Journal of Neurochemistry

Acidification of the Golgi apparatus is indispensable for maturation but not for cell surface delivery of Ret.

Publication Date: 2010 Aug 25 PMID: 20796177
Authors: Hirata, Y. - Shimokawa, N. - Oh-Hashi, K. - Yu, Z. X. - Kiuchi, K.
Journal: J Neurochem

Abstract We examined the effect of concanamycin A and bafilomycin A1, inhibitors of the vacuolar proton-ATPase, on maturation and expression of Ret, a tyrosine kinase receptor for glial cell line-derived neurotrophic factor. Ret appeared as 150- and 170-kDa bands on SDS-PAGE gels and both forms were sensitive to peptide-N-glycosidase F. Western and immunocytochemical analyses revealed that the 150-kDa immature form of Ret accumulated in the Golgi apparatus upon treatment with vacuolar proton-ATPase inhibitors, whereas, the 170-kDa mature form of Ret was dramatically decreased. The result suggests that glycosylation of Ret during the conversion from immature forms to mature forms is pH sensitive, and is likely initiated in the acidic trans-Golgi apparatus. In contrast, glycosylation of nascent receptors to become immature receptors appeared to be pH insensitive, and are likely to take place in the endoplasmic reticulum. The immature form of Ret was present in the plasma membrane when the cells were treated with the vacuolar proton-ATPase inhibitors. In conclusion, the acidification of the Golgi apparatus is crucial for maturation of Ret but not indispensable for trafficking of receptors to the membrane.

post to: CiteULike

Quantitative analysis of the heteromeric neuronal nicotinic receptors in the rat hippocampus.

Publication Date: 2010 Aug 25 PMID: 20796176
Authors: Lomazzo, E. - Macarthur, L. - Yasuda, R. P. - Wolfe, B. B. - Kellar, K. J.
Journal: J Neurochem

Abstract The objective of this study was to identify and quantify the heteromeric neuronal nicotinic receptors (nAChRs) in the rat hippocampus. The density of nAChR subtypes was assessed by labeling them with [(3)H]epibatidine followed by immunoprecipitation with subunit-selective antibodies. Sequential immunoprecipitation assays were used to establish associations between two different subunits, which then allowed the full subunit composition of the receptors to be deduced. Our results show that most of the hippocampal heteromeric nAChRs contain alpha4 and beta2 subunits. In fact, we identified two populations containing these two predominant subunits, the alpha4beta2 and alpha4beta2alpha5 subtypes which account for approximately 40% and approximately 35%, respectively, of the total [(3)H]epibatidine-labeled receptors. An additional heteromeric subtype with the subunit composition of alpha4beta2alpha3 represented approximately 10% of the total nAChRs, and another 10% of the immunoprecipitated receptors contained alpha4 and beta4 subunits, with or without the alpha3 subunit. To determine if alpha4beta2 and alpha4beta2alpha5 nAChR subtypes differ in their ligand binding affinities, the alpha3- and beta4-containing receptors were first removed by immunoprecipitation and then, competition studies with acetylcholine, nicotine, cytisine and sazetidine-A against [(3)H]epibatidine were carried out on the remaining alpha4beta2 and alpha4beta2alpha5 subtypes. Results suggested these subtypes have comparable binding affinities for the nicotinic ligands used here.

post to: CiteULike

Hyperdopaminergic tone in HIV-1 protein treated rats and cocaine sensitization.

Publication Date: 2010 Aug 25 PMID: 20796175
Authors: Ferris, M. J. - Frederick-Duus, D. - Fadel, J. - Mactutus, C. F. - Booze, R. M.
Journal: J Neurochem

Abstract In the United States, one-third of infected individuals contracted Human Immunodeficiency Virus-1 (HIV-1) via injecting drugs with contaminated needles or through risky behaviors associated with drug use. Research demonstrates concomitant administration of psychostimulants and HIV-1-proteins damage neurons to a greater extent than viral proteins or the drug alone. To model the onset of HIV-1-infection in relation to a history of drug use, the current research compared behavior and extracellular dopamine and metabolite levels following Tat(1-86) infusions in animals with and without a history of cocaine experience (10 mg/kg; i.p.; 1 injection / day X 9 days). Animals receiving a behaviorally sensitizing regimen of cocaine demonstrated a decrease in extracellular dopamine concentration in the nucleus accumbens, consistent with evidence describing upregulation of dopamine transporter uptake. Contrary to this effect, Tat(1-86) microinfusion into the nucleus accumbens following the sensitizing regimen of cocaine caused a significant increase in extracellular dopamine levels (nM) within 48 hours with no difference in percent of baseline response to cocaine. After 72 hours, Tat+cocaine treated animals demonstrated a blunted effect on potassium-stimulated extracellular dopamine release (percent of baseline) with a corresponding decrease in expression of behavioral sensitization to cocaine challenge. A persistent decrease in extracellular dopamine metabolite levels was found across all time-points in Tat-treated animals, regardless of experience with cocaine. The current study provides evidence for divergent neurochemical and behavioral outcomes following Tat-treatment; contingent upon experience with cocaine.

post to: CiteULike

Therapeutic evaluation of etanercept in a model of traumatic brain injury.

Publication Date: 2010 Aug 25 PMID: 20796174
Authors: Chio, C. C. - Lin, J. W. - Chang, M. W. - Wang, C. C. - Yang, C. Z. - Chang, C. P.
Journal: J Neurochem

Abstract Antagonism of tumor necrosis factor-alpha (TNF-alpha) with etanercept has proved to be effective in the treatment of spinal cord injury and centrally endotoxin-induced brain injury. However, etanercept may offer promise as therapy for traumatic brain injury (TBI). In this study, anesthetized rats, immediately after the onset of TBI, were divided into two major groups and given the vehicle solution (1 mL/kg of body weight) or etanercept (5 mg/kg of body weight) intraperitoneally once per 12 hours for consecutive 3 days. Etanercept caused attenuation of TBI-induced cerebral ischemia (e.g., increased cellular levels of glutamate and lactate-to-pyruvate ratio), damage (e.g., increased cellular levels of glycerol) and contusion and motor and cognitive function deficits. TBI-induced neuronal apoptosis (e.g., increased numbers of terminal deoxynucleotidyl transferase alphaUTP nick-end labeling and neuronal-specific nuclear protein double-positive cells), glial apoptosis (e.g., increased numbers of terminal deoxynucleotidyl transferase alphaUTP nick-end labeling and glial fibrillary acidic protein double-positive cells), astrocytic (e.g., incrased numbers of glial fibrillary acidic protein positive cells), and microglial (e.g., increased numbers of Iba1-positive cells) activation and activated inflammation (e.g., increased levels of TNF-alpha, interleukin-1beta, and interleukin-6) were all significantly reduced by etanercept treatment. These findings suggest that etanercept may improve outcomes of TBI by penetrating into the cerebrospinal fluid in rats.

post to: CiteULike

Subcellular Rearrangement of Hsp90-binding Immunophilins Accompanies Neuronal Differentiation and Neurite Outgrowth.

Publication Date: 2010 Aug 25 PMID: 20796173
Authors: Ramiro Quinta, H. - Maschi, D. - Gomez-Sanchez, C. - Piwien-Pilipuk, G. - Galigniana, M. D.
Journal: J Neurochem

Abstract FKBP51 and FKBP52 are TPR-domain immunophilins belonging to the TPR-protein*hsp90*hsp70*p23 heterocomplex bound to steroid receptors. Immunophilins are related to receptor folding, subcellular localization, and hormone-dependent transcription. Also, they bind the immunosuppressant macrolide FK506, which shows neuroregenerative and neuroprotective actions by a still unknown mechanism. In this study, we demonstrate that in both, undifferentiated neuroblastoma cells and embryonic hippocampal neurons, the FKBP52*hsp90*p23 heterocomplex concentrates in a perinuclear structure. Upon cell stimulation with FK506, this structure disassembles and this perinuclear area becomes transcriptionally active. The acquisition of a neuronal phenotype is accompanied by increased expression of betaIII-tubulin, Map2, Tau-1, but also hsp90, hsp70, p23, and FKBP52. During the early differentiation steps, the perinuclear heterocomplex redistributes along the cytoplasm and nascent neurites, p23 binds to intermediate filaments and microtubules acquired higher filamentary organization. While FKBP52 moves towards neurites and concentrates in arborization bodies and terminal axons, FKBP51, whose expression remains constant, replaces FKBP52 in the perinuclear structure. Importantly, neurite outgrowth is favored by FKBP52 overexpression or FKBP51 knock-down, and is impaired by FKBP52 knock-down or FKBP51 overexpression, indicating that the balance between these FK506-binding proteins plays a key role during the early mechanism of neuronal differentiation.

post to: CiteULike

The E3-ubiquitin Ligase TRIM2 regulates Neuronal Polarization.

Publication Date: 2010 Aug 25 PMID: 20796172
Authors: Khazaei, M. R. - Bunk, E. C. - Hillje, A. L. - Jahn, H. M. - Riegler, E. M. - Knoblich, J. A. - Young, P. - Schwamborn, J. C.
Journal: J Neurochem

Abstract The establishment of a polarized morphology with a single axon and multiple dendrites is an essential step during neuronal differentiation. This cellular polarization is largely depending on changes in the dynamics of the neuronal cytoskeleton. Here, we show that the TRIM-NHL protein TRIM2 is regulating axon specification in cultured mouse hippocampal neurons, where one of several initially indistinguishable neurites is selected to become the axon. Suppression of TRIM2 by RNA interference results in the loss of neuronal polarity while overexpression of TRIM2 induces the specification of multiple axons. TRIM2 conducts its function during neuronal polarization by ubiquitination of the neurofilament light chain. Together, our results imply an important function of TRIM2 for axon outgrowth during development.

post to: CiteULike

Circadian alteration in neurobiology during protracted opiate withdrawal in rats.

Publication Date: 2010 Aug 5 PMID: 20738730
Authors: Li, S. X. - Liu, L. J. - Jiang, W. G. - Sun, L. L. - Zhou, S. J. - Le Foll, B. - Zhang, X. Y. - Kosten, T. R. - Lu, L.
Journal: J Neurochem

Abstract Protracted opiate withdrawal can extend for months of disrupted hormonal circadian rhythms. We examined rodent behaviors and these circadian disturbances in hormone and peptide levels as well as brain clock gene expression during 60 days of protracted withdrawal. Our behavioral tests included open field, elevated plus maze and sucrose preference tests at 36 hours, 10, 30 and 60 days after stopping chronic morphine. At these four assessment points we collected samples every 4 hours for 24 hours to examine circadian rhythms in blood hormone and peptide levels and brain expression of rPER1, rPER2 and rPER3 clock genes. Decreased locomotor activity and elevated ACTH and melatonin levels persisted for two months after morphine withdrawal, but corticosterone was elevated only at 36h and 10 days after withdrawal. Orexin levels were high at 36h after withdrawal, but then reversed during protracted withdrawal to abnormally low levels. Peakbeta- EP levels showed no differences from normal. However, circadian rhythms were blunted for all of these hormones. Corticosterone, ACTH, and orexin blunting persisted at least for 60 days. The blunted circadian rhythm ofbeta- EP and melatonin recovered by day 60, but the peak phase of beta- EP was delayed about 8 hours. Blunted circadian rhythms and reduced expression of rPER1, rPER2 and rPER3 persisted at least for 60 days in the SCN, PFC, NAc core, CeA, Hippocampus and VTA. Circadian rhythms of rPER1 in the NAc shell and BLA and of rPER2 in the CeA were reversed. Disrupted circadian rhythms of rPER1, rPER 2 and rPER3 expression in reward-related brain circuits and blunted circadian rhythms in peripheral hormones and peptides may play a role in protracted opiate withdrawal and contribute to relapse.

post to: CiteULike

Functional and immunocytochemical characterization of the creatine transporter in rat hippocampal neurons.

Publication Date: 2010 Aug 20 PMID: 20731764
Authors: Dodd, J. R. - Birch, N. P. - Waldvogel, H. J. - Christie, D. L.
Journal: J Neurochem

Abstract Creatine uptake by neurons requires a specific creatine transporter (CRT). The purpose of the present work was to investigate the activity and localization of the CRT in primary cultures of hippocampal neurons obtained from 18-day rat embryos. Creatine uptake increased as the neurons differentiated in culture. Immunofluorescence microscopy showed most of the CRT was associated with dendrites, although some CRT was present in axons and axon terminals. Neurons contained high levels of Na(+)-dependent creatine transport activity (K(m) =45.5 muM; V(max), 1719 pmole creatine/ min/ mg protein) which was inhibited by competitive inhibitors of the CRT. The IC(50) for guanidinoacetate, a precursor of creatine, was 712 muM approximately 15 fold higher than the K(m) for creatine. Incubation of neurons with 1 mM creatine resulted in the accumulation of high levels of creatine which affected the V(max) but not the K(m) for creatine transport. The rate of creatine release from neurons increased in the absence of Na(+) showing the importance of the electrochemical gradient for creatine retention. This is the first detailed study of the CRT in neurons and identifies primary cultures of rat hippocampal neurons as a good model for future studies of the CRT in relation to the effects of creatine on neuronal function and viability.

post to: CiteULike

Experimental models of vascular dementia and vascular cognitive impairment. A systematic review.

Publication Date: 2010 Aug 20 PMID: 20731763
Authors: Jiwa, N. S. - Garrard, P. - Hainsworth, A. H.
Journal: J Neurochem

Abstract Vascular cognitive impairment (VCI) encompasses vascular dementia and is the second most common cause of dementing illness after Alzheimer disease. The main causes of VCI are: cerebral small vessel disease; multi-infarct dementia; strategic infarct (i.e. located in a functionally-critical brain area); haemorrhage/microbleed; angiopathy (including cerebral amyloid angiopathy); severe hypoperfusion (e.g. cardiac arrhythmia); and hereditary vasculopathy (e.g. CADASIL). In this systematic analysis we aimed to relate cognitive and neuropathological features of experimental models to clinical VCI. We extracted data from 107 studies covering 16 models. These included: brief global ischaemic insults (in rats, mice or gerbils); chronic global hypoperfusion (rats, mice, gerbils); chronic hypertension (in primates or stroke-prone, spontaneously-hypertensive rats); multiple ischaemic lesions due to intra-vascular emboli (in rodents, rabbits or primates); strategic ischaemic lesions (in rats or mini-pigs); generalised vasculopathies, due to mutant Notch3, hyperhomocysteinaemia, experimental diabetes mellitus or lack of cerebral vasodilator M(5) receptors (rats or mice). Most cognitive testing showed deficits in working and reference memory. The lesions observed were microinfarcts, diffuse white matter lesions, hippocampal neuronal death, focal ischaemic lesions and micro-haemorrhages. The most-used model was bilateral carotid artery occlusion in rats, leading to white matter injury due to chronic hypoperfusion.

post to: CiteULike

PRESYNAPTIC CALCIUM CHANNELS AND alpha3-INTEGRINS ARE COMPLEXED WITH SYNAPTIC CLEFT LAMININS, CYTOSKELETAL ELEMENTS AND ACTIVE ZONE COMPONENTS.

Publication Date: 2010 Aug 21 PMID: 20731762
Authors: Carlson, S. S. - Valdez, G. - Sanes, J. R.
Journal: J Neurochem

At chemical synapses, synaptic cleft components interact with elements of the nerve terminal membrane to promote differentiation and regulate function. Laminins containing the beta2 subunit are key cleft components, and they act in part by binding the pore-forming subunit of a presynaptic voltage-gated calcium channel (Ca(v)alpha) (Nishimune, et al., 2004). Here, we identify Ca(v)alpha-associated intracellular proteins that may couple channel-anchoring to assembly or stabilization of neurotransmitter release sites called active zones. Using Ca(v)alpha-antibodies, we isolated a protein complex from Torpedo electric organ synapses, which resemble neuromuscular junctions but are easier to isolate in bulk. We identified 10 components of the complex: six cytoskeletal proteins (alpha2/beta2 spectrins, plectin 1, AHNAK/desmoyokin, dystrophin, and myosin 1), two active zone components (bassoon and piccolo), synaptic laminin, and a calcium channel beta subunit. Immunocytochemistry confirmed these proteins in electric organ synapses, and PCR analysis revealed their expression by developing mammalian motor neurons. Finally, we show that synaptic laminins also interact with presynaptic integrins containing the alpha3 subunit. Together with our previous finding that a distinct synaptic laminin interacts with SV2 on nerve terminals (Son, et al., 2000), our results identify three paths by which synaptic cleft laminins can send developmentally important signals to nerve terminals.

post to: CiteULike

Bex1 is involved in the regeneration of axons after injury.

Publication Date: 2010 Aug 21 PMID: 20731761
Authors: Khazaei, M. R. - Halfter, H. - Karimzadeh, F. - Koo, J. H. - Margolis, F. L. - Young, P.
Journal: J Neurochem

Abstract Successful axonal regeneration is a complex process determined by both axonal environment and endogenous neural capability of the regenerating axons in the central and the peripheral nervous systems. Numerous external inhibitory factors inhibit axonal regeneration after injury. In response, neurons express various regeneration-associated genes to overcome this inhibition and increase the intrinsic growth capacity. In the present study we show that the brain expressed X-linked (Bex1) protein was over-expressed as a result of peripheral axonal damage. Bex1 antagonized the axon outgrowth inhibitory effect of myelin-associated glycoprotein (MAG). The involvement of Bex1 in axon regeneration was further confirmed in vivo. We have demonstrated that Bex1 knock-out mice showed lower capability for regeneration after peripheral nerve injury than wild-type animals. Wild type mice could recover from sciatic nerve injury much faster than Bex1 knock-out mice. Our findings suggest that Bex1 could be considered as regeneration associated gene.

post to: CiteULike

INCREASED CASPASE ACTIVATION AND DECREASED TDP-43 SOLUBILITY IN PROGRANULIN KNOCKOUT CORTICAL CULTURES.

Publication Date: 2010 Aug 21 PMID: 20731760
Authors: Kleinberger, G. - Wils, H. - Ponsaerts, P. - Joris, G. - Timmermans, J. P. - Van Broeckhoven, C. - Kumar-Singh, S.
Journal: J Neurochem

ABSTRACT Null mutations in progranulin (GRN) are associated with frontotemporal lobar degeneration characterized by intraneuronal accumulation of TAR DNA-binding protein-43 (TDP-43). However, the mechanism by which GRN-deficiency leads to neurodegeneration remains largely unknown. In primary cortical neurons derived from Grn knockout (Grn(-/-)) mice, we found that Grn-deficiency causes significantly reduced neuronal survival and increased caspase-mediated apoptosis, which was not observed in primary mouse embryonic fibroblasts (MEFs) derived from Grn(-/-) mice. Also, neurons derived from Grn(-/-) mice showed an increased amount of phosphorylated TDP-43 accumulations. Furthermore, proteasomal inhibition with MG132 caused increased caspase-mediated TDP-43 fragmentation and accumulation of detergent-insoluble 35- and 25-kDa C-terminal fragments (CTFs) in Grn(-/-) neurons and MEFs. Interestingly, full-length TDP-43 also accumulated in the detergent-insoluble fraction, and caspase-inhibition prevented MG132-induced generation of TDP-43 CTFs but did not block the pathological conversion of full-length TDP-43 from soluble to insoluble species. These data suggest that GRN functions as a survival factor for cortical neurons and GRN-deficiency causes increased susceptibility to cellular stress. This leads to increased aggregation and accumulation of full-length TDP-43 along with its C-terminal derivatives by both caspase-dependent and independent mechanisms.

post to: CiteULike

Alpha-synuclein expression is induced by depolarization and cyclic AMP in enteric neurons.

Publication Date: 2010 Aug 21 PMID: 20731759
Authors: Paillusson, S. - Tasselli, M. - Lebouvier, T. - Mahe, M. - Chevalier, J. - Biraud, M. - Cario-Toumaniantz, C. - Neunlist, M. - Derkinderen, P.
Journal: J Neurochem

Abstract Accumulated evidence emphasizes the importance of alpha-synuclein expression levels in Parkinson's disease (PD) pathogenesis. PD is a multicentric disorder that affects the enteric nervous system (ENS), whose involvement may herald the degenerative process in the central nervous system. We therefore undertook the present study to investigate the mechanisms involved in the regulation of expression of alpha-synuclein in the ENS. The regulation of alpha-synuclein expression was assessed by qPCR and Western blot analysis in rat primary culture of ENS treated with KCl and forskolin. A pharmacological approach was used to decipher the signaling pathways involved. Intraperitoneal injections of Bay K-8644 and forskolin were performed in mice, whose proximal colons were further analyzed for alpha-synuclein expression. Depolarization and forskolin increased alpha-synuclein mRNA and protein expression in primary cultures of ENS, though L-type calcium channel and protein kinase A, respectively. Both stimuli increased alpha-synuclein expression though a Ras/extracellular-signal regulated kinases pathway. An increase in alpha-synuclein expression was also observed in vivo in the ENS of mice injected with Bay K-8644 or forskolin. In conclusion, we have identified stimuli leading to alpha-synuclein overexpression in the ENS, which could be critical in the initiation of the pathological process in PD.

post to: CiteULike

GFR alpha-1 receptor expression in the aging nigrostriatal and mesoaccumbens pathways.

Publication Date: 2010 Aug 21 PMID: 20731758
Authors: Pruett, B. S. - Salvatore, M. F.
Journal: J Neurochem

Abstract We recently reported that age-related bradykinesia was associated with reduced DA tissue content, ser31 tyrosine hydroxylase (TH) phosphorylation, and total TH levels in substantia nigra (SN) only. Here, we propose that these decreases result from reduced GDNF family receptor alpha-1 (GFR alpha-1) levels in the aged (30 month-old) cohort of rats. Analysis of GFR alpha-1 receptor protein in SN, striatum, ventral tegmental area (VTA), and nucleus accumbens (NAc) from 12- and 30-month old Brown-Norway/Fischer 344 F(1) hybrid rats revealed immunoreactivity at approximately 48 and 52 kDa, bands previously characterized to correspond to soluble and GPI-linked forms of GFR alpha-1, respectively. The nigrostriatal pathway had significantly greater levels of the soluble GFR alpha-1 than the mesoaccumbens pathway. Aging significantly reduced soluble and total GFR alpha-1 in the SN. The levels of GFR alpha-1 significantly correlated with TH protein in SN, striatum, and NAc, but only in the SN did GFR alpha-1 significantly correlate with DA levels. Based on these observations and findings from the literature, we speculate that 1) GFR alpha-1 receptor expression may regulate nigral DA bioavailability in vivo, 2) age-related decreases in soluble GFR alpha-1 in SN may contribute to bradykinesia in aging, and 3) differences in expression of the GFR alpha-1 forms between the nigrostriatal and mesoaccumbens pathways and allied tissue may indicate that GDNF-signaling differs between these DA pathways.

post to: CiteULike

Cerebellar Lipid Differences between R6/1 Transgenic Mice and Humans with Huntington's Disease.

Publication Date: 2010 Aug 21 PMID: 20731757
Authors: Denny, C. A. - Desplats, P. A. - Thomas, E. A. - Seyfried, T. N.
Journal: J Neurochem

Abstract Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, psychiatric, and cognitive abnormalities. In this present study, we tested whether abnormal motor behavior in a mouse model of HD, the R6/1 Tg mice, was associated with changes in cerebellar lipid composition and gene expression. We report altered motor behavior, which was associated with abnormal expression of glycosyltransferase genes in the cerebellum of R6/1 Tg mice. Cerebellar wet weight and total ganglioside concentration was significantly lower in R6/1 Tg mice than in wild-type (Wt) mice. Furthermore, the Purkinje cell-enriched ganglioside LD1 and the granule cell-enriched ganglioside GD1a were significantly lower in R6/1 Tg mice than in Wt mice. The myelin-enriched lipid sulfatides was also reduced in the cerebellum of R6/1 Tg mice. In contrast to the R6/1 Tg mice, total cerebellar ganglioside concentration did not differ between HD and control subjects. However, expression of several cerebellar glycosyltransferases genes was significantly less in HD subjects than in control subjects. Our findings indicate that the R6/1 Tg mice have severe cerebellar glycosphingolipid (GSL) abnormalities that may account, in part, for their abnormal motor behavior. While the cerebellar lipid abnormalities found in the R6/1 Tg mice were not found in these HD subjects, the R6/1 Tg mice may be useful for evaluating the role of GSLs in cerebellar development.

post to: CiteULike

3beta-HSD in Songbird Brain: Subcellular Localization and Rapid Regulation by Estradiol.

Publication Date: 2010 Aug 14 PMID: 20722973
Authors: Pradhan, D. S. - Lau, L. Y. - Schmidt, K. L. - Soma, K. K.
Journal: J Neurochem

Abstract The enzyme 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD) catalyzes the conversion of dehydroepiandrosterone (DHEA) to androstenedione (AE), thereby playing a key role in sex steroid synthesis. In peripheral tissues, 3beta-HSD is membrane-bound, present in both mitochondria and microsomes, and is regulated differentially in these two subcellular compartments. In the brain, 3beta-HSD is present, but its subcellular compartmentalization is unknown. Here, in Study 1, we examined the subcellular localization of 3beta-HSD in the brain of a songbird, the zebra finch. In Study 2, in males and females, we determined whether 3beta-HSD activity in different subcellular compartments is rapidly regulated by in vitro treatment with estradiol (E(2)), which has many rapid effects on the brain. Brain 3beta-HSD was enriched primarily in microsomes and secondarily in mitochondria and synaptosomes. In both males and females, E(2) treatment rapidly (within 5 min) inhibited 3beta-HSD activity in both mitochondria/synaptosomes and microsomes, with greater inhibition in microsomes. We also assessed the activity of 5beta-reductase, which acts on AE. E(2) rapidly inhibited 5beta-reductase activity in microsomes only. This is the first study to examine the subcellular localization of 3beta-HSD in the brain, and the data demonstrate the importance of subcellular localization for the regulation of steroidogenic enzymes in the brain.

post to: CiteULike

Microglial activation mediates de novo lysophosphatidic acid production in a model of neuropathic pain.

Publication Date: 2010 Aug 14 PMID: 20722972
Authors: Ma, L. - Nagai, J. - Ueda, H.
Journal: J Neurochem

Abstract We recently demonstrated that de novo lysophosphatidic acid (LPA) production in the spinal cord occurs in the early phase after nerve injury or LPA injection, and underlies the peripheral mechanisms of neuropathic pain. In this study, we examined the possible involvement of spinal cord microglia in such LPA-mediated functions. Intrathecal LPA injection rapidly increased the gene expression of CD11b and protein expression of phosphor-p38, accompanied by a morphological change of microglia from a ramified to amoeboid shape. Although early treatment with minocycline significantly inhibited LPA-induced neuropathic pain-like behavior and microglial activation, late treatment did not. Early treatment with minocycline also blocked LPA-evoked de novo LPA production and the increased activation of cytosolic phospholipase A(2), an LPA synthesis-related enzyme. Similar results were observed when the sciatic nerve was partially injured: early, but not late, treatment with minocycline significantly inhibited the injury-induced neuropathic pain, microglial activation, de novo LPA production and the underlying increased activation of cytosolic phospholipase A(2) as well as calcium-independent phospholipase A(2), another LPA synthesis-related enzyme. These findings suggest that the early phase of microglial activation is involved in de novo LPA production, and that this underlies the initial mechanisms of nerve injury-induced neuropathic pain.

post to: CiteULike

Light touch induces ERK activation in superficial dorsal horn neurons after inflammation: involvement of spinal astrocytes and JNK signaling in touch-evoked central sensitization and mechanical allodynia.

Publication Date: 2010 Aug 12 PMID: 20722971
Authors: Gao, Y. J. - Ji, R. R.
Journal: J Neurochem

Abstract Activation of extracellular signal-regulated kinase (ERK) in spinal cord neurons could serve as a marker for sensitization of dorsal horn neurons in persistent pain. ERK is normally activated by high-threshold noxious stimuli. We investigated how low-threshold mechanical stimuli could activate ERK after complete Freund's adjuvant (CFA)-induced inflammation. Unilateral injection of CFA induced ipsilateral heat hyperalgesia and bilateral mechanical allodynia. CFA-induced ERK activation in ipsilateral dorsal horn neurons declined after 2 days. Interestingly, low threshold mechanical stimulation given by light touch either on the inflamed paw or the contralateral non-inflamed paw dramatically increased ERK phosphorylation (pERK) in the dorsal horn ipsilateral to touch stimulation. Notably, light touch induced pERK mainly in superficial neurons in laminae I-IIo. Intrathecal administration of the astroglial toxin L-alpha-aminoadipate (L-alpha-AA) on post-CFA day 2 reversed CFA-induced bilateral mechanical allodynia but not heat hyperalgesia. Furthermore, L-alpha-AA, the glial inhibitor fluorocitrate, and a peptide inhibitor of c-Jun N-terminal Kinase (JNK) all reduced light touch-evoked ERK activation ipsilateral to touch. Collectively, these data suggest that (a) ERK can be activated in superficial dorsal horn neurons by low threshold mechanical stimulation under pathological condition and (b) ERK activation by light touch is associated with mechanical allodynia and requires an astrocyte network.

post to: CiteULike

Neuropeptide S stimulates dopaminergic neurotransmission in the medial prefrontal cortex.

Publication Date: 2010 Aug 30 PMID: 20722970
Authors: Si, W. - Aluisio, L. - Okamura, N. - Clark, S. D. - Fraser, I. - Sutton, S. W. - Bonaventure, P. - Reinscheid, R. K.
Journal: J Neurochem

J. Neurochem. (2010) 10.1111/j.1471-4159.2010.06947.x Abstract Neuropeptide S (NPS) is known to produce anxiolytic-like effects and facilitate extinction of conditioned fear. Catecholaminergic neurotransmission in the medial prefrontal cortex (mPFC) has been suggested to be crucially involved in these brain functions. In the current study, we investigated the effect of NPS on the release of dopamine and serotonin in the mPFC by in vivo microdialysis in rats. Central administration of NPS dose-dependently enhanced extracellular levels of dopamine and its major metabolite 3,4-dihydroxyphenylacetic acid, with maximal effects lasting up to 120 min. In contrast, no effect on serotonergic neurotransmission was detected. Dopamine release in the mPFC has been previously linked to modulation of anxiety states and fear extinction. The present results may thus provide a physiological and anatomical basis for the reported effects of NPS on these behaviors.

post to: CiteULike

Chronic exposure to nicotine and saquinavir decreases endothelial Notch-4 expression and disrupts blood-brain barrier integrity.

Publication Date: 2010 Aug 30 PMID: 20722969
Authors: Manda, V. K. - Mittapalli, R. K. - Geldenhuys, W. J. - Lockman, P. R.
Journal: J Neurochem

J. Neurochem. (2010) 10.1111/j.1471-4159.2010.06948.x Abstract Since the advent of HAART, there have been substantial improvements in HIV patient survival; however, the prevalence of HIV associated dementia has increased. Importantly, HIV positive individuals who smoke progress to HIV associated neurological conditions faster than those who do not. Recent in vitro data have shown that pharmacological levels of saquinavir causes endothelial oxidative stress and significantly decreases Notch-4 expression, a primary protein involved in maintaining stability of blood-brain barrier (BBB) endothelium. This is concerning as nicotine can also generate reactive oxygen species in endothelium. It is largely unknown if pharmacological doses of these drugs can cause a similar in vivo down-regulation of Notch-4 and if there is a concurrent destabilization of the integrity of the BBB. The data herein show: (i) nicotine and protease inhibitors cause an additive oxidative stress burden in endothelium; (ii) that the integrity of the BBB is disrupted after concurrent chronic nicotine and protease inhibitor administration; and (iii) that BBB endothelial dysfunction is correlated with a decrease in Notch-4 and ZO-1 expression. Considering the high prevalence of smoking in the HIV infected population (3- to 4-fold higher than in the general population) this data must be followed up to determine if all protease inhibitors cause a similar BBB disruption or if there is a safer alternative. In addition, this data may suggest that the induced BBB disruption may allow foreign molecules to gain access to brain and be a contributing factor to the slow progression of HIV associated dementia.

post to: CiteULike

The Role of Endogenous Serotonin in Methamphetamine-Induced Neurotoxicity to Dopamine Nerve Endings of the Striatum.

Publication Date: 2010 Aug 12 PMID: 20722968
Authors: Thomas, D. M. - Perez, M. A. - Francescutti-Verbeem, D. M. - Shah, M. M. - Kuhn, D. M.
Journal: J Neurochem

Abstract Methamphetamine (METH) is a neurotoxic drug of abuse that damages the dopamine (DA) neuronal system in a highly delimited manner. The brain structure most affected by METH is the striatum where long-term DA depletion and microglial activation are maximal. Endogenous DA has been implicated as a critical participant in METH-induced neurotoxicity, most likely as a substrate for non-enzymatic oxidation by METH-generated reactive oxygen species (ROS). The striatum is also extensively innervated by serotonin (5HT) nerve endings and this neurochemical system is modified by METH in much the same manner as seen in DA nerve endings (i.e., increased release of 5HT, loss of function in tryptophan hydroxylase and the serotonin transporter, long-term depletion of 5HT stores). 5HT can also be modified by ROS to form highly reactive species that damage neurons but its role in METH neurotoxicity has not been assessed. Increases in 5HT levels with 5HTP do not change METH-induced neurotoxicity to the DA nerve endings as revealed by reductions in DA, tyrosine hydroxylase and dopamine transporter levels. Partial reductions in 5HT with p-chlorophenylalanine (PCPA) are without effect on METH toxicity, despite the fact that PCPA largely prevents METH-induced hyperthermia. Mice lacking the gene for brain tryptophan hydroxylase 2 are devoid of brain 5HT and respond to METH in the same manner as wild-type controls, despite showing enhanced drug-induced hyperthermia. Taken together, the present results indicate that endogenous 5HT does not appear to play a role in METH-induced damage to DA nerve endings of the striatum.

post to: CiteULike

Critical role of lipid rafts in virus entry and activation of Phosphoinositide 3' Kinase / Akt signaling during early stages of Japanese Encephalitis Virus infection in neural stem/progenitor cells.

Publication Date: 2010 Aug 12 PMID: 20722967
Authors: Das, S. - Chakraborty, S. - Basu, A.
Journal: J Neurochem

Abstract Japanese encephalitis virus (JEV), the leading cause of acute encephalitis in South-East Asia is a neurotropic virus infecting various CNS cell types. Most Flaviviruses including JEV get internalised into cells by receptor-mediated endocytosis, which involve clathrin and membrane cholesterol. The cholesterol-enriched membrane microdomains referred to as lipid rafts act as portals for virus entry in a number of enveloped viruses, including Flavivirus. However, the precise role played by membrane lipid rafts in JEV internalisation into neural stem cells is still unknown. We have established neural stem/progenitor cells and C17.2 cell line as models of productive JEV infection. Increase in membrane fluidity and clustering of viral envelope proteins in lipid rafts was observed in early time points of infection. Localisation of non-structural proteins to rafts at later infection stages was also observed. Co-localisation of JEV glycoprotein with Cholera toxin B confirmed that JEV internalisation occurs in a lipid-raft dependent manner. Though JEV entry is raft dependent, however, there is requirement of functional clathrin during endocytosis inside the cells. Besides virus entry, the lipid rafts act as signalling platforms for Src tyrosine kinases and result in activation of PI3K/Akt signalling during early JEV infection. Disruption of lipid raft formation by cholesterol depletion using Methyl beta-cyclodextrin, reduced JEV RNA levels and production of infectious virus particles as well as impaired PI3K/Akt signalling during initial infection. Overall, our results implicate the importance of host membrane lipid rafts in JEV entry and life cycle, besides maintaining survival of neural stem/progenitor cells during early infection.

post to: CiteULike

Inhibition of CCAAT/enhancer binding protein delta expression by chrysin in microglial cells results in anti-inflammatory and neuroprotective effects.

Publication Date: 2010 Aug 30 PMID: 20722966
Authors: Gresa-Arribas, N. - Serratosa, J. - Saura, J. - Sola, C.
Journal: J Neurochem

J. Neurochem. (2010) 10.1111/j.1471-4159.2010.06952.x Abstract The control of neuroinflammation is a potential target to be considered in the treatment of neurodegenerative diseases. It is therefore important to find anti-inflammatory drugs and study new targets that inhibit neuroinflammation. We designed an experimental model of neuroinflammation in vitro to study the anti-inflammatory and neuroprotective effects of the flavonoid chrysin and the involvement of nuclear factor-kappaB p65 and CCAAT/enhancer binding proteins (C/EBPs) beta and delta transcription factors in its mechanism of action. We used primary cultures of mouse embryonic cortical neurons and cultures of BV2 (murine microglial cell line) or mouse primary microglia. We induced neuronal death in neuronal-BV2/microglial co-cultures using lipopolysaccharide of Escherichia coli and interferon-gamma. Chrysin pre-treatment inhibited nitric oxide and tumor necrosis factor-alpha production, as well as inducible nitric oxide synthase expression in lipopolysaccharide E. coli and interferon-gamma-treated microglial cells, but did not affect cyclooxygenase-2 expression. Chrysin pre-treatment also protected neurons against the neurotoxicity induced by reactive microglial cells. These effects were associated to a decrease in C/EBPdelta protein level, mRNA expression, and DNA-binding activity, with no effect on C/EBPbeta and p65 nuclear protein levels or DNA-binding activity, pointing out C/EBPdelta as a possible mediator of chrysin effects. Consequently, C/EBPdelta is a possible target to act against neuroinflammation in neurodegenerative processes.

post to: CiteULike

Unique clockwork in photoreceptor of rat.

Publication Date: 2010 Aug 12 PMID: 20722965
Authors: Schneider, K. - Tippmann, S. - Spiwoks-Becker, I. - Holthues, H. - Wolloscheck, T. - Spatkowski, G. - Engel, L. - Frederiksen, U. - Spessert, R.
Journal: J Neurochem

Abstract In mammals, the retina contains a clock system that oscillates independently of the master clock in the suprachiasmatic nucleus and allows the retina to anticipate and to adapt to the sustained daily changes in ambient illumination. Using a combination of laser capture micro-dissection and quantitative polymerase chain reaction in the present study, the clockwork of mammalian photoreceptors has been recorded. The transcript amounts of the core clock genes Clock, Bmal1, Period1, Period3, Cryptochrome2, and Casein kinase Iepsilon in photoreceptors of rat retina have been found to undergo daily changes. Clock and Bmal1 peak with Period1 and Period3 around dark onset, whereas Casein kinase Iepsilon and Cryptochrome2 peak at night. As shown for Clock, Period1, and Casein kinase Iepsilon, the oscillation of transcript amounts results in daily changes of the protein products. The in-phase oscillation of Clock/Bmal1 with Periods and the rhythmic expression of Casein kinase Iepsilon do not occur in molecular clocks of other tissues including the suprachiasmatic nucleus. Therefore, the findings presented suggest that the photoreceptor clock is unique not only in its position outside the clock hierarchy mastered by the suprachiasmatic nucleus, but also with regard to the intrinsic rhythmic properties of its molecular components.

post to: CiteULike

Erratum.

Publication Date: 2010 Aug 5 PMID: 20704638
Authors:
Journal: J Neurochem

post to: CiteULike

The biphasic NAD(P)H fluorescence response of astrocytes to dopamine reflects the metabolic actions of oxidative phosphorylation and glycolysis.

Publication Date: 2010 Aug 4 PMID: 20698931
Authors: Requardt, R. P. - Wilhelm, F. - Rillich, J. - Winkler, U. - Hirrlinger, J.
Journal: J Neurochem

J. Neurochem. (2010) 10.1111/j.1471-4159.2010.06940.x Abstract The NAD(+)/NADH redox pair constitutes an important metabolic node connecting catabolic pathways to energy production. We took advantage of the fluorescence of NADH to monitor changes in NADH levels by 2-photon laser scanning microscopy in cultured cortical astrocytes and acutely isolated brain slices in response to dopamine (DA), a major neurotransmitter involved in modulation of attention, motivation, and learning. DA induced a dose-dependent biphasic response of the NAD(P)H fluorescence signal, consisting of an initial decrease followed by a subsequent increase. This response was mediated by D1-receptors, protein kinase A, and 5'-AMP-activated protein kinase signaling. While the initial decrease could be inhibited by blocking mitochondrial respiratory chain, the increase was inhibited by blocking glycolysis. Finally, activation of DA receptors on astrocytes in acutely isolated mouse cortical brain slices also induced an increase in the NAD(P)H fluorescence signal. We conclude that DA activates two opposing components of astrocytic metabolism with different kinetics. This response of the astroglial metabolism might contribute to fine-tuned participation of astrocytes to neuronal activity and functional states of the brain.

post to: CiteULike

In vitro modeling of perineuronal nets: hyaluronan synthase and link protein are necessary for their formation and integrity.

Publication Date: 2010 Sep 1 PMID: 20584105
Authors: Kwok, J. C. - Carulli, D. - Fawcett, J. W.
Journal: J Neurochem

We have previously shown that all perineuronal nets (PNNs) bearing neurons express a hyaluronan synthase (HAS), a link protein (usually cartilage link protein-1; Crtl1) and a chondroitin sulfate proteoglycan (usually aggrecan). Animal lacking Crtl1 in the CNS lacks normal PNNs. PNNs are implicated in the control of neuronal plasticity, and interventions to modulate PNN formation will be useful for manipulating plasticity. We have developed an in vitro model which demonstrates how the structural components of PNNs trigger their formation, using human embryonic kidney cells, which do not normally produce a pericellular matrix. Expression of HAS3 leads to the production of a diffuse matrix. It was converted into a compact PNN-like structure when the cells also expressed Crtl1 and aggrecan. This matrix was stained by Wisteria floribunda, contained Crtl1 and aggrecan, and like PNNs, could only be solubilized in 6 M urea. In the absence of hyaluronan produced by HAS3, aggrecan and Crtl1 dissipated into the medium, but when the cells were transfected to produce a hyaluronan matrix, Crtl1 and aggrecan were incorporated into it. Cells lacking any one of these molecules showed impaired integrity of the PNNs. Cells expressing HAS3 and Crtl1 were able to incorporate exogenous aggrecan into their pericellular matrix.

post to: CiteULike

Involvement of stathmin 1 in the neurotrophic effects of PACAP in PC12 cells.

Publication Date: 2010 Sep 1 PMID: 20569302
Authors: Dejda, A. - Chan, P. - Seaborn, T. - Coquet, L. - Jouenne, T. - Fournier, A. - Vaudry, H. - Vaudry, D.
Journal: J Neurochem

Rat pheochromocytoma PC12 cells have been widely used to investigate the neurotrophic activities of pituitary adenylate cyclase-activating polypeptide (PACAP). In particular, PACAP has been shown to promote differentiation and to inhibit apoptosis of PC12 cells. In order to identify the mechanisms mediating these effects, we sought for proteins that are phosphorylated upon PACAP treatment. High-performance liquid chromatography and 2D gel electrophoresis analysis, coupled with mass spectrometry, revealed that stathmin 1 is strongly phosphorylated within only 5 min of exposure to PACAP. Western blot experiments confirmed that PACAP induced a robust phosphorylation of stathmin 1 in a time-dependent manner. On the other hand, PACAP decreased stathmin 1 gene expression. Investigations of the signaling mechanisms known to be activated by PACAP revealed that phosphorylation of stathmin 1 was mainly mediated through the protein kinase A and mitogen-activated protein kinase pathways. Blockage of stathmin 1 expression with small interfering RNA did not affect PC12 cell differentiation induced by PACAP but reduced the ability of the peptide to inhibit caspase 3 activity and significantly decreased its neuroprotective action. Taken together, these data demonstrate that stathmin 1 is involved in the neurotrophic effect of PACAP in PC12 cells.

post to: CiteULike

Altered neurotransmission in the mesolimbic reward system of Girk mice.

Publication Date: 2010 Sep 1 PMID: 20557431
Authors: Arora, D. - Haluk, D. M. - Kourrich, S. - Pravetoni, M. - Fernandez-Alacid, L. - Nicolau, J. C. - Lujan, R. - Wickman, K.
Journal: J Neurochem

Mice lacking the Girk2 subunit of G protein-gated inwardly rectifying K+ (Girk) channels exhibit dopamine-dependent hyperactivity and elevated responses to drugs that stimulate dopamine neurotransmission. The dopamine-dependent phenotypes seen in Girk2(-/-) mice could reflect increased intrinsic excitability of or diminished inhibitory feedback to midbrain dopamine neurons, or secondary adaptations triggered by Girk2 ablation. We addressed these possibilities by evaluating Girk(-/-) mice in behavioral, electrophysiological, and cell biological assays centered on the mesolimbic dopamine system. Despite differences in the contribution of Girk1 and Girk2 subunits to Girk signaling in midbrain dopamine neurons, Girk1(-/-) and Girk2(-/-) mice exhibited comparable baseline hyperactivities and enhanced responses to cocaine. Girk ablation also correlated with altered afferent input to dopamine neurons in the ventral tegmental area. Dopamine neurons from Girk1(-/-) and Girk2(-/-) mice exhibited elevated glutamatergic neurotransmission, paralleled by increased synaptic levels of alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate glutamate receptors. In addition, synapse density, alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor levels, and glutamatergic neurotransmission were elevated in medium spiny neurons of the nucleus accumbens from Girk1(-/-) and Girk2(-/-) mice. We conclude that dopamine-dependent phenotypes in Girk2(-/-) mice are not solely attributable to a loss of Girk signaling in dopamine neurons, and likely involve secondary adaptations facilitating glutamatergic signaling in the mesolimbic reward system.

post to: CiteULike

Retailoring docosahexaenoic acid-containing phospholipid species during impaired neurogenesis following omega-3 alpha-linolenic acid deprivation.

Publication Date: 2010 Sep 1 PMID: 20557429
Authors: Brand, A. - Crawford, M. A. - Yavin, E.
Journal: J Neurochem

Diminished levels of docosahexaenoic acid (22:6n-3), the major fatty acid (FA) synthesized from alpha-linolenic acid (18:3n-3), have been implicated in functional impairment in the developing and adult brain. We have now examined the changes in phospholipid (PL) molecular species in the developing postnatal cortex, a region recently shown to be affected by a robust aberration in neuronal cell migration, after maternal diet alpha-linolenic acid deprivation (Yavin et al. (2009)Neuroscience162(4),1011). The frontal cortex PL composition of 1- to 4-week-old rats was analyzed by gas chromatography and electrospray ionization/tandem mass spectrometry. Changes in the cortical PL molecular species profile by dietary means appear very specific as 22:6n-3 was exclusively substituted by docosapentaenoic acid (22:5n-6). However, molecular species were conserved with respect to the combination of specific polar head groups (i.e. ethanolamine and serine) in sn-3 and defined saturated/mono-unsaturated FA in sn-1 position even when the sn-2 FA moiety underwent diet-induced changes. Our results suggest that substitution of docosahexaenoic acid by docosapentaenoic acid is tightly regulated presumably to maintain a proper biophysical characteristic of membrane PL molecular species. The importance of this conservation may underscore the possible biochemical consequences of this substitution in regulating certain functions in the developing brain.

post to: CiteULike

Inflammatory chemokine release of astrocytes in vitro is reduced by all-trans retinoic acid.

Publication Date: 2010 Sep 1 PMID: 20557428
Authors: van Neerven, S. - Regen, T. - Wolf, D. - Nemes, A. - Johann, S. - Beyer, C. - Hanisch, U. K. - Mey, J.
Journal: J Neurochem

The production of chemokines by astrocytes constitutes an important component of neuroinflammatory processes in the brain. As the transcriptional activator retinoic acid (RA), used for chemotherapy and dermatological applications, exerts anti-inflammatory effects on monocytes and lymphocytes, we have tested whether the physiologically occurring isomer, all-trans RA, affects chemokine expression by astrocytes. Under control conditions, primary cultures of murine cortical astrocytes expressed no or very low levels of CCL and CXCL chemokines. After treatment with bacterial lipopolysaccharides to simulate inflammation in vitro, we detected a strong increase in the release of CCL2 (to > 4 ng/mL in cell culture supernatant), CCL3 (> 20 ng/mL), CCL5 (> 25 ng/mL), CXCL1 (> 30 ng/mL) and CXCL2 (> 20 ng/mL). Although simultaneous exposure to RA did not significantly affect this response, 12 h pre-treatment with 0.1 microM all-trans RA strongly suppressed mRNA expression and protein release of all chemokines. The anti-inflammatory activity of RA engaged RA and retinoid X receptors and correlated with a decreased expression of the lipopolysaccharides co-receptor CD14. A minor reduction of nuclear NF-kappaB was observed but not significant, activation of Jun amino-terminal kinase, p38 and signal transducer and activator of transcription 3 were not altered by RA. The results suggest that retinoids should be further investigated as candidates for the treatment of neuroinflammation.

post to: CiteULike

p90 activation contributes to cerebral ischemic damage via phosphorylation of Na+/H+ exchanger isoform 1.

Publication Date: 2010 Sep 1 PMID: 20557427
Authors: Manhas, N. - Shi, Y. - Taunton, J. - Sun, D.
Journal: J Neurochem

Excessive activation of Na+/H+ exchanger isoform 1 (NHE-1) plays a role in cerebral ischemic injury. The current study investigated whether NHE-1 protein in ischemic brains is regulated by extracellular signal-regulated kinase (ERK)/90-kDa ribosomal S6 kinase (p90(RSK)) signaling pathways. A transient focal ischemia in mice was induced by a 60-min-occlusion of the middle cerebral artery followed by reperfusion for 3, 10, or 60 min (Rp). Expression of phosphorylated ERK 1/2 was significantly elevated in the ipsilateral hemispheres at 3-10 min Rp and reduced by 60 min Rp. An increase in phosphorylation of p90(RSK), a known NHE-1 kinase, was also detected at 3-10 min Rp, which was accompanied with a transient elevation of NHE-1 phosphorylation (p-NHE-1). Stimulation of p90(RSK) in ischemic neurons was downstream of ERK activation because inhibition of MEK1 (MAP kinase/ERK kinase) with its inhibitor U0126 blocked phosphorylation of p90(RSK). Moreover, direct inhibition of p90(RSK) by its selective inhibitor fluoromethyl ketone not only reduced p-NHE-1 expression but also ischemic infarct volume. Taken together, our study revealed that reperfusion triggers a transient stimulation of the ERK/p90(RSK) pathway. p90(RSK) activation contributes to cerebral ischemic damage in part via activation of NHE-1 protein.

post to: CiteULike

Neurones express glutamine synthetase when deprived of glutamine or interaction with astrocytes.

Publication Date: 2010 Sep 1 PMID: 20557426
Authors: Fernandes, S. P. - Dringen, R. - Lawen, A. - Robinson, S. R.
Journal: J Neurochem

Glutamine synthetase (GS) forms glutamine by catalyzing the ATP-dependent amidation of glutamate. In healthy brains, GS is restricted to astrocytes but in Alzheimer's disease and cell culture, GS has been detected in neurones. The present study demonstrates the expression of functional GS in cultured cerebellar granule cells and investigates conditions required to reduce this expression. Cerebellar granule cells from neonatal rats were grown in the absence of glutamine. Immunostaining revealed that the majority of neurones contained GS in their somata and dendrites. Treatment of neuronal cultures with glutamine greatly reduced the enzymatic activity of GS and also reduced the intensity of GS immunolabelling in dendrites. GS activity was reduced by 32% in neurones that had been transiently co-cultured with astrocytes, whereas GS immunoreactivity was largely abolished from neurones that had been directly seeded onto astrocytic monolayers. These results imply that GS expression in neurones occurs in response to a reduced availability of glutamine from astrocytes, and that neuronal GS expression represents a default phenotype which is normally suppressed via direct contacts with astrocytes. The aberrant expression of GS in sporadic neurones in Alzheimer's disease may indicate an impairment of such interactions.

post to: CiteULike

Dual modulation of inward rectifier potassium currents in olfactory neuronal cells by promiscuous G protein coupling of the oxytocin receptor.

Publication Date: 2010 Sep 1 PMID: 20557424
Authors: Gravati, M. - Busnelli, M. - Bulgheroni, E. - Reversi, A. - Spaiardi, P. - Parenti, M. - Toselli, M. - Chini, B.
Journal: J Neurochem

Oxytocin receptor is a seven transmembrane receptor widely expressed in the CNS that triggers G(i) or G(q) protein-mediated signaling cascades leading to the regulation of a variety of neuroendocrine and cognitive functions. We decided to investigate whether and how the promiscuous receptor/G protein coupling affects neuronal excitability. As an experimental model, we used the immortalized gonadotropin-releasing hormone-positive GN11 cell line displaying the features of immature, migrating olfactory neurons. Using RT-PCR analysis, we detected the presence of oxytocin receptors whose stimulation by oxytocin led to the accumulation of inositol phosphates and to the inhibition of cell proliferation, and the expression of several inward rectifier (IR) K+ channel subtypes. Moreover, electrophysiological and pharmacological inspections using whole-cell patch-clamp recordings evidenced that in GN11 cells, IR channel subtypes are responsive to oxytocin. In particular, we found that: (i) peptide activation of receptor either inhibited or stimulated IR conductances, and (ii) IR current inhibition was mediated by a pertussis toxin-resistant G protein presumably of the G(q/11) subtype, and by phospholipase C, whereas IR current activation was achieved via receptor coupling to a pertussis toxin-sensitive G(i/o) protein. The findings suggest that neuronal excitability might be tuned by a single peptide receptor that mediates opposing effects on distinct K+ channels through the promiscuous coupling to different G proteins.

post to: CiteULike

Endoplasmic reticulum Ca signaling and mitochondrial Cyt c release in astrocytes following oxygen and glucose deprivation.

Publication Date: 2010 Sep 1 PMID: 20557423
Authors: Liu, Y. - Kintner, D. B. - Begum, G. - Algharabli, J. - Cengiz, P. - Shull, G. E. - Liu, X. J. - Sun, D.
Journal: J Neurochem

In the present study, we investigated changes of cytosolic Ca2+([Ca2+](cyt)), endoplasmic reticulum Ca2+([Ca2+](ER)) and mitochondrial Ca2+(Ca2+(m)) in astrocytes following oxygen/glucose deprivation and reoxygenation (OGD/REOX). Two hours OGD did not cause changes in [Ca2+](cyt), but led to a significant increase in [Ca2+](ER). The elevation in [Ca2+](ER) continued and reached a peak level (130 +/- 2 microM) by 90 min REOX. An abrupt release of Ca2+(ER) occurred during 1.5-2.5 h REOX, which was accompanied with a delayed and sustained rise in [Ca2+](cyt). Moreover, Ca2+(m) content was increased significantly within 15 min REOX followed by a secondary rise (approximately 4.5-fold) and a release of mitochondrial cytochrome c (Cyt c). Astrocytes exhibited translocation of Cyt c from mitochondria to endoplasmic reticulum (ER) and up regulation of ER stress protein p-eIF2alpha. Blocking Na+-K+-Cl(-) cotransporter isoform 1 activity, either by its potent inhibitor bumetanide or genetic ablation, abolished release of ER Ca2+, delayed rise in [Ca2+](cyt) and Ca2+(m). Inhibition of the reverse mode operation of the Na+/Ca2+ exchanger significantly attenuated OGD/REOX-mediated Cyt c release. In summary, this study illustrates that OGD/REOX triggers a time-dependent loss of Ca2+ homeostasis in cytosol and organelles (ER and mitochondria) in astrocytes. Collective stimulation of Na+-K+-Cl(-) cotransporter isoform 1 and reverse mode function of Na+/Ca2+ exchanger contributes to these changes.

post to: CiteULike

Reduction in voltage-gated K+ channel activity in primary sensory neurons in painful diabetic neuropathy: role of brain-derived neurotrophic factor.

Publication Date: 2010 Sep 1 PMID: 20557422
Authors: Cao, X. H. - Byun, H. S. - Chen, S. R. - Cai, Y. Q. - Pan, H. L.
Journal: J Neurochem

Abnormal hyperexcitability of primary sensory neurons plays an important role in neuropathic pain. Voltage-gated potassium (Kv) channels regulate neuronal excitability by affecting the resting membrane potential and influencing the repolarization and frequency of the action potential. In this study, we determined changes in Kv channels in dorsal root ganglion (DRG) neurons in a rat model of diabetic neuropathic pain. The densities of total Kv, A-type (IA) and sustained delayed (IK) currents were markedly reduced in medium- and large-, but not in small-, diameter DRG neurons in diabetic rats. Quantitative RT-PCR analysis revealed that the mRNA levels of IA subunits, including Kv1.4, Kv3.4, Kv4.2, and Kv4.3, in the DRG were reduced approximately 50% in diabetic rats compared with those in control rats. However, there were no significant differences in the mRNA levels of IK subunits (Kv1.1, Kv1.2, Kv2.1, and Kv2.2) in the DRG between the two groups. Incubation with brain-derived neurotrophic factor (BDNF) caused a large reduction in Kv currents, especially IA currents, in medium and large DRG neurons from control rats. Furthermore, the reductions in Kv currents and mRNA levels of IA subunits in diabetic rats were normalized by pre-treatment with anti-BDNF antibody or K252a, a TrkB tyrosine kinase inhibitor. In addition, the number of medium and large DRG neurons with BDNF immunoreactivity was greater in diabetic than control rats. Collectively, our findings suggest that diabetes primarily reduces Kv channel activity in medium and large DRG neurons. Increased BDNF activity in these neurons likely contributes to the reduction in Kv channel function through TrkB receptor stimulation in painful diabetic neuropathy.

post to: CiteULike

The antidepressant phenelzine protects neurons and astrocytes against formaldehyde-induced toxicity.

Publication Date: 2010 Sep 1 PMID: 20557421
Authors: Song, M. S. - Baker, G. B. - Dursun, S. M. - Todd, K. G.
Journal: J Neurochem

Reactive aldehydes have been implicated in the etiology of several neurological and psychiatric disorders, and there is considerable interest in drugs to counteract the actions of these aldehydes. Increased formaldehyde (FA) and up-regulation of semicarbazide-sensitive amine oxidase, which forms FA from methylamine, have been implicated in disorders such as cerebrovascular disorders, alcohol abuse, diabetes and Alzheimer's disease. Phenelzine (PLZ), a monoamine oxidase inhibitor, is an antidepressant that has recently received attention for its neuroprotective/neurorescue properties. We investigated FA-induced toxicity and the effects of PLZ using rat primary cortical neurons and astrocytes and found that FA induced toxicity in neurons and astrocytes by multiple means. In astrocytes, FA decreased glutamate transporter expression, inhibiting glutamate uptake. PLZ reversed the decrease of glutamate uptake and the alteration of the second messengers, AKT and p38, induced by FA. PLZ alone affected the GLT-1 glutamate transporter in opposite directions in astrocytes and neurons. Thus, PLZ has multiple actions in neurons and astrocytes that may contribute to its neuroprotection.

post to: CiteULike

Decreased GABA(B) receptors in the cingulate cortex and fusiform gyrus in autism.

Publication Date: 2010 Sep 1 PMID: 20557420
Authors: Oblak, A. L. - Gibbs, T. T. - Blatt, G. J.
Journal: J Neurochem

Autism is a behaviorally defined neurodevelopmental disorder and among its symptoms are disturbances in face and emotional processing. Emerging evidence demonstrates abnormalities in the GABAergic (gamma-aminobutyric acid) system in autism, which likely contributes to these deficits. GABA(B) receptors play an important role in modulating synapses and maintaining the balance of excitation-inhibition in the brain. The density of GABA(B) receptors in subjects with autism and matched controls was quantified in the anterior and posterior cingulate cortex, important for socio-emotional and cognitive processing, and the fusiform gyrus, important for identification of faces and facial expressions. Significant reductions in GABA(B) receptor density were demonstrated in all three regions examined suggesting that alterations in this key inhibitory receptor subtype may contribute to the functional deficits in individuals with autism. Interestingly, the presence of seizure in a subset of autism cases did not have a significant effect on the density of GABA(B) receptors in any of the three regions.

post to: CiteULike

The formation of tau pathological phospho-epitopes in the axon is prevented by the dephosphorylation of selective sites in primary hippocampal neurons over-expressing human tau.

Publication Date: 2010 Sep 1 PMID: 20550628
Authors: Bertrand, J. - Senechal, P. - Zummo-Soucy, M. - Plouffe, V. - Leclerc, N.
Journal: J Neurochem

In tauopathies including Alzheimer's disease, the axonal microtubule-associated protein tau becomes hyperphosphorylated at pathological epitopes and accumulates in the somato-dendritic compartment. However, it remains unclear whether tau becomes phosphorylated at these epitopes in the somato-dendritic compartment and/or in the axon. In primary hippocampal neurons where human tau was over-expressed both in the somato-dendritic compartment and the axon, the pathological epitopes recognized by the antibodies AT8 (S199/S202/T205), AT100 (T212/S214/T217), and AT180 (T231/S235) were found in the somato-dendritic compartment but not in the axon where tau was either not phosphorylated (T205 and T217) or not simultaneously phosphorylated (T231 and S235) at sites included in the above epitopes. When transfected neurons were treated with the phosphatase inhibitor, okadaic acid, AT8, AT100 and AT180 epitopes were observed in the axon, indicating that tau was dephosphorylated at selective sites of pathological epitopes in this compartment. Expression of tau mutants where one phosphorylation site included in the above epitopes was mutated in alanine showed that the formation of one of these epitopes was not required for the formation of the two others in primary hippocampal neurons. All together our results indicate that in the somato-dendritic compartment, the kinase and phosphatase activity does not prevent the formation of pathological epitopes whereas in the axon, the amount of tau phosphorylated at the pathological epitopes is regulated by phosphatase activity, most likely that of phosphoserine/phosphothreonine phosphatase 2A, the major tau phosphatase. This indicates that if the pathological epitopes are initially formed in the axon in Alzheimer's disease brain, the activation of phosphatases could be an efficient way to abolish their generation.

post to: CiteULike

Regulation of markers of synaptic function in mouse models of depression: chronic mild stress and decreased expression of VGLUT1.

Publication Date: 2010 Sep 1 PMID: 20550627
Authors: Elizalde, N. - Pastor, P. M. - Garcia-Garcia, A. L. - Serres, F. - Venzala, E. - Huarte, J. - Ramirez, M. J. - Del Rio, J. - Sharp, T. - Tordera, R. M.
Journal: J Neurochem

Depression has been linked to failure in synaptic plasticity originating from environmental and/or genetic risk factors. The chronic mild stress model regulates the expression of synaptic markers of neurotransmitter function and associated depressive-like behaviour. Moreover, mice heterozygous for the synaptic vesicle protein vesicular glutamate transporter 1 (VGLUT1), have been proposed as a genetic model of deficient glutamate function linked to depressive-like behaviour. Here, we aimed to identify, in these two experimental models, mechanisms of failure in synaptic plasticity, common to stress and impaired glutamate function. First, we show that chronic mild stress induced a transient decrease of different plasticity markers (VGLUT1, synapsin 1, sinaptophysin, rab3A and activity regulated cytoskeletal protein - Arc) but a long-lasting decrease of the brain derived neurotrophic factor as well as depressive-like behaviour. The immediate early gene Arc was also down-regulated in VGLUT1+/- heterozygous mice. In contrast, an opposite regulation of synapsin 1 was observed. Finally, both models showed a marked increase of cortical Arc response to novelty. Increased Arc response to novelty could be suggested as a molecular mechanism underlying failure to adapt to environmental changes, common to chronic stress and altered glutamate function. Further studies should investigate whether these changes are associated to depressive-like behaviour both in animal models and in depressed patients.

post to: CiteULike

Mending the broken brain: neuroimmune interactions in neurogenesis.

Publication Date: 2010 Sep 1 PMID: 20534007
Authors: Molina-Holgado, E. - Molina-Holgado, F.
Journal: J Neurochem

Neuroimmune networks and the brain endocannabinoid system contribute to the maintenance of neurogenesis. Cytokines and chemokines are important neuroinflammatory mediators that are involved in the pathological processes resulting from brain trauma, ischemia and chronic neurodegenerative diseases. However, they are also involved in brain repair and recovery. Compelling evidence obtained, in vivo and in vitro, establish a dynamic interplay between the endocannabinoid system, the immune system and neural stem/progenitor cells (NSC) in order to promote brain self-repair. Cross-talk between inflammatory mediators and NSC might have important consequences for neural development and brain repair. In addition, brain immune cells (microglia) support NSC renewal, migration and lineage specification. The proliferation and differentiation of multipotent NSC must be precisely controlled during the development of the CNS, as well as for adult brain repair. Although signalling through neuroimmune networks has been implicated in many aspects of neural development, how it affects NSC remains unclear. However, recent findings have clearly demonstrated that there is bi-directional cross-talk between NSC, and the neuroimmune network to control the signals involved in self-renewal and differentiation of NSC. Specifically, there is evidence emerging that neuroimmune interactions control the generation of new functional neurones from adult NSC. Here, we review the evidence that neuroimmune networks contribute to neurogenesis, focusing on the regulatory mechanisms that favour the immune system (immune cells and immune molecules) as a novel element in the coordination of the self-renewal, migration and differentiation of NSC in the CNS. In conjunction, these data suggest a novel mode of action for the immune system in neurogenesis that may be of therapeutic interest in the emerging field of brain repair.

post to: CiteULike

Optogenetic control of striatal dopamine release in rats.

Publication Date: 2010 Sep 1 PMID: 20534006
Authors: Bass, C. E. - Grinevich, V. P. - Vance, Z. B. - Sullivan, R. P. - Bonin, K. D. - Budygin, E. A.
Journal: J Neurochem

Optogenetic control over neuronal firing has become an increasingly elegant method to dissect the microcircuitry of mammalian brains. To date, examination of these manipulations on neurotransmitter release has been minimal. Here we present the first in-depth analysis of optogenetic stimulation on dopamine neurotransmission in the dorsal striatum of urethane-anesthetized rats. By combining the tight spatial and temporal resolution of both optogenetics and fast-scan cyclic voltammetry we have determined the parameters necessary to control phasic dopamine release in the dorsal striatum of rats in vivo. The kinetics of optically induced dopamine release mirror established models of electrically evoked release, indicating that potential artifacts of electrical stimulation on ion channels and the dopamine transporter are negligible. Furthermore a lack of change in extracellular pH indicates that optical stimulation does not alter blood flow. Optical control over dopamine release is highly reproducible and flexible. We are able to repeatedly evoke concentrations of dopamine release as small as a single dopamine transient (50 nM). An inverted U-shaped frequency response curve exists with maximal stimulation inducing dopamine effluxes exceeding 500 nM. Taken together, these results have obvious implications for understanding the neurobiological basis of dopaminergic-based disorders and provide the framework to effectively manipulate dopamine patterns.

post to: CiteULike

Activation of mGluR7s inhibits cocaine-induced reinstatement of drug-seeking behavior by a nucleus accumbens glutamate-mGluR2/3 mechanism in rats.

Publication Date: 2010 Sep 1 PMID: 20534005
Authors: Li, X. - Li, J. - Gardner, E. L. - Xi, Z. X.
Journal: J Neurochem

The metabotropic glutamate receptor 7 (mGluR7) has been reported to be involved in cocaine and alcohol self-administration. However, the role of mGluR7 in relapse to drug seeking is unknown. Using a rat relapse model, we found that systemic administration of AMN082, a selective mGluR7 allosteric agonist, dose-dependently inhibits cocaine-induced reinstatement of drug-seeking behavior. Intracranial microinjections of AMN082 into the nucleus accumbens (NAc) or ventral pallidum, but not the dorsal striatum, also inhibited cocaine-primed reinstatement, an effect that was blocked by local co-administration of MMPIP, a selective mGluR7 antagonist. In vivo microdialysis demonstrated that cocaine priming significantly increased extracellular dopamine in the NAc, ventral pallidum and dorsal striatum, while increasing extracellular glutamate in the NAc only. AMN082 alone failed to alter extracellular dopamine, but produced a slow-onset long-lasting increase in extracellular glutamate in the NAc only. Pre-treatment with AMN082 dose-dependently blocked both cocaine-enhanced NAc glutamate and cocaine-induced reinstatement, an effect that was blocked by MMPIP or LY341497 (a selective mGluR2/3 antagonist). These data suggest that mGluR7 activation inhibits cocaine-induced reinstatement of drug-seeking behavior by a glutamate-mGluR2/3 mechanism in the NAc. The present findings support the potential use of mGluR7 agonists for the treatment of cocaine addiction.

post to: CiteULike

Bcl11A/CTIP1 mediates the effect of the glutamate receptor on axon branching and dendrite outgrowth.

Publication Date: 2010 Sep 1 PMID: 20534004
Authors: Kuo, T. Y. - Chen, C. Y. - Hsueh, Y. P.
Journal: J Neurochem

While neuronal activity regulates neurite outgrowth and branching, the details of the underlying mechanisms are still largely unclear. This study investigated the effect of the glutamate receptors on neuritogenesis using cultured hippocampal neurons. At 3-4 days in vitro, NMDA treatment promoted axon branching but not primary axon extension. In contrast, blockade of the NMDA receptor (NMDAR) by AP5 treatment enhanced primary axon extension. NMDAR activation also increased dendrite number and total dendrite length. These results suggest that NMDAR controls axon and dendrite morphogenesis. A previous study demonstrated that knockdown of the zinc finger transcription factor B cell lymphoma 11A-long (Bcl11A-L) reduces deleted in colorectal cancer (DCC) and microtubule-associated protein (MAP) 1b expression, thereby promoting axon branching. Here, glutamate stimulation down-regulated the levels of the Bcl11A-L, DCC, MAP1b, and MAP2c proteins. Over-expression of either Bcl11A-L or DCC countered the effect of NMDA or glutamate on axon branching and dendrite outgrowth, indicating that the Bcl11A-L/DCC pathway is an important downstream effector of glutamate receptors in neurite arborization. Because knockdown of Bcl11A-L did not down-regulate MAP2c, our results suggest that glutamate receptors also use a Bcl11A-L-independent pathway to control dendrite outgrowth. To summarize, this study reveals novel pathways downstream of glutamate receptors that regulate axon and dendrite arborization.

post to: CiteULike

Differences in activation of ERK1/2 and p38 kinase in Jnk3 null mice following KA treatment.

Publication Date: 2010 Sep 1 PMID: 20534003
Authors: de Lemos, L. - Junyent, F. - Verdaguer, E. - Folch, J. - Romero, R. - Pallas, M. - Ferrer, I. - Auladell, C. - Camins, A.
Journal: J Neurochem

The MAPK family is formed by extracellular signal-regulated kinases p38 kinase and stress-activated protein kinases (SAPK/JNK). There are three genes that encode for three JNK proteins. JNK3 is mainly expressed in the central nervous system and has been related to various processes in that tissue. Specifically, JNK3 plays a crucial role in neuronal death in several neurodegenerative diseases. The activation of this kinase has been described in epilepsy, Alzheimer's disease, Parkinson's disease and Huntington's disease. Different studies have shown that the lack of the Jnk3 gene confers neuroprotection. However, the specific mechanism involved in such neuroprotection has not yet been elucidated. Therefore, in the present study, we analyzed the neuroprotection in mice lacking Jnk3 against neuronal death induced by kainic acid. Moreover, we analyzed the activation of different MAPKs. The results revealed that neuronal death was attenuated and different activation/inactivation of p38 and extracellular signal-regulated kinases 1/2 was reported with respect to control. Therefore, the data indicate that the lack of the JNK3 protein modulates other MAPKs and these changes could also have a pivotal role in neuroprotection.

post to: CiteULike

Endocrine disrupting chemicals bind to a novel receptor, microtubule-associated protein 2, and positively and negatively regulate dendritic outgrowth in hippocampal neurons.

Publication Date: 2010 Sep 1 PMID: 20534002
Authors: Matsunaga, H. - Mizota, K. - Uchida, H. - Uchida, T. - Ueda, H.
Journal: J Neurochem

The present study demonstrates a novel high-affinity neuronal target for endocrine disrupting chemicals (EDCs), which potentially cause psychological disorders. EDCs competitively inhibited the binding of bovine serum albumin-conjugated progesterone to recombinant human microtubule-associated protein 2C (rhMAP2C) with an inhibition constant at picomolar levels. In the rhMAP2C-stimulated tubulin assembly assay, agonistic enhancement was observed with dibutyl phthalate and pentachlorphenol and pregnenolone, while an inverse agonistic effect was observed with 4-nonylphenol. In contrast, progesterone and many of the EDCs, including bisphenol A, antagonized the pregnenolone-induced enhancement of rhMAP2C-stimulated tubulin assembly. These agonistic and inverse agonistic actions were not observed in tubulin assembly stimulated with Delta1-71 rhMAP2C, which lacks the steroid-binding site. Using a dark-field microscopy, pregnenolone and pentachlorphenol were observed to generate characteristic filamentous microtubules in a progesterone- or bisphenol A-reversible manner. In cultured hippocampal neurons, similar agonist-antagonist relationships were reproduced in terms of dendritic outgrowth. Fluorescent recovery after photobleaching of hippocampal neurons showed that pregnenolone and agonistic EDCs enhanced, but that 4-nonylphenol inhibited the MAP2-mediated neurite outgrowth in a progesterone- or antagonistic EDC-reversible manner. Furthermore, none of the examined effects were affected by mifepristone or ICI-182,786 i.e. the classical progesterone and estrogen receptor antagonists. Taken together, these results suggest that EDCs cause a wide variety of significant disturbances to dendritic outgrowth in hippocampal neurons, which may lead to psychological disorders following chronic exposure during early neuronal development.

post to: CiteULike

The central serotonin(2B) receptor: a new pharmacological target to modulate the mesoaccumbens dopaminergic pathway activity.

Publication Date: 2010 Sep 1 PMID: 20534001
Authors: Auclair, A. L. - Cathala, A. - Sarrazin, F. - Depoortere, R. - Piazza, P. V. - Newman-Tancredi, A. - Spampinato, U.
Journal: J Neurochem

The function of the serotonin(2B) receptor (5-HT(2B)R) in the mammalian brain is poorly characterized, especially with regard to its influence on dopamine (DA) neuron activity. Here, we assessed this issue by evaluating effects of 5-HT(2B)Rs ligands in the control of striatal and accumbal DA outflow, using in vivo microdialysis in halothane-anesthetized rats, and amphetamine-induced hyperlocomotion in vigil rats. The selective 5-HT(2B)R antagonist 1-[(2-chloro-3,4-dimethoxyphenyl)methyl]-2,3,4,9-tetrahydro-6-methyl-1H-py rido[3,4-B]indole (LY 266097; 0.16 mg/kg, i.p.) had no influence on basal accumbal and striatal DA outflow but reduced significantly accumbal DA outflow when injected at 0.63 mg/kg. A significant reduction of basal DA outflow in the nucleus accumbens was also observed after i.p. administration of 0.16 mg/kg 2-amino-4-(4-fluoronaphth-1-yl)-6-isopropylpyrimidine, another selective 5-HT(2B)R antagonist. In contrast, the 5-HT(2B)R agonist alpha-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine (3 mg/kg, s.c.) had no influence on basal DA outflow in either brain region. The increase in striatal and accumbal DA outflow induced by the 5-HT(2C)R inverse agonist 5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2,3-f] indole (5 mg/kg, i.p.) was unaltered by LY 266097 (0.63 mg/kg) pre-treatment. Conversely, LY 266097 (0.63 mg/kg) significantly diminished the increase in DA outflow induced by haloperidol (0.01 mg/kg, s.c.) or amphetamine (0.5 mg/kg, i.p.) in the nucleus accumbens, but not in the striatum. Amphetamine-induced hyperlocomotion (1 mg/kg) was also attenuated by LY 266097 (0.63 mg/kg). These findings demonstrate that 5-HT(2B)Rs exert a facilitatory control on mesoaccumbens DA pathway activity, and suggest that they may constitute a new target for improved treatment of DA-related neuropsychiatric disorders.

post to: CiteULike

Axon-oligodendrocyte interactions during developmental myelination, demyelination and repair.

Publication Date: 2010 Sep 1 PMID: 20524961
Authors: Piaton, G. - Gould, R. M. - Lubetzki, C.
Journal: J Neurochem

In multiple sclerosis, CNS demyelination is often followed by spontaneous repair, mostly achieved by adult oligodendrocyte precursor cells. Extent of this myelin repair differs, ranging from very low, limited to the plaque border, to extensive, with remyelination throughout the 'shadow plaques.' In addition to restoring neuronal connectivity, new myelin is neuroprotective. It reduces axonal loss and thus disability progression. Reciprocal communication between neurons and oligodendrocytes is essential for both myelin biogenesis and myelin repair. Hence, deciphering neuron-oligodendrocyte communication is not only important for understanding myelination per se, but also the pathophysiology that underlies demyelinating diseases and the development of innovative therapeutic strategies.

post to: CiteULike

Adaptive immune regulation of glial homeostasis as an immunization strategy for neurodegenerative diseases.

Publication Date: 2010 Sep 1 PMID: 20524958
Authors: Kosloski, L. M. - Ha, D. M. - Hutter, J. A. - Stone, D. K. - Pichler, M. R. - Reynolds, A. D. - Gendelman, H. E. - Mosley, R. L.
Journal: J Neurochem

Neurodegenerative diseases, notably Alzheimer's and Parkinson's diseases, are amongst the most devastating disorders afflicting the elderly. Currently, no curative treatments or treatments that interdict disease progression exist. Over the past decade, immunization strategies have been proposed to combat disease progression. Such strategies induce humoral immune responses against misfolded protein aggregates to facilitate their clearance. Robust adaptive immunity against misfolded proteins, however, accelerates disease progression, precipitated by induced effector T cell responses that lead to encephalitis and neuronal death. Since then, mechanisms that attenuate such adaptive neurotoxic immune responses have been sought. We propose that shifting the balance between effector and regulatory T cell activity can attenuate neurotoxic inflammatory events. This review summarizes advances in immune regulation to achieve a homeostatic glial response for therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are also discussed.

post to: CiteULike

1-Benzyl-1,2,3,4-tetrahydroisoquinoline binds with tubulin beta, a substrate of parkin, and reduces its polyubiquitination.

Publication Date: 2010 Sep 1 PMID: 20067570
Authors: Kohta, R. - Kotake, Y. - Hosoya, T. - Hiramatsu, T. - Otsubo, Y. - Koyama, H. - Hirokane, Y. - Yokoyama, Y. - Ikeshoji, H. - Oofusa, K. - Suzuki, M. - Ohta, S.
Journal: J Neurochem

Substances that mimic the actions of causative gene products of familial Parkinson's disease (PD) are candidate as causative agents of idiopathic PD. 1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ), an endogenous neurotoxin, is present at three times higher levels in CSF of PD patients than in CSF of control subjects. However, the mechanism of 1BnTIQ's neurotoxicity is unclear. In this study, we tried to identify 1BnTIQ-binding proteins by using a diazido-functionalized 1BnTIQ analog, 1-(3-azido-5-azidomethylbenzyl)-1,2,3,4-tetrahydroisoquinoline, designed and synthesized as a probe for radioisotope-free photoaffinity labeling. One major photolabeled protein identified using this probe was tubulin beta, which has been reported to be a substrate of parkin, a ubiquitin E3 ligase and a causative gene product of familial PD. Loss of function mutation of parkin is reported to result in loss of tubulin beta ubiquitination. Therefore, we examined the effect of 1BnTIQ on ubiquitination of tubulin beta. The polyubiquitinated tubulin beta level in human neuroblastoma SH-SY5Y cells was reduced in the presence of 1BnTIQ, even at concentrations as low as those detected in parkinsonian CSF. In vitro ubiquitination assay gave similar results. It is suggested that 1BnTIQ has the same effect on tubulin ubiquitination as does mutant parkin in familial PD. Taken together, substances which reduce polyubiquitination of tubulin such as 1BnTIQ are supposed to be candidates of etiological factors of PD.

post to: CiteULike