Molecular Brain Research最新文献

Narcolepsy is a chronic sleep disorder. It is linked to the HLA-DQB1*0602 allele. A recent report established a genetic linkage between narcolepsy and the chromosomal region 4p13–q21 that contains the Clock gene. We studied two SNPs in the Clock gene aiming to find any association with narcolepsy. We did not find differences in genetic frequencies in the patients group. We concluded that these two SNPs are not associated with narcolepsy.

This study examined the hypothesis that the high prevalence of white matter injury in premature infants is associated with increased expression of calcium-permeable forms of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of glutamate receptors in pre-myelinating white matter. We characterized expression of subunits of the AMPA, and for reference, the N-methyl-d-aspartate (NMDA), glutamate receptors at 0.5, 0.65, 0.85, and term gestation in the ovine fetal white matter and cerebral cortex. There was a low expression of the critical calcium-impermeable AMPA receptor GluR2 subunit in subcortical white matter both absolutely and relative to other AMPA subunits throughout gestation. In contrast, GluR2 subunit mRNA expression fell in the cerebral cortex with increasing gestation whereas protein expression increased. These findings suggest a vulnerability of subcortical white matter to AMPA receptor-mediated calcium toxicity throughout the second half of gestation. Thus, the hypothesis that AMPA receptor-mediated glutamate toxicity contributes to brain damage in premature infants needs to be revised.

α₁-Adrenoreceptors (AR), of which three subtypes exist (α_1A-, α_1B- and α_1D-AR) are G-protein-coupled receptors that mediate the actions of norepinephrine and epinephrine both peripherally and centrally. In the CNS, α₁-ARs are found in the hippocampus where animal studies have shown the ability of α₁-AR agents to modulate long-term potentiation and memory; however, the precise distribution of α₁-AR expression and its subtypes in the human brain is unknown making functional comparisons difficult. In the human hippocampus, ³H-prazosin (α₁-AR antagonist) labels only the dentate gyrus (molecular, granule and polymorphic layers) and the stratum lucidum of the CA3 homogenously. Human α_1A-AR mRNA in the hippocampus is observed only in the dentate gyrus granule cell layer, while α_1D-AR mRNA expression is observed only in the pyramidal cell layers of CA1, CA2 and CA3, regions where ³H-prazosin did not bind. α_1B-AR mRNA is not expressed at detectable levels in the human hippocampus. These results confirm a difference in hippocampal α₁-AR localization between rat and humans and further describe a difference in the localization of the α_1A- and α_1D-AR mRNA subtype between rats and humans.

The purpose of this study is to determine if calcium/calmodulin-dependent protein kinase-II (CaMKII) plays a role in neuronal cell death and if inhibition of this kinase affords some neuroprotection in the RGC-5 retinal ganglion cell line. The RGC-5 cells were treated with glutamate at various concentrations for increasing increments of time. Cytotoxicity was assayed by measuring the lactate dehydrogenase (LDH) leakage from non-viable cells and TUNEL assays. The involvement of caspase-3, Bcl-2 and caspase-8 in glutamate-induced cytotoxicity was determined by immunoblots and/or real time RT-PCR. In addition, the autocamtide-2-related inhibitory peptide (AIP), a specific inhibitor of CaMKII, was used to determine the involvement of CaMKII in glutamate-induced RGC-5 cell death. Application of increasing concentrations of glutamate to RGC-5 cells caused a dose-dependent increase in the level of cell death after 24 h. There was a glutamate-stimulated increase in the expression of caspase-8 and caspase-3 and a corresponding decrease in Bcl-2. The active fragment of caspase-3 increased in glutamate-treated cells. An early transient increase in the expression of CaMKIIα_B gene and a corresponding CaMKIIα nuclear translocation was found in glutamate-treated cells. Treatment with AIP blocked the activation of caspase-3 and protected RGC from glutamate-mediated cell death but did not alter the glutamate-enhanced expression levels of caspase-8 or caspase-3. This report shows the likely involvement of a transcript of the CaMKIIα gene in the cytotoxicity response of RGC-5 cells similar to previous reports in the neural retina. AIP is shown to be a neuroprotectant for RGC-5 cells as was reported for the neural retina.

The vesicular monoamine transporter-2 (VMAT2) sequesters monoamine neurotransmitters into vesicles and prevents neurotoxicity. Human or monkey striatum generated three VMAT2 immunoreactive proteins of ∼75 kDa, ∼52–55 kDa, and ∼45 kDa. The ∼55-kDa band is considered the unglycosylated native protein. Deglycosylation of the VMAT2 from striatum or human VMAT2 expressed in HEK293 cells yielded a ∼45-kDa, but not a 55-kDa immunoreactive band. We investigated this apparent mismatch between observed molecular size and predicted size.

Nicotine is known to induce the release of multiple neurotransmitters, including glutamate and dopamine, through activation of nicotinic receptors. Gene expression in the N-methyl-d-aspartate postsynaptic density (NMDA-PSD), as well as other functional groups, was compared in postmortem hippocampus of schizophrenic and nonmentally ill smokers and nonsmokers utilizing a microarray and quantitative RT-PCR approach. The expression of 277 genes was significantly changed between all smokers and nonsmokers. Specific gene groups, most notably genes expressed in the NMDA-PSD, were prevalent among these transcripts. Analysis of the interaction between smoking and schizophrenia identified several genes in the NMDA-PSD that were differentially affected by smoking in patients. The present findings suggest that smoking may differentially modulate glutamatergic function in schizophrenic patients and control subjects. The biological mechanisms underlying chronic tobacco use are likely to differ substantially between these two groups.

A dramatic example of neuronal and physiological plasticity in adult mammals occurs during the transition from a non-maternal to a maternal, lactating state. In this study, we compared gene expression within a large continuous region of the CNS involved in maternal behaviors (hypothalamus, preoptic regions, and nucleus accumbens) between lactating (L) (postpartum Day 7) and randomly cycling virgin (V) outbred mice. Using high-density oligonucleotide arrays representing 11,904 genes, two statistical algorithms were used to identify significant differences in gene expression: robust multiarray (P < 0.001) (n = 92 genes) and significance analysis of microarrays using a 10% false discover rate (n = 114 genes). 27 common genes were identified as significant using both techniques. A subset of genes (n = 5) were selected and examined by real-time PCR. Our findings were consistent with previous published work. For example, neuropeptide Y (NPY) and proenkephalin were elevated in L mice, whereas POMC was decreased. Increased levels of NPY Y2 receptor and polo-like kinase and decreased levels of endothelin receptor type b in L mice are examples of novel gene expression changes not previously identified. Expression differences occurred in broad classes. Together, our findings provide possible new material on gene expression changes that may support maternal behaviors. The advantages and drawbacks of sampling large CNS regions using arrays are discussed.

Epileptic seizures cause severe and long-lasting events on the architecture of the brain, including neuronal cell death, accompanied neurogenesis, reactive gliosis, and mossy fiber sprouting. However, it remains uncertain whether these functional and anatomical alterations are associated with the development of hyperexcitability, or as inhibitory processes. Neurotrophic factors are probable mediators of these pathophysiological events. The present study was designed to clarify the role of various neurotrophic factors on the pilocarpine model of seizures. At 4 h following pilocarpine-induced seizures, expression of NGF, BDNF, HB-EGF, and FGF-2 increased only in the mice manifesting tonic–clonic convulsions and not in mice without seizures. NT-3 expression decreased in pilocarpine-treated mice experiencing seizures, tonic–clonic or not, compared to mice with no seizures. Neuronal cell damage, which was evident by Fluoro-Jade B staining, was observed within 24 h in the mice exhibiting tonic–clonic seizures, followed by an increase in the number of BrdU-positive cells and glial cells, which were evident after 2 days. None of these pathophysiological changes occurred in the mice which showed no seizures, although they were injected with pilocarpine, nor in the activated epilepsy-prone EL mice, which experienced repeated severe seizures. Together, these results suggest that neuronal damage occurring in the brain of the mice manifesting tonic–clonic seizures is accompanied by neurogenesis. This sequence of events may be regulated through changes in expression of neurotrophic factors such as NGF, BDNF, HB-FGF, and NT-3.

Cyclooxygenase (COX) is the rate-limiting enzyme in the synthesis of prostaglandins (PGs) from arachidonic acid. Evidence suggests that neuronal COX-2 gene expression is mainly regulated by the transcription factor nuclear factor kappa-B (NF-κB). The present study was undertaken to determine whether there is a shared regulation of NF-κB or of nuclear factor of activated T-cells cytoplasmic (NFATc) with COX-2 and whether these transcription factors known to regulate COX-2 expression are altered in brain from COX-2 knockout (COX-2^−/−) mice compared to wild type. We found a decrease in NF-κB DNA–protein binding activity, which was accompanied by a reduction of the phosphorylation state of both I-κBα and p65 proteins in the COX-2^−/− mice. The mRNA and protein levels of p65 were also reduced in COX-2^−/− mice, whereas total cytoplasmic I-κB protein level was not significantly changed. Taken together, these changes may be responsible for the observed decrease in NF-κB DNA binding activity. NF-κB DNA binding activity was selectively affected in the COX-2^−/− mice compared to the wild type as there was no significant change in NFATc DNA binding activity. Overall, our data indicate that constitutive brain NF-κB activity is decreased in COX-2 deficient mice and suggest a reciprocal coupling between NF-κB and COX-2.