Neuroscience
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Brain damage, such as ischemic stroke, enhances proliferation of neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ). To date, no reliable in vitro systems, which can be used to unravel the potential mechanisms underlying this lesion-induced effect, have been established. Here, we developed an ex vivo method to investigate how the proliferation of NSPCs changes over time after experimental stroke or excitotoxic striatal lesion in the adult rat brain by studying the effects of microglial cells derived from an injured brain on NSPCs. ⋯ Furthermore, we found that NSPCs derived from injured brains were more likely to differentiate into neurons and oligodendrocytes than astrocytes. Our ex vivo system reliably mimics what is observed in vivo following brain injury. It constitutes a powerful tool that could be used to identify factors that promote NSPC proliferation and differentiation in response to injury-induced activation of microglial cells, by using tools such as proteomics and gene array technology.
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Traumatic brain injury (TBI) causes massive brain damage. However, the secondary injury and temporal sequence of events with multiple mechanisms after the insult has not been elucidated. Here, we examined the occurrence of apoptosis and a causal relationship between inflammation and apoptosis in the TBI brain. ⋯ Interestingly, the expression profile of CD68 macrophage labeled cells closely resembled that of apoptotic cells after TBI, including the role of inflammatory signaling pathway in the progression of apoptotic cell death. These results taken together suggest that TBI induced upregulation of apoptosis-related genes, concomitant with the detection of apoptotic brain pathology during the 3-48 h post-injury period, which may be likely mediated by inflammation. Therapies designed at abrogating apoptosis and/or inflammation may prove effective when initiated at this subacute TBI phase.
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Comparative Study
Distinct effects of sonic hedgehog and Wnt-7a on differentiation of neonatal neural stem/progenitor cells in vitro.
Sonic hedgehog (Shh) and Wnt-7a are morphogens involved in embryonic as well as ongoing adult neurogenesis. Their effects on the differentiation and membrane properties of neonatal neural stem/progenitor cells (NS/PCs) were studied in vitro using NS/PCs transduced with either Shh or Wnt-7a. Eight days after the onset of in vitro differentiation the cells were analyzed for the expression of neuronal and glial markers using immunocytochemical and Western blot analysis, and their membrane properties were characterized using the patch-clamp technique. ⋯ The electrophysiological analysis revealed that Wnt-7a increased, while Shh decreased the incidence of cells displaying a neuron-like current pattern, represented by outwardly rectifying K(+) currents and tetrodotoxin-sensitive Na(+) currents. Additionally, Wnt-7a increased cell proliferation only at the early stages of differentiation, while Shh promoted proliferation within the entire course of differentiation. Thus we can conclude that Shh and Wnt-7a interfere differently with the process of neuronal differentiation and that they promote distinct stages of neuronal differentiation in neonatal NS/PCs.
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Oxidative stress and inflammation are important processes in the progression of Alzheimer's disease (AD). Recent studies have implicated the role of amyloid β-peptides (Aβ) in mediating these processes. In astrocytes, oligomeric Aβ induces the assembly of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complexes resulting in its activation to produce anionic superoxide. ⋯ Our data showed that laser light at 632.8 nm suppressed Aβ-induced superoxide production, colocalization between NADPH oxidase gp91(phox) and p47(phox) subunits, phosphorylation of cPLA(2,) and the expressions of IL-1β and iNOS in primary astrocytes. We demonstrated for the first time that 632.8 nm laser was capable of suppressing cellular pathways of oxidative stress and inflammatory responses critical in the pathogenesis in AD. This study should prove to provide the groundwork for further investigations for the potential use of laser therapy as a treatment for AD.
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Cholinergic neurons of the pontine laterodorsal tegmentum (LDT) play a critical role in regulation of behavioral state. Therefore, elucidation of mechanisms that control their activity is vital for understanding of how switching between wakefulness, sleep and anesthetic states is effectuated. In vivo studies suggest that GABAergic mechanisms within the pons play a critical role in behavioral state switching. ⋯ All of these GABA-mediated actions were found to occur in histochemically-identified cholinergic neurons. Taken together, these data indicate for the first time that cholinergic neurons of the LDT exhibit functional GABA(A, B and C) receptors, including extrasynaptically located GABA(A) receptors, which may be tonically activated by synaptic overflow of GABA. Accordingly, the activity of cholinergic LDT neurons is likely to be significantly affected by GABAergic tone within the nucleus, and so, demonstrated effects of GABA on behavioral state may be mediated, in part, via direct actions on cholinergic neurons in the LDT.