Transforming growth factor-beta 1 enhances discharge activity of cortical neurons

Transforming growth factor-beta 1(TGF-β1)has been extensively studied for its pleiotropic effects on central nervous system diseases.The neuroprotective or neurotoxic effects of TGF-β1 in specific brain areas may depend on the pathological process and cell types involved.Voltage-gated sodium channels(VGSCs)are essential ion channels for the generation of action potentials in neurons,and are involved in various neuroexcitation-related diseases.However,the effects of TGF-β1 on the functional properties of VGSCs and firing properties in cortical neurons remain unclear.In this study,we investigated the effects of TGF-β1 on VGSC function and firing properties in primary cortical neurons from mice.We found that TGF-β1 increased VGSC current density in a dose-and time-dependent manner,which was attributable to the upregulation of Nav1.3 expression.Increased VGSC current density and Nav1.3 expression were significantly abolished by preincubation with inhibitors of mitogen-activated protein kinase kinase(PD98059),p38 mitogen-activated protein kinase(SB203580),and Jun NH2-terminal kinase 1/2 inhibitor(SP600125).Interestingly,TGF-β1 significantly increased the firing threshold of action potentials but did not change their firing rate in cortical neurons.These findings suggest that TGF-β1 can increase Nav1.3 expression through activation of the ERK1/2-JNK-MAPK pathway,which leads to a decrease in the firing threshold of action potentials in cortical neurons under pathological conditions.Thus,this contributes to the occurrence and progression of neuroexcitatory-related diseases of the central nervous system.

Apoptosis and Proinflammatory Cytokine Responses of Primary Mouse Microglia and Astrocytes Induced by Human H1N1 and Avian H5N1 Influenza Viruses

Patients with an influenza virus infection can be complicated by acute encephalopathy and encephalitis. To investigate the immune reactions involved in the neurocomplication, mouse microglia and astrocytes were isolated, infected with human H1N1 and avian H5N1 influenza viruses, and examined for their immune responses. We observed homogeneously distributed viral receptors, sialic acid （SA）-a2,3-Galactose （Gal） and SA-a2,6-Gal, on microglia and astrocytes. Both viruses were replicative and productive in microglia and astrocytes. Virus-induced apoptosis and cytopathy in infected cells were observed at 24 h post-infection （p.i.）. Expression of IL-1β, IL-6 and TNF-a mRNA examined at 6 h and 24 h p.i. was up-regulated, and their expression levels were considerably higher in H5N1 infection. The amounts of secreted proinflammatory IL-1β, IL-6 and TNF-a at 6 h and 24 h p.i. were also induced, with greater induction by H5N1 infection. This study is the first demonstration that both human H1N1 and avian H5N1 influenza viruses can infect mouse microglia and astrocytes and induce apoptosis, cytopathy, and proinflammatory cytokine production in them in vitro. Our results suggest that the direct cellular damage and the consequences of immunopathological injury in the CNS contribute to the influenza viral pathogenesis. Cellular ＆ Molecular Immunology.

Effects of NS1 variants of H5N1 influenza virus on interferon induction, TNFa response and p53 activity

Non-structural protein 1(NS1)is an important virulence factor of the highly pathogenic H5N1 avian influenza virus.A five-amino-acid(5 aa)deletion at position 80–84 and an aspartic acid to glutamic acid substitution at position 92(D92E)are two major NS1 mutations that are highly correlated with enhanced virulence.To investigate the effect of these mutations in H5N1 virulence,three H5N1-NS1 variants were constructed:NS51(lacking 5 aa at position 80–84),NS51(I)(carrying a 5-aa insertion at position 80–84)and NS51(IM)(carrying both the 5-aa insertion and the D92E mutation).We examined the effects of these mutations on interferon(IFN)induction,tumor-necrosis factor(TNF)a response,p53 activity and apoptosis.We found that the D92E mutation eliminated NS1’s repressive effect on IFN induction,while the 5-aa deletion resulted in enhanced resistance to TNFa responses.We also observed that all three variants exhibited a similar suppressive effect on p53 transcriptional activity,although none of them significantly influenced apoptosis of host cells.Our findings shed new light on the role of NS1 in the pathogenicity of H5N1 virus.