Hepatitis B virus X protein up-regulates tumor necrosis factor-α expression in cultured mesangial cells via ERKs and NF-κB pathways

Objective:To investigate the effects of hepatitis B virus(HBV)X protein(HBx)on the expression of tumor necrosis factor-α(TNF-α)in glomerular mesangial cells(GMCs)and the underlying intracellular signal pathways.Methods:The plasmid pCI-neo-X that carries the X gene of hepatitis B virus was transfected into cultured GMCs.HBx expression in the transfected GMCs was assessed by Western-blot.TNF-αprotein and mRNA were assessed by ELISA and semi-quantitative RT-PCR,respectively.Three kinase inhibitors-U0126,an inhibitor of extracellular signal-regulated kinases(ERKs);lactacvstin,an inhibitor of nuclear factor-κB(NF-κB);and SB203580,a selective inhibitor of p38 MAP kinase(p38 MAPK)were used to determine which intracellular signal pathways may underlie the action of HBx on TNF-αexpression in transfected GMCs.Results:A significant increase in HBx expression in pCI-neo-X transfected GMCs was detected at 36 h and 48 h,which was not affected by any of those kinase inhibitors mentioned above.A similar increase in the expression of both TNF-αprotein and mRNA was also observed at 36 h and 48 h,which was significantly decreased in the presence of U0126 or lactacytin,but not SB203580.Conclusions:HBx upregulates TNF-αexpression in cultured GMCs,possibly through ERKs and NF-κB pathway,but not p38 MAPK pathway.

Roles of extra-cellular signal-regulated protein kinase 5 signaling pathway in the development of spinal cord injury

Background:In consideration of characteristics and functions,extra-cellular signal-regulated protein kinase 5(ERK5)signaling pathway could be a new target for spinal cord injury(SCI)treatment.Our study aimed to evaluate the roles of ERK5 signaling pathway in secondary damage of SCI.Methods:We randomly divided 70 healthy Wistar rats into five groups:ten in the blank group,15 in the sham surgery+BIX02188(sham+B)group,15 in the sham surgery+dimethyl sulfoxide(DMSO;sham+D)group,15 in the SCI+BIX02188(SCI+B)group,and 15 in the SCI+DMSO(SCI+D)group.BIX02188 is a specific inhibitor of the ERK5 signaling pathway.SCI was induced by the application of vascular clips(with the force of 30 g)to the dura on T10 level,while rats in the sham surgery group underwent only T9-T11 laminectomy.BIX02188 or DMSO was intra-thecally injected at 1,6,and 12 h after surgery or SCI.Spinal cord samples were taken for testing at 24 h after surgery or SCI.Results:Expression of phosphorylated-ERK5(p-ERK5)significantly increased after SCI.Application of BIX02188 indeed inhibited ERK5 signaling pathway and reduced the degree of spinal cord tissue injury,neutrophil infiltration and proinflammatory cytokine expression,nuclear factor-kB(NF-kB)activation and apoptosis(measured by TdT-mediated 20-deoxyuridine 50-triphosphate nickend labeling,expression of Fas-ligand,BCL2-associated X[Bax],and B-cell lymphoma-2[Bcl-2]).Double immunofluorescence revealed activation of ERK5 in neurons and microglia after SCI.Conclusion:ERK5 signaling pathway was activated in spinal neurons and microglia,contributing to secondary injury of SCI.Moreover,inhibition of ERK5 signaling pathway could alleviate the degree of SCI,which might be related to its regulation of infiltration of inflammatory cells and release of inflammatory cytokines,expression of NF-kB and cell apoptosis.

L-and T-type Ca^(2+)channels dichotomously contribute to retinal ganglion cell injury in experimental glaucoma

Retinal ganglion cell apoptotic death is the main pathological characteristic of glaucoma,which is the leading cause of irreversible blindness.Disruption of Ca^(2+)homeostasis plays an important role in glaucoma.Voltage-gated Ca^(2+)channel blockers have been shown to improve vision in patients with glaucoma.However,whether and how voltage-gated Ca^(2+)channels are involved in retinal ganglion cell apoptotic death are largely unknown.In this study,we found that total Ca^(2+)current densities in retinal ganglion cells were reduced in a rat model of chronic ocular hypertension experimental glaucoma,as determined by whole-cell patch-clamp electrophysiological recordings.Further analysis showed that L-type Ca^(2+)currents were downregulated while T-type Ca^(2+)currents were upregulated at the later stage of glaucoma.Western blot assay and immunofluorescence experiments confirmed that expression of the Ca_(V)1.2 subunit of L-type Ca^(2+)channels was reduced and expression of the Ca_(V)3.3 subunit of T-type Ca^(2+)channels was increased in retinas of the chronic ocular hypertension model.Soluble tumor necrosis factor-α,an important inflammatory factor,inhibited the L-type Ca^(2+)current of isolated retinal ganglion cells from control rats and enhanced the T-type Ca^(2+)current.These changes were blocked by the tumor necrosis factor-αinhibitor XPro1595,indicating that both types of Ca^(2+)currents may be mediated by soluble tumor necrosis factor-α.The intracellular mitogen-activated protein kinase/extracellular signal-regulated kinase pathway and nuclear factor kappa-B signaling pathway mediate the effects of tumor necrosis factor-α.TUNEL assays revealed that mibefradil,a T-type calcium channel blocker,reduced the number of apoptotic retinal ganglion cells in the rat model of chronic ocular hypertension.These results suggest that T-type Ca^(2+)channels are involved in disrupted Ca^(2+)homeostasis and apoptosis of retinal ganglion cells in glaucoma,and application of T-type Ca^(2+)channel blockers,especially a specific CaV3.3 blocker,may be a potential strategy for the treatment of glaucoma.