The Function And Mechanism Study Of Tunicamycin On Vascular Smooth Muscle Cell Proliferation And Migration

The abnormal proliferation and migration of vascular smooth muscle cell(VSMC), which is tuiggered by various external stimuli,contributes importantly to the pathogenesis of atherosclerosis and restenosis.Recent studies indicate that the endoplasmic reticulum (ER) stress is intensively.involved in the pathophysiological changes of VSMCs by various stimuli.However,the direct effects of ER stress on VSMC proliferation and migration remain unknown.Recent studies about the role of endoplasmic reticulum stress(ERS)in the progression of atherosclerosis attract much attention.Many researches focus on the injured endothelial cells and macrophages,while little was known about the potential atherogenic effects of ERS in the vascular smooth muscle cells(VSMCs).The present study investigated the role of ERS in the abnormal activated VSMCs with robust proliferation and migration,and therefore provided new evidence for the prevention and treatment of atherosclerosis.Tunicamycin(Tm)treatment on VSMCs caused ER stress obviously:XBP1mRNA splicing was notable; ATF6, Bip and CHOP mRNA expressions displayed a dose-dependent increase；XBP1s,Grp94and Bip protein expressions were also induced in a dose.dependent manner.However,Tm in this study showed modest effects on VSMC； cell viability by CCK-8and MTT analyses.Tm also induced mild apoptosis in VSMCs by the annexin V and PI double staining.In this study,we firstly found that pretreatment with tunicamycin(Tm)significantly inhibited platelet derived growth factor(PDGF)-BB-induced VSMC proliferation in a dose-dependent manner, which was confirmed by BrdU incorporation assay and morphology observation.Besides,we also firstly found pretreatment with Tm powerfully inhibited PDGF-BB-induced VSMC migration in a dose-dependent manner,which was proved by Wound healing experiment and Transwell assay.The proliferating cell nuclear antigen(PCNA)and matrix metalloproteinase(MMP)-2activations were down-regulated by Tm in PDGF-BB-induced VSMCs.Tm stimulated the expression of the antioxidant gene heme oxygenase-1(HO-1)both at the transcriptional and translational levels,while reducing phosphorylation and activation of mitogen-activated protein (MAP) kinases. The negative regulative effects of Tm were associated with a decrease in cyclins and cyclin-dependent kinases (CDKs) activation and an increase in p27expression. More importantly, HO-1siRNA partially abolished the beneficial effects of Tm on VSMCs. Furthermore, Tm inhibited inflammatory gene MCP-1, PAI-1and OPN mRNA expression but induced apoptotic gene expression in PDGF-BB-stimulated VSMCs.In conclusion, we provide evidence that pretreatment with the ER stress inducer, Tm, protects against PDGFBB-induced abnormal proliferation and migration of VSMCs. The beneficial effects of Tm are mediated at least dominantly, if not totally, by the induction of HO-1expression and the blockade of cell cycle reentry. Considering that the UPR is conserved among all eukaryotic cells and participates in the various cardiovascular diseases, our findings will further illuminate the potential involvement of ER stress in vascular health and pathology.