High Glucose Promotes Vascular Smooth Muscle Cell Proliferation By Upregulating Proto-oncogene Serine/threonine-protein Kinase Pim-1 Expression

BackgroundDiabetes(DM)is a group of chronic progressive metabolic disorders with persistent hyperglycemia as a biochemical characteristic.Chronic hyperglycemia can cause chronic damage to blood vessels,heart,kidney and other tissues.Vascular remodeling is a common pathological occurrence in diabetes mellitus that causes complications such as atherosclerosis,leading to enhanced patient morbidity and mortality.As a prominent component of the vascular wall,smooth muscle cells play a crucial role in the initiation and propagation of diabetic vascular complications including abnormal cell growth in the atherosclerotic arterial intimae.Proviral integration site for Moloney murine leukemia virus 1(Pim-1)has been documented to play a crucial role in cell proliferation in certain vascular remodeling diseases,such as pulmonary arterial hypertension and neointima of balloon-injured arteries.However,its role in hyperglycemia and in high-glucose(HG)-mediated proliferation of vascular smooth muscle cells(VSMCs)is not clear to further identify new molecules involved in hyperglycemia/high-glucose(HG)-induced vascular smooth muscle cell(VSMC)proliferation,related signaling pathways warrant significant attention.Objective1.We would explore the role of abnormal expression of Pim-1 in the proliferation of vascular smooth muscle cells under high glucose conditions,and the STAT3/Pim-1 signal axis activated by high glucose whether promote the proliferation of vascular smooth muscle cells.2.Based on the potential value of Pim-1 gene target in the treatment of diabetic AS,whether Pim-1 specific inhibitor quercetagetin is effective in prevention and treatment of diabetes mellitus.MethodThis study is divided into two parts of the experiment.In vivo,a rat model of type 1 diabetes mellitus was established by injecting streptozotocin into the abdominal cavity and reducing the secretion of islet from SD rats.Immunohistochemistry,immunofluorescence and RT-PCR were used in the study.In vitro,cell proliferation,gene expression,protein expression and cell cycle were detected by CCK-8,cell count,RT-PCR,immunoblotting and flow cytometry.ResultHere we tested a role of Pim-1 in high-glucose(HG)-mediated vascular smooth muscle cell(VSMC)proliferation.Pim-1 and proliferating cell nuclear antigen(PCNA)expression levels in arterial samples from streptozotocin-induced hyperglycemia rats were increased,compared with their weak expression in normoglycemic groups.In cultured rat VSMCs,HG led to transient Pim-1 expression decline,followed by sustained expression increase at both transcriptional and translational levels.Immunoblot analysis demonstrated that HG increased the expression of the 33-kDa isoform of Pim-1,but at much less extent to its 44-kDa plasma membrane isoform.D-glucose at a concentration of 25 mmol/L showed highest activity in stimulating Pim-1 expression.Both Pim-1 inhibitor quercetagetin and STAT3 inhibitor stattic significantly attenuated HG-induced VSMC proliferation and arrested cell cycle progression at the G1 phase.Quercetagetin showed no effect on Pim-1 expression but decreased the phosphorylated-Bad(T112)/Bad ratio in HG-treated VSMCs.However,stattic decreased phosphorylated-STAT3(Y705)levels and caused transcriptional and translational down-regulation of Pim-1 in HG-treated VSMCs.Conclusion1.Our findings suggest both STZ-induced diabetes and HG-mediated Pim-1 expression contributes to VSMC proliferation,which may be partly due to the activation of STAT3/Pim-1 signaling.2.The Pim-1 inhibitor quercetagetin attenuated HG-induced VSMC proliferation by ffecting downstream gene expression.Therefore,the Pim-1 gene as a target that has potential value in the treatment of diabetic AS.