The Effect Of Perk Pathway In Transformation Of Rats Aortic Smooth Muscle Cells To Osteoblast-like Cells Induced By High Glucose

Background: Vascular calcification decreases vessel elasticity, augments plaquebrittleness, leads to increased plaque rupture during angioplasty procedures,and isassociated with increased risk of myocardial infarction and death.Accumulatingevidence now points vascular calcification toward a tightly regulated process,with competition between factors promoting calcification and inhibitors ofmineralization, but the precise molecular and cellular mechanisms facilitatingectopic mineral deposition are unclear.The mechanisms of VSMCs differentiationinto osteoblast-like cells are not completely understood,the purpose of this studywas designed to reveal the effect of PERK pathway in transformation of smoothmuscle cells to osteoblastic cells induced by high glucose.Aims: To investigate the role of endoplasmic reticulum stress PERK pathwayin the transformation of SD rats aortic smooth muscle cells (VSMCs) toosteogenic cells by high glucose.Methods and Results: The primary cultured VSMCs from rats’ aorticsegments were divided into five groups, including normal control group (5mmol/lD-glucose), mannitol group(5mmol/L D-glucose plus25mmol/L mannitol), highglucose group (30mmol/L D-glucose), high glucose+PERK siRNA group(30mmol/L D-glucose plus PERK siRNA transfection), and high glucose+Scramble RNA group (30mmol/L D-glucose plus Scramble RNA transfection).And the cells were incubated for48h and72h respectively. The mRNA andprotein of the endoplasmic reticulum stress markers GRP78, PERK, p-PERK,eIF2α, p-eIF2α were identified by RT-PCR and Western-blot. The osteogeniccells characteristics markers Cbfα-1, Osteocalcin, and activity of alkalinephosphatase (ALP) and smooth muscle cells markers α-SMA were alsoidentified..When compared with the normal group and mannitol group, the high glucosegroup and high glucose+Scramble RNA group showed that the mRNA of Cbfα -1、PERK and eIF2α increased significantly (p<0.05), however the mRNAexpression were decreased after PERK siRNA transfection. The proteinexpression level of Cbfα-1,PERK, p-PERK, eIF2α, p-eIF2α,ATF-4and ALPactivity were increased the high glucose group and high glucose+Scramble RNAgroup (p<0.05), however decreased after PERK siRNA transfection(p<0.05).Conclusion: Endoplasmic reticulum stress PERK pathway may play a role in thetransformation of VSMCs from the contractile phenotype to the osteoblastphenotype induced by high glucose, and the transformation process can partiallyblocked by suppressing the PERK pathway.