Sodium Selenite Inhibit Xanthine/Xanthine Oxidoreductase-Induced Osteoblastic Differentiation Of Vascular Smooth Muscle Cells And The Signal Mechanism

The direct result of osteoblast differentiation of Vascular smooth muscle cells（VSMCs）is forming vascular calcification, it is a key risk factors in the pathogenesis of thecardioascular disease. A large number of studies have shown that reactive oxygen species（ROS） promote VSMCs osteoblast differentiation through a variety of molecularmechanism,but the most important biological function of trace element selenium isanoxidation.We established Vascular calcification model in vitro,and explained therelationship among selenium, O₂^-·,osteoblast differentiation of calcifying VSMCs and therelated mechanism, and produced O₂^-· through the xanthine/xanthine oxidase system（XXO）.First of all, the result of RT-PCR indicated that selenite suppressed XXO significantup-regulated mRNA expression Runx2,a key transcription factor for osteoblasticdifferentiation; XXO-induced osteoblastic differentiation of VSMCs, our research providedgood evidences,such as XXO increase alkaline phosphatase activity, up-regulated calciumdeposition,which are with dose dependence.These effects of XXO were suppressed bypretreatment of the cells with0.1μmol/L Na₂SeO₃for24h.Secondly,Western Blotsuggested XXO activated the phosphorylation of Akt,and inhibition of XXO-activatedPI3K/Akt signaling by pretreatment of the cells with0.1μmol/L Na₂SeO₃for24h,MEKinhibitor PD98059（2μmol/L） for2h and PI3K inhibitor LY294002（25μmol/L） for30min.Atthe same time, the influence of two inhibitors on ALP activity and expression of Runx2andCol-I in calcifying VSMCs were confirmed,pretreatment by PD98059and LY294002inhibited the XXO enhanced ALP activity and Runx2and Col-I expression.FurthermoreXXO induced oxidative stress in calcifying VSMCs,as evidenced by the increase ofintracellular reactive oxygen species production and MDA content and the decrease of cellapoptosis rate, Selenite pretreatment can restrain oxidatie stress and cell apoptosis.Takentogether,these results suggested that suitable concentration of Na₂SeO₃might be involved ina series of Redox mechanism to suppressed XXO-enhanced oxidative stress, blockedMAPK and PI3K/Akt signaling pathway, and then suppressed XXO-induced VSMCs osteogenetic differentiation and calcification, which appears to show that selenium plays aprotective role against arterial calcification.