Effect Of Paraoxonase 2 On Oxidized Low-density Lipoprotein-induced Myocardial Cell Injury In Neonatal Rat

Atherosclerosis(AS)heart disease has always been the leading cause of human injury,disability and even death all the time.AS heart disease is called coronary heart disease(CHD)for short,and its pathogenesis is complicated.It is well known that endoplasmic reticulum stress(ERS)and oxidative stress(OS)are involved in it.The pathogenic role of oxidized low density lipoprotein(ox-LDL)in AS pathogenesis has become a consensus,and it has been shown that ox-LDL can cause the inflammation reaction,oxidative stress,cell damage and apoptosis of cultured cells.At present,the treatment of myocardial injury induced by ox-LDL is not ideal,and new clinical or animal studies are needed to fill this unfinished field.Paraoxonase(PON),a kind of antioxidant enzyme,PON2 is one of them,mainly distributed in the endoplasmic reticulum,which plays an antioxidant role in the endoplasmic reticulum.The study found that oxidative stress and ERS level of PON2 gene were significantly enhanced,while the overexpression of PON2 could significantly reduce the oxidative stress and ERS level of the cells in the macrophages of PON2 gene defection.At present,research on PON2 focuses on renal,central nervous and immune systems,and has not yet been systematically studied for cardiac cells.This study is aim to investigate the protective effect of PON2 and explore the underlying mechanism by detecting whether the high expression of PON2 can reduce the programmed death or apoptosis of myocardial cells induced by ox-LDL.Methods: The neonatal rat ventricular cells(NRVCs)were divided into the control cells,ox-LDL cells,Salubrinal + ox-LDL cells,PON2 + ox-LDL cells,Mn(III)TBAP + ox-LDL cells after the NRVCs were intervened with ox-LDL,or pretreated with SOD analogue Mn(III)TBAP,e IF2? dephosphorylation inhibitor Salubrinal and antioxidant enzyme PON2 polypeptide(n = 6).The cell viability was measured by MTT assay(n = 6).The cell apoptosis was detected with Caspase-3/7 activity detection kit.The protein expression levels of OS protein Nox2/gp91 phox,p47phox and ERS apoptotic protein caspase-12,e IF2?phox and PON2 were determined by western blotting(n = 4).Results:Compared with the control cells,exposure to ox-LDL resulted in significantly reduced cell viability(P < 0.01)and increased number of apoptotic cells(P < 0.01)in neonatal rat cardiac cells.Compared with cells exposed to ox-LDL alone,the cells pretreated with PON2,salubrinal or Mn(III)TBAP significantly increased viability(P < 0.01)and decreased number of apoptotic cells(P < 0.01).Compared with the control cells,exposure to ox-LDL markedly increased the expression of PON2 in the cardiac cells(P < 0.05),ERS-related proteins e IF2?phox(P < 0.01)and caspase-12(P < 0.01),and OS-related proteins Nox2/gp91phox(P < 0.01)and p47phox(P < 0.01);pretreatment of the cells with PON2 significantly decreased the protein expression of e IF2?phox(P < 0.01),caspase-12(P < 0.05),Nox2/gp91phox(P < 0.05),and p47phox(P < 0.05)and enhanced PON2 expression(P < 0.05);pretreatment with salubrinal significantly decreased the protein expressions of e IF2?phox(P < 0.05)and caspase-12(P < 0.01),Mn(III)TBAP significantly decreased the protein expressions of Nox2/gp91phox(P < 0.01)and p47phox(P < 0.01),and they both significantly increased the expression of PON2(P < 0.05).Conclusions: 1.PON2 could increase the myocardial cell viability induced by ox-LDL and inhibit the apoptosis induced by ox-LDL;2.PON2 reduces the injury of myocardial cell by inhibiting the oxidative stress response induced by ox-LDL through compensatory increasing;3.PON2 can reduce the damage of myocardial cell by inhibiting the endoplasmic reticulum stress response induced by ox-LDL through compensatory increasing.To sum up,PON2 may inhibit oxidative stress and endoplasmic reticulum stress response through compensatory elevations,thus playing a protective role in the programmed death or apoptosis of myocardial cells induced by ox-LDL.This result is expected to provide a new theoretical basis for the prevention and treatment of myocardial injury caused by ox-LDL.