Xanthine Oxidase Inhibitor Allopurinol Improves Oxidative Stress-Mediated Atrial Remodeling In Animal Models Of Diabetes

Objective:There are several mechanisms,including inflammation,oxidative stress and abnormal calcium homeostasis involved in the pathogenesis of atrial fibrillation.In diabetes mellitus（DM）,increased oxidative stress may be attributable to higher xanthine oxidase activity.In this study,we examined the relationship between oxidative stress and atrial electrical remodeling,structural remodeling,and calcium handling abnormalities,and the potential beneficial effects of the xanthine oxidase inhibitor allopurinol upon these pathological changes.Methods:Ninety rabbits were randomly and equally divided into 3 groups:control,DM,and allopurinol-treated DM group.Ninety rats were randomly and equally divided into 3 groups:control,DM,and allopurinol-treated DM group.Echocardiographic and hemodynamic assessments were performed in vivo.Serum and tissue markers of oxidative stress and atrial fibrosis,including the protein expression were examined.Atrial interstitial fibrosis was evaluated by Masson trichrome staining and HE stain.ICaL was measured from isolated left atrial cardiomyocytes using voltage-clamp techniques.Confocal microscopy was used to detect intracellular calcium transients.The Ca²⁺handling protein expression was analyzed by western blotting and immunohistochemistry.Mitochondrial-related proteins were analyzed as markers of mitochondrial function.The mouse atrial myocyte cell line HL-1 cells were cultured,and the cells were randomly divided into4 groups:control group,angiotensin II（Ang II）stimulation group,allopurinol pretreatment（10μM）+AngII stimulation group,allopurinol pretreatment（100μM）+AngII stimulation group.The oxidative stress levels of HL-1 cells in each group were determined by detecting the expression of ROS in HL-1 cells and the expression of MnSOD.The expression levels of CaMKII and p-CaMKII in each group were determined.Results:Compared with the control group,animals in DM group showed obvious left ventricular hypertrophy,increased atrial interstitial fibrosis（1.90%vs.6.83%in the control group and DM group respectively in rabbits and 2.17%vs.29.79%in the control group and DM group respectively in rats）,serum and tissue markers of oxidative stress and atrial fibrosis including XO,NO,MDA,Mn-SOD,NF-κB,TGF-β,p-p38,p-JNK,ERK and p-ERK.Prolonged interal atrial conduction time,increased atrial fibrillation inducibility（0.67%vs.9.11%in the control group and DM group respectively in rabbits and 26.7%vs.83.3%in the control group and DM group respectively in rats）,ICaL density,intracellular calcium transient as well as Ca2+handling protein expression,such as Cav1.2 and NCX,were found in DM group,suggesting that electrical remodeling may occur in diabetic atria.Furthermore,Immunohistochemistry and western blot showed the expression level of CaMKII and p-CaMKII were elevated in atrial tissues of diabetic animals.These abnormalities in atrial structural and electrical remodeling above were alleviated by allopurinol treatment.Conclusions:Allopurinol,via its antioxidant effects,reduces atrial electrical,structural,ion channel remodeling and mitochondrial synthesis abnormalities induced by DM-related oxidative stress.