Role And Molecular Mechanism Of PKC?/NF-?B Pathway In Diabetic Atrial Remodeling

Abstract Objective:The study is to investigate the role and mechanism of Protein kinase C disforms beta?PKC??in the development of atrial fibrillation in diabetes mellitus by establishing streptozotocin-induced diabetes mellitus model.Methods:One hundred twenty-eight adult wistar rats were randomly divided into four groups:control group,diabetes mellitus group,PKC?inhibitor group and diabetes mellitus+PKC?inhibitor group,8 rats in each group.The rats in CR-group and DMR-group were treated with PKC?inhibitor?Ruboxistaurin,RBX,LY333531?for 1mg·Kg·d for 8 weeks.LAD,LVEDD,LVESD and LVEF were measured by echocardiography;SBP,DBP,MBP,LVEDP were recorded by arterial pressure tube.The heart models of Langendorff perfused rats were established to measure the IACT,AVWCL,LAERP,RAERP and AERPD.The incidence of atrial fibrillation was recorded by burst stimulation in each group.The left atrial myocardial cell size was determined by HE staining and interstitial collagen volume fraction in LA myocardium was calculated by Masson staining.The protein levels of PKC?,p-PKC?,NF-?Bp65,p-I?B,P38MARK,TNF-?,TGF-?,Cav1.2 and NCX were measured by Western Blotting.I_Ca,L,I_Naa and I_too of atrial myocytes were recorded by whole cell patch clamp technique.Results:Compared with C-group,after 8 weeks'intervention in the DM-group the LAD increased[?5.35±0.56?mm vs?3.92±0.76?mm,P<0.05]and the difference of LAD increased[?2.11±0.47?mm vs?0.41±0.39?mm,P<0.05].IACT prolonged[?28.38±4.37?ms vs?24.50±2.73?ms,P<0.05],LAERP decreased[?62.63±1.85?ms vs?77.38±1.60?ms,P<0.05],RAERP decreased[?60.50±1.70?ms vs?77.38±1.51?ms,P<0.05],AERPD prolonged[?5.75±1.04?ms vs?3.50±0.93?ms,P<0.05].The incidence of atrial fibrillation increased?95/160 vs 10/160,P<0.05?.The left atrial myocardial cell size increased[?86.67±21.95??m² vs?42.75±18.36??m ²,P<0.05].The interstitial collagen volume fraction in LA myocardium increased?5.64%±0.96%vs3.00%±0.93%,P<0.05?.PKC?,p-PKC?,NF-?Bp65,p-I?B,P38MARK,TNF-?,TGF-?,Cav1.2 and NCX protein expression were upregulated in DM-group.The density of I_Ca,L current was increased[?5.57±1.31?pA/pF vs?3.94±1.40?pA/pF,P<0.05].ThedensityofI_Nawasdecreased[?89.68±11.56?pA/pFvs?125.97±9.36?pA/pF,P<0.05]and the density of I_too was also decreased[?30.53±14.85?pA/pF vs?53.20±18.55?pA/pF,P<0.05]in DM-group.Compared with DM-group,after 8 weeks'intervention in the DMR-group the LAD decreased[?4.18±0.45?mm vs?5.35±0.56?mm,P<0.05]and the difference of LAD decreased[?0.79±0.57?mm vs?2.11±0.47?mm,P<0.05].IACT shorted[?22.50±2.20?ms vs?28.38±4.37?ms,P<0.05],LAERP prolonged[?76.50±1.20?ms vs?62.63±1.85?ms,P<0.05],RAERP prolonged[?72.75±1.83?ms vs?60.50±1.70?ms,P<0.05],AERPD decreased[?3.38±1.92?ms vs?5.75±1.04?ms,P<0.05],and the rate of atrial fibrillation decreased?14/160 vs 95/160,P<0.05?.The left atrial myocardial cell size reduced[?48.36±16.85??m² vs?86.67±21.95??m²,P<0.05],and interstitial collagen volume fraction decreased?3.14%±0.80%vs 5.64%±0.96%,P<0.05?.RBX treatment led to atrial PKC?,p-PKC?,NF-?Bp65,p-I?B,P38MARK,TNF-?,TGF-?,Cav1.2 and NCX protein levels downregulate.The density of I_Ca,L current was decreased[?3.77±0.45?pA/pF vs?5.57±1.31?pA/pF].The density of I_Naa was increased[?113.94±22.83?pA/pF vs?89.68±11.56?pA/pF]and the density of I_too was also increased[?44.27±15.10?pA/pF vs?30.53±14.85?pA/pF]in DMR-group.There was no significant difference in hemodynamics between the four groups.Conclusion:PKC?/NF-?Bp65 is a pathway of diabetes-induced atrial fibrillation,and its downstream TNF-?,TGF-?expression is elevated,resulting in left atrial enlargement,disorganized arrangement of left atrial myocytes,and left atrial fibrosis leading to atrial structure.Electric remodeling was induced in diabetic rats with changes of ion channels in atrial myocytes,prolonged IACT,shortened AERP,and increased AERPD.Atrial structural remodeling and electrical remodeling caused by diabetes play a key role in the occurrence and maintenance of atrial fibrillation.In this study,RBX can significantly reduce the structural remodeling and electrical remodeling of the atria in diabetic rats,and reduce the incidence of atrial fibrillation.