Hyperphosphorylation Of Cx43 At Serine 368 Correlates With Prolonged QRS Complex In Myocarditis

Objective:Clinical studies have found that most patients with myocarditis are accompanied by prolonged QRS complex(? 120ms),and prolonged QRS complex is an independent risk factor for mortality in heart diseases.In the present study,utilizing experimental autoimmune myocarditis(EAM)as a disease model,we explored the correlation of abnormal QRS complex and pS368Cx43 in the ventricular myocardium.Method:EAM was induced in Lewis rats with immunized with porcine cardiac myosin.We recorded the lead II ECG of rats in the time course of EAM to observe changes of QRS complex after immunization.Meantime,we used western blot and immunohistochemical technologies to evaluate the phosphorylation,pattern and distribution of Cx43.To further demonstrate the relationship between Cx43 and QRS complex,we perfused 18-?-Glycyrrhetic Acid(18-?GA)to disturb the Cx43 gap junctional communication in isolated hearts.Treatment H9C2 cells with EAM rats serum to assess the phosphorylation of Cx43 at serine 368 in the presence or absence of Ro-32-0432(PKC specific blocker)and SB203580(p38 MAPK specific blocker).Furthermore,we used fluorescent dye transfer assay to evaluate the gap junctional communication impaired by EAM serum or IL-1? in presence and absence of p38 MAPK inhibitor.Treatment EAM rats with PKC specific blocker or p38 MAPK specific blocker by intraperitoneal injection to evaluate the QRS complex.The phosphorylation and pattern of Cx43 were measured by western blot and immunohistochemical technologies.Results:In the present study,we showed that the prolongation of QRS duration is accompanied by elevated phosphorylation of connexin 43(Cx43)at serine 368(pS368Cx43)not at serine 262.In cultured cells,EAM rat serum and inflammatory cytokine IL-1? activated p38 MAPK to up-regulate pS368Cx43 and destroy cell-to-cell communication.In isolated hearts of normal rats,perfusion of IL-1? not only increased pS368Cx43 but also impaired cell-to-cell communication and prolonged QRS duration.Furthermore,blockade of p38 MAPK down-regulated pS368Cx43,improved cell-to-cell communication and reduced QRS duration in EAM.Meantime,blockade of PKC down-regulated pS368Cx43 and reduces the QRS duration.These findings suggest that up-regulation of pS368Cx43 by IL-1? via p38 MAPK not PKC pathway contributes to the prolongation of QRS duration and could be a therapeutic target for myocarditis-induced prolongation of QRS duration.Conclusion:In this study,our findings reveal that increased phosphorylation of Cx43 induced by IL-1? at serine 368 via PKC and p38 MAPK pathway correlates with changed QRS complex in myocarditis.