Connexin 43 reduces susceptibility to sympathetic atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia reported in clinical practice. Connexin 43 (Cx43) is a member of the connexin protein family, which serves important roles in signal transduction in vivo. The aim of the present study was to investigate the role of Cx43 in the induction and maintenance of atrial fibrillation by using an animal model of sympathomimetic atrial fibrillation. Cx43 was successfully knocked down in the myocardium with gene‑specific small interfering (si)RNA via lentiviral infection. A total of 25 dogs were randomly and evenly divided into five groups: Normal (N), rapid atrial pacing (RAP), isoproterenol (ISO) + RAP, RAP + Cx43 siRNA and ISO + RAP + Cx43 siRNA. The mRNA and protein levels, as well as the distribution of Cx43 on the cell membrane, were gradually decreased in each group compared with the N group following treatment (P<0.05). The induction rate of the atrial effective refractory period was not significantly affected in the RAP and RAP + Cx43 siRNA groups, whereas it was significantly reduced in the ISO + RAP and ISO + RAP + Cx43 siRNA groups compared with the N group (P<0.05). The induction rate of AF was gradually increased in the RAP + Cx43 siRNA, ISO + RAP and ISO + RAP + Cx43 siRNA groups compared with the N group (P<0.05). The expression of nerve growth factor (NGF) and tyrosine hydroxylase (TH) was gradually increased in the ISO + RAP and ISO + RAP + Cx43 siRNA groups compared with their respective controls (RAP and RAP + Cx43 siRNA groups, respectively). However, no significant difference in the levels of NGF and TH was observed between the RAP, RAP + Cx43 siRNA, ISO + RAP and ISO + RAP + Cx43 siRNA groups. The mitochondrial morphology in each group was notably altered compared with the N group. The mitochondrial reactive oxygen species production and apoptotic index were gradually increased in each group compared with the N group (P<0.05). The results of the present study suggest that Cx43 reduces susceptibility to AF. Downregulation of Cx43 mediates the induction and maintenance of sympathetic AF.