The Mechanism Of The Senescence Of Diabetic Atrial Myocyte Increasing Susceptibility To Atrial Fibrillation

Objective:Diabetes mellitus is one of the common chronic diseases caused by significant accumulation of advanced glycation end products（AGEs）,one of its common complications is atrial fibrillation.Currently,the incidence of atrial fibrillation in patients with diabetes is 40%higher than that in patients with diabetes alone.Atrial electrical remodeling plays an important role in the occurrence and maintenance of atrial fibrillation,but its pathogenesis remains elusive.Aging is a major risk factor for diabetes,which could accelerate the process of aging.This study intends to investigate the role and mechanism of atrial myocyte senescence in the susceptibility to diabetic atrial fibrillation.Methods:（1）Intraperitoneal injection of 50 mg/kg STZ were adopted to establish type 1diabetic（T1DM）mice model,random blood glucose levels and body weight were monitored by Rocher-Glycimeter after 20 weeks.Pathological changes of atrial tissues were evaluated by HE and Masson staining of mice.（2）The expression levels of AGE,RAGE,Cav1.2,Kv1.5,Kv4.3,p16 and Rb proteins were detected by Western blot in atrial tissues of mice and HL-1cell.（3）Electrophysiological techniques were used to monitor the susceptibility of mice to atrial fibrillation.（4）HL-1 cell was treated with AGE to establish a diabetic cell injury model,and the DM cell model was treated with Anti-RAGE,the positive rate of cell senescence was detected by SA-β-Gal staining,and the characteristics of cell cycle distribution was analyzed via Flow cytometric.（5）The changes of action potential（AP）,L-type calcium channel(I_Ca,L),transient outward potassium channel(I_to)and ultra-rapidly delayed rectifying potassium channel(I_Kur)in single atrial myocytes of mice and HL-1 cells were recorded by whole-cell patch-clamp technique.（6）In DM cell model,si RNA interfered with p16 or Rb protein,the expression levels of ion channel proteins Cav1.2 and Kv1.5 were detected by Western blot.Results:（1）In T1DM mice,blood glucose level was significantly increased,while body weight was reduced（P<0.01）,atrial myocytes were disordered and the collagen and fibrosis were increased.The expression levels of AGE and RAGE proteins,p16 and Rb proteins in atrial tissues were increased,but the expression levels of ion channel proteins Cav1.2,Kv4.3 and Kv1.5 were significantly decreased（P<0.05）.（2）The incidence rate of atrial fibrillation（AFIR）was higher in diabetic mice,as well as longer mean duration of atrial fibrillation（MDAF）,P-wave duration（PWD）and sinus cycle length（SCL）（P<0.01）.（3）The action potential duration of atrial myocyte in T1DM mice were prolonged,and the current densities of I_Ca,L,I_to and I_Kurwere decreased significantly（P<0.05）.（4）In the DM cell model,the expression of p16 and Rb proteins were increased,the senescence cells were enhanced and cell cycle was arrested in G1 phase,meanwhile,the expression and function of Cav1.2 and Kv1.5 proteins were significantly decreased with prolonged action potential duration（APD）,Anti-RAGE treatment could reverse the above effects（P<0.05）.（5）In DM cell model,down-regulation of p16 or Rb protein could significantly increase the expression of Cav1.2 and Kv1.5 proteins（P<0.05）.Conclusion:The interaction between AGE and RAGE in diabetes can accelerate the senescence of atrial myocytes,and then increase the susceptibility to atrial fibrillation,which is related to the obvious up-regulation of p16 or Rb protein expression in atrial myocytes of diabetes mellitus,the acceleration of aging process,and the promotion of the down regulation of the expression of Cav1.2 and Kv1.5 proteins in ion channel.It is suggested that the senescence of diabetic atrial myocytes is involved in atrial electrical remodeling,leading to the occurrence of AF;p16/Rb senescence signaling pathway may be a potential target for the treatment of diabetic atrial fibrillation.