Effects Of Inducuced Ampk Expression On Autophagy And Myocardial Fibrosis In Dogs With Paroxysmal Atrial Fibrillation

Objective: To observe the changes of autophagy level and myocardial fibrosis in atrial fibrillation(AF),and to further explore the possibility that AMP-dependent protein kinase may improve myocardial fibrosis by inhibiting autophagy.Methods: Twelve Beagle dogs were randomly divided into 4 groups: control group(sinus rhythm),atrial fibrillation group(AF),metformin(MET)+ atrial fibrillation group,vagus nerve stimulation(VNS)+ atrial fibrillation group(n =3 dogs / group).In the control group,sham operation was performed without pacing,and in AF group,the pericardium was cut under anesthesia,the self-made bipolar electrode was sutured at the right auricle and connected with a high frequency stimulator,and the right auricle was paced quickly for 24 hours at 10 V,40 Hz,75 ms,the model of paroxysmal atrial fibrillation was established。 MET+AF group was treated with MET(100 mg/kg,daily drinking water)for 7 days,followed by right atrial appendage rapid pacing for 24 hours.VNS+AF group: Beagle dogs were stimulated by VNS and right atrial appendage pacing for 24 hours.After the successful establishment of the model,the Beagle dogs were killed by air embolization and the left atrial samples were collected immediately after thoracotomy.The levels of AMPK,α smooth muscle actin(a-SMA),microtubule light chain associated protein 3(LC3),autophagy associated protein p62 and Beclin-1 were measured by Western Blotting.Intracellular p62,AMKP and Beclin-1 protein levels were detected by immunofluorescence.HE staining and Masson staining were used to observe the deposition of collagen fibers in the left atrium of Beagle dogs.Result: 1.Compared with the control group,the expression level of p62 protein in AF group decreased significantly,while the expression level of Beclin-1,LC-3I,LC-3II protein and LC-3II/LC-3I ratio increased significantly(P < 0 05).The results of fluorescence immunization showed that the fluorescence intensity of Beclin-1 was strong and the fluorescence intensity of p62 was weak in AF group.It is suggested that atrial fibrillation can increase the level of myocardial autophagy.2.Compared with the control group,AF significantly reduced the protein expression of p-AMPK,Treatment with MET and VNS could improve the decrease of p-AMPK induced by AF.3.Compared with AF group,the expression of Beclin-1 and LC3-II/LC3-I were decreased after MET and VNS treatment,and the expression of p62 was increased(P<0.05),suggesting that MET and VNS treatment can reduce AF-induced autophagy.4.The results of HE staining and Masson staining showed that compared with the control group,HE staining showed looser tissue and more collagen-like substances in AF group,and Masson staining showed more blue collagen fibers.Compared with AF group,HE staining in Met+AF group and VNS+AF group showed a closer arrangement of tissues,collagen-like substances decreased,Masson staining showed less blue collagen fibers.Western Blotting showed that the expression of a-SMA in AF group was significantly higher than control group(P < 0.05),and the expression level of a-SMA in Met+AF group and VNS+AF group was significantly lower than AF group(P < 0.05).It is suggested that atrial fibrillation can make myocardial fibrosis,and activation of AMPK can improve myocardial fibrosis caused by atrial fibrillation.Conclusion: 1.Atrial fibrillation can induce autophagy of cardiomyocytes and induce myocardial fibrosis.2.Induction of AMPK expression may improve myocardial fibrosis induced by atrial fibrillation by inhibiting autophagy of cardiomyocytes.Induction of AMPK expression may improve myocardial fibrosis induced by atrial fibrillation by inhibiting autophagy of cardiomyocytes.