The Role Of Transcription Coactivator P300 In Atrial Electrical Remodeling Induced By Aging

Aim:Atrial fibrillation（AF）is one of the most common arrhythmia in the clinic,which contributes to thromboembolism and heart failure,leading to death and disability in patients.The incidence of AF increases with age,which is one of the independent risk factors for AF.The co-transcriptional activator p300,which also has acetyltransferase activity,plays an important role in the regulation of cell cycle,differentiation and apoptosis.Our previous studies have shown that p300 can participate in the pathogenesis of AF by regulating aging-related fibrosis,but whether p300 is involved in the occurrence of AF by regulating the electrical remodeling of atrial myocytes,there is no relevant report.Therefore,this study aim to explore whether p300 is involved in the electrical remodeling of aging-related atrial myocytes in the atrial tissues of AF patients,animal models of natural aging and atrial myocytes cultured in vitro,which ultimately leads to the occurrence of AF.Methods:1.Collect the left atrial appendage tissues of sinus rhythm（SR）patients and AF patients,and divided them into two group according to age:18-50 years old group,>50years old group;western blot was used to detect the expression of p300,p53,p21,p16 and Cav1.2 protein in the left atrial appendage of AF and SR patients;whole-cell patch clamp was used to detect the I_Ca,L current density of atrial myocytes isolated from patients with SR and AF.2.C57BL/6 mice were reared to the age of 5,13,and 18 months to establish a natural aging model,and AF was induced by rapid atrial pacing in vivo to observe the inducible rate of AF.Western blot was used to detect the expression of p300,p53,p21,p16 and Cav1.2protein expressions in left atrial appendages of mice in different month-old groups;whole-cell patch clamp was used to detect I_Ca,L and APD of atrial myocyte isolated from 5-month-old and18-month-old mice;mice were given different doses of curcumin（50mg/kg/d,100 mg/kg/d）intervention for 6 months,starting from 12 months of age;Atrial rapid pacing was used to observe the inducible rate of AF;the left atrial appendage tissue was collected,and western blot was used to observe the differences in p300 and above protein;whole-cell patch clamp was used to detect I_Ca,L and APD.3.Different doses of tert-butyl hydrogen peroxide（Tert-Butyl hydroperoxide,TBHP）was used to incubate atrial muscle cell lines（HL-1 cells）to establish a cell senescence model,and different doses of curcumin were used to pretreat HL-1cells.The senescence of cells was determined byβ-gal.Western blot was used to detect the protein level of p300 protein,senescence-related proteins p53,Ac-p53,p21 and L-type calcium channel protein Cav1.2.Results:1.Compared with young SR patients,the expression of p300 protein,aging-related proteins p53,p21,and p16 in the left atrial appendage tissue of AF,especially in elderly AF patients,was significantly increased,and the expression of calcium channel protein Cav1.2 was significantly reduced;and compared with SR patients,the current density of ICa,L in the atrial myocytes of AF patients was significantly reduced;2.Compared with5-month-old mice,the expression of p300 protein,aging-related proteins p53,p21,and p16 in the left atrial appendage tissue of 13-month-old and 18-month-old mice was increased,while the expression of calcium channel protein Cav1.2 was significantly reduced;meanwhile,the patch clamp results showed that the I_Ca,L current density of atrial myocytes in 18-month-old mice was significantly reduced and APD was shortened.The expression of p300 protein,aging-related proteins p53,p21,p16 was decreased in atrial appendage tissue of 18-month-old mice treated with different doses curcumin（50 mg/kg/d,100 mg/kg/d,6 months）,while Cav1.2 protein level was significantly increased.At the same time,the patch clamp results showed that I_Ca,L current density of atrial myocytes increased and APD was prolonged in intervention group;3.Oxidative stress（TBHP,600/800μmol/L）stimulation can induce the senescence of HL-1 cells.The protein expression of p300,Ac-p53 and p21 increased,and Cav1.2 protein expression decreased.Pretreatment with curcumin can delay its senescence,inhibit the expression of p300 and p53/p21 proteins in atrial myocytes induced by hydrogen peroxide,and increase the expression of Cav1.2 protein.Conclusion:Co-transcription activator and acetyltransferase p300 may be involved in the aging-related electrical remodeling of atrial myocytes,promoting aging-related electrical remodeling of the atrium,and ultimately leading to the occurrence of AF.