Effects And Intervention Of Desmosome Remodeling And Myocardial Fibrosis On Ventricular Arrhythmias Associated With β1-adrenergic Receptor Autoantibodies

Objective: To investigate the effects of desmosome remodeling and myocardial fibrosis on ventricular arrhythmias(VA)associated with β1-adrenergic receptor autoantibodies(β1ARAbs)in active immunization rabbit models.Methods: 18 New Zealand white rabbits(body weight 2.5～3.5kg)were randomly divided into 3 groups:β1ARAbs model group(β1ARAbs,n=6),intervention group(Meto,n=6),control group(Con,n=6).Multi point injection via back extracellular second cyclic peptide antigen peptide(2 mg each)of β1-adrenergic receptor to establish animal model.The blood of auricular vein was taken at 0,2,4,6 and 8 weeks,and the levels of antibody and cyclic adenosine monophosphate(c AMP)were determined by enzyme-linked immunosorbent assay,and β1-adrenergic receptor(β1-AR)was detected by Western blotting to verify the success of the model.At 8 weeks,heart rate,left ventricular ejection fraction(LVEF),VA burden and ventricular effective refractory period(VERP)were recorded and compared,electrical activity heterogeneity was compared,the structure and distribution of desmosome and gap junction were observed by transmission electron microscope,the degree of ventricular fibrosis was evaluated by Masson and Sirius scarlet pathological staining,and the levels of proteins related to ventricular fibrosis,gap junction and desmosome remodeling were detected by Western blotting.Results: 1)β1ARAbs levels at each time point: At 0week(baseline),there was no significant difference in β1ARAbs levels among Con group,β1ARAbs group and Meto group.From the second week,the levels of β1ARAbs inβ1ARAbs group increased gradually,which was significantly higher than that in Con group and Meto group,but there was no significant difference in β1ARAbs level between Con group and Meto group at each time point(P>0.05);2)c AMP and β1-AR levels: At 8 weeks,the level of c AMP [(61.78±3.00)ng/ml vs.(27.04±2.38)ng/ml vs.(29.39±1.59)ng/ml,all P<0.05] and the expression of β1-AR protein(1.11±0.08 vs.0.86±0.08 vs.0.74±0.03,all P<0.05)in β1ARAbs group were higher than those in Con group and Meto group;3)Heart rate and LVEF: At 8 weeks,compared with Con group and Meto group,average heart rate throughout the day in β1ARAbs group increased [(249.99±35.59)times/min vs.(238.63±48.08)times/min vs.(241.47±35.81)times/min,all P<0.05)],and LVEF levels decreased(55.97%±4.88% vs.76.44%±3.47% vs.70.58%±0.94%,all P<0.05);4)VA burden and VERP: Compared with Con group and Meto group,the frequency of ventricular tachycardia in β1ARAbs group increased [(397.67±88.01)times vs.(32.67±6.51)times vs.(96.33±14.29)times,all P<0.05],the duration of ventricular tachycardia prolonged[(164.13±18.69)s vs.(14.95±1.81)s vs.(57.61±9.13)s,all P<0.05],the induction rate of VA increased(75% vs.6% vs.8%,all P<0.05),and VERP shortened [(115.92±5.48)ms vs.(136.33±14.21)ms vs.(131.90±9.79)ms,all P<0.05];5)Electrical mapping: The electrical activity of ventricular tissue was stable,the conduction direction was clear,the conduction was uniform and orderly in Con group,the conduction direction was disordered and the conduction heterogeneity was increased in β1ARAbs group,and the conduction heterogeneity was improved in Meto group;6)Transmission electron microscope: The gap junctions and desmosomes were regularly distributed in Con group,the arrangement of gap junction and desmosome was disordered in β1ARAbs group,and improved in Meto group.Compared with Con group and Meto group,the intercalated disc compound area inβ1ARAbs group was denser.The length [(3.17±1.31)mm vs.(1.09±0.68)mm vs.(1.59±0.85)mm] and the thickness [(0.11±0.02)mm vs.(0.06±0.02)mm vs.(0.07±0.01)mm] increased(all P<0.05);7)Ventricular fibrosis: Pathological staining of Masson and Sirius scarlet and Western blotting(Collagen I,Collagen III and TGF-β1)showed that the degree of ventricular fibrosis in β1ARAbs group was more severe than that in Con group and Meto group(all P<0.05);8)Gap junction and desmosome protein levels: Compared with Con group and Meto group,the levels of Cx43,Cx40,DSC,DSG and DP in β1ARAbs group were significantly higher than those in β1ARAbs group(all P<0.05).Conclusion:Enhanced β1ARAbs levels could shorten VERP,increase the susceptibility and duration of VA,and aggravate ventricular electrical remodeling and structural remodeling by promoting desmosome remodeling and ventricular fibrosis,thus participating in the occurrence and maintenance of VA.Metoprolol could partially reverse the pathogenic effect of β1ARAbs.