Mechanism Of Hydrogen Sulfide In Improving Atrial Fibrillation Induced By Obstructive Sleep Apnea Based On Oxidative Stress

BackgroundAtrial fibrillation(atrial fibrillation,AF),as a common tachyarrhythmia with poor therapeutic effect and high disability and mortality in clinical,is becoming an clinical burden all around world.Obstructive sleep apnea(obstructivesleepapnea,OSA)is an independent risk factor for atrial fibrillation,which significantly aggravates the occurrence and development of atrial fibrillation.Previous studies have shown that oxidative stress is one of the important pathogenesis of atrial fibrillation induced by OSA.When the body is in a state of oxidative stress,a large number of reactive oxygen species are produced in the cells,resulting in myocardial remodeling,which in turn leads to myocardial fibrosis and thromboembolism.NADPH oxidase(NADPHoxidases,Noxs)is the main source of reactive oxygen species in cardiovascular system.Some studies have shown that the expression of Nox4 is significantly increased and the production of reactive oxygen species is enhanced in hypoxic cardiomyocytes.Therefore,regulating the expression activity of Nox4 in myocardium and reducing the production of reactive oxygen species can reduce myocardial oxidative stress injury,or provide a new breakthrough point for the treatment of OSA-induced atrial fibrillation.Hydrogen sulfide is a new type of gas signal molecule discovered after carbon monoxide and nitric oxide.In recent years,hydrogen sulfide plays a prominent role in the cardiovascular system,protecting cardiomyocytes through various mechanisms such as anti-inflammation,inhibition of oxidative stress and improvement of myocardial remodeling.However,the study of hydrogen sulfide in atrial fibrillation is still rare.In this study,we established a rat model of atrial fibrillation induced by acute obstructive sleep apnea and intervened with sodium hydrogen sulfide(an exogenous donor of hydrogen sulfide),to explore the possible mechanism of sodium hydrogen sulfide in improving OSA-induced atrial fibrillation from oxidative stress.The purpose of this study was to study the effects of hydrogen sulfide on atrial fibrillation,in order to develop new ideas for the treatment of atrial fibrillation.AimsThis study aims was to explore the mechanism of hydrogen sulfide in improving atrial fibrillation induced by obstructive sleep apnea.By establishing a rat model of atrial fibrillation induced by acute obstructive sleep apnea and intervening with sodium hydrogen sulfide as an exogenous donor of hydrogen sulfide.With exploring the oxidative stress activity,to clarify the possible mechanism of sodium hydrogen sulfide in improving atrial fibrillation induced by acute obstructive sleep apnea,in order to develop new ideas for the treatment of atrial fibrillation.Methods1.36 male SD rats aged 8-12 weeks were randomly divided into three groups: control group(Con group,n=12),model group(OSA group,n=12)and sodium hydrosulfide intervention group(Na HS group,n=12).2.Sodium hydrosulfide group was injected intraperitoneally with sodium hydrosulfide solution according to the body mass of each rat(0.9% Na Cl was used to resolved the solution to 48 μ mol/kg.Then the solution was injected at multiple time points.The drug was injected once at the beginning of the experiment,and then repeated every hour until the drug injection was completed).The control group and the model group were given intraperitoneal injection of normal saline at the same time point.3.All rats in each group were intubated under anesthesia.The OSA group and the Na HS group were treated with circulatory breath holding method to simulate the process of OSA(holding breath for 40 seconds,returning to normal ventilation for 5 minutes,20 minutes,6 minutes as a cycle,a total of60 cycles,lasting for 6 hours),and normal ventilation in the control group.The body surface electrocardiogram was continuously recorded with standard limb leads.When the electrode was implanted into the high right atrium in the right jugular vein of the rat,a clear large A wave and small V wave was displayed on the multi-channel electrophysiology instrument,indicating that the atrial electrode was implanted successfully.Programmed electrical stimulation was performed with an electrophysiological stimulator,which included eight continuous stimuli(S1-S1=120ms),followed by one extrasystole stimulation(S2-S2).The S1-S2 interval decreased gradually from the initial 100 ms to the amplitude of 5ms,and the electrophysiological instrument waveform was observed.When approaching the effective refractory period,it was changed to the amplitude of 2ms until the initial atrial effective refractory period was measured,and then the S1-S2 interval was changed to a shorter effective refractory period(5ms).The model group and sodium hydrosulfide group were treated with tracheal intubation for 40 seconds to simulate OSA.OSA immediately uses S1-S2 interval as the parameter of short 5ms,which is a more effective refractory period,and gives stimulation every 2 seconds until conduction response or atrial fibrillation waveform appears,and when the duration is more than 3 seconds,S1-S2 will continue to shorten 2ms,and again programmed stimulation.If atrial fibrillation waveform occurs,the state of atrial fibrillation will be terminated by itself and sinus rhythm will be restored.Programmed stimulation will be performed again and again until the end of one OSA.The final atrial effective refractory period was measured at the end of electrical stimulation.At the end of the experiment,blood and left atrial tissue were collected and the corresponding biochemical indexes were determined.4.The cardiac electrophysiological process was recorded,and the changes of atrial effective refractory period,induction rate of atrial fibrillation and duration of atrial fibrillation in each group were analyzed.5.The content of malondialdehyde(MDA)in serum was detected by thiobarbituric acid method,and the activity of superoxide dismutase(SOD)in serum was detected by xanthine oxidase method.6.The expression of NADPH oxidase 4(Nox4),gap junction protein 43(Cx43)and Collagen Ⅰ、 Fibronectin、 MMP2 in atrial tissue was detected by Western blotting method.7.The left atrial tissue was fixed and sectioned,and the structural changes of atrial myocytes were observed by hematoxylin-eosin(HE)staining,and the degree of fibrosis was observed by Masson staining.Results1.The rat model of atrial fibrillation induced by acute obstructive sleep apnea was successfully established.The rat model of acute OSA-induced atrial fibrillation was established,including control group(n=12),model group(n=12),sodium hydrosulfide group(n=12),control group showed sinus rhythm before and after electrophysiological stimulation,but atrial fibrillation was not induced in OSA model group and sodium hydrosulfide group.This shows that the circulation breath holding method is successful in the the model group and sodium hydrosulfide group2.Sodium hydrosulfide improved atrial fibrillation induced by obstructive sleep apneaCompared with the control group,the atrial effective refractory period in the model group was shortened,the induction rate and duration of atrial fibrillation were significantly increased and prolonged.Afer Na HS intervention,the atrial effective refractory period prolonged,the induction rate and duration of atrial fibrillation were significantly decreased.The difference was statistically significant(P<0.05).3.Sodium hydrosulfide inhibited Nox4 protein to improve oxidative stress injury of atrial fibrillation induced by obstructive sleep apnea.Compared with the control group,the model group had increased expression of Nox4 and malondialdehyde,decreased superoxide dismutase activity,and decreased expression of Cx43,increased expression of CollagenⅠ 、 Fibronectin 、 MMP2.After Na HS intervention,Nox4 expression was inhibited,malondialdehyde content was decreased,superoxide dismutase activity was increased,and Cx43 expression was increased,decreased expression of Collagen Ⅰ、Fibronectin、MMP2(P<0 05).4.observation and comparison of myocardial histomorphology in each group.The fixed sections of atrial tissue of rats in each group were stained with hematoxylin-eosin staining,the results showed that in the control group,the atrial myocytes were arranged closely and neatly,the structure of cardiomyocytes was complete,the nucleus was large and clear,In the model group,myocardial cells were disordered and nuclear pyknosis was observed;Symptoms were slightly relieved after intervention with sodium hydrosulfide.Masson staining showed that there was obvious collagen deposition in the tissue space of the model group compared with the control group,Symptoms were slightly relieved after intervention with sodium hydrosulfide.ConclusionsHydrogen sulfide reduce the oxidative stress injury of atrial fibrillation induced by obstructive sleep apnea,thus reducing the occurrence and duration of atrial fibrillation.The mechanism is closely related to the inhibiting of NADPH oxidase 4 protein activation,scavenging of oxygen free radicals,inhibiting of lipid peroxidation,and up-regulating of connexin 43 expression,improving myocardial fibrosis and effective inhibiting of atrial electrical remodeling and structural remodeling.