Study On Mechanisms Of Chronic Intermittent Hypoxia Inducing Cardiac Hypertrophy Of Rats And The Effect Of Drug Intervention

[Objective]Obstructive sleep apnea syndrome(OSAS)is usually associated with multiple cardiovascular disorders,including myocardial hypertrophy.Melatonin protects the heart from damaging conditions.However,whether melatonin alleviates heart damage induced by chronic intermittent hypoxia(CIH)is unknown.We are trying to confirm this speculate.[Method]In vivo,we divided the SD rats into four groups randomly:normoxia + saline(NOR + SAL),normoxia + melatonin(NOR + MEL),CIH + saline(CIH + SAL),CIH +melationin(CIH + MEL).The rats were treated with CIH or normoxia and received melatonin(10 mg/kg body weight)or the same dose of saline by daily intraperitoneal(ip)injection.This process was repeated for 8 h/day,7 days/week for a total of 6 weeks.In vitro,Cells were pretreated with melatonin(1 mM),compound C(CC,10 mL,),or 3-MA(10 mmol/L).Cells were then exposed to either normoxia(21%02 with 5%C02 balanced with N2)or CIH(repeated cycles of 21%02 for 25 min followed by 5%02 for 35 min).This CIH protocol was applied for 4 hours every three to four days.[Results]Melatonin significantly reversed the cardiac hypertrophy induced by CIH.Melatonin significantly enhanced AMPK and AMPK-autophagy induction under CIH.[Conclusion]Our results suggest that melatonin ameliorates cardiac hypertrophy caused by CIH by inducing autophagy via the AMPK pathway and by autophagy-regulated apoptosis.[Objective]Autophagy is tightly regulated to maintain cardiac homeostasis.Impaired autophagy is closely associated with pathological cardiac hypertrophy.However,the relationship between autophagy and cardiac hypertrophy induced by chronic intermittent hypoxia(CIH)is not known.[Methods]We measured the dynamic of cardiac autophagy by measuring the autophagy related genes by western blot and autophagosomes by transmission electron microscopy.And we verified the dynamic of autophagy by autophagy flux assay in present or absent of chloroquine(10 mg/kg).Then we detected the critical index of cardiac hypertrophy with impaired autophagy,such as serum ANP,HW/BW,ATP content,cell surface,fibrosis area,cardiomyocyte apoptosis and cleaved caspase-3 coupled with hemodynamic measurements.Then we verified the functional role of siRNA by western bolt and real time PCR.Silencing the ATG5 gene with specific ATG5 siRNA transfection in vivo can induces more significant cellular hypertrophic changing then CIH treatment alone and control siRNA transfection.We identified the autophagy regulating role of AMPK by autophagy flux assay in present or absent of chloroquine(10 mg/kg).Then we detected the function role of AMPK-autophagy in vitro.Finally,we revealed the mechanism of CIH impairing autophagy by measuring several critical factors in the pathway of AMPK-autophagy.[Results]CIH detected impaired cardiac autophagy by measuring critical index of autophagy which was further confirmed by autophagy flux assay.Impaired autophagy induces adverse cardiac hypertrophic pathological changings and cardiac dysfunction.Silencing of ATG 5 by siRNA transfection induced more significant cellular hypertrophic changings than CIH treatment alone and control siRNA transfection in vivo.CIH impairs cardiac autophagy through the AMPK pathway.Directly regulation of autophagy or indirectly regulation autophagy by AMPK-regulation can induces similar effects on cardiomyocyte hypertrophic changings.CIH impairs cardiac autophagy through the calcinurin-AMPK pathway in an Akt-and NFAT3-independent manner.[Conclusion]Collectively,these data demonstrated that impaired autophagy induced by CIH through the AMPK pathway contributed to cardiac hypertrophy.