To Explore The Regulatory Effect Of CB1R/AMPK/PGC-1α Signaling Pathway On Heart And Cardiomyocytes Under Chronic Intermittent Hypoxia

Objective:Obstructive sleep apnea(OSA),as the most common sleep disorder,is one of the independent risk factors of cardiovascular disease,but the specific molecular mechanism and pathway are not clear.In this study,the effects of chronic intermittent hypoxia(CIH)on the mitochondria of mouse heart and H9C2 cardiomyocytes were observed in vivo and in vitro.At the same time,AM251 was used to block endogenous cannabinoid receptor 1(Endogenous cannabinoid receptor type 1 CB1R)and to explore CB1R/Adenosine5’-monophosphate-activated protein kinase(AMPK)/ peroxisome proliferator-activated receptor-γ coactivator-1α(PGC-1α),that is,the role of CB1R/AMPK/PGC-1α signal pathway in the above process.Methods:The CIH animal model and IH cell model were made in intermittent hypoxia chamber.The cardiac function of mice was measured by echocardiography,and the changes of heart tissue and ultrastructure were observed by HE staining and electron microscope.Apoptosis and reactive oxygen species were detected by flow cytometry.The membrane potential of mitochondria was detected by JC-1 staining and the changes of mitochondria in cardiomyocytes were observed by Mito Tracker staining.The expressions of CB1 R,AMPK and PGC-1α were detected by Westernblot,immunohistochemistry and cellular immunofluorescence.Results:The in vivo study showed that the ejection fraction and heart rate of 4W CIH group were higher than those of NC group,but there was no significant difference in heart morphology,mitochondrial synthesis and the expression of CB1 R,AMPK and PGC-1α.In 6W CIH group,the ejection fraction and heart rate increased,the expression of CB1 R increased,the expression of AMPK and PGC-1α decreased,and the heart tissue was damaged obviously.Targeted blocking of CB1 R could reduce the degree of cardiac injury in 6W CIH group,and the expression of AMPK and PGC-1α increased.The cell studies in vitro showed that there was no significant difference in apoptosis between H9C2 cells in 6h IH group and NC group.Reactive oxygen species increased slightly,membrane potential increased,mitochondria increased,and the expression of CB1 R,AMPK and PGC-1α increased.In 18 h IH group,apoptosis increased,reactive oxygen species significantly increased,membrane potential decreased,mitochondrial fragmentation increased,CB1 R expression increased,AMPK and PGC-1α expression decreased.After targeted blocking of CB1 R,the expression of AMPK and PGC-1αincreased,which could reduce the injury of H9C2 cardiomyocytes induced by 18 h IH.Conclusion:The results show that CB1 R has a negative regulatory effect on AMPK/PGC-1 α pathway.Short-term CIH can directly activate AMPK/PGC-1α pathway,promote mitochondrial synthesis in cardiomyocytes,and protect heart structure and function.Long-term CIH can significantly increase the expression of CB1 R and inhibit the expression of AMPK/PGC-1 α pathway,resulting in structural damage and synthesis disturbance of myocardial mitochondria,and further changes in cardiac structure and function.After targeted blocking of CB1 R,the expression of AMPK and PGC-1α increased,which could reduce the injury of heart and cardiomyocytes caused by CIH.