RESUMO
PURPOSE: This study evaluated the effects of chronic intermittent hypoxia (CIH) at different times on the mitochondria of mouse hearts and H9C2 cardiomyocytes to determine the role of the cannabinoid receptor 1 (CB1R)/adenosine 5'-monophosphate-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) signaling pathway. METHODS: Animal and cellular CIH models were prepared in an intermittent hypoxia chamber at different times. The cardiac function of mice was determined, and heart tissue and ultrastructural changes were observed. Apoptosis, reactive oxygen species (ROS), and mitochondrial membrane potential were detected, and MitoTracker™ staining was performed to observe cardiomyocyte mitochondria. Western blot, immunohistochemistry, and cellular immunofluorescence were also performed. RESULTS: In the short-term CIH group, increases in mouse ejection fraction (EF) and heart rate (HR); mitochondrial division; ROS and mitochondrial membrane potential; and the expression levels of CB1R, AMPK, and PGC-1α were observed in vivo and in vitro. In the long-term CIH group, the EF and HR increased, the myocardial injury and mitochondrial damage were more severe, mitochondrial synthesis decreased, the apoptosis percentage and ROS increased, mitochondrial fragmentation increased, membrane potential decreased, CB1R expression increased, and AMPK and PGC-1α expression levels decreased. Targeted blocking of CB1R can increase AMPK and PGC-1α, reduce damage attributed to long-term CIH in mouse hearts and H9C2 cells, and promote mitochondrial synthesis. CONCLUSION: Short-term CIH can directly activate the AMPK/PGC-1α pathway, promote mitochondrial synthesis in cardiomyocytes, and protect cardiac structure and function. Long-term CIH can increase CB1R expression and inhibit the AMPK/PGC-1α pathway, resulting in structural damage, the disturbance of myocardial mitochondria synthesis, and further alterations in the cardiac structure. After targeted blocking of CB1R, levels of AMPK and PGC-1α increased, alleviating damage to the heart and cardiomyocytes caused by long-term CIH.
