Effect of miR-22 secreted by macrophage exosomes on cardiomyocyte autophagy under uremic toxin stimulation

AIM To investigate the effect of microRNA-22 (miR-22) secreted by macrophage exosomes on the autophagy of H9c2 cardiomyocytes under uremic toxin stimulation. METHODS The macrophage-derived exosomes stimulated by indoxyl sulfate (IS) were collected and co-cultured with H9c2 cells. The levels of miR-22 in the macrophages， macrophage-derived exosomes and H9c2 cells were detected by RT-qPCR. The viability of H9c2 cells was measured by CCK-8 assay. The expression of exosome surface marker protein CD63 and autophagy-related proteins LC3 and P62 was determined by Western blot. RESULTS Under IS stimulation, the expression of exosome surface marker protein CD63 in the macrophages was significantly higher than that in control group (P<0.05), and the levels of miR-22 in the macrophages and macrophage-derived exosomes were significantly increased (P<0.01). With the increase in macrophage exosome concentration, the viability of H9c2 cells was decreased gradually (P<0.05), and the stimulation of macrophage exosomes reduced P62 expression and promoted the conversion of LC3-I to LC3-II in a dose-dependent manner (P<0.05). Macrophage-derived exosomes increased the ratio of LC3-II to LC3-I but decreased P62 protein expression in the H9c2 cells transfected with miR-22 mimic compared with the cells transfected with corresponding negative control miRNAs (P<0.05). However, miR-22 inhibitor yielded contrasting results. CONCLUSION IS-stimulated macrophages increase expression of miR-22 in cardiomyocytes through exosomes, and promote autophagy of the cardiomyocytes.