The role of astragaloside IV in extracellular matrix remodeling in fibrotic heart disease: Regulation of TRPM7-dependent macrophage function

Background: Astragaloside IV (ASG), the main active constituent of Astragalus membranaceus, exerts protective effects against several diseases associated with myocardial fibrosis, while no data suggest its role on macrophages in the process of myocardial fibrosis. This study aimed to investigate the regulatory effects of ASG on macrophages during extracellular matrix remodeling in fibrotic heart disease Methods and Results: Cardiac fibrosis of Sprague Dawley rats was induced by isoproterenol (5 mg/kg/day, s.c.) for 14 days, and ASG (10 mg/kg/day, 50 mg/kg/day, p.o.) treatment was administered from the 6th day of modeling. Histopathological changes and cytokines secretion by macrophages were observed. NIH-3T3 cells were incubated with the conditioned supernatant of the hypoxia model RAW 264.7 cells to investigate the involvement of macrophage-secreted cytokines. The results showed that cardiac fibrosis accompanied by infiltration of macrophages attenuated after ASG treatment. Importantly, ASG counteracted the activation of the miR-135a-TRPM7-TGF-β1/Smad3 pathway in primary macrophages and the increased levels of profibrotic cytokines in supernatants. In vitro, the conditioned medium secreted by RAW 264.7 macrophages stimulated the proliferation and differentiation of fibroblasts in a TRPM7-dependent manner. Moreover, patch-clamp data showed that ASG inhibited macrophage TRPM7 current in dose-dependent. Conclusions: Our results suggest that macrophages promote the proliferation and differentiation of cardiac fibroblasts and remodeling of the extracellular matrix through paracrine function. In addition, TRPM7 may play an important role in the regulation of paracrine cytokines in macrophages. ASG remodeling the extracellular matrix and attenuating cardiac fibrosis by regulating macrophage activation via the miR-135a-TRPM7-TGF-β/Smads pathway.