Abstract Tu095: Cycloastragenol Alleviates Cardiac Fibrosis through Inhibiting Pyroptosis Activated by NLRP3 Inflammasome

Cardiac fibrosis is cardiac interstitial remodeling characterized by an enhanced extracellular matrix deposition. Acute sympathetic stress causes cardiac cells to immediately undergo pyroptosis, which induces cardiac inflammation and damage, and ultimately results in cardiac fibrosis. Our previous study has demonstrated the inhibitory effects of cycloastragenol (CAG), an active form of astragaloside IV isolated from Astragalus membranaceus, on isoproterenol (ISO)-induced cardiac fibrosis through blocking the NLRP3 signaling pathway. It is yet unknown how CAG affects pyroptosis of cardiac cells and whether its ability to prevent cardiac fibrosis coincides with this process. In this study, 5 mg/kg ISO was subcutaneously injected into wild-type (WT), NLRP3 knockout (KO), and GSDMD KO mice for 7 days to induce cardiac fibrosis. CAG (125 mg/kg/d) was administrated to the mice intragastrically at the start of the ISO injection. Primary cardiomyocytes and cardiac fibroblasts were isolated from neonatal rat hearts and treated with 10 μM ISO either with or without CAG. The results show that CAG alleviates cardiac fibrosis in WT mice, while lost this efficacy in NLRP3 KO mice. GSDMD KO mice do not develop ISO-induced cardiac fibrosis, indicating the key role of pyroptosis in cardiac fibrosis. Pyroptosis mainly occurs in mouse hearts during the initial stages of ISO induction (1 and 24 hours after ISO injection), and CAG significantly reduces pyroptosis of heart cells in WT mice, while CAG is unable to prevent pyroptosis in NLRP3 KO mouse hearts. The TGF-/Smads signaling pathway is also inhibited by CAG in WT mice but not in NLRP3 KO mice. Additionally, CAG prevents the in vitro pyroptosis of cardiomyocytes induced by ISO directly and cardiac fibroblasts caused by LPS+ATP. These results suggest that the principal mechanism of the anti-cardiac fibrosis effect of CAG mainly depends on its inhibition of pyroptosis mediated by NLRP3 inflammasome.