Acid sphingomyelinase downregulation alleviates diabetic myocardial fibrosis in mice

Increased activity of acid sphingomyelinase (ASMase) has been linked to diabetes and organ fibrosis. Nevertheless, the precise influence of ASMase on diabetic myocardial fibrosis and the corresponding molecular mechanisms remain elusive. In this study, we aim to elucidate whether ASMase contributes to diabetic myocardial fibrosis through the phosphorylation mediated by MAPK, thereby culminating in the development of diabetic cardiomyopathy (DCM). In vitro experiments utilized cardiac fibroblasts (CFs) isolated from wild-type mice (WT). For in vivo studies, ASMase knockout mice were generated through TALEN gene editing technology. Additionally, a diabetes mellitus model was established by intraperitoneal injection of Streptozotocin (STZ), involving both ASMase knockdown mice (ASMase^+/--STZ) and WT mice. CFs were subjected to incubation with amitriptyline (AMP) (2.5 μM), advanced glycation end products (AGEs), and small interfering RNA (siRNA) over a duration of 24 h. Experimental assessments encompassed EdU incorporation, transwell assays, and fluorescence staining, aimed at elucidating the functional characteristics of cardiac fibroblasts. The quantification of collagen I, phosphorylated MAPK levels within both cellular and murine cardiac contexts was accomplished through Western blot analysis. In the ASMase^±-STZ group, mice exhibited attenuated myocardial fibrosis and ameliorated cardiac diastolic function in comparison to the WT-STZ group. Furthermore, treatment of CFs with AMP and siRNA demonstrated a suppressive effect on the proliferation and fibrotic expression induced by AGEs in CFs. Our investigation unveiled that ASMase modulates myocardial fibrosis through the TGF-β-Smad3 and MAPK pathways, elucidating the intricate molecular mechanisms underlying the observed effects. Our findings indicate that ASMase plays a vital role in myocardial fibrosis in DCM, providing a foundation for developing new therapeutic strategies for the prevention and control of DCM.