Small ubiquitin-related modifier (SUMO)ylation of SIRT1 mediates (-)-epicatechin inhibited- differentiation of cardiac fibroblasts into myofibroblasts

Context: (-)-Epicatechin (EPI) is a crucial substance involved in the protective effects of flavanol-rich foods. Previous studies have indicated EPI has a cardioprotective effect, but the molecular mechanisms in inhibition of cardiac fibrosis are unclear.

Objective: We evaluated the effect of EPI in preventing cardiac fibrosis and the underlying molecular mechanism related to the SIRT1-SUMO1/Akt/GSK3β pathway.

Materials and methods: Cardiac fibrosis mice model was established with transaortic constriction (TAC). Male C57BL/6 mice were randomly separated into 4 groups. Mice received 1 mg/kg/day of EPI or vehicle orally for 4 weeks. The acutely isolated cardiac fibroblasts were induced to myofibroblasts with 1 µM angiotensin II (Ang II). The cardiac function was measured with the ultrasonic instrument. Histological analysis of mice's hearts was determined with H&E or Masson method. The protein level of fibrosis markers, SUMOylation of SIRT1, and Akt/GSK3β pathway were quantified by immunofluorescence and western blot.

Results: EPI treatment (1 mg/kg/day) could reverse the TAC-induced decline in LVEF (TAC, 61.28% ± 1.33% vs. TAC + EPI, 74.00% ± 1.64%), LVFS (TAC, 28.16% ± 0.89% vs. TAC + EPI, 37.18% ± 1.29%). Meantime, we found that 10 µM EPI blocks Ang II-induced transformation of cardiac fibroblasts into myofibroblasts. The underlying mechanism of EPI-inhibited myofibroblasts transformation involves activation of SUMOylation of SIRT1 through SP1. Furthermore, SUMOylation of SIRT1 inhibited Ang II-induced fibrogenic effect via the Akt/GSK3β pathway.

Conclusion: EPI plays a protective effect on cardiac fibrosis by regulating the SUMO1-dependent modulation of SIRT1, which provides a theoretical basis for use in clinical therapies.