Exogenous H2S initiating Nrf2/GPx4/GSH pathway through promoting Syvn1-Keap1 interaction in diabetic hearts.

Excessive ROS accumulation contributes to cardiac injury in type 2 diabetes mellitus. Hydrogen sulfide (H2S) is a vital endogenous gasotransmitter to alleviate cardiac damage in diabetic cardiomyopathy (DCM). However, the underlying mechanisms remain unclear. In this study, we investigated the effects of NaHS administration in db/db mice via intraperitoneal injection for 20 weeks and the treatment of high glucose (HG), palmitate (PA) and NaHS in HL-1 cardiomyocytes for 48 h, respectively. H2S levels were decreased in hearts of db/db mice and HL-1 cardiomyocytes exposed to HG and PA, which were restored by NaHS. Exogenous H2S activated the nuclear factor erythroid 2-related factor 2 (Nrf2)/glutathione peroxidase 4 (GPx4)/glutathione (GSH) pathway, suppressed ferroptosis and mitigated mitochondrial apoptosis in db/db mice. However, these effects were abrogated after Nrf2 knockdown. NaHS treatment elevated the ubiquitination level of Kelch-like ECH-associated protein (Keap1) by preserving its E3 ligase synoviolin (Syvn1), resulting in Nrf2 nuclear translocation. H2S facilitated the sulfhydration of Syvn1-cys115 site, a post-translational modification. Transfecting Syvn1 C115A in cardiomyocytes exposed to HG and PA partially attenuated the effects of NaHS on Nrf2 and cell death. Our findings suggest that exogenous H2S regulates Nrf2/GPx4/GSH pathway by promoting the Syvn1-Keap1 interaction to reduce ferroptosis and mitochondrial apoptosis in DCM.