Polysulfide-mediated sulfhydration of SIRT1 prevents diabetic nephropathy by suppressing phosphorylation and acetylation of p65 NF-κB and STAT3

Diabetic kidney disease is known as a major cause of chronic kidney disease and end stage renal disease. Polysulfides, a class of chemical agents with a chain of sulfur atoms, are found to confer renal protective effects in acute kidney injury. However, whether a polysulfide donor, sodium tetrasulfide (Na₂S₄), confers protective effects against diabetic nephropathy remains unclear. Our results showed that Na₂S₄ treatment ameliorated renal dysfunctional and histological damage in diabetic kidneys through inhibiting the overproduction of inflammation cytokine and reactive oxygen species (ROS), as well as attenuating renal fibrosis and renal cell apoptosis. Additionally, the upregulated phosphorylation and acetylation levels of p65 nuclear factor κB (p65 NF-κB) and signal transducer and activator of transcription 3 (STAT3) in diabetic nephropathy were abrogated by Na₂S₄ in a sirtuin-1 (SIRT1)-dependent manner. In renal tubular epithelial cells, Na₂S₄ directly sulfhydrated SIRT1 at two conserved CXXC domains (Cys371/374; Cys395/398), then induced dephosphorylation and deacetylation of its targeted proteins including p65 NF-κB and STAT3, thereby reducing high glucose (HG)-caused oxidative stress, cell apoptosis, inflammation response and epithelial-to-mesenchymal transition (EMT) progression. Most importantly, inactivation of SIRT1 by a specific inhibitor EX-527, small interfering RNA (siRNA), a de-sulfhydration reagent dithiothreitol (DTT), or mutation of Cys371/374 and Cys395/398 sites at SIRT1 abolished the protective effects of Na₂S₄ on diabetic kidney insulting. These results reveal that polysulfides may attenuate diabetic renal lesions via inactivation of p65 NF-κB and STAT3 phosphorylation/acetylation through sulfhydrating SIRT1.