Arylsulfonothioates: Thiol-Activated Donors of Hydropersulfides which are Excreted to Maintain Cellular Redox Homeostasis or Retained to Counter Oxidative Stress

Abstract

Despite their biological significance, the study of hydropersulfides (RSSH) is often limited due to their inherent instability. Here, we introduce arylsulfonothioates as thiol-activated RSSH donors and provide insight into cellular reactive sulfur species homeostasis. These precursors persulfidate physiologically relevant thiols (RSH) to form the corresponding RSSH. Real-time monitoring of hydrogen sulfide (H₂S) generation via membrane inlet mass spectrometry (MIMS) was employed to follow RSSH production, revealing that electron-donating aryl substituents marginally slow RSSH release rates, whereas electron-withdrawing substituents slightly accelerate release. Furthermore, arylsulfonothioates with strong electron-withdrawing substituents offer superior protection against doxorubicin (DOX)-induced cardiotoxicity. Experiments using H9c2 cardiomyocytes affirmed the cell-permeability of arylsulfonothioates and their ability to increase intracellular RSSH levels and protein persulfidation levels. Notably, we observe the excretion of RSSH into the extracellular medium. Further investigations revealed the involvement of the cystine/glutamate antiporter SLC7A11, as cotreatment with its inhibitor, sulfasalazine, significantly reduce extracellular RSSH release. H9c2 cells exhibit tolerance to arylsulfonothioate 1g with an electron-withdrawing 4-cyano group at 1 mM; however, inhibition of the cystine antiporter results in a minor decrease in cell viability. Under oxidative stress conditions induced by DOX or hydrogen peroxide (H₂O₂), cotreatment with 1g diminishes the excretion of RSSH and confers cytoprotection against DOX or H₂O₂-mediated toxicity. Our findings show adaptive cellular responses to RSSH levels, demonstrating excretion under elevated conditions to maintain redox homeostasis and intracellular retention as a protective response during oxidative stress.