Reaction of Nitroxyl (HNO) with Hydrogen Sulfide and Hydropersulfides

Nitroxyl (HNO) has gained a considerable amount of attention because of its promising pharmacological effects. The biochemical mechanisms of HNO activity are associated with the modification of regulatory thiol proteins. Recently, several studies have suggested that hydropersulfides (RSSH), presumed signaling products of hydrogen sulfide (H₂S)-mediated thiol (RSH) modification, are additional potential targets of HNO. However, the interaction of HNO with reactive sulfur species beyond thiols remains relatively unexplored. Herein, we present characterization of HNO reactivity with H₂S and RSSH. The reaction of H₂S with HNO leads to the formation of hydrogen polysulfides and sulfur (S₈), suggesting a potential role in sulfane sulfur homeostasis. Furthermore, we show that hydropersulfides are more efficient traps for HNO than their thiol counterparts. The reaction of HNO with RSSH at varied stoichiometries has been examined with the observed production of various dialkylpolysulfides (RSSSR) and other nitrogen-containing dialkylpolysulfide species (RSS-NH-SR). We do not observe evidence of sulfenylsulfinamide (RS-S(O)-NH₂) formation, a pathway expected by analogy with the known reactivity of HNO with thiol.