Oxidation of Hydrogen Sulfide to Polysulfide and Thiosulfate by a Carbon Nanozyme: Therapeutic Implications with an Emphasis on Down Syndrome.

Abstract

Hydrogen sulfide (H₂ S) is a noxious, potentially poisonous, but necessary gas produced from sulfur metabolism in humans. In Down Syndrome (DS), the production of H₂ S is elevated and associated with degraded mitochondrial function. Therefore, removing H₂ S from the body as a stable oxide could be an approach to reducing the deleterious effects of H₂ S in DS. In this report we describe the catalytic oxidation of hydrogen sulfide (H₂ S) to polysulfides (HS_2+n ^- ) and thiosulfate (S₂ O₃ ^2- ) by poly(ethylene glycol) hydrophilic carbon clusters (PEG-HCCs) and poly(ethylene glycol) oxidized activated charcoal (PEG-OACs), examples of oxidized carbon nanozymes (OCNs). We show that OCNs oxidize H₂ S to polysulfides and S₂ O₃ ^2- in a dose-dependent manner. The reaction is dependent on O₂ and the presence of quinone groups on the OCNs. In DS donor lymphocytes we found that OCNs increased polysulfide production, proliferation, and afforded protection against additional toxic levels of H₂ S compared to untreated DS lymphocytes. Finally, in Dp16 and Ts65DN murine models of DS, we found that OCNs restored osteoclast differentiation. This new action suggests potential facile translation into the clinic for conditions involving excess H₂ S exemplified by DS.