Characterization of Glutathione Dithiophosphates as Long-Acting HS Donors.

Considering the important cytoprotective and signaling roles but relatively narrow therapeutic index of hydrogen sulfide (HS), advanced HS donors are required to achieve a therapeutic effect. In this study, we proposed glutathione dithiophosphates as new combination donors of HS and glutathione. The kinetics of HS formation in dithiophosphate solutions suggested a continuous HS release by the donors, which was higher for the dithiophosphate of reduced glutathione than oxidized glutathione. The compounds, unlike NaHS, inhibited the proliferation of C2C12 myoblasts at submillimolar concentrations due to an efficient increase in intracellular HS. The HS donors more profoundly affected reactive oxygen species and reduced glutathione levels in C2C12 myocytes, in which these parameters were elevated compared to myoblasts. Oxidized glutathione dithiophosphate as well as control donors exerted antioxidant action toward myocytes, whereas the effect of reduced glutathione dithiophosphate at (sub-)micromolar concentrations was rather modulating. This dithiophosphate showed an enhanced negative inotropic effect mediated by HS upon contraction of the atrial myocardium, furthermore, its activity was prolonged and reluctant for washing. These findings identify glutathione dithiophosphates as redox-modulating HS donors with long-acting profile, which are of interest for further pharmacological investigation.