Manganese Porphyrin-Based SOD Mimetics Produce Polysulfides from Hydrogen Sulfide.

Manganese-centered porphyrins (MnPs), MnTE-2-PyP (MnTE), MnTnHex-2-PyP (MnTnHex), and MnTnBuOE-2-PyP (MnTnBuOE) have received considerable attention because of their ability to serve as superoxide dismutase (SOD) mimetics thereby producing hydrogen peroxide (HO), and oxidants of ascorbate and simple aminothiols or protein thiols. MnTE-2-PyP and MnTnBuOE-2-PyP are now in five Phase II clinical trials warranting further exploration of their rich redox-based biology. Previously, we reported that SOD is also a sulfide oxidase catalyzing the oxidation of hydrogen sulfide (HS) to hydrogen persulfide (HS) and longer-chain polysulfides (HS, = 3-7). We hypothesized that MnPs may have similar actions on sulfide metabolism. HS and polysulfides were monitored in fluorimetric assays with 7-azido-4-methylcoumarin (AzMC) and 3',6'-di(O-thiosalicyl)fluorescein (SSP4), respectively, and specific polysulfides were further identified by mass spectrometry. MnPs concentration-dependently consumed HS and produced HS and subsequently longer-chain polysulfides. This reaction appeared to be O-dependent. MnP absorbance spectra exhibited wavelength shifts in the Soret and Q bands characteristic of sulfide-mediated reduction of Mn. Taken together, our results suggest that MnPs can become efficacious activators of a variety of cytoprotective processes by acting as sulfide oxidation catalysts generating per/polysulfides.