SOD1 is an essential H2S detoxifying enzyme.

Although hydrogen sulfide (H2S) is an endogenous signaling molecule with antioxidant properties, it is also cytotoxic by potently inhibiting cytochrome c oxidase and mitochondrial respiration. Paradoxically, the primary route of H2S detoxification is thought to occur inside the mitochondrial matrix via a series of relatively slow enzymatic reactions that are unlikely to compete with its rapid inhibition of cytochrome c oxidase. Therefore, alternative or complementary cellular mechanisms of H2S detoxification are predicted to exist. Here, superoxide dismutase [Cu-Zn] (SOD1) is shown to be an efficient H2S oxidase that has an essential role in limiting cytotoxicity from endogenous and exogenous sulfide. Decreased SOD1 expression resulted in increased sensitivity to H2S toxicity in yeast and human cells, while increased SOD1 expression enhanced tolerance to H2S. SOD1 rapidly converted H2S to sulfate under conditions of limiting sulfide; however, when sulfide was in molar excess, SOD1 catalyzed the formation of per- and polysulfides, which induce cellular thiol oxidation. Furthermore, in SOD1-deficient cells, elevated levels of reactive oxygen species catalyzed sulfide oxidation to per- and polysulfides. These data reveal that a fundamental function of SOD1 is to regulate H2S and related reactive sulfur species.

The use of B vitamins for cutaneous ulcerations mimicking pyoderma gangrenosum in patients with MTHFR polymorphism.

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) polymorphisms are associated with thrombophilia and vasculopathy that may result in cutaneous ulceration. Pyoderma gangrenosum (PG) is a clinical diagnosis that may be made following exclusion of alternate causes of ulceration, including vascular inflammatory or occlusive disease, infection, and malignant neoplasm. OBSERVATIONS: We describe 2 patients with MTHFR polymorphisms discovered during hypercoagulable evaluation for cutaneous ulcerations on the lower extremities. Both patients showed a rapid improvement following treatment with oral vitamin supplementation and local wound care. One patient developed several subsequent ulcers when he decided to discontinue his therapy, and following reinitiation of therapy, the new ulcerations healed. The treatment was tolerated well without any adverse effects. CONCLUSIONS: MTHFR polymorphisms should be part of a comprehensive laboratory evaluation during hypercoagulable workup. Vitamin supplementation with folic acid (B(9)), pyridoxine hydrochloride (B(6)), and cyanocobalamin (B(12)) may result in healing of cutaneous ulcerations in some patients with MTHFR mutations.