Hydrogen Sulfide as a “Double-Faced” Compound

Hydrogen sulfide (H2S), like other gasotransmitters such as nitric oxide (NO•) and carbon monoxide (CO), acts as a signaling molecule in various biological systems. It may also regulate the oxidative stress observed in several diseases sometimes associated with changes of H2S concentration. This chapter describes the “double face” of hydrogen sulfide as both an antioxidant and a prooxidant in biological systems. One proposed mechanism by which H2S exerts its antioxidative effects is its ability to modulate the concentration of glutathione, which is a very important physiological antioxidant. This chapter discusses the interactions of H2S with various reactive oxygen species and reactive nitrogen species, including the superoxide radical anion (O2−•), hydrogen peroxide (H2O2), and peroxynitrite anion (ONOO−), which is produced in a rapid reaction between O2−• and NO•.