Hydrogen Sulfide and Cellular Redox Homeostasis

Figure 1

The main ROS generation and elimination pathways. ROS (including , , , , and H₂O₂) may be generated by exogenous (like smoking, , air pollution, etc.) and endogenous (like mitochondria, catecholamine, NOX, etc.) stimulating factors. can further react with H₂O₂ to generate through the Haber-Weiss reaction in the presence of ferric irons (shown as solid line arrows). Excessive is eliminated by SOD by catalyzing the dismutation of to H₂O₂ and O₂. H₂O₂ can be further removed by the catalysis of CAT or GPx. The catalysis of GPx needs GSH as its cosubstrate and GSH is oxidized to GSSG. GSSG can be reduced to GSH again by GR utilizing NADPH. GSH can also react with oxygen free radical directly and form the thiyl radical () and later GSSG. Vitamin E and vitamin C may react with oxygen free radical and form less reactive radicals (shown as dotted line arrows). NADPH: nicotinamide-adenine dinucleotide phosphate; NOX: NADPH oxidase; XO: xanthine oxidase; SOD: superoxide dismutase; GSH: glutathione; GSSG: glutathione disulfide; GPx: glutathione peroxidase; GR: glutathione reductase.