Participation of several agents such as the reducing equivalents, antioxidant enzymes and pathologies in reductive stress. Abbreviations: G6PD = glucose 6 phosphate dehydrogenase, NAD = nicotinamide adenine dinucleotide, NAD+ = nicotinamide adenine dinucleotide oxidized, NADH = nicotinamide adenine dinucleotide reduced, NADPH = nicotinamide adenine dinucleotide phosphate reduced, GSH = glutathione, GSSG = glutathione disulfide, PPP = pentose phosphate pathway, γ-glutamyl-cysteine synthase, GSHS = glutathione synthetase, GPx = Glutathione peroxidase, Trx = thioredoxin, Grd = glutaredoxin, TNFα = tumor necrosis factor alpha, NrF2 = erythroid related factor 2, IL6 = interleukin 6, ROS = reactive oxidative species, OS = oxidative stress, ER = endoplasmic reticulum, Se = selenium, Hsp = heat shock protein, GR = glutathione reductase.