Desulfonation of a colitis inducer 2,4,6-trinitrobenzene sulfonic acid produces sulfite radical

2,4,6-Trinitrobenzene sulfonic acid (TNBS) has been used in vivo to induce colitis. With the nitroreductase of intestinal cells, TNBS underwent redox cycling to produce TNBS-nitro and superoxide radical anions which are thoug ht to be involved in initial oxidative reactions that lead to colonic injur y. In this study, we demonstrated that the TNBS desulfonative reaction with tissue amino acids produces sulfite which is subsequently oxidized to sulf ite radical. Sulfite radical was measured using a spin trapping methodology . Sulfite radical adducts of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or 5-d iethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were detected in a mixture of TNBS and lysine, xanthine oxidase, red blood cells, colonic muco sal or submucosal muscle tissues. TNBS alone did not produce sulfite radica l, indicating that its formation required the presence of amino acids. Beca use sulfite radical is the precursor of highly reactive sulfiteperoxyl and sulfate radicals, our data imply that these sulfite-derived free radicals m ay also contribute to oxidative reactions leading to colonic injury in TNBS -induced colitis. (C) 1999 Elsevier Science B.V. All rights reserved.