3,3'-diselenodipropionic acid, an efficient peroxyl radical scavenger and a GPx mimic, protects erythrocytes (RBCs) from AAPH-induced hemolysis

3,3'-Diselenodipropionic acid (DSePA), a derivative of selenocystine, has been synthesized and examined for antioxidant activity, glutathione peroxidase (GPx) activity, and cytotoxicity. The effect of DSePA on membrane lipid peroxidation, release of hemoglobin, and intracellular K+ ion as a consequence of erythrocyte (red blood cells or RBCs) oxidation by free radicals generated by 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) were used to evaluate the antioxidant ability. Lipid peroxidation, hemolysis, and K+ ion loss in RBCs were assessed, respectively, by formation of thiobarbituric acid reactive substances (TBARS), absorbance of hemoglobin at 532 nm and flame photometry. The IC50 values for lipid peroxidation, hemolysis, and K+ ion leakage were 45 +/- 5, 20 +/- 2, and 75 +/- 8,mu M, respectively. DSePA treatment prevented the depletion of glutathione (GSH) levels in RBCs from free-radical-induced stress. DSePA is a good peroxyl radical scavenger and the bimolecular rate constant for the reaction of DSePA with a model peroxyl radical, trichloromethyl peroxyl radical (CCl3O2*), was determined to be 2.7 x 10(8) M-1 s(-1) using a pulse radiolysis technique. DSePA shows GPx activity with higher substrate specificity towards peroxides than thiols. The cytotoxicity of DSePA was studied in lymphocytes and EL4 tumor cells and the results showed that DSePA is nontoxic to these cells at the concentrations employed. These results when compared with two well-known selenium compounds, sodium selenite and ebselen, indicated that DSePA, although it shows lesser GPx activity, has higher free radical scavenging ability and lesser toxicity.