The dual effects of nitrite on hemoglobin-dependent redox reactions

• Published in: Nitric oxide Vol. 40; pp. 1 - 9
• Main Authors: Lu, Naihao, Chen, Chao, He, Yingjie, Tian, Rong, Xiao, Qiang, Peng, Yi-Yuan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 31.08.2014
• Subjects: Anti-oxidant; Hemoglobin; Hemoglobins - metabolism; Hep G2 Cells; Humans; Nitrite; Nitrites - metabolism; Oxidation-Reduction; Oxidative/nitrative stress; Pro-oxidant; Tumor Cells, Cultured; DNPH; Anti-oxidant; DNP; Nitrite; MTT; MPO; BSA; Mb; 3-NT; Hemoglobin; Hb; Oxidative/nitrative stress; Pro-oxidant
• ISSN: 1089-8603; 1089-8611; 1089-8611
• DOI: 10.1016/j.niox.2014.04.010

•NO2− acted as a reducing agent to remove ferryl hemoglobin.•NO2− exerted pro-oxidant effect on Hb–H2O2-induced protein oxidation at lower concentrations.•NO2− effectively enhanced Hb–H2O2-induced loss of HepG2 cell viability.•NO2−-triggered tyrosine nitration may play an important role in enolase activation. Evidence to support the role of heme proteins-dependent reactions as major inducers of oxidative damage is increasingly present. Nitrite (NO2−) is one of the major end products of NO metabolism, and from the daily consumption. Although the biological significance of heme proteins/NO2−-mediated protein tyrosine nitration is a subject of great interest, the important roles of NO2− on heme proteins-dependent redox reactions have been greatly underestimated. In this study, we investigated the influence of NO2− on met-hemoglobin (Hb)-dependent oxidative and nitrative stress. It was found that NO2− effectively reduced cytotoxic ferryl intermediate back to ferric Hb in a biphasic kinetic reaction. However, the presence of NO2− surprisingly exerted pro-oxidant effect on Hb–H2O2-induced protein (bovine serum albumin, enolase) oxidation at low concentrations and enhanced the loss of HepG2 cell viability. In the reduction of ferryl Hb to ferric state, NO2− was decreased and oxidized to a nitrating agent NO2, Tyr12 and Tyr191 in enolase were subsequently nitrated. In contrast to the frequently inhibitive effect of nitrotyrosine, NO2−-triggered tyrosine nitration might play an important role in enolase activation. These data provided novel evidence that the dietary intake and potential therapeutic application of NO2− would possess anti- and pro-oxidant activities through interfering in hemoglobin-dependent redox reactions. Besides the classic role in protein tyrosine nitration, the dual effects on hemoglobin-triggered oxidative stress may provide new insights into the physiological and toxicological implications of NO2− with heme proteins.