Vitamin B12 protects against superoxide-induced cell injury in human aortic endothelial cells

Abstract

Superoxide (O2•−) is implicated in inflammatory states including arteriosclerosis and ischemia–reperfusion injury. Cobalamin (Cbl) supplementation is beneficial for treating many inflammatory diseases and also provides protection in oxidative-stress-associated pathologies. Reduced Cbl reacts with O2•− at rates approaching that of superoxide dismutase (SOD), suggesting a plausible mechanism for its anti-inflammatory properties. Elevated homocysteine (Hcy) is an independent risk factor for cardiovascular disease and endothelial dysfunction. Hcy increases O2•− levels in human aortic endothelial cells (HAEC). Here, we explore the protective effects of Cbl in HAEC exposed to various O2•− sources, including increased Hcy levels. Hcy increased O2•− levels (1.6-fold) in HAEC, concomitant with a 20% reduction in cell viability and a 1.5-fold increase in apoptotic death. Pretreatment of HAEC with physiologically relevant concentrations of cyanocobalamin (CNCbl) (10–50nM) prevented Hcy-induced increases in O2•− and cell death. CNCbl inhibited both Hcy and rotenone-induced mitochondrial O2•− production. Similarly, HAEC challenged with paraquat showed a 1.5-fold increase in O2•− levels and a 30% decrease in cell viability, both of which were prevented with CNCbl pretreatment. CNCbl also attenuated elevated O2•− levels after exposure of cells to a Cu/Zn-SOD inhibitor. Our data suggest that Cbl acts as an efficient intracellular O2•− scavenger.