Vitamin B12 does not increase cell viability after hydrogen peroxide induced damage in mouse kidney proximal tubular cells and brain endothelial cells

Abstract

Vitamin B12 (B12) is an essential co-factor for two enzymes in mammalian metabolism and can also act as a mimetic of superoxide dismutase (SOD) converting superoxide (O₂ ^•−) to hydrogen peroxide (H₂O₂). High oral dose B12 decreases renal O₂ ^•− and post-ischemia/reperfusion injury in mice and protects against damage induced by hypoxia/reperfusion in mouse kidney proximal tubular cells (BU.MPT). O₂ ^•− is unstable and rapidly converted to H₂O₂. H₂O₂ mediates oxidative stress associated with O₂ ^•−. Whether B12 protects against damage induced by H₂O₂ is unknown. Both BU.MPT cells and mouse brain endothelial cells (bEdn.3) were applied to test the effects of B12 on H₂O₂-induced cytotoxicity. Both types of cells were treated with different doses of H₂O₂ with or without different doses of B12. Cell viability was analyzed 24 h later. H₂O₂ caused cell death only at a very high dose, and high pharmacological dose of B12 did not prevent this detrimental effect in either cell type. In bEnd.3 cells, transcriptional levels of heme oxygenase-1 (HO-1) increased, while nuclear factor erythroid 2-related factor 2 (Nrf2) decreased by H₂O₂. The levels of transcripts were not affected by the B12 treatment. We conclude that the cytotoxic effects of exogenous H₂O₂ in BU.MPT and bEdn.3 cells are not prevented by B12.