Nicotinamide "protects" resting lymphocytes exposed to hydrogen peroxide from necrosis but not from apoptosis

The aim of this work was to investigate the relationship between mechanisms of DNA repair and apoptosis induced by oxidative stress (H₂O₂) in human lymphocytes. Using the comet assay, fluorescent microscopy, and DNA electrophoresis, we studied the DNA damage induced by hydrogen peroxide (H₂O₂) treatment, the time and the amount of repair of strand breaks, the type of cell death, and the influence of inhibitors of repair (nicotinamide). When lymphocytes were treated with H₂O₂, we observed an increased in necrosis compared to apoptosis. However, when nicotinamide (which inhibits DNA repair) was added, the mode of death reversed to increased apoptosis. These results indicate that nicotinamide "protects" resting lymphocytes exposed to H₂O₂ from necrosis but not from apoptosis. This revised version was published online in July 2006 with corrections to the Cover Date.