Effect of cobalt treatment on cell growth and mitochondrial DNA damage in HEK293 acutely exposed to hydrogen peroxide

Abstract

Severity of ischemia/reperfusion injury accompanied with generation of reactive oxygen species is reduced by hypoxic preconditioning, the precise mechanisms of which are not completely understood. Recently, several authors suggested the pathway via hypoxia-inducible factor-1α (HIF-1α). The activation reduced the number of ischemia-induced apoptotic cells through the suppression of apoptosis signaling of cytochrome c release. Reactive oxygen species cause not only apoptosis via cytochrome c, but also mitochondrial DNA (mtDNA) damage. In this study, we determined cell growth and mtDNA damage in HEK293 cells exposed to H2O2 as pretreated with cobalt to mimic hypoxic preconditioning. When cells were treated with 0.2~0.4 mM H2O2, cell growth was suppressed, and mtDNA was damaged dependent on H2O2 concentration. When 0.4 mM H2O2 was exposed to cells where HIF-1α was induced with 100 μM CoCl2, mtDNA damage was suppressed, and cell number 4 days after H2O2 exposure (15.7 % against no exposure) was significantly greater than that without cobalt treatment (3.7 %). These results suggest that cobalt-induced HIF-1α activity ameliorates suppression of cell growth through protecting mtDNA damage caused by H2O2.