The role of glucose in cellular defences against cytotoxicity of hydrogen peroxide in Chinese hamster ovary cells.

The presence of glucose in the cellular environment influences the response of cells to hydrogen peroxide. This study examines the effect of glucose on clonogenic cell survival of Chinese hamster ovary cells exposed to micromolar concentrations of exogenous hydrogen peroxide. Exposure to hydrogen peroxide (20 mumol/10(7) cells) resulted in considerable cytotoxicity that was unaffected by the presence or absence of glucose. However, glucose protected the cells from killing induced by milder exposure (1 mumol/10(7) cells) to the oxidant causing a shift in the dose-response curve. This effect was considered in terms of glucose metabolism via the pentose phosphate cycle. A low nontoxic concentration of hydrogen peroxide (0.1 mumol/10(7) cells) markedly increased pentose phosphate cycle activity in normal cells. Clonogenic survival and activity of the cycle for cells depleted of total glutathione to about 8.6% of its initial value and/or with catalase activity reduced to about 10% of control levels were also determined. Neither of these modifications alone completely abolished the protective effect of glucose. Efficacy of glucose protection against cytotoxicity of hydrogen peroxide diminished in cells depleted of glutathione, and this was not accompanied by any detectable increase in pentose phosphate cycle activity above the control level. Cells depleted of catalase alone had a profile of survival and pentose phosphate cycle activity similar to that of control cells when exposed to hydrogen peroxide. Cells depleted of both glutathione and catalase were almost as sensitive to hydrogen peroxide as the cells incubated without glucose. They also did not express any detectable increase in pentose phosphate cycle activity. Survival of those cells, when exposed to hydrogen peroxide, was almost the same regardless if glucose was present or not. These results demonstrate an important role for the glutathione redox cycle, catalase, and the pentose phosphate cycle in protection against hydrogen peroxide in Chinese hamster ovary cells. They confirm the essential role of glucose and pentose phosphate cycle activity for the detoxification of hydrogen peroxide via the glutathione redox cycle. The data suggest that the ability of catalase to metabolise peroxide may also depend on metabolism of glucose via the pentose phosphate cycle. A clear understanding of the protective mechanisms in cells against hydrogen peroxide has many applications since this common reactive oxygen species is implicated in several pathophysiologies and in the action of certain chemotherapeutic drugs.