Glucose metabolism is accelerated by exposure to t-butylhydroperoxide during NADH consumption in human erythrocytes

Several mechanisms have been proposed to underlie the events that occur during oxidative damage in red blood cells (RBCs) exposed to reactive oxygen species. This work explores what happens when metabolites related to redox regulation in human RBCs are oxidized to form alkoxyl radical and peroxyl radical as a result of exposure to tert-buthylhydroperoxide (BHP). During exposure to BHP, the glutathione level and the ratio of NADPH to total nicotinamide adenine dinucleotide phosphate (NADPH plus NADP+) were significantly decreased. Although alteration in the concentration of monosaccharides metabolized in the pentose phosphate pathway (PPP) was not observed, exposing RBCs to BHP caused the formation of methemoglobin (metHb) and a significant decrease in NADH. Moreover, we detected a significant increase in one of the peaks during BHP exposure by using HPLC with dansyl hydrazine as a prelabel reagent. A complete enzymatic conversion procedure was used to identify the peak as pyruvate based on comparison with standards. These results suggest that the rapid recovery in the level of glutathione and the formation of metHb by BHP require NADPH and NADH consumption. Subsequently, glucose metabolism accelerates to reproduce NADPH and NADH, which results in pyruvate accumulation. Our findings indicate that the level of pyruvate markedly increases upon exposure to a radical-generating oxidant capable of forming metHb. Methemoglobin reductase requires NADH as a co-factor, and oxidized form (NHADP+) is reduced via the glycolytic reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase. Thus, the overall acceleration of glycolysis induced by BHP is strongly dependent on the NADH reproducing pathway. In addition, the decrease in NADH enhances the increase in pyruvate by inhibiting the conversion of pyruvate to lactate in the presence of lactate dehydrogenase.