High glucose impairs superoxide production from isolated blood neutrophils

Abstract

Objective: Superoxide (02-), a key antimicrobial agent in phagocytes, is produced by the activity of NADPH oxidase. High glucose concentrations may, however, impair the production of O2- through inhibition of glucose-6-phosphate dehydrogenase (G6PD), which catalyzes the formation of NADPH. This study measured the acute effects of high glucose or the G6PD inhibitor dehydroepiandrosterone (DHEA) on the production of O2- from isolated human neutrophils. Design: Laboratory studies of short-term cultures of neutrophil granulocytes. Participants: Healthy subjects. Interventions: Neutrophils were isolated from peripheral blood and incubated for 1 h in Krebs-Ringer buffer containing 5, 10, or 25 mM glucose, 5 mM glucose with 0, 5, or 20 mM mannitol, or 5 mM glucose with 0, 1, 10, or 100 μM DHEA. O2- production was induced by N-formyl-methionyl-leucyl-phenylalanine and measured by the cytochrome c reduction assay. Potential scavenging of O2- by glucose, mannitol, or DHEA was assessed in a cell free system using the pyrogallol assay. Measurements and results: Incubation of neutrophils with glucose dose-dependently reduced O2- production, which was 50% decreased at 25 mM glucose. Also DHEA reduced the production of O2- dose-dependently, whereas production rates were unaffected by mannitol. Neither glucose, mannitol, nor DHEA scavenged O2-. Conclusions: High extracellular glucose concentrations acutely reduce O2- production from activated neutrophils possibly through inhibition of G6PD. If this occurs in vivo, microbial killing by neutrophils may be impaired during acute hyperglycemia, as observed after major surgery, trauma, or severe infection.