High glucose impairs superoxide production from isolated blood neutrophils

Abstract

Objective

Superoxide (O₂ ⁻), 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.