Induction of nitric oxide synthase in macrophages: inhibition by fructose-1,6-diphosphate

Intravenous fructose-1,6-diphosphate (FDP) is reported to reverse shock and improves survival in animals given systemic lipopolysaccharide (LPS), although the mechanism is incompletely understood. Since endotoxin-related shock is associated with increased nitric oxide (NO) production, LPS-stimulated macrophages were treated with FDP, and the NO metabolite, nitrite, was measured 24 h later. Treatment of LPS-stimulated macrophages with 1, 5, or 10 mM FDP caused a dose-dependent reduction in mRNA expression for inducible NO synthase by Northern analysis and decreased the micromolar concentrations of nitrite produced by 17, 42, and 68%, respectively. Neither fructose nor sodium phosphate had these effects in LPS-exposed macrophages. Electrophoretic mobility shift assays revealed that FDP did not inhibit LPS-mediated activation of nuclear factor kappa B. Viability analysis showed that the FDP effect was not caused by cytotoxicity. Overall, these results suggest that fructose-1,6-diphosphate, a glycolytic intermediate with potential clinical use, may mitigate the adverse effects of LPS by regulating the generation of NO.