Inducible nitric oxide synthase in rat neutrophils: role of insulin

Defective leukocyte-endothelial interactions are observed in experimental d iabetes mellitus. Endogenous substances, including nitric oxide (NO), have anti-inflammatory effects within the vasculature by reducing leukocyte adhe rence to post-capillary venules. The purpose of this study was to examine t he activity and expression of NO synthase in neutrophils from alloxan-induc ed diabetic rats. Glycogen-elicited peritoneal neutrophils were obtained fr om diabetic rats and matching controls 10, 30, and 180 days after alloxan ( 42 mg/kg, i.v.) or saline injection. NO synthase activity was determined by the [H-3]L-citrulline assay method. Expression of the enzyme was investiga ted by western blot analysis, Relative to controls, neutrophils obtained fr om diabetic rats presented a 2-fold increase in the activity of inducible N O synthase (iNOS), accompanied by an increase in the expression of the enzy me depicted by western blot. Treatment of diabetic animals with NPH insulin (2 IU/day, for 3 days) reduced both the activity and expression of iNOS to normal levels. Results presented suggest that overexpression of the induci ble isoform of NO synthase by neutrophils may be responsible, at least in p art, for the defects in leukocyte-endothelial interactions in diabetes mell itus, (C) 2001 Elsevier Science Inc. All rights reserved.