Involvement of peripheral polymorphonuclear leukocytes in oxidative stress and inflammation in type 2 diabetic patients

OBJECTIVE - To determine the extent to which peripheral polymorphonuclear leukocytes (PMNs) contributed to oxidative stress (OS) and inflammation in type 2 diabetic patients. RESEARCH DESIGN AND METHODS - PMNs and plasma were separated from blood withdrawn from 18 type 2 diabetic patients and 16 age- and sex-matched normal control subjects. The rate of superoxide release from phorbol 12-myristate 13-acetate (PMA)-stimulated PMNs and the plasma glutathione (GSH) levels served as measures of OS. Inflammation was assessed by PMN recruitment, expressed by peripheral blood PMN counts, and the in vitro survival of PMNs, which reflects cell necrosis. RESULTS - PMA-stimulated PMNs from diabetes released superoxide significantly faster, and plasma-reduced GSH was lower in diabetic patients than in normal control subjects. The rate of superoxide release from diabetic PMNs showed no correlation with the plasma glucose concentrations, whereas a positive linear correlation with HbA_lc was found. The in vitro survival of diabetic PMNs was lower than normal control PMNs when each was incubated in its own serum. The in vitro survival of normal control PMNs was reduced when incubated with diabetic serum, whereas normal control sera promoted the survival of diabetic PMNs. Peripheral PMN counts were higher in diabetic patients than in normal control patients. CONCLUSIONS - Type 2 diabetes is accompanied by a priming of PMNs, resulting in OS and increased self-necrosis. Necrosis starts a chain of inflammatory reactions that result in cell recruitment and in the long run, with OS, may result in endothelial dysfunction. Understanding the contribution of PMNs to OS and inflammation in diabetes may illuminate new mechanisms through which endothelial dysfunction evolves and causes angiopathy and atherosclerosis.