Modified kinetics of generation of reactive species in peripheral blood of patients with type 2 diabetes

Abstract

Level of reactive species in blood is an important pathogenic factor in diabetes mellitus leading to dysfunctions of vascular endothelial and smooth muscle cells and coagulation system abnormality. A massive release of reactive species (respiratory burst), catalyzed by NADPH oxidase in blood phagocytes, is not well understood in diabetes. The work aimed to study kinetics of response to microbial particles in blood to specify changes in regulatory mechanisms of generation of reactive species in patients with type 2 diabetes. Production of reactive species in blood and isolated granulocytes was measured by luminol-dependent chemiluminescence. Respiratory burst was initiated by serum opsonized zymosan in blood samples and phorbol ester in cell samples. Kinetic parameters were calculated from experimental kinetic curves of chemiluminescence intensity. ROC curve analysis and mathematical modeling were used to reveal the most significant predictors and clarify specific mechanisms of NADPH oxidase activation. It was shown that kinetic parameters of response to opsonized zymosan (lag-time, response rate, amplitude, production of reactive species) were higher in blood of patients than controls. Amplitude and response rate were the most statistically significant predictors for distinguishing patients and controls at high glucose. It indicated NADPH oxidase activation was the target of hyperglycemia. Mathematical modeling showed hyperglycemia increased stability of NADPH oxidase complex, decreased synchronization of its assembling and elevated neutrophil capacity to phagocytosis in patients. Weak or no dependence of response kinetics on ionomycin concentration was shown in patients indicating changed Ca2+-dependent mechanism of NADPH oxidase activation. Hyperglycemia in type 2 diabetes causes disturbances in mechanisms of NADPH oxidase activation associated with both phagocytosis and the state of intracellular signaling systems, including Ca2+-dependent. We suggest that NADPH oxidase in blood granulocytes can be a promising target for clinical intervention improving management of diabetic complications associated with inflammation.