Metabolic support of the respiratory burst in blood and sputum neutrophils of patients with community-acquired pneumonia

Abstract

The aim of the study was to investigate relationships between the respiratory burst in blood and sputum neutrophils and intracellular enzyme activity in patients with pneumonia. Methods. The study involved 82 patients with moderate to severe community-acquired pneumonia (CAP). The chemiluminescent assay was used to investigate synthesis of primary and secondary reactive oxygen species (ROS). The bioluminescent method was used to examine NAD(P)-dependent dehydrogenase activity in neutrophils. Results. Low-intensity respiratory burst in blood neutrophils and its predominant relations to the state of mitochondrial metabolism and malic enzyme activity were observed in healthy subjects. Blood neutrophils in patients with CAP were activated; the anaerobic respiration and mitochondrial metabolism increased in the cells. Additionally, intensity of the respiratory burst was related to terminal glycolysis reactions and the key reaction of the pentose phosphate cycle. Sputum neutrophils in patients with CAP were also activated. Conclusion. Abnormalities of metabolic support of the respiratory burst, such as decreased production of primary and secondary ROS, could appear under unfavorable conditions. Peroxidation increased in the cells, the intensity of terminal glycolysis reactions decreased, and substrates transferred from the citric acid cycle to amino acid exchange reactions. Under these conditions, malic enzyme remained the only substrate that stimulated the respiratory burst in sputum neutrophils, while substrate transfer from the tricarboxylic acid cycle inhibited synthesis of the secondary ROS.