Secretion of IL-1 and H2O2 by human mononuclear cells in vitro

The secretion of hydrogen peroxide (H2O2) and interleukin-1α (IL-1α) was evaluated during in vitro culturing of human monocytes. The oxidative metabolism and cytokine secretion were correlated to the cell distribution (number of surface-associated cells), the DNA content and their integrity, evaluated by lactate dehydrogenase (LDH) assay. The differentiation of cultured monocytes was determined by the expression of CD14, 27E10 and RM3/1. After 24 h cultivation, unstimulated cells had a low production of H2O2 and IL-1α. A four-fold increase in the production of H2O2 was detected with 5 and 10 μg/ml of lipopolysaccharide (LPS) and polystyrene (PS) particles. PS particles induced a concentration-dependent increase in IL-1α after 24 h. In contrast, cultivation for 48 h, did not result in any measurable production of H2O2, irrespective of the type of stimulus. A decreased viability of monocytes was shown after stimulation with PS particles in high concentrations. Our results indicate that the phenotype expression, adhesion, integrity and secretory pattern of human monocytes is dependent on the culture time and the type and concentration of stimulus.