[Effect of low intensity laser light in the red range on macrophage superoxide dismutase activity]

The effect of lipopolysaccharides (LPS) and low-power laser radiation on nitric oxide (NO) production and the activity of superoxide dismutase (SOD) in rat peritoneal exudate macrophages was investigated. It was found that LPS increased NO production and SOD activity in macrophages in a concentration-dependent manner. The maximal activity of SOD was more than 100 times greater than in the control and was achieved at an LPS concentration of less than 10 ng/ml. The maximal production of NO was more than 250% of the control and was achieved at an LPS concentration of 100 ng/ml. The presence of cycloheximide, a transcriptional synthesis inhibitor, in conditioned media almost completely abolished SOD activation and NO production. This implies that the LPS-induced increase in SOD activity and NO production were determined by the activation of de novo protein synthesis (SOD and inducible NO synthase). The irradiation of macrophages by red light resulted in a dose-dependent increase in NO production and SOD activity. The incubation of irradiated cells in the presence of 10 microM cycloheximide abolished the increase. The presence of antioxidants (mexidol and ascorbate) also significantly inhibited the laser-induced activity of macrophages. Thus, laser irradiation of cells in the red range activates the synthesis of SOD and inducible NO-synthase de novo due to photosensitized initiation of free radical reactions.