The Role of Overproduction of Nitric Oxide in Apoptosis of BALB/C Mice Macrophages Infected with LeishmaniaMajor in Vitro

Abstract

Nitric oxide (NO) derived from activated macrophages has been shown to be crucial for the host's leishmanicidal activities. Excess NO, however, can in¬duce apoptosis in some cell types, including macrophages. In the present inves¬tigation, we studied the role of NO in inducing apoptosis of BALB/c mice mac¬rophages infected with Leishmania major in vitro. The peritoneal macrophages were harvested and cultured with or without L.major in the presence of a donat¬ing reagent (s-Nitroso-N-Acetylpenicillamine (SNAP)) or an inhibitor of NO synthase (NG -Methyl-L-Arginine (NMMA)). The concentration of NO in cul¬ture supernatants was measured after 18 hours incubation. Simultaneously, mac¬rophages undergoing apoptosis were identified by fluorescence and electron mi¬croscopy. The results showed an increase in apoptosis rate in parallel to nitrite production in macrophages cultured in the presence of SNAP. Although mac¬rophages infected with L.major had no significant increase in NO production, they showed a significant increase in apoptosis rate. Besides, macrophages cul¬tured with NMMA, had a decreased NO production but the apoptosis rate in¬creased. Therefore, mechanisms involved in apoptosis induction in the last two groups may be different from NO overproduction.