EVALUATION OF NITRIC-OXIDE PRODUCTION BY LEISHMANIA INFANTUM-INFECTEDDOG MACROPHAGES

Protozoa of the genus Leishmania (L.) infect reticuloendothelial cells of several mammalian species, including dogs, in which they often giv e rise to a chronic, not self-healing visceral disease. Since the para sitocidal mechanism of macrophages towards Leishmania in dog has not y et been well investigated, in this work we have evaluated in Leishmani a infantum-infected macrophage cultures from 10 healthy dogs, killing capacity and nitric oxide (NO) production, in terms of nitrite (NO2-) levels. Parallel experiments were performed on macrophages stimulated with both Concanavalin A (ConA)-activated PBMC supernatants and Salmon ella typhimurium lipopolysaccharide (LPS), and in the same conditions, but in the presence of the NO synthase inhibitor L-N monomethylargini ne (L-NMMA). In L. infantum-infected macrophages, nitric oxide product ion was observed at a concentration significantly higher after stimula tion with both Con A-activated PBMC supernatants and LPS than that obs erved in uninfected cells cultured in medium alone, or infected cells unstimulated or stimulated by PBMC supernatants or LPS alone, respecti vely. Moreover, NO production was abolished in the presence of the NO synthase inhibitor L-NMMA. Finally, killing of Leishmania by macrophag es was significantly reduced in the presence of L-NMMA.