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Evaluation of nitric oxide production by Leishmania infantum-infected dog macrophages
M A Panaro1, A Fasanella, S Lisi
1Istituto di Anatomia Umana Normale, Università di Bari, Italy.
Abstract:
Protozoa of the genus Leishmania (L.) infect reticuloendothelial cells of several mammalian species, including dogs, in which they often give rise to a chronic, not self-healing visceral disease. Since the parasitocidal mechanism of macrophages towards Leishmania in dog has not yet been well investigated, in this work we have evaluated in Leishmania 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 Salmonella typhimurium lipopolysaccharide (LPS), and in the same conditions, but in the presence of the NO synthase inhibitor L-N monomethylarginine (L-NMMA). In L. infantum-infected macrophages, nitric oxide production was observed at a concentration significantly higher after stimulation with both Con A-activated PBMC supernatants and LPS than that observed in uninfected cells cultured in medium alone, or infected cells unstimulated or stimulated by PBMC supernatants or LPS alone, respectively. Moreover, NO production was abolished in the presence of the NO synthase inhibitor L-NMMA. Finally, killing of Leishmania by macrophages was significantly reduced in the presence of L-NMMA.
Insights
This study investigated how dog macrophages kill Leishmania infantum. Macrophages produced nitric oxide (NO) when stimulated, which aided in parasite killing, but this was inhibited by L-N monomethylarginine (L-NMMA).
Area of Science:
- Immunology
- Parasitology
- Veterinary Medicine
Background:
- Leishmania (L.) protozoa cause chronic visceral disease in mammals, including dogs.
- The anti-Leishmania mechanisms of canine macrophages remain poorly understood.
- Leishmania infantum is a significant pathogen in canine visceral leishmaniasis.
Purpose of the Study:
- To evaluate the nitric oxide (NO) production and killing capacity of canine macrophages against Leishmania infantum.
- To investigate the role of NO in the macrophage-mediated killing of Leishmania in dogs.
Main Methods:
- Macrophage cultures from healthy dogs were infected with Leishmania infantum.
- Nitric oxide (NO) production was measured via nitrite (NO2) levels.
- Macrophages were stimulated with Concanavalin A (ConA)-activated PBMC supernatants and Salmonella typhimurium lipopolysaccharide (LPS).
- Experiments were conducted with and without the NO synthase inhibitor L-N monomethylarginine (L-NMMA).
Main Results:
- Leishmania infantum-infected macrophages showed significantly higher NO production upon stimulation with ConA-activated PBMC supernatants and LPS compared to controls.
- NO production was completely abolished in the presence of L-NMMA.
- Macrophage killing of Leishmania was significantly reduced when L-NMMA was present.
Conclusions:
- Canine macrophages produce nitric oxide (NO) in response to Leishmania infantum infection and stimulation.
- NO plays a crucial role in the macrophage-mediated killing of Leishmania in dogs.
- Targeting NO production could be a potential therapeutic strategy for canine leishmaniasis.