Avaliação da imunomodulação de macrófagos murinos de perfil M1 e M2 por Leishmania infantum in vitro

Abstract

Visceral leishmaniasis is an infectious parasitic disease caused by protozoa of the genus Leishmania, transmitted by the bite of infected phlebotomine sand flies, and considered a severepublic health problem by the World Health Organization. In Brazil, the visceral form of the disease is caused by Leishmania infantum, with the domestic dog acting as the main vertebratehost, while humans act as accidental hosts. Macrophages are the main host cells for the parasite and play a dual role in the infection, acting simultaneously as effector cells and as anintracellular replication niche, depending on their polarization profile. Therefore, this study aimed to investigate the impact of macrophage polarization into M0, M1 (pro-inflammatory),and M2 (anti-inflammatory) phenotypes on L. infantum infection in vitro, focusing on the immunomodulation mechanisms that influence the control and persistence of the parasite. Using murine J774 macrophages, which were polarized and subsequently infected with L. infantum (Li) promastigotes, the study evaluated the macrophages after 24 and 48 hours bymeasuring the infection rate, parasite load, nitric oxide (NO) production, and levels of the cytokines TNF-α, IL-4, and IL-10. The results demonstrated that M1+Li showed the lowest infection rate (24h = 20.17 ± 0.47 and 48h = 18.75 ± 0.75 infected macrophages/100 macrophages) and the lowest parasite load (24h = 106.7 ± 1.38 and 48h = 116.5 ± 0.80 amastigotes/100 macrophages). This was associated with the highest production of NO (21.95 ± 0.40 μmol/mL at 48h) and TNF-α (73.41 ± 4.15 pg/mL at 48h), indicating the efficacy of thepro-inflammatory profile in controlling the parasite. In contrast, M2+Li were more susceptible to infection, showing higher infection rates (24h = 33.71 ± 0.56 and 48h = 37.86 ± 0.95 infected macrophages/100 macrophages) and parasite loads (24h = 133.5 ± 1.30 and 48h = 141.2 ± 1.04 amastigotes/100 macrophages), alongside elevated levels of IL-10 (24h = 17.74 ± 0.90 and 48h = 22.25 ± 1.31 pg/mL) and IL-4 (24h = 13.15 ± 0.97 and 48h = 15.83 ± 1.08 pg/mL). These data therefore suggest that L. infantum can modulate the immune response of macrophages, favoring its persistence in microenvironments dominated by M2 macrophages. The study highlights the crucial importance of the M1/M2 axis in the immunopathogenesis of visceral leishmaniasis, suggesting that macrophage modulation may be a promising strategy for the development of new therapeutic approaches.