Leishmania braziliensis resistente ao Glucantime modula a resposta de macrófagos de perfil M1 in vitro

Abstract

American Tegumentary Leishmaniasisis (ATL) is a disease with high incidence and significant impact on public health in Brazil, with Leishmania braziliensis being the primary etiological agent. Glucantime (meglumine antimoniate) is the drug used for treatment; however, in recent decades, the emergence of resistant strains has complicated treatment. Macrophages are the host cells for Leishmania and play a crucial role in the response against these parasites. Activation to inflammatory macrophages (M1) promotes parasite elimination, but little is known about the modulation of macrophage plasticity induced by a treatment-refractory L. braziliensis strain. The main objective of this study was to evaluate the response of macrophages polarized in vitro to M1 and M2 profiles upon infection with Leishmania braziliensis strains resistant (LbR) and susceptible (LbS) to meglumine antimoniate. J774 macrophages were polarized to M1 (LPS, 1 μg/ml) and M2 (IL-4, 1 μg/ml), then infected with LbR or LbS strains. Parasite load, cytokine production (M1 macrophages: TNF-α, IL-12; M2 macrophages: IL-4, IL-10), and nitric oxide (NO) production were evaluated at 24- and 48-hours post-infection. The results showed that M1 macrophages infected with LbR exhibited a higher parasite load than those infected with LbS at both time points. Regarding inflammatory mediators, infection with LbR induced lower levels of inflammatory cytokines (TNF-α and IL-12) and NO in M1 macrophages compared to LbS at both 24 and 48 hours. In contrast, LbR induced significant production of the anti-inflammatory cytokines IL-10 and IL-4 in M2 macrophages, while LbS did not induce significant cytokine production compared to LbR at the evaluated time points. These findings suggest that the LbR strain, refractory to meglumine antimoniate treatment, can modulate the production of inflammatory cytokines and NO in M1 macrophages, as well as regulatory cytokine production in M2 macrophages. This creates a less inflammatory intracellular environment, favoring the parasite’s survival and potentially prolonging the infection, making treatment and disease cure more challenging. These results open new perspectives for further studies to deepen the understanding of Leishmania resistance mechanisms to current treatments, which may contribute to the development of more effective therapies.