Efeito da quimiocina CXCL10 na infecção de macrófagos por Leishmania infantum in vitro

Abstract

Visceral leishmaniasis caused by Leishmania infantum is characterized by loss of the host's ability to generate an effective immune response. The chemokine CXCL10 is already showing promising results in the treatment against the parasite. This work aimed to evaluate the in vitro effect of CXCL10 and its association with Glucantime in macrophages infected by L. infantum. Macrophages RAW 264 were infected with L. infatum, and posteriorly were either treated or not with CXCL10 at the concentrations of 25, 50 and 100 ng/mL, Glucantime (16 mg/mL), LPS (20 ng/mL) and CXCL10+Glucantime [(25, 50 and 100 ng/mL) + (16 mg/mL)]. Parasite load in macrophages, nitric oxide concentrations and the cytokines IL-4 and IL-10 were assessed from the culture supernatants at both 24 and 48 hours after infection. The results showed that treatment with CXCL10 and CXCL10+Glucantime combined reduced significantly parasitic load, whereas the treatment with Glucantime alone presented reduction of only 50% of the infection when compared with control group. Twenty-four hours after infection, reduction of parasitic load varied between 64% and 74%, and 68% to 75% when treated with CXCL10 and CXCL10+Glucantime combined, respectively. Forty-eight hours after infection, reduction of parasitic load varied between 67% and 73%, and 72% to 78% when treated with CXCL10 and CXCL10+Glucantime combined, respectively. At the concentrations of 50 and 100 ng/mL of CXCL10, reduction of the parasitic load and increase of NO concentrations were simultaneously observed after 24 and 48 hours (p<0.001). Similar results were not found when CXCL10+Glucantime combined were used. Regarding inflammatory cytokines’ results, CXCL10 inhibited IL-10 secretion (p<0.001) after 24 and 48 hours. CXCL10 also inhibited IL-4 production, showing significant inhibition 24 hours after infection (p<0.001). Alike results were found in analysis of the supernatants obtained from 48 hours after infection regarding the reduction, although not significant. We conclude that in vitro treatment with CXCL10 induced increase in NO concentrations and reduced significantly parasitic load and induced low production of IL-10 e IL-4 on L. infantuminfected macrophages. CXCL10 association with Glucantime, although reduces intracellular parasite load in vitro, induces inhibition of NO production in a dose-dependent manner, suggesting that other mediators are involved in infection control.