Evaluating the Effects of Imiquimod on Paths of TLRs and Inflammatory Cytokines Signaling in Infected Macrophages with Leishmania major in Vitro and in Vivo

Abstract

Background: Leishmania major is an obligate and intracellular pathogen and the macrophages are the cell hosts for L. major. Imiquimod stimulates macrophages to secrete different cytokines via the expression of TLRs.
Methods: This study was carried out in the Department of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, in 2018. The effect of imiquimod was investigated on non-infected and infected macrophages with L. major on the expression of Toll-like receptors (TLRs) and inflammatory cytokines. TLRs play an important role in enhancing the proceeding of phagocytosis and killing parasites. Moreover, the cytokines such as TNFα, IL6, and IL1, are often identified in inflammatory conditions as interfering targets in treatment. Healthy macrophages and macrophages infected with Leishmania major parasites were affected by different concentrations of imiquimod, after that the expression of TLR genes (TLR1, TLR2, TLR3, TLR4, TLR7 and TLR9) and cytokines were evaluated by real time RT-PCR. For experiments in laboratory animals, infected BALB/c mice were exposed to imiquimod and then isolated peritoneal macrophages.
Results: The expression of TLR2 decreased in non-infected macrophages were affected by the imiquimod. The expression level of TLR7 in healthy macrophages, decreased and the difference with control group was significant. Imiquimod increases the expression of inflammatory cytokines and IL12 in mouse macrophages and also decrease the expression of IL10.
Conclusion: This suggests that imiquimod may improve the therapeutic effects in infected mice with Leishmania major. Imiquimod causes that TLR2 decreased expression but TLR7 and TLR9 increased expression. Imiquimod as TLR7 agonist, enhance the recovery of leishmaniasis.