Toll-like receptors (TLR) trigger the innate inflammatory response by the recognition of molecular patterns from pathogens or cell damages. Its signaling pathway can be regulated by post-transcriptional control of gene expression via microRNAs (miRNAs). To evaluate the role of both mechanisms in the Leishmania amazonensis infection, we observed the modifications of signaling pathway of TLR and miRNA profile expression, comparing wild type (WT) macrophages (MØ) or knocked-out to encoding genes of TLR2, TLR4 and MyD88 (myeloid differentiation primary response 88). The absence of these genes increased infectivity of Leishmania amazonensis. Since the TLR pathway also influences in the L-arginine metabolism leading to nitric oxide (NO) production to kill parasite, via increase of Nitric Oxide Synthase 2 mRNA expression (Nos2), which was blocked in the absence of TLR2, TLR4 and MyD88. Also in MyD88-/--MØ was increased Cationic Amino Acid Transporters 1 and 2 mRNA amount, and TLR2-/--MØ increased the number of Arginase 1 transcripts, enzyme involved in polyamines production and parasite survival. Also, L. amazonensis infection of WT-MO modulated 32% of 84 miRNAs analyzed, being 50% up regulated; while MyD88-/-, TLR2-/- and TLR4-/- showed distinctly modulation of miRNAs. Indeed, we observed an increase in let-7e amount in L. amazonensis infection of WT-MØ that was reduced in the knockout mice strains. The let-7e functional inhibition impacted in the TLR pathway gene expression, involving recognition and adaptors molecules, as TLR9, MD-2, TIRAP and TRAF6, NF-kB signaling and immunomodulators, such as COX2, GM-CSF and NOS2, promoting a reduction in infectivity. In conclusion, TLR and miRNA impact in the macrophage response to L. amazonensis infection. Link to the article: Click here