Toll-Like Receptor and miRNA-let-7e Expression Alter the Inflammatory Response in Leishmania amazonensis-Infected Macrophages

Abstract

Parasite recognition by Toll-like receptors (TLRs) contributes to macrophage activation and subsequent control of Leishmania infection through the coordinated production of pro-inflammatory and microbicidal effector molecules. The modulation of microRNA (miRNA) expression by Leishmania infection potentially mediates the post-transcriptional regulation of the expression of genes involved in leishmanicidal activity. Here, the contribution of TLR signaling to the miRNA profile and gene expression was evaluated in Leishmania amazonensis-infected murine macrophages. The infectivity of L. amazonensis was higher in murine bone marrow-derived macrophages from mice knockout for myeloid differentiation factor 88 (MyD88−/−), TLR2 (TLR2−/−), or TLR4 (TLR4−/−) than wild type C57BL/6 (WT). L. amazonensis infection of WT macrophages modulated the expression of 32% of the miRNAs analyzed, while 50% were upregulated. The absence of MyD88, TLR2, and TLR4 altered the percentage of miRNAs modulated during L. amazonensis infection, including the downregulation of let-7e expression. Moreover, the absence of signals mediated by MyD88, TLR2, or TLR4 reduced nitric oxide synthase 2 (Nos2) mRNA expression during infection. Indeed, the inhibition of let-7e increased levels of the Nos2 mRNA and NOS2 (or iNOS) protein and nitric oxide (NO) production in L. amazonensis-infected macrophages (4–24 h). The absence of TLR2 and inhibition of let-7e increased the expression of the arginase 1 (Arg1) mRNA but did not alter the protein level during infection. However, higher levels of the L-arginine transporters Cat2B and Cat1 were detected in the absence of Myd88 signaling during infection but were not altered following let-7e inhibition. The inhibition of let-7e impacted the global expression of genes in the TLR pathway by upregulating the expression of recognition and adaptors molecules, such as Tlr6, Tlr9, Ly96, Tirap, Traf 6, Ticam1, Tollip, Casp8, Map3k1, Mapk8, Nfkbib, Nfkbil1, Ppara, Mapk8ip3, Hspd1, and Ube2n, as well as immunomodulators, such as Ptgs2/Cox2, Csf 2, Csf 3, Ifnb1, Il6ra, and Ilr1, impacting NOS2 expression, NO production and parasite infectiveness. In conclusion, L. amazonensis infection alters the TLR signaling pathways by modulating the expression of miRNAs in macrophages to subvert the host immune responses.

Metabolomic Profile of BALB/c Macrophages Infected with Leishmania amazonensis: Deciphering L-Arginine Metabolism

“…However, the parasite can subvert the activation of macrophages to establish infection [36]. The genomic and transcriptomic networks during Leishmania infection have been providing interesting data regarding how Leishmania can to modulate the gene organization and gene expression of its host [37][38][39][40]. Additionally, we have observed differentially expressed genes profile during the different phases of parasite growth [37,38,41].…”

MicroRNAs: Biological Regulators in Pathogen–Host Interactions

“…Also, L. donovani strain, which is resistant to sodium stibogluconate, a pentavalent antimonial that is used for visceral leishmaniasis treatment in the Indian subcontinent, upregulates the expression of miR-466i in murine macrophages that target MyD88, increasing the levels of IL-10 production and the severity of disease [57]. Our group showed that the upregulation of let-7e, let-7f, and let-7g occurs in a MyD88, TLR2, or TLR4 dependent way during L. amazonensis infection and let-7e inhibition increases the expression of NOS2 mRNA, the NOS2 protein amount, and NO production, thus impacting infectivity [90]. Also, let-7e inhibition during L. amazonensis infection upregulates the levels of the validated targets, Tnfpaip3, Map2k4, Tbk1, and Tnf, as well as in the predicted targets, Traf 6, Ppara, Mapk8ip3/Jip3, Map3k1, and Ube2n, globally impacting TLR signaling gene expression [90].…”

“…Our group showed that the upregulation of let-7e, let-7f, and let-7g occurs in a MyD88, TLR2, or TLR4 dependent way during L. amazonensis infection and let-7e inhibition increases the expression of NOS2 mRNA, the NOS2 protein amount, and NO production, thus impacting infectivity [90]. Also, let-7e inhibition during L. amazonensis infection upregulates the levels of the validated targets, Tnfpaip3, Map2k4, Tbk1, and Tnf, as well as in the predicted targets, Traf 6, Ppara, Mapk8ip3/Jip3, Map3k1, and Ube2n, globally impacting TLR signaling gene expression [90]. It is interesting that the infection of macrophages with Mycobacterium and Neisseria upregulate the levels of let-7e [91,92].…”

Differential expression of polyamine biosynthetic pathways in skin lesions and in plasma reveals distinct profiles in diffuse cutaneous leishmaniasis

“…The polyamine biosynthetic pathway has been described as critical to promote Leishmania intracellular replication inside host macrophages 6,18,19 . In this exploratory study, we performed a detailed investigation of the expression profiles of components of such pathway in skin lesions and in peripheral blood of patients presenting with distinct clinical forms within the spectrum of TL disease.…”