Authors

Discussion

Leishmaniasis is a tropical neglected disease caused by parasitic protozoa from the Leishmania genus. The understanding of underlying mechanisms of host-parasite interaction allowing infection persistence is necessary for a scenario where vaccines are not available and drug resistance is increasing. It is well established in the literature that the macrophage host cell microRNA (miRNA) profile can determine Leishmania survival. Here, we investigate immune response-related miRNAs of THP-1 derived macrophages infected with L. amazonensis.

Our group demonstrated that murine miR-294 targets nitric oxide synthase 2 (Nos2) mRNA. To investigate if human macrophages are regulated the same way, we determined the miRNA profile of L. amazonensis infected human THP-1 macrophages.  We identified that the miR-372, homologous to the mmu-miR-294, is upregulated in infected human macrophages, as well as other paralogous miRNAs, the miR-373 and miR-520d. Functional inhibition of miR-372 and miR-520d, but not miR-373 reduced the infectivity of L. amazonensis. Since the miRNAs miR-372-373-520d share the nucleotides responsible for target recognition, they must regulate similar pathways and the action of miR-373 could be masked by the action of miR-372 or miR-520d. To test this hypothesis, we simultaneously transfected miRNA inhibitors for miR-372, miR-373, and 520d, which resulted in fact in a reduction of infectivity, greater than the observed by inhibiting single miRNAs.

To test if L-arginine metabolism mRNAs can also be targeted in human macrophages, we performed RT-qPCR but no statistically significant difference was found comparing uninfected and Leishmania-infected THP-1 macrophages. We also found that the site for mmu-miR-294 and hsa-miR-372-373-520d present in murine Nos2 mRNA is mutated in humans.

As the inhibition of miRNAs showed a reduced infection, we performed bioinformatic analysis that pointed to other targets for miR-372-373-520d , which will be further investigated. MiRNAs, either alone or in combination, have already been used in clinical studies as anti-tumor therapies. Given the current status of increasing drug resistance, these findings provide good candidates for potential targets for host-directed therapy.