MicroRNAs Expression Induces Apoptosis of Macrophages in Response to Leishmania major (MRHO/IR/75/ER): An In-Vitro and In-Vivo Study

Abstract

Background: We aimed to investigate the effect of miR-15a mimic and inhibitor of miR-155 expression on apoptosis induction in macrophages infected with Iranian strain of Leishmania major in-vitro and in-vivo.
 Methods: RAW 264.7 cells were infected with L. major promastigotes (MRHO/IR/75/ER), and then were treated with miRNAs. For in-vivo experiment, BALB/c mice were inoculated with L. major promastigotes, and then they were treated with miRNAs. For evaluation of miRNA therapeutic effect, in-vitro and in-vivo studies were performed using quantitative Real-time PCR, Flow cytometry, lesion size measurement, and Limiting Dilution Assay (LDA). This study was performed in Shahid Beheshti University of Medical Sciences in 2019.
 Results: In-vitro results of flow cytometry showed that using miR-15a mimic, miR-155 inhibitor or both of them increased apoptosis of macrophages. In in-vivo, size of lesion increased during experiment in control groups (P<0.05) while application of both miR-155 inhibitor and miR-15a mimic inhibited the increase in the size of lesions within 6 wk of experiment (P=0.85). LDA results showed that microRNA therapy could significantly decrease parasite load in mimic or inhibitor receiving groups compared to the control group (P<0.05).
 Conclusion: miR-155 inhibitor and miR-15a mimic in L. major infected macrophages can induce apoptosis and reduce parasite burden. Therefore, miRNA-based therapy can be proposed as new treatment for cutaneous leishmaniasis.

Bidirectional cytokine-microRNA control: A novel immunoregulatory framework in leishmaniasis

“…Similar paradox exists in miR-155 functions as well. On the one hand, miR-155 promotes M1 polarization while preventing M2 polarization and facilitates Leishmania elimination [ 3 , 37 , 42 ]; on the other hand, miR-155 promotes Leishmania persistence via inhibition of macrophage apoptosis [ 43 ]. Thus, a balanced miR-155 expression within macrophages needs to maintain M1 macrophage polarization without repressing apoptosis.…”

“…Indeed, miR-15a expression decreases while miR-155 increases in mouse macrophages after L . major infection [ 43 ]. miR-155 prevents macrophage apoptosis by targeting caspase 3, caspase 10, and APAF1 [ 56 – 59 ].…”

“…Therefore, targeting the apoptosis-regulating miRNAs in Leishmania-infected macrophages may have potential to control the infection. Indeed, miR-15a expression decreases while miR-155 increases in mouse macrophages after L. major infection [43]. miR-155 prevents macrophage apoptosis by targeting caspase 3, caspase 10, and APAF1 [56][57][58][59].…”

“…In the L. donovani-infected macrophages, miR-155, miR-335, miR-143, miR-221, miR-93, and let7c were associated with negative regulation of apoptosis [26]. Inhibition of antiapoptosis miRNAs can be proposed as a new strategy for treating leishmaniasis [43].…”

Highlighting the interplay of microRNAs from Leishmania parasites and infected-host cells

“…Additionally, the use of miR-15a mimic, miR-155 inhibitor or both of them increases the apoptosis rate of infected macrophages in vitro, and reduces the size of lesions in vivo within 6 weeks after the infection (Gholamrezaei et al, 2020) suggesting that miRNA-based therapy could be a possible novel treatment for cutaneous leishmaniasis.…”