Leishmania donovani alters the host sphingolipid biosynthetic pathway regulatory microRNA hsa-miR-15a-5p for its survival.

Leishmania donovani is an intracellular protozoan parasite that has successfully evolved to manipulate host macrophages. The exact mechanism by which Leishmania spp evades macrophage function is not fully understood. Recently, several studies have shown that pathogens target host-microRNA to alter cellular pathways for their persistence. Here, we explored the alterations in host sphingolipid biosynthetic pathway regulatory microRNAs during Leishmania donovani infection. Here, the sphingolipid biosynthetic pathway genes serine palmitoyltransferase long chain base subunit 1 (SPTLC1), 3-ketodihydrosphingosine reductase (KDSR), ceramide synthase 1(CERS1) and dihydroceramide desaturase 1 (DEGS1) were found to be upregulated while N-Acylsphingosine Amidohydrolase 1 (ASAH1) was downregulated but no significant changes were observed in sphingomyelin synthase 1 (SGMS1) and sphingosine kinase 1 (SPHK1) in Leishmania donovani infected THP-1 derived macrophages (TDM) at 24 hours. Bioinformatic analysis using miRWalk 2.0 predicted SPTLC1 to be a target of hsa-miR-15a-5p and hsa-miR-330-5p, CERS1 to be targeted by hsa-miR-10396a-3p, and ASAH1 by hsa-miR-513a-5p; all of these miRNAs have been previously reported to be dysregulated during infection. Since hsa-miR-15a-5p was found common to target SPTLC1 in all three databases, namely Targetscan, miRDB, and miRTarBase therefore the expression of hsa-miR-15a-5p was selected for further studies. We found a downregulated expression of hsa-miR-15a-5p during Leishmania donovani infection. In silico target prediction followed by in vitro target validation of hsa-miR-15a-5p showed SPTLC1 as one of the targets. Additionally, mimics of hsa-miR-15a-5p reduced the expression of SPTLC1, upregulated mainly the proinflammatory cytokines, and reduced the parasites in TDM as well as Peripheral Blood Mononuclear Cell (PBMC) derived human macrophages.