Expression of Serum Exosomal miRNA 122 and Lipoprotein Levels in Dogs Naturally Infected by Leishmania infantum: A Preliminary Study

SIMPLE SUMMARY: The immunopathogenesis of leishmaniasis is not completely understood. Exosomes are extracellular vesicles produced by most eukaryotic cells, containing various molecular constituents with biological effects (e.g., proteins, peptides, RNA). They play an important role in cell-to-cell signaling. Recently, exosomal microRNA were demonstrated to be able to regulate gene expression and protein production in mammalian cells, serving as potential biomarkers of disease. The microRNA miR-122 is a biomarker of hepatic damage widely studied in mice in the course of Leishmania infection. Leishmania organisms can interfere with miR-122 production leading to a dysfunction in cholesterol metabolism ensuring its proliferation in the infected host. In this study, we suggest that such a phenomenon may also occur in dogs affected by Leishmania infection. ABSTRACT: Current knowledge on the role of exosomal microRNA (miRNA) in canine leishmaniasis (CL), with particular regards to the interaction between miR-122 and lipid alterations, is limited. The aim of this study was to isolate/characterize exosomes in canine serum and evaluate the expression of miR-122 in ten healthy and ten leishmaniotic dogs. Serum exosomes were isolated using a polymer-based kit, ExoQuick(®) and characterized by flow cytometry and transmission electron microscopy, whereas miR-122-5p expression was evaluated by quantitative reverse-transcriptase polymerase chain reaction. A significant decreased expression of exosomal miR-122-5p, decreased serum levels of high-density lipoproteins, and increased serum levels of low-density lipoproteins were seen in leishmaniotic dogs when compared with healthy dogs. These results suggest that hepatic dysfunctions induced by the parasite interfere with lipoprotein status. The decreased expression of exosomal miR122 represents an additional effect of Leishmania infection in dogs as in people.