Leishmania infection-derived extracellular vesicles drive transcription of genes involved in M2 polarization

Abstract

Although it is known that the composition of extracellular vesicles (EVs) is determined by the characteristics of the cell and its environment, the effects of intracellular infection on EV composition and functions are not well understood. We had previously shown that cultured macrophages infected with Leishmania parasites release EVs (LiEVs) containing parasite-derived molecules. In this study we show that LdVash, a molecule previously identified in LiEVs from L. donovani infected RAW264.7 macrophages, is widely distributed in the liver of L. donovani infected mice. This result shows for the first time that parasite molecules are released in EVs and distributed in infected tissues where they can be endocytosed by cells in the liver, including macrophages that significantly increase numbers as the infection progresses. To evaluate the potential impact of LiEVs on macrophage functions, we show that primary peritoneal exudate macrophages (PECs) express transcripts of signature molecules of M2 macrophages such as arginase 1, IL-10, and IL-4R when incubated with LiEVs. In comparative studies that illustrate how intracellular pathogens control the composition and functions of EVs released from macrophages, we show that EVs from RAW264.7 macrophages infected with Salmonella Typhimurium activate PECs to express transcripts of signature molecules of M1 macrophages such as iNOS, TNF alpha, and IFN-gamma and not M2 signature molecules. Finally, in contrast to the polarized responses observed in in vitro studies of macrophages, both M1 and M2 signature molecules are detected in L. donovani infected livers, although they exhibit differences in their spatial distribution in infected tissues. In conclusion, EVs produced by macrophages during Leishmania infection lead to the gene expression consistent with M2 polarization. In contrast, the EVs produced during S. Typhimurium infection stimulated the transcription of genes associated with M1 polarization.

Platelet-Derived Microvesicles Contribute to the Pathophysiogenesis of Human Cutaneous Leishmaniasis: A Nano-Flow Cytometric Approach in Plasma Samples from Patients before and under Antimonial Treatment

“…Studies evaluating the role of EVs in diseases caused by protozoa, such as cutaneous leishmaniasis, are scarce, and they were regarded as the function of EVs produced and released by the Leishmania protozoa itself [ 31 , 32 , 33 ]. In this context, the current study has used nano-flow cytometry and plasma samples from CL patients and healthy individuals to elucidate the contribution of platelet-derived MVs (pMVs) in the CL pathophysiogenesis, correlating it with the acute inflammatory phase and with antimonial treatment against the pathogen.…”

“…To date, there are no systematic studies on the roles and corresponding mechanisms of pEVs in the pathophysiology of CL, and most of the articles found on this issue focused on investigating the impact of the protozoan-derived EVs in the host immune responses [ 31 , 32 , 33 ]. In order to address this gap in knowledge, we investigated the contribution of pMVs in the pathophysiology of acute cutaneous leishmaniasis and during antimony treatment.…”

Extracellular Vesicles and Their Impact on the Biology of Protozoan Parasites

“…EVs from L. amazonensis promoted the progression of the disease by increasing the expression of IL-6 and IL-10 by naïve macrophages [ 54 ]. Recent work has shown that the EVs secreted by Leishmania -infected macrophages (LiEVs) contain parasite-derived molecules and can carry these to the liver in murine models of infection [ 59 , 60 ]. Although there was some initial evidence that LiEVs are associated with the M2 polarization of macrophages, further work is required to verify that the EVs are responsible for the alternatively activation of M2 polarization.…”