Cytokine Gene Expression Alterations in Human Macrophages Infected by Leishmania major

Abstract

Objective: Leishmaniasis is caused by members of the Leishmania species and constitute a group of infective diseases that range from cutaneous lesions to lethal visceral forms. In infected persons, macrophages recognize and eliminate the parasites via phagocytosis. In order to change a hostile environment into an environment adequate for survival and reproduction, the engulfed Leishmania species needs to modulate the function of its host macrophage. The expression patterns of cytokine genes such as interleukin-12 (IL-12), tumour necrosis factor-alpha (TNF-α), IL-1, and interferon-gamma (IFNγ) represent the immune response. In this study, we employed an RNA-seq approach for human monocyte-derived macrophages infected with Leishmania major (L. major) to decipher cytokine gene expression alterations in host macrophages.

Materials and methods: In this descriptive study, human monocytes were isolated by magnetic activated cell sorting (MACS) and cultured in the presence of monocyte colony stimulating factor (M-CSF) to obtain the macrophages. Monocyte-derived macrophages were then co-cultured with metacyclic promastigotes of L. major for 4 hours. RNA isolation was performed using TRIzol reagent. RNA sequencing was performed using the Illumina sequencing platforms. Gene expression analysis was performed using a Bioconductor DESeq2 package.

Results: Our data revealed significant changes in immune response gene expressions in macrophages infected with L. major, with an up-regulation of cytokines and mostly down-regulation of their receptors.

Conclusion: The obtained data could shed more light on the biology of L. major and how the host cell responds to leishmaniasis.

Keywords: Chemokines; Cytokines; Leishmania major; Macrophages; RNA Sequencing.

Fig.1

Gene expression pattern showing different expressions of noninfected samples compared to infected samples. As seen in the noninfected cells, the gene expression pattern is almost similar. In infected cells, the gene expression pattern is clearly altered. A. The different expression patterns for infected (grey column) and non-infected (red column) cells are shown. B. Non-infected cells exhibit a more similar gene expression pattern.

Fig.2

Expression levels of CC chemokine genes are higher than CxC chemokines. CCL2 and CCL7 chemokines were down-regulated. CCL2 seems to be one of the most important targets of Leishmania major (L. major) that is reprogrammed by this parasite. Most of the chemokine genes showed up-regulated expression patterns; thus, it may indicate the importance of cellular recruitments early infection time point.