Defining the Molecular Signal Pathways and Upstream Regulators in Cutaneous Leishmaniasis with Transcriptomic Data Approach

Abstract

Leishmaniasis is a disease caused by the genus Leishmania spp., which are intracellular parasites. Depending on parasite species and host immune response, there are three basic clinical forms of the disease: cutaneous, mucocutaneous, and visceral leishmaniasis. Cutaneous leishmaniasis is a chronic disease and characterized by the presence of ulcerated skin lesions. The type of skin pathology seen during disease is determined in part by the infecting Leishmania spp., but also by a combination of inflammatory and antiinflammatory host immune response factors resulting in diverse clinical outcomes. In this study, it was aimed to determine the genes, molecular signaling mechanisms and biological functions of the molecules that play a role in the pathogenesis of the disease and immune response and determine host-parasite interactions in mice that are naturally resistant and susceptible to Leishmania major and Leishmania braziliensis. For this, transcriptomic series GSE56029 was downloaded from "Gene Expression Omnibus"(GEO) data base, including expression profiling of twenty-four tissue samples that were recovered from both naive mice and mice (BALB/c, C57BL/6) infected with L.major and L.braziliensis. Then, "Differentially Expressed Genes" (DEGs) were identified by limma package in R script. FDR q<0.05 and absolute log2FC> 2 as threshold values were accepted in the analysis. Subsequently, functional and pathway enrichment analyses were performed for the DEGs by "Ingenuity Pathway Analysis" (IPA). For each of DEGs, p<0.01, FDR q<0.01, and absolute log2FC> 1 were used and analyzed with the software program IPA 8.0. Ingenuity Pathway Analysis revealed the most enrichment pathways to be the inflammation, dendritic cell maturation and "Triggering Receptor Expressed on Myeloid Cells 1" (TREM-1) signal mechanisms and that the DEGs related to the regulation of immune system process were closely associated with the progress of cutaneous leishmaniasis. The upstream regulator analysis predicted that TNF-α, IFNy, IL-1 β, IL-10RA and "Signal Transducer and Activator of Transcription-1" (STAT-1) are the regulators that explained gene expression changes causing biological activities in the tissues. Chemical compounds that may have anti-leishmanial effects were also identified in the study. In this study, the mechanisms belonging to the parasite species and host that determine the resistance/susceptibility phenotype were attempted to elucidate. Assessment of gene expression patterns, cytokine/chemokines, and signaling pathways in BALB/c and C57BL/6 mice infected with L.major and L.braziliensis will provide a better understanding of the potential mechanisms underlying infection from a genetic perspective. These results may guide for the future studies in terms of developing potential biomarkers for the diagnosis and prognosis prediction of cutaneous leishmaniasis and providing information about new treatment targets.