Differential miRNA Expression in Human Macrophage-Like Cells Infected with Histoplasma capsulatum Yeasts Cultured in Planktonic and Biofilm Forms

Abstract

Histoplasma capsulatum affects healthy and immunocompromised individuals, sometimes causing a severe disease. This fungus has two morphotypes, the mycelial (infective) and the yeast (parasitic) phases. MicroRNAs (miRNAs) are small RNAs involved in the regulation of several cellular processes, and their differential expression has been associated with many disease states. To investigate miRNA expression in host cells during H. capsulatum infection, we studied the changes in the miRNA profiles of differentiated human macrophages infected with yeasts from two fungal strains with different virulence, EH-315 (high virulence) and 60I (low virulence) grown in planktonic cultures, and EH-315 grown in biofilm form. MiRNA profiles were evaluated by means of reverse transcription-quantitative polymerase chain reaction using a commercial human miRNome panel. The target genes of the differentially expressed miRNAs and their corresponding signaling pathways were predicted using bioinformatics analyses. Here, we confirmed biofilm structures were present in the EH-315 culture whose conditions facilitated producing insoluble exopolysaccharide and intracellular polysaccharides. In infected macrophages, bioinformatics analyses revealed especially increased (hsa-miR-99b-3p) or decreased (hsa-miR-342-3p) miRNAs expression levels in response to infection with biofilms or both growth forms of H. capsulatum yeasts, respectively. The results of miRNAs suggested that infection by H. capsulatum can affect important biological pathways of the host cell, targeting two genes: one encoding a protein that is important in the cortical cytoskeleton; the other, a protein involved in the formation of stress granules. Expressed miRNAs in the host’s response could be proposed as new therapeutic and/or diagnostic tools for histoplasmosis.

Common virulence factors between Histoplasma and Paracoccidioides: Recognition of Hsp60 and Enolase by CR3 and plasmin receptors in host cells

“…The progression of the disease hinges on the yeast cells’ ability to survive and multiply within these phagocytic cells, making the host-pathogen interaction a highly intricate phenomenon and a critical determinant of the disease's course. In this context, the innate immune response plays a pivotal role in influencing disease progression ( Cleare et al, 2017 ; Cohen et al, 2022 ; Guimarães, de Cerqueira, et al, 2011 ; Hahn et al, 2022 ; Loose et al, 1983 ; Mittal et al, 2019 ; N. de S. Pitangui et al, 2021 ; Shankar et al, 2011 ).…”

“…Besides these described genes in Histoplasma spp., recent publications have shown that biofilm formation could represent an important virulence mechanism in Histoplasma spp. ( Gonçalves et al, 2020 ; Pitangui et al, 2016 , 2021 ; Pitangui et al, 2012 ).…”

“…The differential expression of various miRNAs was observed in biofilm infection. Interactome analysis showed that the most affected metabolic pathways in macrophages were related to the regulation of fungus-host cell adhesion (receptor-ECM adhesion, focal adhesion), polysaccharide biosynthesis (glycosaminoglycans and N-glycans), regulation of cell structure and motility (actin cytoskeleton), protein degradation (ubiquitin-mediated proteolysis), response to proinflammatory stimuli (MAPK signaling), regulation of cellular homeostasis (apoptosis and gap junctions), amino acid metabolism (lysine degradation), and functional cellular effects of proliferation, differentiation, and cell migration ( Pitangui et al, 2021 ). The dysregulation of several metabolic pathways in host cells due to Histoplasma spp.…”