Avaliação da expressão e do papel dos microRNAs mmu-miR-155-5p e mmu-miR-146b-5p durante a infecção pulmonar causada pela bactéria Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is an important opportunistic human pathogen capable of causing severe infections in immunocompromised patients and in patients with cystic fibrosis. To trigger an effective response against infection by P. aeruginosa is required a first line of recognition of this bacterium by the innate immune system. Although the innate immune response is beneficial in the control of P. aeruginosa infection, this response should be controlled. Recent studies have begun to clarify how miRNAs play key roles in regulating processes such as infection, immune response and inflammation by participating in the immune response modulation. Due to the importance of the P. aeruginosa bacterium in infectious processes in humans and stimulated by the need to uncover the mechanisms of regulation of the immune response against this bacterium, the objective of this study was to evaluate the role of mmu-miR-155-5p and mmu-miR-146b -5p expressed in mice infected with strains ATCC 27853 and PA14 of the bacterium P. aeruginosa. To assess the level of expression of mmu-miR-155-5p and mmu-miR-146b-5p and the cytokines IL-1β, IL-6 and IL-12 in vitro, the total RNA was extracted from Raw 264.7 cells, bone marrow derived macrophages (BMDM) and bone marrow-derived dendritic cells (BMDC) for real-time PCR analysis. After infection of the Raw 264.7, BMDMs and BMDCs cells, it was possible to observe that the expression of miRNAs and cytokines occurred in a dependent manner in each infected cell type. For the in vivo analyzes C57BL / 6 mice were infected intratracheally with the strains ATCC 27853 and PA14 of P. aeruginosa for analysis of CFU, RT-qPCR, histopathology and stereology. Only the PA14 strain was recovered in the lungs and spleens of the animals, where no variation in the expression of mmu-miR-155-5p or a significant increase in a series of effector cytokines was observed. Histopathological analyzes demonstrated an intense diffuse inflammatory process, presenting a larger number of inflammatory cells, a decrease in the number of alveoli and the volume of the star when compared to uninfected animals and animals infected by the avirulent strain. In the lung of animals infected with ATCC 27853 strain, increased expression of mmu-miR-155-5p and mmu-miR-146b-5p, of inflammatory cytokines was observed. The identification of regulatory networks of the miRNAs under study showed important direct and indirect targets associated with the innate immune response that may be compromised during the differential expression of mmu-miR-155-5p and mmu-miR-146b-5p in favor or detriment of P. aeruginosa infection. The results obtained to date suggest that the infection by P. aeruginosa exerts a modulation in the expression of miRNAs and consequently in the immune response against this bacterium and that the virulence of different strains of P. aeruginosa influence the expression of miRNAs mmu-miR- 155-5p and mmu-miR-146b-5p, of proinflammatory cytokines and in pathology. Further studies are needed to uncover the mechanisms by which virulent P. aeruginosa strains can subvert the immune response and ensure replication in its host.