Avaliação da influência da obesidade na microbiota pulmonar em modelo murino de asma alérgica

Abstract

Asthma is the most common inflammatory airway disease and its prevalence has increased worldwide. Obesity is also a risk factor for asthma and preliminary studies demonstrated that obese asthmatic subjects presented high levels of IL-17A and neutrophils in the lungs, demonstrating that they have a distinct phenotype from classic allergy. Evidence has been raised indicating that the gut microbiota play an important role setting different features of asthma. However, there are not studies showing the influence of obesity in a pulmonary microbiota. Therefore, the present study aimed to evaluate the influence of obesity on the pulmonary microbiota in a model of allergic asthma. Female BALB/c mice fed a high fat diet during 14 weeks, sensitized and challenged with Ovalbumin (OVA), were euthanized 24h and 48h after the last OVA challenge. Pulmonary microbiota was analyzed through Fluorescent in situ Hybridization (FISH) and quantitative Polymerase Chain Reaction (qPCR). Lung microbiota effect over dendritic cells was evaluated in coculture with bone marrow derived dendritic cells (BDMC). Both obesity and allergy increased Firmicutes/Bacteroidetes ratio in the gut. Obese and obese-allergic mice presented higher pulmonary IL-17A levels. Obesity increased Proteobacteria and diminished Firmicutes counting, associated with higher TLR-4 and reduced TLR-2 expression by pulmonary DCs. After allergy induction, these markers increased over time, obese allergic mice, which presented diminished Proteobacteria and increased Firmicutes number, compared to allergic group. Obese BMDC coculture with lung microbiota, showed reduced TLR-2/4 and CD80 expression. These data suggests obesity is able to modify pulmonary microbiota, before and after allergy induction. These changes promoted lung homeostasis disruption, causing the delay of immune response development and Th17 profile onset. This work provides a novel mechanism by which obesity worsens asthma. Hence, the better understanding of those interactions will contribute to the development of new treatment strategies suitable for that distinct asthma phenotype.