Commensal lung microbiota members inhibit activation of the pro-inflammatory NF-?B pathway in three-dimensional lung epithelial cells

Abstract

Chronic lung inflammation is the major pathophysiological trait in respiratory diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). There is a need for novel anti-inflammatory approaches due to ineffectiveness and/or side effects of current therapies. A central player in the regulation of the transcriptional response of lung epithelial and immune cells to various pro-inflammatory mediators in chronic lung disease is the nuclear factor (NF)-kappaB (NF-κB). Our group recently identified a non-pathogenic commensal of the lung microbiota, i.e. Rothia mucilaginosa, that inhibits inflammation by interfering with NF-κB pathway activation in in vitro and in vivo models of lung inflammation. Therefore, we hypothesized that the lung microbiota may contain other bacteria with anti-inflammatory properties. We isolated a collection of microbiota members, including aerobic and anaerobic species, from CF patient sputum samples and evaluated their ability to reduce lipopolysaccharide (LPS)-triggered NF-κB-pathway activation in an in vivo-like three-dimensional (3-D) alveolar epithelial cell model (A549 luciferase NF-κB-reporter). Species were tested at varying multiplicity of infection (MOI) to determine the minimal effective dose, and their cytotoxicity was evaluated using an LDH assay. We demonstrate that various lung microbiota members inhibit NF-κB pathway activation, and that the minimal effective dose strongly varies between anti-inflammatory species. Few commensal species exerted cytotoxic effects. This study shows that members of the lung microbiota may influence inflammation, which could offer new avenues for treatment.