Exploring the anti-inflammatory effect of commensal lung microbiota members in a 3-D lung epithelial cell model

Chronic lung inflammation is a hallmark of respiratory diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) and there is an urgent need for more effective anti-inflammatory treatments that have less side effects than the 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 invivo models of lung inflammation. Therefore, we hypothesized that the lung microbiota may contain other bacteria with anti-inflammatory properties. We isolated aerobic and anaerobic microbiota members 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, and tested cytotoxicity using an LDH assay. Next, anti-inflammatory and non-cytotoxic isolates were tested at varying doses to determine the minimal effective dose, and the anti-inflammatory effect was evaluated on the secretion of interleukin (IL)-8. We demonstrate that various lung microbiota members inhibit NF-κB pathway activation and IL-8 secretion, and that the minimal effective dose strongly varies between anti-inflammatory species. Few isolates exerted cytotoxic effects. This study shows that members of the lung microbiota may influence inflammation, which could open up new avenues for treatment.