Gut microbiota modulate susceptibility to bleomycin-induced lung injury

Acute lung injury (ALI) resulting in acute respiratory distress syndrome (ARDS) affects almost 200,000 people in the US each year, leading to 75,000 deaths. Airway instillation of bleomycin (BLM) in mice is a widely used, yet challenging model for ALI due to high variability. We have observed that B6 mice from two SPF facilities at our University exhibit significantly different mortality and weight loss in response to BLM. To test whether the facility-dependent response to BLM can be transferred by the microbiome, we conventionalized germ-free (GF) B6 littermates in each facility and challenged with BLM. Conventionalized GF mice recapitulated the respective donors’ response to BLM. Further, fecal microbiota transfer from the facility where the mice had worse mortality into the mice in the facility with more survival rendered recipient mice more susceptible to BLM compared to controls, indicating that the differential gut microbiome between two facilities were sufficient to modulate BLM response. To identify microorganisms that drive the phenotype, we compared gut microbial community memberships by 16S rRNA and metagenomics sequencing. Interestingly, BLM highly susceptible mice had greater alpha diversity and harbored specific species of Bacteroides, Prevotella, and Helicobacter genera. Flow cytometry of the lung immune cell landscape at baseline revealed comparable composition and phenotype of adaptive immune cells regardless of facility. However, lung NK cells were significantly increased BLM highly susceptible mice. Thus, we demonstrate that distinct gut microbiota communities modulate death and weight loss in response to BLM-induced lung injury, implicating host-commensal interactions in regulating ALI outcomes.