P. aeruginosatRNA-fMet halves secreted in outer membrane vesicles suppress lung inflammation in Cystic Fibrosis

Abstract

Although tobramycin increases lung function in people with cystic fibrosis (pwCF), the density ofPseudomonas aeruginosa (P. aeruginosa)in the lungs is only modestly reduced by tobramycin; hence, the mechanism whereby tobramycin improves lung function is not completely understood. Here, we demonstrate that tobramycin increases 5′ tRNA-fMet halves in outer membrane vesicles (OMVs) secreted by laboratory and CF clinical isolates ofP. aeruginosa. The 5′ tRNA-fMet halves are transferred from OMVs into primary CF human bronchial epithelial cells (CF-HBEC), decreasing OMV-induced IL-8 and IP-10 secretion. In mouse lung, increased expression of the 5′ tRNA-fMet halves in OMVs attenuated KC secretion and neutrophil recruitment. Furthermore, there was less IL-8 and neutrophils in bronchoalveolar lavage fluid isolated from pwCF during the period of exposure to tobramycin versus the period off tobramycin. In conclusion, we have shown in mice andin vitrostudies on CF-HBEC that tobramycin reduces inflammation by increasing 5′ tRNA-fMet halves in OMVs that are delivered to CF-HBEC and reduce IL-8 and neutrophilic airway inflammation. This effect is predicted to improve lung function in pwCF receiving tobramycin forP. aeruginosainfection.New and noteworthyThe experiments in this report identify a novel mechanim whereby tobramycin reduces inflammation in two models of CF. Tobramycin increased the secretion of tRNA-fMet haves in OMVs secreted byP. aeruginiosa, which reduced the OMV-LPS induced inflammatory response in primary cultures of CF-HBEC and in mouse lung, an effect predicted to reduce lung damage in pwCF.Graphical abstractThe anti-inflammatory effect of tobramycin mediated by 5′ tRNA-fMet halves secreted inP. aeruginosaOMVs.(A)P. aeruginosacolonizes the CF lungs and secrets OMVs. OMVs diffuse through the mucus layer overlying bronchial epithelial cells and induce IL-8 secretion, which recruits neutrophils that causes lung damage. (B) Tobramycin increases 5′ tRNA-fMet halves in OMVs secreted byP. aeruginosa. 5′ tRNA-fMet halves are delivered into host cells after OMVs fuse with lipid rafts in CF-HBEC and down-regulate protein expression of MAPK10, IKBKG, and EP300, which suppresses IL-8 secretion and neutrophils in the lungs. A reduction in neutrophils in CF BALF is predicted to improve lung function and decrease lung damage.