Role of S1PR1 in Modulating Airway Epithelial Responses to Pseudomonas aeruginosa in Cystic Fibrosis

<b>Background:</b><i>Pseudomonas aeruginosa</i> infection is a major driver of morbidity and mortality in cystic fibrosis (CF), yet disease severity varies widely among people with CF (pwCF). This clinical heterogeneity suggests the involvement of host genetic modifiers beyond <i>CFTR</i>. We previously identified <i>sphingosine 1-phosphate receptor 1</i> (<i>S1PR1</i>) as a candidate gene associated with susceptibility to <i>P. aeruginosa</i>. Here, we investigated its role in modulating airway epithelial responses to infection. <b>Methods:</b> Using CRISPR/Cas9, we generated S1PR1-knockout bronchial epithelial cells with (IB3-1) and without (C38) <i>CFTR</i> mutations. We assessed cell viability, cytotoxicity, and interleukin-8 secretion following exposure to <i>P. aeruginosa</i> exoproducts. S1PR1 protein expression was evaluated in lung tissue from pwCF and non-CF individuals using immunohistochemistry. <b>Results:</b> S1PR1-mutant cells produced truncated, non-functional peptides. In CFTR-mutant cells, S1PR1 loss reduced viability, increased cytotoxicity, and significantly enhanced interleukin-8 production in response to <i>P. aeruginosa</i> exoproducts. These effects were not observed in CFTR-competent cells. Notably, S1PR1 protein levels were markedly lower in lung tissue from pwCF compared to non-CF individuals. <b>Conclusions:</b> S1PR1 deficiency exacerbates epithelial damage and inflammatory responses to <i>P. aeruginosa</i> in CF models. These findings highlight S1PR1 as a potential contributor to infection severity and a promising target for therapeutic strategies in pwCF.