Emma Lea Matthews

Cystic fibrosis (CF) is a genetic disorder that causes chronic airway disease, leading to accelerated aging, inflammation, and susceptibility to opportunistic infections. Pseudomonas aeruginosa (PA) is prevalent in the CF lung, often multidrug-resistant, and affecting lung function decline, highlighting a need for alternative treatment strategies, such as host-directed therapeutics. The PA metabolite pyocyanin can induce senescence-associated β-galactosidase (SA-βgal), a lysosomal cell senescence marker. However, whether PA can induce cell senescence and therefore affect immune functions has not been studied. Using established airway epithelial culture models, we observed that PA infection increased SA-βgal activity and proinflammatory cytokines without increasing a comprehensive set of cell senescence markers. PA infection also resulted in lysosomal neutralization and decreased lysosome biogenesis, with the latter attenuated by rapamycin (RAPA), a senolytic and an established inhibitor of mTOR signaling. In conclusion, our study implies that PA infection does not induce cell senescence in the CF bronchial epithelium but disturbs lysosomal homeostasis, which can be attenuated by RAPA. These findings highlight lysosomal health as a promising therapeutic target in CF airways, especially as patients live longer yet remain susceptible to recurrent airway infections.

The lung is a unique organ because of its continuous exposure to the external environment, which requires a complex and tightly regulated immune network

The number of adults living with cystic fibrosis (CF) has already increased significantly because of drastic improvements in life expectancy attributable to advances in treatment, including the development of highly effective modulator therapy. Chronic airway inflammation in CF contributes to morbidity and mortality, and aging processes like inflammaging and cell senescence influence CF pathology. Our results show that single-cell RNA sequencing data, human primary bronchial epithelial cells from non-CF and CF donors, a CF bronchial epithelial cell line, and Cftr -knockout ( Cftr ^–/– ) rats all demonstrated increased cell senescence markers in the CF bronchial epithelium. This was associated with upregulation of fibroblast growth factor receptors (FGFRs) and mitogen-activated protein kinase (MAPK) p38. Inhibition of FGFRs, specifically FGFR4 and to some extent FGFR1, attenuated cell senescence and improved mucociliary clearance, which was associated with MAPK p38 signaling. Mucociliary dysfunction could also be improved using a combination of senolytics in a CF ex vivo model. In summary, FGFR/MAPK p38 signaling contributes to cell senescence in CF airways, which is associated with impaired mucociliary clearance. Therefore, attenuation of cell senescence in the CF airways might be a future therapeutic strategy improving mucociliary dysfunction and lung disease in an aging population with CF.

Background and Objectives: Chronic inflammation due to Pseudomonas aeruginosa (PA) infection in people with cystic fibrosis (CF) remains a concerning issue in the wake of modulator therapy initiation. Given the perpetuating cycle of colonization, infection, chronic inflammation, and recurrent injury to the lung, there are increases in the risk for mortality in the CF population. We have previously shown that fibroblast growth factor (FGF) 23 can exaggerate transforming growth factor (TGF) beta-mediated bronchial inflammation in CF. Our study aims to shed light on whether FGF23 signaling also plays a role in PA infection of the CF bronchial epithelium. Materials and Methods: CF bronchial epithelial cells were pretreated with FGF23 or inhibitors for FGF receptors (FGFR) and then infected with different PA isolates. After infection, immunoblot analyses were performed on these samples to assess the levels of phosphorylated phospholipase C gamma (PLCγ), total PLCγ, phosphorylated extracellular signal-regulated kinase (ERK), and total ERK. Additionally, the expression of FGFRs and interleukins at the transcript level (RT-qPCR), as well as production of interleukin (IL)-6 and IL-8 at the protein level (ELISA) were determined. Results: Although there were decreases in isoform-specific FGFRs with increases in interleukins at the mRNA level as well as phosphorylated PLCγ and the production of IL-8 protein with PA infection, treatment with FGF23 or FGFR blockade did not alter downstream targets such as IL-6 and IL-8. Conclusions: FGF23 signaling does not seem to modulate the PA-mediated inflammatory response of the CF bronchial epithelium.