Cigarette Smoke Exposure Limits Functional Efficacy of CFTR Modulator Therapy in Cell Culture and Animal Models

Abstract Rationale: We previously found that secondhand smoke (SHS) exposure is associated with reduced CFTR modulator efficacy in CFF Patient Registry epidemiologic data. This project now investigates the direct impact of cigarette smoke on ETI response in laboratory models. Methods: Fisher Rat Thyroid (FRT) cells expressing either WT- or F508del-CFTR were grown at an air-liquid interface and treated with elexacaftor and tezacaftor in the setting of escalating doses of cigarette smoke exposure (0%, 0.25%, 0.5%, 1% CSE) for 48 hours. In vitro CFTR function was quantified by the change in short circuit current (ΔIsc) by Ussing chamber electrophysiology following treatment with forskolin, ivacaftor, and CFTRinh-172. Similarly, following a 5-week SHS exposure from 1R6F cigarettes/Air Control, we tested oral ivacaftor (30 mg/kg/day) or 1% methylcellulose effect on CFTR potentiation. CFTR function was quantified by nasal potential difference (NPD) across sinus epithelia. Statistical analysis was performed in R and GraphPad Prism. Results: Exposure to 1% CSE significantly reduced the benefit of Trikafta treatment on CFTR function (14.8 µA/cm295% CI -1.97 to 31.52 vs 64.0 µA/cm295% CI: 7.97-120; p<0.05). Lower concentrations of CSE (0.5% and 0.25%) did not result in a statistically significant reduction in CFTR-dependent ΔIsc. Similar to the FRT data, smoke exposure nullified ivacaftor benefit in vivo. Exposure of hG551D rats to CSE reduced the magnitude of NPD change after ivacaftor from -5.8 (SD 3.7, n=16) to -0.81 (SD 0.50, n=8, p<0.005). Conclusion: CSE directly inhibits CFTR response to modulator therapy in a dose dependent manner in vitro. Similarly, smoke exposure leads to reduced efficacy of IVA in the hG551D CF rat. Our forthcoming work will identify the targetable mechanisms through which CSE decreases CFTR expression, function, and response to therapeutic intervention. These models will allow us to test interventional strategies to combat the deleterious impact of CSE on CFTR modulator efficacy in vitro and in vivo.Page 1 of 1