C70-22 Cigarette Smoke Exposure Limits Efficacy of Cftr Modulator Therapy in Preclinical Models

Introduction Previous epidemiologic data indicates that children with CF exposed to cigarette smoke (CS) experience a diminished response to CFTR modulators. This project investigates the direct impact of CS on CFTR-directed therapies in preclinical models. Hypothesis CFTR modulator efficacy is compromised by CS exposure in both in vitro and in vivo model systems. Methods In-vitro : FRT cells (G551D/F508del) exposed to CS extract were treated with CFTR modulators ivacaftor (VX-770, 10 μM) for G551D and/or a combination of Elexacaftor (VX-445, 3 μM) and Tezacaftor (VX-661, 5 μM) for F508del. Isc measurements evaluated CFTR-mediated chloride channel function. qPCR quantified biochemical responses to CSE. In-vivo : hG551D rats were exposed to secondhand CS while controls were exposed to air for 12 weeks (daily for 1 hour). During the final three days of exposure, all the animals received ivacaftor (orally, 30 mg/kg/day). CFTR functional efficacy was analyzed by NPD measurements, tracheal Isc measurements, ASL depth, MCT rates and reflectivity, serving as ion and fluid transport markers of CFTR. qPCR quantified biochemical response to CS. Results CSE reduced the functional efficacy of modulators by > 50% in gene edited cells lines including G551D (p < 0.01) and F508del cells (p < 0.024). Similarly, CS reduced CFTR transcripts by 0.59 fold (p < 0.01) and increased TGF-β signaling (PAI-1, p < 0.0001). In CF animal models (hG551D rats), CS reduced NPD response to ivacaftor (Air: -5.8±3.7mV; Smoke: -0.81±0.5mV, p < 0.005) while Isc data showed over 50% reduction in CFTR function in CS exposed animals (p < 0.05) μOCT data showed similar reductions in ivacaftor effects on PCL (Air: 3.24±0.17μm; Smoke: 2.47±0.28 μm, p < 0.0001) and MCT (Air: 28.33±10.71μm/s, Smoke: 10.77±3.44μm/s, p < 0.0001). Trachea from CS exposed rats showed increased dynamic mucus viscosity compared to air exposed thus having higher optical reflectance intensity (Air: 1922.133±1296, Smoke: 5264±2571, p = 0.038) marked by the difference in light scattered in the mucus layer. Furthermore, CFTR expression were reduced and TGF- β transcripts significantly upregulated in the smoke exposed hG551D rat lung compared to air control. Conclusions CS exposure limits modulator stimulated CFTR functional efficacy in both in vitro and in vivo models. Our biochemical data suggest that CS alters the biochemical expression of CFTR at least partially through enhanced TGF-β signaling. Our data indicate a direct relationship between CS exposure and suggest potential targetable mechanisms to enhance CFTR-directed therapy. This abstract is funded by: Cystic Fibrosis Foundation (HARRIW23G0) and