Lin VY, Kaza N, Birket SE, Kim H, Edwards LJ, LaFontaine J, Liu L, Mazur M, Byzek SA, Hanes J, Tearney GJ, Raju SV, and Rowe SM
The mechanisms by which cigarette smoking impairs airway mucus clearance are not well understood. We recently established a ferret model of cigarette smoke-induced chronic obstructive pulmonary disease (COPD) exhibiting chronic bronchitis. We investigated the effects of cigarette smoke on mucociliary transport (MCT).Adult ferrets were exposed to cigarette smoke for 6 months, with in vivo mucociliary clearance measured by technetium-labelled DTPA retention. Excised tracheae were imaged with micro-optical coherence tomography. Mucus changes in primary human airway epithelial cells and ex vivo ferret airways were assessed by histology and particle tracking microrheology. Linear mixed models for repeated measures identified key determinants of MCT.Compared to air controls, cigarette smoke-exposed ferrets exhibited mucus hypersecretion, delayed mucociliary clearance (-89.0%, p<0.01) and impaired tracheal MCT (-29.4%, p<0.05). Cholinergic stimulus augmented airway surface liquid (ASL) depth (5.8±0.3 to 7.3±0.6 µm, p<0.0001) and restored MCT (6.8±0.8 to 12.9±1.2 mm·min -1 , p<0.0001). Mixed model analysis controlling for covariates indicated smoking exposure, mucus hydration (ASL) and ciliary beat frequency were important predictors of MCT. Ferret mucus was hyperviscous following smoke exposure in vivo or in vitro , and contributed to diminished MCT. Primary cells from smokers with and without COPD recapitulated these findings, which persisted despite the absence of continued smoke exposure.Cigarette smoke impairs MCT by inducing airway dehydration and increased mucus viscosity, and can be partially abrogated by cholinergic secretion of fluid secretion. These data elucidate the detrimental effects of cigarette smoke exposure on mucus clearance and suggest additional avenues for therapeutic intervention., Competing Interests: Conflict of interest: V.Y. Lin has nothing to disclose. Conflict of interest: N. Kaza has nothing to disclose. Conflict of interest: S.E. Birket has nothing to disclose. Conflict of interest: H. Kim has nothing to disclose. Conflict of interest: L.J. Edwards has nothing to disclose. Conflict of interest: J. LaFontaine has nothing to disclose. Conflict of interest: L. Liu has a patent “Method for functional investigation of respiratory airways and other ciliated tissues using µOCT” pending. Conflict of interest: M. Mazur has nothing to disclose. Conflict of interest: S.A. Byzek has nothing to disclose. Conflict of interest: J. Hanes is founder and owner of company stock (which is subject to certain rules and restrictions under Johns Hopkins University policy) of GrayBug Vision, Inc., and Kala Pharmaceuticals, Inc., outside the submitted work. Conflict of interest: G.J. Tearney has patents 14/240,938 and 12826303.5 pending. Conflict of interest: S.V. Raju has nothing to disclose. Conflict of interest: S.M. Rowe reports grants from Bayer, Forest Research Institute, AstraZeneca, N30/Nivalis, Novartis, Galapagos/AbbVie, Proteostasis, PTC Therapeutics and Eloxx, grants and personal fees for consultancy from Celtaxsys, personal fees for consultancy and advisory board work and in kind support for clinical trial work from Vertex Pharmaceuticals Incorporated, personal fees for consultancy from Bayer and Novartis, outside the submitted work; and has a patent “Use of OCT as a diagnostic modality for diseases of mucus clearance” issued., (Copyright ©ERS 2020.)