“Smoke, Choline-Acetyl-Transferase, Muscarinic Receptors and fibroblast proliferation in COPD

Acetylcholine (ACh), synthesized by choline acetyltransferase (ChAT), and muscarinic M1, M2, and M3 receptors (MRs) are involved in fibroblast proliferation. We evaluated ChAT, MRs, and extracellular signal-regulated kinase (ERK) 1/2 and nuclear factor (NF) κB activation in lung fibroblasts from patients with chronic obstructive pulmonary disease (COPD), control smokers, and controls. Human fetal lung fibroblasts (HFL-1) stimulated with interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and cigarette smoke extracts (CSEs) were evaluated for ChAT and MR expression. We tested the effects of ACh on fibroblast proliferation and its ability to bind fibroblasts from patients with COPD, control smokers, controls, and HFL-1 stimulated with IL-1β, TNF-α, and CSE. ChAT, M1, and M3 expression and ERK1/2 and NFκB activation were increased, whereas M2 was reduced, in COPD and smoker subjects compared with controls. IL-1β increased the ChAT and M3, TNF-α down-regulated M2, and CSE increased ChAT and M3 expression while down-regulating the expression of M2 in HFL-1 cells. ACh stimulation increased fibroblast proliferation in patients with COPD, control smokers, and controls, with higher effect in control smokers and patients with COPD and increased HFL-1 proliferation only in CSE-treated cells. The binding of ACh was higher in patients with COPD and in control smokers than in controls and in CSE-treated than in IL-1β- and TNF-α-stimulated HFL-1 cells. Tiotropium (Spiriva; [1α,2β,4β,5α,7β-7-hydroxydi-2-thienylacetyl)oxy]-9,9-dimethyl-3-oxa-9-azoniatrcyclo[3.3.1.024], C19H22 NO4S2Br·H2O), gallamine triethiodide (C19H22N4O2S·2HCl·H2O), telenzepine [4,9-d-dihydro-3-methyl-4-[(4-methyl-1piperazinyl) acetyl]-10H-thieno [3,4-b][1,5]benzodiazepine-10-one dihydrobromide, C30H60I3N3O3], 4-diphenylacetoxy-N-methylpiperidine, PD098059 [2-(2-amino-3methoxyphenyl)-4H-1benzopyran-4-one, C16H13NO3], and BAY 11-7082 [(E)-3-(4-methylphenylsulfonyl)-2-propenetrile, C10H9NO2C], down-regulated the ACh-induced fibroblast proliferation, promoting the MRs and ERK1/2 and NFκB pathways involvement in this phenomenon. These results suggest that cigarette smoke might alter the expression of ChAT and MRs, promoting airway remodeling in COPD and that anticholinergic drugs, including tiotropium, might prevent these events.