Regulation of Nitric Oxide by Cigarette Smoke in Airway Cells

Abstract

Background and Objectives:Exhaled nitric oxide (NO) is decreased by smoking while oxides of nitrogen such as nitrites/nitrates (NO x ) are increased. It was hypothesised that in vitro cigarette smoke extract (CSE) would either inhibit NO generation by increasing the NO synthase inhibitor, NG, NG-dimethyl-L-arginine (ADMA) or increase NO x levels via an oxidation pathway, which in turn could be inhibited by the antioxidant N-acetylcysteine NAC. Methods: Transformed airway cells (A549) were cultured with control medium, 1.0% CSE in culture medium, or 0.8 mM NAC with 1.0% CSE. Baseline L-arginine, NO x and ADMA levels were measured in the media. Conditioned media were then sampled at 1hour, 6 hours, 24 hours, 48 hours and 72 hours after incubation. Results: CSE induced significantly higher NO x levels (mean (SD) peak increase of 135.8 (126.6)% after incubation for 6 hours (p < 0.0005)). NAC pre-treatment partially reversed this effect to 35.6 (21.4)% at 6 hours (p = 0.009). ADMA levels were significantly higher in the CSE conditioned media compared with control media (p = 0.02) while NAC pre-treatment did not affect ADMA levels. Conclusions: CSE increased NO x which was partially reversed by NAC pre-treatment. ADMA levels were also increased after CSE exposure, suggesting that it activates the NO pathway via oxidative-stress while inhibition probably occurs via both ADMA and NOS.

Loss of secretin results in systemic and pulmonary hypertension with cardiopulmonary pathologies in mice

“…The disruption of the pulmonary bronchiolar epithelium with the loss or deformation of the shape of native club cells observed in SCT −/− mice may be due to the consequences of SCT deficiency on Cl − and HCO 3 − secretion in the lungs, as this is necessary for airway surface liquid (ASL) to maintain a healthy epithelium in the lungs 12 . This epithelium defect also contributes to the reduction of TGF-beta, iNOS, and VEGF expression in bronchiolar epithelium 54–56 found in SCT −/− mice. It was reported that the VEGF ameliorates PAH 57 and that VEGFR inhibition can cause PAH 58,59 ; as such, the bronchiolar epithelium depletion may cause VEGF and VEGFR reduction and then favour the occurrence of PAH in SCT −/− mice 54 .…”