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JAK2 participates in PA remodelling and tension and may be an attractive target to treat IPF associated to PH.

Keywordspulmonary artery endothelial cells; endothelin receptor B; bosentan; cigarette smoke; endothelial dysfunction ---------------------------------------------------------------- BACKGROUND AND PURPOSEPulmonary arteries from smokers and chronic obstructive pulmonary disease patients show abnormal endothelium-dependent vascular reactivity. We studied the effect of cigarette smoke extract (CSE) on endothelin receptor B (ETB) expression in human pulmonary artery endothelial cells (HPAECs) and its role in endothelial dysfunction. EXPERIMENTAL APPROACHETB receptor expression was measured by real time RT-PCR, Western blot and immunofluorescence. Cell contraction, intracellular Ca 2+ , F/G-actin, RhoA activity, myosin light chain phosphorylation, ET, NO, thromboxane (Tx)A2 and reactive oxygen species (ROS) were measured by traction microscopy, fluorescence microscopy, phalloidin fluorescence, colorimetric assay, Western blot, ELISA and DCFDA fluorescence respectively. KEY RESULTSCigarette smoke extract dose-dependently increased ETB receptor expression in HPAECs after 24 h incubation. CSE-induced ETB expression was attenuated by bosentan, the ETB receptor antagonist BQ788, the Rho kinase antagonist Y27632 and the antioxidant N-acetylcysteine. A monoclonal antibody to ET-1 prevented CSE-induced ETB receptor overexpression. Twenty-four hour exposure to ET-1 dose-dependently increased ETB receptor expression, mimicking the effect of CSE. CSE-induced ETB receptor overexpression caused greater cell contraction; increased intracellular Ca 2+ ; increased F/G-actin and RhoA activity; increased myosin light chain phosphorylation; augmented TxA2 and ROS production; and decreased NO after acute ET-1 (10 nM). These effects were attenuated by bosentan, BQ788, Y27632 and N-acetylcysteine. CONCLUSIONS AND IMPLICATIONCigarette smoke extract induced ETB receptor overexpression by a feed forward mechanism mediated partly by ET release, promoting HPAEC dysfunction and attenuated by ETB receptor blockade, Rho kinase and ROS inhibition. These results provide support for the use of bosentan in CS-related endothelial dysfunction.

Sildenafil improves the 6-min walking distance in patients with idiopathic pulmonary fibrosis (IPF) and right-sided ventricular systolic dysfunction.We analysed the previously unexplored role of sildenafil on vasoconstriction and remodelling of pulmonary arteries from patients with IPF and pulmonary hypertension (PH) ex vivo Pulmonary arteries from 18 donors without lung disease, nine IPF, eight PH+IPF and four PH patients were isolated to measure vasodilator and anti-contractile effects of sildenafil in isometric organ bath. Ventilation/perfusion was explored in an animal model of bleomycin lung fibrosis.Sildenafil relaxed serotonin (5-HT) pre-contracted pulmonary arteries in healthy donors and IPF patients and, to a lesser extent, in PH+IPF and PH. Sildenafil inhibited 5-HT dose-response contraction curve mainly in PH+IPF and PH, but not in healthy donors. Sildenafil did not impair the ventilation/perfusion mismatching induced by bleomycin. Pulmonary arteries from PH+IPF patients showed a marked expression of phosphodiesterse-5 and extracellular matrix components. Sildenafil inhibited pulmonary artery endothelial and smooth muscle cell to mesenchymal transition by inhibition of extracellular regulated kinases 1 and 2 (ERK1/2) and SMAD3 phosphorylation.These results suggest an absence of direct relaxant effect and a prominent anti-contractile and anti-remodelling role of sildenafil in PH+IPF pulmonary arteries that could explain the beneficial effects of sildenafil in IPF with PH phenotype.

1 Cysteinyl-leukotrienes cause contractions and/or relaxations of human isolated pulmonary vascular preparations. Although, the localization and nature of the receptors through which these effects are mediated have not been fully characterized, some effects are indirect and not mediated via the welldescribed LT1 receptor. 2 In human pulmonary veins (HPV) with an intact endothelium, leukotriene D4 (LTD4) induced contraction above basal tone. This response was observed at lower concentrations of LTD4 in the presence of nitric oxide synthase inhibitor N4-nitro-L-arginine (L-NOARG). Contractions (in the absence and presence of L-NOARG) were partially blocked by the LT, antagonists (MK 571 and ICI 198615). 3 LTD4 relaxed HPV previously contracted with noradrenaline. This relaxation was potentiated by LT1 antagonists, but was abolished by removal of the endothelium. LTD4 also relaxed human pulmonary arteries (HPA) precontracted with noradrenaline but this effect was not modified by LT, antagonists. 4 The results suggest that contraction of endothelium-intact HPV by LTD4 is partially mediated via LT, receptors. Further, in endothelium-intact HPV, this contraction was opposed by a relaxation induced by LTD4, dependent on the release of nitric oxide, which was mediated, at least in part, via a non-LT, receptor. In addition, LTD4 relaxation on contracted HPA was not mediated by LT, receptors. 5 The mechanical effects of LTD4 on human pulmonary vasculature are complex and involve both direct and indirect mechanisms mediated via at least two types of cysteinyl-leukotriene receptors.