Pulmonary vascular smooth muscle cells remodeling and dysfunction in cystic fibrosis

Abstract

Background Pulmonary hypertension (PH) is a major feature of advanced cystic fibrosis (CF) and may lead to right ventricular dysfunction and cor pulmonale. Although PH is usually moderate in CF, its severity varies greatly across patients and its presence may negatively affect the prognosis. Extensive pulmonary vessel remodeling with muscularisation of the small arterioles are major pathological features of PH in CF. Although these structural changes are considered the major cause of the increase in pulmonary vascular resistance, their pathogenesis remains uncertain. The aim of this study was to determine whether the CFTR channel is present and affects functions of human pulmonary arteries smooth muscle cells (SMCs). Methods Lung and pulmonary arteries from CF and control patients were obtained from Hospital Foch, surgical department. Primary vascular smooth muscle cells (VSMCs) were isolated from the pulmonary artery (PA) of patients. Cytosolic Ca 2+ was measured using Fura-2 and dual-wavelength microfluorimetry. Protein expression was analyzed by immunofluorescence, immunoblot and RT-PCR analysis. Results Histological analysis revealed increased muscularisation of small pulmonary arteries from CF patients comparing to control patients (75 vs. 45%, n = 10, P 2+ ATPase 2a (SERCA2a). CFTR was detected in both control and CF PA-SMCs but exhibited differential intracellular localization. Particularly, in control PA-SMCs CFTR was localized within plasma membrane (PM) whereas in CF PA-SMCs CFTR was localized within the sarcoplasmic reticulum (SR), in line with previous observations in human airway epithelial cells (Front Pharmacol 2011;2:67). Accordingly, major alterations of calcium handling were detected in primary CF PA-SMCs. Particularly, total SR calcium content was increased in CF VSMCs, whereas PM Ca 2+ influx (store operated Ca 2+ entry [SOCE]) was decreased. Furthermore, primary CF PA-SMCs were poorly sensitive to Thrombin (inductor of proliferation) but highly sensitive to serotonin (inductor of contraction). In opposite to the brief increase in cytosolic Ca 2+ observed in control cells, in CF PA-SMCs serotonin-induced a sustained long-lasting oscillatory Ca 2+ transient, suggesting establishment of “membrane oscillator” during whole period of occupancy of serotonin receptor. Conclusions Relocalization of ΔCFTR to RS in PA-SMCs results in major alterations of Ca 2+ handling favoring hypercontractility of PA-SMCs in CF patients.