ABSTRACT
Idiopathic pulmonary arterial hypertension (IPAH) is a fatal disease characterised by elevated blood pressure in the pulmonary circulation. Initial vasoconstriction, proliferation of pulmonary arterial smooth muscle cells (PASMC) and increased deposition of extracellular matrix (ECM) contribute to pathological remodelling of pulmonary arterioles in IPAH. Glycosaminoglycans (GAGs), components of the ECM, control cellular proliferation and differentiation, but their expression in IPAH remains elusive. In the present study, GAG expression was investigated in the lungs of patients with IPAH or control transplant donors, and expression and localisation of GAG-metabolising enzymes were analysed in vivo and in vitro. A significant increase in the expression of hyaluronic acid (HA) was detected in IPAH lungs, associated with increased hyaluronan synthase (Has)1 and decreased hyaluronoglucosaminidase 1 gene expression, as assessed by quantitative RT-PCR and Western blotting. HAS1 protein localised to PASMC in vivo and increased HA deposition was observed in remodelled pulmonary arteries in IPAH. Transforming growth factor-beta1, a profibrotic growth factor, led to increased HA secretion and HAS1 expression in primary PASMC. The results demonstrate an increased hyaluronic acid content in idiopathic pulmonary arterial hypertension lungs, associated with increased hyaluronan synthase 1 and decreased hyaluronoglucosaminidase 1 gene expression. Synergistic regulation of glycosaminoglycan-metabolising enzymes in favour of accumulation may, thus, regulate pathological vascular remodelling in idiopathic pulmonary arterial hypertension lungs.
Subject(s)
Hyaluronic Acid/metabolism , Hypertension, Pulmonary/metabolism , Pulmonary Artery/pathology , Adult , Cell Differentiation , Female , Fibrosis , Gene Expression Regulation, Enzymologic , Glycosaminoglycans/metabolism , Humans , Lung/metabolism , Lung/pathology , Male , Middle Aged , Myocytes, Smooth Muscle/metabolism , Pulmonary Artery/metabolism , Transforming Growth Factor beta1/metabolismABSTRACT
Mutations in genes encoding members of the transforming growth factor (TGF)-beta superfamily have been identified in idiopathic forms of pulmonary arterial hypertension (PAH). The current study examined whether perturbations to the TGF-beta/Smad2,3 signalling axis occurred in a monocrotaline (MCT) rodent model of experimental PAH. Expression of the TGF-beta signalling machinery was assessed in the lungs and kidneys of MCT-treated rodents with severe PAH by semi-quantitative reverse-transcription (RT)-PCR, real-time RT-PCR and immunoblotting. TGF-beta signalling was assessed in the lungs and in pulmonary artery smooth muscle cells (PASMC) from MCT-treated rodents by Smad2 phosphorylation, expression of the connective tissue growth factor gene, activation of the serpine promoter in a luciferase reporter system and by the induction of apoptosis. The expression of type1 TGF-beta receptor (TGFBR) activin-A receptor-like kinase1, TGFBR-2, TGFBR-3 (endoglin), Smad3 and Smad4; as well as TGF-beta signalling and TGF-beta-induced apoptosis, were dramatically reduced in the lungs and PASMC, but not the kidneys, of MCT-treated rodents that developed severe PAH. The current data indicate that the transforming growth factor-beta/Smad2,3 signalling axis is functionally impaired in monocrotaline-treated rodents with severe pulmonary arterial hypertension, underscoring the potential importance of transforming growth factor-beta/Smad2,3 signalling in the onset or development of pulmonary arterial hypertension.
