Dominant negative mutation of the TGF-beta receptor blocks hypoxia-induced pulmonary vascular remodeling
ABSTRACT The present study utilized a novel transgenic mouse model that expresses an inducible dominant negative mutation of the transforming growth factor (TGF)-beta type II receptor (DnTGFbetaRII mouse) to test the hypothesis that TGF-beta signaling plays an important role in the pathogenesis of chronic hypoxia-induced increases in pulmonary arterial pressure and vascular and alveolar remodeling. Nine- to 10-wk-old male DnTGFbetaRII and control nontransgenic (NTG) mice were exposed to normobaric hypoxia (10% O2) or air for 6 wk. Expression of DnTGFbetaRII was induced by drinking 25 mM ZnSO4 water beginning 1 wk before hypoxic exposure. Hypoxia-induced increases in right ventricular pressure, right ventricular mass, pulmonary arterial remodeling, and muscularization were greatly attenuated in DnTGFbetaRII mice compared with NTG controls. Furthermore, the stimulatory effects of hypoxic exposure on pulmonary arterial and alveolar collagen content, appearance of alpha-smooth muscle actin-positive cells in alveolar parenchyma, and expression of extracellular matrix molecule (including collagen I and III, periostin, and osteopontin) mRNA in whole lung were abrogated in DnTGFbetaRII mice compared with NTG controls. Hypoxic exposure had no effect on systemic arterial pressure or heart rate in either strain. These data support the hypothesis that endogenous TGF-beta plays an important role in pulmonary vascular adaptation to chronic hypoxia and that disruption of TGF-beta signaling attenuates hypoxia-induced pulmonary hypertension, right ventricular hypertrophy, pulmonary arterial hypertrophy and muscularization, alveolar remodeling, and expression of extracellular matrix mRNA in whole lung.
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ABSTRACT: Muscular dystrophy (MD) is a disease characterized by skeletal muscle necrosis and the progressive accumulation of fibrotic tissue. While transforming growth factor (TGF)-β has emerged as central effector of MD and fibrotic disease, the cell types in diseased muscle that underlie TGFβ-dependent pathology have not been segregated. Here we generated transgenic mice with myofiber-specific inhibition of TGFβ signaling due to expression of a TGFβ type II receptor dominant negative (dnTGFβRII) truncation mutant. Expression of dnTGFβRII in myofibers mitigated the dystrophic phenotype observed in δ-sarcoglycan-null (Sgcd(-/-)) mice through a mechanism involving reduced myofiber membrane fragility. The dnTGFβRII transgene also reduced muscle injury and improved muscle regeneration after cardiotoxin injury, as well as increased satellite cell numbers and activity. An unbiased global expression analysis revealed a number of potential mechanisms for dnTGFβRII mediated protection, one of which was induction of the antioxidant proteins metallothionein (Mt). Indeed, TGFβ directly inhibited Mt gene expression in vitro, the dnTGFβRII transgene conferred protection against ROS accumulation in dystrophic muscle, and treatment with Mt mimetics protected skeletal muscle upon injury in vivo and improved the membrane stability of dystrophic myofibers. Hence, our results show that the myofibers are central mediators of the deleterious effects associated with TGFβ signaling in MD.Human Molecular Genetics 08/2014; 23(25). DOI:10.1093/hmg/ddu413 · 6.68 Impact Factor
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ABSTRACT: Mutations affecting transforming growth factor-beta (TGF-β) superfamily receptors, activin receptor-like kinase (ALK)-1, and endoglin (ENG) occur in patients with pulmonary arterial hypertension (PAH). To determine whether the TGF-β/ALK1/ENG pathway was involved in PAH, we investigated pulmonary TGF-β, ALK1, ALK5, and ENG expressions in human lung tissue and cultured pulmonary-artery smooth-muscle-cells (PA-SMCs) and pulmonary endothelial cells (PECs) from 14 patients with idiopathic PAH (iPAH) and 15 controls. Seeing that ENG was highly expressed in PEC, we assessed the effects of TGF-β on Smad1/5/8 and Smad2/3 activation and on growth factor production by the cells. Finally, we studied the consequence of ENG deficiency on the chronic hypoxic-PH development by measuring right ventricular (RV) systolic pressure (RVSP), RV hypertrophy, and pulmonary arteriolar remodeling in ENG-deficient (Eng+/-) and wild-type (Eng+/+) mice. We also evaluated the pulmonary blood vessel density, macrophage infiltration, and cytokine expression in the lungs of the animals. Compared to controls, iPAH patients had higher serum and pulmonary TGF-β levels and increased ALK1 and ENG expressions in lung tissue, predominantly in PECs. Incubation of the cells with TGF-β led to Smad1/5/8 phosphorylation and to a production of FGF2, PDGFb and endothelin-inducing PA-SMC growth. Endoglin deficiency protected mice from hypoxic PH. As compared to wild-type, Eng+/- mice had a lower pulmonary vessel density, and no change in macrophage infiltration after exposure to chronic hypoxia despite the higher pulmonary expressions of interleukin-6 and monocyte chemoattractant protein-1. The TGF-β/ALK1/ENG signaling pathway plays a key role in iPAH and experimental hypoxic PH via a direct effect on PECs leading to production of growth factors and inflammatory cytokines involved in the pathogenesis of PAH.PLoS ONE 06/2014; 9(6):e100310. DOI:10.1371/journal.pone.0100310 · 3.53 Impact Factor
Dataset: Final Sheikh et al