scholarly journals Hypoxia induces downregulation of PPAR-γ in isolated pulmonary arterial smooth muscle cells and in rat lung via transforming growth factor-β signaling

2011 ◽  
Vol 301 (6) ◽  
pp. L899-L907 ◽  
Author(s):  
Kaizheng Gong ◽  
Dongqi Xing ◽  
Peng Li ◽  
Baran Aksut ◽  
Namasivayam Ambalavanan ◽  
...  
Keyword(s):  
Growth Factor ◽  
Vascular Remodeling ◽  
Chronic Hypoxia ◽  
Transforming Growth Factor ◽  
Muscle Cells ◽  
Transforming Growth Factor Β ◽  
Hypoxic Stress ◽  
Ppar Γ ◽  
Β Receptor ◽  
Tgf Β1

Chronic hypoxia activates transforming growth factor-β (TGF-β) signaling and leads to pulmonary vascular remodeling. Pharmacological activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) has been shown to prevent hypoxia-induced pulmonary hypertension and vascular remodeling in rodent models, suggesting a vasoprotective effect of PPAR-γ under chronic hypoxic stress. This study tested the hypothesis that there is a functional interaction between TGF-β/Smad signaling pathway and PPAR-γ in isolated pulmonary artery small muscle cells (PASMCs) under hypoxic stress. We observed that chronic hypoxia led to a dramatic decrease of PPAR-γ protein expression in whole lung homogenates (rat and mouse) and hypertrophied pulmonary arteries and isolated PASMCs. Using a transgenic model of mouse with inducible overexpression of a dominant-negative mutant of TGF-β receptor type II, we demonstrated that disruption of TGF-β pathway significantly attenuated chronic hypoxia-induced downregulation of PPAR-γ in lung. Similarly, in isolated rat PASMCs, antagonism of TGF-β signaling with either a neutralizing antibody to TGF-β or the selective TGF-β receptor type I inhibitor SB431542 effectively attenuated hypoxia-induced PPAR-γ downregulation. Furthermore, we have demonstrated that TGF-β1 treatment suppressed PPAR-γ expression in PASMCs under normoxia condition. Chromatin immunoprecipitation analysis showed that TGF-β1 treatment significantly increased binding of Smad2/3, Smad4, and the transcriptional corepressor histone deacetylase 1 to the PPAR-γ promoter in PASMCs. Conversely, treatment with the PPAR-γ agonist rosiglitazone attenuated TGF-β1-induced extracellular matrix molecule expression and growth factor in PASMCs. These data provide strong evidence that activation of TGF-β/Smad signaling, via transcriptional suppression of PPAR-γ expression, mediates chronic hypoxia-induced downregulation of PPAR-γ expression in lung.

scholarly journals Interactions between Growth Factors and Integrins: Latent Forms of Transforming Growth Factor-β Are Ligands for the Integrin αvβ1

1998 ◽  
Vol 9 (9) ◽  
pp. 2627-2638 ◽  
Author(s):  
John S. Munger ◽  
John G. Harpel ◽  
Filippo G. Giancotti ◽  
Daniel B. Rifkin
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
A549 Cells ◽  
Transforming Growth Factor Β ◽  
Mutant Form ◽  
Rgd Sequence ◽  
Β Receptor ◽  
Coated Surfaces ◽  
Β Function ◽  
Tgf Β1

The multipotential cytokine transforming growth factor-β (TGF-β) is secreted in a latent form. Latency results from the noncovalent association of TGF-β with its processed propeptide dimer, called the latency-associated peptide (LAP); the complex of the two proteins is termed the small latent complex. Disulfide bonding between LAP and latent TGF-β–binding protein (LTBP) produces the most common form of latent TGF-β, the large latent complex. The extracellular matrix (ECM) modulates the activity of TGF-β. LTBP and the LAP propeptides of TGF-β (isoforms 1 and 3), like many ECM proteins, contain the common integrin-binding sequence RGD. To increase our understanding of latent TGF-β function in the ECM, we determined whether latent TGF-β1 interacts with integrins. A549 cells adhered and spread on plastic coated with LAP, small latent complex, and large latent complex but not on LTBP-coated plastic. Adhesion was blocked by an RGD peptide, and cells were unable to attach to a mutant form of recombinant LAP lacking the RGD sequence. Adhesion was also blocked by mAbs to integrin subunits αv and β1. We purified LAP-binding integrins from extracts of A549 cells using LAP bound to Sepharose. αvβ1 eluted with EDTA. After purification in the presence of Mn2+, a small amount of αvβ5 was also detected. A549 cells migrated equally on fibronectin- and LAP-coated surfaces; migration on LAP was αvβ1 dependent. These results establish αvβ1 as a LAP-β1 receptor. Interactions between latent TGF-β and αvβ1 may localize latent TGF-β to the surface of specific cells and may allow the TGF-β1 gene product to initiate signals by both TGF-β receptor and integrin pathways.

scholarly journals Transforming growth factor-β plays divergent roles in modulating vascular remodeling, inflammation, and pulmonary fibrosis in a murine model of scleroderma

2017 ◽  
Vol 312 (1) ◽  
pp. L22-L31 ◽  
Author(s):  
Kazuyuki Tsujino ◽  
Nilgun Isik Reed ◽  
Amha Atakilit ◽  
Xin Ren ◽  
Dean Sheppard
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Smooth Muscle Cells ◽  
Vascular Remodeling ◽  
Transforming Growth Factor ◽  
Muscle Cells ◽  
Transforming Growth Factor Β ◽  
Tgfβ Signaling ◽  
Pulmonary Vascular Remodeling ◽  
Global Inhibition

The efficacy and feasibility of targeting transforming growth factor-β (TGFβ) in pulmonary fibrosis and lung vascular remodeling in systemic sclerosis (SSc) have not been well elucidated. In this study we analyzed how blocking TGFβ signaling affects pulmonary abnormalities in Fos-related antigen 2 (Fra-2) transgenic (Tg) mice, a murine model that manifests three important lung pathological features of SSc: fibrosis, inflammation, and vascular remodeling. To interrupt TGFβ signaling in the Fra-2 Tg mice, we used a pan-TGFβ-blocking antibody, 1D11, and Tg mice in which TGFβ receptor type 2 ( Tgfbr2) is deleted from smooth muscle cells and myofibroblasts (α-SMA-CreER; Tgfbr2 flox/flox). Global inhibition of TGFβ by 1D11 did not ameliorate lung fibrosis histologically or biochemically, whereas it resulted in a significant increase in the number of immune cells infiltrating the lungs. In contrast, 1D11 treatment ameliorated the severity of pulmonary vascular remodeling in Fra-2 Tg mice. Similarly, genetic deletion of Tgfbr2 from smooth muscle cells resulted in improvement of pulmonary vascular remodeling in the Fra-2 Tg mice, as well as a decrease in the number of Ki67-positive vascular smooth muscle cells, suggesting that TGFβ signaling contributes to development of pulmonary vascular remodeling by promoting the proliferation of vascular smooth muscle cells. Deletion of Tgfbr2 from α-smooth muscle actin-expressing cells had no effect on fibrosis or inflammation in this model. These results suggest that efforts to target TGFβ in SSc will likely require more precision than simply global inhibition of TGFβ function.

scholarly journals Disruption of Transforming Growth Factor β Signaling by a Novel Ligand-dependent Mechanism

2002 ◽  
Vol 195 (10) ◽  
pp. 1247-1255 ◽  
Author(s):  
Tania Fernandez ◽  
Stephanie Amoroso ◽  
Shellyann Sharpe ◽  
Gary M. Jones ◽  
Valery Bliskovski ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Surface Expression ◽  
Dominant Negative ◽  
Cell Surface Expression ◽  
Receptor Complex ◽  
Β Receptor ◽  
Tgf Β1

Transforming growth factor (TGF)-β is the prototype in a family of secreted proteins that act in autocrine and paracrine pathways to regulate cell development and function. Normal cells typically coexpress TGF-β receptors and one or more isoforms of TGF-β, thus the synthesis and secretion of TGF-β as an inactive latent complex is considered an essential step in regula-ting the activity of this pathway. To determine whether intracellular activation of TGF-β results in TGF-β ligand–receptor interactions within the cell, we studied pristane-induced plasma cell tumors (PCTs). We now demonstrate that active TGF-β1 in the PCT binds to intracellular TGF-β type II receptor (TβRII). Disruption of the expression of TGF-β1 by antisense TGF-β1 mRNA restores localization of TβRII at the PCT cell surface, indicating a ligand-induced impediment in receptor trafficking. We also show that retroviral expression of a truncated, dominant-negative TβRII (dnTβRII) effectively competes for intracellular binding of active ligand in the PCT and restores cell surface expression of the endogenous TβRII. Analysis of TGF-β receptor–activated Smad2 suggests the intracellular ligand–receptor complex is not capable of signaling. These data are the first to demonstrate the formation of an intracellular TGF-β–receptor complex, and define a novel mechanism for modulating the TGF-β signaling pathway.

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