Transglutaminase 2 and Its Role in Pulmonary Fibrosis

University of Rochester, Division of Pulmonary and Critical Care Medicine, Department of Medicine, Rochester, NY 14642, USA.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 06/2011; 184(6):699-707. DOI: 10.1164/rccm.201101-0013OC
Source: PubMed


Idiopathic pulmonary fibrosis (IPF) is a deadly progressive disease with few treatment options. Transglutaminase 2 (TG2) is a multifunctional protein, but its function in pulmonary fibrosis is unknown.
To determine the role of TG2 in pulmonary fibrosis.
The fibrotic response to bleomycin was compared between wild-type and TG2 knockout mice. Transglutaminase and transglutaminase-catalyzed isopeptide bond expression was examined in formalin-fixed human lung biopsy sections by immunohistochemistry from patients with IPF. In addition, primary human lung fibroblasts were used to study TG2 function in vitro.
TG2 knockout mice developed significantly reduced fibrosis compared with wild-type mice as determined by hydroxyproline content and histologic fibrosis score (P < 0.05). TG2 expression and activity are increased in lung biopsy sections in humans with IPF compared with normal control subjects. In vitro overexpression of TG2 led to increased fibronectin deposition, whereas transglutaminase knockdown led to defects in contraction and adhesion. The profibrotic cytokine transforming growth factor-β causes an increase in membrane-localized TG2, increasing its enzymatic activity.
TG2 is involved in pulmonary fibrosis in a mouse model and in human disease and is important in normal fibroblast function. With continued research on TG2, it may offer a new therapeutic target.

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Available from: Siiri E Iismaa, Sep 30, 2015
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    • "In addition, the authors reported that fibroblast-derived TG2, acting downstream of TGFβ, was also important in the effector phase of fibrogenesis [56]. TG2 knockout mice were protected from bleomycin-induced lung fibrosis, and TG2 expression and activity were increased in patients with IPF versus normal controls [57]. "
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    ABSTRACT: Repairing damaged tissues is an essential homeostatic mechanism that enables clearance of dead or damaged cells after injury, and the maintenance of tissue integrity. However, exaggeration of this process in the lung can lead to the development of fibrotic scar tissue. This is characterized by excessive accumulation of extracellular matrix (ECM) components such as fibronectin, proteoglycans, hyaluronic acid, and interstitial collagens. After tissue injury, or a breakdown of tissue integrity, a cascade of events unfolds to maintain normal tissue homeostasis. Inflammatory mediators are released from injured epithelium, leading to both platelet activation and inflammatory cell migration. Inflammatory cells are capable of releasing multiple pro-inflammatory and fibrogenic mediators such as transforming growth factor (TGF)beta and interleukin (IL)-13, which can trigger myofibroblast proliferation and recruitment. The myofibroblast population is also expanded as a result of epithelial cells undergoing epithelial-to-mesenchymal transition and of the activation of resident fibroblasts, leading to ECM deposition and tissue remodeling. In the healthy lung, wound healing then proceeds to restore the normal architecture of the lung; however, fibrosis can develop when the wound is severe, the tissue injury persists, or the repair process becomes dysregulated. Understanding the processes regulating aberrant wound healing and the matrix in the chronic fibrotic lung disease idiopathic pulmonary fibrosis (IPF), is key to identifying new treatments for this chronic debilitating disease. This review focuses primarily on the emerging role of enzymes in the lungs of patients with IPF. Elevated expression of a number of enzymes that can directly modulate the ECM has been reported, and recent data indicates that modulating the activity of these enzymes can have a downstream effect on fibrotic tissue remodeling.
    Fibrogenesis & Tissue Repair 11/2013; 6(1):20. DOI:10.1186/1755-1536-6-20
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    • "Moreno reported that AF-1 can inhibit the activity of transglutaminase-2 (TG-2) [36]. TG-2 is a multifunctional protein that plays an important role in bleomycin-induced pulmonary fibrosis [37,38]. Overexpression of TG-2 increases fibronectin deposition and matrix organization in vitro. "
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    ABSTRACT: Antiflammin-1 (AF-1), a derivative of uteroglobin (UG), is a synthetic nonapeptide with diverse biological functions. In the present study, we investigated whether AF-1 has a protective effect against bleomycin-induced pulmonary fibrosis. C57BL/6 mice were injected with bleomycin intratracheally to create an animal model of bleomycin-induced pulmonary fibrosis. On Day 7 and Day 28, we examined the anti-inflammatory effect and antifibrotic effect, respectively, of AF-1 on the bleomycin-treated mice. The effects of AF-1 on the transforming growth factor-beta 1 (TGF-beta1)-induced proliferation of murine lung fibroblasts (NIH3T3) were examined by a bromodeoxycytidine (BrdU) incorporation assay and cell cycle analysis. Severe lung inflammation and fibrosis were observed in the bleomycin-treated mice on Day 7 and Day 28, respectively. Administration of AF-1 significantly reduced the number of neutrophils in the bronchoalveolar lavage fluid (BALF) and the levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1beta) in the lung homogenates on Day 7. Histological examination revealed that AF-1 markedly reduced the number of infiltrating cells on Day 7 and attenuated the collagen deposition and destruction of lung architecture on Day 28. The hydroxyproline (HYP) content was significantly decreased in the AF-1-treated mice. In vitro, AF-1 inhibited the TGF-beta1-induced proliferation of NIH3T3 cells, which was mediated by the UG receptor. AF-1 has anti-inflammatory and antifibrotic actions in bleomycin-induced lung injury. We propose that the antifibrotic effect of AF-1 might be related to its suppression of fibroblast growth in bleomycin-treated lungs and that AF-1 has potential as a new therapeutic tool for pulmonary fibrosis.
    Respiratory research 10/2013; 14(1):101. DOI:10.1186/1465-9921-14-101 · 3.09 Impact Factor
    • "Sections of 5 μm thickness were cut, mounted on slides, and stained with Gomori Trichrome (Richard Allen brand, Thermo Fisher Scientific Inc., Pittsburgh, PA) using the manufacturer's suggested protocol. The histology slides were scored for fibrosis by a blinded pathologist on the scale of 0 (minimum) to 4 (maximum) as described previously [14]. Immunohistochemistry was performed as described [13] using primary antibodies to αSMA (Sigma-Aldrich, St. Louis, MO). "
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    PLoS ONE 05/2013; 8(5):e63798. DOI:10.1371/journal.pone.0063798 · 3.23 Impact Factor
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