MEK-ERK Pathway Modulation Ameliorates Pulmonary Fibrosis Associated with Epidermal Growth Factor Receptor Activation

Department of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 3.99). 03/2012; 46(3):380-8. DOI: 10.1165/rcmb.2011-0237OC
Source: PubMed


Pulmonary fibrosis remains a significant public health burden with no proven therapies. The mitogen-activated protein kinase (MAPK)/MAPK kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling cascade is a major pathway controlling cellular processes associated with fibrogenesis, including growth, proliferation, and survival. Activation of the MAPK/ERK pathway is detected in the lungs of human fibrosis samples; however, the effect of modulating the pathway in vivo is unknown. Overexpression of transforming growth factor (TGF)-α in the lung epithelium of transgenic mice causes a progressive pulmonary fibrosis associated with increased MEK/ERK activation localized primarily in mesenchymal cells. To determine the role of the MEK pathway in the induction of TGF-α-induced lung fibrosis, TGF-α was overexpressed for 4 weeks while mice were simultaneously treated with the specific MEK inhibitor, ARRY-142886 (ARRY). Treatment with ARRY prevented increases in lung cell proliferation and total lung collagen, attenuated production of extracellular matrix genes, and protected mice from changes in lung function. ARRY administered as a rescue treatment after fibrosis was already established inhibited fibrosis progression, as assessed by lung histology, changes in body weights, extracellular matrix gene expression, and lung mechanics. These findings demonstrate that MEK inhibition prevents progression of established fibrosis in the TGF-α model, and provides proof of concept of targeting the MEK pathway in fibrotic lung disease.

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    • "Several growth factors and their downstream signaling pathways that maintain tumors are also activated in both human and mouse models of pulmonary fibrosis [15]–[18]. Receptor tyrosine kinases (RTK) are high-affinity cell-surface receptors for many polypeptide growth factors and cytokines, including ligands of the epidermal growth factor receptor (EGFR) and platelet-derived growth factor (PDGF), basic fibroblast growth factor, and vascular endothelial growth factor receptors [19], [20]. Following RTK activation, the cascade of subsequent signaling events activates multiple kinase pathways, including both the mitogen activated protein kinases (MAPK) and phosphatidylinositide 3-kinase (PI3K) pathways [9]. "
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    ABSTRACT: Pulmonary fibrosis is often triggered by an epithelial injury resulting in the formation of fibrotic lesions in the lung, which progress to impair gas exchange and ultimately cause death. Recent clinical trials using drugs that target either inflammation or a specific molecule have failed, suggesting that multiple pathways and cellular processes need to be attenuated for effective reversal of established and progressive fibrosis. Although activation of MAPK and PI3K pathways have been detected in human fibrotic lung samples, the therapeutic benefits of in vivo modulation of the MAPK and PI3K pathways in combination are unknown. Overexpression of TGFα in the lung epithelium of transgenic mice results in the formation of fibrotic lesions similar to those found in human pulmonary fibrosis, and previous work from our group shows that inhibitors of either the MAPK or PI3K pathway can alter the progression of fibrosis. In this study, we sought to determine whether simultaneous inhibition of the MAPK and PI3K signaling pathways is a more effective therapeutic strategy for established and progressive pulmonary fibrosis. Our results showed that inhibiting both pathways had additive effects compared to inhibiting either pathway alone in reducing fibrotic burden, including reducing lung weight, pleural thickness, and total collagen in the lungs of TGFα mice. This study demonstrates that inhibiting MEK and PI3K in combination abolishes proliferative changes associated with fibrosis and myfibroblast accumulation and thus may serve as a therapeutic option in the treatment of human fibrotic lung disease where these pathways play a role.
    PLoS ONE 01/2014; 9(1):e86536. DOI:10.1371/journal.pone.0086536 · 3.23 Impact Factor
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    • "ERK is involved in the regulation of lung angiogenesis and inflammation. Recent reports have shown that ERK1/2 activation is increased in an animal model of pulmonary fibrosis, and inhibiting ERK1/2 activation suppresses lung collagen deposition and inflammation and consequently ameliorates pulmonary fibrosis [44,45]. Western blots of human lung biopsy samples also demonstrate significantly increased ERK1/2 signalling in IPF samples compared with normal controls [46]. "
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    ABSTRACT: Background Recent evidence has demonstrated the role of angiogenesis in the pathogenesis of pulmonary fibrosis. Endostatin, a proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis. The aim of our study was to assess whether endostatin has beneficial effects on bleomycin (BLM)-induced pulmonary fibrosis in rats. Methods The rats were randomly divided into five experimental groups: (A) saline only, (B) BLM only, (C) BLM plus early endostatin treatment, (D) BLM plus late endostatin treatment, and (F) BLM plus whole-course endostatin treatment. We investigated the microvascular density (MVD), inflammatory response and alveolar epithelial cell apoptosis in rat lungs in each group at different phases of disease development. Results Early endostatin administration attenuated fibrotic changes in BLM-induced pulmonary fibrosis in rats. Endostatin treatment decreased MVD by inhibiting the expression of VEGF/VEGFR-2 (Flk-1) and the activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). Endostatin treatment also decreased the number of inflammatory cells infiltrating the bronchoalveolar lavage fluid during the early inflammatory phase of BLM-induced pulmonary fibrosis. In addition, the levels of tumour necrosis factor-α (TNF-α) and transforming growth factor β1 (TGF-β1) were reduced by endostatin treatment. Furthermore, endostatin decreased alveolar type II cell apoptosis and had an epithelium-protective effect. These might be the mechanism underlying the preventive effect of endostatin on pulmonary fibrosis. Conclusions Our findings suggest that endostatin treatment inhibits the increased MVD, inflammation and alveolar epithelial cell apoptosis, consequently ameliorating BLM-induced pulmonary fibrosis in rats.
    Respiratory research 05/2013; 14(1):56. DOI:10.1186/1465-9921-14-56 · 3.09 Impact Factor
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    • "To induce Fizz1 expression bitransgenic mice were administered doxycycline (Dox) food (62.5 mg/kg). The fold increase in detectable Fizz1 was determined by comparing pixels from the off Dox and On Dox lanes in Figure 1 using a phosphorimager and ImageQuant software [23]. "
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    ABSTRACT: Resistin-like molecule alpha or found in inflammatory zone protein (Fizz1) is increased in pulmonary epithelial cells and also in limited amounts by other lung cells during various lung injuries and fibrosis. However, the direct role of Fizz1 produced in the pulmonary epithelium has not been determined. Fizz1 Transgenic mice (CCSP/Fizz1) were generated that overexpress Fizz1 in the lung epithelium under the control of a doxycycline (Dox) inducible lung epithelial cell specific promoter Scgb1a1 (Clara cell secretory protein, CCSP). Histology and FACS analysis of lung cells were used to identify the direct effects of Fizz1 in the transgenic mice (Dox treated) when compared with control (CCSP/-) mice. Intratracheal bleomycin sulfate or silica in saline and saline alone were used to study the role of Fizz1 during bleomycin- and silica-induced pulmonary fibrosis in CCSP/Fizz1 and CCSP/- mice. Weight change, pulmonary inflammation, and fibrosis were assessed 10 days post bleomycin or 28 days post silica challenge. When CCSP/Fizz1 mice were fed Dox food, elevated Fizz1 protein was detected in lung homogenates by western blot. Lungs of mice in which Fizz1 was induced in the epithelium contained increased lung cells staining for CD11c and F4/80 by FACS analysis consistent with increased dendritic cells however, no changes were observed in the percentage of interstitial macrophages compared to CCSP/- controls. No significant changes were found in the lung histology of CCSP/Fizz1 mice after up to 8 weeks of overexpression compared to CCSP/- controls. Overexpression of Fizz1 prior to challenge or following challenge with bleomycin or silica did not significantly alter airway inflammation or fibrosis compared to control mice. The current study demonstrates that epithelial cell derived Fizz1 is sufficient to increase the bone-marrow derived dendritic cells in the lungs, but it is not sufficient to cause lung fibrosis or alter chemical or particle-induced fibrosis.
    Respiratory research 06/2012; 13(1):51. DOI:10.1186/1465-9921-13-51 · 3.09 Impact Factor
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