Inhibition of mechanosensitive signaling in myofibroblasts ameliorates experimental pulmonary fibrosis
Yong Zhou, Xiangwei Huang, Louise Hecker, Deepali Kurundkar, Ashish Kurundkar, Hui Liu, Tong-Huan Jin, Leena Desai, Karen Bernard, Victor J. Thannickal
Yong Zhou, Xiangwei Huang, Louise Hecker, Deepali Kurundkar, Ashish Kurundkar, Hui Liu, Tong-Huan Jin, Leena Desai, Karen Bernard, Victor J. Thannickal
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Research Article

Inhibition of mechanosensitive signaling in myofibroblasts ameliorates experimental pulmonary fibrosis

Abstract

Matrix stiffening and myofibroblast resistance to apoptosis are cardinal features of chronic fibrotic diseases involving diverse organ systems. The interactions between altered tissue biomechanics and cellular signaling that sustain progressive fibrosis are not well defined. In this study, we used ex vivo and in vivo approaches to define a mechanotransduction pathway involving Rho/Rho kinase (Rho/ROCK), actin cytoskeletal remodeling, and a mechanosensitive transcription factor, megakaryoblastic leukemia 1 (MKL1), that coordinately regulate myofibroblast differentiation and survival. Both in an experimental mouse model of lung fibrosis and in human subjects with idiopathic pulmonary fibrosis (IPF), we observed activation of the Rho/ROCK pathway, enhanced actin cytoskeletal polymerization, and MKL1 cytoplasmic-nuclear shuttling. Pharmacologic disruption of this mechanotransduction pathway with the ROCK inhibitor fasudil induced myofibroblast apoptosis through a mechanism involving downregulation of BCL-2 and activation of the intrinsic mitochondrial apoptotic pathway. Treatment with fasudil during the postinflammatory fibrotic phase of lung injury or genetic ablation of Mkl1 protected mice from experimental lung fibrosis. These studies indicate that targeting mechanosensitive signaling in myofibroblasts to trigger the intrinsic apoptosis pathway may be an effective approach for treatment of fibrotic disorders.

Authors

Yong Zhou, Xiangwei Huang, Louise Hecker, Deepali Kurundkar, Ashish Kurundkar, Hui Liu, Tong-Huan Jin, Leena Desai, Karen Bernard, Victor J. Thannickal

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Figure 6

Postinflammatory treatment with fasudil or genetic deletion of Mkl1 protects mice from bleomycin injury-induced lung fibrosis.

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Postinflammatory treatment with fasudil or genetic deletion of Mkl1 prot...
(A–C) C57BL/6 mice were administered bleomycin intratracheally at a dose of 5 U/kg. Control mice were given an equal volume of saline. At 14 days, mice were administered fasudil intraperitoneally at a dose of 25 mg/kg/d over 14 days. Control mice were injected with an equal volume of PBS. Lung tissues were harvested at 28 days and subjected to Masson trichrome staining for collagen (A), hydroxyproline content assay (B), and immunoblot analysis for α-SMA expression (C). (D–F) Mkl1–/– and Mkl1+/+ mice were administered bleomycin or saline as above. Mouse lung tissues were harvested at 28 days and subjected to Masson trichrome staining (D), hydroxyproline content assay (E), and α-SMA expression analysis (F). Graphs are mean ± SD (n = 5–7). Representative immunoblots are shown. Scale bars: 100 μm. **P < 0.01; ***P < 0.001.