A critical role for the mTORC2 pathway in lung fibrosis

PLoS One. 2014 Aug 27;9(8):e106155. doi: 10.1371/journal.pone.0106155. eCollection 2014.

Abstract

A characteristic of dysregulated wound healing in IPF is fibroblastic-mediated damage to lung epithelial cells within fibroblastic foci. In these foci, TGF-β and other growth factors activate fibroblasts that secrete growth factors and matrix regulatory proteins, which activate a fibrotic cascade. Our studies and those of others have revealed that Akt is activated in IPF fibroblasts and it mediates the activation by TGF-β of pro-fibrotic pathways. Recent studies show that mTORC2, a component of the mTOR pathway, mediates the activation of Akt. In this study we set out to determine if blocking mTORC2 with MLN0128, an active site dual mTOR inhibitor, which blocks both mTORC1 and mTORC2, inhibits lung fibrosis. We examined the effect of MLN0128 on TGF-β-mediated induction of stromal proteins in IPF lung fibroblasts; also, we looked at its effect on TGF-β-mediated epithelial injury using a Transwell co-culture system. Additionally, we assessed MLN0128 in the murine bleomycin lung model. We found that TGF-β induces the Rictor component of mTORC2 in IPF lung fibroblasts, which led to Akt activation, and that MLN0128 exhibited potent anti-fibrotic activity in vitro and in vivo. Also, we observed that Rictor induction is Akt-mediated. MLN0128 displays multiple anti-fibrotic and lung epithelial-protective activities; it (1) inhibited the expression of pro-fibrotic matrix-regulatory proteins in TGF-β-stimulated IPF fibroblasts; (2) inhibited fibrosis in a murine bleomycin lung model; and (3) protected lung epithelial cells from injury caused by TGF-β-stimulated IPF fibroblasts. Our findings support a role for mTORC2 in the pathogenesis of lung fibrosis and for the potential of active site mTOR inhibitors in the treatment of IPF and other fibrotic lung diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzoxazoles / pharmacology*
  • Bleomycin
  • Carrier Proteins / antagonists & inhibitors
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Coculture Techniques
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Extracellular Matrix Proteins / antagonists & inhibitors
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / metabolism
  • Fibroblasts / drug effects*
  • Fibroblasts / metabolism
  • Fibroblasts / pathology
  • Gene Expression Regulation
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Mice
  • Multiprotein Complexes / antagonists & inhibitors
  • Multiprotein Complexes / genetics*
  • Multiprotein Complexes / metabolism
  • Protective Agents / pharmacology*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Pulmonary Fibrosis / chemically induced
  • Pulmonary Fibrosis / drug therapy*
  • Pulmonary Fibrosis / genetics
  • Pulmonary Fibrosis / pathology
  • Pyrimidines / pharmacology*
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Signal Transduction
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / genetics*
  • TOR Serine-Threonine Kinases / metabolism
  • Transforming Growth Factor beta / pharmacology

Substances

  • Benzoxazoles
  • Carrier Proteins
  • Extracellular Matrix Proteins
  • INK128
  • Multiprotein Complexes
  • Protective Agents
  • Pyrimidines
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Transforming Growth Factor beta
  • rictor protein, mouse
  • Bleomycin
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt

Grant support

This work was supported by a grant from the Takeda Corporation. The funders had no role in data collection, and analysis or decision to publish. They did provide MLN-0128, made suggestions about its formulation for animal studies, and proofread the manuscript.