Science and Research

Tubastatin ameliorates pulmonary fibrosis by targeting the TGFbeta-PI3K-Akt pathway

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal disease. Histone deacetylase 6 (HDAC6) alters function and fate of various proteins via deacetylation of lysine residues, and is implicated in TGF-beta1-induced EMT (epithelial-mesenchymal transition). However, the role of HDAC6 in pulmonary fibrosis is unknown. METHODS: HDAC6 expression in IPF and control lungs was assessed by quantitative real-time PCR (qRT-PCR) and immunoblots. Lung fibroblasts were treated with TGF-beta1 +/- HDAC6 inhibitors (Tubacin, Tubastatin, ACY1215, or MC1568), and fibrotic markers such as type I collagen were assessed using qRT-PCR and immunoblots. Mice were treated with bleomycin (oropharyngeal aspiration; single dose) +/- Tubastatin (intraperitoneally injection; daily for 21 days), and lung collagen expression was gauged using immunoblots and trichrome staining. In a separate experiment, HDAC6 wild-type (WT) and knockout (KO) mice were administered bleomycin, and lungs were evaluated in the same manner. RESULTS: HDAC6 expression was deregulated in IPF lungs. Among the HDAC6 inhibitors tested, only Tubastatin significantly repressed TGF-beta1-induced expression of type-1 collagen in lung fibroblasts, and this finding was coupled with decreased Akt phosphorylation and increased Akt-PHLPP (PH domain and Leucine rich repeat Protein Phosphatase) association. Tubastatin repressed TGF-beta1-induced S6K phosphorylation, HIF-1alpha expression, and VEGF expression. Tubastatin also repressed TGF-beta1-induced inhibition of LC3B-II (a marker of autophagosome formation). In bleomycin-treated mouse lungs, HDAC6 expression was increased, and Tubastatin repressed type-1 collagen expression. However, in HDAC6 KO mice, bleomycin-induced type-1 collagen expression was not repressed compared to WT mice. Knockdown of HDAC6, as well as HDAC10, another potential Tubastatin target, did not inhibit TGF-beta1-induced collagen expression in lung fibroblasts. CONCLUSIONS: HDAC6 expression is altered during lung fibrogenesis. Tubastatin represses TGF-beta1-induced collagen expression, by diminishing Akt phosphorylation and regulating downstream targets such as HIF-1alpha-VEGF axis and autophagy. Tubastatin-treated WT mice are protected against bleomycin-induced fibrosis, but HDAC6 KO mice are not. Our data suggest that Tubastatin ameliorates pulmonary fibrosis, by targeting the TGFbeta-PI3K-Akt pathway, likely via an HDAC6-independent mechanism.

  • Saito, S.
  • Zhuang, Y.
  • Shan, B.
  • Danchuk, S.
  • Luo, F.
  • Korfei, M.
  • Guenther, A.
  • Lasky, J. A.

Keywords

  • Aged
  • Aged, 80 and over
  • Animals
  • Autophagosomes/drug effects/metabolism
  • Autophagy/drug effects
  • Bleomycin
  • Collagen Type I/metabolism
  • Female
  • Fibroblasts/drug effects/metabolism
  • Histone Deacetylase 6
  • Histone Deacetylases/genetics/metabolism
  • Humans
  • Hydroxamic Acids/pharmacology/*therapeutic use
  • Hypoxia-Inducible Factor 1, alpha Subunit/metabolism
  • Idiopathic Pulmonary Fibrosis/*drug therapy/genetics/*metabolism/pathology
  • Indoles/pharmacology/*therapeutic use
  • Lung/metabolism/pathology
  • Male
  • Mechanistic Target of Rapamycin Complex 1
  • Mice, Knockout
  • Middle Aged
  • Multiprotein Complexes/metabolism
  • Nuclear Proteins/metabolism
  • Phosphatidylinositol 3-Kinases/*metabolism
  • Phosphoprotein Phosphatases/metabolism
  • Phosphorylation/drug effects
  • Proto-Oncogene Proteins c-akt/*metabolism
  • RNA, Messenger/genetics/metabolism
  • Ribosomal Protein S6 Kinases/metabolism
  • Signal Transduction/*drug effects
  • TOR Serine-Threonine Kinases/metabolism
  • Transforming Growth Factor beta/*metabolism/pharmacology
  • Tubulin/metabolism
  • Vascular Endothelial Growth Factor A/metabolism
Publication details
DOI: 10.1371/journal.pone.0186615
Journal: PloS one
Pages: e0186615 
Number: 10
Work Type: Original
Location: UGMLC
Disease Area: DPLD
Partner / Member: JLU
Access-Number: 29045477

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