Angiopoietin-like 4 confers resistance to hypoxia/serum deprivation-induced apoptosis through PI3K/Akt and ERK1/2 signaling pathways in mesenchymal stem cells

PLoS One. 2014 Jan 21;9(1):e85808. doi: 10.1371/journal.pone.0085808. eCollection 2014.

Abstract

Angiopoietin-like 4 (ANGPTL4) is a potential anti-apoptotic agent for various cells. We examined the protective effect of ANGPTL4 on hypoxia/serum deprivation (SD)-induced apoptosis of MSCs, as well as the possible mechanisms. MSCs were obtained from rat bone marrow and cultured in vitro. Apoptosis was induced by hypoxia/SD for up to 24 hr, and assessed by flow cytometry and TUNEL assay. Expression levels of Akt, ERK1/2, focal adhesion kinase (FAK), Src, Bcl-2, Bax, cytochrome C and cleaved caspase-3 were detected by Western blotting. Integrin β1 mRNA was detected by qRT-PCR. Mitochondrial membrane potential was assayed using a membrane-permeable dye. Hypoxia/SD-induced apoptosis was significantly attenuated by recombinant rat ANGPTL4 in a concentration dependent manner. Moreover, ANGPTL4 decreased the hypoxia/SD-induced caspase-3 cleavage and the cytochrome C release, but increased the Bcl-2/Bax ratio and the mitochondrial membrane potential. Decreased expression of integrin β1, the ANGPTL4 receptor was observed during hypoxia/SD conditions, however, such decrease was reversed by ANGPTL4. In addition, ANGPTL4 induced integrin β1-associated FAK and Src phosphorylation, which was blocked by anti-integrin β1 antibody. ANGPTL4 also reversed the hypoxia/SD-induced decrease of Akt and ERK 1/2 phosphorylation, and the effect of ANGPTL4 was abolished by inhibitors of either integrins, ERK1/2, or phosphatidylinositol 3-kinase (PI3K). Blocking integrinβ1, Akt or ERK largely attenuated anti-apoptotic effect of ANGPTL4. ANGPTL4 protects MSCs from hypoxia/SD-induced apoptosis by interacting with integrins to stimulate FAK complex, leading to downstream ERK1/2 and PI3K/Akt signaling pathways and mimicking the pathway in which MSCs contact with the extracellular matrix.

Publication types

  • Research Support, Non-U.S. Gov't
  • Retracted Publication

MeSH terms

  • Angiopoietin-Like Protein 4
  • Angiopoietins / metabolism*
  • Animals
  • Apoptosis* / drug effects
  • Cell Hypoxia / drug effects
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Culture Media, Serum-Free / pharmacology
  • Cytoprotection / drug effects
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Integrin beta1 / genetics
  • Integrin beta1 / metabolism
  • MAP Kinase Signaling System* / drug effects
  • Male
  • Mesenchymal Stem Cells / cytology*
  • Mesenchymal Stem Cells / drug effects
  • Mesenchymal Stem Cells / enzymology
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Phosphatidylinositol 3-Kinase / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Rats
  • Rats, Sprague-Dawley

Substances

  • ANGPTL4 protein, rat
  • Angiopoietin-Like Protein 4
  • Angiopoietins
  • Culture Media, Serum-Free
  • Integrin beta1
  • Phosphatidylinositol 3-Kinase
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases

Grants and funding

This study was supported by a grant from the National Natural Science Foundation of China (to BY, Grant No. 30871064). This work was also supported by grants from the Key Laboratory of Myocardial Ischemia Mechanism and Treatment (Harbin Medical University), Ministry of Education (to MH, Grant No: KF201315). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.