The role of tumour suppressor PDCD4 in beta cell death in hypoxia

PLoS One. 2017 Jul 27;12(7):e0181235. doi: 10.1371/journal.pone.0181235. eCollection 2017.

Abstract

Objective: Hypoxia is known to induce pancreatic beta cell dysfunction and apoptosis. Changes in Programmed Cell Death Gene 4 (PDCD4) expression have previously been linked with beta cell neogenesis and function. Our aim was to investigate the effects of hypoxia on cell viability, PDCD4 expression and subcellular localisation.

Methods: MIN6 beta cells and ARIP ductal cells were exposed to 1% (hypoxia) or 21% O2 (normoxia) for 12 or 24 hours. MTT assay, HPI staining, scanning electron microscopy, western blotting and immunocytochemistry analyses were performed to determine the effect of hypoxia on cell viability, morphology and PDCD4 expression.

Results: 24 hour exposure to hypoxia resulted in ~70% loss of beta cell viability (P<0.001) compared to normoxia. Both HPI staining and SEM analysis demonstrated beta cell apoptosis and necrosis after 12 hours exposure to hypoxia. ARIP cells also displayed hypoxia-induced apoptosis and altered surface morphology after 24 hours, but no significant growth difference (p>0.05) was observed between hypoxic and normoxic conditions. Significantly higher expression of PDCD4 was observed in both beta cells (P<0.001) and ductal (P<0.01) cells under hypoxic conditions compared to controls. PDCD4 expression was localised to the cytoplasm of both beta cells and ductal cells, with no observed effects of hypoxia, normoxia or serum free conditions on intracellular shuttling of PDCD4.

Conclusion: These findings indicate that hypoxia-induced expression of PDCD4 is associated with increased beta cell death and suggests that PDCD4 may be an important factor in regulating beta cell survival during hypoxic stress.

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / metabolism*
  • Cell Death
  • Cell Hypoxia
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival
  • Insulin-Secreting Cells / metabolism*
  • Insulin-Secreting Cells / pathology*
  • Mice
  • RNA-Binding Proteins / metabolism*
  • Rats
  • Subcellular Fractions / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • Pdcd4 protein, mouse
  • Pdcd4 protein, rat
  • RNA-Binding Proteins

Grants and funding

SK was funded by the Diabetes Research Group, University of Brighton. NFA was funded by the Kuwaiti Cultural Office. The Kuwaiti Cultural Office had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.