Autophagy defect is associated with low glucose-induced apoptosis in 661W photoreceptor cells

PLoS One. 2013 Sep 16;8(9):e74162. doi: 10.1371/journal.pone.0074162. eCollection 2013.

Abstract

Glucose is an important metabolic substrate of the retina and diabetic patients have to maintain a strict normoglycemia to avoid diabetes secondary effects, including cardiovascular disease, nephropathy, neuropathy and retinopathy. Others and we recently demonstrated the potential role of hypoglycemia in diabetic retinopathy. We showed acute hypoglycemia to induce retinal cell death both in vivo during an hyperinsulinemic/hypoglycemic clamp and in vitro in 661W photoreceptor cells cultured at low glucose concentration. In the present study, we showed low glucose to induce a decrease of BCL2 and BCL-XL anti-apoptotic proteins expression, leading to an increase of free pro-apoptotic BAX. In parallel, we showed that, in retinal cells, low glucose-induced apoptosis is involved in the process of autophagosomes formation through the AMPK/RAPTOR/mTOR pathway. Moreover, the decrease of LAMP2a expression led to a defect in the autophagosome/lysosome fusion process. Specific inhibition of autophagy, either by 3-methyladenine or by down-regulation of ATG5 or ATG7 proteins expression, increased caspase 3 activation and 661W cell death. We show that low glucose modifies the delicate equilibrium between apoptosis and autophagy. Cells struggled against low nutrient condition-induced apoptosis by starting an autophagic process, which led to cell death when inhibited. We conclude that autophagy defect is associated with low glucose-induced 661W cells death that could play a role in diabetic retinopathy. These results could modify the way of addressing negative effects of hypoglycemia. Short-term modulation of autophagy could be envisioned to treat diabetic patients in order to avoid secondary complications of the disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Autophagy / drug effects*
  • Blotting, Western
  • Cells, Cultured
  • Glucose / pharmacology*
  • Immunohistochemistry
  • Immunoprecipitation
  • In Situ Nick-End Labeling
  • Mice
  • Photoreceptor Cells / cytology*
  • Photoreceptor Cells / drug effects*
  • Photoreceptor Cells / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Glucose

Grants and funding

RR was supported by “La Fondation Romande pour la Recherche sur le Diabète” (www.fondationromande-diabete.ch) “La Fondation Charles-Henri et Ruth ROUFFY” and “La Fondation Art & Vie”; JA and PA were supported by the Ecole Polytechnique Fédérale de Lausanne, the Swiss National Science Foundation (www.snf.ch), and the European Research Council (www.erc.europa.eu). JP was supported by grants from the Swiss National Science Foundation (www.snf.ch) (310030-130769) and from the Faculté de Biologie et Médecine (University of Lausanne). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.