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

Delphine Balmer1, Martine Emery, Pénélope Andreux

  • 1IRO-Institute for Research in Ophthalmology, Sion, Switzerland.

Plos One
|September 26, 2013
PubMed

Insights

Hypoglycemia induces retinal cell death by disrupting the balance between apoptosis and autophagy. Inhibiting autophagy exacerbates cell death, suggesting it plays a protective role against low glucose conditions in diabetic retinopathy.

Area of Science:

  • Ophthalmology
  • Cell Biology
  • Metabolic Disorders

Background:

  • Diabetic patients require strict blood glucose control to prevent complications like retinopathy.
  • Hypoglycemia, or low blood glucose, has been implicated as a potential factor in diabetic retinopathy development.
  • Previous studies demonstrated that acute hypoglycemia can cause retinal cell death in vivo and in vitro.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying low glucose-induced retinal cell death.
  • To explore the interplay between apoptosis and autophagy in retinal cells under hypoglycemic conditions.
  • To determine the role of autophagy defects in the pathogenesis of diabetic retinopathy.

Main Methods:

  • Utilized 661W photoreceptor cells cultured in low glucose conditions.
  • Assessed the expression levels of key apoptosis-related proteins (BCL2, BCL-XL, BAX).
  • Investigated the involvement of the AMPK/RAPTOR/mTOR pathway in autophagy.
  • Examined the autophagosome-lysosome fusion process by analyzing LAMP2a expression.
  • Inhibited autophagy using 3-methyladenine and by down-regulating ATG5/ATG7 expression.
  • Measured caspase 3 activation and cell viability.

Main Results:

  • Low glucose decreased anti-apoptotic proteins (BCL2, BCL-XL) and increased pro-apoptotic BAX.
  • Low glucose induced apoptosis and initiated autophagosome formation via the AMPK/RAPTOR/mTOR pathway.
  • Reduced LAMP2a expression resulted in impaired autophagosome-lysosome fusion.
  • Autophagy inhibition (3-MA, ATG5/ATG7 knockdown) significantly increased caspase 3 activation and cell death.
  • Low glucose disrupts the balance between apoptosis and autophagy, with autophagy initially acting as a protective mechanism.

Conclusions:

  • Autophagy defects are linked to low glucose-induced retinal cell death (661W cells).
  • This cell death mechanism may contribute to the development of diabetic retinopathy.
  • Targeting autophagy could offer a novel therapeutic strategy to mitigate hypoglycemia's adverse effects in diabetic patients.
  • Modulating autophagy may help prevent secondary complications of diabetes.

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