Diabetes-induced activation of caspase-3 in retina: effect of antioxidant therapy

Free Radic Res. 2002 Sep;36(9):993-9. doi: 10.1080/1071576021000006572.


Apoptosis of retinal endothelial cells and pericytes is postulated to contribute to the development of retinopathy in diabetes. The goal of this study is to investigate diabetes-induced activation of retinal caspase-3, an apoptosis executer enzyme, in retina, and examine the effects of antioxidants on the activation. Caspase-3 activation was determined in the retina of alloxan diabetic rats (2-14 months duration) and in the isolated retinal capillary cells (endothelial cells and pericytes) by measuring cleavage of caspase-3 specific fluorescent substrate, and cleavage of caspase-3 holoenzyme and poly (ADP ribosyl) polymerase. Effect of antioxidants on the activation of caspase-3 was determined by feeding a group of diabetic rats diet supplemented with a comprehensive mixture of antioxidants, including Trolox, alpha-tocopherol, N-acetyl cysteine, ascorbic acid, beta-carotene and selenium for 2-14 months, and also under in vitro conditions by incubating isolated retinal capillary cells with antioxidants with wide range of actions. Caspase-3 was activated in the rat retina at 14 months of diabetes (P < 0.05 vs. normal), but not at 2 months of diabetes, and administration of antioxidants for the entire duration inhibited this activation. In the isolated retinal capillary cells incubated in 25 mM glucose medium, caspase-3 activity was increased by 50% compared to the cells incubated in 5 mM glucose (P < 0.02), and antioxidants or caspase-3 inhibitor inhibited this increase. Our results suggest that increased oxidative stress in diabetes is involved in the activation of retinal caspase-3 and apoptosis of endothelial cells and pericytes. Antioxidants might be inhibiting the development of diabetic retinopathy by inhibiting microvascular apoptosis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / administration & dosage
  • Animals
  • Antioxidants / therapeutic use*
  • Apoptosis
  • Ascorbic Acid / administration & dosage
  • Caspase 3
  • Caspases / metabolism*
  • Diabetes Mellitus, Experimental / enzymology*
  • Diabetic Retinopathy / enzymology
  • Diabetic Retinopathy / pathology
  • Diabetic Retinopathy / prevention & control*
  • Endothelium, Vascular / enzymology
  • Endothelium, Vascular / pathology
  • Enzyme Activation
  • Glucose / metabolism
  • In Vitro Techniques
  • Male
  • Oxidative Stress
  • Pericytes / enzymology
  • Pericytes / pathology
  • Poly(ADP-ribose) Polymerases / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Retina / enzymology*
  • Selenium / administration & dosage
  • Thiobarbituric Acid Reactive Substances / metabolism
  • alpha-Tocopherol / administration & dosage
  • beta Carotene / administration & dosage


  • Antioxidants
  • Thiobarbituric Acid Reactive Substances
  • beta Carotene
  • Poly(ADP-ribose) Polymerases
  • Casp3 protein, rat
  • Caspase 3
  • Caspases
  • alpha-Tocopherol
  • Selenium
  • Glucose
  • Ascorbic Acid
  • Acetylcysteine