FOXO1 Plays an Important Role in Enhanced Microvascular Cell Apoptosis and Microvascular Cell Loss in Type 1 and Type 2 Diabetic Rats

  1. Yugal Behl1,
  2. Padmaja Krothapalli1,
  3. Tesfahun Desta1,
  4. Sayon Roy2 and
  5. Dana T Graves (gravesdt{at}
  1. 1Department of Periodontology and Oral Biology, Boston University School of Dental Medicine,
  2. 2Departments of Medicine and Ophthalmology, Boston University School of Medicine
  3. 3Department of Periodontics, University of Medicine and Dentistry of New Jersey, Newark, NJ


    Objective: To investigate early events leading to microvascular cell loss in diabetic retinopathy.

    Research Design and Methods: FOXO1 was tested in vivo by DNA binding activity and by nuclear translocation in microvascular cells in retinal trypsin digests. In vivo studies were undertaken in STZ rats and ZDF rats using the TNF specific blocker, pegsunercept or by inhibiting FOXO1 with RNAi. Microvascular cell apoptosis, formation of pericyte ghosts and acellular capillaries were measured. Upstream and downstream effects of high glucose induced FOXO1 were tested on rat microvascular endothelial cells (RMEC) by siRNA in vitro.

    Results: DNA binding or nuclear translocation of FOXO1 was elevated in type 1 and type 2 diabetic retinas, which was reduced by TNF inhibition. Diabetes stimulated microvascular cell apoptosis and pericyte ghost and acellular capillary development was inhibited by FOXO1 siRNA. High glucose in vitro decreased FOXO1 phosphorylation and DNA binding activity and decreased Akt phosphorylation in RMEC. High glucose stimulated FOXO1 DNA binding activity was mediated through TNF-α and formation of reactive oxygen species (ROS), while inhibitors of TNF and ROS and FOXO1 siRNA reduced high glucose enhanced RMEC apoptosis. The caspase-3/7 activity and capacity of high glucose to increase mRNA levels of several genes that regulate RMEC activation and apoptosis were knocked down by FOXO1 siRNA.

    Conclusion: FOXO1 plays an important role in rat retinal microvascular cell loss in type-1 and -2 diabetic rats and can be linked to the effect of high glucose on FOXO1 activation.


      • Received April 22, 2008.
      • Accepted December 16, 2008.