Diabetes regulates small molecular weight G-protein, H-Ras, in the microvasculature of the retina: implication in the development of retinopathy

Microvasc Res. 2008 Nov;76(3):189-93. doi: 10.1016/j.mvr.2008.04.002. Epub 2008 Apr 25.

Abstract

Retinopathy, a largely microvascular complication, affects over 80% of patients with diabetes for 20 years. The purpose of this study is to investigate the effect of diabetes on the activation of H-Ras, a small molecular weight G-protein that regulates cell fate, in the retinal microvessels. Microvessels were prepared from freshly isolated retina from streptozotocin diabetic rats or 30% galactose-fed rats by hypotonic lysis method. Ras activation was quantified by Raf-1 binding assay, and the activation of the signaling proteins, Raf-1 and mitogen activated protein (MAP) kinase, by quantifying their gene transcripts (RTPCR) and/or by protein expression (western blot). Two months of diabetes or experimental galactosemia activated H-Ras (Raf-binding assay) in the retinal microvessels by over 40% and 70% respectively compared to the values obtained from normal rat retinal microvessels. In the same diabetic rats the gene transcripts of H-Ras and its effector protein Raf-1 were elevated by 30% and 135% respectively with their protein expressions elevated by about 25% each, and this was paralleled by similar increases in the protein expressions of H-Ras and Raf-1 in experimentally galactosemic rats. Diabetes increased the gene expression of Ras-Raf-1 downstream signaling protein MAP kinase by over 50%, and that of nuclear transcriptional factor by 25-30%. This activation of H-Ras in retinal microvessels implies that its signaling pathway, in part, could be contributing to the microvascular pathology characteristic of diabetic retinopathy. Comparable activation of H-Ras and its signaling cascade in the retinal microvessels from experimentally galactosemic rats suggests that H-Ras activation is not due to insulin deficiency. Regulation of Ras function could provide important target in the complex approach to inhibit the pathogenesis of diabetic retinopathy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Diabetes Mellitus, Experimental / genetics
  • Diabetes Mellitus, Experimental / metabolism*
  • Diabetic Retinopathy / etiology*
  • Diabetic Retinopathy / genetics
  • Diabetic Retinopathy / metabolism*
  • Genes, ras
  • MAP Kinase Signaling System
  • Male
  • Microvessels / metabolism
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / metabolism
  • Proto-Oncogene Proteins c-raf / genetics
  • Proto-Oncogene Proteins c-raf / metabolism
  • Rats
  • Rats, Wistar
  • Retinal Vessels / metabolism*
  • ras Proteins / metabolism*

Substances

  • NF-kappa B
  • Nitric Oxide Synthase Type II
  • Nos2 protein, rat
  • Proto-Oncogene Proteins c-raf
  • ras Proteins