Role of matrix metalloproteinase-9 in the development of diabetic retinopathy and its regulation by H-Ras.
OBJECTIVE
Diabetes activates a small molecular weight G-protein, H-Ras, in the retina and its capillary cells, and H-Ras activation is implicated in the apoptosis of retinal capillary cells. Matrix metalloproteinase (MMP)-9 is regulated by H-Ras, and in diabetes its activation is associated with increased vascular permeability. The goal of this study was to investigate the role of sustained activation of MMP-9 in the pathogenesis of diabetic retinopathy and to illustrate the mechanism through which it is upregulated in diabetes.


METHODS
Retinal MMP-9 activation and its tissue inhibitor, TIMP-1, were quantified in streptozotocin-induced diabetic rats. Inhibition of H-Ras by simvastatin on diabetes-induced activation of H-Ras was evaluated. The mechanism by which diabetes regulates retinal MMP-9 was confirmed by determining the effect of genetic or pharmacologic regulation of H-Ras on its activation in retinal endothelial cells.


RESULTS
In rats, MMP-9 was activated and expression of TIMP-1 was decreased in the retina and its microvasculature at both 2 months and 12 months of diabetes. In retinal endothelial cells, high glucose activated MMP-9, and inhibition of its activation (by pharmacologic inhibitor or siRNA) ameliorated accelerated apoptosis. Inhibition of H-Ras, both in diabetic rats (simvastatin) and in isolated endothelial cells (H-Ras siRNA), abrogated the activation of MMP-9 and prevented the reduction of TIMP-1.


CONCLUSIONS
Hyperglycemia-induced activation of MMP-9 accelerates apoptosis of retinal capillary cells, a phenomenon that predicts the development of diabetic retinopathy, and the activation of MMP-9 is downstream of H-Ras. Characterizing the role of MMP-9 in the development of diabetic retinopathy will help explore novel molecular targets for future pharmacological interventions.
Kowluru
Renu A
RA
Department of Ophthalmology, Kresge Eye Institute, Detroit, Michigan 48201, USA. rkowluru@med.wayne.edu
D000818:Animals; D017209:Apoptosis; D002417:Cattle; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D003930:Diabetic Retinopathy / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000473:pathology; D004789:Enzyme Activation; D011905:Genes, ras / Q000187:drug effects / Q000502:physiology*; D020780:Matrix Metalloproteinase 9 / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000201:enzymology*; D012171:Retinal Vessels / Q000201:enzymology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019821:Simvastatin / Q000494:pharmacology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D014162:Transfection
D034741:RNA, Small Interfering; D019715:Tissue Inhibitor of Metalloproteinase-1; D019821:Simvastatin; D020780:Matrix Metalloproteinase 9