title: Role of oxidative stress in epigenetic modification of MMP-9 promoter in the development of diabetic retinopathy.
abstract: BACKGROUND
  In the pathogenesis of diabetic retinopathy, damaged retinal mitochondria accelerate apoptosis of retinal capillary cells, and regulation of oxidative stress by manipulating mitochondrial superoxide dismutase (SOD2) protects mitochondrial homeostasis and prevents the development of diabetic retinopathy. Diabetes also activates matrix metalloproteinase-9 (MMP-9), and activated MMP-9 damages retinal mitochondria. Recent studies have shown a dynamic DNA methylation process playing an important role in regulation of retinal MMP-9 transcription in diabetes; the aim of this study is to investigate the role of oxidative stress in MMP-9 transcription.
  
  
  METHODS
  The effect of regulation of mitochondrial superoxide on DNA methylation of MMP-9 promoter region was investigated in retinal endothelial cells incubated in the presence or absence of a MnSOD mimetic MnTBAP, by quantifying the levels of 5 methyl cytosine (5mC) and hydroxyl-methyl cytosine (5hmC). The binding of DNA methylating, and of hydroxymenthylating enzymes (Dnmts and Tets, respectively), at MMP-9 promoter (by chromatin immunoprecipitation) was also evaluated. The in vitro results were confirmed in the retina of diabetic mice overexpressing SOD2.
  
  
  RESULTS
  MnTBAP attenuated glucose-induced decrease in 5mC levels and increase on Dnmt1 binding at the MMP-9 promoter region. MnTBAP also ameliorated alterations in 5hmC levels and Tet binding, regulated MMP-9 transcription, and prevented mitochondrial damage. Similarly, mice overexpressing SOD2 were protected from diabetes-induced alteration in MMP-9 promoter methylation, and its transcription.
  
  
  CONCLUSIONS
  Thus, regulation of oxidative stress by pharmacologic/genetic approaches maintains retinal mitochondrial homeostasis by ameliorating epigenetic modifications in the MMP-9 promoter region.
authors.affiliation: Kresge Eye Institute, Wayne State University, Detroit, MI, 48201, USA. rkowluru@med.wayne.edu.
authors.forename: Renu A
authors.initials: RA
authors.lastname: Kowluru
authors.affiliation: Kresge Eye Institute, Wayne State University, Detroit, MI, 48201, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Shan
mesh_terms: D000818:Animals; D017209:Apoptosis; D002417:Cattle; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics*; D019175:DNA Methylation; D003921:Diabetes Mellitus, Experimental; D003930:Diabetic Retinopathy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D057890:Epigenomics / Q000379:methods; D020780:Matrix Metalloproteinase 9 / Q000235:genetics* / Q000378:metabolism; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004247:DNA; D013482:Superoxide Dismutase; D020780:Matrix Metalloproteinase 9
keywords: DNA methylation; Diabetic retinopathy; Epigenetics; Oxidative stress