title: Epigenetic modifications of Keap1 regulate its interaction with the protective factor Nrf2 in the development of diabetic retinopathy.
abstract: OBJECTIVE
  Diabetes induces oxidative imbalance in the retina and impairs Nrf2-mediated antioxidant response, and elevates Keap1, the cytoplasmic repressor of Nrf2. The goal of this study was to understand the role of epigenetic modifications at Keap1 promoter in regulation of Nrf2 function.
  
  
  METHODS
  The effect of high glucose on the binding of transcriptional factor Sp1 at Keap1 promoter and histone methylation status of the promoter was investigated in retinal endothelial cells. Role of histone methylation was confirmed in cells transfected with siRNA of methyltransferase enzyme Set7/9 (SetD7). In vitro results were confirmed in the retina from streptozotocin-induced diabetic rats. The role of epigenetic modifications of Keap1 promoter in the metabolic memory was examined in rats maintained in poor control for 3 months followed by good control for 3 months.
  
  
  RESULTS
  Hyperglycemia increased the binding of Sp1 at Keap1 promoter, and enriched H3K4me1 and activated SetD7. SetD7-siRNA prevented increase in Sp1 binding at Keap1 promoter and Keap1 expression, and ameliorated decrease in Nrf2-regulated antioxidant genes. Cessation of hyperglycemia failed to attenuate increased binding of Sp1 at Keap1, and the promoter continued to be methylated with increased expression of Keap1 and decreased expression of Nrf2-regulated genes.
  
  
  CONCLUSIONS
  Epigenetic modifications at Keap1 promoter by SetD7 facilitate its binding with Sp1, increasing its expression. Keap1 restrains Nrf2 in the cytosol, impairing its transcriptional activity. Reversal of hyperglycemia fails to provide any benefit to epigenetic modifications of Keap1 promoter, suggesting their role in both the development of diabetic retinopathy and the metabolic memory phenomenon.
authors.affiliation: Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States.
authors.forename: Manish
authors.initials: M
authors.lastname: Mishra
authors.affiliation: Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhong
authors.affiliation: Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States.
authors.forename: Renu A
authors.initials: RA
authors.lastname: Kowluru
mesh_terms: D000818:Animals; D019175:DNA Methylation; D003921:Diabetes Mellitus, Experimental; D003930:Diabetic Retinopathy / Q000235:genetics* / Q000378:metabolism / Q000517:prevention & control; D005500:Follow-Up Studies; D005786:Gene Expression Regulation; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D000072019:Kelch-Like ECH-Associated Protein 1; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000096:biosynthesis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C486610:KEAP1 protein, rat; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D012313:RNA
keywords: Keap1; Nrf2; diabetic retinopathy; epigenetic modifications; metabolic memory