title: Regulation of retinal inflammation by rhythmic expression of MiR-146a in diabetic retina.
abstract: OBJECTIVE
  Chronic inflammation and dysregulation of circadian rhythmicity are involved in the pathogenesis of diabetic retinopathy. MicroRNAs (miRNAs) can regulate inflammation and circadian clock machinery. We tested the hypothesis that altered daily rhythm of miR-146a expression in diabetes contributes to retinal inflammation.
  
  
  METHODS
  Nondiabetic and STZ-induced diabetic rats kept in 12/12 light/dark cycle were killed every 2 hours over a 72-hour period. Human retinal endothelial cells (HRECs) were synchronized with dexamethasone. Expression of miR-146a, IL-1 receptor-associated kinase 1 (IRAK1), IL-1β, VEGF and ICAM-1, as well as clock genes was examined by real-time PCR and Western blot. To modulate expression levels of miR-146a, mimics and inhibitors were used.
  
  
  RESULTS
  Diabetes inhibited amplitude of negative arm (per1) and enhanced amplitude of the positive arm (bmal1) of clock machinery in retina. In addition to clock genes, miR-146a and its target gene IRAK1 also exhibited daily oscillations in antiphase; however, these patterns were lost in diabetic retina. This loss of rhythmic pattern was associated with an increase in ICAM-1, IL-β, and VEGF expression. Human retinal endothelial cells had robust miR-146a expression that followed circadian oscillation pattern; however, HRECs isolated from diabetic donors had reduced miR-146a amplitude but increased amplitude of IRAK1 and ICAM-1. In HRECs, miR-146a mimic or inhibitor caused 1.6- and 1.7-fold decrease or 1.5- and 1.6-fold increase, respectively, in mRNA and protein expression levels of ICAM-1 after 48 hours.
  
  
  CONCLUSIONS
  Diabetes-induced dysregulation of daily rhythms of miR-146a and inflammatory pathways under miR-146a control have potential implications for the development of diabetic retinopathy.
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Svetlana N
authors.initials: SN
authors.lastname: Bozack
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Boulton
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Maria B
authors.initials: MB
authors.lastname: Grant
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Julia V
authors.initials: JV
authors.lastname: Busik
mesh_terms: D000818:Animals; D015153:Blotting, Western; D056926:CLOCK Proteins / Q000235:genetics; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000235:genetics; D003930:Diabetic Retinopathy / Q000235:genetics*; D042783:Endothelial Cells; D005786:Gene Expression Regulation / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics; D053583:Interleukin-1beta / Q000235:genetics; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020318:Rats, Long-Evans; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium; D012171:Retinal Vessels; D012173:Retinitis / Q000235:genetics*; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
chemical_list: D005938:Glucocorticoids; D053583:Interleukin-1beta; C554180:MIRN146 microRNA, rat; D035683:MicroRNAs; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D018799:Intercellular Adhesion Molecule-1; D003907:Dexamethasone; D056926:CLOCK Proteins; C538945:Clock protein, rat; C547807:IRAK1 protein, rat; D053592:Interleukin-1 Receptor-Associated Kinases
keywords: circadian rhythm; diabetic retinopathy; endothelial cells; inflammatory response; intercellular adhesion molecule 1; miRNA