title: Erythropoietin Protects Retinal Cells in Diabetic Rats Through Upregulating ZnT8 via Activating ERK Pathway and Inhibiting HIF-1α Expression.
abstract: OBJECTIVE
  Zinc transporter 8 (ZnT8) was downregulated in hypoxic retina, which could be rescued by hypoxia-inducible factor-1α (HIF-1α) inhibition. Erythropoietin (EPO) protects retinal cells in diabetic rats through inhibiting HIF-1α as one of its mechanisms. We hence tried to explore the effect of EPO in regulating ZnT8 and protecting retinal cells in diabetic rats and possible mechanisms.
  
  
  METHODS
  Diabetes was induced in Sprague-Dawley rats. Intravitreal injection of EPO was performed 1 month after diabetes onset. The CoCl2-treated rat Müller cell line (rMC-1) was cotreated with EPO, soluble EPO receptor (sEPOR), digoxin, or U0126. Cell viability, cell death, and intracellular zinc level were examined. The expression of ZnT8, HIF-1α, AKT, and ERK was studied.
  
  
  RESULTS
  In diabetic rat retinas, EPO significantly decreased HIF-1α expression and increased ZnT8 expression. In CoCl2-treated rMC-1 cells, EPO increased cell viability and decreased intracellular zinc. Erythropoietin or digoxin could activate ERK pathway, downregulate HIF-1α, and upregulate ZnT8. The effect of EPO was abolished by sEPOR and U0126. Transient knockdown of ZnT8 increased intracellular zinc level, but not to a degree that would decrease cell viability or cause cell death.
  
  
  CONCLUSIONS
  In diabetic retinas, EPO maintains zinc homeostasis through activating the ERK pathway and downregulating HIF-1α, and thus upregulating ZnT8 expression. This work proposed a possible new protective mechanism for EPO in, and indicated a potential target for, the treatment of diabetic retinopathy.
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 2Department of Ophthalmology, Second Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Guoxu
authors.initials: G
authors.lastname: Xu
authors.affiliation: Department of Ophthalmology, Second Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Daohuan
authors.initials: D
authors.lastname: Kang
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Ophthalmology, Second Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Lou
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Sun
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Lixia
authors.initials: L
authors.lastname: Lu
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Guo-Tong
authors.initials: GT
authors.lastname: Xu
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China 3Department of Regenerative Medicine and Stem Cell Research Center, TUSM, Shanghai, China.
authors.forename: Jingfa
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Ophthalmology of Shanghai Tenth People's Hospital Tongji Eye Institute, Tongji University School of Medicine (TUSM), Shanghai, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental; D003930:Diabetic Retinopathy / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D015536:Down-Regulation; D004921:Erythropoietin / Q000008:administration & dosage*; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D058449:Intravitreal Injections; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D012313:RNA / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D015533:Transcriptional Activation; D015854:Up-Regulation; D000075703:Zinc Transporter 8
chemical_list: D027682:Cation Transport Proteins; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C542071:Slc30a8 protein, rat; D000075703:Zinc Transporter 8; D004921:Erythropoietin; D012313:RNA