title: Erythropoietin protects adult retinal ganglion cells against NMDA-, trophic factor withdrawal-, and TNF-α-induced damage.
abstract: OBJECTIVE
  This study aimed to evaluate the neuroprotective effect of EPO in the presence of N-methyl-d-aspartate (NMDA)-, trophic factor withdrawal (TFW)-, and tumor necrosis factor-alpha (TNF-α)-induced toxicity on total, small, and large retinal ganglion cells (RGCs).
  
  
  METHODS
  Retinal cells from adult rats were cultured in a medium containing brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), basic fibroblast growth factor (bFGF), and forskolin. Expression of RGC markers and EPOR was examined using immunocytochemistry. RGCs were classified according to their morphological properties. Cytotoxicity was induced by NMDA, TFW, or TNF-α. RGC survival was assessed by counting thy-1 and neurofilament-l double-positive cells.
  
  
  RESULTS
  EPO offered dose-dependent (EC₅₀ = 5.7 ng/mL) protection against NMDA toxicity for small RGCs; protection was not significant for large RGCs. Time-course analysis showed that the presence of EPO either before or after NMDA exposure gave effective protection. For both small and large RGCs undergoing trophic factor withdrawal, EPO at concentrations of 1, 10, or 100 ng/mL improved survival. However, EPO had to be administered soon after the onset of injury to provide effective protection. For TNF-α-induced toxicity, survival of small RGCs was seen only for the highest examined concentration (100 ng/mL) of EPO, whereas large RGCs were protected at concentrations of 1, 10, or 100 ng/mL of EPO. Time-course analysis showed that pretreatment with EPO provided protection only for large RGCs; early post-treatment with EPO protected both small and large RGCs. Inhibitors of signal transduction and activators of transcription such as (STAT)-5, mitogen-activated protein kinases (MAPK)/extracellular-regulated kinase (ERK), and phosphatidyl inositol-3 kinase (PI3K)/Akt impaired the protective effect of EPO on RGCs exposed to different insults.
  
  
  CONCLUSIONS
  EPO provided neuroprotection to cultured adult rat RGCs; however, the degree of protection varied with the type of toxic insult, RGC subtype, and timing of EPO treatment.
authors: Graduate Institute of Life Sciences, National Defense Medical Center, Neihu, Taipei, Taiwan.
authors: Zhi-Yang
authors: ZY
authors: Chang
authors: Ming-Kung
authors: MK
authors: Yeh
authors: Chiao-Hsi
authors: CH
authors: Chiang
authors: Yi-Hao
authors: YH
authors: Chen
authors: Da-Wen
authors: DW
authors: Lu
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor; D002452:Cell Count; D018929:Cell Culture Techniques; D020934:Ciliary Neurotrophic Factor; D005576:Colforsin; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000494:pharmacology*; D016222:Fibroblast Growth Factor 2; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D016202:N-Methylaspartate / Q000633:toxicity*; D051381:Rats; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000187:drug effects*; D018675:Toxicity Tests; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D020934:Ciliary Neurotrophic Factor; D003470:Culture Media; D014409:Tumor Necrosis Factor-alpha; D016222:Fibroblast Growth Factor 2; D004921:Erythropoietin; D005576:Colforsin; D016202:N-Methylaspartate
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