title: A novel specific application of pyruvate protects the mouse retina against white light damage: differential stabilization of HIF-1α and HIF-2α.
abstract: OBJECTIVE
  To mimic hypoxia preconditioning by a novel specific pyruvate treatment and to study its retinal protection against white light damage.
  
  
  METHODS
  Six-to-eight-week-old BALB/c mice were exposed to strong white light calculated to produce photoreceptor degeneration. Some were given injections of pyruvate in a preordained protocol because evidence exists that proves pyruvate can affect the concentration of hypoxia inducible factor (HIF). Western blotting and real-time PCR were used to determine the concentration of proteins and mRNAs in retinas. Morphology was analyzed with toluidine blue staining and was plotted using a spidergraph. A free nucleosome cell death assay was used to examine apoptosis. Retina explant cultures were used to investigate the background mechanism.
  
  
  RESULTS
  Pyruvate administration stabilized hypoxia inducible factor (HIF)-1α but not HIF-2α. Expression of the downstream genes hemoxygenase-1 and erythropoietin mirrored the changes of the two HIFs, respectively. Importantly, pyruvate given not only before but also after exposure to light protected photoreceptors against apoptosis. In the retinal explant system, addition or depletion of pyruvate caused only changes of HIF-1α and prolyl hydroxylase (PHD)-2, while HIF-2α and PHD1 were not affected. However, under hypoxic conditions, HIF-2α was stabilized by pyruvate but not HIF-1α.
  
  
  CONCLUSIONS
  Pyruvate evoked a hypoxia-like response under normoxic conditions and was retina-protective against strong white light. This response included stabilization of HIF-1α but not HIF-2α. This differential stabilization might be related to the distinct preference of their degrading enzyme of PHD2 and PHD1 in response to pyruvate treatment.
authors.affiliation: Department of Histology and Embryology, China Medical University, Shenyang, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ren
authors.forename: Ning-Yu
authors.initials: NY
authors.lastname: Liu
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Song
authors.forename: Yun-Sheng
authors.initials: YS
authors.lastname: Ma
authors.forename: Xiao-Yue
authors.initials: XY
authors.lastname: Zhai
mesh_terms: D000818:Animals; D017209:Apoptosis; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D004921:Erythropoietin / Q000235:genetics; D051547:Heme Oxygenase-1 / Q000235:genetics; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D008027:Light / Q000009:adverse effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D020419:Photoreceptor Cells, Vertebrate / Q000528:radiation effects*; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism; D019289:Pyruvic Acid / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D012162:Retinal Degeneration / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004921:Erythropoietin; D051547:Heme Oxygenase-1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D011393:Procollagen-Proline Dioxygenase; D019289:Pyruvic Acid; D012333:RNA, Messenger; D000099162:Endothelial PAS Domain-Containing Protein 1; C497443:Hif1a protein, mouse; C522721:PHD1 protein, mouse; C490189:Egln1 protein, mouse