title: Baicalein protects against retinal ischemia by antioxidation, antiapoptosis, downregulation of HIF-1α, VEGF, and MMP-9 and upregulation of HO-1.
abstract: OBJECTIVE
  Retinal ischemia-associated ocular disorders are vision threatening. This study examined whether the flavonoid baicalein is able to protect against retinal ischemia/reperfusion.
  
  
  METHODS
  Using rats, the intraocular pressure was raised to 120 mmHg for 60 min to induce retinal ischemia. In vitro, an ischemic-like insult, namely oxidative stress, was established by incubating dissociated retinal cells with 100 μM ascorbate and 5 μM FeSO4 (iron) for 1 h. The rats or the dissociated cells had been pretreated with baicalein (in vivo: 0.05 or 0.5 nmol; in vitro: 100 μM), vehicle (1% ethanol), or trolox (in vivo: 5 nmol; in vitro: 100 μM or 1 mM). The effects of these treatments on the retina or the retinal cells were evaluated by electrophysiology, immunohistochemistry, terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) staining, Western blotting, or in vitro dichlorofluorescein assay. In addition, real-time-polymerase chain reaction was used to assess the retinal expression of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase-9 (MMP-9), vascular endothelium growth factor (VEGF), and heme oxygenase-1 (HO-1).
  
  
  RESULTS
  The retinal changes after ischemia included a decrease in the electroretinogram b-wave amplitude, a loss of choline acetyltransferase immunolabeling amacrine cell bodies/neuronal processes, an increase in vimentin immunoreactivity, which is a marker for Müller cells, an increase in apoptotic cells in the retinal ganglion cell layer linked to a decrease in the Bcl-2 protein, and changes in the mRNA levels of HIF-1α, VEGF, MMP-9, and HO-1. Of clinical importance, the ischemic detrimental effects were concentration dependently and/or significantly (0.05 nmol and/or 0.5 nmol) altered when baicalein was applied 15 min before retinal ischemia. Most of all, 0.5 nmol baicalein significantly reduced the upregulation of MMP-9; in contrast, 5 nmol trolox only had a weak attenuating effect. In dissociated retinal cells subjected to ascorbate/iron, there was an increase in the levels of reactive oxygen species, which had been significantly attenuated by 100 μM baicalein and trolox (100 μM or 1 mM; a stronger antioxidative effect at 1 mM).
  
  
  CONCLUSIONS
  Baicalein would seem to protect against retinal ischemia via antioxidation, antiapoptosis, upregulation of HO-1, and downregulation of HIF-1α, VEGF, and MMP-9. The antioxidative effect of baicalein would appear to play a minor role in downregulation of MMP-9.
authors.affiliation: Department of Ophthalmology, Cheng Hsin General Hospital, Taipei, Taiwan, Republic of China. ox_drchao@yahoo.ca
authors.forename: Hsiao-Ming
authors.initials: HM
authors.lastname: Chao
authors.forename: Min-Jay
authors.initials: MJ
authors.lastname: Chuang
authors.forename: Jorn-Hon
authors.initials: JH
authors.lastname: Liu
authors.forename: Xiao-Qian
authors.initials: XQ
authors.lastname: Liu
authors.forename: Li-Kang
authors.initials: LK
authors.lastname: Ho
authors.forename: Wynn H T
authors.initials: WH
authors.lastname: Pan
authors.forename: Xiu-Mei
authors.initials: XM
authors.lastname: Zhang
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Liu
authors.forename: Shen-Kou
authors.initials: SK
authors.lastname: Tsai
authors.forename: Chi-Woon
authors.initials: CW
authors.lastname: Kong
authors.forename: Shou-Dong
authors.initials: SD
authors.lastname: Lee
authors.forename: Mi-Mi
authors.initials: MM
authors.lastname: Chen
authors.forename: Fang-Ping
authors.initials: FP
authors.lastname: Chao
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D015536:Down-Regulation; D044950:Flavanones / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D051547:Heme Oxygenase-1 / Q000096:biosynthesis*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis*; D058449:Intravitreal Injections; D007511:Ischemia / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D012164:Retinal Diseases / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D012171:Retinal Vessels / Q000187:drug effects; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
chemical_list: D000975:Antioxidants; D044950:Flavanones; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; C006680:baicalein; D051547:Heme Oxygenase-1; D020780:Matrix Metalloproteinase 9; C572337:Mmp9 protein, rat
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