Baicalein protects against retinal ischemia by antioxidation, antiapoptosis, downregulation of HIF-1α, VEGF, and MMP-9 and upregulation of HO-1.

Abstract

PURPOSE:

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: Hsiao-Ming Chao, Min-Jay Chuang, Jorn-Hon Liu, Xiao-Qian Liu, Li-Kang Ho, Wynn H T Pan, Xiu-Mei Zhang, Chi-Ming Liu, Shen-Kou Tsai, Chi-Woon Kong, Shou-Dong Lee, Mi-Mi Chen, Fang-Ping Chao
• Journal: Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics (J Ocul Pharmacol Ther) 2013 Jul-Aug Vol. 29 Issue 6 Pg. 539-49 ISSN: 1557-7732 [Electronic] United States
• PMID: 23537149 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antioxidants
• Flavanones
• Hif1a protein, rat
• Hypoxia-Inducible Factor 1, alpha Subunit
• Vascular Endothelial Growth Factor A
• vascular endothelial growth factor A, rat
• baicalein
• Heme Oxygenase-1
• Matrix Metalloproteinase 9
• Mmp9 protein, rat

Topics

• Animals
• Antioxidants (administration & dosage, metabolism, pharmacology, therapeutic use)
• Apoptosis (drug effects)
• Cell Line
• Down-Regulation
• Flavanones (administration & dosage, pharmacology, therapeutic use)
• Heme Oxygenase-1 (biosynthesis)
• Hypoxia-Inducible Factor 1, alpha Subunit (biosynthesis)
• Intravitreal Injections
• Ischemia (metabolism, pathology, prevention & control)
• Matrix Metalloproteinase 9 (biosynthesis)
• Rats
• Rats, Wistar
• Retina (drug effects, metabolism, pathology)
• Retinal Diseases (metabolism, pathology, prevention & control)
• Retinal Vessels (drug effects)
• Up-Regulation
• Vascular Endothelial Growth Factor A (biosynthesis)