title: Valproic acid-mediated neuroprotection in retinal ischemia injury via histone deacetylase inhibition and transcriptional activation.
abstract: Retinal ischemia plays a central role in several retinal diseases. The pathogenesis of retinal ischemia involves changes in gene expression. Valproic acid (VPA), a broad-spectrum histone deacetylase inhibitor, is an anticonvulsant and mood-stabilizing drug with neuroprotective effects. Here, we investigated whether VPA protects the retina and optic nerve axon from ischemic damage in a rat model and determined a possible protective mechanism. Adult male Wistar rats were randomized into sham, ischemia/reperfusion (I/R)-plus-vehicle, and I/R-plus-VPA groups. Rats received subcutaneous injections of 300 mg/kg VPA or phosphate-buffered saline twice a day after retinal ischemia induced by acute high intraocular pressure. Twenty-four hours after I/R, retinal neuron apoptosis was evaluated using the TUNEL assay. The expression of heat-shock protein 70 (Hsp70), activated-caspase-3, and apoptotic-protease-activating factor-1 (apaf-1), acetylation levels of histone H3, release of cytochrome c, and interaction between Hsp70 and apaf-1 were analyzed by immunoblotting analysis in all groups; the transcriptional activation of the Hsp70 gene and interaction between the Hsp70 promoter with p300 or HDAC1 were analyzed using chromatin immunoprecipitation assay. Seven days after I/R, the histological changes in the retina were evaluated using hematoxylin and eosin staining, and optic nerve axon damage was evaluated using toluidine blue staining and transmission electron microscopy. The density of retinal ganglion cells (RGCs) was analyzed using Fluoro-Gold retrograde labeling at 7, 14, 21 days after I/R. VPA markedly attenuated I/R-induced retinal neuron apoptosis, damage to RGCs, and morphological injury to the retina and optic nerve axons. VPA resulted in the upregulation of Hsp70 and hyperacetylation of histone H3, accompanied by Hsp70 promoter hyperacetylation, which may result from increased p300 recruitment to the Hsp70 promoter. Furthermore, VPA increased the binding between Hsp70 and apaf-1 to block apoptosome formation and reduced the release of cytochrome c and activation of caspase-3 in the retina after I/R. Therefore, VPA-mediated neuroprotection against I/R injury in the retina may involve cytoprotective Hsp70 induction via transcriptional activation and inhibition of the mitochondria-mediated apoptosis pathway.
authors.affiliation: Department of Ophthalmology, Shanghai Jiaotong University affiliated Shanghai First People's Hospital, Wujin Road 85, Shanghai 200080, China.
authors.forename: ZhenZhen
authors.initials: Z
authors.lastname: Zhang
authors.forename: XiuHong
authors.initials: X
authors.lastname: Qin
authors.forename: Nianting
authors.initials: N
authors.lastname: Tong
authors.forename: XinFeng
authors.initials: X
authors.lastname: Zhao
authors.forename: YuanYuan
authors.initials: Y
authors.lastname: Gong
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Shi
authors.forename: XingWei
authors.initials: X
authors.lastname: Wu
mesh_terms: D000107:Acetylation; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D007279:Injections, Subcutaneous; D008297:Male; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D012164:Retinal Diseases / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015533:Transcriptional Activation / Q000187:drug effects*; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: C506594:Apaf1 protein, rat; D053477:Apoptotic Protease-Activating Factor 1; D018840:HSP70 Heat-Shock Proteins; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D018696:Neuroprotective Agents; D014635:Valproic Acid; D045304:Cytochromes c; D053148:Caspase 3; D006655:Histone Deacetylases