title: Neuroprotective effects of valproic acid against hemin toxicity: possible involvement of the down-regulation of heme oxygenase-1 by regulating ubiquitin-proteasomal pathway.
abstract: During hemorrhagic stroke induced by intracerebral hemorrhage (ICH), brain injury occurs from the deleterious actions of hemoglobin byproducts; induction of heme oxygenase-1 (HO-1) also plays a critical role in the neurotoxicity in ICH. Valproic acid (VPA), which is a commonly used drug in the treatment of epilepsy, has been reported to have neuroprotective effects against various neuronal insults including ischemic stroke. We investigated the effect of VPA on HO-1-mediated neurotoxicity in an experimental model of ICH. We investigated the effects of VPA on HO-1 protein in primary cortical neurons: (1) the expression levels of HO-1 mRNA and protein measured by RT-PCR and Western blotting; (2) the cell viability and ROS generation by MTT reduction assay and ROS measurement; (3) the signal pathway regulated by VPA using IP-Western blotting; (4) the effects of VPA on hemin-induced cell death by hemin microinjection and immunohistochemistry in vivo. VPA treatment partially blocked cell death induced by hemin, which is released from hemoglobin during ICH, both in rat primary cortical neurons and rat brain. Treatment of VPA significantly decreased the expression of HO-1 protein both in vitro and in vivo. Hemin treatment induced HO-1 protein expression and this was partially blocked by pretreatment with VPA, which might be mediated by increased ubiquitination and degradation of HO-1 via ERK1/2 and JNK activation in primary cortical neurons. Our results indicate that VPA inhibits hemin toxicity by downregulating HO-1 protein expression, and provide a therapeutic strategy to attenuate intracerebral hemorrhagic injury.
authors.affiliation: Department of Neurology, Center for Neuroscience Research, SMART Institute of Advanced Biomedical Science, School of Medicine, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
authors.forename: Kyoung Ja
authors.initials: KJ
authors.lastname: Kwon
authors.forename: Jung Nam
authors.initials: JN
authors.lastname: Kim
authors.forename: Min Kyeong
authors.initials: MK
authors.lastname: Kim
authors.forename: Su Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Kyu Suk
authors.initials: KS
authors.lastname: Cho
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Jeon
authors.forename: Hahn Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Ryu
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Han
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Cheong
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Ignarro
authors.forename: Seol-Heui
authors.initials: SH
authors.lastname: Han
authors.forename: Chan Young
authors.initials: CY
authors.lastname: Shin
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D015536:Down-Regulation; D005260:Female; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006427:Hemin / Q000633:toxicity*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D020935:MAP Kinase Signaling System; D008297:Male; D018696:Neuroprotective Agents / Q000494:pharmacology*; D011247:Pregnancy; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D018894:Reverse Transcriptase Inhibitors; D025801:Ubiquitin / Q000378:metabolism*; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D017931:DNA Primers; D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; D018894:Reverse Transcriptase Inhibitors; D025801:Ubiquitin; D014635:Valproic Acid; D006427:Hemin; D051547:Heme Oxygenase-1; D046988:Proteasome Endopeptidase Complex