Cardioprotective effects of Zileuton 5-Lo inhibitor, is mediated by COX-2 via PKC delta activation.
곽현정, 박경미, 이형희, 정경숙, 이세형, 박현영
국립보건원 생명의과학센터 심혈관질환팀
Abstract
Zileuton, a well known 5-Lo inhibitor, has been demonstrated to exert anti-inflammatory effect through inhibition of 5-lipoxygenase metabolism. However, the role of 5-lipoxygenase and its inhibitor in the cardiac ischemia-reperfusion injury has not been completely elucidated. Here, we investigated the effects of zileuton on cardiac ischemia-reperfusion injury, and further examined possible involvement of protein kinase c (PKC) delta-mediated COX-2 induction. According to our data, pretreatment with zileuton (1-100 M) in H9c2 cells exerted profound dose-dependent protective effect against H2O2-induced oxidative stress, mimic to reperfusion damage in vitro. Zileuton acted as a PKC deltaactivator making PKC delta to translocate from cytosol to nucleus in as early as 5 minutes as demonstrated by digital imaging fluorescent microscopy. Inhibition of PKC delta activation with rotterlin (PKC delta specific inhibitor) abolished zileuton-induced protection against H2O2-induced cell death. Surprisingly, zileuton induced COX-2 expression and PGE2 production via PKC delta dependent pathway and inhibition of its activation with rofecoxib (selective COX-2 inhibitor) also abrogated protective effects. Activation of PKC delta by zileuton resulted in the activation of ERK1/2. Additionally, inhibition of either PKC delta or ERK1/2 activation abolished COX-2 and PGE2 production, implicating that COX-2 pathway is down-regulated by PKC delta and ERK1/2 pathways. Administration with zileuton (50 mg/kg, i.p.), followed by 60 min coronary occlusion/60 min reperfusion, increased in PKC delta phosphorylation in necrotic area and significantly reduced in infarct size. In conclusion, zileuton protects ischemic damage by activating PKC delta and subsequent activation of its downstream molecules ERK1/2 and COX-2. Based on these findings, we propose that zileuton may be useful in protecting I/R injury of the heart
Key word; 5-Lo inhibitor, cyclooxygenase-2, Protein kinase C
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