The cardioprotective effects of zileuton, a 5-lipoxygenase inhibitor, are mediated by COX-2 via activation of PKC delta.
Zileuton has been demonstrated to act as an anti-inflammatory agent by virtue of its well-known ability to inhibit 5-lipoxygenase (5-LO). However, the effects of zileuton on cardiovascular disease and cardiomyocyte apoptosis are unclear. Here, we investigated the effects of zileuton on apoptosis of cardiac myogenic H9c2 cells and neonatal rat cardiomyocytes (NRCMs), and examined the possible role of PKC delta-mediated induction of COX-2 in these effects. Treatment of H9c2 cells with zileuton efficiently induced COX-2 expression and PGE(2) biosynthesis in a time- and dose-dependent manner. Zileuton also exerted a profound protective effect against H(2)O(2)-induced oxidative stress, a mimic of reperfusion damage in vitro, and this protective effect was abolished by COX-2-selective inhibitor. When we investigated the signalling pathways involved in zileuton-induced COX-2 expression, we found that zileuton acts as a PKC delta activator, causing it to translocate from the cytosol to nucleus. Inhibition of PKC delta activation with rottlerlin, a PKC delta-specific inhibitor, abolished the zileuton-induced protection against H(2)O(2)-induced cell death and inhibited zileuton-induced COX-2 expression and PGE(2) production. The protective effect of zileuton was dramatically diminished by treatment with LY294002 or PD98059. Furthermore, zileuton-stimulated ERK1/2 and Akt phosphorylation was attenuated by rottlerin, indicating that PKC delta might act upstream of ERK1/2 and Akt. Moreover, inhibition of either ERK1/2 or Akt activation abolished zileuton-induced COX-2 expression. Knockdown of PKC delta with siRNA also reversed the protective effect of zileuton and blocked the induction of COX-2. These results suggest that zileuton-induced COX-2 expression is sequentially mediated through PKC delta-dependent activation of ERK1/2 and Akt. Based on these findings, we propose that zileuton might provide a new therapeutic strategy for ischemia/reperfusion injury of the heart.
Division of Cardiovascular Disease, Department of Biomedical Sciences, National Institutes of Health, 194 Tongillo, Eunpyung-gu, Seoul 122-701, Republic of Korea.
Hyun-Jeong
HJ
Kwak
Kyoung-Mi
KM
Park
Hye-Eun
HE
Choi
Hyun-Joung
HJ
Lim
Jin-Hee
JH
Park
Hyun-Young
HY
Park
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects*; D015232:Dinoprostone / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D051381:Rats
D016859:Lipoxygenase Inhibitors; D006861:Hydrogen Peroxide; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; C497260:Prkcd protein, rat; D051745:Protein Kinase C-delta; D015232:Dinoprostone; C063449:zileuton; D006918:Hydroxyurea