Kwak Hyun-Jeong, Park Kyoung-Mi, Choi Hye-Eun, Lim Hyun-Joung, Park Jin-Hee, Park Hyun-Young
Division of Cardiovascular Disease, Department of Biomedical Sciences, National Institutes of Health, 194 Tongillo, Eunpyung-gu, Seoul 122-701, Republic of Korea.
Cell Signal. 2010 Jan;22(1):80-7. doi: 10.1016/j.cellsig.2009.09.014. Epub 2009 Sep 22.
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.
齐留通已被证明可作为一种抗炎剂，因为它具有众所周知的抑制5-脂氧合酶（5-LO）的能力。然而，齐留通对心血管疾病和心肌细胞凋亡的影响尚不清楚。在此，我们研究了齐留通对心肌源性H9c2细胞和新生大鼠心肌细胞（NRCMs）凋亡的影响，并探讨了PKCδ介导的COX-2诱导在这些影响中的可能作用。用齐留通处理H9c2细胞可有效诱导COX-2表达和PGE(2)生物合成，且呈时间和剂量依赖性。齐留通还对H(2)O(2)诱导的氧化应激发挥了显著的保护作用，H(2)O(2)是体外再灌注损伤的模拟物，而这种保护作用被COX-2选择性抑制剂消除。当我们研究齐留通诱导COX-2表达所涉及的信号通路时，发现齐留通作为PKCδ激活剂，使其从胞质溶胶转位至细胞核。用PKCδ特异性抑制剂rottlerin抑制PKCδ激活，消除了齐留通对H(2)O(2)诱导的细胞死亡的保护作用，并抑制了齐留通诱导的COX-2表达和PGE(2)产生。用LY294002或PD98059处理可显著减弱齐留通的保护作用。此外，rottlerin减弱了齐留通刺激的ERK1/2和Akt磷酸化，表明PKCδ可能作用于ERK1/2和Akt的上游。此外，抑制ERK1/2或Akt激活可消除齐留通诱导的COX-2表达。用siRNA敲低PKCδ也可逆转齐留通的保护作用并阻断COX-2的诱导。这些结果表明，齐留通诱导的COX-2表达是通过PKCδ依赖性激活ERK1/2和Akt依次介导的。基于这些发现，我们提出齐留通可能为心脏缺血/再灌注损伤提供一种新的治疗策略。
