Gao Qin, Zhang Shi-Zhong, Cao Chun-Mei, Bruce Iain C, Xia Qiang
Department of Physiology, Zhejiang University School of Medicine, 353 Yan-an Road, Hangzhou 310031, China.
Cytokine. 2005 Dec 7;32(5):199-205. doi: 10.1016/j.cyto.2005.09.008. Epub 2005 Nov 2.
Pretreatment with tumor necrosis factor-alpha (TNF-alpha) is known to trigger cardioprotection and it can activate multiple downstream signaling cascades. However, it is not known whether the mitochondrial permeability transition pore and the Ca(2+)-activated K(+) channel (K(Ca) channel) are involved in the TNF-alpha-induced cardioprotection. In the present study, we examined whether TNF-alpha inhibits pore opening and activates the K(Ca) channel in the cardioprotection. In isolated rat hearts subjected to 30 min of regional ischemia and 120 min of reperfusion, pretreatment with 10 U/ml TNF-alpha for 7 min followed by 10 min washout improved the recovery of rate-pressure product (RPP=left ventricular developed pressure x heart rate) and coronary flow (CF) during reperfusion, and reduced the infarct size and release of lactate dehydrogenase (LDH). Administration of 20 micromol/L atractyloside, a pore opener, for the last 5 min of ischemia and first 15 min of reperfusion, and pretreatment with 1 micromol/L paxilline, an inhibitor of the K(Ca) channel, for 5 min before ischemia, attenuated the recovery of RPP and CF, and the reductions of infarct size and release of LDH induced by TNF-alpha. On the other hand, administration of 10 micromol/L NS 1619, an opener of the K(Ca) channel, for 10 min before ischemia, decreased the infarct size and LDH release, and improved contractile functions and CF; these effects were attenuated by atractyloside. Pretreatment with 0.2 micromol/L cyclosporin A for the last 5 min of ischemia and first 15 min of reperfusion showed similar effects to those of TNF-alpha, and they were not attenuated by paxilline. In mitochondria isolated from hearts pretreated with 10 U/ml TNF-alpha for 7 min, a significant inhibition of Ca(2+)-induced swelling was observed. Furthermore, paxilline attenuated the inhibition of Ca(2+)-induced mitochondrial swelling by TNF-alpha. These findings indicate that TNF-alpha protects the myocardium against ischemia and reperfusion injury by inhibiting mitochondrial permeability transition pore opening as well as activating K(Ca) channels, probably the mitochondrial K(Ca) channel, which is upstream from the pore.
已知用肿瘤坏死因子-α（TNF-α）进行预处理可引发心脏保护作用，并且它能激活多个下游信号级联反应。然而，线粒体通透性转换孔和钙激活钾通道（KCa通道）是否参与TNF-α诱导的心脏保护作用尚不清楚。在本研究中，我们检测了TNF-α在心脏保护过程中是否抑制孔开放并激活KCa通道。在经历30分钟局部缺血和120分钟再灌注的离体大鼠心脏中，用10 U/ml TNF-α预处理7分钟，随后冲洗10分钟，可改善再灌注期间心率血压乘积（RPP =左心室舒张末压×心率）和冠脉流量（CF）的恢复，并减小梗死面积和降低乳酸脱氢酶（LDH）的释放。在缺血的最后5分钟和再灌注的最初15分钟给予20 μmol/L的苍术苷（一种孔开放剂），以及在缺血前5分钟用1 μmol/L的派迷清（一种KCa通道抑制剂）预处理5分钟，可减弱TNF-α诱导的RPP和CF的恢复以及梗死面积和LDH释放的减少。另一方面，在缺血前10分钟给予10 μmol/L的NS 1619（一种KCa通道开放剂）10分钟，可减小梗死面积和LDH释放，并改善收缩功能和CF；这些作用被苍术苷减弱。在缺血的最后5分钟和再灌注的最初15分钟用0.2 μmol/L环孢素A预处理显示出与TNF-α相似的作用，并且它们未被派迷清减弱。在用10 U/ml TNF-α预处理7分钟的心脏分离出的线粒体中，观察到对钙诱导肿胀的显著抑制。此外，派迷清减弱了TNF-α对钙诱导的线粒体肿胀的抑制作用。这些发现表明，TNF-α通过抑制线粒体通透性转换孔开放以及激活KCa通道（可能是线粒体KCa通道，其位于孔的上游）来保护心肌免受缺血再灌注损伤。
