Seidlmayer Lea K, Juettner Vanessa V, Kettlewell Sarah, Pavlov Evgeny V, Blatter Lothar A, Dedkova Elena N
Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
Institute of Cardiovascular and Medical Sciences, College of Veterinary Medical and Life Sciences, University of Glasgow, Glasgow, UK.
Cardiovasc Res. 2015 May 1;106(2):237-48. doi: 10.1093/cvr/cvv097. Epub 2015 Mar 5.
The mitochondrial permeability transition pore (mPTP) plays a central role for tissue damage and cell death during ischaemia-reperfusion (I/R). We investigated the contribution of mitochondrial inorganic polyphosphate (polyP), a potent activator of Ca(2+)-induced mPTP opening, towards mPTP activation and cardiac cell death in I/R.
A significant increase in mitochondrial free calcium concentration ([Ca(2+)]m), reactive oxygen species (ROS) generation, mitochondrial membrane potential depolarization (ΔΨm), and mPTP activity, but no cell death, was observed after 20 min of ischaemia. The [Ca(2+)]m increase during ischaemia was partially prevented by the mitochondrial Ca(2+) uniporter (MCU) inhibitor Ru360 and completely abolished by the combination of Ru360 and the ryanodine receptor type 1 blocker dantrolene, suggesting two complimentary Ca(2+) uptake mechanisms. In the absence of Ru360 and dantrolene, mPTP closing by polyP depletion or CSA decreased mitochondrial Ca(2+) uptake, suggesting that during ischaemia Ca(2+) can enter mitochondria through mPTP. During reperfusion, a burst of endogenous polyP production coincided with a decrease in [Ca(2+)]m, a decline in superoxide generation, and an acceleration of hydrogen peroxide (H2O2) production. An increase in H2O2 correlated with restoration of mitochondrial pHm and an increase in cell death. mPTP opening and cell death on reperfusion were prevented by antioxidants Trolox and MnTBAP [Mn (III) tetrakis (4-benzoic acid) porphyrin chloride]. Enzymatic polyP depletion did not affect mPTP opening during reperfusion, but increased ROS generation and cell death, suggesting that polyP plays a protective role in cellular stress response.
Transient Ca(2+)/polyP-mediated mPTP opening during ischaemia may serve to protect cells against cytosolic Ca(2+) overload, whereas ROS/pH-mediated sustained mPTP opening on reperfusion induces cell death.
线粒体通透性转换孔（mPTP）在缺血再灌注（I/R）过程中的组织损伤和细胞死亡中起核心作用。我们研究了线粒体无机多聚磷酸盐（polyP）（一种Ca²⁺诱导的mPTP开放的有效激活剂）对I/R中mPTP激活和心脏细胞死亡的作用。
缺血20分钟后，观察到线粒体游离钙浓度（[Ca²⁺]m）显著升高、活性氧（ROS）生成增加、线粒体膜电位去极化（ΔΨm）和mPTP活性增加，但未观察到细胞死亡。线粒体Ca²⁺单向转运体（MCU）抑制剂Ru360部分阻止了缺血期间[Ca²⁺]m的增加，而Ru360与1型兰尼碱受体阻滞剂丹曲林的联合使用则完全消除了这种增加，提示存在两种互补的Ca²⁺摄取机制。在没有Ru360和丹曲林的情况下，通过polyP耗竭或环孢菌素A（CSA）关闭mPTP会减少线粒体Ca²⁺摄取，提示在缺血期间Ca²⁺可通过mPTP进入线粒体。在再灌注期间，内源性polyP的爆发与[Ca²⁺]m的降低、超氧化物生成的减少以及过氧化氢（H₂O₂）生成的加速同时发生。H₂O₂的增加与线粒体pHm的恢复以及细胞死亡的增加相关。抗氧化剂曲克芦丁（Trolox）和四（4-苯甲酸）锰（III）卟啉氯化物（MnTBAP）可防止再灌注时mPTP开放和细胞死亡。酶促polyP耗竭不影响再灌注期间mPTP的开放，但会增加ROS生成和细胞死亡，提示polyP在细胞应激反应中起保护作用。
缺血期间短暂的Ca²⁺/polyP介导的mPTP开放可能有助于保护细胞免受胞质Ca²⁺过载的影响，而再灌注时ROS/pH介导的持续性mPTP开放则诱导细胞死亡。
