HO-1CO系统在缺血再灌注中的保护机制.doc

HO-1/CO系统在缺血再灌注中的保护机制重庆医科大学附属第一医院麻醉科 400016刘力 闵苏【摘要】 缺血再灌注(I/R)损伤是心肌梗死等许多疾病的病理生理基础，也是手术、创伤、休克以及器官移植导致器官功能和结构损伤的原因之一。在已知的缺血再灌注损伤的众多病理机制中已经明确氧化应激产生的活性氧自由基和炎症反应具有重要的作用。血色素氧合酶-1(Heme oxygenase-1 HO-1)是催化血色素降解生成胆绿素、一氧化碳（carbon monoxide CO），并释放Fe2+离子。近年来的研究已经证明HO-1及其催化产物CO具有抗氧化应激和抗炎作用，在I/R损伤中能够发挥对组织器官的保护作用。本文就I/R损伤中HO-1/CO系统的保护作用进行综合阐述。【关键词】 血红素氧合酶 一氧化碳 缺血再灌注Mechanism of HO-1/CO system protective effection in ischemia/reperfusion Li liu Su min (Department of Anesthesiology ,The First Affiliated Hospital of Chongqing Medical University)【Abstract】 Ischemia/reperfusion (I/R) injury occurs frequently in a variety of clinical settings, including myocardial infarction, surgery, trauma,shock, and organ transplantation. Although the exact mechanisms involved in the pathogenesis of I/R injury have not been fully elucidated, it is generally believed that pro-inflammatory cytokines, and mediators generated in the setting of oxidative stress, such as reactive oxygen species (ROS), play important roles. Heme oxygenase (HO) is the rate-limiting enzyme that catalyzes the degradation of heme into equimolar quantities of biliverdinand carbon monoxide (CO), while the iron is released. HO-1, biliverdin, and CO, have been shown to possess generalized endogenous anti-inflammatory activities and provide protection against I/R injury. Further, recent observations have demonstrated that exogenous HO-1 expression, as well as exogenously administered CO have potent cytoprotective effects on I/R injury as well. we summarize the currently available data regarding the role of the HO/CO system in the prevention I/R injury.【Key word】 Heme oxygenase carbon monoxide ischemia-reperfusion缺血再灌注(I/R)损伤是在可逆的组织器官缺血损伤的基础上发展成为不可逆的细胞功能代谢障碍和结构破坏的病理生理过程。尽早恢复缺血组织的血流又防止再灌注损伤的发生是亟待解决的重要课题。近年来，对血色素氧合酶（Heme oxygenase HO）的研究日益受到人们的重视，其抗氧化应激；抗炎症；抗细胞凋亡以及抗血小板聚集作用被广泛的用于缺血再灌注损伤的研究，为许多疾病的诊疗和围术期组织器官的保护提供一个新的探索方向。1. 概述血色素氧合酶（HO）是血红素代谢的限速酶，能够催化血红素代谢生成具有抗氧化作用的胆绿素、Fe2+、CO，参与机体抗氧化反应。HO有三类形式同工酶：HO-1，HO-2，HO-31。其中以HO-1在体内分布最为广泛，能够接受各种应激刺激诱导其表达增强，比如缺氧、ROS、细胞因子、NO、重金属离子、紫外线A（320-380nm）、层流剪应力、过氧化氢及硫氢基（SH）活性物质1,2,3。CO是机体内重要的气体信号传导分子，具有重要的生理作用。HO-1/CO的表达调控作为一种防御机制在对抗氧化应激、炎症、缺血再灌注中均有重要作用。2. HO-1/CO抗I/R损伤机制活性氧自由基的破坏，炎症反应以及细胞凋亡在I/R的损伤机制中有重要作用。HO-1/CO发挥抗炎；抗氧化；调控细胞增殖凋亡等作用，干预I/R损伤的各个环节，发挥保护组织器官结构和功能的作用。2.1 抗氧化作用血红素是体内的强氧化剂，不仅可以穿过细胞膜直接催化ROS生成3还能增加细胞对氧化的敏感性。HO直接参与血红素的清除，将其转化为具有抗氧化作用的胆绿素，胆红素，Fe2+，CO。胆红素和胆绿素能抑制脂类过氧化物的形成1,4，Fe2+能增加铁蛋白结合游离铁发挥抗氧化作用4。由于HO-1接受刺激的多样性，其作用机制与多个通路的激活有关，包括依赖于NF-B的通路，依赖于sGC的通路，Akt-eNOS通路以及MAPKs传导通路5。其中MAPKs通路是研究最多也是最为重要的通路。MAPKs是生物体普遍存在的信号传导系统，调节各种细胞的生长，凋亡，分化以及对环境和刺激的反应。MAPKs包括三个主要的通路：ERK，JNK，p38。以p38MAPK与HO-1/CO的关系最紧密。细胞氧化反应核心调节因子（Nrf2）是HO-1表达最常见的转录因子，MAPK的磷酸化影响Nrf2在亚细胞结构上的定位和与辅激活蛋白的相互作用6,7。CO激活p38MAPK以及上游激酶MKK3，下调ERK1/2,JNK通路，调控介质、酶等的表达。p38MAPK活化后，CO与启动子区不同反应元件结合的中间分子介导不同蛋白合成。CO与鸟苷酸环化酶sGC的亚铁血红素部位结合，使sGC构象发生变化, 酶的活化中心暴露, 三磷酸鸟苷(guanosin tirphosphate, GPT)转变成cGMP ，增加的cGMP降低胞浆内的钙离子浓度松弛血管平滑肌，改善微循环8；另一方面激活PKG，发挥其在神经和血管方面的作用9。sGC通过p38MAPK途径发挥抗炎和抗凋亡作用，有利于线粒体膜及细胞膜的稳定，使细胞膜通透性减小。另外，J. L. Scragg 10研究认为CO 能够与L型Ca2+通道的胞内C末端的三个半胱氨酸残基拼接插入，导致通道的阻滞。使用线粒体电子传递链的复合物III和MitoQ的阻断剂能够消除CO的抗氧化作用，说明CO可逆性的抑制L型Ca2+通道可能减轻I/R损伤后细胞内的Ca2+超载。2.2 抗炎作用HO-1/CO通过P38MAPK信号传导通路下调TNF-,IL-6的表达已经得到证实。近年来的研究发现HO-1/CO实际上能抑制大多数血管因子和炎性因子的作用，比如促炎因子IL-1、COX-2，Th1型细胞因子IL-2、IFN- 以及血管因子ICAM-1和炎症趋化因子。S. Basuroy等11在实验中发现CO和胆绿素的抗炎作用与其抑制NOX4活性有关。而HO-1能加强CD163与血红蛋白结合释放抗炎因子IL-1012。小窝蛋白-1（Caveolin-1 Cav-1）是肿瘤抑制基因蛋白，能够调节下游的信号通路。Cav-1绑定于TLR-4能抑制LPS诱发促炎因子TNF-和IL-6生成， 促进HO-1通过p38MAPK通路被转运到细胞质模微囊，下调促炎信号。CO可扩大Cav-1/ TLR-4的相互作用促进抗炎因子的释放13,14。新近研究发现HO-1可以通过诱导衰变加速因子（DAF）调节补体激活，通过增加DAF的表达，增强抗C3沉积和抗补体介导的溶胞作用。除HO-1之外，胆红素，Fe螯合物以及铁蛋白重链也能诱导内皮细胞DAF的表达。2.3 抗凋亡作用HO-1和CO影响许多细胞的生长周期，调控细胞的增殖，调节细胞内的信号传导。CO能够抑制TNF-引起的鼠成纤维细胞和内皮细胞凋亡。HO-1通过激活P38MAPK通路上调HSP1和HSP70的表达，对抗TNF-启动的细胞死亡程序。胰星状细胞在胰腺炎和胰腺癌的病理发展中具有特殊的重要地位，Schwer 等15发现HO-1能够通过抑制ERK信号通路抑制胰星状细胞的增殖。胰岛素延缓糖尿病微血管病变发展的机制与HO-1作用有关，胰岛素表现出的抗凋亡作用与激活IRS1/P3K/Akt2诱导HO-1mRNA表达增强有关16。HO-1的诱导可加速血管内皮细胞的增殖周期而抑制平滑肌细胞的增殖，过表达的HO-1激活sGC通过p38MAPK通路上调P21促进新生血管的生成17。HO-1能上调bcl-2蛋白并抑制p53蛋白核内聚集，这些产物在细胞的存活和凋亡中起有重要作用。在中枢神经的研究中，增加的HO-1能够增强神经元BDNF的表达和星状细胞BDNF、GDNF的表达18。在肺I/R的动物试验中，CO能够激活p38MAPK以及上游激酶MKK3，而抑制胞外信号传导激酶，激活c-JunN-终末蛋白激酶，抑制Fas/FasL的表达和凋亡相关基因caspase-3，-8，-9以及线粒体细胞色素c的释放，抑制Bcl-2蛋白和聚ADP核糖聚合酶裂解19。体外研究还表明CO的抗凋亡还与磷酸酰肌醇-3激酶/Akt和依赖p38MAPK的信号转导及转录激活子-3的激活有关20。2.4 抗血栓作用HO-1CO的抗血栓作用主要通过一下几个方面实现。一是当诱因持续作用时，微血管内皮细胞内HO-1诱导表达增加，使得内皮细胞对氧化物质导致的白细胞黏附的敏感性降低4,21。二是CO通过可溶性鸟苷酸环化酶(sGC)提高细胞内环鸟苷酸(cGMP)的水平，进而降低胞浆内的钙离子浓度，抑制血小板凝集与活化的作用9,10,22。三是HO-1保护血管内皮的完整性，减弱血小板激活以及限制TF、vWF和纤溶酶原激活物抑制物-1的表达，纤溶酶原激活物抑制物-1直接参与血栓形成，而TF、vWF通过作用于纤维蛋白和凝血连锁反应易化血栓形成，CO可以抑制MAPK驱动的Egr-1表达，从而抑制TF。通过吸入CO和给予胆红素可以明显减轻炎症组织内血管血栓形成4,21,23。3. HO-1/CO与I/R的器官保护动物实验已经证明HO-1CO对脑，心脏，肺，肾，小肠在I/R损伤中具有重要的保护作用。在严重创伤，出血性休克，器官移植中HO-1CO能够保护组织器官结构功能，具有特殊的应用价值。吸入CO可以减少心脏I/R损伤后心肌梗死面积，抑制肺I/R损伤中性粒细胞的浸润，保护小肠I/R损伤后黏膜的破环。氧自由基和促炎介质是移植器官缺血再灌注损伤中诱导细胞凋亡的最强刺激因素，氧自由基和促炎介质直接损伤核酸、蛋白质和脂质，活化凋亡蛋白酶和核酸内切酶，加速凋亡相关基因表达，诱发细胞凋亡。HO-1/CO系统具有下调促炎介质，增加抗炎细胞因子，抑制中性粒细胞的活化及与内皮细胞的黏附减少炎症细胞浸润的作用。对HO-1/CO系统的深入研究可能为器官移植的保护提供了新的探索途径。随着对CO在体内发挥抗氧化和抗凋亡作用认识的加深，吸入CO已用于临床的研究。报告表明吸入100-125ppmCO对慢性阻塞性肺炎的病人有益 24 ，使用水溶CO释放剂也可以减轻LTP毒性，改善术后肠梗阻的发生25,26。CO还用于骨髓移植造血干细胞的保护27以及控制肿瘤的侵袭和转移28。4 小结HO-1CO系统的抗氧化应激、抗炎症损伤、抑制血小板聚集、调控细胞增殖和凋亡等作用日益受到国内外专家的关注。对HO-1CO系统保护机制的研究为某些疾病的治疗，术中重要器官的保护，危重病人和移植术后的全身器官功能调节提供新的思路和理论基础。然而，HO-1CO系统错综复杂的作用机制仍然尚未完全清楚，而其临床应用虽迈开了第一步，但其有效性和安全性也仍需进一步探究。【参考文献】1. Stefan W. Ryter, Jawed Alam , Augustine, Heme Oxygenase-1/Carbon Monoxide: From Basic Science to Therapeutic ApplicationsJ, Physiol,2006, 86: 583-6502. Slebos DJ，RyterSW ，ChoiMK. Hemin oxygenase-1 and carbonmonoxide in pulmonary medicineJRespir Res，2003，4(1)：7-123. Z. Han, S. Varadharaj, R. J. Giedt, J. L. 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