sCD40L调控斑块内胶原代谢网络的机制研究及干预策略

In recent years, theories about the role of extracellular matrix (ECM) in the pathogenesis of atherosclerosis have been developed. ECM components, especially collagen-is thought to be important in the progression of atherosclerosis and plaque rupture. The stability of plaques is maintained by a balanced ECM metabolism of production and degradation. Degradation of extracellular matrix by matrix metalloproteinases (MMPs) can lead to the progression of atherosclerosis and plaque rupture. MMP-2 and MMP-9 have been identified in human atherosclerotic lesions, and the enhanced expression of MMP-9 at the shoulders of these lesions has been linked to plaque rupture. Collagen biosynthesis involves a number of posttranslational modifications of procollagens and proteolytic conversion to collagens. The synthesis of all known types of collagen depends on prolyl 4-hydroxylase (P4H). P4H is composed of α and ? subunits; the α subunit is rate limiting and essential for collagen maturation and secretion. Inhibition of P4H produces unstable collagen associated with decreased collagen level. Various interleukins may participate in ECM metabolism by decreasing the activity of the type I isoenzyme of P4H. At present, many groups have studied the degradation of collagen, but it is not very clear about the relationship between a balanced ECM metabolism and the stability of plaques. Our previous findings suggest that inhibition of P4H associated with decreased collagen level, anti-inflammatory molecule overexpression could significantly increase collagen levels by inducing the expression of P4Hα1. CD40 ligand (CD40L) is a proin?ammatory mediator .CD40L interacts with CD40 resulting in various in?ammatory responses and platelet activation. Moreover, in the advanced stage of atherosclerosis, plaque rupture and a large amount of thrombus formation could lead to further increase of CD40L release. Therefore, the interaction between CD40L and CD40 may serve as a link between in?ammation, atherosclerosis, and thrombosis. Some reports have demonstrated the presence of cells expressing CD40 and MMP9 in atherosclerotic plaque of humans and in knock-out mice. A recent study also showed that disruption of the CD40-CD40L system can retard the initiation of arterial plaque formation. These observations provide compelling evidence that the CD40-CD40L system play major roles in the onset of atherosclerosis. However, the regulation of sCD40L on the extracellular matrix metabolism of the plaque is still not well-understood. In this present study, our objectives is to study the relationship of the CD40-CD40L system with the balanced extracellular matrix metabolism of plaque and the underlying molecular mechanisms of these effects. Our study will provide a new therapeutic target for preventive treatment of atherosclerosis.

动脉粥样硬化（AS）斑块内胶原的代谢平衡已成为近年来研究斑块不稳定发生机制的热点之一。胶原代谢平衡主要通过胶原合成与降解来调节，MMPs可降解细胞外基质导致斑块不稳定，P4Hα1则与胶原合成密切相关。研究表明多种炎症因子通过影响胶原代谢而导致斑块不稳定。sCD40L是AS的炎症免疫调节中的重要的细胞因子，研究发现，sCD40L可通过调节MMPs在斑块中表达来影响AS斑块的稳定性，但sCD40L与P4Hα1关系目前尚未见报道。我们前期研究发现抑制P4Hα1会使胶原产生减少，而P4Hα1基因的过表达则和胶原产生过量有关，研究还发现抗炎因子过表达能显著增加斑块及HASMCs内P4Hα1表达及胶原含量。但sCD40L能否同时调控MMPs、P4Hα1表达目前尚不明确。因此，本研究拟从体内和体外两个水平观察sCD40L与MMPs、P4Hα1表达的关系及可能的作用机制，旨在为防治AS带来新的治疗靶点。

背景：动脉粥样硬化（AS）的发病机制十分复杂,斑块内胶原的代谢平衡已成为近年来研究斑块不稳定发生机制的热点之一。胶原代谢平衡主要通过胶原合成与降解来调节，MMPs可降解细胞外基质导致斑块不稳定，P4Hα1则与胶原合成密切相关，炎症因子可抑制P4Hα1表达而导致胶原产生减少。sCD40L是AS的炎症免疫调节中的重要的细胞因子，几乎贯穿整个动脉粥样硬化发生发展乃至斑块破裂的全过程，他汀类药物除具有降脂作用，尚可发挥巨大的抗炎和免疫调节效应，研究发现，短期内应用大剂量他汀类药物可能会减少冠状动脉粥样斑块基质成分降解和炎症反应,并更有效地降低心血管事件的发生率。本研究拟从体内和体外两个水平观察炎性细胞因子sCD40L与MMPs、P4Hα1表达的关系及可能的作用机制及他汀类药物的干预作用，旨在为防治AS带来新的治疗靶点。方法：通过对颈动脉斑块行组织病理学分析观察斑块的形态学变化，明确sCD40L调控斑块内胶原代谢网络的作用；探讨sCD40L调控胶原代谢网络稳态过程的信号传导途径；观察瑞舒伐他汀钙能否抑制rhCD40L的不良调控作用。结果：体内研究结果显示：CD40L过表达有较高的不稳定斑块的发生率，斑块内炎症因子、巨噬细胞、脂质含量增加，平滑肌细胞和胶原含量降低，弹力纤维断裂增加，斑块内铁沉积增多，平均纤维帽厚度，纤维帽面积和帽/核比值降低，斑块内P4Hα1、胶原Ⅰ和Ⅲ含量降低，MMP2、MMP9活性增加，瑞舒伐他汀钙能显著逆转sCD40L的上述不良作用。体外研究结果显示：rhCD40L对P4Hα1作用呈浓度和时间依赖性，MMP2表达未呈时间和浓度依赖性，MMP9未见表达，TRAF6-MAPKs-NF-κB这一信号传导途径参与了rhCD40L调控平滑肌细胞胶原代谢网络的过程。瑞舒伐他汀钙能显著逆转rhCD40L的不良调控作用。结论： CD40L过表达能通过调控斑块内胶原代谢网络从而使动脉粥样硬化斑块纤维帽变薄，易损性增加，稳定性显著降低；TRAF6-JNK-NF-κB参与了CD40L过表达胶原代谢网络的过程；瑞舒伐他汀钙能显著抑制rhCD40L的上述不良作用。本研究必将为探寻到稳定易损斑块的新策略，扩展抗动脉粥样硬化作用的新思路，早期认识并及时干预冠状动脉粥样硬化并发症的发生，有效阻止ACS的发生发展提供重要的理论依据。