A new Chinese herb-derived selective Toll-like receptor antagonist (Project 1)

摘要： 动脉粥样硬化是心脏病发作和中风的直接原因，在美国，这两种疾病分别是头号和第三大杀手。这是脂肪沉积和慢性血管炎症共同作用的结果。Toll样受体(Toll-like Receptor，TLRs)是天然免疫的关键成分，在动脉粥样硬化的各个阶段都发挥着有害的作用，其中Toll样受体TLR2和TLR4的研究最多。在参与防御入侵病原体的第一道防线的同时，TLR2和TLR4介导的信号被认为是动脉粥样硬化形成的驱动力。因此，阻断TLR2和TLR4信号是治疗动脉粥样硬化的一种有趣的方法。然而，目前还没有TLR2或TLR4拮抗剂被批准用于临床。最近，为了从常用中草药三棱中分离和鉴定单一化合物，我们获得了一个新的化合物，命名为玄参甲素B(SsnB)，并有了令人兴奋的发现。我们的初步研究表明：1)丹参皂苷B通过选择性阻断TLR2和TLR4信号通路对巨噬细胞具有明显的抗炎作用；2)丹参皂苷B能降低活化内皮细胞吸引单核细胞黏附的能力，并减少动脉平滑肌细胞的迁移；3)丹参皂苷B能有效抑制小鼠对脂多糖(LPS)的炎症反应。在这些初步数据的基础上，我们假设SSnB可以通过选择性地抑制TLR2和TLR4信号通路而被开发为抗炎和抗动脉粥样硬化的药物。为了检验这一假设，我们提出了三个具体目标。SA1.目的：阐明SSNB阻断TLR2和TLR4信号的分子机制。我们将表达和纯化TLRs的Toll/IL-1受体(TIR)结构域、适配蛋白TIRAP/MAL和MyD88，并检测SSNB与这些蛋白的结合。SA2.目的：研究丹参皂苷B对血管细胞的影响。我们将验证SSNB通过阻断TLR2和TLR4信号来抑制动脉内皮细胞和平滑肌细胞炎症表型的假设。SA3.验证SSNB抑制小鼠动脉粥样硬化形成的假说。低密度脂蛋白受体(LDLR)缺陷小鼠将通过高脂饮食诱导高胆固醇血症和动脉粥样硬化。SSNB将被用来测试它是否能减弱这些小鼠的动脉粥样硬化形成。综上所述，本研究将测试我们最近分离和表征的一种新的天然化合物的抗炎和抗动脉粥样硬化作用。SSnB通过阻断巨噬细胞和驻留血管细胞中的TLR2和TLR4信号而具有抗炎和抗动脉粥样硬化作用的假说的证实，将使该化合物发展成为抗动脉粥样硬化的药物。这项研究还将为补充和替代医学与现代药理学之间的桥梁提供一个新的范例。

Abstract: Atherosclerosis is the direct cause of heart attack and stroke, the No. 1 and No. 3 killers in the United States, respectively. It is the result of both lipid deposition and chronic vascular inflammation. Toll-like receptors (TLRs), the key components of innate immunity, play detrimental roles in every stage of atherosclerosis, with TLR2 and TLR4 being best documented. While participating in the first line of defense against invading pathogens, TLR2- and TLR4-mediated signaling is considered to be a driving force in atherogenesis. Thus, blockade of TLR2 and TLR4 signaling is an intriguing therapeutic approach for atherosclerosis. However, no TLR2 or TLR4 antagonists are currently approved for clinic use. Recently, in an effort to isolate and characterize single compounds from Sparganium stoloniferum tubers, a commonly used Traditional Chinese Medicine herb, we obtained a novel compound, designated Sparstolonin B (SsnB), and made exciting discoveries. Our preliminary studies show that 1) SsnB has potent anti-inflammatory effects on macrophages by selectively blocking TLR2 and TLR4 signaling; 2) SsnB diminishes the ability of activated endothelial cells to attract monocytes for adhesion, and decreases arterial smooth muscle cell migration; and 3) SsnB effectively suppresses inflammatory response to lipopolysaccharide (LPS) in mice. On the basis of these preliminary data, we hypothesize that SsnB can be developed as an anti-inflammatory and anti-atherogenic agent by virtue of its selective inhibitory effects on TLR2 and TLR4 signaling. To test this hypothesis, we propose three specific aims. SA1. To elucidate the molecular mechanism by which SsnB blocks TLR2 and TLR4 signaling. We will express and purify the Toll/IL-1 receptor (TIR) domains of TLRs, the adaptor proteins TIRAP/Mal and MyD88, and examine the binding of SsnB to these proteins. SA2. To examine the effects of SsnB on resident vascular cells. We will test the hypothesis that SsnB suppresses the inflammatory phenotype in arterial endothelial and smooth muscle cells by blocking TLR2 and TLR4 signaling. SA3. To test the hypothesis that SsnB attenuates atherogenesis in mice. LDL receptor (LDLR) deficient mice will be fed high fat diet to induce hypercholesterolemia and atherosclerosis. SsnB will be administrated to test if it attenuates atherogenesis in these mice. In summary, this study will test the anti-inflammatory and anti-atherogenic effects of a new natural compound recently isolated and characterized by us. The confirmation of the hypothesis that SsnB has anti-inflammatory and anti-atherogenic merit by blocking TLR2 and TLR4 signaling in macrophages and resident vascular cells will usher the development of this compound into an anti-atherogenic agent. This study will also provide a new example of complementary and alternative medicine bridging with modern pharmacology.