Departments of Pharmacology, Pathology, and Medicine, Vanderbilt University, Nashville, Tennessee 37232-6602, USA.
Chem Res Toxicol. 2010 Jan;23(1):240-50. doi: 10.1021/tx900407a.
Expression of cyclooxygenase-2 (COX-2) is associated with the development of many pathologic conditions. The product of COX-2, prostaglandin H(2) (PGH(2)), can spontaneously rearrange to form reactive gamma-ketoaldehydes called levuglandins (LGs). This gamma-ketoaldehyde structure confers a high degree of reactivity on the LGs, which rapidly form covalent adducts with primary amines of protein residues. Formation of LG adducts of proteins has been demonstrated in pathologic conditions (e.g., increased levels in the hippocampus in Alzheimer's disease) and during physiologic function (platelet activation). On the basis of knowledge that lipid modification of proteins is known to cause their translocation and to alter their function, we hypothesize that modification of proteins by LG could have functional consequences. Testing this hypothesis requires an experimental approach that discriminates between the effects of protein modification by LG and the effects of cyclooxygenase-derived prostanoids acting through their G-protein coupled receptors. To achieve this goal, we have synthesized and evaluated a series of scavengers that react with LG with a potency more than 2 orders of magnitude greater than that with the epsilon-amine of lysine. A subset of these scavengers are shown to block the formation of LG adducts of proteins in cells without inhibiting the catalytic activity of the cyclooxygenases. Ten of these selective scavengers did not produce cytotoxicity. These results demonstrate that small molecules can scavenge LGs in cells without interfering with the formation of prostaglandins. They also provide a working hypothesis for the development of pharmacologic agents that could be used in experimental animals in vivo to assess the pathophysiological contribution of levuglandins in diseases associated with cyclooxygenase up-regulation.
环氧合酶-2（COX-2）的表达与许多病理状况的发展有关。COX-2 的产物，前列腺素 H2（PGH2），可以自发重排形成称为莱格朗丁（LGs）的反应性γ-酮醛。这种γ-酮醛结构赋予 LGs 高度的反应性，它们可以迅速与蛋白质残基的伯胺形成共价加合物。在病理条件下（例如阿尔茨海默病患者的海马体中水平升高）和生理功能（血小板激活）中已经证明了 LG 与蛋白质形成加合物。基于已知脂质修饰蛋白质会导致其易位并改变其功能的知识，我们假设 LG 修饰蛋白质可能具有功能后果。测试这一假设需要一种实验方法，该方法可以区分 LG 对蛋白质的修饰作用和通过其 G 蛋白偶联受体起作用的环氧化酶衍生的前列腺素的作用。为了实现这一目标，我们已经合成并评估了一系列与 LG 反应的清除剂，其与 LG 的反应活性比与赖氨酸的ε-胺的反应活性高两个数量级以上。这些清除剂的一部分被证明可以阻止 LG 与蛋白质形成加合物，而不会抑制环氧化酶的催化活性。其中十种选择性清除剂不会产生细胞毒性。这些结果表明，小分子可以在细胞中清除 LG，而不会干扰前列腺素的形成。它们还为开发药理学药物提供了一个工作假设，这些药物可用于体内实验动物，以评估与 COX-2 上调相关的疾病中莱格朗丁的病理生理贡献。
