Mason R P, Mak I T, Trumbore M W, Mason P E
Department of Biochemistry and Medicine, MCP-Hahnemann University School of Medicine, Pittsburgh, Pennsylvania, USA.
Am J Cardiol. 1999 Aug 19;84(4A):16L-22L. doi: 10.1016/s0002-9149(99)00360-4.
The antioxidant activities of representative calcium antagonists, including amlodipine, verapamil, and diltiazem, were measured in hepatic microsomal membranes by the Fe-catalyzed, hydroxyl radical-producing system (dihydroxyfumarate + Fe3+) and assessed by malondialdehyde (MDA) formation. Despite the absence of L-type calcium channels in this membrane preparation, the calcium antagonists showed dose-dependent antioxidant activity. The biophysical mechanism for calcium-antagonist antioxidant activity was evaluated using radioligand binding assays, high-resolution differential scanning calorimetry, and small-angle x-ray diffraction approaches. These analyses demonstrated that calcium-antagonist antioxidant potency correlated directly with the compounds' relative affinity for the membrane lipid bilayer and ability to modulate membrane thermodynamic properties (amlodipine >> verapamil > diltiazem). The charged 1,4-dihydropyridine calcium antagonist, amlodipine, had the highest affinity for the membrane lipid bilayer (Kp>10(4)) and produced the largest changes in membrane thermodynamic properties, including a reduction in thermal phase transition temperature (-11%), enthalpy (-14%), and cooperative unit size (-59%), relative to control phosphatidylcholine liposomes. Electron density profiles generated from x-ray diffraction data demonstrated that amlodipine effected a broad and dose-dependent increase in molecular volume associated with the membrane hydrocarbon core. These data indicate that lipophilic calcium antagonists inhibit lipid peroxidation in cellular membranes as a result of modulating physicochemical properties of the membrane lipid bilayer, independently of calcium channel inhibition. Amlodipine had the most potent antioxidant activity as a result of distinct biophysical interactions with the membrane lipid bilayer. The nonreceptor-mediated antioxidant activity of calcium antagonists may contribute to cytoprotective mechanisms of action in cardiovascular diseases.
通过铁催化的羟基自由基生成系统（二羟基富马酸 + Fe3+）在肝微粒体膜中测定了包括氨氯地平、维拉帕米和地尔硫䓬在内的代表性钙拮抗剂的抗氧化活性，并通过丙二醛（MDA）的形成进行评估。尽管在此膜制剂中不存在 L 型钙通道，但钙拮抗剂仍表现出剂量依赖性的抗氧化活性。使用放射性配体结合测定、高分辨率差示扫描量热法和小角 X 射线衍射方法评估了钙拮抗剂抗氧化活性的生物物理机制。这些分析表明，钙拮抗剂的抗氧化效力与化合物对膜脂质双层的相对亲和力以及调节膜热力学性质的能力直接相关（氨氯地平 >> 维拉帕米 > 地尔硫䓬）。带电荷的 1,4 - 二氢吡啶类钙拮抗剂氨氯地平对膜脂质双层具有最高的亲和力（Kp>10(4)），并且相对于对照磷脂酰胆碱脂质体，在膜热力学性质上产生了最大的变化，包括热相变温度降低（-11%）、焓降低（-14%）和协同单元大小降低（-59%）。由 X 射线衍射数据生成的电子密度分布图表明，氨氯地平使与膜烃核心相关的分子体积产生广泛且剂量依赖性的增加。这些数据表明，亲脂性钙拮抗剂通过调节膜脂质双层的物理化学性质来抑制细胞膜中的脂质过氧化作用，而与钙通道抑制无关。由于与膜脂质双层存在独特的生物物理相互作用，氨氯地平具有最有效的抗氧化活性。钙拮抗剂的非受体介导的抗氧化活性可能有助于心血管疾病中的细胞保护作用机制。
