Larsson David A, Baird Sarah, Nyhalah Jerome Diinga, Yuan Xi-Ming, Li Wei
Division of Experimental Pathology, Department of Neuroscience and Locomotion, Faculty of Health Sciences, Linköping University, 581 85 Linköping, Sweden.
Free Radic Biol Med. 2006 Sep 15;41(6):902-10. doi: 10.1016/j.freeradbiomed.2006.05.032. Epub 2006 Jun 6.
Apoptotic cells in atheroma lesions may contribute to plaque development and instability. Oxysterols constitute the major toxic component in oxLDL and are present in mixed forms in human atheroma lesions. However, the cellular effects of oxysterols have been mostly studied individually. In the present study, we investigated the cytotoxic effects of 7beta-hydroxycholesterol (7betaOH), 7-ketocholesterol (7keto), 25-hydroxycholesterol (25OH), and 27-hydroxycholesterol (27OH) on U937 monocytic cells, both individually and in atheroma-relevant mixtures mimicking the oxysterol composition reported in human atheroma lesions. Apoptosis and necrosis were studied by examining cell morphology, phosphatidylserine exposure, caspase activation, and the terminal dUTP nick end-labeling technique. Cellular reactive oxygen species and total amount of reduced thiols were measured by using fluorescence probes and 5,5'-dithiobis-(2-nitrobenzoic acid), respectively. We found that 7betaOH and 7keto induced caspase activation, ROS production, cellular thiol depletion, permeabilization of lysosomal and mitochondrial membranes, and cell death. 25OH and 27OH did not cause any of the above alterations, whereas 7betaOH and 7keto exerted synergistic toxic effects. Although single 25OH or 27OH exhibited quenching effects on both 7betaOH- and 7keto-induced cell death, the combination of all four oxysterols in atheroma-relevant proportions was proapoptotic. Our findings indicate that the major oxysterols accumulated in human atheroma are proapoptotic and may contribute to atherosclerotic lesion development.
动脉粥样硬化斑块病变中的凋亡细胞可能会促进斑块的发展和不稳定。氧化甾醇是氧化型低密度脂蛋白中的主要毒性成分，以混合形式存在于人类动脉粥样硬化斑块病变中。然而，氧化甾醇的细胞效应大多是单独研究的。在本研究中，我们分别以及以模拟人类动脉粥样硬化斑块病变中报道的氧化甾醇组成的动脉粥样硬化相关混合物的形式，研究了7β-羟基胆固醇（7βOH）、7-酮胆固醇（7keto）、25-羟基胆固醇（25OH）和27-羟基胆固醇（27OH）对U937单核细胞的细胞毒性作用。通过检查细胞形态、磷脂酰丝氨酸暴露、半胱天冬酶激活和末端脱氧核苷酸转移酶介导的缺口末端标记技术来研究细胞凋亡和坏死。分别使用荧光探针和5,5'-二硫代双（2-硝基苯甲酸）测量细胞活性氧和还原型硫醇的总量。我们发现，7βOH和7keto可诱导半胱天冬酶激活、活性氧生成、细胞硫醇消耗、溶酶体和线粒体膜通透性增加以及细胞死亡。25OH和27OH未引起上述任何改变，而7βOH和7keto具有协同毒性作用。尽管单一的25OH或27OH对7βOH和7keto诱导的细胞死亡均表现出淬灭作用，但四种氧化甾醇以动脉粥样硬化相关比例组合时具有促凋亡作用。我们的研究结果表明，在人类动脉粥样硬化斑块中积累的主要氧化甾醇具有促凋亡作用，可能有助于动脉粥样硬化病变的发展。
