Lloyd Mitchell M, Grima Michael A, Rayner Benjamin S, Hadfield Katrina A, Davies Michael J, Hawkins Clare L
The Heart Research Institute, Newtown, Sydney, NSW 2042, Australia.
The Heart Research Institute, Newtown, Sydney, NSW 2042, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia.
Free Radic Biol Med. 2013 Dec;65:1352-1362. doi: 10.1016/j.freeradbiomed.2013.10.007. Epub 2013 Oct 10.
In the immune response, hypohalous acids are generated by activated leukocytes via the release of myeloperoxidase and the formation of H2O2. Although these oxidants have important bactericidal properties, they have also been implicated in causing tissue damage in inflammatory diseases, including atherosclerosis. Hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN) are the major oxidants formed by myeloperoxidase under physiological conditions, with the ratio of these oxidants dependent on diet and smoking status. HOCl is highly reactive and causes marked cellular damage, but few data are available on the effects of HOSCN on mammalian cells. In this study, we have compared the actions of HOCl and HOSCN on human coronary artery endothelial cells (HCAEC). HOCl reacts rapidly with the cells, resulting in extensive cell death by both apoptosis and necrosis, with necrosis dominating at higher oxidant doses. In contrast, HOSCN is consumed more slowly, with cell death occurring only by apoptosis. Exposure of HCAEC to HOCl and HOSCN induces changes in mitochondrial membrane permeability, which, in the case of HOSCN, is associated with mitochondrial release of proapoptotic factors, including cytochrome c, apoptosis-inducing factor, and endonuclease G. With each oxidant, apoptosis appears to be caspase-independent, with the inactivation of caspases 3/7 observed, and pretreatment of the cells with the caspase inhibitor Z-VAD-fmk having no effect on the extent of cell death. Loss of cellular thiols, depletion of glutathione, and the inactivation of thiol-dependent enzymes, including glyceraldehyde-3-phosphate dehydrogenase, were seen with both oxidants, though to a much greater extent with HOCl. The ability of myeloperoxidase-derived oxidants to induce endothelial cell apoptosis may contribute to the formation of unstable lesions in atherosclerosis. The results with HOSCN may be particularly significant for smokers, who have elevated plasma levels of SCN(-), the precursor of this oxidant.
在免疫反应中，活化的白细胞通过释放髓过氧化物酶并形成H2O2来生成次卤酸。尽管这些氧化剂具有重要的杀菌特性，但它们也与包括动脉粥样硬化在内的炎症性疾病中的组织损伤有关。次氯酸（HOCl）和次硫氰酸（HOSCN）是髓过氧化物酶在生理条件下形成的主要氧化剂，这些氧化剂的比例取决于饮食和吸烟状况。HOCl具有高反应性，会导致明显的细胞损伤，但关于HOSCN对哺乳动物细胞影响的数据很少。在本研究中，我们比较了HOCl和HOSCN对人冠状动脉内皮细胞（HCAEC）的作用。HOCl与细胞迅速反应，通过凋亡和坏死导致广泛的细胞死亡，在较高氧化剂剂量下坏死占主导。相比之下，HOSCN的消耗较慢，仅通过凋亡导致细胞死亡。HCAEC暴露于HOCl和HOSCN会诱导线粒体膜通透性改变，就HOSCN而言，这与促凋亡因子（包括细胞色素c、凋亡诱导因子和核酸内切酶G）的线粒体释放有关。对于每种氧化剂，凋亡似乎不依赖于半胱天冬酶，观察到半胱天冬酶3/7失活，并且用半胱天冬酶抑制剂Z-VAD-fmk预处理细胞对细胞死亡程度没有影响。两种氧化剂都导致细胞内硫醇丧失、谷胱甘肽耗竭以及硫醇依赖性酶（包括甘油醛-3-磷酸脱氢酶）失活，不过HOCl的影响程度要大得多。髓过氧化物酶衍生的氧化剂诱导内皮细胞凋亡的能力可能有助于动脉粥样硬化中不稳定病变的形成。HOSCN的结果对于吸烟者可能特别重要，因为他们血浆中该氧化剂的前体SCN(-)水平升高。
