Sathishkumar K, Murthy Subramanyam N, Uppu Rao M
Department of Environmental Toxicology, The Health Research Center, Southern University and A&M College, Baton Rouge, LA 70813, USA.
Free Radic Res. 2007 Jan;41(1):82-8. doi: 10.1080/10715760600950566.
Ozone present in the photochemical smog or generated at the inflammatory sites is known to oxidize cholesterol and its 3-acyl esters. The oxidation results in the formation of multiple "ozone-specific" oxysterols, some of which are known to cause abnormalities in the metabolism of cholesterol and exert cytotoxicity. The ozone-specific oxysterols have been shown to favor the formation of atherosclerotic plaques and amyloid fibrils involving pro-oxidant processes. In the present communication, cultured murine GT1-7 hypothalamic neurons were studied in the context of cholesterol metabolism, formation of reactive oxygen species, intracellular Ca2 + levels and cytotoxicity using two most commonly occurring cholesterol ozonolysis products, 3beta- hydroxy-5-oxo-5,6-secocholestan-6-al (ChSeco) and 5beta, 6beta-epoxy-cholesterol (ChEpo). It was found that ChSeco elicited cytotoxicity at lower concentration (IC50 = 21 +/- 2.4 microM) than did ChEpo (IC50 = 43 +/- 3.7 microM). When tested at their IC50 concentrations in GT1-7 cells, both ChSeco and ChEpo resulted in the generation of ROS, the magnitude of which was comparable. N-acetyl-l-cysteine and Trolox attenuated the cytotoxic effects of ChSeco and ChEpo. The intracellular Ca2 + levels were not altered by either ChSeco or ChEpo. Methyl-beta-cyclodextrins, which cause depletion of cellular cholesterol, prevented ChSeco- but not ChEpo-induced cytotoxicity. The cell death caused by ChEpo, but not ChSeco, was prevented by exogenous cholesterol. Although oxidative stress plays a significant role, the results of the present study indicate differences in the pathways of cell death induced by ChSeco and ChEpo in murine GT1-7 hypothalamic neurons.
已知光化学烟雾中存在的臭氧或在炎症部位产生的臭氧会氧化胆固醇及其3 - 酰基酯。这种氧化会导致多种“臭氧特异性”氧化甾醇的形成，其中一些已知会导致胆固醇代谢异常并发挥细胞毒性。臭氧特异性氧化甾醇已被证明有利于涉及促氧化过程的动脉粥样硬化斑块和淀粉样原纤维的形成。在本通讯中，使用两种最常见的胆固醇臭氧分解产物3β - 羟基 - 5 - 氧代 - 5,6 - 开环胆甾烷 - 6 - 醛（ChSeco）和5β,6β - 环氧胆固醇（ChEpo），在胆固醇代谢、活性氧形成、细胞内Ca2 +水平和细胞毒性的背景下研究了培养的小鼠GT1 - 7下丘脑神经元。结果发现，ChSeco在比ChEpo更低的浓度（IC50 = 21±2.4 microM）下引发细胞毒性（ChEpo的IC50 = 43±3.7 microM）。当在GT1 - 7细胞中以其IC50浓度进行测试时，ChSeco和ChEpo都导致了ROS的产生，其幅度相当。N - 乙酰 - l - 半胱氨酸和生育三烯酚减弱了ChSeco和ChEpo的细胞毒性作用。ChSeco和ChEpo均未改变细胞内Ca2 +水平。引起细胞胆固醇耗竭的甲基 - β - 环糊精可预防ChSeco诱导的细胞毒性，但不能预防ChEpo诱导的细胞毒性。外源性胆固醇可预防ChEpo而非ChSeco引起的细胞死亡。尽管氧化应激起重要作用，但本研究结果表明ChSeco和ChEpo在小鼠GT1 - 7下丘脑神经元中诱导细胞死亡的途径存在差异。
