維生素E和GSH保護細胞形態之探討

細胞進行藥物代謝或正常代謝時常可伴隨活性氧分子 (reactive oxygen species) 的產生。這些活性氧分子如無法有效清除，將形成氧化緊迫 (oxdative stress)，造成細胞傷害，進而壞死。在細胞受到傷害時，常 可觀察到細胞表面形態發生變化，造成發泡現象 (blebbing)。細胞膜內 的重要抗氧化分子－維生素E，可以減緩氧化傷害的發生，除了保護細胞 膜中脂質免於氧化之外，維生素E也能有效保護細胞膜蛋白質；除了維生 素E外，生物體內其他的抗氧化分子，例如 GSH，已知也有維持細胞蛋白 質免於氧化傷害的功能。所以本實驗針對維生素E和GSH保護細胞形態進行 探討第一部分針對在氧化緊迫下，探討維生素E和GSH與脂質過氧化、細胞 膜蛋白質硫醇 (thiol) 流失、細胞架構蛋白及細胞發泡現象之間的關係 ；結果顯示，細胞形態受損似乎與脂質過氧化無直接關係，而和細胞膜蛋 白質硫醇的流失較有關係，並且維生素E的補充可以延緩發泡現象，但是 GSH對細胞的保護作用並不明顯。第二部份：主要針對胞內硫醇(包括非蛋 白質硫醇與蛋白質硫醇)，探討硫醇(thiol)流失與細胞發泡現象之間的關 係，這一部份實驗我們改用diamide (硫醇氧化劑)來處理肝細胞。結果發 現：維持蛋白質硫醇對於保護細胞免於受到氧化傷害遠比非蛋白質硫醇來 得重要。綜合以上兩個實驗結果，我們認為：(一) 氧化緊迫下，脂質過 氧化並非造成肝細胞發泡的必然因素，細胞膜蛋白的氧化可能扮演有重要 的角色；(二) 維生素E可有效延緩架構蛋白肌動蛋白及其他細胞膜蛋白質 硫醇的流失，並減少細胞形態發生改變。保護細胞形態上，維生素E較GSH 硫醇來得更重要。(三) 肌動蛋白與細胞形態的維持有密切相關。

Drug metabolism and normal metabolism in cellular microenvirement can lead to the production of reactive oxygen species. Once these reactive these reactive oxygen species cannot be eliminated, cells will be damaged and leads to membrane morphological changes, such as the bleb formation. Tocopherol, the important antioxidant molecule of cell membrane, can protect membrane lipids and proteins from oxidative damage. Besides, other intracellular antioxidants, such as glutathione (GSH), is also known to have similar functions as tocopherol. Therefore, in this study, we compare the protective effects of tocopherol and GSH on the cell morphology in rat hepatocytes under oxidative stress. In the first section of this study, by treating cells with tert-butyl hydroperoxides, we examined the effects of tocopherol and GSH on lipid peroxidation, membrane protein thiol depletion, cytoskeleton, and cell blebbing. Results indicated that cell morphological change was not directly related to lipid peroxidation, but was corresponded to membrane protein thiol status. Tocopherol suppresses blebbing formation, however, the effect of glutathione is not significant. In the second part, we further examined the role of intracellular thiol status (including non-protein and protein thiols) on cell blebbing. In this study, hepatocytes were pretreated with L-buthionine sulfoximine following by a thiol oxidizing agent, diamide. Result indicated that protein thiols play a more important role on protecting cell from morphological change than GSH. In conclusions: 1). Lipid peroxidation is not an essential of blebbing formation in hepatocytes, otherwise, membrane protein oxidation may play a more important role. 2). Tocopherol effectively inhibits the polymerization of actin, the depletion of membrane protein thiol, and the morphological changes. However, the protection of GSH on these parameters is less significant than tocopherol is. 3). The oxidation of actin thiols is related to the change of cell morphology.