槲皮酮及其代謝產物對人類肝癌細胞株Hep 3B生長之抑制機轉及槲皮酮對正常大鼠初代肝細胞麩胱甘肽相關之解毒代謝與抗氧化系統之影響

Abstract

本研究以槲皮酮（quercetin）及其代謝產物槲皮酮葡萄糖醛酸（quercetin glucuronides）及槲皮酮硫酸鹽（quercetin sulfates）為實驗樣品，探討其對於人類肝癌細胞株Hep 3B的抑制機轉，並以正常大鼠之初代肝細胞進行試驗，評估槲皮酮對正常大鼠初代肝細胞麩胱甘肽相關之解毒代謝與抗氧化系統的影響及對四氯化碳誘導肝損傷的保護效果。結果以槲皮酮處理Hep 3B細胞48小時，由細胞生存力發現其IC50為335 μM，含有兩種代謝產物槲皮酮葡萄糖醛酸及槲皮酮硫酸鹽但比例不同的sample 1與sample 2效果更佳，分別為12 μM及67 μM。藉由流式細胞儀分析細胞週期，結果顯示槲皮酮會誘導細胞走向凋亡，且在細胞凋亡分析中亦發現槲皮酮可誘導caspase-3的活性；代謝產物槲皮酮葡萄糖醛酸及槲皮酮硫酸鹽則是使細胞滯留於G2/M期。進一步以西方墨點法偵測槲皮酮對細胞凋亡蛋白的影響，發現隨著槲皮酮濃度增加，活化型caspase-3、PARP與caspase-9的表現呈上升趨勢，促進細胞凋亡的蛋白Bax與Bad亦增加，抑制細胞凋亡的蛋白Bcl-2則下降。初代肝細胞麩胱甘肽相關之解毒代謝與抗氧化系統方面，以0-120 μM之槲皮酮處理正常大鼠初代肝細胞24小時，並不會造成脂質過氧化，而與對照組相較，在80 μM的槲皮酮濃度下不影響細胞生存力且可顯著提升麩胱甘肽（glutathione, GSH）的含量約50 %，並使麩胱甘肽過氧化酶（glutathione peroxidase, GPx）的活性上升47 %、麩胱甘肽還原酶（glutathione reductase, GRd）的活性上升41 %、與麩胱甘肽硫轉移酶（glutathione S-transferase, GST）的活性上升15 %（P＜0.05），因此有助於肝臟的解毒代謝與抗氧化作用。在以10 mM四氯化碳誘導初代肝細胞損傷的模式中，也發現40 μM槲皮酮即具有保護細胞的作用。綜合上述結果，槲皮酮可抑制肝癌細胞生長，並有促進肝臟生理功能及護肝效果，作為抗癌保健的藥物，極具發展潛力。

In this study, quercetin and quercetin metabolites, quercetin glucuronides and quercetin sulfates, were used to investigate the anti-proliferation effects and mechanism on human hepatoma cells Hep 3B and the effect on glutathione-related detoxification and antioxidation system of primary rat hepatocytes. We found that after 48 hr treatment, quercetin inhibited the growth of Hep 3B cells and the IC50 value was 335 μM. With much lower IC50 values, two samples containing different amount of quercetin glucuronides and quercetin sulfates showed stronger anti-proliferative effect than quercetin. The IC50 value of sample 1 was 12 μM and sample 2 was 67 μM. Through cell cycle and Western blot analysis, we found that quercetin metabolites arrested Hep 3B cells in G2/M phase while quercetin induced apoptosis of Hep 3B cells by increasing the levels of pro-apoptotic proteins Bax and Bad, decreasing the levels of anti-apoptotic protein Bcl-2, and inducing the cleavages of caspase-3, caspase-9 and PARP. The results of quercetin on glutathione-related detoxification and antioxidation system of primary rat hepatocytes showd that 80 μM quercetin significantly elevated the level of glutathione up to 150 % and increased the activities of glutathione peroxidase to 147 %, glutathione reductase to 141 % and glutathione S-transferase to 115 % as compared with control group (P＜0.05) without causing lipid peroxidation. Quercetin also protected primary rat hepatocytes from 10 mM carbon tetrachloride-induced cytotoxity. The results suggest that quercetin could inhibit the gowth of hepatoma cells, promote the antioxidant defense system and metabolic activity of hepatocytes, and might be a promising agent for the treatment and prevention of human hepatoma.