The interaction of inhibitory effects between curcumin and water-soluble antioxidants on the proliferation of a hepatoma cell line, Hep3B cells

Abstract

薑黃(學名為Curcuma longa )是一種根莖植物，其莖部幾世紀以來即被用來當作消炎藥。薑黃素(Curcumin；化學名︰Diferuloylmethane)則是從薑黃中提取的天然黃色色素，屬於多酚類化合物(polyphenol compound)，同時也是鬱金(Curcumin aromatica )及咖哩(curry)之主要活性成份。過去許多研究指出，Curcumin具有抗氧化、抗發炎與預防癌症功效。另一方面，Curcumin也被發現具有直接抑制血癌細胞(human leukemia cells, HL-60)增殖的作用，而Vitamin C (Vit-C)、glutathione（GSH）及N-Acetyl-cysteine (NAC)等水溶性抗氧化劑則可以加強Curcumin抑制血癌細胞增殖的作用，然而Curcumin是否含會抑制固體癌細胞的增殖，以及水溶性抗氧化劑是否可以加強Curcumin的作用則尚未見報導。 本研究的目的乃探討Curcumin抑制Hep3B肝癌細胞增殖的作用及其作用機轉，並探討水溶性抗氧化劑(Vit-C及NAC)是否影響薑黃素之抗癌作用。我們將成長狀況穩定的人類肝癌細胞株(Hep3B)以1X103 /ml細胞的密度放置於96 well microplate 中，而後加入不同濃度的Curcumin或以Curcumin合併不同濃度的Superoxide dismutase (SOD)、 Catalase、 Buthionine sulfoximine (BSO)、Vit-C或NAC，放置於37℃培養箱內培養72小時。最後以MTT assay計算細胞存活率。 結果發現，Curcumin單獨在10 μM以上具有顯著抑制Hep3B肝癌細胞增殖的作用。高濃度Vit-C (≧0.6 mM)濃度時會顯著加強Curcumin的抗癌作用。相反的，NAC在高濃度(2-6 mM)則會顯著抑制Curcumin的抗癌作用。SOD及Catalase對Curcumin的抗癌作用則無顯著一致性影響，但BSO則可以顯著加強Curcumin的抗癌作用。以上結果顯示，Curcumin在高濃度時對Hep3B肝癌細胞的增殖具有一定的抑制作用，高濃度Vit-C會加強Curcumin抑制肝癌細胞增殖的作用，相反的，高濃度NAC則會降低Curcumin抑制肝癌細胞增殖的作用，此兩者之差異的機轉有待進一步探討。

Turmeric (Scientific name: Curcuma longa) is a kind of rhizome plant. Its stem has been used as an anti-inflammatory drug for several centuries. Curcumin (Chemical name: Diferuloylmethane), a kind of polyphenol compound, is a natural yellow pigment extracted from Tumeric. It also is the main active component of Curcumin aromatica and Curry. Many studies pointed out that, curcumin has the activities of anti-oxidation, anti-inflammation, and cancer prevention. On the other hand, curcumin has also been found to have inhibitory activity on the proliferation of leukemia cells (human leukemia cells, HL-60) directly. Besides, the water-soluble antioxidants, such as vitamin C (Vit-C), glutathione (GSH) and N-Acetyl-cysteine (NAC), can enhance the anti-cancer effect of curcumin on leukemia cells. So far, it is not known whether the above water-soluble antioxidants can strengthen the anti-cancer activity of curcumin in solid cancer cells. The purposes of this study were to evaluate the effect of curcumin to suppress the proliferation of Hep3B hepatoma cells and to clarify whether the water-soluble antioxidants such as Vit-C and NAC can affect the anti-cancer effect of Curcumin. We cultured human hepatoma cells (Hep3B) in incubator with 5% CO2 at 37℃until stable. We placed the cells into 96 wells of micro-plate by a density of 1x103 cells/ml per well. Each well was added various concentrations of curcumin (0-100μM) combined with or without various concentrations of superoxide dismutase (SOD), catalase, Buthionine sulfoximine (BSO), Vit-C or NAC. After incubation for 72 hours, we measured the survival rate of cancer cells by MTT assay . The results show that curcumin at 10 μM or higher concentration significantly suppressed the proliferation of Hep3B cells. Vit-C at 0.6 mM or higher concentration significantly enhanced the anti-cancer activity of curcumin. In contrast, NAC at concentration from 2 to 6 mM significantly attenuated the anti-cancer activity of curcumin. Antioxidant enzymes SOD and catalase, even added at 100 IU/ml, had no significant influence on the anti-cancer activity of curcumin. However, BSO, an inhibitor of GSH synthesis, significantly enhanced the anti-cancer activity of curcumin. The above results suggest that, curcumin itself at high concentration has an inhibitory activity on the proliferation of Hep3B cancer cells. The mechanism may be related to the depletion of GSH in cancer cells. There are differential effects of Vit-C and NAC on the anti-cancer activity of curcumin and their mechanisms of action remain to be elucidated.