| 摘要: | 血管新生(Angiogenesis)是一種生理過程，包括: 生長、發育、傷口修復、腫瘤生長與轉移。血管內皮生長因子(VEGF)是內皮細胞特定的細胞分裂素和趨化劑，並對於內皮細胞存活、增殖與遷移上扮演重要因子。二十二碳六烯酸(DHA)是一種n-3多元不飽和脂肪酸，在體內與體外試驗中已被證實有抗癌作用。因此本篇研究，DHA是透過何種分子機制而達到抑制血管新生之作用。我們使用人類臍帶靜脈內皮細胞(HUVECs)當作實驗模式，並做細胞存活率、西方墨點法、傷口修復、磷酸酶活性與一氧化氮濃度測定等試驗，探討DHA的抗癌作用。實驗結果顯示，DHA、PD98059 (ERK抑制劑)、 GW9508 (GPR120促進劑)可抑制VEGF所誘發細胞的遷移作用。然而預處理PP2A抑制劑 (okadaic acid ,OA)和NO donor (S-Nitroso-N-acetyl-DL-penicillamine , SNAP)，可反轉DHA抑制細胞遷移作用。在訊息途徑上，VEGF是藉由增加ERK、eNOS磷酸化和增加一氧化氮的生成，因而誘發細胞的遷移作用。HUVECs在預處理DHA可增加PP2A酵素活性，並且可降低VEGF所誘發ERK、eNOS磷酸化。從上述結果意味著，DHA抑制VEGF所誘發細胞的遷移作用，是透過增加PP2A的酵素活性，和抑制VEGF所誘發ERK/eNOS/NO訊息路徑。綜合以上結論，DHA對於抗癌的功效是藉由抑制細胞遷移作用。
Angiogenesis is invovled in the physiological processes including growth, development, wound healing, tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen, which is essential for endothelial cell survival, proliferation, and migration. Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, shows anti-carcinogenic potential both in vitro and in vivo. In this study, we investigated the molecular mechanism by which DHA down-regulates angiogenesis. We used HUVECs and fertilized chicken eggs as study models, and used chick chorioallantoic membrane (CAM) assay, MTT assay, Western blotting,wound healing assay, phosphatase activity assay and NO assay, to explore the anti-carcinogenic effect of DHA. The results showed that DHA, PD98059 (ERK inhibitor) and GW9508 (GPR120 agonist) inhibited VEGF-induced cell migration. Nevertheless, pretreatment with okadaic acid (OA, PP2A inhibitor) and S-Nitroso-N-acetyl-DL-penicillamine (SNAP, NO donor) reversed the cell migration inhibitory effect of DHA. VEGF induced angiogenesis was accompanied by phosphorylation of ERK and eNOS, as well as an increase in NO production. Treatment of HUVECs with DHA increased PP2A enzyme activity and decreased VEGF-induced phosphorylation of ERK and eNOS. However, pretreatment with OA significantly decreased DHA-induced PP2A enzyme activity and reversed the DHA inhibition of VEGF-induced ERK and eNOS phosphorylation. These results suggest that DHA abolishes VEGF-induced cell migratin via inhibition of VEGF-induced ERK/eNOS/NO signaling pathway and stimulation of PP2A activity. Taken together, anti-caricnogenic effect of DHA is at least in part by virture of its attenuation of cell migration which is essential for angiogenesis. |
