許多研究顯示，發炎反應和血管內皮細胞功能異常是動脈粥樣硬化的重要起始關鍵。細胞間黏附分子1 (ICAM-1)是一種發炎生理指標，與單核球黏附至內皮細胞上的作用有關。文獻指出，飲食中攝取富含n-3多元不飽和脂肪酸的魚油，例如二十二碳六烯酸 (DHA)，可以有效地減少罹患心血管疾病的風險。因此本實驗將以腫瘤壞死因子-α (TNF-α)誘發內皮細胞株EA.hy926產生發炎反應，來探討DHA對於TNF-α所誘發ICAM-1表現之影響以及可能參與的機制。結果發現，DHA (50, 100 μM)除了會抑制TNF-α所誘發的ICAM-1蛋白質、mRNA表現、報導基因活性；亦能進一步地降低IKK磷酸化、IκB磷酸化和降解、p65核轉移，以及NF-κB與DNA的結合能力。另一方面，處理DHA會顯著增加血基質氧化酵素1 (HO-1)和轉錄因子Nrf2的蛋白質表現，並誘導Nrf2轉移進入細胞核內，向上調節antioxidant response element (ARE)報導基因活性。同時，我們也發現DHA調節HO-1的表現主要是在轉錄階段。另外，利用siRNA干擾技術抑制HO-1的表現，會部分逆轉DHA對於ICAM-1的抑制作用。綜合以上結果得知，在EA.hy926細胞中，DHA會藉由抑制NF-κB訊息傳遞路徑及增加Nrf2-dependent HO-1之表現來降低TNF-α所誘發的ICAM-1表現；本研究證實DHA具有預防心血管等發炎性疾病之潛力。
Several studies indicate that inflammation and endothelial cell dysfunction are important initiating events in atherosclerosis. Intercellular adhesion molecule 1 (ICAM-1), an inflammatory biomarker, plays a pivotal role in cardiovascular disease (CVD) progression. Dietary intake of fish oil rich in n-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA), has been associated with reduced CVD risk. In this study, we investigated the effect of DHA on the tumor necrosis factor-alpha (TNF-α)-induced ICAM-1 expression in EA.hy926 cells and the possible mechanisms involved. The results showed that DHA (50 and 100 μM) inhibited TNF-α-induced ICAM-1 protein, mRNA expression, and promoter activity. In addition, TNF-α-stimulated IKK phosphorylation, IκB phosphorylation and degradation, p65 nuclear translocation, and NF-κB and DNA binding activity were attenuated by pretreatment with DHA. Furthermore, DHA significantly increased the protein expression of heme oxygenase 1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2), induced Nrf2 translocation to the nucleus, and up-regulated antioxidant response element (ARE)-luciferase reporter activity. HO-1 expression is primarily regulated by DHA at the transcriptional level. Transfection with HO-1 siRNA knocked down HO-1 expression and partially reversed the DHA-mediated inhibition of ICAM-1 expression. In conclusion, these results suggested that DHA inhibits TNF-α-induced ICAM-1 expression is through attenuation of NF-κB signaling pathway and stimulation of Nrf2-dependent HO-1 expression in EA.hy926 cells. The anti-inflammatory effects of DHA may implicate its CVD-protective potential.
