Department of Health and Nutrition Biotechnology, Asia University, Taichung 413, Taiwan.
J Nutr Biochem. 2013 Jan;24(1):204-12. doi: 10.1016/j.jnutbio.2012.05.003. Epub 2012 Aug 15.
We examined the underlying mechanisms involved in n-3 docosahexaenoic acid (DHA) inhibition of inflammation in EA.hy926 cells. The present results demonstrated that pretreatment with DHA (50 and 100 μM) inhibited tumor necrosis factor-alpha (TNF-α)-induced intercellular adhesion molecule 1 (ICAM-1) protein, mRNA expression and promoter activity. In addition, TNF-α-stimulated inhibitory kappa B (IκB) kinase (IKK) phosphorylation, IκB phosphorylation and degradation, p65 nuclear translocation, and nuclear factor-κB (NF-κB) and DNA binding activity were attenuated by pretreatment with DHA. DHA triggered early-stage and transient reactive oxygen species (ROS) generation and significantly increased the protein expression of heme oxygenase 1 (HO-1), induced nuclear factor erythroid 2-related factor 2 (Nrf2) translocation to the nucleus and up-regulated antioxidant response element (ARE)-luciferase reporter activity. Moreover, DHA inhibited Nrf2 ubiquitination and proteasome activity. DHA activated Akt, p38 and ERK1/2 phosphorylation, and specific inhibitors of respective pathways attenuated DHA-induced Nrf2 nuclear translocation and HO-1 expression. Transfection with HO-1 siRNA knocked down HO-1 expression and partially reversed the DHA-mediated inhibition of TNF-α-induced p65 nuclear translocation and ICAM-1 expression. Importantly, we show for the first time that HO-1 plays a down-regulatory role in NF-κB nuclear translocation, and inhibition of Nrf2 ubiquitination and proteasome activity are involved in increased cellular Nrf2 level by DHA. In this study, we show that HO-1 plays a down-regulatory role in NF-κB nuclear translocation and that the protective effect of DHA against inflammation is partially via up-regulation of Nrf2-mediated HO-1 expression and inhibition of IKK/NF-κB signaling pathway.
我们研究了 n-3 二十二碳六烯酸（DHA）抑制 EA.hy926 细胞炎症的潜在机制。本研究结果表明，DHA（50 和 100 μM）预处理可抑制肿瘤坏死因子-α（TNF-α）诱导的细胞间黏附分子 1（ICAM-1）蛋白、mRNA 表达和启动子活性。此外，DHA 预处理可减弱 TNF-α 刺激的抑制性 κB 激酶（IKK）磷酸化、IKK 磷酸化和降解、p65 核易位以及核因子-κB（NF-κB）和 DNA 结合活性。DHA 触发早期和短暂的活性氧（ROS）生成，并显著增加血红素加氧酶 1（HO-1）的蛋白表达，诱导核因子红细胞 2 相关因子 2（Nrf2）向核内易位并上调抗氧化反应元件（ARE）-荧光素酶报告活性。此外，DHA 抑制 Nrf2 泛素化和蛋白酶体活性。DHA 激活 Akt、p38 和 ERK1/2 磷酸化，相应途径的特异性抑制剂可减弱 DHA 诱导的 Nrf2 核易位和 HO-1 表达。HO-1 siRNA 转染敲低 HO-1 表达，并部分逆转 DHA 介导的 TNF-α诱导的 p65 核易位和 ICAM-1 表达的抑制作用。重要的是，我们首次表明 HO-1 在 NF-κB 核易位中起负调控作用，并且 DHA 抑制 Nrf2 泛素化和蛋白酶体活性参与增加细胞内 Nrf2 水平。在本研究中，我们表明 HO-1 在 NF-κB 核易位中起负调控作用，DHA 对炎症的保护作用部分是通过上调 Nrf2 介导的 HO-1 表达和抑制 IKK/NF-κB 信号通路实现的。
