甲基半胱胺酸抑制酯多醣所誘發之細胞發炎反應及其機轉

Se-methylselenocysteine suppresses lipopolysaccharide-induced iNOS expression and NO production in RAW 264.7 macrophages

江艾芝(Ai-Zhi Jhang)

指導教授 ： 陳威仁

中山醫學大學/醫學科技學院/生物醫學科學學系碩士班/碩士(2010年)

https://doi.org/10.6834/CSMU.2010.00001

摘要

在癌症預防的領域裡，發炎的抑制也是一門很重要的課題，因當體內產生慢性發炎時，持續惡化後則會造成許多更嚴重之疾病，例如：關節病變、神經退化、阿茲海默、糖尿病、心血管疾病及癌症等。近年來因有研究證實人體所需之微量元素硒對於抗癌及抗氧化具有良好之功效，但對於抗發炎之機轉則尚未明瞭。故本篇利用已證實具有抗氧化及抗癌特性的硒元素胺基酸化合物，探討其抗發炎之機轉。我們以四種硒類胺基酸化合物，分別為Se-methylselenocysteine (MSC)、Glutamyl-Se-methylSelenoCysteine (GMSC)、 L-Selenomethionine (SeM)、Glutamyl- L-Selenomethionine (GSeM) 作為比較。本實驗以RAW264.7細胞株作為模式，以LPS引發RAW264.7細胞株之發炎反應，再比較四種硒類胺基酸化合物對於LPS所誘發的發炎反應之影響。四種硒類胺基酸化合物對細胞皆屬於低毒性，由結果發現MSC為四種硒類胺基酸中對LPS所引發的NO生成量最具有抑制效果且MSC對細胞為低毒性，顯示MSC抑制LPS所誘導的NO生成可能是透過影響訊息傳遞路徑以達成。研究亦發現是MSC抑制iNOS蛋白及mRNA的表現。結果如推測，MSC抑制LPS所活化的IKK的活性導致IκB磷酸化的減少，降低IκB降解的機會，進而使轉錄因子NF-κB則無法進入細胞核裡驅動iNOS基因表現。此外，實驗也發現MSC會抑制LPS所誘導的p38 MAPK及JNK的活性，顯示MSC也可透過抑制MAPK訊息傳遞路徑中的p38及JNK使LPS所誘發的NF-κB活化受到抑制，進而影響iNOS表現，降低LPS所誘導的NO生成與發炎反應。

關鍵字

甲基半胱胺酸

並列摘要

Nitric Oxide (NO), a free radical generated by the expression and activity of inducible NO synthase ( iNOS ), acts an essential mediator in inflammation response, which is closely linked to several human diseases including cancer. Therefore, prevention of iNOS expression may be an important mechanism of anti-inflammation and antitumor. Recent studies establish a critical role of selenium in cancer prevention in vitro and in vivo but the effect of selenium on anti-inflammation still remains unclear yet. Here we used murine macrophage RAW 264.7 cells as a cell-line model to evaluate the anti-inflammatory capacity of selenium-related compounds including several seleno-amino acid compounds. Firstly, we determined and compared the cytotoxicity of four kinds of seleno-amino acid compounds by MTT assay and LDH cytotoxicity assay and show low toxicity of these compounds to lipopolysaccharide (LPS)-induced RAW 264.7 cells. Next, we evaluated the anti-inflammatory activity of seleno-amino acid compounds. Our preliminary data shows that Se-methylselenocysteine (MSC) has the strongest activity of anti-inflammation compared to other seleno-amino acid compounds. MSC reduced the mRNA and protein levels of iNOS induced by LPS, paralleled with the decrease in LPS-induced NO production in RAW 264.7 macrophages. However, MSC does not inhibit LPS-induced COX-2 expression at the same condition. MSC treatment also reduced the translocation of p65 subunit, but not in p50 subunit of nuclear factor-κB (NF-κB) from cytosol to nucleus by prevention of the phosphorylation and consequent degradation of inhibitor of nuclear factor-κB (IκB) via inhibition of phosphorylation of IKKα/β. In this study, we also demonstrate that MSC can reduce the activation and phosphorylation of p38 and JNK induced by LPS, which modulate iNOS protein expression. Taken together, our current data demonstrate that MSC might contribute to the potent anti-inflammatory effect in LPS-elicited RAW264.7 cells via down-regulation of iNOS expression, but the detailed mechanisms require further study.

並列關鍵字

Se-methylselenocysteine

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