果膠對酯多醣體誘發巨噬細胞發炎反應之影響

Effects of pectin in lipopolysaccharide-induced inflammatory responses in mouse RAW264.7 Macrophages

王盈清(Ying-Ching Wang)

指導教授 ： 陳增福 陳建和

臺北醫學大學/醫學院/藥理學研究所/碩士(2005年)

摘要

飲食中某些成分在臨床上對於抗發炎和抗癌扮演了重要角色。果膠主要是由半乳糖醛酸所構成的多醣體且其存在於柑橘類水果中。果膠及結構上經過修飾作用的果膠被發現具有抗突變作用、預防癌細胞增殖及轉移等特性。前列腺素和一氧化氮的產生對於發炎反應和癌症的形成扮演重要的角色，因此在此篇研究論文中我們去探討不同酯化程度的果膠對於酯多醣體誘發巨噬細胞產生誘生型一氧化氮合成?(iNOS)和環氧酵素-2 (COX-2)活性的影響。西方點墨法及反轉錄-聚合?連鎖反應顯示酯化程度百分之二十五、六十五和九十四的果膠皆抑制酯多醣體所誘發的誘生型一氧化氮合成?和環氧酵素-2蛋白質和mRNA活性。然而在我們所測試的三種果膠中，酯化程度百分之九十四的果膠抑制效果最顯著且隨著濃度增加其抑制效果愈顯著。為了確認其中的抑制機轉，EMSA之結果顯示酯化程度百分之九十四的果膠在30?M時可以抑制酯多醣體誘發之NF?B和AP-1的活性；Transient transfection結果顯示酯化程度百分之九十四的果膠可以抑制酯多醣體誘發之NF?B的轉錄活性。另外進一步的結果顯示酯化程度百分之九十四的果膠藉由抑制I?B?的磷酸化及降解而抑制NF?B的活性；酯化程度百分之九十四的果膠同時也會抑制酯多醣體誘發之MAPK和STAT1的活性。此篇研究報告顯示果膠調節iNOS和COX-2 的特性也許對於預防發炎反應及癌症的形成扮演重要角色。

關鍵字

巨噬細胞 ； 酯化程度 ； 前列腺素 ； 一氧化氮 ； 蛋白質

並列摘要

The role of dietary components in cancer chemoprevention and inflammation is an emerging field of clinical importance. Pectin is complex polysaccharides rich in galactoside residues and it is most abundant in citrus fruits. Pectin and modified pectin have been found to exhibit anti-mutagenic activity and prevent spontaneous cancer metastasis and inhibit cancer cell proliferation. Prostaglandins biosynthesis and nitric oxide production have been implicated in the process of carcinogenesis and inflammation. In this study, we investigated the effect of pectin with different degrees of esterification (DE) on the activities of inducible nitric oxidant synthase (iNOS) and cyclooxygenase-2 (COX2) in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Western and RT-PCR analyses demonstrated that DE25, DE65 and DE94 pectin significantly blocked the protein and mRNA expression of iNOS and COX-2 in LPS-activated macrophages. Among three types of tested pectin, DE 94 pectin was the most potent inhibitor on the iNOS and COX2 expression by a concentration-dependant manner. To clarify the mechanism involved, electrophoretic mobility shift assay (EMSA) experiments indicated that DE94 pectin blocked the LPS-induced activation of nuclear factor-?B (NF-?B) and activator protein-1 (AP-1) at 30 ?M. Transient transfection experiments also showed that pectin inhited NF-?B-dependent transcriptional activity. DE94 pectin inhibited NF-?B activition through the prevention of inhibitor ?B (I?B) degradation and phosphorylation. Moreover, DE94 pectin also inhibited the LPS-induced phosphorylation of mitogen-activated protein kinase (MAPK) and STAT-1. This study suggests that modulation of iNOS and COX2 expression by pectin may be important in the prevention of carcinogenesis and inflammation.

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