共軛亞麻油酸在脂多醣體誘發RAW264.7巨噬細胞發炎反應相關事件之影響

共軛亞麻油酸（Conjugate linoleic acid, CLA）是一群18個碳，兩個共軛雙鍵的多元不飽和脂肪酸（Octadecadienoic acid）的同質異構物，目前已知CLA同質異構物中，其共軛雙鍵位置可在△7, 9, △9, 11, △11, 13, △8, 10和△10, 12上，以順式（cis）或反式（trans）方式排列。飲食中牛羊等反芻類動物肉類（2.7-5.6 mg CLA/g fat）及乳製品（2.9-7.1mg CLA/g fat）含較高CLA，為CLA主要來源（review in Chin et al., 1992）。動物實驗發現，CLA除具有抗癌功效外，它亦可影響身體組成，比如減少脂肪組織（antiadipogenic），增加肌肉組織；減少動脈脂肪層破損（aortic fatty streak lesion）而調節粥狀硬化形成；調控血糖衡定及影響免疫力功能等。雖然探討CLA對疾病預防及治療的文獻很多，但至今對探討CLA與發炎反應的相關文獻卻不多。由於發炎反應與許多疾病發生及病程有關，故本實驗模擬生理感染及發炎反應之實驗模式，評估CLA對RAW264.7小鼠巨噬細胞經細菌內毒素lipopolysaccharides（LPS）刺激所誘發產生及發炎反應的相關事件之影響，並探討相關可能的調控機轉。結果顯示，20-200μM CLA及0.1-1μg/ml LPS處理下，均不影響RAW264.7巨噬細胞存活率。而CLA處理呈劑量關係的有效抑制LPS誘發inducible nitric oxide synthase（iNOS）和cyclooxygenase-2（COX-2）蛋白質及mRNA的表現，也抑制nitric oxide（NO）和 prostglandin E2（PGE2）的生成，尤以200μM CLA之抑制效果最顯著（p<0.05）。結果也顯示200μM CLA可顯著減緩LPS誘發IκBα磷酸化並抑制NF-κB與DNA結合。綜合以上結果可知LPS活化RAW264.7小鼠巨噬細胞所誘發之iNOS、COX-2蛋白質和mRNA及其催化生成之事件可被CLA有效抑制，且此抑制作用可能與CLA降低LPS誘發NF-κB活化，進而影響NF-κB 之轉錄活性有關。 關鍵詞：共軛亞麻油酸、RAW264.7巨噬細胞、脂多醣體、一氧化氮、發炎反應

Conjugated linoleic acid（CLA）refers to a group of positional and geometric isomers of octadecadienoic acid with conjugated dienoic double bond in △7, 9, △9, 11, △11, 13, △8, 10 and △10, 12 positions, in either cis and/or trans configurations. Dietary CLA is primarily found in dairy products and beef fat. CLA has been shown to play an important role in chemopreventation, immune function as well as blood sugar and lipid homeostasis. However, the role of CLA on the inflammatory reaction is still not clear so far. In order to explore the anti-inflammatory ability of CLA, exogenous CLA（0, 20, 100 or 200μM）was added with 0.1 or 1μg/ml medium bacteria endotoxin lipopolysaccharides（LPS）in mouse RAW264.7 macrophage cell. The 3-（4,5-dimetyl-thiazo-2-yl）-2,5-diphenyl-tetrazoleum assay showed that exogenous CLA addition did not influence cell viability. CLA, however dose-dependently diminished LPS-induced inducible nitric oxide synthase（iNOS）and cyclooxygenase-2（COX-2） expression and subsequent nitric oxide（NO）and prostaglandin E2（PGE2）synthesis.respectively. Furthermore, 200μM CLA significantly decreased LPS-induced IκB-αphosphorylation, p65 translocation to nucleus and NF-κB nuclear protein —DNA binding activity. In conclusion, CLA significantly inhibits LPS- induced inflammatory events in RAW264.7 macrophages, and this inhibitory activity of CLA may be through its modulating NF-κB transcriptional activity. Key words : conjugated linoleic acid, RAW264.7 macrophages, Lipopolysaccharide, inflammation, NO, NF-κB.