- 學位論文
Gamma-次亞麻油酸與亞麻油酸對脂多醣體誘發小鼠RAW264.7巨噬細胞發炎反應之效應及相關機轉
The influence of gamma-linolenic acid and linoleic acid on LPS-induced inflammatory reactions in mouse RAW264.7 macrophage cells
摘要
Gamma-次亞麻油酸（18:3, gamma-linolenic acid, GLA）為n-6多元不飽和脂肪酸，在人體可經由 delta 6去飽和酵素 (delta 6 desaturase)代謝n-6多元不飽和脂肪酸-亞麻油酸（18:2, Linoleic acid, LA）生成GLA。研究發現有許多因素可導致 delta 6 desaturase活性降低，例如：老化、反式脂肪酸、氫化油、吸煙、及過度飲酒等。減少體內亞麻油酸代謝成GLA被視為與疾病發生有關，研究也證實補充GLA確有助於緩解老化、經前症候群、糖尿病、風濕性關節炎、癌症及心血管疾病發生。巨噬細胞可分泌促發炎物質，造成組織細胞發炎，是身體免疫系統中重要防禦系統之一。然而被活化巨噬細胞長期不斷分泌促發炎物質也與慢性發炎反應的發生具有密切相關性。本研究在探討GLA與LA對脂多醣（lipopolysaccharides, LPS）誘發小鼠RAW264.7巨噬細胞發炎反應之效應及相關機轉。單獨處理GLA及LA或LPS 1 μg/ml共同處理 18小時，皆不影響細胞存活率；LPS誘發小鼠RAW264.7細胞發炎反應模式下，GLA和LA顯著抑制LPS誘發inducible nitric oxide synthase（iNOS）、cyclooxygenase-2（COX-2）、pro-interleukin-1β (pro-IL-1β)的表現和一氧化氮（Nitric Oxide, NO）生成，其中，LA雖可減少LPS誘發iNOS mRNA表現，但卻不影響iNOS蛋白質表現。此外，氧化壓力的增加與慢性發炎反應有關，在抗氧化作用上，GLA可增加胞內在LPS刺激下GSH的含量，但LA則無此效果，且LA反而有增加LPS刺激下胞內GSH的減少，顯示GLA和LA在對抗氧化壓力作用中，是經由不同途徑達到抑制發炎反應的功效。GLA和LA均可抑制LPS誘發AP-1與NF-κB活化，在LPS活化NF-κB途徑中，GLA和LA可經由選擇性抑制MAPK訊息傳遞途徑和IκBα磷酸化，減少IκBα降解，抑制NF-κB轉移至核內，進而影響NF-κB之轉錄活性。由以上結果得知：GLA和LA可經由不同途徑達到抗發炎作用，且GLA較LA更具有抗發炎之功效。
並列摘要
Gamma linolenic ascid (18:3, GLA) is an omega-6 polyunsaturated fatty acid. Linoleic acid（18:2, LA）is metabolized by delta 6 desaturase to form GLA.A decreased capacity of converting LA to GLA has been linked with various physiologic/pathophysiologic states, including aging, diabetes, premenstrual syndrome, rheumatoid arthritis, cancer, and cardiovascular disease. Macrophages play a central role in the immune system and are capable of modulating several important biologic functions. Activated macrophages can synthesize a serious of proinflammatory products to induce tissue inflammation. We examined the influence of GLA and LA on lipopolysaccharide (LPS)-induced inflammatory reactions in mouse RAW264.7 macrophage cell line. MTT assay showed that addition of different concentrations GLA and 200 μM LA in the absence or presence of 1 μg/ml LPS treatment after 18 hours did not influence mouse RAW264.7 cell viability. GLA dose-dependent inhibited LPS-induced protein expressions of inducible nitric oxide synthase (iNOS), pro-interleukin-1β (pro-IL-1β) and cyclooxygenase-2 (COX-2) as well as nitric oxide (NO) production (p＜0.05). Addition of exogenous LA 200 μM inhibited LPS-induced pro-IL-1β,COX-2 protein and iNOS, COX-2 mRNA expression and NO production (p＜0.05), but not regulated LPS-induced iNOS protein expression. GLA at 50-200 μM concentrations increasel LPS-induced intracellular GSH level, however 200 μM LA reduced LPS-induced intracellular GSH level. GLA and LA dramatically inhibited LPS-induced IκBα degradation, IκBα-phosphorylation and nuclear p65 protein expression as well as NF-κB and AP-1 nuclear protein-DNA binding activity. Moreover, exogenous addition of GLA reduced LPS-induced phosphorylated extracellular signal-regulated kinase 1/2 (ERK 1/2), c-Jun N-terminal kinase 1 (JNK 1) but not p38 mitogen-activated kinase (p38 kinase) expression . Interestingly, exogenous addition of LA did not affect on LPS-induced mitogen-activated protein kinases (MAPK) activation. Base on our data the GLA and LA showed the different effect on LPS-induced events.Further more the anti-inflammatory ability of GLA is more efficiency than LA.