探討蘆薈凝膠處理對細菌脂多醣體誘發炎症反應之影響

Abstract

近二十年來，人們廣泛利用蘆薈，甚至由蘆薈凝膠中萃取的特定成分已有成為醫藥製劑。而最近備受注目的為存在蘆薈凝膠中的多醣體可能具有的免疫調節與抗菌功效。因此，我們製備蘆薈凝膠物，並用於添加在離乳仔豬隻飼料中以探討其對豬隻免疫力的影響，並透過體外細胞試驗探討蘆薈凝膠之免疫調節功效性。 離乳仔豬在餵飼含0.2%蘆薈凝膠粉四週後，將細菌脂多醣（lipopolysaccharide, LPS）注入豬隻肌肉層，並分別在注射後第4、8、12、24、48及72小時採血測量血漿中免疫球蛋白IgG、IgM、腫瘤壞死因子阿法（Tumor necrosis factor-alpha; TNF-α）、迦瑪干擾素（Interferon-gamma; INF-□）及腎上腺皮質醇（cortisol）等細胞激素含量。試驗結果顯示（1）供餵蘆薈凝膠粉末可有效降低因注射細菌LPS所引起豬隻的死亡；（2）供餵蘆薈凝膠粉末，對豬隻血漿中的IgM與IgG含量無顯著影響；（3）蘆薈凝膠可顯著影響LPS所誘發血漿中過度表現的INF-□含量。 在體外試驗中，我們測定蘆薈凝膠萃取液活化巨噬細胞的功效。培養之RAW 264.7巨噬細胞分別於以細菌LPS或1, 2.5, 5 and 10 mg/mL蘆薈凝膠萃取液，或合併LPS與蘆薈凝膠萃取液處理之，再分別檢測與炎症相關的細胞激素分泌量、巨噬細胞表面標記CD11a、一氧化氮產生量及誘導性一氧化氮合成脢（iNOS）基因的表現等。試驗結果顯示：（1）就細胞型態的改變而言，蘆薈凝膠萃取液無法有效活化巨噬細胞；（2）蘆薈凝膠萃取液在LPS誘導細胞活化的過程中並非扮演協同作用的角色；（3）蘆薈萃取液會抑制一氧化氮合成脢基因的表現。 綜言之，本研究結果顯示蘆薈凝膠中雖含有可調節細胞激素產生與逆境誘發表現的因子，而這些作用在免疫調節扮有重要角色。然而，無論是蘆薈凝膠中的特定物質或其免疫調節作用的影響與機制，都須要許多持續性的實驗探討才能釐清。

In the decade, popular interest and use of the Aloe have increased dramatically and there are a lot of purified materials for Aloe gel used as a therapeutic agent. An advanced theme running through much recent research is the immuno-modulatory and anti-microbial properties of the Aloe polysaccharides. Therefore, we prepared Aloe gel derived products that was supplied as a feed additives for weaned pigs, and to investigate the effect of dietary Aloe gel supplementation on the immuno activity of pigs. Biological effects of the Aloe gel on immuno-modulation were evaluated via in vivo and in vitro experiments. The weaned pigs were fed the diet with the Aloe gel powder (0.2%). After 4 weeks, the pigs were injected intramuscularly with Escherichia coli lipopolysaccharide (LPS) challenge, followed the blood samples were collected at 0, 4, 8, 12, 24, 48 and 72 h for immunoglobulins G (IgG), IgM, TNF-alpha, IFN-gamma and cortisol analyses. The animal study revealed that Aloe gel supplementation (1) significantly reduced mortality of pigs challenged with LPS; (2) did not affect plasma IgG and IgM concentrations; and (3) significantly increased plasma IFN-gamma when compared to control group. In the in vitro study, the potential of macrophage activation by Aloe gel extract was tested. Macrophage RAW 264.7 cells were cultured in the presence or absence of LPS alone or in combination with 1, 2.5, 5 and 10 mg/mL of Aloe gel extract. Cytokines secretion, cell surface marker CD11a, NO production and iNOS mRNA expression in the RAW 264.7 cells were measured. Results also revealed that (1) base on the macrophage morphology, immuno-responses differed sittle in pigs of Aloe gel group; (2) LPS could not act synergistically to increase the Fc receptor expression in Aloe gel extract treatment group; and (3) Aloe gel extract treatment inhibited iNOS expression at the transcriptional level. In conclusion, the Aloe gel contains the factors regulating cytokines production and stress-induced gene expression which play roles on the immuno-modulation; however, the effects and mechanisms of such functions and factors remain to be largely explored.