本硏究是延續本實驗室之前發現，探討炸油抑制腸免疫力的機轉。先前實驗室的硏究發現炸油抑制小鼠專一性與非專一性抗體反應，血清 IgA (Immunoglobulin A) 濃度增加和糞便 IgA 濃度下降。細胞激素在調節免疫反應上扮演重要的角色，炸油可能藉由改變腸免疫細胞細胞激素表現而抑制專一性與非專一性抗體免疫反應。腸腔 (糞便) IgA 來源有二途徑:小腸上皮細胞 pIgR (polymeric immunoglobulin receptor) 負責運送固有層中雙體 IgA 到腸腔; 肝細胞 pIgR 則是負責血中雙體或多聚體 IgA 經由膽汁運送至腸腔，推測炸油可能影響小腸和肝 pIgR 的表現而導致血清 IgA 濃度增加和糞便 IgA 濃度下降。
實驗一的目的是探討餵食炸油六週對小鼠皮爾氏斑、腸繫膜淋巴結細胞激素和肝細胞 pIgR 表現之影響。60 隻 5 週齡 C57BL/6J 雌小鼠隨機分為四組，分別飼以 7% 和 15% 新鮮黃豆油 (C組、HC組) 或炸油 (O 組、HO組)。結果顯示炸油會顯著減少小鼠的飼料攝取量與終體重。IgA 濃度為 HO 組血清顯著高於 HC 組，糞便 IgA 濃度則是 HO 組顯著低於 HC 組。炸油降低肝細胞 pIgR 的表現量，O 和 HO 組 pIgR 表現與對照組比較分別減少 40% 和 60%。皮爾氏斑細胞激素炸油小鼠 (O、HO 組) IL-4表現受油脂品質影響而增加，IL-6 則受到油脂品質與含量影響而增加；腸繫膜淋巴結細胞激素則不受油脂品質與含量的影響。
實驗二的目的是探討餵食四週炸油對小鼠腸上皮細胞和肝細胞 pIgR 表現與血清 IgA 分子分佈之影響。此實驗除了C、H、O和HO組外，因實驗一結果炸油減少飼料攝取量，故增加高低油對飼育組 (PO和PHO組)。結果顯示對飼育組的血清、小腸內容物與糞便 IgA 含量與對照組比較均無顯著差異。HO 組小腸內容物與糞便 IgA 均顯著減少，血清 IgA濃度卻顯著增加。炸油對腸上皮細胞 pIgR 表現無影響，但肝細胞 pIgR 表現有顯著降低，O 和 HO 組表現量與對照組比較分別減少的 30% 與 50%，PO 和 PHO 對飼育組則不因降低飼料攝取量而減少肝細胞 pIgR 表現。另一方面，Western blot 發現雙體和多聚體 IgA 皆有增加，以雙體 IgA 增加最為顯著，與炸油減少肝細胞 pIgR 表現的結果相符。綜合上述結果，炸油影響腸非專一性抗體免疫反應是經由降低肝細胞 pIgR 表現進而影響血清、小腸內容物與糞便 IgA 的含量。
關鍵字:皮爾氏斑、腸繫膜淋巴結、炸油、細胞激素、pIgR、IgA This study is to extend the previous finding in our laboratory and to investigate the mechanistic effect of deep frying oil (DFO) on gut immune response. Our previous results showed that DFO depressed the gut specific and non-specific antibody responses concomitantly with a high concentration of serum IgA and a low concentration of fecal IgA in mice. Cytokine plays an important role in regulation of immune response. The depression effect of gut antibody response by DFO may be caused by the alteration of cytokine expression in gut immune cells. Gut luminal IgA comes from two sources: 1)the intestinal polymeric immunoglobulin receptor (pIgR) transports dimeric IgA (dIgA) from the lamina propria to the gut lumen, and 2)the hepatic pIgR transports the serum dIgA via bile to the gut lumen. We hypothesize that the elevation of serum IgA and the low fecal IgA concentration in previous results is contributed by the reduction of pIgR in DFO fed mice.
The objectives of experiment 1 were to study the effect of DFO on the cytokines gene expression of Peyer’s patches (PP) and mesenteric lymph node (MLN) cells as well as the hepatic pIgR gene expression. Sixty-five week old female C57BL/6J mice were divided into four groups and fed 7% and 15% fresh (C and HC) or DFO soybean oil (O and HO) for 6 weeks. The final body weight and feed intake were significantly reduced in mice fed DFO. IL-2 and IL-4 genes expression were significantly increased in PP by DFO . By contrast, IL-2, IL-4, IL-6 and TNF-?expression in MLN were not affected by DFO. The hepatic pIgR in O and HO groups were reduced 40% and 60% compared to C and HC groups, respectively. Elevation of serum IgA concentration and reduction of fecal IgA concentration were found in the HO group.
The experiment 2 was to study the intestinal and hepatic pIgR expression as well as the molecular form distribution of serum IgA in mice fed DFO for 4 weeks. Since DFO reduced feed intake in experiment 1, experiment 2 included a two pair-fed group (PO and PHO). Results showed that the reduction of feed intake did not affect the serum, intestinal luminal content and fecal IgA concentration. DFO significantly increased the serum IgA concentration and significantly decreased the fecal IgA concentration. Although hepatic pIgR gene expression was markedly decreased in O and HO groups, intestinal pIgR was not affected by DFO. Western blotting revealed an elevation in concentration of dimeric and polymeric forms of serum IgA in the HO group.
Taken together, DFO has an inhibitory effect on hepatic pIgR. Elevation of serum IgA and low fecal IgA concentration is partially contributed by low hepatic pIgR expression in mice fed DFO.
Key word: Peyer’s patches、Mesenteric lymph node、Frying oil、Cytokine、pIgR、IgA
