鱿鱼墨多糖改善小鼠肠粘膜免疫及作用机制的研究

Promotion effect of Squid Ink polysaccharide on intestinal mucosa immunity in mice

目的探讨鱿鱼墨多糖对小鼠肠粘膜免疫的影响及其作用机制。方法将50只Balb/c小鼠随机分为5组:正常组、模型组、低、中、高鱿鱼墨多糖剂量组。采用环磷酰胺腹腔注射法制备免疫低下小鼠模型,并通过灌胃给予各剂量组小鼠鱿鱼墨多糖饲养28 d。检测胸腺指数/脾指数,取小鼠空肠段检测肠粘膜SIgA的含量,观察北太平洋鱿鱼墨多糖对肠道粘膜免疫的保护作用。采用酶联免疫反应和RT-PCR方法,检测了pIgR的蛋白质与mRNA表达量。结果与正常组相比,模型组小鼠胸腺指数、脾指数分别下降44.4%、19.4%,肠道SIgA的表达量下降40.9%,免疫组织化学染色也显示肠道IgA明显下降;与模型组相比,鱿鱼墨多糖可以改善免疫低下小鼠的机体免疫功能,并且呈剂量依赖性,胸腺指数在模型组水平上分别升高了53.5%、67.6%、61.8%,脾指数分别升高了12.7%、13.1%、15.6%。鱿鱼墨多糖还可以提高小鼠肠粘膜SIgA的分泌功能,相比于模型组小鼠,鱿鱼墨多糖组小鼠SIgA的分泌量分别升高了43.9%、63.6%、68.7%;免疫组织化学染色发现鱿鱼墨多糖组小鼠肠道固有层中IgA明显增加,且ELISA检测发现鱿鱼墨多糖高剂量组小鼠小肠pIgR的蛋白表达量明显增加。结论北太平洋鱿鱼墨多糖能够促进小鼠肠粘膜SIgA的分泌,并呈剂量依赖关系,作用机制可能与其促进浆细胞分泌IgA以及促进上皮细胞分泌pIgR有关。

Aim To investigate intestinal mucosa immunoprotective effect of Squid Ink polysaccharide on mice. Methods Fifty mice were randomly divided into 5 groups： wild type group, model group, low dose group, medium dose group, and high dose group. Model of immunosuppressed mice was induced by cyclophosphamide treatment. Spleen/bodyweight index, thymus/bodyweight index, SIgA content in intestinal mucosa, relative pIgR mRNA and protein expression were detected. Results Compared with wild type group, cyclophosphamide made the mouse bodyweight decreased, and the thymus/bodyweight index, spleen/ bodyweight index were also decreased by 44. 4% and 19.4%, respectively. The SIgA content was decreased by 40. 9% when compared with wild type group. These results indicated that cyelophosphamide could damnify thymus and spleen to do harm to the immune system, and the intestinal mucosa immunity was also damaged by the decrease of SIgA secretion. However, compared with model group, low, medium and high doses Squid Ink polysaecharide exerted immunoprotective effects different degree. They enhanced the thymus/body-weight index by 53.5%, 67.6%, and 61.8%, respectively, and enhanced the spleen/bodyweight index by 12.7%, 13.1%, and 15.6% respectively. The secretion of SIgA was also increased by 43.9%, 63.6% , and 68.7% respectively. Immunohistochem- istry staining of IgA showed that the expression of IgA in small intestine lamina propria was improved by Squid Ink polysaccharide, especially in high dose group. Even though the Squid Ink polysaccharide showed no apparent effect on pIgR mRNA expression, but it did promote the production of pIgR in high dose group. The enhancement of the SIgA secretion relied on the increase of IgA secreted by plasma cell in lamina propria and the higher expression of pIgR in high dose group. Conclusion Squid Ink polysaccharide can improve the immunity of cyclophosphamide in- duced immunosupressed mice by stimulating the secretion of SIgA into the intestinal lumen, which shows a dose-dependent relationship.