Agaricus brasiliensis polysaccharides stimulate human monocytes to capture Candida albicans, express toll-like receptors 2 and 4, and produce pro-inflammatory cytokines

Abstract Background Agaricus brasiliensis is a medicinal mushroom with immunomodulatory and antitumor activities attributed to the β-glucans presented in the polysaccharide fraction of its fruiting body. Since β-glucans enhance cellular immunoresponsiveness, in this study we aimed to evaluate the effect of an acid-treated polysaccharide-rich fraction (ATF) of A. brasiliensis on the ability of human monocytes to adhere/phagocyte C. albicans yeast cells, their expression of pattern recognition receptors and their ability to produce cytokines. Methods Adhesion/phagocytosis of FITC-labeled C. albicans was evaluated by flow cytometry. Cells were incubated with specific fluorochrome-labeled antibodies for TLR2 and 4, βGR and MR and also evaluated by flow cytometry. Monocytes were cultured with ATF, and culture supernatants were collected for analysis of in vitro cytokine production by ELISA (TNF-α, IL-1β, IL-12 and IL-10). Results ATF significantly increased the adherence/phagocytosis of C. albicans by monocytes and this was associated with enhanced expression of TLR2 and TLR4, while no effect was observed on βGR or MR. Moreover, expression of TLR4 and TLR2 was associated with higher levels of in vitro production of TNF-α and IL-1, respectively. Production of IL-10 was also increased by ATF treatment, but we found no association between its production and the expression of Toll-like receptors. Conclusion Our results provided us with evidence that A. brasiliensis polysaccharides affect human monocytes probably through the modulation of Toll-like receptors.

【背景摘要】巴西蘑菇（Agaricus brasiliensis）是一种兼具免疫调节与抗肿瘤活性的药用真菌，其活性成分为子实体多糖组分中的β-葡聚糖。鉴于β-葡聚糖可增强细胞免疫应答能力，本研究旨在评估经酸处理的巴西蘑菇多糖富集组分（ATF）对人单核细胞黏附/吞噬白色念珠菌（Candida albicans, C. albicans）酵母细胞的能力、模式识别受体（pattern recognition receptors）表达水平，以及单核细胞产生细胞因子能力的影响。
【研究方法】采用流式细胞术检测异硫氰酸荧光素（FITC）标记的白色念珠菌的黏附/吞噬情况；使用针对Toll样受体2（Toll-like receptor 2, TLR2）、Toll样受体4（Toll-like receptor 4, TLR4）、β-葡聚糖受体（β-glucan receptor, βGR）与甘露糖受体（mannose receptor, MR）的荧光素标记抗体孵育细胞，同样通过流式细胞术分析受体表达；将单核细胞与ATF共培养，收集培养上清液，采用酶联免疫吸附测定（ELISA）检测体外培养的肿瘤坏死因子α（TNF-α）、白细胞介素1β（IL-1β）、白细胞介素12（IL-12）及白细胞介素10（IL-10）的产生水平。
【研究结果】ATF可显著提升单核细胞对白色念珠菌的黏附与吞噬能力，该效应与TLR2、TLR4的表达上调相关，但对βGR或MR的表达无显著影响。进一步分析显示，TLR4与TLR2的表达分别与体外TNF-α及IL-1的产生水平升高呈正相关；ATF处理还可上调IL-10的产生，但该效应与Toll样受体的表达无关联。
【研究结论】本研究结果证实，巴西蘑菇多糖可通过调控Toll样受体通路，进而影响人单核细胞的免疫功能。