Division of Infectious Diseases, Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
Inflamm Bowel Dis. 2011 Jan;17(1):319-33. doi: 10.1002/ibd.21428. Epub 2010 Aug 18.
Although intestinal epithelial cells (IECs) are continually exposed to commensal microbes, under healthy conditions they contribute to intestinal homeostasis while keeping inflammatory responses in check. In response to invading pathogens, however, IECs respond vigorously by producing inflammatory mediators. To better understand the signals that regulate the inflammatory responses of IECs, we investigated whether the danger signal ATP (which is released from injured cells) could alter responses to bacterial products.
We measured chemokine production from Caco-2 cells stimulated with the Toll-like receptor 5 agonist flagellin with or without ATP. ATP increased flagellin-induced IL-8 secretion but reduced CCL20 secretion via distinct signaling pathways.
ATP-enhanced IL-8 production was only partly blocked by the P(2) receptor antagonist suramin and required activation of NF-κB while ATP-mediated reduction of CCL20 was completely blocked by suramin and required activation of ERK1/2. The effects of ATP on both chemokines required extracellular calcium but not phospholipase C, implicating P(2) X receptor involvement. To investigate how ATP alters IEC responses to bacterial products in vivo, mice receiving dextran sodium sulfate were given intrarectal flagellin with or without ATP. Addition of ATP to flagellin caused greater weight loss and increased antiflagellin antibody titers, as well as decreased colonic interferon gamma (IFN-γ) and higher antiflagellin IgG1/IgG2 ratios, which indicate decreased Th1 polarization.
Together, these data indicate that stress, in the form of extracellular ATP, reshapes both the inflammatory response of flagellin-stimulated IECs and downstream adaptive immunity, representing a possible strategy by which these cells differentiate between commensal and pathogenic bacteria.
尽管肠道上皮细胞 (IECs) 不断暴露于共生微生物中，但在健康状态下，它们有助于肠道稳态，同时控制炎症反应。然而，当遇到入侵病原体时，IECs 通过产生炎症介质做出强烈反应。为了更好地理解调节 IEC 炎症反应的信号，我们研究了损伤细胞释放的危险信号 ATP 是否可以改变对细菌产物的反应。
我们测量了 Caco-2 细胞在 TLR5 激动剂鞭毛蛋白刺激下有无 ATP 时趋化因子的产生。ATP 通过不同的信号通路增加了鞭毛蛋白诱导的 IL-8 分泌，但减少了 CCL20 的分泌。
ATP 增强的 IL-8 产生仅部分被 P2 受体拮抗剂苏拉明阻断，需要 NF-κB 的激活，而 ATP 介导的 CCL20 减少完全被苏拉明阻断，需要 ERK1/2 的激活。ATP 对两种趋化因子的作用都需要细胞外钙，但不需要磷脂酶 C，提示 P2X 受体的参与。为了研究 ATP 如何在体内改变 IEC 对细菌产物的反应，我们给接受葡聚糖硫酸钠的小鼠直肠内给予鞭毛蛋白和/或 ATP。在鞭毛蛋白中加入 ATP 会导致更严重的体重减轻和更高的抗鞭毛蛋白抗体滴度，以及降低结肠干扰素 γ (IFN-γ) 和更高的抗鞭毛蛋白 IgG1/IgG2 比值，这表明 Th1 极化减少。
这些数据表明，以细胞外 ATP 的形式出现的应激会重塑鞭毛蛋白刺激的 IEC 的炎症反应和下游适应性免疫，这代表了这些细胞区分共生和致病细菌的一种可能策略。
