Department of Pediatrics, Northwestern University Feinberg School of Medicine/Children's Memorial Hospital, Chicago, IL 60611, USA.
Infect Immun. 2011 May;79(5):1863-72. doi: 10.1128/IAI.01025-10. Epub 2011 Feb 22.
Citrobacter rodentium infection of mice induces cell-mediated immune responses associated with crypt hyperplasia and epithelial β-catenin signaling. Recent data suggest that phosphatidylinositol-3-kinase (PI3K)/Akt signaling cooperates with Wnt to activate β-catenin in intestinal stem and progenitor cells through phosphorylation at Ser552 (P-β-catenin(552)). Our aim was to determine whether epithelial PI3K/Akt activation is required for β-catenin signaling and host defense against C. rodentium. C57BL/6 mice were infected with C. rodentium and treated with dimethyl sulfoxide (DMSO) (vehicle control) or with the PI3K inhibitor LY294002 or wortmannin. The effects of infection on PI3K activation and β-catenin signaling were analyzed by immunohistochemistry. The effects of PI3K inhibition on host defense were analyzed by the quantification of splenic and colon bacterial clearance, and adaptive immune responses were measured by real-time PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Increased numbers of P-β-catenin(552)-stained epithelial cells were found throughout expanded crypts in C. rodentium colitis. We show that the inhibition of PI3K signaling attenuates epithelial Akt activation, the Ser552 phosphorylation and activation of β-catenin, and epithelial cell proliferative responses during C. rodentium infection. PI3K inhibition impairs bacterial clearance despite having no impact on mucosal cytokine (gamma interferon [IFN-γ], tumor necrosis factor [TNF], interleukin-17 [IL-17], and IL-1β) or chemokine (CXCL1, CXCL5, CXCL9, and CXCL10) induction. The results suggest that the host defense against C. rodentium requires epithelial PI3K activation to induce Akt-mediated β-catenin signaling and the clearance of C. rodentium independent of adaptive immune responses.
柠檬酸杆菌感染小鼠诱导与隐窝增生和上皮 β-连环蛋白信号相关的细胞介导免疫反应。最近的数据表明，磷脂酰肌醇-3-激酶（PI3K）/Akt 信号通过丝氨酸 552 位磷酸化（P-β-连环蛋白（552））与 Wnt 合作激活肠干细胞和祖细胞中的 β-连环蛋白。我们的目的是确定上皮细胞 PI3K/Akt 激活是否是 β-连环蛋白信号和宿主防御柠檬酸杆菌所必需的。C57BL/6 小鼠感染柠檬酸杆菌并用二甲基亚砜（DMSO）（载体对照）或 PI3K 抑制剂 LY294002 或渥曼青霉素处理。通过免疫组织化学分析感染对 PI3K 激活和 β-连环蛋白信号的影响。通过定量脾和结肠细菌清除来分析 PI3K 抑制对宿主防御的影响，通过实时 PCR（RT-PCR）和酶联免疫吸附测定（ELISA）测量适应性免疫反应。在柠檬酸杆菌结肠炎中，在扩大的隐窝中发现了更多数量的 P-β-连环蛋白（552）染色的上皮细胞。我们表明，PI3K 信号转导的抑制减弱了上皮细胞 Akt 的激活、β-连环蛋白的丝氨酸 552 位磷酸化和激活以及柠檬酸杆菌感染期间上皮细胞的增殖反应。尽管 PI3K 抑制对黏膜细胞因子（γ干扰素[IFN-γ]、肿瘤坏死因子[TNF]、白细胞介素 17[IL-17]和白细胞介素 1β）或趋化因子（CXCL1、CXCL5、CXCL9 和 CXCL10）诱导没有影响，但它会损害细菌清除。结果表明，宿主防御柠檬酸杆菌需要上皮细胞 PI3K 激活来诱导 Akt 介导的 β-连环蛋白信号和柠檬酸杆菌的清除，而无需适应性免疫反应。
