Division of Gastroenterology and Hepatology, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany.
J Immunol. 2013 Jun 1;190(11):5676-88. doi: 10.4049/jimmunol.1201592. Epub 2013 May 1.
Variants of the multidrug resistance gene (MDR1/ABCB1) have been associated with increased susceptibility to severe ulcerative colitis (UC). In this study, we investigated the role of TLR/IL-1R signaling pathways including the common adaptor MyD88 in the pathogenesis of chronic colonic inflammation in MDR1A deficiency. Double- or triple-null mice lacking TLR2, MD-2, MyD88, and MDR1A were generated in the FVB/N background. Deletion of TLR2 in MDR1A deficiency resulted in fulminant pancolitis with early expansion of CD11b(+) myeloid cells and rapid shift toward TH1-dominant immune responses in the lamina propria. Colitis exacerbation in TLR2/MDR1A double-knockout mice required the unaltered commensal microbiota and the LPS coreceptor MD-2. Blockade of IL-1β activity by treatment with IL-1R antagonist (IL-1Ra; Anakinra) inhibited colitis acceleration in TLR2/MDR1A double deficiency; intestinal CD11b(+)Ly6C(+)-derived IL-1β production and inflammation entirely depended on MyD88. TLR2/MDR1A double-knockout CD11b(+) myeloid cells expressed MD-2/TLR4 and hyperresponded to nonpathogenic Escherichia coli or LPS with reactive oxygen species production and caspase-1 activation, leading to excessive cell death and release of proinflammatory IL-1β, consistent with pyroptosis. Inhibition of reactive oxygen species-mediated lysosome degradation suppressed LPS hyperresponsiveness. Finally, active UC in patients carrying the TLR2-R753Q and MDR1-C3435T polymorphisms was associated with increased nuclear expression of caspase-1 protein and cell death in areas of acute inflammation, compared with active UC patients without these variants. In conclusion, we show that the combined defect of two UC susceptibility genes, MDR1A and TLR2, sets the stage for spontaneous and uncontrolled colitis progression through MD-2 and IL-1R signaling via MyD88, and we identify commensally induced pyroptosis as a potential innate immune effector in severe UC pathogenesis.
多药耐药基因（MDR1/ABCB1）的变异与严重溃疡性结肠炎（UC）的易感性增加有关。在这项研究中，我们研究了 TLR/IL-1R 信号通路，包括常见接头分子 MyD88，在 MDR1A 缺乏的慢性结肠炎症发病机制中的作用。在 FVB/N 背景下，生成了缺失 TLR2、MD-2、MyD88 和 MDR1A 的双缺失或三缺失小鼠。在 MDR1A 缺陷的情况下，TLR2 的缺失导致暴发性全结肠炎，伴有 CD11b（+）髓样细胞的早期扩张，并迅速向固有层中的 TH1 优势免疫反应转变。TLR2/MDR1A 双敲除小鼠的结肠炎恶化需要未改变的共生微生物群和 LPS 核心受体 MD-2。通过使用白细胞介素 1 受体拮抗剂（白细胞介素 1 拮抗剂；Anakinra）阻断白细胞介素 1β 的活性抑制了 TLR2/MDR1A 双缺失中的结肠炎加速；肠道 CD11b（+）Ly6C（+）衍生的白细胞介素 1β 产生和炎症完全依赖于 MyD88。TLR2/MDR1A 双敲除 CD11b（+）髓样细胞表达 MD-2/TLR4，并对非致病性大肠杆菌或 LPS 产生超反应，导致活性氧物质产生和半胱天冬酶-1 激活，从而导致过度细胞死亡和促炎白细胞介素 1β 的释放，与细胞焦亡一致。抑制活性氧物质介导的溶酶体降解抑制了 LPS 的超反应性。最后，与没有这些变体的活动性 UC 患者相比，携带 TLR2-R753Q 和 MDR1-C3435T 多态性的活动性 UC 患者的 caspase-1 蛋白核表达和急性炎症区域的细胞死亡增加。总之，我们表明，两个 UC 易感性基因 MDR1A 和 TLR2 的联合缺陷通过 MyD88 通过 MD-2 和 IL-1R 信号通路为自发性和不受控制的结肠炎进展奠定了基础，并且我们确定共生诱导的细胞焦亡是严重 UC 发病机制中的潜在先天免疫效应物。
