Al Nabhani Ziad, Montcuquet Nicolas, Roy Maryline, Dussaillant Monique, Hugot Jean-Pierre, Barreau Frédérick
*Laboratoire d'excellence Inflamex, Université Paris-Diderot Sorbonne Paris-Cité, UMR 1149, Paris, France; †INSERM, UMR 1149, Paris, France; ‡INSERM, UMR 989, Paris, France; §Université Paris Descartes-Sorbonne Paris Cité, Institut IMAGINE, Paris, France; ‖Assistance Publique Hôpitaux de Paris, Services des Maladies Digestives et Respiratoires de l'Enfant et Service d'Anatomie Pathologique, Hôpital Robert Debré, Paris, France; and ¶Institut de Recherche en Santé Digestive IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, 31024 Toulouse, France.
Inflamm Bowel Dis. 2017 Jul;23(7):1109-1119. doi: 10.1097/MIB.0000000000001135.
Crohn's disease (CD) pathogenesis is multifactorial involving genetic and environmental factors. Loss of function mutations in the nucleotide oligomerization domain 2 (NOD2) gene are the main genetic risk factor for CD. Like patients with CD, Nod2 mice are characterized by an enhanced Th1 immune response and a defective mucosal barrier function evidenced by increased intestinal permeability. We previously showed that the latter is related to hematopoietic Nod2 deficiency. Our aim was to explore the mechanisms by which Nod2 expressed in the hematopoietic and in the nonhematopoietic compartments interplay to control epithelial paracellular permeability.
Depletion of CD4 T cells in Nod2 mice and treatments with inhibitors were conducted in chimeric mice transplanted with bone marrow cells from Nod2-deficient donors into Nod2-sufficient recipients or vice versa. Caco-2 cells overexpressing a NOD2 gene which did or did not include a CD-associated polymorphism were treated with inhibitors or siRNAs and cocultured with hematopoietic cells from Peyer's patches.
In vivo and in vitro Nod2 in hematopoietic cells regulates epithelial paracellular permeability through cytokine production influencing myosin light chain kinase (MLCK) activity. Indeed, tumor necrosis factor-α and interferon-γ secretion by CD4 T cells upregulated expression and activity of epithelial MLCK leading to increased epithelial tight junction opening. When stimulated by muramyl dipeptide, Nod2 in the nonhematopoietic compartment normalized the permeability and T-cell cytokine secretion and regulated MLCK activity. This MLCK regulation is mediated by TAK1 and RICK-dependent mechanisms.
Our study demonstrates how hematopoietic and nonhematopoietic Nod2 regulate intestinal barrier function, improving our knowledge on the mechanisms involved in CD pathogenesis.
克罗恩病（CD）的发病机制是多因素的，涉及遗传和环境因素。核苷酸寡聚化结构域2（NOD2）基因的功能缺失突变是CD的主要遗传风险因素。与CD患者一样，Nod2小鼠的特征是Th1免疫反应增强，且肠道通透性增加证明其黏膜屏障功能存在缺陷。我们之前表明，后者与造血系统中Nod2缺乏有关。我们的目的是探索造血和非造血区室中表达的Nod2相互作用以控制上皮细胞旁通透性的机制。
在将Nod2缺陷供体的骨髓细胞移植到Nod2充足受体或反之的嵌合小鼠中，对Nod2小鼠的CD4 T细胞进行耗竭并用抑制剂进行处理。对过表达或未过表达与CD相关多态性的NOD2基因的Caco-2细胞用抑制剂或小干扰RNA（siRNA）处理，并与派尔集合淋巴结的造血细胞共培养。
造血细胞中的Nod2在体内和体外通过影响肌球蛋白轻链激酶（MLCK）活性的细胞因子产生来调节上皮细胞旁通透性。实际上，CD4 T细胞分泌的肿瘤坏死因子-α和干扰素-γ上调了上皮MLCK的表达和活性，导致上皮紧密连接开放增加。当受到胞壁酰二肽刺激时，非造血区室中的Nod2使通透性和T细胞细胞因子分泌正常化，并调节MLCK活性。这种MLCK调节由TAK1和RICK依赖性机制介导。
我们的研究证明了造血和非造血Nod2如何调节肠道屏障功能，增进了我们对CD发病机制相关机制的了解。
