The pathogenic roles of GSDMD-dependent gut epithelium extracellular vesicles in IBD

摘要 了解环境因素如何触发失调的免疫反应被认为是炎症性肠病(IBD)发病机制临床前研究的关键挑战。肠上皮细胞(IECS)对管腔环境的异常反应被广泛认为是IBD的驱动因素。另一方面，免疫调节生物制剂的成功，如vedolizumab和ustekinumab，清楚地表明T细胞，特别是致病T细胞在IBD中的中心作用。然而，目前尚不清楚IECS如何将粘膜表面的先天免疫检测传递给获得性免疫反应和随后的炎症。在这种感知功能的中心出现的是炎症体，它可以检测细胞应激和危险信号，如在慢性炎症期间在受损组织中发现的ATP。为了了解炎症小体在IECS中的作用，我们发现IECS以GSDMD依赖的方式释放大量含有多泛素化IL-1家族细胞因子的细胞外小泡(SEV)，包括IL-1和IL-18，以响应炎症小体的激活。重要的是，IEC衍生的SEV代表了IEC和T细胞之间的一种新的通讯形式。尤其是IL-18通过诱导炎症性T细胞产生干扰素？和GM-CSF的产生。来自发炎的小鼠结肠的SEV-在T细胞转移性结肠炎模型中加重疾病并对抗肿瘤坏死因子治疗产生抵抗。与非炎症区相比，IBD患者炎症区活检组织的IECs产生SEV的能力一直较强。因此，我们推测，IEC来源的SEV在IBD的发病机制中发挥了关键作用，它通过释放含有IL-1家族细胞因子(包括IL-1和IL-18，可能还有IL-33)的SEV来放大上皮炎症反应，促进致病T细胞的产生。本申请旨在确定SEV释放的分子机制(S)，并评估SEV在促进小鼠结肠炎模型和IBD患者患者标本中致病T细胞和抗肿瘤坏死因子治疗失败方面的重要性。

Abstract Understanding how environmental factors trigger dysregulated immune responses was identified as a key challenge in preclinical research for the pathogenesis of inflammatory bowel disease (IBD). Dysregulated responses to the luminal environment by intestinal epithelial cells (IECs) have been widely postulated to be a driver of IBD. On the other hand, the success of immunomodulatory biologics, such as vedolizumab and ustekinumab, clearly demonstrate the central role of T cells, especially pathogenic T cells, in IBD. However, it remains unclear how IECs convey innate immune detection at mucosal surfaces to adaptive immune responses and subsequent inflammation. Emerging at the center of this sensing function is the inflammasome, which can detect cellular stress and danger signals, such as ATP, found in injured tissues during chronic inflammation. In our quest to understand the role of the inflammasome in IECs, we found that IECs release large amounts of small extracellular vesicles (sEVs) containing polyubiquitinated IL-1 family cytokines, including IL-1 and IL-18, in response to inflammasome activation in a GSDMD-dependent manner. Importantly, IEC-derived sEVs represent a novel form of communication between IECs and T cells. In particular, IL-18 promotes inflammatory pathogenic T cells via induction of IFN? and GM-CSF production. sEVs-derived from inflamed mouse colons exacerbate disease and confer resistance to anti-TNF treatment in a T cell transfer colitis model. Consistently, IECs from biopsies of inflamed areas from IBD patients displayed enhanced capacity to produce sEVs compared to that from non-inflamed areas. Thus, we hypothesize that IEC-derived sEVs play a critical role in IBD pathogenesis by amplifying epithelial inflammatory responses and promoting pathogenic T cells via the release of sEVs containing IL-1 family cytokines, including IL-1 and IL-18, and perhaps IL-33. This application seeks to determine the molecular mechanism(s) that underlie the release of sEVs and assess the importance of sEVs in promoting pathogenic T cells and anti-TNF therapy failure in murine models of colitis and in patient-derived specimens from IBD patients.