基于GR和FXR-FGF15介导的非甾体类抗炎药相关性小肠损伤的作用机制研究

Small intestinal injury caused by nonsteroidal anti-inflammatory drugs (NSAIDs) is very common and clinically significant. However, the pathogenesis of NSAIDs-induced small intestinal injury remains elusive, and there are no proven-effective preventative and/or therapeutic measures. Our preliminary study demonstrated that dexamethasone (DEX) aggravated ibuprofen-induced small intestinal injury in mice via the glucocorticoid receptor (GR) signaling pathway. Based on our gene expression and metabolism data, we hypothesize that GR might interact with peroxisome proliferator-activated receptor alpha (PPARa) to induce the expression and activity of intestinal UDP-glucuronosyltransferases（UGTs), and thus increase the glucuronidation of NSAIDs and bile acids (BAs) in the intestine. The increased BA glucuronidation facilitates the elimination of BAs from the body, resulting in decreased BA concentrations and the subsequent “deactivation” of intestinal FXR-FGF15/19(fibroblast growth factor 15 or 19) signaling pathway, which plays a crucial role in regulating the intestinal integrity. To test our hypothesis, we will exploit various cell and murine models (GR-knockdown, PPARa-null and FXR-null mice), as well as molecular biology, cellular biology, and metabolism analytical techniques to determine the role of GR, PPARα and FXR in NSAIDs-induced small intestinal injury. We will elucidate the role of liver and intestine FXR signaling pathways in NSAIDs-induced small intestinal injury by using tissue-specific FXR-null mice. Additionally, we will test the therapeutic potential of two FXR activators and FGF19 recombinant protein for NSAIDs-induced small intestinal injury. The proposed studies will lead to new strategies and therapeutic targets for treating NSAIDs-induced small intestinal injury.

非甾体类抗炎药(NSAIDs)相关性小肠损伤发病率高、临床后果严重，但目前机制不明确，且无有效的治疗措施。课题组前期工作发现，地塞米松(DEX)可通过激活GR加重布洛芬对小鼠的小肠损伤。综合基因和代谢分析的结果，我们推测GR可能与PPARα协同作用诱导肠道UGT的表达，改变NSAIDs和胆汁酸代谢，进而抑制肠道FXR-FGF15/19信号通路，最终导致NSAIDs相关性小肠损伤。为验证该假说，本项目拟采用GR低表达、PPARα敲除和FXR敲除鼠以及多种细胞模型，通过分子细胞生物学、代谢分析等手段，阐明GR、PPARα和FXR在DEX加重NSAIDs小肠损伤中的作用；拟采用组织选择性FXR敲除鼠，明确肠道和肝脏FXR信号通路在NSAIDs相关性小肠损伤中的作用，并探索FXR激动剂和FGF19重组蛋白对其治疗和保护作用，为NSAIDs相关性小肠损伤的防治以及新型NSAIDs的开发提供新靶点。

目前关于NSAIDs相关性小肠损伤的确切机制尚不明确，本项目旨在对其发病机制进行探索。根据前期数据，我们推测糖皮质激素受体（GR）和法尼醇X受体（FXR）可能是地塞米松加重布洛芬肠毒性中的关键机制。在该项目中，我们首先建立了一个同时检测40种胆汁酸的LC-MS方法，用该方法表征了地塞米松通过GR对小鼠体内胆汁酸代谢的影响。接着从分子、细胞、动物水平上阐明了地塞米松通过肠道GR-FXR轴加重布洛芬肠毒性的机制，发现地塞米松通过增加肝脏和肠道中胆汁酸转运体来增加胆汁分泌，同时升高FXR内源性拮抗剂TMCA的含量来抑制肠道FXR的信号通路，降低CSE的活性，减少肠道保护气体H2S的产生。地塞米松还可以激活肠道PPARα-UGT信号通路来增加IBU的糖醛酸化，从而增加IBU和IBU-AG的肝肠循环。最后，地塞米松可以显著改变肠道细菌，尤其是降低了肠道保护细菌。我们的结果表明FXR激活剂对NSAIDs相关性小肠损伤具有潜在的防治作用。我们还发现FXR信号通路在糖尿病脑病的发展和大黄素导致胆汁淤积肝毒性中起着关键作用，并通过迷走神经隔断大鼠模型，明确了FXR在神经系统中的作用。我们研究了布洛芬对地塞米松诱导脂肪肝的保护作用，发现FXR和胆汁酸代谢是关键机制。最后，我们还考察了地塞米松对尿酸代谢的影响，发现GR对尿酸转运体具有调控作用。经过该项目的实施，我们建立了研究GR和FXR的关键方法和模型，包括胆汁酸和肠道菌检测方法以及基因敲除细胞或动物等，为临床治疗NSAIDs相关性小肠损伤提供了新策略，为脑病的发展提供了新机制，为含大黄素等中药的肝毒性提出了新模型，为高尿酸血症的治疗提供了新靶点。

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