Kearon Joanne E, Kocherry S C, Zoumboulakis D, Rivera D, Lourenssen S R, Blennerhassett M G
Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON K7L 2V7, Canada.
Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON K7L 2V7, Canada.
Mol Cell Neurosci. 2021 Sep;115:103655. doi: 10.1016/j.mcn.2021.103655. Epub 2021 Jul 15.
Intestinal inflammation challenges both function and structure of the enteric nervous system (ENS). In the animal model of TNBS-induced colitis, an influx of immune cells causes early neuron death in the neuromuscular layers, followed by axonal outgrowth from surviving neurons associated with upregulation of the neurotrophin GDNF (glial cell line-derived neurotrophic factor). Inflammation could involve ischemia and metabolic inhibition leading to neuronal damage, which might be countered by a protective action of GDNF. This was examined in a primary co-culture model of rat myenteric neurons and smooth muscle, where metabolic challenge was caused by dinitrophenol (DNP), O-methyl glucose (OMG) or hypoxia. These caused the specific loss of 50% of neurons by 24 h that was blocked by GDNF both in vitro and in whole mounts. Neuroprotection was lost with RET inhibition by vandetanib or GSK3179106, which also caused neuron loss in untreated controls. Thus, both basal and upregulated GDNF levels signal via RET for neuronal survival. This includes a key role for upregulation of HIF-1α, which was detected in neurons in colitis, since the inhibitor chetomin blocked rescue by GDNF or ischemic pre-conditioning in vitro. In DNP-treated co-cultures, neuron death was not inhibited by zVAD, necrosulfonamide or GSK872, and cleaved caspase-3 or - 8 were undetectable. However, combinations of inhibitors or the RIP1kinase inhibitor Nec-1 prevented neuronal death, evidence for RIPK1-dependent necroptosis. Therefore, inflammation challenges enteric neurons via ischemia, while GDNF is neuroprotective, activating RET and HIF-1α to limit programmed cell death. This may support novel strategies to address recurrent inflammation in IBD.
肠道炎症对肠神经系统（ENS）的功能和结构都构成了挑战。在三硝基苯磺酸（TNBS）诱导的结肠炎动物模型中，免疫细胞的涌入导致神经肌肉层早期神经元死亡，随后存活神经元的轴突发芽，同时神经营养因子胶质细胞源性神经营养因子（GDNF）上调。炎症可能涉及局部缺血和代谢抑制，从而导致神经元损伤，而GDNF的保护作用可能会对抗这种损伤。这在大鼠肌间神经元和平滑肌的原代共培养模型中进行了研究，其中代谢挑战由二硝基苯酚（DNP）、O-甲基葡萄糖（OMG）或缺氧引起。这些因素在24小时内导致50%的神经元特异性丧失，而GDNF在体外和整体标本中均能阻止这种情况。凡德他尼或GSK3179106抑制RET后，神经保护作用丧失，这也导致未处理对照组中的神经元丧失。因此，基础和上调的GDNF水平均通过RET发出神经元存活信号。这包括缺氧诱导因子-1α（HIF-1α）上调的关键作用，在结肠炎的神经元中检测到了HIF-1α，因为抑制剂chetomin在体外阻断了GDNF或缺血预处理的拯救作用。在DNP处理的共培养物中，zVAD、坏死磺酰胺或GSK872均未抑制神经元死亡，且未检测到裂解的半胱天冬酶-3或-8。然而，抑制剂组合或RIP1激酶抑制剂Nec-1可预防神经元死亡，这是RIPK1依赖性坏死性凋亡的证据。因此，炎症通过局部缺血挑战肠神经元，而GDNF具有神经保护作用，激活RET和HIF-1α以限制程序性细胞死亡。这可能为解决炎症性肠病（IBD）的复发性炎症提供新策略。
