Abstract：
Ephrin-B-EphB signaling can promote pain through ligand-receptor interactions between peripheral cells, like immune cells expressing ephrin-Bs, and EphB receptors expressed by DRG neurons. Previous studies have shown increased ephrin-B2 expression in peripheral tissues like synovium of rheumatoid and osteoarthritis patients, indicating the clinical significance of this signaling. The primary goal of this study was to understand how ephrin-B2 acts on mouse and human DRG neurons, which express EphB receptors, to promote pain and nociceptor plasticity. We hypothesized that ephrin-B2 would promote nociceptor plasticity and hyperalgesic priming through MNK-eIF4E signaling, a critical mechanism for nociceptive plasticity induced by growth factors, cytokines and nerve injury. Both male and female mice developed dose-dependent mechanical hypersensitivity in response to ephrin-B2, and both sexes showed hyperalgesic priming when challenged with PGE2 injection either to the paw or the cranial dura. Acute nociceptive behaviors and hyperalgesic priming were blocked in mice lacking MNK1 (Mknk1 knockout mice) and by eFT508, a specific MNK inhibitor. Sensory neuron-specific knockout of EphB2 using Pirt-Cre demonstrated that ephrin-B2 actions require this receptor. In Ca2+-imaging experiments on cultured DRG neurons, ephrin-B2 treatment enhanced Ca2+ transients in response to PGE2 and these effects were absent in DRG neurons from MNK1-/- and EphB2-PirtCre mice. In experiments on human DRG neurons, ephrin-B2 increased eIF4E phosphorylation and enhanced Ca2+ responses to PGE2 treatment, both blocked by eFT508. We conclude that ephrin-B2 acts directly on mouse and human sensory neurons to induce nociceptor plasticity via MNK-eIF4E signaling, offering new insight into how ephrin-B signaling promotes pain.
摘要：
Ephrin-B-EphB信号传导可以通过外周细胞之间的配体-受体相互作用促进疼痛，像表达ephrin-Bs的免疫细胞，和DRG神经元表达的EphB受体。先前的研究表明，类风湿和骨关节炎患者的周围组织如滑膜中的ephrin-B2表达增加，表明这种信号的临床意义。这项研究的主要目的是了解ephrin-B2如何作用于小鼠和人类DRG神经元，表达EphB受体，促进疼痛和伤害性感受器可塑性。我们假设ephrin-B2会通过MNK-eIF4E信号促进痛觉感受器可塑性和痛觉过敏启动，生长因子诱导的伤害性可塑性的关键机制，细胞因子和神经损伤。雄性和雌性小鼠都对ephrin-B2产生了剂量依赖性的机械性超敏反应，当用PGE2注射到爪或颅硬脑膜时，两种性别都显示出痛觉过敏。在缺乏MNK1的小鼠（Mknk1敲除小鼠）和特定MNK抑制剂eFT508中，急性伤害性行为和痛觉过敏引发被阻断。使用Pirt-Cre对EphB2的感觉神经元特异性敲除证明了ephrin-B2的作用需要该受体。在培养的DRG神经元的Ca2+成像实验中，ephrin-B2处理增强了对PGE2的响应的Ca2瞬变，这些作用在MNK1-/-和EphB2-PirtCre小鼠的DRG神经元中不存在。在人类DRG神经元的实验中，ephrin-B2增加eIF4E磷酸化和增强Ca2+对PGE2处理的反应，都被eFT508阻止。我们得出结论，ephrin-B2直接作用于小鼠和人类感觉神经元，通过MNK-eIF4E信号诱导伤害感受器可塑性，提供了关于ephrin-B信号如何促进疼痛的新见解。
