Department of Medicine, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Dis Esophagus. 2011 Apr;24(3):194-203. doi: 10.1111/j.1442-2050.2010.01127.x. Epub 2010 Nov 12.
Sensitization of esophageal nociceptive afferents by inflammatory mediators plays an important role in esophageal inflammatory nociception. Our previous studies demonstrated that esophageal mast cell activation increases the excitability of esophageal nodose C-fibers. But the intracellular mechanism of this sensitization process is still less clear. We hypothesize that extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling pathway plays an important role in mast cell activation-induced sensitization of esophageal nodose C-fiber neurons. Mast cell activation and in vivo esophageal distension-induced phosphorylations of ERK1/2 were studied by immuno-staining and Western blot in esophageal nodose neurons. Extracellular recordings were performed from nodose neurons using ex vivo esophageal-vagal preparations with intact nerve endings in the esophagus. Nerve excitabilities were compared by action potentials evoked by esophageal distensions before and after mast cell activations with/without pretreatment of mitogen-activated protein kinases (MAPK)/ERK kinase inhibitor U0126. The expressions of phospho-ERK1/2 (p-ERK1/2) in the same nodose ganglia were then studied by Western blot. Mast cell activation enhances in vivo esophageal distension-induced phosphorylation of ERK1/2 in nodose neurons. This can be prevented by pretreatment with mast cell stabilizer cromolyn. In ex vivo esophageal-vagal preparations, both mast cell activation and proteinase-activated receptor 2 (PAR2)-activating peptide perfusion increases esophageal distension-induced mechano-excitability of esophageal nodose C-fibers and phosphorylation of ERK1/2 in nodose neurons. Pretreatment with MAPK/ERK kinase inhibitor U0126 prevents these potentiation effects. Collectively, our data demonstrated that mast cell activation enhances esophageal distension-induced mechano-excitability and phosphorylation of ERK1/2 in esophageal nodose C-fiber neurons. This reveals a new intracellular pathway of esophageal peripheral sensitization and inflammatory nociception.
炎性介质对食管伤害感受器的致敏作用在食管炎症性伤害感受中起重要作用。我们之前的研究表明，食管肥大细胞激活增加了食管迷走神经 C 纤维的兴奋性。但这种敏化过程的细胞内机制仍不太清楚。我们假设细胞外信号调节激酶 1 和 2（ERK1/2）信号通路在肥大细胞激活诱导的食管迷走神经 C 纤维神经元敏化中起重要作用。通过免疫染色和 Western blot 研究了食管迷走神经神经元中肥大细胞激活和体内食管扩张诱导的 ERK1/2 磷酸化。使用具有完整食管神经末梢的离体食管迷走神经制备物，从迷走神经神经元进行细胞外记录。在肥大细胞激活前后，通过食管扩张诱发的动作电位比较神经兴奋性，肥大细胞激活前后分别用丝裂原激活蛋白激酶（MAPK）/ERK 激酶抑制剂 U0126 预处理。然后通过 Western blot 研究同一迷走神经节中磷酸化 ERK1/2（p-ERK1/2）的表达。肥大细胞激活增强了体内食管扩张诱导的迷走神经神经元 ERK1/2 的磷酸化。这可以通过肥大细胞稳定剂 cromolyn 的预处理来预防。在离体食管迷走神经制备物中，肥大细胞激活和蛋白酶激活受体 2（PAR2）激活肽灌流均增加了食管扩张诱导的食管迷走神经 C 纤维的机械兴奋性和迷走神经神经元 ERK1/2 的磷酸化。MAPK/ERK 激酶抑制剂 U0126 的预处理可预防这些增强作用。总之，我们的数据表明，肥大细胞激活增强了食管扩张诱导的食管迷走神经 C 纤维神经元的机械兴奋性和 ERK1/2 的磷酸化。这揭示了食管外周敏化和炎症性伤害感受的新细胞内途径。
