Yu Shaoyong, Gao Guofeng, Peterson Blaise Z, Ouyang Ann
Division of Gastroenterology and Hepatology, The Milton S. Hershey Medical Center, Penn State University College of Medicine, 500 Univ. Drive, Hershey, PA 17033, USA.
Am J Physiol Gastrointest Liver Physiol. 2009 Jul;297(1):G34-42. doi: 10.1152/ajpgi.00068.2009. Epub 2009 May 7.
Sensitization of esophageal sensory afferents by inflammatory mediators plays an important role in esophageal nociception. We have shown esophageal mast cell activation induces long-lasting mechanical hypersensitivity in vagal nodose C-fibers. However, the roles of mast cell mediators and downstream ion channels in this process are unclear. Mast cell tryptase via protease-activated receptor 2 (PAR2)-mediated pathways sensitizes sensory nerves and induces hyperalgesia. Transient receptor potential A1 (TRPA1) plays an important role in mechanosensory transduction and nociception. Here we tested the hypothesis that mast cell activation via a PAR2-dependent mechanism sensitizes TRPA1 to induce mechanical hypersensitivity in esophageal vagal C-fibers. The expression profiles of PAR2 and TRPA1 in vagal nodose ganglia were determined by immunostaining, Western blot, and RT-PCR. Extracellular recordings from esophageal nodose neurons were performed in ex vivo guinea pig esophageal-vagal preparations. Action potentials evoked by esophageal distention and chemical perfusion were compared. Both PAR2 and TRPA1 expressions were identified in vagal nodose neurons by immunostaining, Western blot, and RT-PCR. Ninety-one percent of TRPA1-positive neurons were of small and medium diameters, and 80% coexpressed PAR2. Esophageal mast cell activation significantly enhanced the response of nodose C-fibers to esophageal distension (mechanical hypersensitivity). This was mimicked by PAR2-activating peptide, which sustained for 90 min after wash, but not by PAR2 reverse peptide. TRPA1 inhibitor HC-030031 pretreatment significantly inhibited mechanical hypersensitivity induced by either mast cell activation or PAR2 agonist. Collectively, our data provide new evidence that sensitizing TRPA1 via a PAR2-dependent mechanism plays an important role in mast cell activation-induced mechanical hypersensitivity of vagal nodose C-fibers in guinea pig esophagus.
炎症介质对食管感觉传入神经的致敏作用在食管伤害感受中起重要作用。我们已经表明，食管肥大细胞活化可诱导迷走神经结状C纤维产生持久的机械性超敏反应。然而，肥大细胞介质和下游离子通道在此过程中的作用尚不清楚。肥大细胞类胰蛋白酶通过蛋白酶激活受体2（PAR2）介导的途径使感觉神经致敏并诱导痛觉过敏。瞬时受体电位A1（TRPA1）在机械感觉转导和伤害感受中起重要作用。在此，我们检验了以下假设：通过PAR2依赖性机制激活肥大细胞可使TRPA1致敏，从而诱导豚鼠食管迷走神经C纤维产生机械性超敏反应。通过免疫染色、蛋白质印迹法和逆转录-聚合酶链反应（RT-PCR）确定PAR2和TRPA1在迷走神经结状神经节中的表达谱。在离体豚鼠食管-迷走神经标本中对食管结状神经元进行细胞外记录。比较食管扩张和化学灌注诱发的动作电位。通过免疫染色、蛋白质印迹法和RT-PCR在迷走神经结状神经元中鉴定出PAR2和TRPA1的表达。91%的TRPA1阳性神经元为中小直径，80%共表达PAR2。食管肥大细胞活化显著增强了结状C纤维对食管扩张的反应（机械性超敏反应）。PAR2激活肽可模拟此反应，冲洗后可持续90分钟，但PAR2反向肽则不能。TRPA1抑制剂HC-030031预处理可显著抑制肥大细胞活化或PAR2激动剂诱导的机械性超敏反应。总的来说，我们的数据提供了新的证据，即通过PAR2依赖性机制使TRPA1致敏在肥大细胞活化诱导的豚鼠食管迷走神经结状C纤维机械性超敏反应中起重要作用。
