Submitted on February 23, 2009
Revised on May 1, 2009
Accepted on May 1, 2009
TRPA1 in Mast Cell Activation-induced Long-lasting Mechanical Hypersensitivity of Vagal Afferent C fibers in Guinea Pig Esophagus
Shaoyong Yu1*, Guofeng Gao2, Blaise Z. Peterson2, and Ann Ouyang3
1 Penn State College of Medicine
2 Penn State Hershey College of Medicine
3 Milton S. Hershey Medical Center
* To whom correspondence should be addressed. E-mail: suy13{at}psu.edu.
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 PAR2-mediated pathways sensitizes sensory nerve and induces hyperalgesia. TRPA1 plays an important role in mechano-sensory transduction and nociception. Here we tested hypothesis that mast cell activation via 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. Extra-cellular 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. 91% TRPA1-positive neurons were of small- and medium-diameters, and 80% co-expressed 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 washout, 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 PAR2-dependent mechanism plays an important role in mast cell activation-induced mechanical hypersensitivity of vagal nodose C fibers in guinea pig esophagus.
