HCl-activated neural and epithelial vanilloid receptors (TRPV1) in cat esophageal mucosa

Abstract

To test whether transient receptor potential channel vanilloid subfamily member-1 (TRPV1) mediates acid-induced inflammation in the esophagus, a tubular segment of esophageal mucosa was tied at both ends, forming a sac. The sac was filled with 0.01 N HCl (or Krebs buffer for control) and kept in oxygenated Krebs buffer at 37°C. The medium around the sac (supernatant) was collected after 3 h. Supernatant of the HCl-filled sac abolished contraction of esophageal circular muscle strips in response to electric field stimulation. Contraction was similarly abolished by supernatant of mucosal sac filled with the TRPV1 agonist capsaicin (10 Ϫ6 M). These effects were reversed by the selective TRPV1 antagonist 5Ј-iodoresiniferatoxin (IRTX) and by the plateletactivating factor (PAF) receptor antagonist CV9388. Substance P and CGRP levels in mucosa and in supernatant increased in response to HCl, and these increases were abolished by IRTX and by tetrodotoxin (TTX) but not affected by CV9388, indicating that substance P and CGRP are neurally released and PAF independent. In contrast, the increase in PAF was blocked by IRTX but not by TTX. Presence of TRPV1 receptor was confirmed by RT-PCR and by Western blot analysis in whole mucosa and in esophageal epithelial cells enzymatically isolated and sorted by flow cytometry or immunoprecipitated with cytokeratin antibodies. In epithelial cells PAF increased in response to HCl, and the increase was abolished by IRTX. We conclude that HCl-induced activation of TRPV1 receptors in esophageal mucosa causes release of substance P and CGRP from neurons and release of PAF from epithelial cells. smooth muscle; signal transduction; platelet-activating factor TRANSIENT RECEPTOR POTENTIAL channel vanilloid subfamily member-1 (TRPV1, also known as VR1) was originally described in primary sensory neurons as a receptor for capsaicin and related natural irritants (collectively referred to as vanilloids) (61). TRPV1 is a nonselective cation channel expressed by several cell types including sensory nerves. It is activated by heat, by the pungent ingredient of chili peppers, capsaicin, or by endogenous hydrogen ions released in tissues during inflammation (61) or present in gastric reflux. TRPV1 is now believed to function as a molecular integrator of noxious stimuli, including acids, heat, pollutants with negative electric charge, and endogenous proinflammatory substances (23). TRPV1 activation in primary afferent neurons evokes the sensation of burning pain and induces neurogenic inflammation by the release of substance P and calcitonin gene-related peptide (CGRP) (65, 66). Upregulated TRPV1 expression has been demonstrated in disease states such as inflammatory bowel disease (66) and irritable bowel syndrome (15) and, more recently, in esophageal submucosal neurons of esophagitis patients (5, 41).TRPV1-associated "neurogenic inflammation" has been examined in several systems, particularly in the airways, and to a lesser extent in the digestive tract. In the digestive tract most publications have ...

TRP channels in neurogastroenterology: opportunities for therapeutic intervention

“…In keeping with this hypothesis, intra-esophageal capsaicin installation was found to induce symptoms of heartburn and chest pain in healthy volunteers (Kindt et al, 2009). The proposed role of TRPV1 is further supported by a recent study showing that acid-induced activation of TRPV1 receptors in feline esophageal mucosa results in substance P and CGRP release, presumably arising from submucous neurons, together with the release of platelet activating factor from esophageal epithelial cells, which also turned out to express TRPV1 (Cheng et al, 2009). The release of proinflammatory mediators via TRPV1 activation probably also plays a role in acid-induced esophagitis because TRPV1 null mice develop less severe esophagitis compared with wild-type mice (Fujino et al, 2006).…”

ATP: a mediator for HCl-induced TRPV1 activation in esophageal mucosa

“…We demonstrated that, in these cells, PAF production is directly linked to TRPV1 activation, resulting in increased intracellular Ca 2ϩ , activation of a p38-dependent transduction pathway, and production of PAF (27). The production of SP and CGRP in the mucosa, however, was not affected by the PAF receptor antagonist CV-3988, indicating that production of SP and CGRP by submucosal neurons does not depend on PAF release from epithelial cells (14).…”

“…We demonstrated that, in these cells, PAF production is directly linked to TRPV1 activation, resulting in increased intracellular Ca 2ϩ , activation of a p38-dependent transduction pathway, and production of PAF (27). The production of SP and CGRP in the mucosa, however, was not affected by the PAF receptor antagonist CV-3988, indicating that production of SP and CGRP by submucosal neurons does not depend on PAF release from epithelial cells (14).ATP is a neurotransmitter in the central and peripheral nervous systems and is also involved in peripheral inflammation and transmission of the sensation of pain (2). Recently, the regulated release of ATP from nonneuronal sources has been shown to play a role in the activation of sensory nerve terminals (2).…”

Transient Receptor Potential Vanilloid 1 in animal tissues: An overview to highlight similarities and differences with human species

“…Moreover, this study demonstrated the activation of TRPV1 by HCl and its enrolment in acid-induced inflammation and contraction of this organ. Capsaicin inhibits the contractions while 5-I-RTX had the opposite effect [33] . The results showed that TRPV1 HCl-induced activation in oesophageal mucosa induce the release of substance P and CGRP release from neurons and PAF release from epithelial cells [33] .…”

“…The study of Cheng et al [33] , identified the presence of TRPV1 in oesophageal mucosa in cats. Moreover, this study demonstrated the activation of TRPV1 by HCl and its enrolment in acid-induced inflammation and contraction of this organ.…”