Envolvimento do receptor TRPV1 em um novo modelo de doença do refluxo não erosiva (NERD): da inflamação ao defeito funcional

Abstract

Non-erosive reflux disease (NERD) affects about 70% of patients with reflux symptoms. These patients do not present erosions in the esophageal mucosa at endoscopy, but exhibit impaired epithelial integrity and increased expression of transient receptor potential vanilloid 1 (TRPV1). In addition, chloridric acid (HCl) activates TRPV1 with release of inflammatory mediators. However, there is no experimental model of NERD and the role of TRPV1 receptor in this disease is unknown. Aim: To standardize an experimental model of NERD in mice and investigate the role of TRPV1 receptor in inflammation and impairment of esophageal epithelial barrier. Methods: NERD was induced surgically in Swiss mice (30-35g, Ethics Committee: 104/14) by stenosis pyloric and gastric fundus ligation. The control group was Sham (operated false). The animals were sacrificed 1, 3, 7 and 14 days post-surgery. Another design consisted of animals sacrificed on the 7th day; Group I: Sham, II: NERD, III: Omeprazole (a PPI: 40 mg/kg, i.p.), IV and V: SB366791 and capsazepine (TRPV1 antagonists: 5 mg/kg, i.p.) and VI: resiniferatoxin (RTX, to deplete TRPV1: for 3 days, 30 μg/kg, 70 μg/kg and 100 μg/kg, s.c.). Survival and body weight were monitored daily, were also analyzed the wet weight, macroscopy, histology, myeloperoxidase (MPO) and cytokines in the esophagus. Transepithelial electrical resistance (TEER) was evaluated with exposure to pH 1.0 or 0.5 containing pepsin (1 mg/ml) and taurodeoxycholic acid (TDCA: 2 mM) and the permeability without acid exposure. Results: The survival rate was 78% at 14 day, with a mild loss in body weight. Surgery did not induce erosive esophagitis (EE), but induced microscopic inflammation, increased wet weight, IL-6 and KC levels and MPO activity in the esophagus, with peak between 3 and 7 days and resolution 14 days post-surgery. Sham intervention did not cause esophageal inflammation. The impairment of the esophageal epithelial barrier was evaluated using the Ussing chamber technique, on 7 and 14 days post-surgery, and was observed decrease TEER and increase permeability in NERD animals, compared to the Sham group. The model on day 7 was selected for the following experiments. Inhibition of acid secretion with omeprazole, pharmacological blockade with capsazepine and SB366791, and depletion of TRPV1 with RTX prevented esophageal inflammation, decrease TEER, and increase permeability, compared to the NERD animals. Conclusion: A novel model of NERD in mice was implemented and validated, and we demonstrated that the TRPV1 receptor plays a critical role in esophageal inflammation, and is involved in the acid-induced impairment epithelial barrier, which contributes to the understanding of the pathophysiology of NERD.