Search for an Effective Drug for Refractory GERD Using an Originally Developed Duodenogastroesophageal Reflux Animal Model

Abstract

Background: Antisecretory drugs, especially proton pump inhibitors (PPIs), are the preferred treatment agents for patients with gastroesophageal reflux disease (GERD). However, refractory GERD, which can manifest as an incomplete response or a complete lack of response to PPI therapy, is very common. Despite administering PPIs for symptom control, duodenogastroesophageal reflux (DGER) containing bile is controlled in only one-third of patients. To identify an effective drug for refractory GERD, especially for DGER, we administered a traditional Japanese herbal medicine rikkunshito, which has a prokinetic action on gastric emptying, to an originally established rat model for GERD that does not respond to PPIs. Materials and Methods: Eight-week-old male Wistar rats were used in this study. We artificially induced the flow of DGER through the stoma of an esophago-glandular stomach anastomosis after removal of the forestomach. We classified the surviving animals into 1 sham-operated group, 3 rikkunshito groups [0% (control group), 0.3%, and 0.6%], and 4 omeprazole (OPZ) groups [0 (control), 10, 30, and 100 mg/kg]. Resected esophagi were divided into two sections: one for analyses of mRNA levels of COX-2, interleukin (IL)6, IL-1beta, and tumor necrosis factor-alpha (TNF-alpha) and the other for histological examination. Histological examination was performed after hematoxylin and eosin staining, and Ki67(MIB5) was used for immunohistochemical analysis. Results: Esophagitis, hyperplasia, and regenerative atypia were detected in all rats with reflux operation. However, the degree of these lesions was much milder in the 0.3% and 0.6% rikkunshito groups than in the rikkunshito control and OPZ groups (10, 30, and 100 mg/kg). The mRNA levels of IL6 and TNF-alpha were significantly lower in the 0.3% and 0.6% rikkunshito groups than in the rikkunshito control group (Dunnett's test, p < 0.05). The mRNA levels of COX-2 and IL-1beta tended to be lower in the 0.3% and 0.6% rikkunshito groups than in the rikkunshito control group. On the other hand, all doses of OPZ failed to inhibit the expression of mRNA encoding the inflammatory mediators. Moreover, the Ki67 index was significantly lower in the 0.3% and 0.6% rikkunshito groups than in the rikkunshito control group and all OPZ groups. Discussion: Rikkunshito decreased the mRNA levels of inflammatory mediators in the esophageal mucosa and improved the degree of reflux esophagitis in the animal reflux model. In the preliminary study, we are getting a result that rikkunshito play a role in the binding of bile acids. Because rikkunshito not only has a prokinetic action on gastric emptying but also reduces the exposure of esophageal mucosa to bile acids, it might be an effective drug for the treatment of refractory GERD associated with DGER.