Sa1730 Several Active Ingredients Synergistically Contribute to the Analgesic Effects of Hangeshashinto in Ulcerative Oral Mucositis

Abstract

Background: Ulcerative oral mucositis is frequently observed in cancer patients undergoing chemoradiotherapy; it induces intractable, severe pain during meals and leads to a deterioration of the patient's quality of life. Recently, hangeshashinto (HST), a traditional Japanese medicine consisting of seven crude herbal drugs, has been reported to alleviate gastric cancer chemotherapy-induced oral mucositis in a randomized, double-blind, placebo-controlled clinical trial. In this study, we investigated the efficacy of HST on oral ulcer (OU)-induced mucosal pain in rats using a new behavioral technique, the stable intraoral opening (SIO) method. Methods: A piece of filter paper was soaked in a 50%-acetic acid solution and placed in the labial fornix region of the inferior incisors of anesthetized rats for 30 seconds. OU-induced mucosal pain was evaluated using the SIO method that enables measurement of intraoral mechanical pain threshold in conscious rats by stimulation to the exposed oral mucosa with von Frey filaments. The effects of HST, the extract of crude drugs or ingredients contained in HST after application on the OU region of the OU model, were evaluated using the SIO method. Tissue penetration in the OU was examined by application of a retrograde tracer fluorogold. For possible target evaluation for analgesic effects, the typical 21 ingredients contained in HST were screened by measurement of channel currents or intracellular calcium concentrations in human Nav1.8, TRPV1, or TRPA1-expressing CHO or HEK293 cells. Results: Treatment with acetic acid caused obvious ulcers in the labial fornix region, characterized by severe infiltration of inflammatory cells and epidermolysis. Mechanical threshold in the ulcerated oral mucosa was significantly reduced compared to that of the vehicle-treated mucosa. HST recovered the mechanical threshold reduction to naive levels, beginning at 30 m following topical application until 2 h. In the ion channel screening, (6)shogaol and (6)-gingerol in Ginger and isoliquiritigenin in Licorice demonstrated a strong antagonistic effect on Nav1.8 activation. The analgesic effects of isoliquiritigenin and (6)shogaol/(6)-gingerol were slower and/or weaker than that of HST, while they were enhanced by the co-application of a Ginseng extract, containing abundant surfactant saponins, which showed acceleration of tissue penetration in the ulcer region. Conclusions: Mechanical allodynia develops in the OU of acetic acid-treated rats. Direct application of HST in the early stages ameliorates OU-induced mechanical allodynia, and several active ingredients, such as isoliquiritigenin, (6)-shogaol and (6)-gingerol with saponins, may synergistically contribute to the analgesic effects of HST. These results suggest that HST is a useful drug for ameliorating OU-induced pain in patients undergoing chemoradiotherapy.