Effect of Japanese Kampo Daikenchuto on chronic TNBS-induced colitis by up-regulation of CGRP, adrenomedullin and their receptor components expressions in rat colon

Abstract

Daikenchuto (DKT) is a traditional Japanese herbal medicine which has been used as the treatment of paralytic ileus by increase gastrointestinal motility through an up-regulation of the calcitonin gene-related peptide (CGRP). CGRP is also the most powerful vasoactive substance. Recently, we have demonstrated that DKT increased the colonic blood flow, an effect mediated by CGRP, adrenomedullin (ADM) and their receptors in normal rat. Tissue CGRP and ADM are decreased in human and experimental Crohn's disease, and have also been reported as protective and therapeutic peptides in experimental Crohn's disease. In the present study, we examined the therapeutic effect of DKT, as an inducer of tissue CGRP, ADM and their receptors, in 2,4,6,-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Rectal enemas of TNBS in ethanol were given to SD rats, and then the animals were given oral DKT (100mg/kg) daily for 3 wks. Three weeks after colitis induction, all animals were killed and colonic damage was evaluated macroscopically, histologically and biochemistry. The colonic myeloperoxidase (MPO) activity was evaluated. RT-PCR was employed the detection of mRNA of CGRP, ADM, calcitonin receptor-like receptor (CRLR), receptor-activity modifying protein 1 (RAMP1), the component of CGRP 1 receptor and RAMP2, RAMP3, the component of ADM receptor. Treatment with DKT attenuated colonic inflammation, improving rat weight, damage score, colonic weight-to-length ratio, the total area of ulceration and MPO activity. RT-PCR showed that mRNAs for CGRP, ADM, CRLR, RAMP1, RAMP2 and RAMP3 were up-regulated by DKT in TNBS-treated colon extracts, compared with the control group without DKT treatment. These results suggest that DKT has therapeutic effects on TNBS-induced colitis via up-regulation of tissue CGRP, ADM and their receptor components (CRLR, RAMP1, RAMP2 and RAMP3), therefore, DKT may have potential therapeutic utility in patients with Crohn's disease.