Aqueous extracts of Liriope platyphylla induced significant laxative effects on loperamide-induced constipation of SD rats

BACKGROUND Liriope platyphylla has long been reported as a therapeutic drug for treatment of various human chronic diseases including inflammation, diabetes, neurodegenerative disorders, obesity, and atopic dermatitis. To investigate the laxative effects of L. platyphylla, alterations in excretion parameters, histological structure, mucin secretion, and related protein levels were investigated in rats with loperamide (Lop)-induced constipation after treatment with aqueous extract of L. platyphylla (AEtLP). METHODS Alterations on constipation phenotypes were measured in rats with Lop-induced constipation after treatment with AEtLP using excretion parameter analysis, histological analysis, RT-PCR, western blot and transmission electron microscope (TEM) analysis. RESULTS The amounts of stool and urine excretion were significantly higher in the Lop + AEtLP-treated group than in the Lop + vehicle-treated group, whereas food intake and water consumption were maintained at constant levels. AEtLP treatment also induced an increase in villus length, crypt layer, and muscle thickness in the constipation model. Total mucin secretion was higher in the Lop + AEtLP-treated group than in the Lop + vehicle-treated group, although mucin secretion per crypt was very similar among all groups. Furthermore, RT-PCR and western blot revealed a dramatic reduction of key factors level on the muscarinic acetylcholine receptors (mAChRs) signaling pathway in the Lop + AEtLP-treated group relative to the Lop + vehicle-treated group. Especially, the accumulation of lipid droplets in enterocytes of crypts following Lop treatment was improved to the level of the No-treated group in response to AEtLP treatment. CONCLUSION These results suggest that AEtLP improves constipation induced by Lop treatment through an increase in crypt layer and stimulation of lipid droplet secretions. These data are the first to show that the laxative effects of AEtLP are closely related to the down-regulation of mAchRs and their downstream signals.