Tong-Xie-Yao-Fang alleviates diarrhea-predominant irritable bowel syndrome in rats via the GCN2/PERK-eIF2α-ATF4 signaling pathway.

BACKGROUND: Diarrhea-predominant irritable bowel syndrome (IBS-D) is a common functional gastrointestinal disease. Tong-Xie-Yao-Fang (TXYF), the traditional Chinese herbal medicine prescription, is a classic and effective prescription for the treatment of IBS-D, but its mechanism of action is not fully clarified. OBJECTIVE: To evaluate the efficacy of TXYF in the treatment of IBS-D and to explore its potential mechanism of action. METHODS: Changes in the serum levels of 50 free amino acids were targeted for detection by high-performance liquid chromatography (HPLC), and the expression of glucose-regulated protein 78 (GRP78), general control nonderepressible 2 (GCN2), and endoplasmic reticulum-resident kinase (PERK) was detected by immunohistochemistry examinations in healthy volunteers and IBS-D patients. The IBS-D rat was constructed by the three-factor superposition method of neonatal maternal separation, 2,4,6-trinitrobenzene sulfonic acid enema, and chronic unpredictable stress stimulation. The treatment effect of TXYF on IBS-D rats was observed by recording the body weight, grasp force, fecal water content (FWC), and abdominal withdrawal reflex (AWR) of rats before and after treatment. The effects of GCN2/PERK-eukaryotic initiation factor-2 (eIF2α) -activating transcription Factor 4 (ATF4) pathway proteins and gene expression were analyzed by western blotting, reverse transcription-polymerase chain reaction (RT-qPCR), and immunohistochemistry evaluations. RESULTS: Compared with healthy volunteers, IBS-D patients exhibited lower levels of cysteine, γ-aminoacetic acid (GABA), homoproline, and lysine, and immunohistochemistry showed strong activation of GRP78, a marker of endoplasmic reticulum stress. Differential expression of GCN2 and PERK proteins was detected in IBS-D patients and rat colons. In the IBS-D rats, TXYF improved the body weight and grasp force, reduced the FWC, and improved the AWR score. TXYF increased the levels of p-GCN2 and GCN2 and reduced the levels of GRP78, p-PERK, PERK, p-eIF2α, and eIF2α, thereby affecting the expression of the apoptosis-related transcription factors ATF4, CHOP, Caspase-3, and Bcl-2. CONCLUSION: Our study showed that TXYF improved IBS-D by inhibiting apoptosis. The anti-apoptosis effects were potentially mediated by regulating the GCN2/PERK-eIF2a-ATF4 signaling pathway.

The effect of Oren-gedoku-to on experimental colitis in rats.

In Japan and China, Oren-gedoku-to (a complex mixture of ingredients derived from plants) has been used as a herbal medicine in the treatment of inflammatory and ulcerative diseases. In other countries salicylazosulfapyridine has been used to treat inflammatory bowel disease. In this study, we have compared the effect of Oren-gedoku-to with salicylazosulfapyridine on trinitrobenzene-sulphonic acid-induced colonic damage in rats, a model representative of ulcerative colitis and Crohn's disease in man. Oren-gedoku-to was administered orally for one or two weeks over a range of doses. Tissue damage scores, body weight, spleen weight, colon wet weight and colon wall thickness were measured, and colonic tissue levels of interleukin-8 (IL-8), leukotriene B4 (LTB4), prostaglandin E2 (PGE2), and myeloperoxidase activity were examined. The results indicated that Oren-gedoku-to was effective in the treatment of inflammatory bowel disease in the rat model. Histological observation showed a quicker healing process of the lesions, and a reduction of inflammatory cell infiltration following administration of Oren-gedoku-to. The precise mechanism of action for Oren-gedoku-to is still unclear; however, the reduction of IL-8, LTB4, and PGE2 observed suggests that the mechanism may be different from salicylazosulfapyridine (which has no effect on IL-8). There may be a potential benefit in offering combination therapy for the treatment of inflammatory bowel disease.