Mechanism of Huanglian Houpo Decoction in treatment of ulcerative colitis in mice based on brain-gut axis

Abstract

Based on the brain-gut axis, the present study investigated the effect of Huanglian Houpo Decoction(HLHPD) in the treatment of ulcerative colitis(UC) and explored the mechanism in the regulation of 5-hydroxytryptamine(5-HT), substance P(SP), and vasoactive intestinal peptide(VIP) using modern technologies and molecular docking. Sixty male C57 BL/6 J mice were randomly divided into a blank control group, a model group, a sulfasalazine(SASP) group, and high-(5.00 g·kg~(-1)), medium-(2.50 g·kg~(-1)), and low-dose(1.25 g·kg~(-1)) HLHPD groups. The UC model was induced by oral administration of water containing 3% dextran sulfate sodium salt(DSS) in mice except those in the blank control group. After HLHPD was administered for 10 days, the mice were sacrificed for sample collection. Morphological changes of colon tissues were observed by HE staining. The expression of 5-HT, SP, VIP, tumor necrosis factor α(TNF-α), interleukin-6(IL-6), and interleukin-1β(IL-1β) in the hypothalamus, serum, and colon was determined by the enzyme-linked immunosorbent assay(ELISA). The expression of tryptophan hydroxylase 1(TPH1), SP, and VIP in colon tissues was evaluated by immunohistochemistry. The expression of brain-gut peptide receptors, such as 5-HT3 A, neurokinin receptor 1(NK-1 R), and VIP receptor 1(VPAC1) in colon tissues was investigated by Western blot. The binding affinity of the brain-gut peptide receptors to the main components of HLHPD was analyzed by molecular docking. After HLHPD intervention, UC mice showed increased body weight, reduced DAI score and occult blood, prolonged colon, down-regulated levels of TNF-α, IL-1β, and IL-6 in colon tissues, and relieved pathological damage in the colon. The VIP levels in the colon were significantly up-regulated in the HLHPD groups. The high-and medium-dose HLHPD could significantly down-regulated SP and 5-HT in colon tissues and 5-HT in the serum, and up-regulated the VIP in the serum. The high-dose HLHPD group could down-regulate 5-HT and up-regulate VIP in the hypothalamus. It is suggested that HLHPD can reverse the levels of brain-gut peptides in UC mice to varying degrees. Correlation analysis results suggested that the expression levels of brain-gut peptides in the hypothalamus, serum, and colon tissues were related to inflammatory factors. Molecular docking results showed that berberine, coptisine, and epiberberine were presumedly the material basis for HLHPD in regulating the levels of 5-HT3 A, NK-1 R, and VPAC1. The main components of HLHPD may reduce colonic inflammation and pathological damage of colon tissues by regulating the activity of brain-gut peptides and their receptors, thereby reducing DSS-induced colitis in mice.