Liangfu Pill Alleviates Constipation-Predominant Irritable Bowel Syndrome through Modulation of 5-HT Signaling Pathway and Gut Microbiota.

OBJECTIVE

To elucidate the modulation mechanism of Liangfu Pill (LFP) on serotonin (5-HT) signaling pathway and gut microbiota in constipation-predominant irritable bowel syndrome (IBS-C) rat models to clarify its therapeutic effects.

METHODS

The major metabolites of LFP were analyzed, and network analysis was used to predict the potential mechanism of LFP on IBS-C. Sixty SD rats were allocated to normal, normal + LFP (N+LFP), model, moxapride, low- and high-dose LFP (LFP-L and LFP-H) groups. IBS-C model was developed by tail-clamping stress, irregular feeding, and ice-water gavage for 14 d. Following 7-d intervention, levels of substance P (SP), vasoactive intestinal peptide (VIP), and melatonin (MLT) in the colon tissues were quantified using ELISA, while high-performance liquid chromatography was used to measure the concentration of 5-HT in colon tissue. The expressions of serotonin transporter (SERT), tryptophan hydroxylase 1 (TPH1), and serotonin 4 receptor (5-HT4R) proteins were assessed using Western blot. The open-field test was performed on day 14 and day 21 to evaluate rats' locomotor activity. Additionally, the structure of rat intestinal microbiota was analyzed by 16S rDNA high-throughput sequencing technology.

RESULTS

Chromatographic analysis identified 104 major metabolites in LFP. Network analysis predicted that the main signaling pathways involved serotonergic synapses and regulation of transient receptor potential channels by inflammatory mediators. In rats with IBS-C, LFP increased body weight gain, open-field total distance and average speed, fecal count, Bristol stool score, and the levels of SP and VIP, while decreasing abdominal withdrawal reflex scores and 5-HT level (P<0.05 or P<0.01). The protein expressions of SERT and 5-HT4R were upregulated (P<0.05 or P<0.01), whereas TPH1 expression was downregulated (P<0.01). Additionally, LFP improved gut microbiota composition, with increased Chao, abundance-based coverage estimator, Shannon indices (P<0.05 or P<0.01) and relative abundance of differential microbial taxa.

CONCLUSIONS

LFP alleviates IBS-C symptoms, improves overall condition and especially reduces visceral sensitivity in rats. The potential mechanism may involve modulation of 5-HT signaling pathway and gut microbiota.