A neutral polysaccharide from Persicaria hydropiper (L.) Spach ameliorates lipopolysaccharide-induced intestinal barrier injury via regulating the gut microbiota and modulating AKT/PI3K/mTOR and MAPK signaling pathways

Ethnopharmacological relevance: Persicaria hydropiper (L.) Spach, a herb that is prevalent across Asia and Europe, finds utility as both a culinary ingredient and medicinal herb. In China, P. hydropiper decoction is commonly employed to alleviate dysentery, gastroenteritis, and diarrhea symptoms. Aim of the study: To assess the effects of a neutral polysaccharide from P. hydropiper (PHP) on the intestinal barrier (IB) injury induced by lipopolysaccharide (LPS) in mice, and elucidate the molecular mechanisms involved. Materials and methods: PHP was extracted from dried P. hydropiper herb using hot water extraction, followed by ethanol precipitation. The extract underwent successive isolation and purification steps involving anion -exchange and gel filtration chromatography. The primary structure of PHP was determined using Fourier -transformed infrared spectroscopy, ion chromatography, gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) spectroscopy. Male BALB/c mice were randomly assigned to control (CON), model (MOD), berberine hydrochloride (BBR), and PHP (20, 40 and 80 mg/kg) groups. Histopathological changes in jejunal tissues were assessed through hematoxylin and eosin (HE) staining. The expression levels of proteins and genes involved in AKT/PI3K/mTOR and MAPK signaling pathways were evaluated using qRT-PCR and Western blotting, respectively. The composition and abundance of the gut microbiota in mice were analyzed using high-throughput 16S rRNA gene sequencing. Additionally, the concentrations of short-chain fatty acids (SCFAs) were determined using GC-MS. Results: The main components of PHP included arabinose, galactose, and glucose (molar ratio = 1.00:5.52:11.39). The backbone of PHP consisted of-*4)-Glcp-(1-*,-*4,6)-Glcp-(1-*,-*4)-Galp-(1-*, -*4,6)-Galp-(1-*. The branched chains primarily consisted of 5)-Araf-(1-* residues, which were attached to the back-bone through-*6)-Glcp-(1-* and-*6)-Galp-(1-* at the 6-position. Histological analysis demonstrated that PHP exhibited a mitigating effect on intestinal damage induced by LPS. PHP could markedly reduce the mRNA levels of PI3K, AKT, mTOR, p70 S6K, Ras, Raf1, MEK1/2, p38, ERK1/2, and JNK, while downregulating the protein levels of p-mTOR, p-PI3K, p-AKT, p-p38, p-ERK, and p-JNK. PHP also modulated the diversities and abundances of the gut microbiota, resulting in an increase in the abundances of Lactobacillaceae, Anaerovoracaceae, Lach-nospiraceae, Eggerthellaceae, and Desulfovibrionaceae and a decrease in the abundances of Muribaculaceae, Pre-votellaceae, and Rikenellaceae. Additionally, PHP significantly increased the content of various SCFAs. Conclusion: PHP emerges as a pivotal factor in the repair of IB injury by virtue of its ability to regulate the gut microbiota, elevate SCFA levels, and inhibit the MAPK and AKT/PI3K/mTOR pathways. It is worth noting that the therapeutic effect of high-dose PHP was remarkably significant, surpassing even the positive control of berberine hydrochloride.