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

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.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.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.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 backbone 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, Lachnospiraceae, Eggerthellaceae, and Desulfovibrionaceae and a decrease in the abundances of Muribaculaceae, Prevotellaceae, and Rikenellaceae. Additionally, PHP significantly increased the content of various SCFAs.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.