Integrative Lipid Pseudotargeted Metabolomics and Amino Acids Targeted Metabolomics Unravel the Therapeutic Mechanism of Rhizoma Paridis Saponins on Experimental Colitis of Damp-Heat Type

Purpose: Inflammatory bowel disease (IBD) is a serious disease that affects the metabolism and inflammatory responses of human beings. From the perspective of traditional Chinese medicine, damp-heat syndrome is one of the main syndromes of IBD. Rhizoma Paridis, also known as the root of Paris polyphylla, a well-known herbal medicine used in China, is used to treat IBD with damp-heat syndrome (IBD-DH). However, uncertainty still exists regarding the underlying mechanisms and the impact of Rhizoma Paridis on IBD-DH.

Methods: The rats in the model (DAT) and medication administration (Rhizoma Paridis total saponins (RPTS) and Pennogenin (PN)) groups were given a high temperature and high humidity environment, high fat and high sugar diet combined with 2,4,6-trinitrobenzene sulfonic acid (TNBS) to establish the model of experimental colitis of damp-heat type, and the normal control group (RNC) rats were given a normal diet at normal temperature and humidity. Damp-heat control group (DNC) was set with the same condition as DAT without TNBS. Hematoxylin-Eosin (HE) staining was used to observe the histopathological morphology of the rat colorectum. The expression of the metabolism-related genes (Phospholipase A2 (sPLA2, cPLA2), and phosphatidylethanolamine N-methyltransferase (PEMT)) was assessed by using real-time quantitative PCR analysis (RT-qPCR). And the levels of the metabolism-related proteins (sPLA2, cPLA2), S100A8/9, Arg-1, and cytokines were detected by enzyme-linked immunosorbent assay (ELISA) kit. To investigate lipids and amino acids which closely associated with the IBD and IBD-DH, lipid pseudotargeted metabolomics with UHPLC-TQ/MS analysis method, as well as targeted quantitative amino acid analysis were performed.

Results: Our data showed that RPTS (50 mg/kg) and PN (20 mg/kg) significantly ameliorated the severity of TNBS-induced colitis and downregulated the levels of circulating proinflammatory cytokines. Compared with RNC group, lipid pseudotargeted metabolomics demonstrated that glycerophospholipids, sphingolipids, carnitine, and glycerolipids were the four most perturbed lipid classes, and amino acids targeted metabolomics demonstrated that serine, N-acetylneuraminic acid, histidine, proline, taurine, and kynurenine changed significantly in DAT group . Correlation analyses showed tight associations between most of differential metabolites and proinflammatory cytokines. RPTS and PN both regulated glycerophospholipid metabolism and sphingolipid metabolism. However, both of them did not have a significant effect on amino acid modulation. RPTS and PN potentially regulated sPLA2, cPLA2, and PEMT.

Conclusion: These results showed that RPTS (50 mg/kg) and PN (20 mg/kg) effectively alleviated rats' colitis of damp-heat type, affected cytokines, and altered lipid metabolism without significant modulation on amino acid metabolism.