Metabolomics-based analysis of the interventional effects of peroxydehydrotumulosic acid in Poria cocos on airway inflammation in asthma

The study aims to investigate the interventional effect of peroxydehydrotumulosic acid (PHA) in Poria cocos on allergic asthma mice, and to investigate its mechanism of action based on metabolomics. Male BALB/c mice were randomly divided into normal group (CON), model group (M), positive drug montelukastna group (Y, 1.3 mg·kg^-1), PHA low-dose group (PHA-L, 15 mg·kg^-1), and PHA high-dose group (PHA-H, 30 mg·kg^-1). The mouse model of allergic asthma was established by intraperitoneal injection of ovalbumin (OVA) and aluminium hydroxide adjuvant for sensitisation and OVA nebulisation for excitation. The corresponding drugs were given by gavage 30 min before modelling, and the drugs were administered for 7 consecutive days. 24 h after the last administration of the drugs, the mice were tested for cough and asthma indexes, lung function and lung coefficient, the mice were stained with hematoxylin-eosin (HE) to observe the pathological changes of the lung histology, and the mice were stained with Masson to observe the level of collagen fibre deposition, and the levels of inflammatory factors in the serum and alveolar lavage fluid of the mice were measured by enzyme-linked immunosorbent assay (ELISA) and flow cytometry to determine the levels of inflammatory factors in the mice. Apoptotic cell levels in lung tissue and Th17 and Tregs cell levels in blood were detected by flow cytometry, and small molecule metabolites were analysed by liquid-liquid mass spectrometry (LC-MS) in serum samples of mice of different treatment groups. The metabolic pathway enrichment analysis was used to investigate the biometabolic pathways involved in the characterised metabolites. The results indicated a comparison with group M, PHA significantly improved lung function, reduced lung coefficient, attenuated lung histopathological damage and collagen fibre deposition, significantly down-regulated the levels of interleukin 4 (IL4), immunoglobulin E (IgE), interleukin 17A (IL17A) in blood and tumor necrosis factor-α (TNF-α) in alveolar lavage fluid, inhibited apoptosis and the generation of Th17 cells, and increased the level of Tregs cells in lung tissue. Metabolomics analysis of endogenous substances in the M and PHA groups separated significantly, and 63 differential metabolites were screened, mainly involving arachidonic acid metabolism, retinol metabolism, biosynthesis of phenylalanine, tryptophan, and tyrosine, glycerophospholipid metabolism, and tyrosine metabolism. PHA can improve the pathological state of mice with asthma by inhibiting the production of inflammatory factors IL4 and IL17A, hindering the recruitment of inflammatory cells, and regulating some differential metabolites and metabolic pathway disorders. The animal experiment was approved and supervised by the Animal Ethics Committee of Henan University of Traditional Chinese Medicine (ethics number: DWLL2018080003).