Metabolomics of the anti-inflammatory effect of Pueraria lobata and Pueraria lobata var. Thomsonii in rats

Pueraria lobata (Willd.) Ohwi and Pueraria lobata var. Thomsonii (Benth.) Maesen are essential medicinal and edible homologous plants widely cultivated in Asian countries. Therefore, P. lobata and P. thomsonii are widely used in the food, health products and pharmaceutical industries and have significant domestic and international market potential and research value. P. lobata and P. thomsonii have pharmacological effects in the clinic, such as antipyretic, analgesic, anti-inflammatory and antioxidant effects. These plants are commonly used in the treatment of inflammatory diseases and other related diseases. However, the potential mechanisms of the anti-inflammatory effects of P. lobata and P. thomsonii have not been elucidated. This study aimed to confirm the anti-inflammatory effects of P. lobata and P. thomsonii on inflammatory model diseases and to investigate the mechanism of their anti-inflammatory effects from the perspective of plasma metabolomics. First, P. lobata and P. thomsonii were identified by high‒performance liquid chromatography (HPLC). Second, we established the following three inflammation models: an acute inflammation model of auricular swelling in mice induced by xylene, an acute inflammation model of foot swelling in rats induced by carrageenan gum, and a chronic inflammation model of cotton ball granuloma in rats. Then we examined the weight and swelling rate of auricular swelling in mice; the residence time, contact area, and mean contact pressure in rats on the gait meter; and the weight of granulomas in rats and the content of IL-1β and TNF-α in plasma to investigate the anti-inflammatory pharmacodynamics of P. lobata and P. thomsonii. Third, we used LC‒MS‒based plasma metabolomics techniques to obtain potential biomarkers of P. lobata and P. thomsonii related to inflammation. Then, the potential biomarkers were enriched by MetaboAnalyst and KEGG metabolomics analysis tools to obtain metabolic pathways related to inflammation. Finally, we tested the indicators of COX-2, 5-LOX, GSH, GSSG and γ⁃GCL in rat plasma from the granuloma model by enzyme-linked immunosorbent assays (ELISAs) to verify the inflammation-related metabolic pathway. The experimental results showed that P. lobata and P. thomsonii could reduce the swollen weight and swelling rate of the auricle in mice, and could increase the residence time, contact area and mean contact pressure in rats on the gait meter. Moreover, P. lobata and P. thomsonii could inhibit the growth of granulomas and reduce the content of IL-1β and TNF-α in plasma in rats. The above results preliminarily verified that P. lobata and P. thomsonii have different anti-inflammatory effects. We identified eighteen plasma biomarkers associated with P. lobata and sixteen plasma biomarkers related to P. thomsonii in regulating inflammation by a plasma metabolomics analysis. The following two major metabolic pathways were further screened and enriched: arachidonic acid metabolism and glutathione metabolism. Then we noted that P. lobata and P. thomsonii could reduce the COX-2, 5-LOX and GSSG levels and increase the GSH, GSH/GSSG and γ⁃GCL levels based on the ELISA results, which demonstrated that P. lobata and P. thomsonii affect the anti-inflammatory mechanism through arachidonic acid metabolism and glutathione metabolism. The results of this study further elucidate the anti-inflammatory mechanism of action of P. lobata and P. thomsonii, providing a scientific basis for developing new drugs for the treatment of inflammation-related diseases and laying a foundation for the development of herbal resources, such as P. lobata and P. thomsonii.