An integrated network pharmacology and metabolomics approach to reveal the immunomodulatory mechanism of Brassica rapa L. (Tibetan Turnip) in fatigue mice

Brassica rapa L. has been widely used as an edible, feeding and medicinal plant in the Qinghai-Tibet Plateau due to its several pharmacological effects of alleviating deficiency or weakness, anti-inflammation, and relieving acute mountain sickness. However, its therapeutic efficacy and the underlying mechanism against fatigue have not been elucidated. The aim of this study is to investigate the action mechanisms of Brassica rapa L. extract (BE) in treating fatigue, with emphasis on the fatigue-related biomarkers, targets and pathways, via network pharmacology and widely targeted metabolomics. Based on the UHPLC-MS results, a total of 33 components were identified and the energy metabolic homeostasis and inflammation related signaling pathways were considered crucial for BE against fatigue by gene functional enrichment analysis. Western blotting (WB) showed that BE significantly up-regulated Nrf2/HO-1, phosphorylation of AMPK, and expression of the downstream signaling pathway, which was further verified by quantitative real-time PCR (q Rt-PCR). The metabolic pathway analysis of BE showed that linoleic acid metabolism was mainly involved, as well as the generation and degradation of ketone bodies, and taurine and hypotaurine metabolism, which are closely related to the regulation of energy metabolism and immunoregulation. Furthermore, the drug-containing serum of BE attenuated intracellular ROS levels in macrophage Raw264.7 cells and reversed the M1 polarization by enhancing the level of IL-10 and Arg-1 and inhibiting that of IL-12 and iNOS in vitro. Hence, Brassica rapa L. has the potential to become a functional food or alternative therapy for fatigue management among immune-compromised people.