ETHNOPHARMACOLOGICAL RELEVANCE:Platycodon grandiflorum and Lonicera japonica are two plants that have been widely used in traditional ethnic medicine for both medicinal and edible purposes. They are commonly applied in the prevention and treatment of lung-heat-related and inflammatory diseases. However, the stems and leaves of these plants have historically been regarded as by-products, and their therapeutic potential has not been thoroughly explored. Recent studies have shown that the Platycodon grandiflorum stems and leaves, and Lonicera japonica stems and leaves are rich in bioactive compounds, including flavonoids, saponins and phenolic compounds and exhibit notable anti-inflammatory and antioxidant activities. In this study, we investigate the protective mechanism of Platycodon grandiflorum stems and leaves and Lonicera japonica stems and leaves (PLSL) against lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. This work aims to provide a theoretical basis for resource development and the sustainable, high-value utilization of non-medicinal parts of traditional Chinese medicinal plants.
METHODS:In this study, an LPS-induced inflammatory model using RAW264.7 cells was employed to screen the optimal compatible ratio of PLSL. High-performance liquid chromatography (HPLC) was used to analyze its chemical composition and identify the main active components. In the animal experiment, a mouse model of ALI was established by intranasal instillation of LPS. The severity of lung injury was comprehensively evaluated based on the lung index, lung wet-to-dry (W/D) weight ratio, hematoxylin and eosin staining and Masson's staining. Levels of inflammatory cytokines, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured using ELISA. The transcriptional levels of genes related to the Keap1/Nrf2 pathway were detected by quantitative real-time polymerase chain reaction (qRT-PCR), and the expression and nuclear translocation of Nrf2 and p65 proteins were assessed by immunofluorescence. Meanwhile, 16S rRNA high-throughput sequencing was applied to analyze the cecal microbiota composition in mice, and gas chromatography was used to determine short-chain fatty acid (SCFA) concentrations. Spearman correlation analysis was performed to explore correlations among inflammatory mediators, antioxidant markers and gut microbiota at the genus level.
RESULTS:The in vitro results demonstrated that the 4:1 combination of PLSL promoted the migration and proliferation of RAW264.7 cells in a dose-dependent manner and effectively inhibited the overexpression of pro-inflammatory mediators, including cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as inflammatory cytokines such as TNF-α, IL-6 and IL-1β. Meanwhile, PLSL exhibited strong scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) cation radicals and hydroxyl radicals (·OH). HPLC analysis revealed that PLSL contained key active components, including platycodin D, lobetyolin, loganin and chlorogenic acid. In vivo experiments confirmed that PLSL significantly alleviated LPS-induced ALI in mice by regulating the NF-κB and Keap1/Nrf2 signaling pathways, reducing malondialdehyde (MDA) and nitric oxide (NO) levels, increasing glutathione (GSH) levels, suppressing the expression of COX-2, iNOS, TNF-α, IL-6 and IL-1β and modulating the mRNA expression of Keap1, Nrf2, heme oxygenase-1(HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Furthermore, PLSL effectively improved intestinal microbial diversity, increased the relative abundance of beneficial bacteria, including Lachnospiraceae and Alistipes, and significantly elevated cecal short-chain fatty acids (SCFAs), such as acetic acid, propionic acid and butyric acid.
CONCLUSIONS:This study preliminarily elucidates the multi-target synergistic anti-inflammatory effects of PLSL from the perspectives of inflammatory signaling pathways and gut microbiota. It provides experimental evidence for the whole-plant development and utilization of Platycodon grandiflorum and Lonicera japonica as ethnomedicines.