Proteomic analysis reveals that Acalypha australis L. mitigates chronic colitis by modulating the FABP4/PPARγ/NF-κB signaling pathway

Ethnopharmacological relevance

Acalypha australis L. (AAL), a traditional medicinal herb from the Euphorbiaceae family, has been widely used in Chinese medicine for its heat-clearing, detoxifying, and diuretic properties, as well as for treating gastrointestinal disorders such as diarrhea and dysentery. Its reported anti-inflammatory and hemostatic effects are closely linked to inflammatory pathways. While previous studies have demonstrated AAL's efficacy in acute colitis, its therapeutic potential in chronic colitis and the underlying mechanisms remain largely unexplored.

Aim of the study

This study aims to investigate the therapeutic efficacy of AAL in dextran sulfate sodium (DSS)-induced chronic colitis and elucidate its anti-inflammatory and barrier-protective mechanisms, with a specific focus on the FABP4/PPARγ/NF-κB signaling pathway.

Materials and methods

The chemical composition of AAL was characterized using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Chronic colitis was induced in mice through three cycles of DSS administration, and the therapeutic effects of AAL were evaluated by assessing body weight, Disease Activity Index (DAI), colon length, and pathological alterations. Enzyme-linked immunosorbent assay (ELISA) was used to quantify inflammatory cytokine levels. Immunohistochemistry and Western blotting were performed to assess mucosal barrier proteins, including Mucin 2 (MUC2), zonula occludens-1 (ZO-1), and Occludin, as well as key signaling proteins such as fatty acid-binding protein 4 (FABP4), peroxisome proliferator-activated receptor gamma (PPARγ), and phosphorylated P65 (p-P65). Proteomic analysis combined with Gene Set Enrichment Analysis (GSEA) was conducted to identify differentially expressed proteins and enriched pathways. The role of the FABP4/PPARγ/NF-κB axis was further validated using the PPARγ antagonist GW9662. Additionally, molecular docking and molecular dynamics simulations were employed to identify bioactive components in AAL and their interactions with FABP4 and PPARγ.

Results

UPLC-QTOF-MS analysis identified 47 compounds in AAL, including flavonoids, terpenoids, and polyphenols. Bergaptol and corilagin were identified as major constituents with potential anti-inflammatory properties. AAL treatment significantly alleviated chronic colitis symptoms, as evidenced by reduced DAI scores, restoration of body weight, and improved colon length. Pathological and immunohistochemical analyses demonstrated that AAL preserved intestinal mucosal integrity by upregulating MUC2, ZO-1, and Occludin expression. Proteomic and GSEA analyses identified the FABP4/PPARγ/NF-κB pathway as a key target of AAL. Western blotting confirmed that AAL suppressed FABP4 expression, enhanced PPARγ levels, and reduced p-P65 expression, indicating inhibition of NF-κB activation. Notably, the therapeutic effects of AAL were abolished by GW9662, further validating the involvement of PPARγ signaling. Molecular docking and molecular dynamics simulations demonstrated strong binding affinities of bergaptol and corilagin to FABP4 and PPARγ, suggesting their role as active compounds responsible for AAL's therapeutic effects.

Conclusions

AAL effectively mitigates chronic colitis by preserving intestinal barrier integrity, suppressing inflammatory responses, and modulating the FABP4/PPARγ/NF-κB pathway. The bioactive compounds bergaptol and corilagin may contribute to these therapeutic effects, highlighting AAL as a promising natural therapeutic agent for ulcerative colitis.