Study on the Anti-inflammatory Mechanism of Liubao Tea Theabrownins Against Intestinal Inflammation Based on NF-κB Pathway Regulation

Objective To investigate the protective effects of Liubao tea theabrownin (LTB) against lipopolysaccharide (LPS)-induced inflammatory responses in intestinal epithelial cells and to elucidate the underlying molecular mechanisms. Methods LTB was prepared using hot water extraction, and its chemical composition was profiled through untargeted metabolomics analysis. An inflammatory model was established using LPS-induced Caco-2 cells. Cell viability was assessed using the Cell Counting Kit-8 (CCK-8) assay. Levels of inflammatory cytokines and enzymes were measured by enzyme-linked immunosorbent assay (ELISA), while nitric oxide (NO) content was determined using the Griess assay. Intracellular reactive oxygen species (ROS) levels were detected using the DCFH-DA fluorescent probe. Intestinal barrier function was evaluated by measuring transepithelial electrical resistance (TEER). The expression of relevant genes and proteins was quantified using quantitative real-time PCR (qPCR) and Western blot, respectively. Nuclear translocation of NF-κB p65 was observed via immunofluorescence. Results Untargeted metabolomics analysis revealed that LTB is composed of diverse bioactive constituents, primarily shikimates and phenylpropanoids (21.01%), fatty acids (15.75%), and terpenoids (11.82%). LTB significantly inhibited the LPS-induced secretion of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8), as well as the excessive production of NO. Concurrently, it upregulated the expression of the anti-inflammatory cytokine interleukin-10 (IL-10) (P < 0.01). Furthermore, LTB effectively reduced intracellular ROS levels, enhanced the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), decreased malondialdehyde (MDA) production, and upregulated the gene expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and NAD(P)H quinone dehydrogenase 1 (NQO1) (P<0.05). LTB also restored TEER values in a dose-dependent manner and upregulated the gene expression of Claudin-1, Occludin, and Zonula Occludens-1 (ZO-1), thereby preserving intestinal barrier integrity. Crucially, LTB significantly inhibited the nuclear translocation and phosphorylation of the nuclear factor-kappa B p65 subunit (NF-κB p65) and downregulated the protein expression of Toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) (P<0.05). Conclusion: Liubao tea theabrownin exerts comprehensive anti-inflammatory, antioxidant, and intestinal barrier-protective effects by modulating the TLR4/MyD88/NF-κB signaling pathway and activating the Nrf2 antioxidant pathway. These findings provide a scientific basis for the development of LTB-based therapeutic agents for the prevention and treatment of intestinal inflammation.