1,8-Cineole Alleviates PA-Induced Lipid Accumulation, Oxidative Stress, and Inflammation via the TLR4/MyD88/NF-κB Signaling Pathway

Objective: The present study investigates the effect of 1,8-cineole on improving lipid metabolism disorder by regulating oxidative stress and inflammation via the TLR4/MyD88/NF-κB pathway. 1,8-Cineole is a monoterpene compound widely found in the essential oils of many plants and has been reported to possess anti-inflammatory and antioxidant activities. However, its role in regulating lipid metabolism disorders remains unclear. This study aimed to investigate the effects of 1,8-cineole on lipid metabolism and explore the potential mechanisms related to oxidative stress and inflammation. Methods: Cell viability was assessed by MTT assay to determine the optimal PA concentration for inducing lipid accumulation and the non-cytotoxic range of 1,8-cineole in HepG2 and AML-12 cells. Lipid droplets were visualized by Oil Red O staining, while triglyceride (TG) and total cholesterol (TC) levels were quantified using enzymatic kits. Oxidative stress markers (ROS by DCFH-DA fluorescence; MDA by TBA method; CAT activity by ammonium molybdate method) and inflammatory cytokines (TNF-α, IL-6, IL-1β, IL-18 by ELISA) were measured. Western blotting analyzed key proteins in the TLR4/MyD88/NF-κB pathway (TLR4, MyD88, p-P65, p-IκBα). Pathway-specific inhibitors were employed for mechanistic validation. Results: 1,8-Cineole (up to 1000 μg/mL) showed no cytotoxicity. It significantly attenuated PA-induced lipid droplet accumulation, reduced TG and TC levels (p< 0.05), and ameliorated oxidative stress by decreasing ROS and MDA while enhancing CAT activity in AML-12 cells (p< 0.01). Furthermore, 1,8-cineole suppressed pro-inflammatory cytokine release (TNF-α, IL-6, and IL-1β;p< 0.01), whereas no significant effect was observed on IL-18 levels. Downregulated TLR4/MyD88/NF-κB pathway activation. Inhibition of TLR4 or NF-κB mirrored these protective effects. Conclusions: 1,8-Cineole alleviates PA-induced lipid metabolism disorders, oxidative stress, and inflammation in hepatocytes, likely through suppression of the TLR4/MyD88/NF-κB signaling pathway.