2.2. Cell Culture and MSU Treatment

THP-1 cells were cultured in RPMI 1640 containing 10% fetal bovine serum, 0.05 mM 2-mercaptoethanol, 100 U/ml penicillin, and 100 μg/ml streptomycin. These were then seeded (1 × 10 ⁵ cells/ml/well) into 6-well culture plates. As described previously, THP-1-derived macrophages (THP-Ms) were obtained by treating the cells with 150 ng/ml PMA for 24 h [22]. Then, after pretreatment with different concentrations of cichoric acid (30 μg/ml, 100 μg/ml, and 300 μg/ml), THP-Ms were subjected to MSU suspension (1.0 mg/ml) for 24 h. The supernatants were used to detect the cytokine levels. ELISA, as per the manufacturer's guidelines, was used to determine the levels of IL-1β, TNF-α, PGE2, and cAMP. The activity of PKA (protein kinase A) was determined using a multifunctional enzyme marker.