Fig. 6.

Induction of IL-1b in THP-1 cells by coculture with cholesterol crystal–containing HepG2 cells or by direct exposure to synthetic cholesterol crystals. A–B: HepG2 cells exposed to 200 µM of oleic acid (OA), 2,000 µg/ml of LDL cholesterol (LDL), or both LDL + OA for 20 days, after which they were cocultured with PMA-activated THP-1 cells (macrophages). A: mRNA expression was measured after 3 h. Increased mRNA expression of Il-1b and to a lesser extent Tnfα and Nlrp3 mRNA by the THP-1 cells was noted when cocultured with HepG2 cells that had been previously exposed to both LDL + OA and had developed cholesterol crystals in their lipid droplets. B: IL-1b in the media at 24 h as measured by ELISA. Results are shown as a percentage of control cells. Significantly increased IL-1b secretion occurred in the THP-1 cells cocultured with HepG2 cells that had been previously exposed to both LDL + OA. C: Exposure of PMA-activated THP-1 cells directly to synthetic cholesterol crystals causes a dose-dependent secretion of IL-1b. ★Results are significant at P < .05 in comparison with control.