Figure 6.

p38 MAPK is involved in regulating endocytosis by leukotriene C₄ (LTC₄) on lipopolysaccharide (LPS) -stimulated dendritic cells (DCs). The DCs and LPS-stimulated DCs (1 μg/ml for 30 min at 37°) were incubated (2.5 × 10⁶ cells/ml) for 20 min at 37° without inhibitors or in the presence of 50 μm SB202190. Then, the cells were exposed to LTC₄ (0.01 μm) for 30 min at 37°. After this time, DCs were washed and cultured for an additional 40 min in the presence of dextran (DX) -FITC (100 μg/ml) at 37°. (a) Results are expressed as mean fluorescence intensity (MFI) and represent the arithmetic mean ± SEM of four experiments. (b,c) and (d) DCs and LPS-stimulated DCs (1 μg/ml for 30 min at 37°) were incubated (2.5 × 10⁶ cells/ml) for 20 min at 37° without inhibitors or in the presence of 50 μm PD98059 or 50 μm SB202190. Then, DCs were untreated or treated with LTC₄ (0.01 μm) for 18 hr at 37°, in some cases, brefeldin A (5 μg/ml) was added during the last 6 hr of culture to inhibit the release of cytokines into the supernatant. (b) Culture supernatants were collected and levels of interleukin-23 (IL-23) were quantified by ELISA. Results are expressed as the cytokine concentrations (pg/ml) and represent the mean ± SEM of four experiments. The percentages of positive cells for IL-12p70 (c) and IL-12p40 (d) are shown and represent the arithmetic mean ± SEM of three experiments. Asterisk represents statistical significance ^*P< 0.05 for DCs pretreated or not with inhibitors and then exposed to LTC₄.