Figure 5.

Silica exposure decreased uptake of fluorescently labeled synthetic diacylated and triacylated lipoproteins in vitro. Macrophages derived from the bone marrow of wild-type C57Bl/6 and CD204^−/− mice were exposed to media or silica (100 μg/ml) for 24 h and subsequently treated with fluorescently labeled Pam₂CSK₄ and Pam₃CSK4 for 2 h. (A) Flow cytometry revealed uptake of the rhomadine-labeled lipoproteins into macrophages as measured by an increase in the mean fluorescence intensity (MFI), which was attenuated in the SiO₂-exposed macrophages. This increase in MFI was not due to changes in the uptake of SiO₂ into the macrophages, as shown by an increase in SSC. (B) Representative images from confocal microscopy showed increased fluorescence in the macrophages exposed to fluorescently labeled lipoproteins vs. media alone. Moreover, this fluorescence was diminished in SiO₂-exposed macrophages. Results are means ± SEM (n = 5). *p < 0.05 compared to media.