Pneumococcal Infection Response in PM2.5-Treated Macrophages

RAW264.7 cells (2 × 10⁶) were untreated or treated with PM_2.5 (20 μg/ml) for 24 h followed by infection with pneumococcus (MOI = 10) for an additional 6 h. Cells were washed and lysed with 100 μl RIPA containing protease and phosphatase inhibitors (Roche, Indianapolis, IN), and then subjected to western blot assay. The samples were resolved by 12% SDS-PAGE and transferred onto polyvinylidene difluoride membranes (Millipore, Billerica, MA). The membranes were blocked by 5% skim milk and incubated with the primary antibodies followed by incubation with horseradish peroxidase (HRP)-conjugated secondary antibodies (Millipore). The proteins of interests were detected using ECL Western Blotting Detection Reagent (BIOMAN, Taipei, Taiwan) and analyzed by Azure C400 (Azure Biosystems, Dublin, CA) and AzureSpot Analysis Software (Azure Biosystems) [27 (link)]. To determine the intensities of western blot bands, Un-Scan-It v6.1 software (Orem, UT, USA) was used. Identical areas surrounding each band were cropped, and protein expression levels were converted into pixel densities. Each area value was normalized to the β-actin density in the same lane on the gel, and then divided by the normalized density in the mock-control. Fold change represents protein expression level relative to the mock-control.