The samples were then examined click here by phase-contrast and fluorescence microscopy for the level of phagocytosis.

To determine the numbers of colony-forming units of engulfed S. aureus, macrophages incubated with bacteria (macrophages : bacteria = 1 : 500) for 30 min were washed to remove unengulfed bacteria and further incubated for 30 min. The macrophages were lysed with water 0 and 30 min after washing, and the lysates at serial dilutions were seeded on agar-solidified mannitol salt medium or Luria–Bertani medium, the latter of which contained tetracycline and was used for bacteria transformed with the pHY300PLK-based plasmid. The plates were incubated overnight at 37°, and the number of colonies (only selleck kinase inhibitor those surrounded by yellow rings in the mannitol salt medium) was determined and presented relative to that obtained at time 0 after washing. For the determination of superoxide production, macrophages maintained on coverslips in serum-free RPMI-1640 medium were incubated with unlabelled bacteria (macrophages : bacteria = 1 : 1000) at 37°, and the amount of superoxide

released into the culture medium was determined by a chemiluminescence reaction using Diogenes, as described previously.10 To determine the activity of α-N-acetylglucosaminidase, whole-cell lysates of peritoneal macrophages were incubated in a reaction mixture containing 4-methylumbelliferyl N-acetyl-α-d-glucosaminide (Sigma-Aldrich), and the level of cleaved substrates

was measured with a fluorometer, as described previously.25 HEK293 cells were transfected by the calcium/phosphate method overnight with a mixture of plasmid DNA including pELAM26 (a gift from Dr Douglas Golenbock at the University of Massachusetts, Worcester, MA), a reporter gene vector expressing firefly luciferase under the control of a promoter activated by NF-κB; pRL-TK (Promega Corp.), a control reporter constitutively expressing luciferase from Renilla reniformis (Promega Dual-Luciferase Reporter Assay System) used for the normalization of transfection efficiency; and mouse TLR2 cDNA in pDisplay (Invitrogen, Carlsbad, CA) (a gift from Dr Yoshiyuki Adachi at Coproporphyrinogen III oxidase Tokyo University of Pharmacy and Life Science, Tokyo, Japan).27 The cells were further cultured with fresh medium for 1 day and subsequently incubated with S. aureus for 2 hr, and the cell lysates were examined for the amounts of firefly luciferase and Renilla luciferase using the Dual Luciferase Assay kit. The ratio of firefly luciferase to Renilla luciferase was determined and considered to represent the level of NF-κB activation. Data are representative of at least three independent experiments (n = 2–3 in each experiment) that yielded similar results. Data from quantitative analyses are expressed as the mean ± standard deviations of the results from at least three independent experiments.