Subsequently, the culture supernatant was collected and stored at -70°C. IL-8 concentration was measured by enzyme-linked immunosorbent assay (ELISA) assay. As a positive control, a separate group of PMA-differentiated U937 cells was stimulated with TNF-α and PCN. RNA was extracted afterwards, and IL-8 mRNA levels were determined. In some experiments, SB203580, PD98059 or PDTC was added into fresh medium

of U937 cells at 60 min before PCN incubation. Thiazolyl blue tetrazolium bromide (MTT) assay Cell viability was assessed using the MTT assay (Sigma) according to the manufacturer’s instructions. Measurement of IL-8 Cells were cultured in 24-well tissue culture plates until they reached 80-90% confluence. Cells were cultured in serum-free medium without growth factors and medium supplements for 24 h prior to treatment. The medium was harvested 24 h after treatment selleck screening library and stored SCH727965 purchase at -20°C until assayed. IL-8 level was determined by ELISA according to the manufacturer’s instructions. The reproducibility, calculated as the coefficient of variation (CV), was 5.5%. Reverse transcription-polymerase chain reaction (RT-PCR) Total RNA was extracted from the U937 cells as described by Chomczynski [22]. At the end of the incubation period, cells were washed with 1 mL ice-cold PBS and solubilized with 1 mL of trizol. RNA was treated with

chloroform, centrifuged at 12000 × g for 15 min at 4°C and finally precipitated with ethanol. RNA was extracted and redissolved in diethylpyrocarbonate-treated water,

and the OD at 260 nm was used to determine its concentration. To synthesize cDNA, 2.5 μg of RNA was resuspended in a 10 μL final volume of the reaction buffer and incubated for 30 min at 42°C. The reaction was stopped by denaturing the enzyme at 95°C for 5 min. Polymerase chain reaction was performed as follows. Ten microliters of the synthesized cDNA were added to 40 μL of PCR mixture containing 5 μL of 5 × PCR buffer, 1 μL of primers (GenBank accession PLEKHB2 IL-8 sense: 5′-AGATGTCAGTGCATAAAGACA-3′, click here antisense: 5′-TGAATTCTCAG CCCTCTTCAAAAA-3′, 201 bp; GenBank accession β-actin sense: 5′-GGCATGGGTCAGAAGGATY CC-3′, antisense: 5′-ATGTCACGCACGATTTCCCGC-3′, 501 bp) and 0.25 μL DNA polymerase. PCR conditions for IL-8 were 35 cycles of denaturation at 94°C for 45 s, annealing at 55.3°C for 45 s and extension at 72°C for 1 min. PCR conditions for β-actin were 35 cycles of denaturation at 94°C for 45 s, annealing at 59°C for 45 s and extension at 72°C for 1 min. Amplified PCR products were separated by electrophoresis on 1.5% agarose gel (UltraPure, Sigma) containing 0.05 μg/mL ethidium bromide. The mRNA expression was visualized using a Gel imaging system and analyzed using the molecular analyst software and was standardized by the β-actin housekeeping gene signal to correct any variability in gel loading.