Up-regulation of cytokine and chemokine mRNA expression in THP-1 monocytes by PlGF. THP-1 cells were treated with PlGF for time periods of 1 to 24 hours, and RNA was isolated; 10 μg RNA samples were hybridized with ³²P-labeled antisense mRNA probes and digested with RNase and T1 nuclease. The protected hybridized probe fragments were resolved on 5% polyacrylamide gel. The intensity of radioactive bands in the autoradiogram was quantitated by the Alpha Imager documentation system. The relative mRNA levels were determined by normalizing band intensities of TNF-α, IL-1β, MIP-1β, MCP-1, and IL-8 with that of GAPDH housekeeping gene. The data presented are representative of 1 of 3 replicate experiments.