Validating differential regulation of mRNAs during MSU crystal inflammation in mouse peritoneal macrophages. Cells were harvested at the indicated time points after the addition of medium containing monosodium urate (MSU) crystals (200 μg/ml) or medium alone. RNA was analyzed by TaqMan real-time reverse transcription PCR for expression of the targets indicated in the figure. Results represent the averages of two experiments. Induction of target mRNAs in negative control (medium only) cells was negligible in nearly all cases. Therefore, the curves corresponding to the negative controls are not shown. However, numeric values for mean fold expression changes in MSU stimulated and negative controls with respect to t = 0 hours are listed below for the time points of maximal induction by MSU crystals. (a) Tumour necrosis factor (TNF)-α (2 hours: MSU:medium = 28.1:1.2), IL-6 (1 hour: MSU:medium = 49.7:1.2), IL-1β (2 hours: MSU:medium = 13.1:0.5); and early growth response (Egr)-1 (1 hour: MSU:medium = 17.4:1). (b) Irg1 (6 hours: MSU:medium = 60.0:6.8); prokineticin (PROK)-2 (6 hours: MSU:medium, 11.0:1.0), histidine decarboxylase (Hdc; 9 hours: MSU:medium = 11.6:0.9) and protein upregulated on macrophages activated with interferon-γ (PUMA-g; 9 hours: MSU:medium = 73.5:2.5). (c) Comparison of fold induction by MSU crystals in dissected membranes versus macrophage culture.