Effect of TNFα on mRNA expression of PGE synthases and COX-2. Gingival fibroblasts were treated with TNFα (20 ng/ml) or without TNFα for the indicated time period. Total RNA was extracted from gingival fibroblasts, and mRNA expression of the PGE2 synthesizing enzymes mPGES-1, mPGES-2, cPGES and COX-2, was measured by microarray analysis, using specific probes for each enzyme. Two probes for each of the PGE synthase isoenzymes mPGES-1 and cPGES were present on the chip used in the microarray analysis. The y-axis displays the M-value which is the log2 of the ratio gene expression of TNFα treated cells/gene expression of control cells. A positive number corresponds to higher expression in the TNFα treated cells. The x-axis corresponds to the different time points. A filled circle denotes a significant differentially expressed gene at the indicated time point whereas an empty circle denotes no significant difference.