Expression of cyclooxygenase-2 in rat vascular smooth muscle cells is unrelated to nuclear factor-kappa B activation

The promoter region of cyclooxygenase-2 (COX-2) gene contains binding sites for a number of important transcription factors including cyclic AMP respo nse element, nuclear factor-IL6, nuclear factor-kB (NF-kB) and TGF-beta res ponse element. Several reports have documented that the activation of NF-kB triggers the expression of COX-2 gene. In the present study, NF-kB was act ivated by TNF-alpha in rat aortic smooth muscle cells as demonstrated by el ectrophoretic mobility shift assay. The activity of NF-kB induced by TNF-al pha was blocked by calpain inhibitor I, a potent NF-kB inhibitor. However, the activation of NF-kB was not related to the expression of COX-2 induced by TNF-alpha since calpain inhibitor I blocked the activation of NF-kB but not the expression of COX-2 mRNA or protein. Mutation of rat COX-2 NF-kB-li ke sites in the promoter region did not significantly reduce the promoter a ctivity. These results suggest that the transcriptional regulation of COX-2 expression by NF-kB depends upon the types of cells studied and that activ ation of this transcription factor alone does not play an important role in the expression of COX-2 in rat smooth muscle cells.