Requirement of nuclear factor κB for the constitutive expression of nitric oxide synthase-2 and cyclooxygenase-2 in rat trophoblasts

Recently isolated trophoblasts express nitric oxide synthase 2 (NOS-2) and cyclooxygenase 2 (COX-2), decreasing the levels of the corresponding mRNAs when the cells were maintained in culture. The sustained expression of COX-2 and NOS-2 in trophoblasts was dependent on the activation of nuclear factor kappa B (NF-kappa B) since proteasome inhibitors and antioxidants that abrogated NF-kappa B activity suppressed the induction of both genes, The time-dependent fall of the mRNA levels of NOS-2 and COX-2 paralleled the inhibition of NF-kappa B, determined by electrophoretic mobility shift assays, and the increase of the I kappa B alpha and I kappa B beta inhibitory proteins. Isolated trophoblasts synthesized reactive oxygen intermediates (ROI), a process impaired after culturing the cells, and that might be involved in the NF-kappa B activation process, Moreover, treatment of recently isolated cells with ROI scavengers suppressed the expression of COX-2 and NOS-2, Challenge of trophoblasts with interleukin-1 beta upregulated the expression of both proteins, an effect that was potentiated by lipopolysaccharide, These results indicate that the physiological expression of NOS-2 and COX-2 in trophoblasts involves a sustained activation of NF-kappa B which inhibition abrogates the inducibility of both genes.