Antiinflammatory effects of glucocorticoids in brain cells, independent ofNF-kappa B

Glucocorticoids are potent antiinflammatory drugs. They inhibit the express ion of proinflammatory cytokines and adhesion molecules. It has recently be en proposed that the underlying basis to such inhibition is the induction o f the protein I kappa B, which inhibits the transcription factor NF-kappa B , The latter is a key activator of the genes encoding cytokines and adhesio n molecules, The present study shows that the synthetic glucocorticoid, dex amethasone, inhibits the induction of the proinflammatory cytokine IL-8 and the adhesion molecules VCAM-1 and ICAM-1 in human 1321N1 astrocytoma and S K.N.SH neuroblastoma cells. However, dexamethasone failed to induce I kappa B or inhibit activation of NF-kappa B by IL-1 in the two cell types. EMSA confirmed the identity of the activated NF-kappa B by demonstrating that an oligonucleotide, containing the wild-type NF-kappa B-binding moth, inhibit ed formation of the NF-kappa B-DNA complexes whereas a mutated form of the NF-kappa B-binding motif was ineffective. In addition, supershift analysis showed that the protein subunits p50 and p65 were prevalent components in t he activated NF-kappa B complexes. The lack of effect of dexamethasone on t he capacity of IL-1 to activate NF-kappa B correlated with its inability to induce I kappa B and the ability of IL-1 to cause degradation of I kappa B , even in the presence of dexamethasone. The results presented in this pape r strongly suggest that glucocorticoids may exert antiinflammatory effects in cells of neural origin by a mechanism(s) independent of NF-kappa B.