Glucocorticoids Suppress Tumor Necrosis Factor-α Expression by Human Monocytic THP-1 Cells by Suppressing Transactivation through Adjacent NF-κB and c-Jun-Activating Transcription Factor-2 Binding Sites in the Promoter
Journal of Biological Chemistry
Glucocorticoid drugs suppress tumor necrosis factor-␣ (TNF-␣) synthesis by activated monocyte/macrophages, contributing to an anti-inflammatory action in vivo. In lipopolysaccharide (LPS)-activated human monocytic THP-1 cells, glucocorticoids acted primarily on the TNF-␣ promoter to suppress a burst of transcriptional activity that occurred between 90 min and 3 h after LPS exposure. LPS increased nuclear c-Jun/ATF-2, NF-B 1 /Rel-A, and Rel-A/C-Rel transcription factor complexes, which bound
... ifically to oligonucleotide sequences from the ؊106 to ؊88 base pair (bp) region of the promoter. The glucocorticoid, dexamethasone, suppressed nuclear binding activity of these complexes prior to and during the critical phase of TNF-␣ transcription. Site-directed mutagenesis in TNF-␣ promoterluciferase reporter constructs showed that the adjacent c-Jun/ATF-2 (؊106 to ؊99 bp) and NF-B (؊97 to ؊88 bp) binding sites each contributed to the LPS-stimulated expression. Mutating both sites largely prevented dexamethasone from suppressing TNF-␣ promoter-luciferase reporters. LPS exposure also increased nuclear Egr-1 and PU.1 abundance. The Egr-1/Sp1 (؊172 to ؊161 bp) binding sites and the PU.1-binding Ets site (؊116 to ؊110 bp) each contributed to the LPS-stimulated expression but not to glucocorticoid response. Dexamethasone suppressed the abundance of the c-Fos/c-Jun complex in THP-1 cell nuclei, but there was no direct evidence for c-Fos/c-Jun transactivation through sites in the ؊172 to ؊52 bp region. Small contributions to glucocorticoid response were attributable to promoter sequences outside the ؊172 to ؊88 bp region and to sequences in the TNF-␣ 3-untranslated region. We conclude that glucocorticoids suppress LPS-stimulated secretion of TNF-␣ from human monocytic cells largely through antagonizing transactivation by c-Jun/ATF-2 and NF-B complexes at binding sites in the ؊106 to ؊88 bp region of the TNF-␣ promoter.