Central to the bone-sparing effect of estrogen (E2) is its ability to block the monocytic production of the osteoclastogenic cytokine TNF-α (TNF). However, the mechanism by which E2 downregulates TNF production is presently unknown. Transient transfection studies in HeLa cells, an E2 receptor- negative line, suggest that E2 inhibits TNF gene expression through an effect mediated by estrogen receptor β (ERβ). We also report that in RAW 264.7 cells, an E2 receptor-positive murine monocytic line, E2 downregulates cytokine-induced TNF gene expression by decreasing the activity of the Jun NH2-terminal kinase (JNK). The resulting diminished phosphorylation of c-Jun and JunD at their NH2-termini decreases the ability of these nuclear proteins to autostimulate the expression of the c-Jun and JunD genes, thus leading to lower production of c-Jun and JunD. The consequent decrease in the nuclear levels of c-Jun and JunD leads to diminished binding of c-Jun/c-Fos and JunD/c-Fos heterodimers to the AP-1 consensus sequence in the TNF promoter and, thus, to decreased transactivation of the TNF gene.
|Number of pages||11|
|Journal||Journal of Clinical Investigation|
|Publication status||Published - Aug 1999|
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