Epigenetic and transcriptional regulation of CCL17 production by glucocorticoids in arthritis

Glucocorticoids (GCs) are potent anti-inflammatory agents and are broadly used in treating rheumatoid arthritis (RA) patients, albeit with adverse side effects associated with long-term usage. The negative consequences of GC therapy provide an impetus for research into gaining insights into the molecular mechanisms of GC action. We have previously reported that granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced CCL17 has a non-redundant role in inflammatory arthritis. Here, we provide molecular evidence that GCs can suppress GM-CSF-mediated upregulation of IRF4 and CCL17 expression via downregulating JMJD3 expression and activity. In mouse models of inflammatory arthritis, GC treatment inhibited CCL17 expression and ameliorated arthritic pain-like behavior and disease. Significantly, GC treatment of RA patient peripheral blood mononuclear cells ex vivo resulted in decreased CCL17 production. This delineated pathway potentially provides new therapeutic options for the treatment of many inflammatory conditions, where GCs are used as an anti-inflammatory drug but without the associated adverse side effects. [Display omitted] •Dexamethasone suppresses GM-CSF-induced CCL17 formation in monocytes and macrophages•By suppressing JMJD3/IRF4 expression, dexamethasone inhibits CCL17 expression•Decreasing CCL17 correlates with dexamethasone-mediated amelioration of arthritis•Dexamethasone-mediated inhibition of CCL17, IRF4, and JMJD3 is evident in RA samples Orthopedics; Molecular mechanism of gene regulation; Epigenetics