Dexamethasone up-regulates type IIIL-1 receptor in mouse primary activatedastrocytes

Brain astrocytes play a pivotal role in the brain response to inflammation. They express IL-1 receptors including the type I IL-1 receptor (IL-1 RI) t hat transduces IL-1 signals in cooperation with the IL-l receptor accessory protein (IL-1RAcP) and the type ii IL-1 receptor (IL-1RII) that functions as a decoy receptor. As glucocorticoid receptors are expressed on astrocyte s, we hypothesized that glucocorticoids regulate IL-1 receptors expression. IL-1 beta -activated mouse primary astrocytes were treated with 10(-6) M d examethasone, and IL-1 receptors were studied at the mRNA and protein level s. Using RT-PCR, IL-IRI and IL-1RII but not L-1RAcP mRNAs were found to be up-regulated by dexamethasone in a time-dependent manner. Dexamethasone (De x), but not progesterone, had no effect on IL-IRI but strongly increased IL -1RII mRNA expression. Binding studies revealed Bn increase in the number o f IL-1RII binding sites under the effect or Dex, but no change in affinity. These findings support the concept that glucocorticoids have important reg ulatory effect on the response of astrocytes to IL-1.