Dexamethasone is an antiinflammatory glucocorticoid that induces the production of phospholipase A2 inhibitory protein (lipocortin). It also inhibits induction of nitric oxide synthase (IC50=5 nM). Dexamethasone has been shown to cause reduction in cyclin A and Cdk2 activity, inhibition of G1/S transition in osteoblasts and inhibition of phosphorylation of Rb protein in vitro. Dexamethasone has been observed to induce apoptosis in human thymocytes and eosinophils, but inhibits apoptosis in neutrophils in vitro. Dexamethasone is an activator of IDO.