Dimethyl fumarate (DMF) was recently approved by the FDA for the treatment of relapsing remitting MS. The pathology of MS is a result of both immune dysregulation and oxidative stress induced damage, and DMF is believed to have therapeutic effects on both of these processes. However, the mechanisms of action of DMF are not fully understood. To determine if DMF is able to activate signaling cascades that affect immune dysregulation, we treated human peripheral blood mononuclear cells with DMF. We discovered that DMF stimulates cyclic adenosine monophosphate (cAMP) production after 1 min treatment in vitro. cAMP is a small molecule second messenger that has been shown to modulate immune response. Using pharmacological inhibitors, we determined that adenylyl cyclase mediates DMF induced CAMP production; DMF activated the prostaglandin EP2 receptor to produce cAMP. This response was not due to increased endogenous production of prostaglandin E2 (PGE(2)), but was enhanced by addition of exogenous PGE(2). Furthermore, we determined that the bioactive metabolite of DMF, monomethyl fumarate (MMF), also stimulates cAMP production. These novel findings suggest that DMF may provide protection against MS by inhibiting immune cell function via the CAMP signaling pathway. Published by Elsevier Inc.