The Role of mPGES-1 in Inflammatory Brain Diseases.

Prostaglandin E2 (PGE2) has been thought to be an important mediator of inflammation in peripheral tissues, but recent studies clearly show the involvement of PGE2 in inflammatory brain diseases. In some animal models of brain disease, the genetic disruption and chemical inhibition of cyclooxygenase (COX)-2 resulted in the reduction of PGE2 and amelioration of symptoms, and it had been thought that PGE2 produced by COX-2 may be involved in the progression of injuries. However, COX-2 produces not only PGE2, but also some other prostanoids, and thus the protective effects of COX-2 inhibition, as well as severe side effects, may be caused by the inhibition of prostanoids other than PGE2. Therefore, to elucidate the role of PGE2, studies of microsomal prostaglandin E synthase-1 (mPGES-1), an inducible terminal enzyme for PGE2 synthesis, have recently been an active area of research. Studies from mPGES-1 deficient mice provide compelling evidence for its role in a variety of inflammatory brain diseases, such as ischemic stroke, Alzheimer's disease and epilepsy, and clues for developing new therapeutic treatments for brain diseases by targeting mPGES-1. Considering that COX inhibitors may non-selectively suppress the production of many types of prostanoids that are essential for normal physiological functioning of the brain and peripheral tissues, as well as induce gastro-intestinal, renal and cardiovascular complications, mPGES-1 inhibitors are expected to be injury-selective and have fewer side-effects when treating human brain diseases. Thus, this paper focuses on recent studies that have demonstrated the involvement of mPGES-1 in pathological brain diseases.