Prostaglandina E2 potencializa as convulsões induzidas por metilmalonato

Abstract

Methylmalonic acidemias comprehend a group of innate error of the metabolism (EIM)characterized clinically and biochemically for the tissue accumulation of acid methylmalonic (MMA)and neurological dysfunction, including seizures. The clinical experience suggests that infections precipitate metabolic crises in methylmalonic acidemic patients. Since it has been demonstrated that MMA cause seizures, and that inflammation facilitates the occurrence of seizures in some animal models, is possible that inflammatory mediators, such as the prostaglandins, also facilitate MMAinduced seizures. Ciclooxigenase (COX) is the rate-limiting enzyme in the metabolic route by which the arachidonic acid is converted to prostaglandins. COX-2 is an isoform of cicloooxigenase that is induced at sites of injury / inflammation, and that is also constitutively expressed in some tissues, such as the central nervous system (CNS). It has been suggested that prostaglandin E2 (PGE2), the main product of COX-2 in the CNS, plays an important role in some neurodegenerative diseases, including epilepsy. However, no study has evaluated whether inflammatory mediators, such as the PGE2, facilitates MMA-induced seizures, to date. Thus, in this study we investigated the role of COX-2 and of PGE2 in seizures induced by MMA (2,5 µmol/2,5 µL, i.c.v.). While PGE2 (100 ng/2 μL, i.c.v.) facilitated, the selective COX-2 inhibitor celecoxib, attenuated MMA-induced seizures, assessed by electroencephalographic recordings in the hippocampus and cerebral cortex of rats. The ´protective effect of celecoxib against MMA-induced seizures was prevented by the PGE2. The results of this study support a facilitatory role for COX-2/PGE2 pathway in the MMA-induced seizures.