Hippocampal kindling epileptogenesis upregulates neuronal cyclooxygenase-2 expression in neocortex

Recurrent and spontaneous seizures in epilepsy result from poorly defined cell signaling aberrations thought to include synaptic and extracellular matrix remodeling. Here we have used a rat hippocampal kindling model to study cyclooxygenase-2 (COX-2) gene expression in epileptogenesis. COX-2, encoded in an early-response gene, increases in a synaptic activity-dependent fashion and also during kainic acid-induced hippocampal damage. We found that during kindling, COX-2 induction occurred initially only in hippocampal neurons, and then spread to neocortical neurons. When rats were rekindled 34 days later, this spreading of COX-2 expression persisted. Induction of hippocampal and neocortical cytosolic phospholipase A(2) (cPLA(2)), an enzyme that catalyzes the synthesis of COX-2 substrate arachidonic acid (AA), occurred after 4 days of stimulation during kindling and rekindling. Moreover the COX-2 selective inhibitor nimesulide attenuated kindling development. We conclude that neuronal COX-2 gene induction and cPLA(2) activation are key signaling events in epileptogenesis.