Inhibition of cyclooxygenase-2 reduces proliferation of endogenous neural progenitors and ameliorates the epileptogenic process

Abstract

Cyclooxygenase-2 (COX-2), the principal isoenzyme in the brain, modulates inflammation, glutamate-mediated cytotoxicity, and synaptic plasticity. Its major metabolite, PGE2, exerts the action via EP1-4 receptor. Status epilepticus (SE) induces the epileptogenic process through the generation of ectopic hilar granule cells, and COX-2 is upregulated during this period. In this study, we investigated whether celecoxib, a selective COX-2 inhibitor, can prevent the epileptogenic process in the pilocarpine-induced SE. Experimental SE was induced with lithium-pilocarpine injection, and celecoxib (20 mg/kg, p.o.) were treated at 2 hours after SE and afterwards for 7 or 35 days. BrdU was injected for 7 or 14 days after SE. Spontaneous recurrent seizure (SRS) were video-monitored. BrdU immunohistochemistry was used for the spatial and temporal analysis of hippocampal cell proliferation, and double labellings using NeuN, calbindin or GFAP antibodies were performed. For in vitro study, cultured human neural stem cells (NSCs, F3 cell) were treated with celecoxib, PGE2, or EP2 receptor agonist butaprost, and analyzed in means of BrdU / Ki-67 labeling index, cell cycle analysis and MTT assay. Celecoxib treatment reduced neural damage at 7 and 42 days after status epilepticus (esp. CA1, CA3 and Hilar damage) and reduced microglial infiltration after SE. In addition, celcoxib treatment reduced the proliferation of neural progenitors in subgranular layer of dentate gyrus, and reduced BrdU+ /Calbindin+ /NeuN+ cells in hilar areas. No hilar ectopic granule cell can be found in celecoxib-treated group (ectopic granule neurons: 45% of hilar BrdU+ cells in epilepsy-only group vs. 0% in epilepsy-celecoxib group). Most of the BrdU-labeled cells in the hilar area are positive to GFAP. Celecoxib treatment reduced reactive COX-2 expression in the SE-damaged brain, especially in the early period (days 1–7), with a decrease in SRS formation (days 28-42; p<0.05). In vitro analysis showed that celecoxib dose-dependently inhibited proliferation of NSCs with a decrease in BrdU/Ki-67 labeling index and in a proportion of S phase by cell cycle analysis. In contrast, PGE2 or butaprost treatment increases NSCs proliferation. COX-2 inhibition interfered with cell cycle propagation of NSCs. Taken together, we provide evidences that inhibition of COX-2 prevents the epileptogenic process, which might be due to the neuroprotective and anti-inflammatory effects, and suppression of abnormal neural progenitor proliferation.