Background and Purpose Neonatal seizures are a clinical emergency. Current anti-seizure medications, however, fail to resolve seizures in ~50% of infants. The P2X7 receptor (P2X7R) is an important driver of inflammation and evidence suggest P2X7R contributing to seizures and epilepsy in adults. To date, however, no genetic proof has been provided to determine the contribution of the P2X7R to neonatal seizures, its effects on inflammatory signalling during neonatal seizures and the therapeutic potential of P2X7R-based treatments on long-lasting brain excitability. Experimental Approach Neonatal seizures were induced via global hypoxia in 7 day-old mouse pups (P7). The role of P2X7Rs during seizures was analyzed in P2X7R overexpressing and knock-out mice. Treatment of wild-type mice post-hypoxia with the P2X7R antagonist JNJ-47965567 was used to determine the effects of the P2X7R on long-lasting brain hyperexcitability. Cell type-specific P2X7R expression was analyzed via P2X7R-EGFP reporter mice. RNA sequencing was used to monitor P2X7R-dependent hippocampal down-stream signalling. Key Results P2X7R deletion reduced seizure severity whereas P2X7R overexpression exacerbated seizure severity and reduced responsiveness to anti-seizure medication. P2X7R deficiency let to an anti-inflammatory phenotype in microglia and treatment of mice with a P2X7R antagonist reduced long-lasting brain hyperexcitability. RNA sequencing identified several pathways altered in P2X7R knock-out mice after neonatal hypoxia including a down-regulation of genes implicated in inflammation and glutamatergic signalling. Conclusion and Implications Treatments based on targeting the P2X7R may represent a novel therapeutic strategy for neonatal seizures with P2X7Rs contributing to the generation of neonatal seizures, driving inflammatory processes and long-term hyperexcitability states.

Background and Purpose Refractory status epilepticus is a clinical emergency associated with high mortality and morbidity. Increasing evidence suggests neuroinflammatory pathways contribute to the development of drug-refractoriness during status epilepticus. The ATP-gated P2X7 receptor (P2X7R) has been described as potential link between inflammation and increased hyperexcitability. The aim of the present study was to determine the contribution of the P2X7R to drug-refractory status epilepticus and its therapeutic potential. Experimental Approach Status epilepticus was induced via a unilateral microinjection of kainic acid into the amygdala in adult mice. Severity of status epilepticus was compared in animals overexpressing or knock-out in the P2X7R, after inflammatory priming by the pre-injection of bacterial lipopolysaccharide (LPS) and in mice treated with P2X7R-targeting and anti-inflammatory drugs. Key Results P2X7R overexpressing mice were unresponsive to several anticonvulsants (lorazepam, midazolam, phenytoin and carbamazepine) during status epilepticus. P2X7R expression was increased in microglia during drug-refractory status epilepticus, P2X7R overexpression led to a pro-inflammatory phenotype in microglia during status epilepticus and the anti-inflammatory drug minocycline restored normal responsiveness to anticonvulsants in P2X7R overexpressing mice. Pre-treatment of wildtype mice with LPS increased P2X7R levels in the brain and promoted the development of pharmaco-resistant status epilepticus, which was overcome by either a genetic deletion of the P2X7R or the administration of the P2X7R antagonists AFC-5128 or ITH15004. Conclusion and Implications Our results demonstrate that P2X7R-induced pro-inflammatory effects contribute to resistance to pharmacotherapy during status epilepticus and suggest therapies targeting the P2X7R as novel adjunctive treatments for drug-refractory status epilepticus.