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Background and Purpose: Neonatal seizures represent a clinical emergency. However, current anti‐seizure medications fail to resolve seizures in ~50% of infants. The P2X7 receptor (P2X7R) is an important driver of inflammation, and evidence suggests that P2X7R contributes to seizures and epilepsy in adults. However, no genetic proof has yet been provided to determine what contribution P2X7R makes 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 by global hypoxia in 7‐day‐old mouse pups (P7). The role of P2X7Rs during seizures was analysed in P2X7R‐overexpressing and knockout mice. Treatment of wild‐type mice after 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 analysed in P2X7R‐EGFP reporter mice. RNA sequencing was used to monitor P2X7R‐dependent hippocampal downstream signalling. Key Results: P2X7R deletion reduced seizure severity, whereas P2X7R overexpression exacerbated seizure severity and reduced responsiveness to anti‐seizure medication. P2X7R deficiency led 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 knockout 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. [ABSTRACT FROM AUTHOR]

Purinergic signaling via P2 receptors is now widely accepted to play a critical role during increased states of hyperexcitability and seizure-induced pathology. In the setting of seizures and epilepsy, most attention has been paid to investigating the fast-acting ATP-gated P2X receptor family. More recent evidence has now also provided compelling evidence of an involvement of the slower-acting P2Y receptor family during seizures. This includes data demonstrating expression changes of P2Y receptors in the hippocampus following acute seizures and during epilepsy and anticonvulsive properties of P2Y-targeting drugs; in particular drugs targeting the P2Y1 subtype. Seizures, however, also involve damage to extra-hippocampal brain regions such as the cortex, which is thought to contribute to the epileptic phenotype. To analyze expressional changes of the P2Y receptor family in the cortex following status epilepticus and to determine the impact of drugs interfering with P2Y1 signaling on cortical damage, we used a unilateral mouse model of intraamygdala kainic acid-induced status epilepticus. Analysis of cortical tissue showed that status epilepticus leads to a global up-regulation of the P2Y receptor family in the cortex including P2Y1, P2Y2, P2Y4, and P2Y6, with the P2Y1 and P2Y4 receptor subtypes showing the strongest increase. Supporting a detrimental role of P2Y1 activation during status epilepticus, treatment with the P2Y1 agonist MRS2365 exacerbated high frequency high amplitude spiking, synonymous with injury-causing electrographic activity, and treatment with the P2Y1 antagonists MRS2500 protected against seizure-induced cortical damage. Suggesting P2Y1-mediated effects are predominantly due to increased microglia activation, treatment with the broad-spectrum anti-inflammatory drug minocycline abolished the observed neuroprotective effects of P2Y1 antagonism. In conclusion, our results further support a role for P2Y1-mediated signaling during seizure generation and seizure-induced neurodegeneration, suggesting P2Y1-targeting therapies as novel treatment for drug-refractory status epilepticus. [ABSTRACT FROM AUTHOR]

Epilepsy is one of the most common chronic diseases of the central nervous system (CNS). Treatment of epilepsy remains, however, a clinical challenge with over 30% of patients not responding to current pharmacological interventions. Complicating management of treatment, epilepsy comes with multiple comorbidities, thereby further reducing the quality of life of patients. Increasing evidence suggests purinergic signalling via extracellularly released ATP as shared pathological mechanisms across numerous brain diseases. Once released, ATP activates specific purinergic receptors, including the ionotropic P2X7 receptor (P2X7R). Among brain diseases, the P2X7R has attracted particular attention as a therapeutic target. The P2X7R is an important driver of inflammation, and its activation requires high levels of extracellular ATP to be reached under pathological conditions. Suggesting the therapeutic potential of drugs targeting the P2X7R for epilepsy, P2X7R expression increases following status epilepticus and during epilepsy, and P2X7R antagonism modulates seizure severity and epilepsy development. P2X7R antagonism has, however, also been shown to be effective in treating conditions most commonly associated with epilepsy such as psychiatric disorders and cognitive deficits, which suggests that P2X7R antagonisms may provide benefits beyond seizure control. This review summarizes the evidence suggesting drugs targeting the P2X7R as a novel treatment strategy for epilepsy with a particular focus of its potential impact on epilepsy-associated comorbidities. [ABSTRACT FROM AUTHOR]

Neonatal seizures are one of the most common comorbidities of neonatal encephalopathy, with seizures aggravating acute injury and clinical outcomes. Current treatment can control early life seizures; however, a high level of pharmacoresistance remains among infants, with increasing evidence suggesting current anti-seizure medication potentiating brain damage. This emphasises the need to develop safer therapeutic strategies with a different mechanism of action. The purinergic system, characterised by the use of adenosine triphosphate and its metabolites as signalling molecules, consists of the membrane-bound P1 and P2 purinoreceptors and proteins to modulate extracellular purine nucleotides and nucleoside levels. Targeting this system is proving successful at treating many disorders and diseases of the central nervous system, including epilepsy. Mounting evidence demonstrates that drugs targeting the purinergic system provide both convulsive and anticonvulsive effects. With components of the purinergic signalling system being widely expressed during brain development, emerging evidence suggests that purinergic signalling contributes to neonatal seizures. In this review, we first provide an overview on neonatal seizure pathology and purinergic signalling during brain development. We then describe in detail recent evidence demonstrating a role for purinergic signalling during neonatal seizures and discuss possible purine-based avenues for seizure suppression in neonates. [ABSTRACT FROM AUTHOR]

• P2X7R signaling regulates both glial and neuronal genes during seizures. • P2X7R deficiency in microglia reduces seizure severity and leads to an anti-inflammatory phenotype in microglia during seizures. • P2X7R deficiency in neurons increases seizure severity. • Increased expression of P2X7Rs on GABAergic interneurons reduces seizure severity in acquired and genetic models of epilepsy. The purinergic ATP-gated P2X7 receptor (P2X7R) is increasingly recognized to contribute to pathological neuroinflammation and brain hyperexcitability. P2X7R expression has been shown to be increased in the brain, including both microglia and neurons, in experimental models of epilepsy and patients. To date, the cell type-specific downstream effects of P2X7Rs during seizures remain, however, incompletely understood. Effects of P2X7R signaling on seizures and epilepsy were analyzed in induced seizure models using male mice including the kainic acid model of status epilepticus and pentylenetetrazole model and in male and female mice in a genetic model of Dravet syndrome. RNA sequencing was used to analyze P2X7R downstream signaling during seizures. To investigate the cell type-specific role of the P2X7R during seizures and epilepsy, we generated mice lacking exon 2 of the P2rx7 gene in either microglia (P2rx7 : Cx3cr1 -Cre) or neurons (P2rx7 : Thy-1 -Cre). To investigate the protective potential of overexpressing P2X7R in GABAergic interneurons, P2X7Rs were overexpressed using adeno-associated virus transduction under the mDlx promoter. RNA sequencing of hippocampal tissue from wild-type and P2X7R knock-out mice identified both glial and neuronal genes, in particular genes involved in GABAergic signaling, under the control of the P2X7R following seizures. Mice with deleted P2rx7 in microglia displayed less severe acute seizures and developed a milder form of epilepsy, and microglia displayed an anti-inflammatory molecular profile. In contrast, mice lacking P2rx7 in neurons showed a more severe seizure phenotype when compared to epileptic wild-type mice. Analysis of single-cell expression data revealed that human P2RX7 expression is elevated in the hippocampus of patients with temporal lobe epilepsy in excitatory and inhibitory neurons. Functional studies determined that GABAergic interneurons display increased responses to P2X7R activation in experimental epilepsy. Finally, we show that viral transduction of P2X7R in GABAergic interneurons protects against evoked and spontaneous seizures in experimental temporal lobe epilepsy and in mice lacking Scn1a , a model of Dravet syndrome. Our results suggest a dual and opposing action of P2X7R in epilepsy and suggest P2X7R overexpression in GABAergic interneurons as a novel therapeutic strategy for acquired and, possibly, genetic forms of epilepsy. [ABSTRACT FROM AUTHOR]