Context-Specific Switch from Anti- to Pro-epileptogenic Function of the P2Y₁ Receptor in Experimental Epilepsy

Abstract

Extracellular ATP activates inflammatory responses to tissue injury. It is also implicated in establishing lasting network hyperexcitability in the brain by acting upon independent receptor systems. Whereas the fast-acting P2X channels have well-established roles driving neuroinflammation and increasing hyperexcitability, the slower-acting metabotropic P2Y receptors have received much less attention. Recent studies of P2Y 1 receptor function in seizures and epilepsy have produced contradictory results, suggesting that the role of this receptor during seizure pathology may be highly sensitive to context. Here, by using male mice, we demonstrate that the metabotropic P2Y 1 receptor mediates either proconvulsive or anticonvulsive responses, dependent on the time point of activation in relation to the induction of status epilepticus. P2Y 1 deficiency or a P2Y 1 antagonist (MRS2500) administered before a chemoconvulsant, exacerbates epileptiform activity, whereas a P2Y 1 agonist (MRS2365) administered at this time point is anticonvulsant. When these drugs are administered after the onset of status epilepticus, however, their effect on seizure severity is reversed, with the antagonist now anticonvulsant and the agonist proconvulsant. This result was consistent across two different mouse models of status epilepticus (intraamygdala kainic acid and intraperitoneal pilocarpine). Pharmacologic P2Y 1 blockade during status epilepticus reduces also associated brain damage, delays the development of epilepsy and, when applied during epilepsy, suppresses spontaneous seizures, in mice. Our data show a context-specific role for P2Y 1 during seizure pathology and demonstrate that blocking P2Y 1 after status epilepticus and during epilepsy has potent anticonvulsive effects, suggesting that P2Y 1 may be a novel candidate for the treatment of drug-refractory status epilepticus and epilepsy. This is the first study to fully characterize the contribution of a metabotropic purinergic P2Y receptor during acute seizures and epilepsy. The findings suggest that targeting P2Y 1 may offer a potential novel treatment strategy for drug-refractory status epilepticus and epilepsy. Our data demonstrate a context-specific role of P2Y 1 activation during seizures, switching from a proconvulsive to an anticonvulsive role depending on physiopathological context. Thus, our study provides a possible explanation for seemingly conflicting results obtained between studies of different brain diseases where P2Y 1 targeting has been proposed as a potential treatment strategy and highlights that the timing of pharmacological interventions is of critical importance to the understanding of how receptors contribute to the generation of seizures and the development of epilepsy.

Update of P2Y receptor pharmacology: IUPHAR Review 27

“…P2Y 1 receptor antagonism is associated with cerebroprotection and might improve cognition in Alzheimer's disease (Reichenbach et al, 2018) and glutamate mediated hippocampal neurodegeneration (Simões et al, 2018). P2Y 1 receptors could also be novel candidates for the treatment of epilepsy (Alves et al, 2019). However, P2Y 1 and P2Y 13 receptor agonists could also display neuroprotective actions against oxidative stress and glutamate excitotoxicity as reported in other experimental models (Miras Portugal et al, 2019).…”

Differential Expression of the Metabotropic P2Y Receptor Family in the Cortex Following Status Epilepticus and Neuroprotection via P2Y1 Antagonism in Mice

“…Further supporting a role for P2Y receptors during seizures, mice deficient in P2Y 12 display a more severe seizure phenotype during status epilepticus (Eyo et al, 2014). P2Y 1 antagonism has been shown to reduce seizure severity and protect against hippocampal neurodegeneration (Simoes et al, 2018;Alves et al, 2019). This is of no surprise considering the well documented role of P2Y 1 to regulate neurotransmitter release, facilitate neuronal excitability, and mediate microglia migration and activation (Guzman and Gerevich, 2016).…”

“…Minocycline (30 mg/kg, PBS) (Sigma-Aldrich (M9511), Dublin, Ireland) was administered twice via i.p. injection (200 ml) 24 and 4 h before triggering status epilepticus via intraamygdala KA (Alves et al, 2019).…”

“…Among the P2Y receptors analyzed, P2Y 1 was one of the receptors showing the strongest increase in its expression in the cortex following status epilepticus. Importantly, recent data suggests a functional role of P2Y 1 during status epilepticus and epilepsy (Alves et al, 2019). Therefore, to test whether P2Y receptor activation impacts on cortical neurodegeneration, our subsequent studies focused on the P2Y 1 receptor subtype.…”

“…Mounting data has repeatedly demonstrated distinct changes in the expression profile of P2X and P2Y family members following acute seizures and during epilepsy, and provided compelling evidence that drugs blocking P2X or P2Y members alter seizure severity and may even impact on the development of epilepsy (Amhaoul et al, 2016;Engel et al, 2016;Amorim et al, 2017;Alves et al, 2018). While most efforts have been invested to study the effects of the fast-acting P2X receptor family on seizures and epilepsy, in particular the P2X7 receptor , increasing evidence also suggest a causal role for P2Y receptors during seizure-induced pathology (Eyo et al, 2014;Avignone et al, 2015;Alves et al, 2017;Alves et al, 2018;Alves et al, 2019). P2Y receptor expression is altered in the hippocampus following status epilepticus and during epilepsy and ADP and UTP, both broadspectrum P2Y receptor agonists, alter seizure severity during status epilepticus and seizure-induced neurodegeneration .…”