Neutrophils in pathophysiology of epilepsy – EpiNeutro

Epilepsy is brain disorder characterized by hyper-excitable neurons and tissular remodelling as neuronal death, neuro-inflammation and vascular remodelling. The Blood Brain Barrier (BBB) disruption as well as chronic neuroinflammation are known to contribute to neuronal hyperexcitability. Neuro-inflammation in epilepsy could be acquired from systemic inflammation via the migration of peripheral leucocytes, highly activated in blood of patient, through the BBB disruption. Neutrophils (PMNs), key cells of the innate immune system, act as a first line of host defense and are also important mediators of inflammation-induced vascular and tissue injury. PMNs granules present a high level of metalloproteinase 9 that is correlated with BBB disruption in epileptic patients. IL-8, a strong chemoattractant and activator of PMNs, is released by activated microglia 4 hours after epileptic seizures in human tissue. Moreover, in rodent model, PMN infiltration in parenchyma is observed around vasogenic oedema after seizures and depleting PMN reduce the severity of seizures.

Despite their critical role in innate immune system and some evidence of their possible impact on neuropathology little attention has been focused on the role of PMNs in epilepsy and more particularly on their impact on BBB disruption. This translational project in collaboration with clinicians of pitié-salpétriere hospital, will characterize the phenotype and functions of PMNs and their impact on BBB integrity in the pathophysiology of epilepsy. This project combines clinical studies, mouse model of epilepsy and in vitro experiments. First of all, we will characterize subtype and function of peripheral PMNs by flow cytometry in blood of epileptic patient and of epileptic mouse. We will take the advantage of rodent model of epilepsy to follow PMNs phenotype during epileptogenesis and seizure severity. Secondly, their impact on BBB disruption will be studied by depleting PMNs in epileptic mice. Human endothelial cells (hCMEC/D3) co-cultured with isolated PMNs from epileptic patient, will allow us to understand the mechanisms of PMNs on the loss of endothelial cell integrity.

This project will gain knowledge on the activation, subtype and functions of peripheral PMNs. It will be the first study to evaluate peripheral PMNs in relation to seizures and may suggest new markers of seizure severity and frequency. This project will also be a pivotal study in the contributions of PMNs in BBB disruption during epileptogenesis. This would enhance the understanding of epileptogenesis. As still 30% of epilepsy are pharmacoresistant, our data should thus open new perspectives in the development of innovative immunotherapy strategies by modulating PMNs response.