Presentations

Abstract

Introduction: Neuroinflammation is increasingly recognized as a pivotal factor in the development and progression of epilepsy, a chronic neurological disorder characterized by recurrent, spontaneous seizures. Inflammatory processes within the brain can contribute to the onset and exacerbation of epileptic activity by altering neuronal excitability and network stability. CD40, a transmembrane protein of the TNF receptor superfamily, has been implicated in several inflammatory diseases, including epilepsy. CD40 is expressed on the surface of various cell types within the central nervous system (CNS), such as microglia, astrocytes, and neurons. Activation of CD40 by its ligand, CD40L (CD154), leads to the production of pro-inflammatory cytokines like IL-1β, TNF-α, and IL-6, which are known to exacerbate neuroinflammation and potentially contribute to the pathogenesis of epilepsy. Studies have demonstrated that the downregulation of CD40 can attenuate seizure susceptibility, highlighting its potential role in epileptogenesis. Given the critical role of CD40 in neuroinflammation, investigating the expression and function of its ligand, CD40L, in epilepsy is of great interest. This study aimed to explore the expression levels of CD40L in both experimental and clinical models of epilepsy and to assess its potential role in promoting neuroinflammation and epileptogenesis.

Methods: A pilocarpine model of epilepsy was induced in adult male mice to simulate the chronic stages of the disorder. Seizure activity was assessed both clinically, using Racine's score, and electrically, through local field potential recordings obtained from a silicon probe implanted in the brain. Following seizure induction, the mice were euthanized, and brain tissues were collected for further analysis. CD40L expression was examined using immunohistochemistry and biochemical assays. The levels of secretory CD40L (sCD40L) and various cytokines and chemokines were measured using ELISA and the Meso-Scale Discovery platform. In parallel, CD40L expression was also analyzed in human brain samples obtained from epileptic patients through immunohistological techniques. Statistical analyses were performed using ANOVA, Student's t-test, and Z-scores to evaluate the significance of the findings.

Results: Our preliminary data indicate a significant increase in CD40L and sCD40L levels following seizures in both experimental and clinical settings. Immunohistochemical analysis revealed that CD40L is upregulated in neural tissues, particularly within microglia and neurons, in both experimental and human epileptic brain samples. This upregulation was notably higher in areas exhibiting chronic epileptic activity. Furthermore, the increased expression of CD40L in chronic experimental epilepsy correlated positively with elevated levels of IL-1β, a potent pro-inflammatory cytokine known to contribute to the inflammatory response in epilepsy.

Conclusion: These findings suggest that CD40L plays a critical role in the inflammatory processes associated with epilepsy, likely by activating the CD40 pathway and promoting the production of pro-inflammatory molecules. The upregulation of CD40L in microglia and neurons indicates its involvement in the neuroinflammatory cascade that contributes to epileptogenesis. The CD40L-CD40 signaling system appears to be a key component of a broader network of inflammatory mediators that collectively drive the development and progression of epilepsy. Targeting this pathway could offer new therapeutic strategies for controlling neuroinflammation and reducing seizure susceptibility in epileptic patients.