Sex-related Differences in Glial Fibrillary Acidic Protein-positive GABA Regulate Neuropathology Following Pilocarpine-induced Status Epilepticus

Sex-specific proteomic analysis of epileptic brain tissues from Pten knockout mice and human refractory epilepsy

Rationale

Epilepsy presents significant sex-based disparities in prevalence and manifestation. Epidemiological studies reveal that epilepsy is more prevalent in males, with lesional types being more common, whereas idiopathic generalized epilepsies are more frequently observed in females. These differences stress the importance of considering sex-specific factors in epilepsy diagnosis, treatment, and mechanistic research using preclinical models. To elucidate potential molecular differences that could explain these disparities and inform personalized treatment strategies, we conducted a proteomic analysis of epileptic brain tissues from both an experimental mouse model of genetic epilepsy and humans with drug-resistant epilepsy (DRE).

Methods

We employed mass spectrometry-based proteomic analysis on brain tissues from DRE patients and the Pten knockout (KO) mouse model of genetic epilepsy with focal cortical dysplasia. Mouse samples included hippocampi from adult wild-type (WT) and Pten KO mice (4-5 per group and sex). Human samples included temporal cortex from 12 DRE adult patients (7 males, 5 females) and 5 non-epileptic (NE) controls (2 males, 3 females). Brain biopsies were collected with patients' informed consent under approved IRB protocols (Indiana University Health Biorepository). Proteomic profiles were analyzed using principal component analysis (PCA) along with volcano plots to identify significant changes in protein expression. The enrichment analysis of differentially expressed proteins was conducted by Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway.

Results

PCA revealed distinct clustering of brain proteomes between epilepsy and control cases in both human and mice, with 390 proteins showing significant differences in human and 437 proteins in mouse samples. These proteins are primarily associated with ion channels, synaptic processes, and neuronal energy regulation. In the mouse model, males have more pronounced proteomic changes than females, with enrichment in metabolic pathways and VEGF signaling pathway, indicating a more severe vascular permeability impairment in males. In human DRE cases, 118 proteins were significantly changed by comparing epileptic females to males. Pathway analysis revealed changes in metabolic pathways and the HIF-1 signaling pathway, indicating that altered neuronal activity and inflammation may lead to increased oxygen consumption.

Conclusion

These findings highlight significant differences between epilepsy and control brain samples in both humans and mice. Sex-specific analysis revealed distinct pathway enrichments between females and males, with males exhibiting a broader range of alterations, suggesting more extensive proteomic alterations. This study offers valuable insights into potential underlying mechanisms of epilepsy and underscores the importance of considering sex as a key factor in epilepsy research and therapeutic development.

Sex influences on hippocampal kindling-induced seizures in middle-aged mice

Epilepsy is a chronic neurological disorder, and its prevalence presents a bimodal distribution with high incidences in children and older adults. The incidence of epilepsy does not generally differ between men and women; however, whether this holds true for new-onset epilepsy in older adults is unclear. While studies in animal models of epilepsy may help explore the biological mechanisms relevant to the influences of sex on epileptogenesis, relatively little information is available regarding sex differences in the genesis of epileptic seizures in middle-aged animals. In this study, we addressed this knowledge gap using a mouse model of extended hippocampal kindling. C57 black mice aged between the ages of 12 and 13 months underwent hippocampal kindling as this age roughly corresponds to middle age in humans (∼50 years). Relative to male mice, female mice showed faster-progressing and more severe evoked seizures, a higher tendency to experience spontaneous seizures in the early stage of extended kindling, less frequent expression of hippocampal interictal spikes, and insignificant decreases in hippocampal theta rhythm. Collectively, these results demonstrated the existence of sex-specific differences in hippocampal kindling-induced seizures and suggested that middle-aged female mice have greater but variable susceptibility to hippocampal kindling-induced epileptogenesis compared with male mice of similar age.

Extracellular vesicles from periodontal pathogens regulate hepatic steatosis via Toll-like receptor 2 and plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is associated with nonalcoholic fatty liver disease (NAFLD) by lipid accumulation in the liver. In this study, we showed that extracellular vesicles (EVs) from the periodontal pathogens Filifactor alocis and Porphyromonas gingivalis induced steatosis by inducing PAI-1 in the liver and serum of mice fed a low-fat diet. PAI-1 induction was not observed in TLR2-/- mice. When tested using HEK-Blue hTLR2 cells, human TLR2 reporter cells, the TLR2-activating ability of serum from NAFLD patients (n = 100) was significantly higher than that of serum from healthy subjects (n = 100). Correlation analysis confirmed that PAI-1 levels were positively correlated with the TLR2-activating ability of serum from NAFLD patients and healthy subjects. Amphiphilic molecules in EVs were involved in PAI-1 induction. Our data demonstrate that the TLR2/PAI-1 axis is important for hepatic steatosis by EVs of periodontal pathogens.

Alleviation of hippocampal necroptosis and neuroinflammation by NecroX-7 treatment after acute seizures

Temporal lobe epilepsy (TLE) is one of the most common neurological disorders, but still one-third of patients cannot be properly treated by current medication. Thus, we investigated the therapeutic effects of a novel small molecule, NecroX-7, in TLE using both a low [Mg2+]o-induced epileptiform activity model and a mouse model of pilocarpine-induced status epilepticus (SE). NecroX-7 post-treatment enhanced the viability of primary hippocampal neurons exposed to low [Mg2+]o compared to controls in an MTT assay. Application of NecroX-7 after pilocarpine-induced SE also reduced the number of degenerating neurons labelled with Fluoro-Jade B. Immunocytochemistry and immunohistochemistry showed that NecroX-7 post-treatment significantly alleviated ionized calcium-binding adaptor molecule 1 (Iba1) intensity and immunoreactive area, while the attenuation of reactive astrocytosis by glial fibrillary acidic protein (GFAP) staining was observed in cultured hippocampal neurons. However, NecroX-7-mediated morphologic changes of astrocytes were seen in both in vitro and in vivo models of TLE. Finally, western blot analysis demonstrated that NecroX-7 post-treatment after acute seizures could decrease the expression of mixed lineage kinase domain-like pseudokinase (MLKL) and phosphorylated MLKL (p-MLKL), markers for necroptosis. Taken all together, NecroX-7 has potential as a novel medication for TLE with its neuroprotective, anti-inflammatory, and anti-necroptotic effects.

Role of glutamate excitotoxicity and glutamate transporter EAAT2 in epilepsy: Opportunities for novel therapeutics development

Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.