Neural correlate of reduced respiratory chemosensitivity during chronic epilepsy

While central autonomic cardiorespiratory dysfunction underlies sudden unexpected death in epilepsy (SUDEP), the specific neural mechanisms that lead to SUDEP remain to be determined. Here we took an advantage of single cell neuronal Ca2+ imaging and intrahippocampal kainic acid (KA)-induced chronic epilepsy in mice to investigate progressive changes in key cardiorespiratory brainstem circuits during chronic epilepsy. Following induction of status epilepticus (SE), we observed that the adaptive ventilatory responses to hypercapnia were reduced in mice with chronic epilepsy for 5 weeks post-SE. These changes were paralleled by reduced chemosensitivity of neurons in the retrotrapezoid nucleus (RTN), an important centre for respiratory chemosensitivity. Over the same period, chemosensory responses of the presympathetic RVLM neurons showed a slower decrease. Mice with chronic epilepsy were more sensitive to chemoconvulsants and exhibited a greatly reduced latency to seizure induction compared to naive mice. This enhanced sensitivity to seizures, which invade the RTN, puts the chemosensory circuits at further risk and increases the chances of terminal apnoea. Our findings establish a dysfunctional breathing phenotype with its RTN neuronal correlate in mice with chronic epilepsy and suggests a functional non-invasive biomarker test, based on respiratory chemosensitivity, to identify people with epilepsy at risk of SUDEP.

Choice of anesthesia and data analysis method strongly increases sensitivity of 18F-FDG PET imaging during experimental epileptogenesis

Purpose Alterations in brain glucose metabolism detected by 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) positron emission tomography (PET) may serve as an early predictive biomarker and treatment target for epileptogenesis. Here, we aimed to investigate changes in cerebral glucose metabolism before induction of epileptogenesis, during epileptogenesis as well as during chronic epilepsy. As anesthesia is usually unavoidable for preclinical PET imaging and influences the distribution of the radiotracer, four different protocols were compared. Procedures We investigated 18F-FDG uptake phase in conscious rats followed by a static scan as well as dynamic scans under continuous isoflurane, medetomidine-midazolam-fentanyl (MMF), or propofol anesthesia. Furthermore, we applied different analysis approaches: atlas-based regional analysis, statistical parametric mapping, and kinetic analysis. Results At baseline and compared to uptake in conscious rats, isoflurane and propofol anesthesia resulted in decreased cortical 18F-FDG uptake while MMF anesthesia led to a globally decreased tracer uptake. During epileptogenesis, MMF anesthesia was clearly best distinctive for visualization of prominently increased glucometabolism in epilepsy-related brain areas. Kinetic modeling further increased sensitivity, particularly for continuous isoflurane anesthesia. During chronic epilepsy, hypometabolism affecting more or less the whole brain was detectable with all protocols. Conclusion This study reveals evaluation of anesthesia protocols for preclinical 18F-FDG PET imaging as a critical step in the study design. Together with an appropriate data analysis workflow, the chosen anesthesia protocol may uncover otherwise concealed disease-associated regional glucometabolic changes.

In Silico and In Vivo: Evaluating the Therapeutic Potential of Kaempferol, Quercetin, and Catechin to Treat Chronic Epilepsy in a Rat Model

Recently, alternative therapies are gaining popularity in the treatment of epilepsy. The present study aimed to find out the antiepileptic potential of quercetin, catechin, and kaempferol. In vivo and in silico experiments were conducted to investigate their therapeutic potential. 25 mg/kg/day of pentylenetetrazole was administered for 4 weeks after epilepsy was induced in the rats; this was followed by the behavioral studies and histological analysis of rat brain slices. Binding affinities of kaempferol, quercetin, and catechin were assessed by performing in silico studies. Kaempferol, quercetin, and catechin were found to have the highest binding affinity with the synaptic vesicle 2A (SV2A) protein, comparable to standard levetiracetam (LEV). The mRNA levels of SV2A, as well as the expression of TNF, IL 6, IL 1 beta, NFkB, IL 1Ra, IL 4, and IL 10, were investigated using qPCR. Our results indicate for the first time that SV2A is also a transporter of understudied phytoflavonoids, due to which a significant improvement was observed in epileptic parameters. The mRNA levels of SV2A were found to be significantly elevated in the PF-treated rats when compared with those of the control rats with epilepsy. Additionally, downregulation of the pro-inflammatory cytokines and upregulation of the anti-inflammatory cytokines were also noted in the PF-treated groups. It is concluded that kaempferol, quercetin, and catechin can effectively decrease the epileptic seizures in our chronic epilepsy rat model to a level that is comparable to the antiepileptic effects induced by levetiracetam drug.

AMPA Receptor Antagonists Facilitate NEDD4-2-Mediated GRIA1 Ubiquitination by Regulating PP2B-ERK1/2-SGK1 Pathway in Chronic Epilepsy Rats

The neural precursor cell expressed by developmentally downregulated gene 4-2 (NEDD4-2) is a ubiquitin E3 ligase that has a high affinity toward binding and ubiquitinating glutamate ionotropic receptor α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type subunit 1 (GRIA1, also referred to GluR1 or GluA1). Since dysregulation of GRIA1 surface expression is relevant to the responsiveness to AMPA receptor (AMPAR) antagonists (perampanel and GYKI 52466) in chronic epilepsy rats, it is likely that NEDD4-2 may be involved in the pathogenesis of intractable epilepsy. However, the role of NEDD4-2-mediated GRIA1 ubiquitination in refractory seizures to AMPAR antagonists is still unknown. In the present study, both AMPAR antagonists recovered the impaired GRIA1 ubiquitination by regulating protein phosphatase 2B (PP2B)-extracellular signal-regulated kinase 1/2 (ERK1/2)-serum and glucocorticoid-regulated kinase 1 (SGK1)-NEDD4-2 signaling pathway in responders (whose seizure activities are responsive to AMPAR), but not non-responders (whose seizure activities were uncontrolled by AMPAR antagonists). In addition, cyclosporin A (CsA, a PP2B inhibitor) co-treatment improved the effects of AMPAR antagonists in non-responders, independent of AKT signaling pathway. Therefore, our findings suggest that dysregulation of PP2B-ERK1/2-SGK1-NEDD4-2-mediated GRIA1 ubiquitination may be responsible for refractory seizures and that this pathway may be a potential therapeutic target for improving the treatment of intractable epilepsy in response to AMPAR antagonists.

Clinical Course and Features of Seizures Associated With LGI1-Antibody Encephalitis

Objective:To determine risk factors associated with clinical relapses and development of chronic epilepsy in patients with anti-leucine-rich glioma-inactivated 1 (LGI1) IgG encephalitis.Methods:Patients with seizures related to LGI1-antibody encephalitis with ≥ 24 months of follow-up from disease onset were identified in the Mayo Clinic electronic medical record and Neuroimmunology lab records. Charts were reviewed to determine clinical factors, seizure types, imaging, treatment, occurrence of relapse, and outcome. Binary logistic regression analysis was performed to identify predictors of the development of chronic epilepsy. Univariate Cox proportional hazards regression was used to examine the influence of baseline characteristics on relapse risk.Results:Forty-nine patients with LGI1-antibody encephalitis and acute symptomatic seizures were identified. Almost all patients (n=48, 98%) were treated with immunotherapy. Eight had definite, and two had possible chronic epilepsy at last follow-up (10/49, 20.4%). Female sex (P=0.048) and younger age at disease onset (P=0.02) were associated with development of chronic epilepsy. Relapses occurred in 20 (40.8%), with a median time to first relapse of 7.5 months (range 3-94 months). Initial treatment with chronic steroid sparing immunotherapy was associated with reduced risk of relapse (hazards ratio=0.28, 95% CI 0.11-0.73, P=0.009).Conclusions:Chronic epilepsy occurred in 20.4% of our patients with LGI1-antibody encephalitis despite aggressive immunotherapy. Risk factors for chronic epilepsy were female sex and earlier age of onset. Relapses occurred in 40.8% of patients with prolonged follow-up, and chronic steroid sparing immunotherapy was associated with a lower relapse rate.

Ictal Occurrence of High-Frequency Oscillations Correlates With Seizure Severity in a Rat Model of Temporal Lobe Epilepsy

High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study, it was aimed to investigate whether the HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFOs were marked in 24 seizures during a preictal, ictal, and postictal EEG segment. The duration covered by the HFO during these different segments was analyzed and compared between mild and severe seizures. HFOs were significantly increased during ictal periods (p < 0.001) and significantly decreased during postictal periods (p < 0.03) compared to the ictal segment. Ictal ripples (p = 0.04) as well as fast ripples (p = 0.02) were significantly higher in severe seizures compared to mild seizures. The present study demonstrates that ictal HFO occurrence mirrors seizure severity in a chronic focal epilepsy model in rats. This is similar to recent observations in patients with refractory mesio-temporal lobe epilepsy. Moreover, postictal HFO decrease might reflect postictal inhibition of epileptic activity. Overall results provide additional evidence that HFOs can be used as biomarkers for measuring seizure severity in epilepsy.

CDDO-Me Attenuates Astroglial Autophagy via Nrf2-, ERK1/2-SP1- and Src-CK2-PTEN-PI3K/AKT-Mediated Signaling Pathways in the Hippocampus of Chronic Epilepsy Rats

Clasmatodendrosis is an autophagic astroglial death showing extensive swollen cell bodies with vacuoles and disintegrated/beaded processes. This astroglial degeneration is closely relevant to the synchronous epileptiform discharges. However, the underlying molecular mechanisms and the roles of clasmatodendrosis in spontaneous seizure activity are still unknown. The 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is one of the activators for nuclear factor-erythroid 2-related factor 2 (Nrf2) that is a redox-sensitive transcription factor. In the present study, we explored the effects of CDDO-Me on clasmatodendrosis in chronic epilepsy rats, which could prevent epilepsy-related complications. In the present study, clasmatodendritic astrocytes showed reduced Nrf2 expression and its nuclear accumulation, which were restored by CDDO-Me. CDDO-Me also abrogated heat shock protein 25 (HSP25) upregulation in clasmatodendritic astrocytes by regulating extracellular signal-related kinases 1/2 (ERK1/2)-specificity protein 1 (SP1)- and Src-casein kinase 2 (CK2)-phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-phosphatidylinositol-3-kinase (PI3K)-AKT-glycogen synthase kinase 3β (GSK3β)-bax-interacting factor 1 (Bif-1)-mediated signaling pathways in chronic epilepsy rats. In addition, CDDO-Me ameliorated spontaneous seizure duration, but not seizure frequency and behavioral seizure severity. Therefore, our findings suggest that clasmatodendrosis may affect seizure duration in chronic epilepsy rats, and that CDDO-Me may attenuate autophagic astroglial degeneration by regulating various signaling pathways.