The roles of ER stress in epilepsy: Molecular mechanisms and therapeutic implications

The first ER-targeting flavone-based fluorescent probe for Cys: Applications in real-time tracking in an epilepsy model and food analysis

Epilepsy is one of the most commonly-seen neurological disorders, and both endoplasmic reticulum stress (ERS) and oxidative stress (OS) have been demonstrated to be associated with epileptic seizures. As one of the three endogenous thiol-containing amino acids, cysteine (Cys) is recognized not only as an important biomarker of various biological processes but also widely used as a significant additive in the food industry. However, the exact role that Cys plays in ERS has not been well answered up to now. In this paper, we reported the first flavone-based fluorescent probe (namely BFC) with nice endoplasmic reticulum (ER)-targeting ability, which was capable of monitoring Cys in a fast response (3.0 min), large stokes shift (130 nm) and low detection limit (10.4 nM). The recognition mechanism of Cys could be attributed to the addition-cyclization reaction involving a Cys residue and an acrylate group, resulting in the release of the strong excited-state intramolecular proton transfer (ESIPT) emission molecule of benzoflavonol (BF). The low cytotoxicity and good biocompatibility of the probe BFC allowed for monitoring the fluctuation of endogenous Cys levels under both ERS and OS processes, as well as in zebrafish models of epilepsy. Quantitative determination of Cys with the probe BFC was also achieved in three different food samples. Additionally, a probe-immersed test strips integrated with a smartphone device was successfully constructed for on-site colorimetric detection of Cys. Undoubtedly, our work provided a valuable tool for tracking Cys levels in both an epilepsy model and real food samples.

Role of inflammasomes and neuroinflammation in epilepsy

Epilepsy is a brain disorder characterized by recurrent seizures, which are brief episodes of abnormal electrical activity in the brain and involuntary movement that can lead to physical injury and loss of consciousness. Seizures are canonically accompanied by increased inflammatory cytokine production that promotes neuroinflammation, brain pathology, and seizure propagation. Understanding the source of pro-inflammatory cytokines which promote seizure pathogenesis could be a gateway to precision epilepsy drug design. This review discusses the inflammasome in epilepsy including its role in seizure propagation and negative impacts on brain health. The inflammasome is a multiprotein complex that coordinates IL-1β and IL-18 production in response to tissue damage, cellular stress, and infection. Clinical evidence for inflammasome signaling in epileptogenesis is reviewed followed by a discussion of emerging strategies to modulate inflammasome activity in epilepsy.

Best1 mitigates ER stress induced by the increased cellular microenvironment stiffness in epilepsy

Changes in brain tissue stiffness are closely linked to the development and diseases of the nervous system. Endoplasmic reticulum (ER) stress plays a role in various pathological processes related to epilepsy. However, the relationship between stiffness changes, ER stress, and epilepsy remains unclear. This study aimed to investigate the impact of Best1 upregulation on alleviating ER stress and the underlying mechanism. Additionally, we proposed a protective strategy to prevent cell death resulting from ER stress in epilepsy. This study investigated the expression levels of ER stress-related proteins in epileptic tissues of varying stiffness. Atomic force microscopy revealed differences in stiffness across various lesion regions in patients with epilepsy. The expression levels of ECM and ER stress-related proteins were elevated in tissues with higher stiffness. Polypropionamide hydrogels were used to simulate extracellular matrix (ECM) with varying stiffness levels. Basal ER stress increased in the stiffer hydrogel substrates. Furthermore, the calcium-activated anion channel Bestrophin 1 (Best1) mitigated ER stress induced by both the stiffer substrate and thapsigargin. The loss-of-function mutations in Best1 inhibited this activity. The underlying mechanism involves the upregulation of the endosomal sorting complex required for the transport (ESCRT) components by Best1, which helps mitigate ER stress. These findings suggest that increased stiffness of the cellular microenvironment may contribute to neuronal death during epileptogenesis. Additionally, Best1 upregulation may serve as a protective strategy against excessive ER stress-induced neuronal damage in epilepsy.

The role of microRNAs regulation of endoplasmic reticulum stress in ischemia-reperfusion injury: A review

The endoplasmic reticulum (ER) is an important organelle in eukaryotic cells, responsible for a range of biological functions such as the secretion, modification and folding of proteins, maintaining Ca2+ homeostasis and the synthesis of steroids/lipids, secreted proteins and membrane proteins. When cells are affected by internal or external factors, including abnormal energy metabolism, disrupted Ca2+ balance, altered glycosylation, drug toxicity, and so on, the unfolded or misfolded proteins accumulate in the ER, leading to the unfolded protein response (UPR) and ER stress. The abnormal ER stress has been reported to be involved in various pathological processes. MicroRNAs (miRNAs) are non-coding RNAs with the length of approximately 19-25 nucleotides. They control the expression of multiple genes through posttranscriptional gene silencing in eukaryotes or some viruses. Increasing evidence indicates that miRNAs are involved in various cellular functions and biological processes, such as cell proliferation and differentiation, growth and development, and metabolic homeostasis. Hence, miRNAs participate in multiple pathological processes. Recently, many studies have shown that miRNAs play an important role by regulating ER stress in ischemia-reperfusion (I/R) injury, but the relevant mechanisms are not fully understood. In this review, we reviewed the current understanding of ER stress, as well as the biogenesis and function of miRNAs, and focused on the role of miRNAs regulation of ER stress in I/R injury, with the aim of providing new targets for the treatment of I/R injury.

Differential Gene Expression Associated with Idiopathic Epilepsy in Belgian Shepherd Dogs

BACKGROUND

Idiopathic epilepsy (IE) disproportionately affects Belgian shepherd dogs and although genomic risk markers have been identified previously in the breed, causative variants have not been described.

METHODS

The current study analyzed differences in whole blood RNA expression associated with IE and with a previously identified IE risk haplotype on canine chromosome (CFA) 14 using a transcriptomics RNA-seq approach.

RESULTS

MFSD2A and a likely pseudogene of RPL19, both of which are genes implicated in seizure activity, were upregulated in dogs with IE. Genes in the interferon signaling pathway were downregulated in Belgian shepherds with IE. The CFA14 risk haplotype was associated with upregulation of CLIC1, ACE2, and PIGN and downregulation of EPDR1, all known to be involved with epilepsy or the Wnt/β-catenin signaling pathway.

CONCLUSIONS

These results highlight the value of assessing gene expression in canine IE research to uncover genomic contributory factors.

NUS1 Variants Cause Lennox-Gastaut Syndrome Related to Unfolded Protein Reaction Activation

NUS1 encodes the Nogo-B receptor, a critical regulator for unfolded protein reaction (UPR) signaling. Although several loss-of-function variants of NUS1 have been identified in patients with developmental and epileptic encephalopathy (DEE), the role of the NUS1 variant in Lennox-Gastaut syndrome (LGS), a severe child-onset DEE, remains unknown. In this study, we identified two de novo variants of NUS1, a missense variant (c.868 C > T/p.R290C) and a splice site variant (c.792-2 A > G), in two unrelated LGS patients using trio-based whole-exome sequencing performed in a cohort of 165 LGS patients. Both variants were absent in the gnomAD population and showed a significantly higher observed number of variants than expected genome-wide. The R290C variant was predicted to damage NUS1 and decrease its protein stability. The c.792-2 A > G variant caused premature termination of the protein. Knockdown of NUS1 activated the UPR pathway, resulting in apoptosis of HEK293T cells. Supplementing cells with expression of wild-type NUS1, but not the mutant (R290C), rescued UPR activation and apoptosis in NUS1 knockdown cells. Compared to wild-type Drosophila, seizure-like behaviors and excitability in projection neurons were significantly increased in Tango14 (homolog of human NUS1) knockdown and Tango14R290C/+ knock-in Drosophila. Additionally, abnormal development and a small body size were observed in both mutants. Activated UPR signaling was also detected in both mutants. Thus, NUS1 is a causative gene for LGS with dominant inheritance. The pathogenicity of these variants is related to the UPR signaling activation, which may be a common pathogenic mechanism of DEE.

"Sigma-1 receptor modulation by clemastine highlights its repurposing as neuroprotective agent against seizures and cognitive deficits in PTZ-kindled rats"

Epilepsy is a neurological disorder characterized by recurrent spontaneous seizures alongside other neurological comorbidities. Cognitive impairment is the most frequent comorbidity secondary to progressive neurologic changes in epilepsy. Sigma 1 receptors (σ1 receptors) are involved in the neuroprotection and pathophysiology of both conditions and targeting these receptors may have the potential to modulate both seizures and comorbidities. The current research demonstrated the effect of clemastine (10 mg/kg, P.O.), a non-selective σ1 receptor agonist, on pentylenetetrazol (PTZ) (35 mg/kg, i.p., every 48 h for 14 doses)-kindling rats by acting on σ1 receptors through its anti-inflammatory/antioxidant capacity. Clemastine and phenytoin (30 mg/kg, P.O.) or their combination were given once daily. Clemastine treatment showed a significant effect on neurochemical, behavioural, and histopathological analyses through modulation of σ1 receptors. It protected the kindling animals from seizures and attenuated their cognitive impairment in the Morris water maze test by reversing the PTZ hippocampal neuroinflammation/oxidative stress state through a significant increase in inositol-requiring enzyme 1 (IRE1), x-box binding protein 1 (XBP1), along with a reduction of total reactive oxygen species (TROS) and amyloid beta protein (Aβ). The involvement of σ1 receptors in the protective effects of clemastine was confirmed by their abrogation when utilizing NE-100, a selective σ1 receptor antagonist. In light of our findings, modulating σ1 receptors emerges as a compelling therapeutic strategy for epilepsy and its associated cognitive impairments. The significant neuroprotective effects observed with clemastine underscore the potential of σ1 receptor-targeted treatments to address both the primary symptoms and comorbidities of neurological disorders.

A Ketogenic Diet may Improve Cognitive Function in Rats with Temporal Lobe Epilepsy by Regulating Endoplasmic Reticulum Stress and Synaptic Plasticity

A ketogenic diet (KD) is often used in the treatment of refractory epilepsy. Many studies have found that it also has a positive impact on cognitive comorbidities, but the specific mechanism remains unclear. In many disease models, endoplasmic reticulum stress (ERS) and synaptic plasticity is considered a new therapeutic target for improving cognitive impairment, and it has become a research focus in recent years. Recently, studies have found that a KD has a certain regulatory effect on both ERS and synaptic plasticity, but this result has not been confirmed in epilepsy. To investigate the effect of a KD on ERS and synaptic plasticity. In this study, a rat model of temporal lobe epilepsy (TLE) induced by lithium chloride-pilocarpine was used. After the model was successfully established, the rats in each group were fed a normal diet or a KD for 28 days, and the effect of a KD on the latency and seizure frequency of spontaneous recurrent seizures (SRSs) was observed via video monitoring. Subsequently, a Morris water maze was used to evaluate the spatial learning and memory abilities of the rats in each group; the ultrastructure of the ER and the synapses of the hippocampus were observed by transmission electron microscopy, and the dendritic spine density of the hippocampus was analysed by Golgi staining. Long-term potentiation (LTP) was used to detect the synaptic plasticity of the rats' hippocampi, and the expression of ERS-related proteins and synapse-related proteins was detected by Western blotting. A KD effectively reduced the frequency of SRSs in rats with TLE and improved their learning and memory impairment. Further investigations found that a KD inhibited the up-regulation of glucose-regulated protein 78, phospho-protein kinase-like ER kinase, phosphorylated α subunit of eukaryotic initiation factor 2, activating transcription factor 4 and C/EBP homologous protein expression in the hippocampi of rats with TLE and protected the ultrastructure of the neuronal ER, suggesting that a KD suppressed excessive ERS induced by epilepsy. Concurrently, we also found that a KD not only improved the synaptic ultrastructure and increased the density of dendritic spines in rats with TLE but also reversed the epilepsy-induced LTP deficit to some extent. More importantly, the expression of postsynaptic density protein 95, synaptotagmin-1 and synaptosomal-associated protein 25 in the hippocampi of rats with epilepsy was significantly increased after KD intervention. The study findings indicate that a KD improves learning and memory impairment in rats with epilepsy, possibly by regulating ERS and synaptic plasticity.

Endoplasmic reticulum stress and its role in various neurodegenerative diseases

The Endoplasmic reticulum (ER), a critical cellular organelle, maintains cellular homeostasis by regulating calcium levels and orchestrating essential functions such as protein synthesis, folding, and lipid production. A pivotal aspect of ER function is its role in protein quality control. When misfolded proteins accumulate within the ER due to factors like protein folding chaperone dysfunction, toxicity, oxidative stress, or inflammation, it triggers the Unfolded protein response (UPR). The UPR involves the activation of chaperones like calnexin, calreticulin, glucose-regulating protein 78 (GRP78), and Glucose-regulating protein 94 (GRP94), along with oxidoreductases like protein disulphide isomerases (PDIs). Cells employ the Endoplasmic reticulum-associated degradation (ERAD) mechanism to counteract protein misfolding. ERAD disruption causes the detachment of GRP78 from transmembrane proteins, initiating a cascade involving Inositol-requiring kinase/endoribonuclease 1 (IRE1), Activating transcription factor 6 (ATF6), and Protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathways. The accumulation and deposition of misfolded proteins within the cell are hallmarks of numerous neurodegenerative diseases. These aberrant proteins disrupt normal neuronal signalling and contribute to impaired cellular homeostasis, including oxidative stress and compromised protein degradation pathways. In essence, ER stress is defined as the cellular response to the accumulation of misfolded proteins in the endoplasmic reticulum, encompassing a series of signalling pathways and molecular events that aim to restore cellular homeostasis. This comprehensive review explores ER stress and its profound implications for the pathogenesis and progression of neurodegenerative diseases.

Sex differences in physiological response to increased neuronal excitability in a knockin mouse model of pediatric epilepsy

BACKGROUND

Epilepsy is a common neurological disease; however, few if any of the currently marketed antiseizure medications prevent or cure epilepsy. Discovery of pathological processes in the early stages of epileptogenesis has been challenging given the common use of preclinical models that induce seizures in physiologically normal animals. Moreover, despite known sex dimorphism in neurological diseases, females are rarely included in preclinical epilepsy models.

METHODS

We characterized sex differences in mice carrying a pathogenic knockin variant (p.N1768D) in the Scn8a gene that causes spontaneous tonic-clonic seizures (TCs) at ∼3 months of age and found that heterozygous females are more resilient than males in mortality and morbidity. To investigate the cellular mechanisms that underlie female resilience, we utilized blood-brain barrier (BBB) and hippocampal transcriptomic analyses in heterozygous mice before seizure onset (pre-TC) and in mice that experienced ∼20 TCs (post-TC).

RESULTS

In the pre-TC latent phase, both sexes exhibited leaky BBB; however, patterns of gene expression were sexually dimorphic. Females exhibited enhanced oxidative phosphorylation and protein biogenesis, while males activated gliosis and CREB signaling. After seizure onset (chronic phase), females exhibited a metabolic switch to lipid metabolism, while males exhibited increased gliosis and BBB dysfunction and a strong activation of neuroinflammatory pathways.

CONCLUSION

The results underscore the central role of oxidative stress and BBB permeability in the early stages of epileptogenesis, as well as sex dimorphism in response to increasing neuronal hyperexcitability. Our results also highlight the need to include both sexes in preclinical studies to effectively translate results of drug efficacy studies.

A forebrain-hypothalamic ER stress driven circuit mediates hepatic steatosis during obesity

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) affects 1 in 3 adults and contributes to advanced liver injury and cardiometabolic disease. While recent evidence points to involvement of the brain in NAFLD, the downstream neural circuits and neuronal molecular mechanisms involved in this response, remain unclear. Here, we investigated the role of a unique forebrain-hypothalamic circuit in NAFLD.

METHODS

Chemogenetic activation and inhibition of circumventricular subfornical organ (SFO) neurons that project to the paraventricular nucleus of the hypothalamus (PVN; SFO→PVN) in mice were used to study the role of SFO→PVN signaling in NAFLD. Novel scanning electron microscopy techniques, histological approaches, molecular biology techniques, and viral methodologies were further used to delineate the role of endoplasmic reticulum (ER) stress within this circuit in driving NAFLD.

RESULTS

In lean animals, acute chemogenetic activation of SFO→PVN neurons was sufficient to cause hepatic steatosis in a liver sympathetic nerve dependent manner. Conversely, inhibition of this forebrain-hypothalamic circuit rescued obesity-associated NAFLD. Furthermore, dietary NAFLD is associated with marked ER ultrastructural alterations and ER stress in the PVN, which was blunted following reductions in excitatory signaling from the SFO. Finally, selective inhibition of PVN ER stress reduced hepatic steatosis during obesity.

CONCLUSIONS

Collectively, these findings characterize a previously unrecognized forebrain-hypothalamic-ER stress circuit that is involved in hepatic steatosis, which may point to future therapeutic strategies for NAFLD.

Can endoplasmic reticulum stress observed in the PTZ-kindling model seizures be prevented with TUDCA and 4-PBA?

Epilepsy is a chronic neurological disease with recurrent seizures. Increasing evidence suggests that endoplasmic reticulum (ER) stress may play a role in the pathogenesis of epilepsy. We aimed to investigate the effects of Tauroursodeoxycholic acid (TUDCA) and 4-phenyl-butyric acid (4-PBA), which are known to suppress ER stress, on developed seizures in terms of markers of ER stress, oxidative stress, and apoptosis. The pentylenetetrazole (PTZ) kindling model was induced in Wistar albino rats (n = 48) by administering 35 mg/kg PTZ intraperitoneally (I.P.) every other day for 1 month. TUDCA and 4-PBA were administered via I.P. at a dose of 500 mg/kg dose. ER stress, apoptosis, and oxidative stress were determined in the hippocampus tissues of animals in all groups. Immunohistochemistry, qRT-PCR, ELISA, and Western Blot analyzes were performed to determine the efficacy of treatments. Expressions of ATF4, ATF6, p-JNK1/2, Cleaved-Kaspase3, and Caspase12 significantly increased in PTZ-kindled seizures compared to the control group. Increased NOX2 and MDA activity in the seizures were measured. In addition, stereology analyzes showed an increased neuronal loss in the PTZ-kindled group. qRT-PCR examination showed relative mRNA levels of CHOP. Accordingly, TUDCA and 4-PBA treatment suppressed the expressions of ATF4, ATF6, Cleaved-Caspase3, Kaspase12, NOX2, MDA, and CHOP in TUDCA + PTZ and 4-PBA + PTZ groups. ER stress-induced oxidative stress and apoptosis by reducing neuronal loss and degeneration were also preserved in these groups. Our data show molecularly that TUDCA and 4-PBA treatment can suppress the ER stress process in epileptic seizures.

The role of molecular chaperones in the mechanisms of epileptogenesis

Epilepsy is a group of neurological diseases which requires significant economic costs for the treatment and care of patients. The central point of epileptogenesis stems from the failure of synaptic signal transmission mechanisms, leading to excessive synchronous excitation of neurons and characteristic epileptic electroencephalogram activity, in typical cases being manifested as seizures and loss of consciousness. The causes of epilepsy are extremely diverse, which is one of the reasons for the complexity of selecting a treatment regimen for each individual case and the high frequency of pharmacoresistant cases. Therefore, the search for new drugs and methods of epilepsy treatment requires an advanced study of the molecular mechanisms of epileptogenesis. In this regard, the investigation of molecular chaperones as potential mediators of epileptogenesis seems promising because the chaperones are involved in the processing and regulation of the activity of many key proteins directly responsible for the generation of abnormal neuronal excitation in epilepsy. In this review, we try to systematize current data on the role of molecular chaperones in epileptogenesis and discuss the prospects for the use of chemical modulators of various chaperone groups' activity as promising antiepileptic drugs.

CPEB4-CLOCK crosstalk during temporal lobe epilepsy

OBJECTIVE

Posttranscriptional mechanisms are increasingly recognized as important contributors to the formation of hyperexcitable networks in epilepsy. Messenger RNA (mRNA) polyadenylation is a key regulatory mechanism governing protein expression by enhancing mRNA stability and translation. Previous studies have shown large-scale changes in mRNA polyadenylation in the hippocampus of mice during epilepsy development. The cytoplasmic polyadenylation element-binding protein CPEB4 was found to drive epilepsy-induced poly(A) tail changes, and mice lacking CPEB4 develop a more severe seizure and epilepsy phenotype. The mechanisms controlling CPEB4 function and the downstream pathways that influence the recurrence of spontaneous seizures in epilepsy remain poorly understood.

METHODS

Status epilepticus was induced in wild-type and CPEB4-deficient male mice via an intra-amygdala microinjection of kainic acid. CLOCK binding to the CPEB4 promoter was analyzed via chromatin immunoprecipitation assay and melatonin levels via high-performance liquid chromatography in plasma.

RESULTS

Here, we show increased binding of CLOCK to recognition sites in the CPEB4 promoter region during status epilepticus in mice and increased Cpeb4 mRNA levels in N2A cells overexpressing CLOCK. Bioinformatic analysis of CPEB4-dependent genes undergoing changes in their poly(A) tail during epilepsy found that genes involved in the regulation of circadian rhythms are particularly enriched. Clock transcripts displayed a longer poly(A) tail length in the hippocampus of mice post-status epilepticus and during epilepsy. Moreover, CLOCK expression was increased in the hippocampus in mice post-status epilepticus and during epilepsy, and in resected hippocampus and cortex of patients with drug-resistant temporal lobe epilepsy. Furthermore, CPEB4 is required for CLOCK expression after status epilepticus, with lower levels in CPEB4-deficient compared to wild-type mice. Last, CPEB4-deficient mice showed altered circadian function, including altered melatonin blood levels and altered clustering of spontaneous seizures during the day.

SIGNIFICANCE

Our results reveal a new positive transcriptional-translational feedback loop involving CPEB4 and CLOCK, which may contribute to the regulation of the sleep-wake cycle during epilepsy.

An allelic series of spontaneous Rorb mutant mice exhibit a gait phenotype, changes in retina morphology and behavior, and gene expression signatures associated with the unfolded protein response

The Retinoid-related orphan receptor beta (RORβ) gene encodes a developmental transcription factor and has 2 predominant isoforms created through alternative first exon usage; one specific to the retina and another present more broadly in the central nervous system, particularly regions involved in sensory processing. RORβ belongs to the nuclear receptor family and plays important roles in cell fate specification in the retina and cortical layer formation. In mice, loss of RORβ causes disorganized retina layers, postnatal degeneration, and production of immature cone photoreceptors. Hyperflexion or "high-stepping" of rear limbs caused by reduced presynaptic inhibition by Rorb-expressing inhibitory interneurons of the spinal cord is evident in RORβ-deficient mice. RORβ variants in patients are associated with susceptibility to various neurodevelopmental conditions, primarily generalized epilepsies, but including intellectual disability, bipolar, and autism spectrum disorders. The mechanisms by which RORβ variants confer susceptibility to these neurodevelopmental disorders are unknown but may involve aberrant neural circuit formation and hyperexcitability during development. Here we report an allelic series in 5 strains of spontaneous Rorb mutant mice with a high-stepping gait phenotype. We show retinal abnormalities in a subset of these mutants and demonstrate significant differences in various behavioral phenotypes related to cognition. Gene expression analyses in all 5 mutants reveal a shared over-representation of the unfolded protein response and pathways related to endoplasmic reticulum stress, suggesting a possible mechanism of susceptibility relevant to patients.

Sustained overexpression of spliced X-box-binding protein-1 in neurons leads to spontaneous seizures and sudden death in mice

The underlying etiologies of seizures are highly heterogeneous and remain incompletely understood. While studying the unfolded protein response (UPR) pathways in the brain, we unexpectedly discovered that transgenic mice (XBP1s-TG) expressing spliced X-box-binding protein-1 (Xbp1s), a key effector of UPR signaling, in forebrain excitatory neurons, rapidly develop neurologic deficits, most notably recurrent spontaneous seizures. This seizure phenotype begins around 8 days after Xbp1s transgene expression is induced in XBP1s-TG mice, and by approximately 14 days post induction, the seizures evolve into status epilepticus with nearly continuous seizure activity followed by sudden death. Animal death is likely due to severe seizures because the anticonvulsant valproic acid could significantly prolong the lives of XBP1s-TG mice. Mechanistically, our gene profiling analysis indicates that compared to control mice, XBP1s-TG mice exhibit 591 differentially regulated genes (mostly upregulated) in the brain, including several GABAA receptor genes that are notably downregulated. Finally, whole-cell patch clamp analysis reveals a significant reduction in both spontaneous and tonic GABAergic inhibitory responses in Xbp1s-expressing neurons. Taken together, our findings unravel a link between XBP1s signaling and seizure occurrence.

WGCNA combined with GSVA to explore biomarkers of refractory neocortical epilepsy

About two-thirds of epilepsy patients relapse within five years after surgery. It is significant to note that the limitations of current treatments stem from a lack of understanding of molecular mechanisms. In this study, Weighted Gene Co-expression Network Analysis (WGCNA) and Gene set variation analysis (GSVA) methods were used to analyze the total RNA data from 20 surgical removal samples (epileptogenic zone and irritative zone, EZ and IZ) of 10 Chinese patients with refractory neocortical epilepsy downloaded from the original microarray dataset (GSE31718) of the National Center for Biological Information -Gene Expression Omnibus database (NCBI-GEO). The late stages of the estrogen response pathway, the IL6-JAK-STAT3-signal pathway and G2 checkpoints are correlated with the EZ, whereas the early stages of the estrogen response pathway and TGF-β signal are more strongly expressed in the IZ. The allogeneic rejection, apical surface and the TGF-β signal are relevant to the high seizure frequency, the unfolded protein response and MYC-target are mostly expressed in patients with low-frequency seizures. Genes with high gene significance(GS) values that were correlated with seizure frequency include OSR2, CABP4, CAPSL, CYP4F8, and FRK in the pink module, and SH3GLB2, CHAC1 and DDX23 in the yellow module. The occurrence of EZ and IZ act on different biological mechanisms. The upregulated genes associated with seizure frequency include OSR2, CABP4, CAPSL, CYP4F8, and FRK, and the downregulated genes include SH3GLB2, CHAC1 and DDX23. The evidence of key genes and differential pathways obtained by WGCNA and GSVA may be biomarkers for novel preventive and pharmacological interventions in clinical practice.

•

The study listed different pathways between the epileptogenic zone and irritative zone.

•

The study listed different pathways between high seizure frequency and low seizure frequency.

•

The upregulated and downregulated genes associated with seizure frequency were identified.

4-Phenylbutyric Acid Plus Valproic Acid Exhibits the Therapeutic and Neuroprotective Effects in Acute Seizures Induced by Pentylenetetrazole

Endoplasmic reticulum (ER) stress and apoptosis are implicated in the pathogenesis of epilepsy. Here we examine the effects of valproic acid (VA) plus 4-phenylbutyric acid (4-PBA) on abnormal electrical brain activity, ER stress and apoptosis in acute seizures induced by pentylenetetrazole (PTZ). Forty male rats were randomly divided into five groups, each consisting of 8 rats as follows: Sham, PTZ, VA+PTZ, 4-PBA+PTZ, and VA plus 4-PBA+PTZ. The treated groups received VA, 4-PBA and VA plus 4-PBA by intraperitoneal application for 7 days prior to PTZ-induced seizure. On the 8th day, acute epileptic seizures were induced by PTZ (50 mg/kg, i.p.) injection, except for the sham group. Then, the seizure stage was observed and ECoG activities were recorded during the 30 min. At 24th post seizures, the hippocampus and blood samples were collected for biochemical and histopathological examinations. Administration of VA plus 4-PBA prior to PTZ-induced seizures significantly decreased seizure stage, the duration of generalized tonic-clonic seizure and the total number of spikes as increased the latency to the first myoclonic jerk when compared to the PTZ group. 4-PBA suppressed the increased levels of ER stress markers GRP78 and CHOP in the hippocampus. VA plus 4-PBA treatment before seizures significantly inhibited PTZ-induced elevations of apoptosis-related indicators caspase-3 and caspase-12, and significantly reduced the number of histopathological lesions of the hippocampus region at 24th post seizures. These findings suggest that administration of VA plus 4-PBA prior to PTZ-induced seizures may be involved in the neuroprotective potential of these agents for seizures.

Nedd4-2 Haploinsufficiency in Mice Impairs the Ubiquitination of Rer1 and Increases the Susceptibility to Endoplasmic Reticulum Stress and Seizures

Neural precursor cell expressed developmentally downregulated gene 4-like (NEDD4-2) is an epilepsy-associated gene encoding an E3 ligase that ubiquitinates neuroactive substrates. An involvement of NEDD4-2 in endoplasmic reticulum (ER) stress has been recently found with mechanisms needing further investigations. Herein, Nedd4-2+/− mice were found intolerant to thapsigargin (Tg) to develop ER stress in the brain. Pretreatment of Tg aggravated the pentylenetetrazole (PTZ)-induced seizures. Retention in endoplasmic reticulum 1 (Rer1), an ER retrieval receptor, was upregulated through impaired ubiquitination in Nedd4-2+/− mouse brain. Nedd4-2 interacted with Rer1 more strongly in mice with Tg administration. The negative regulation and NEDD4-2-mediated ubiquitination on RER1 were evaluated in cultured neurocytes and gliacytes by NEDD4-2 knockdown and overexpression. NEDD4-2 interacted with RER1 at higher levels in the cells with Tg treatment. Disruption of the 36STPY39 motif of RER1 attenuated the interaction with NEDD4-2, and the ubiquitinated RER1 underwent proteasomal degradation. Furthermore, the interactome of Rer1 was screened by immunoprecipitation-mass spectrometry in PTZ-induced mouse hippocampus, showing multiple potential ER retrieval cargoes that mediate neuroexcitability. The α1 subunit of the GABAA receptor was validated to interact with Rer1 and retain in ER more heavily in Nedd4-2+/− mouse brain by Endo-H digestion. In conclusion, Nedd4-2 deficiency in mice showed impaired ubiquitination of Rer1 and increased ER stress and seizures. These data indicate a protective effect of NEDD4-2 in ER stress and seizures possibly via RER1. We also provided potential ER retention cargoes of Rer1 awaiting further investigation.

Disruption of the Ubiquitin-Proteasome System and Elevated Endoplasmic Reticulum Stress in Epilepsy

The epilepsies are a broad group of conditions characterized by repeated seizures, and together are one of the most common neurological disorders. Additionally, epilepsy is comorbid with many neurological disorders, including lysosomal storage diseases, syndromic intellectual disability, and autism spectrum disorder. Despite the prevalence, treatments are still unsatisfactory: approximately 30% of epileptic patients do not adequately respond to existing therapeutics, which primarily target ion channels. Therefore, new therapeutic approaches are needed. Disturbed proteostasis is an emerging mechanism in epilepsy, with profound effects on neuronal health and function. Proteostasis, the dynamic balance of protein synthesis and degradation, can be directly disrupted by epilepsy-associated mutations in various components of the ubiquitin-proteasome system (UPS), or impairments can be secondary to seizure activity or misfolded proteins. Endoplasmic reticulum (ER) stress can arise from failed proteostasis and result in neuronal death. In light of this, several treatment modalities that modify components of proteostasis have shown promise in the management of neurological disorders. These include chemical chaperones to assist proper folding of proteins, inhibitors of overly active protein degradation, and enhancers of endogenous proteolytic pathways, such as the UPS. This review summarizes recent work on the pathomechanisms of abnormal protein folding and degradation in epilepsy, as well as treatment developments targeting this area.

The ER Stress/UPR Axis in Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

Cellular protein homeostasis in the lungs is constantly disrupted by recurrent exposure to various external and internal stressors, which may cause considerable protein secretion pressure on the endoplasmic reticulum (ER), resulting in the survival and differentiation of these cell types to meet the increased functional demands. Cells are able to induce a highly conserved adaptive mechanism, known as the unfolded protein response (UPR), to manage such stresses. UPR dysregulation and ER stress are involved in numerous human illnesses, such as metabolic syndrome, fibrotic diseases, and neurodegeneration, and cancer. Therefore, effective and specific compounds targeting the UPR pathway are being considered as potential therapies. This review focuses on the impact of both external and internal stressors on the ER in idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) and discusses the role of the UPR signaling pathway activation in the control of cellular damage and specifically highlights the potential involvement of non-coding RNAs in COPD. Summaries of pathogenic mechanisms associated with the ER stress/UPR axis contributing to IPF and COPD, and promising pharmacological intervention strategies, are also presented.