Cholesterol 24-hydroxylase is a novel pharmacological target for anti-ictogenic and disease modification effects in epilepsy

Design and identification of brain-penetrant, potent, and selective 1,3-oxazole-based cholesterol 24-hydroxylase (CH24H) inhibitors

Azole-, pyridine-, and pyrimidine-based cytochrome P450 (CYP) inhibitors strongly bind to CYP enzymes through the coordination between the heme iron of CYP and the sp2-nitrogen atoms of heteroaromatic rings, providing potent pharmacological effects by inhibiting the initiation of the catalytic cycles of target CYP enzymes. Although imidazole-, 1,2,4-triazole-, pyridine-, and pyrimidine-based CYP inhibitors have been widely explored, 1,3-oxazole-based CYP inhibitors have received little attention. In this study, we designed and identified novel 1,3-oxazole-based inhibitors of cholesterol 24- hydroxylase (CH24H; CYP46A1), a brain-specific enzyme involved in cholesterol catabolism, to form 24S-hydroxycholesterol. Detailed insights into the CH24H-ligand interactions were provided by the crystal structures of 1,3-oxazole compounds, including high-throughput screening hit 2 and rationally designed inhibitor 3f. Optimization of 3f led to the identification of 1,3-oxazole derivative 4 l as a potent, selective, and brain-penetrable CH24H inhibitor that significantly reduced 24HC levels in the mouse brain. The design of 1,3-oxazole-based CYP inhibitors holds the potential for the discovery of novel inhibitors with significant potency against a broad spectrum of CYP enzymes.

The role of glutamate receptors and transporters in epilepsy: evidence from animal studies

Epilepsy encompasses a group of chronic brain disorders characterized by recurrent, hypersynchronous activity of neuronal clusters, with epileptic seizures being the primary manifestation of these disorders. The objective of epilepsy treatment is to prevent seizures with minimum adverse side effects. However, approximately 30 % of patients do not respond to available medications. One proposed mechanism of epileptogenesis is glutamate excitotoxicity. When released in excess or not appropriately removed from the synaptic cleft, glutamate hyperactivates receptors, causing a biochemical cascade, which culminates in seizures and cell death. The use of animal models is essential for uncovering potential epileptogenic pathways, understanding the role of receptors and transporters in excitotoxicity, and screening effective antiepileptic treatments. This review examines studies that investigate the role of glutamate transporters and receptors in excitotoxicity and epileptogenesis using animal models. For this, we searched through both PubMed/Medline and ScienceDirect databases. After applying the inclusion and exclusion criteria, 26 (twenty-six) studies were selected for analysis. The studies addressed key glutamate transporter family of excitatory amino acid transporters (EAATs) EAAT1, EAAT2, and EAAT3, responsible for glutamate clearance, as well as AMPA receptor subunits GluA1 and GluA2, NMDA receptor subunits GluN1, GluN2a, and GluN2b, and the metabotropic receptors mGluR5 and mGluR2/3. Results showed that the dysregulation of these transporters and receptors is associated to seizure induction and excitotoxic damage, pointing to their fundamental role in the mechanisms of excitotoxicity and epileptogenesis. These findings highlight the potential of targeting glutamate transporters and receptors to stabilize glutamate homeostasis as an intervention in epilepsy management.

Voluntary running wheel activity reduces seizure burden and affords neuroprotection in a mouse model of acquired epilepsy

OBJECTIVE

Physical exercise may improve neurological deficits and neuronal damage after acute brain injuries and decrease established seizures. We investigated whether voluntary running wheel (RW) activity affects epileptogenesis in a mouse model of acquired epilepsy compared to sedentary mice.

METHODS

Epilepsy was induced by intra-amygdala kainate causing status epilepticus (SE) in adult male mice. Sham mice were implanted with electrodes and injected with saline, and matched to experimental mice. In the RW-1 protocol, SE mice were trained to run for 5 weeks before SE induction and for 6 weeks thereafter. In the RW-2 protocol, mice began using RWs 24 h post-SE for 10 weeks. At the end of each protocol, electrocorticography (ECoG) was recorded for 2 weeks (24/7) in the absence of RWs. Matched sedentary mice were kept in home cages without RWs, subjected to SE, and had ECoG monitored. At the end of experiment, all mice were processed for assessing hippocampal neuronal cell loss (Nissl staining), hilar mossy cells (GLUR2/3 staining), and blood-brain barrier (BBB) damage (serum matrix metalloproteinase-9 [MMP-9] by enzyme-linked immunosorbent assay). Neuroinflammation (reverse-transcriptase quantitative polymerase chain reaction) and albumin level (western blot) were also measured in the hippocampus of RW1 mice 72 h post-SE, together with serum MMP-9.

RESULTS

RW activity in SE mice reduced the incidence of epilepsy (RW-1 by 38%; RW-2 by 54%, p < .05) and the total time spent in seizures (RW-1, p < .05; RW-2, p < .01) compared to sedentary mice. RW-1 SE mice showed reduced average seizure duration (p < .01), whereas RW-2 SE mice showed reduced number of seizures (p < .01). Reduction in seizure duration was associated with prevention of GluR2/3-positive mossy cell loss, which occurs in sedentary SE mice (p < .01 vs sham mice). Seizure duration in epileptic mice was negatively correlated with the number of hilar mossy cells (p < .01). Preventive RW-1 activity reduced SE duration and severity (p < .05) vs sedentary mice. Aberrant neurogenesis was reduced in the dentate gyrus of SE mice subjected to RWs (p < .01) vs sedentary mice. Serum MMP-9 and brain albumin levels were reduced in SE mice exposed to running activity (p < .05) compared to sedentary mice.

SIGNIFICANCE

Physical exercise reduced seizure burden and neuropathology in mice, offering a strategy to improve disease outcomes after acute brain injury.

Role of cholesterol in modulating brain hyperexcitability

Cholesterol is a critical molecule in the central nervous system, and imbalances in the synthesis and metabolism of brain cholesterol can result in a range of pathologies, including those related to hyperexcitability. The impact of cholesterol on disorders of epilepsy and developmental and epileptic encephalopathies is an area of growing interest. Cholesterol cannot cross the blood-brain barrier, and thus the brain synthesizes and metabolizes its own pool of cholesterol. The primary metabolic enzyme for brain cholesterol is cholesterol 24-hydroxylase (CH24H), which metabolizes cholesterol into 24S-hydroxycholesterol (24HC). Dysregulation of CH24H and 24HC can affect neuronal excitability through a range of mechanisms. 24HC is a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptors and can increase glutamate release via tumor necrosis factor-α-dependent pathways. Increasing cholesterol metabolism can lead to dysfunction of excitatory amino acid transporter 2 and impair glutamate reuptake. Finally, overstimulation of NMDA receptors can further activate metabolism of cholesterol, leading to a vicious cycle of overactivation. All of these mechanisms increase extracellular glutamate and can lead to hyperexcitability. For these reasons, the cholesterol pathway represents a new potential mechanistic target for antiseizure medications. CH24H inhibition has been shown to decrease seizure behavior and improve survival in multiple animal models of epilepsy and could be a promising new mechanism of action for the treatment of neuronal hyperexcitability and developmental and epileptic encephalopathies.

Characterization of soticlestat, a novel cholesterol 24-hydroxylase inhibitor, in acute and chronic neurodegeneration models

We investigated whether soticlestat (TAK-935), a newly discovered cholesterol 24-hydroxylase (CH24H) inhibitor now in phase 3 clinical trials for Dravet and Lennox-Gastaut syndromes, has effects on neurodegeneration in both chronic and acute animal models associated with glutamate hyperexcitation. Soticlestat was administered at doses that approximately halve 24S-hydroxycholesterol in both experiments. In the kainic acid (KA)-induced acute hippocampal degeneration model, soticlestat ameliorated inflammatory cytokine expression, hippocampal degeneration, and memory impairment. We ruled out the possibility that soticlestat directly interferes with KA binding to the KA receptor, or that 24S-hydroxycholesterol modulates KA receptor signaling, by conducting receptor binding and cell death assays. In the PS19 chronic degeneration model of tauopathy, treatment effects were observed in neurodegeneration markers. Notably, there was a significant correlation between the levels of brain 24S-hydroxycholesterol and a proinflammatory cytokine, tumor necrosis factor-α, which is implicated in cognitive decline and lowering of seizure threshold. This is the first study demonstrating that CH24H inhibition can alleviate neurodegeneration concomitant with neuroinflammation. Herein, we discuss the interplay among 24S-hydroxycholesterol production, neuroinflammation, and excitotoxicity. Effects on neurodegeneration and neuroinflammation demonstrated in two preclinical models suggest that soticlestat is effective in ameliorating seizures and addressing cognitive dysfunction in seizure disorders.

Innovative drug discovery strategies in epilepsy: integrating next-generation syndrome-specific mouse models to address pharmacoresistance and epileptogenesis

INTRODUCTION

Although there are numerous treatment options already available for epilepsy, over 30% of patients remain resistant to these antiseizure medications (ASMs). Historically, ASM discovery has relied on the demonstration of efficacy through the use of 'traditional' acute in vivo seizure models (e.g. maximal electroshock, subcutaneous pentylenetetrazol, and kindling). However, advances in genetic sequencing technologies and remaining medical needs for people with treatment-resistant epilepsy or special patient populations have encouraged recent efforts to identify novel compounds in syndrome-specific models of epilepsy. Syndrome-specific models, including Scn1a variant models of Dravet syndrome and APP/PS1 mice associated with familial early-onset Alzheimer's disease, have already led to the discovery of two mechanistically novel treatments for developmental and epileptic encephalopathies (DEEs), namely cannabidiol and soticlestat, respectively.

AREAS COVERED

In this review, the authors discuss how it is likely that next-generation drug discovery efforts for epilepsy will more comprehensively integrate syndrome-specific epilepsy models into early drug discovery providing the reader with their expert perspectives.

EXPERT OPINION

The percentage of patients with pharmacoresistant epilepsy has remained unchanged despite over 30 marketed ASMs. Consequently, there is a high unmet need to reinvent and revise discovery strategies to more effectively address the remaining needs of patients with specific epilepsy syndromes, including drug-resistant epilepsy and DEEs.

Withaferin A protects against epilepsy by promoting LCN2-mediated astrocyte polarization to stopping neuronal ferroptosis

BACKGROUND

Epilepsy is among the most frequent severe brain diseases, with few treatment options available. Neuronal ferroptosis is an important pathogenic mechanism in epilepsy. As a result, addressing ferroptosis appears to be a promising treatment approach for epilepsy. Withaferin A (WFA) is a C28 steroidal lactone that has a broad range of neuroprotective properties. Nonetheless, the antiepileptic action of WFA and the intrinsic mechanism by which it inhibits ferroptosis following epilepsy remain unknown.

PURPOSE

This study aimed at investigating to the antiepileptic potential of WFA in epilepsy, as well as to propose a potential therapeutic approach for epilepsy therapy.

METHODS

We conducted extensive research to examine the impacts of WFA on epilepsy and ferroptosis, using the kainic acid (KA)-treated primary astrocyte as an in vitro model and KA-induced temporal lobe epilepsy mice as an in vivo model. To analyze the neuroprotective effects of WFA on epileptic mice, electroencephalogram (EEG) recording, Nissl staining, and neurological function assessments such as the Morris water maze (MWM) test, Y-maze test, Elevated-plus maze (O-maze) test, and Open field test were used. Furthermore, the mechanism behind the neuroprotective effect of WFA in epilepsy was investigated using the transcriptomics analysis and verified on epileptic patient and epileptic mouse samples using Western blotting (WB) and immunofluorescence (IF) staining. In addition, WB, IF staining and specific antagonists/agonists were used to investigate astrocyte polarization and the regulatory signaling pathways involved. More critically, ferroptosis was assessed utilizing lipocalin-2 (LCN2) overexpression cell lines, siRNA knockdown, JC-1 staining, WB, IF staining, flow cytometry, electron microscopy (TEM), and ferroptosis-related GSH and MDA indicators.

RESULTS

In this study, we observed that WFA treatment reduced the number of recurrent seizures and time in seizure, and the loss of neurons in the hippocampal area in in epileptic mice, and even improved cognitive and anxiety impairment after epilepsy in a dose depend. Furthermore, WFA treatment was proven to enhance to the transformation of post-epileptic astrocytes from neurotoxic-type A1 to A2 astrocytes in both in vivo and in vitro experiments by inhibiting the phosphoinositide 3-kinase /AKT signaling pathway. At last, transcriptomics analysis in combination with functional experimental validation, it was discovered that WFA promoted astrocyte polarity transformation and then LCN2 in astrocytes, which inhibited neuronal ferroptosis to exert neuroprotective effects after epilepsy. In addition, we discovered significant astrocytic LCN2 expression in human TLE patient hippocampal samples.

CONCLUSIONS

Taken together, for the first, our findings suggest that WFA has neuroprotective benefits in epilepsy by modulating astrocyte polarization, and that LCN2 may be a novel potential target for the prevention and treatment of ferroptosis after epilepsy.

Phase 1 pharmacokinetic and safety study of soticlestat in participants with mild or moderate hepatic impairment or normal hepatic function

This phase 1, open-label, three-arm study (NCT05098054) compared the pharmacokinetics and safety of soticlestat (TAK-935) in participants with hepatic impairment. Participants aged ≥18 to <75 years had moderate (Child-Pugh B) or mild (Child-Pugh A) hepatic impairment or normal hepatic function (matched to hepatic-impaired participants by sex, age, and body mass index). Soticlestat was administered as a single oral 300 mg dose. Pharmacokinetic parameters of soticlestat and its metabolites TAK-935-G (M3) and M-I were assessed and compared by group. The incidence of treatment-emergent adverse events (TEAEs) and other safety parameters were also monitored. The pharmacokinetic analyses comprised 35 participants. Participants with moderate hepatic impairment had lower proportions of bound and higher proportions of unbound soticlestat than participants with mild hepatic impairment and normal hepatic function. Total plasma soticlestat pharmacokinetic parameters (maximum observed concentration [Cmax], area under the concentration-time curve from time 0 to time of last quantifiable concentration [AUClast], and AUC from time 0 to infinity [AUC∞]) were approximately 115%, 216%, and 199% higher with moderate and approximately 45%, 35%, and 30% higher with mild hepatic impairment, respectively, than healthy matched participants. Moderate hepatic impairment decreased the liver's ability to metabolize soticlestat to M-I; glucuronidation to M3 was also affected. Mild hepatic impairment resulted in a lower total plasma M-I exposure, but glucuronidation was unaffected. TEAEs were similar across study arms, mild, and no new safety findings were observed. A soticlestat dose reduction is required for individuals with moderate but not mild hepatic impairment.

Early treatment with rifaximin during epileptogenesis reverses gut alterations and reduces seizure duration in a mouse model of acquired epilepsy

The gut microbiota is altered in epilepsy and is emerging as a potential target for new therapies. We studied the effects of rifaximin, a gastrointestinal tract-specific antibiotic, on seizures and neuropathology and on alterations in the gut and its microbiota in a mouse model of temporal lobe epilepsy (TLE). Epilepsy was induced by intra-amygdala kainate injection causing status epilepticus (SE) in C57Bl6 adult male mice. Sham mice were injected with vehicle. Two cohorts of SE mice were fed a rifaximin-supplemented diet for 21 days, starting either at 24 h post-SE (early disease stage) or at day 51 post-SE (chronic disease stage). Corresponding groups of SE mice (one each disease stage) were fed a standard (control) diet. Cortical ECoG recording was done at each disease stage (24/7) for 21 days in all SE mice to measure the number and duration of spontaneous seizures during either rifaximin treatment or control diet. Then, epileptic mice ± rifaximin and respective sham mice were sacrificed and brain, gut and feces collected. Biospecimens were used for: (i) quantitative histological analysis of the gut structural and cellular components; (ii) markers of gut inflammation and intestinal barrier integrity by RTqPCR; (iii) 16S rRNA metagenomics analysis in feces. Hippocampal neuronal cell loss was assessed in epileptic mice killed in the early disease phase. Rifaximin administered for 21 days post-SE (early disease stage) reduced seizure duration (p < 0.01) and prevented hilar mossy cells loss in the hippocampus compared to epileptic mice fed a control diet. Epileptic mice fed a control diet showed a reduction of both villus height and villus height/crypt depth ratio (p < 0.01) and a decreased number of goblet cells (p < 0.01) in the duodenum, as well as increased macrophage (Iba1)-immunostaining in the jejunum (p < 0.05), compared to respective sham mice. Rifaximin's effect on seizures was associated with a reversal of gut structural and cellular changes, except for goblet cells which remained reduced. Seizure duration in epileptic mice was negatively correlated with the number of mossy cells (p < 0.01) and with villus height/crypt depth ratio (p < 0.05). Rifaximin-treated epileptic mice also showed increased tight junctions (occludin and ZO-1, p < 0.01) and decreased TNF mRNA expression (p < 0.01) in the duodenum compared to epileptic mice fed a control diet. Rifaximin administered for 21 days in chronic epileptic mice (chronic disease stage) did not change the number or duration of seizures compared to epileptic mice fed a control diet. Chronic epileptic mice fed a control diet showed an increased crypt depth (p < 0.05) and reduced villus height/crypt depth ratio (p < 0.01) compared to respective sham mice. Rifaximin treatment did not affect these intestinal changes. At both disease stages, rifaximin modified α- and β-diversity in epileptic and sham mice compared to respective mice fed a control diet. The microbiota composition in epileptic mice, as well as the effects of rifaximin at the phylum, family and genus levels, depended on the stage of the disease. During the early disease phase, the abundance of specific taxa was positively correlated with seizure duration in epileptic mice. In conclusion, gut-related alterations reflecting a dysfunctional state, occur during epilepsy development in a TLE mouse model. A short-term treatment with rifaximin during the early phase of the disease, reduced seizure duration and neuropathology, and reversed some intestinal changes, strengthening the therapeutic effects of gut-based therapies in epilepsy.

Oxysterols in Central and Peripheral Synaptic Communication

Cholesterol is a key molecule for synaptic transmission, and both central and peripheral synapses are cholesterol rich. During intense neuronal activity, a substantial portion of synaptic cholesterol can be oxidized by either enzymatic or non-enzymatic pathways to form oxysterols, which in turn modulate the activities of neurotransmitter receptors (e.g., NMDA and adrenergic receptors), signaling molecules (nitric oxide synthases, protein kinase C, liver X receptors), and synaptic vesicle cycling involved in neurotransmitters release. 24-Hydroxycholesterol, produced by neurons in the brain, could directly affect neighboring synapses and change neurotransmission. 27-Hydroxycholesterol, which can cross the blood-brain barrier, can alter both synaptogenesis and synaptic plasticity. Increased generation of 25-hydroxycholesterol by activated microglia and macrophages could link inflammatory processes to learning and neuronal regulation. Amyloids and oxidative stress can lead to an increase in the levels of ring-oxidized sterols and some of these oxysterols (4-cholesten-3-one, 5α-cholestan-3-one, 7β-hydroxycholesterol, 7-ketocholesterol) have a high potency to disturb or modulate neurotransmission at both the presynaptic and postsynaptic levels. Overall, oxysterols could be used as "molecular prototypes" for therapeutic approaches. Analogs of 24-hydroxycholesterol (SGE-301, SGE-550, SAGE718) can be used for correction of NMDA receptor hypofunction-related states, whereas inhibitors of cholesterol 24-hydroxylase, cholestane-3β,5α,6β-triol, and cholest-4-en-3-one oxime (olesoxime) can be utilized as potential anti-epileptic drugs and (or) protectors from excitotoxicity.

The potential of CYP46A1 as a novel therapeutic target for neurological disorders: An updated review of mechanisms

Cholesterol is a key component of the cell membrane that impacts the permeability, fluidity, and functions of membrane-bound proteins. It also participates in synaptogenesis, synaptic function, axonal growth, dendrite outgrowth, and microtubule stability. Cholesterol biosynthesis and metabolism are in balance in the brain. Its metabolism in the brain is mediated mainly by CYP46A1 or cholesterol 24-hydroxylase. It is responsible for eliminating about 80% of the cholesterol excess from the human brain. CYP46A1 converts cholesterol to 24S-hydroxycholesterol (24HC) that readily crosses the blood-brain barrier and reaches the liver for the final elimination process. Studies show that cholesterol and 24HC levels change during neurological diseases and conditions. So, it was hypothesized that inhibition or activation of CYP46A1 would be an effective therapeutic strategy. Accordingly, preclinical studies, using genetic and pharmacological interventions, assessed the role of CYP46A1 in main neurodegenerative disorders such as Parkinson's disease, Huntington's disease, Alzheimer's disease, multiple sclerosis, spinocerebellar ataxias, and amyotrophic lateral sclerosis. In addition, its role in seizures and brain injury was evaluated. The recent development of soticlestat, as a selective and potent CYP46A1 inhibitor, with significant anti-seizure effects in preclinical and clinical studies, suggests the importance of this target for future drug developments. Previous studies have shown that both activation and inhibition of CYP46A1 are of therapeutic value. This article, using recent studies, highlights the role of CYP46A1 in various brain diseases and insults.