In silico screening for clinical efficacy of antiseizure medications: Not all central nervous system drugs are alike

Challenges in Batch-to-Bed Translation Involving Inflammation-Targeting Compounds in Chronic Epilepsy: The Case of Cathepsin Activity-Based Probes

Our goal was to test the feasibility of a new theranostic strategy in chronic epilepsy by targeting cathepsin function using novel cathepsin activity-based probes (ABPs). We assessed the biodistribution of fluorescent cathepsin ABPs in vivo, in vitro, and ex vivo, in rodents with pilocarpine-induced chronic epilepsy and naïve controls, in human epileptic tissue, and in the myeloid cell lines RAW 264.7 (monocytes) and BV2 (microglia). Distribution and localization of ABPs were studied by fluorescence scanning, immunoblotting, microscopy, and cross-section staining in anesthetized animals, in their harvested organs, in brain tissue slices, and in vitro. Blood-brain-barrier (BBB) efflux transport was evaluated in transporter-overexpressing MDCK cells and using an ATPase activation assay. Although the in vivo biodistribution of ABPs to both naïve and epileptic hippocampi was negligible, ex vivo ABPs bound cathepsins preferentially within epileptogenic brain tissue and colocalized with neuronal but not myeloid cell markers. Thus, our cathepsin ABPs are less likely to be of major clinical value in the diagnosis of chronic epilepsy, but they may prove to be of value in intraoperative settings and in CNS conditions with leakier BBB or higher cathepsin activity, such as status epilepticus.

Placental disposition of cannabidiol: An ex vivo perfusion study

OBJECTIVE

In the absence of safety data in humans, the use of cannabidiol (CBD) is not recommended during pregnancy. Yet >50% of pregnancies in women with epilepsy are unintended, making fetal exposure to CBD possible. As a small-molecule, highly lipid-soluble drug, CBD is likely to be distributed into the placenta and cross it. To estimate the placental distribution profile of CBD and its potential short-term placental effects, we conducted an ex vivo perfusion study in human placentas.

METHODS

Placentas were obtained from healthy women undergoing cesarean deliveries. Selected cotyledons were cannulated and perfused for 180 min with a CBD-containing medium (250 ng/mL, .796 μmol·L-1 ; representative of a low therapeutic concentration; n = 8). CBD concentrations were determined at 180 min in the medium and placental tissue using liquid chromatography-tandem mass spectrometry. A customized gene panel array was used to analyze the expression of selected genes in the perfused placental cotyledons as well as in placentas perfused with 1000 ng/mL CBD (3.18 μmol·L-1 ; high therapeutic concentration; n = 8) and in those exposed to the vehicle.

RESULTS

CBD was sequestered in the placental tissue, exhibiting significant variability across samples (median = 5342 ng/g tissue, range = 1066-9351 ng/g tissue). CBD concentrations in the fetal compartment were one fifth of those measured in the maternal compartment (median = 59 ng/mL, range = 48-72 ng/mL vs. 280 = ng/mL, range = 159-388 ng/mL, respectively; p < .01). Placental gene expression was not significantly altered by CBD.

SIGNIFICANCE

The placenta acts as a depot compartment for CBD, slowing down its distribution to the fetus. This phenomenon might yield flatter but prolonged fetal CBD levels in vivo. The attenuated transplacental CBD transfer does not imply that its use by pregnant women is safe for the fetus. Only pregnancy registries and neurocognitive assessments would establish the risk of being antenatally exposed to CBD.

A Postictal Traffic Jam

Seizure-Induced Neutrophil Adhesion in Brain Capillaries Leads to a Decrease in Postictal Cerebral Blood Flow Lim H-K, Bae S, Han K, Kang B-M, Jeong Y, Kim S-G, Suh M. iScience . 2023;26(5):106655. doi:10.1016/j.isci.2023.106655 Cerebral hypoperfusion has been proposed as a potential cause of postictal neurological dysfunction in epilepsy, but its underlying mechanism is still unclear. We show that a 30% reduction in postictal cerebral blood flow (CBF) has two contributing factors: the early hypoperfusion up to ∼30 min post-seizure was mainly induced by arteriolar constriction, while the hypoperfusion that persisted for over an hour was due to increased capillary stalling induced by neutrophil adhesion to brain capillaries, decreased red blood cell (RBC) flow accompanied by constriction of capillaries and venules, and elevated intercellular adhesion molecule-1 (ICAM-1) expression. Administration of antibodies against the neutrophil marker Ly6G and against LFA-1, which mediates adhesive interactions with ICAM-1, prevented neutrophil adhesion and recovered the prolonged CBF reductions to control levels. Our findings provide evidence that seizure-induced neutrophil adhesion to cerebral microvessels via ICAM-1 leads to prolonged postictal hypoperfusion, which may underlie neurological dysfunction in epilepsy.

Epilepsy: Mitochondrial connections to the 'Sacred' disease

Over 65 million people suffer from recurrent, unprovoked seizures. The lack of validated biomarkers specific for myriad forms of epilepsy makes diagnosis challenging. Diagnosis and monitoring of childhood epilepsy add to the need for non-invasive biomarkers, especially when evaluating antiseizure medications. Although underlying mechanisms of epileptogenesis are not fully understood, evidence for mitochondrial involvement is substantial. Seizures affect 35%-60% of patients diagnosed with mitochondrial diseases. Mitochondrial dysfunction is pathophysiological in various epilepsies, including those of non-mitochondrial origin. Decreased ATP production caused by malfunctioning brain cell mitochondria leads to altered neuronal bioenergetics, metabolism and neurological complications, including seizures. Iron-dependent lipid peroxidation initiates ferroptosis, a cell death pathway that aligns with altered mitochondrial bioenergetics, metabolism and morphology found in neurodegenerative diseases (NDDs). Studies in mouse genetic models with seizure phenotypes where the function of an essential selenoprotein (GPX4) is targeted suggest roles for ferroptosis in epilepsy. GPX4 is pivotal in NDDs, where selenium protects interneurons from ferroptosis. Selenium is an essential central nervous system micronutrient and trace element. Low serum concentrations of selenium and other trace elements and minerals, including iron, are noted in diagnosing childhood epilepsy. Selenium supplements alleviate intractable seizures in children with reduced GPX activity. Copper and cuproptosis, like iron and ferroptosis, link to mitochondria and NDDs. Connecting these mechanistic pathways to selenoproteins provides new insights into treating seizures, pointing to using medicines including prodrugs of lipoic acid to treat epilepsy and to potential alternative therapeutic approaches including transcranial magnetic stimulation (transcranial), photobiomodulation and vagus nerve stimulation.

An Electric Light Orchestra in the Brain: Optogenetics for Controlling Seizures via Modulation of Astrocyte Activity

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