Truncated Neogenin Promotes Hippocampal Neuronal Death after Acute Seizure

Scorpion venom heat-resistant synthesized peptide ameliorates epileptic seizures and imparts neuroprotection in rats mediated by NMDA receptors

Finding new and effective natural products for designing antiepileptic drugs is highly important in the scientific community. The scorpion venom heat-resistant peptide (SVHRP) was purified from Buthus martensii Karsch scorpion venom, and subsequent analysis of the amino acid sequence facilitated the synthesis of a peptide known as scorpion venom heat-resistant synthesis peptide (SVHRSP) using a technique for peptide synthesis. Previous studies have demonstrated that the SVHRSP can inhibit neuroinflammation and provide neuroprotection. This study aimed to investigate the antiepileptic effect of SVHRSP on both acute and chronic kindling seizure models by inducing seizures in male rats through intraperitoneal administration of pentylenetetrazole (PTZ). Additionally, an N-methyl-D-aspartate (NMDA)-induced neuronal injury model was used to observe the anti-excitotoxic effect of SVHRSP in vitro. Our findings showed that treatment with SVHRSP effectively alleviated seizure severity, prolonged latency, and attenuated neuronal loss and glial cell activation. It also demonstrated the prevention of alterations in the expression levels of NMDA receptor subunits and phosphorylated p38 MAPK protein, as well as an improvement in spatial reference memory impairment during Morris water maze (MWM) testing in PTZ-kindled rats. In vitro experiments further revealed that SVHRSP was capable of attenuating neuronal action potential firing, inhibiting NMDA receptor currents and intracellular calcium overload, and reducing neuronal injury. These results suggest that the antiepileptic and neuroprotective effects of SVHRSP may be mediated through the regulation of NMDA receptor function and expression. This study provides new insight into therapeutic strategies for epilepsy.

Licochalcone A attenuates NMDA-induced neurotoxicity

This study investigates the effect of Licochalcone A (Lico-A), a flavonoid from licorice roots known for its anti-inflammatory, anti-cancer, and antioxidant properties, on NMDA-induced neurotoxicity in primary cultured rat hippocampal neurons. The study measured cell survival following NMDA and Lico-A exposure, revealing that Lico-A at a 2.5 μg/ml significantly improved cell viability, countering the detrimental effects of NMDA. The study also analyzed synaptic changes by examining both postsynaptic density 95 (PSD95) and synaptophysin-targeted imaging, showing that Lico-A treatment resulted in a significant increase in synaptic puncta, contrasting with the reduction observed under NMDA exposure. Furthermore, levels of phosphorylated mixed lineage kinase domain-like pseudokinase (P-MLKL) and phosphorylated receptor-interacting serine/threonine-protein kinase 3 (P-RIP3), key necroptosis regulators, were measured using Western blotting. The results showed an increase in P-MLKL and P-RIP3 in neurons exposed to NMDA, which was reduced following Lico-A treatment. The response of astrocyte and microglia was also evaluated by immunostaining for glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor molecule 1 (IBA-1) and tumor necrosis factor alpha (TNF-α). These markers exhibited heightened expression in the NMDA group, which was substantially reduced by Lico-A treatment. These findings suggest that Lico-A has neuroprotective effects against NMDA-induced neurotoxicity, potentially contributing to synaptic preservation, inhibition of neuronal necroptosis, and modulation of glial activation. Therefore, Lico-A shows promise as a neuroprotective agent for conditions associated with NMDA-related neurotoxicity.

Role of Necroptosis, a Regulated Cell Death, in Seizure and Epilepsy

Epilepsy is a chronic neurological disease that is characterized by spontaneous and recurrent seizures. Regulated cell death is a controlled process and has been shown to be involved in neurodegenerative diseases. Necroptosis is a type of regulated cell death, and its association with epilepsy has been documented. Necroptosis signaling can be divided into two pathways: canonical and non-canonical pathways. Inhibition of caspase-8, dimerization of receptor-interacting protein kinase 1 (RIP1) and RIP3, activation of mixed-lineage kinase domain-like protein (MLKL), movement of MLKL to the plasma membrane, and cell rupture occurred in these pathways. Through literature review, it has been revealed that there is a relationship between seizure, neuroinflammation, and oxidative stress. The seizure activity triggers the activation of various pathways within the central nervous system, including TNF-α/matrix metalloproteases, Neogenin and Calpain/ Jun N-terminal Kinase 1, which result in distinct responses in the brain. These responses involve the activation of neurons and astrocytes, consequently leading to an increase in the expression levels of proteins and genes such as RIP1, RIP3, and MLKL in a time-dependent manner in regions such as the hippocampus (CA1, CA3, dentate gyrus, and hilus), piriform cortex, and amygdala. Furthermore, the imbalance in calcium ions, depletion of adenosine triphosphate, and elevation of extracellular glutamate and potassium within these pathways lead to the progression of necroptosis, a reduction in seizure threshold, and increased susceptibility to epilepsy. Therefore, it is plausible that therapeutic targeting of these pathways could potentially provide a promising approach for managing seizures and epilepsy.

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.

Interleukin-17A Mediates Hippocampal Damage and Aberrant Neurogenesis Contributing to Epilepsy-Associated Anxiety

Anxiety disorder is one of the most common comorbidities in temporal lobe epilepsy (TLE), but its neurobiological mechanisms remain unclear. Here we identified a novel target, interleukin-17A (IL-17A), which can contribute to TLE-associated anxiety. Epileptic seizures were induced in 6-week-old IL-17A wild-type (WT) and knockout (KO) mice by pilocarpine injection. To evaluate anxiety level, we subjected mice to open field and elevated plus maze (EPM) tests and measured the time animals spent in center zone or open arms. Epileptic IL-17A WT mice showed thigmotaxis and reluctance to stay in open arms, whereas IL-17A KO mice spent more time in the center area and open arms, suggesting alleviated anxiety in epilepsy. Histological assessments revealed that hippocampal neuronal death as evaluated by Fluoro-Jade B staining was significantly reduced in IL-17A KO mice. Moreover, at 6 weeks after pilocarpine-induced status epilepticus, the number of hilar ectopic granule cells was also markedly decreased by IL-17A deficiency without a difference in the proliferation of neural progenitors or the generation of newborn neurons in the dentate gyrus. Taken together, our data demonstrated that IL-17A deletion mitigates TLE-associated anxiety behavior, possibly via the hippocampal neuroprotection and the reduction of seizure-induced aberrant neurogenesis.