Astaxanthin protects against kainic acid-induced seizures and pathological consequences

Inhibition of Synaptic Glutamate Exocytosis and Prevention of Glutamate Neurotoxicity by Eupatilin from Artemisia argyi in the Rat Cortex

The inhibition of synaptic glutamate release to maintain glutamate homeostasis contributes to the alleviation of neuronal cell injury, and accumulating evidence suggests that natural products can repress glutamate levels and associated excitotoxicity. In this study, we investigated whether eupatilin, a constituent of Artemisia argyi, affected glutamate release in rat cortical nerve terminals (synaptosomes). Additionally, we evaluated the effect of eupatilin in an animal model of kainic acid (KA) excitotoxicity, particularly on the levels of glutamate and N-methyl-D-aspartate (NMDA) receptor subunits (GluN2A and GluN2B). We found that eupatilin decreased depolarization-evoked glutamate release from rat cortical synaptosomes and that this effect was accompanied by a reduction in cytosolic Ca2+ elevation, inhibition of P/Q-type Ca2+ channels, decreased synapsin I Ca2+-dependent phosphorylation and no detectable effect on the membrane potential. In a KA-induced glutamate excitotoxicity rat model, the administration of eupatilin before KA administration prevented neuronal cell degeneration, glutamate elevation, glutamate-generating enzyme glutaminase increase, excitatory amino acid transporter (EAAT) decrease, GluN2A protein decrease and GluN2B protein increase in the rat cortex. Taken together, the results suggest that eupatilin depresses glutamate exocytosis from cerebrocortical synaptosomes by decreasing P/Q-type Ca2+ channels and synapsin I phosphorylation and alleviates glutamate excitotoxicity caused by KA by preventing glutamatergic alterations in the rat cortex. Thus, this study suggests that eupatilin can be considered a potential therapeutic agent in the treatment of brain impairment associated with glutamate excitotoxicity.

Astaxanthin Protection against Neuronal Excitotoxicity via Glutamate Receptor Inhibition and Improvement of Mitochondrial Function

Excitotoxicity is known to associate with neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Amyotrophic lateral sclerosis and Huntington’s disease, as well as aging, stroke, trauma, ischemia and epilepsy. Excessive release of glutamate, overactivation of glutamate receptors, calcium overload, mitochondrial dysfunction and excessive reactive oxygen species (ROS) formation are a few of the suggested key mechanisms. Astaxanthin (AST), a carotenoid, is known to act as an antioxidant and protect neurons from excitotoxic injuries. However, the exact molecular mechanism of AST neuroprotection is not clear. Thus, in this study, we investigated the role of AST in neuroprotection in excitotoxicity. We utilized primary cortical neuronal culture and live cell fluorescence imaging for the study. Our results suggest that AST prevents neuronal death, reduces ROS formation and decreases the abnormal mitochondrial membrane depolarization induced by excitotoxic glutamate insult. Additionally, AST modulates intracellular calcium levels by inhibiting peak and irreversible secondary sustained calcium levels in neurons. Furthermore, AST regulates the ionotropic glutamate subtype receptors NMDA, AMPA, KA and mitochondrial calcium. Moreover, AST decreases NMDA and AMPA receptor protein expression levels, while KA remains unaffected. Overall, our results indicate that AST protects neurons from excitotoxic neuronal injury by regulating ionotropic glutamate receptors, cytosolic secondary calcium rise and mitochondrial calcium buffering. Hence, AST could be a promising therapeutic agent against excitotoxic insults in neurodegenerative diseases.

Mechanism of cell death pathways in status epilepticus and related therapeutic agents

The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.

Dietary astaxanthin: an excellent carotenoid with multiple health benefits

Astaxanthin is a carotenoid widely found in marine organisms and microorganisms. With extensive use in nutraceuticals, cosmetics, and animal feed, astaxanthin will have the largest share in the global market for carotenoids in the near future. Owing to its unique molecular features, astaxanthin has excellent antioxidant activity and holds promise for use in biochemical studies. This review focuses on the observed health benefits of dietary astaxanthin, as well as its underlying bioactivity mechanisms. Recent studies have increased our understanding of the role of isomerization and esterification in the structure-function relationship of dietary astaxanthin. Gut microbiota may involve the fate of astaxanthin during digestion and absorption; thus, further knowledge is needed to establish accurate recommendations for dietary intake of both healthy and special populations. Associated with the regulation of redox balance and multiple biological mechanisms, astaxanthin is proposed to affect oxidative stress, inflammation, cell death, and lipid metabolism in humans, thus exerting benefits for skin condition, eye health, cardiovascular system, neurological function, exercise performance, and immune response. Additionally, preclinical trials predict its potential effects such as intestinal flora regulation and anti-diabetic activity. Therefore, astaxanthin is worthy of further investigation for boosting human health, and wide applications in the food industry.

The potential antiepileptic activity of astaxanthin in epileptic rats treated with valproic acid

Objectives

Epilepsy is a neurological disease characterized by sudden, abnormal, and hyper- discharges in the central nervous system (CNS). Valproic acid (VPA) is commonly used as a broad-spectrum antiepileptic therapeutic. However, in many cases, patients develop resistance to VPA treatment due to overwhelming oxidative stress, which in turn might be a major catalyst for disease progression. Therefore, antioxidants can potentially become therapeutic agents by counteracting reactive oxygen species (ROS)-mediated damage. The present study is aimed to evaluate the potential antiepileptic effect of astaxanthin (ASTA) in pentylenetetrazol (PTZ) induced epileptic model rats that are chronically treated with VPA for 8 weeks.

Method

Fifty-male Wistar rats were randomly divided into five groups: Non-PTZ group, PTZ, PTZ/VPA, PTZ/ASTA, and PTZ/VPA/ASTA treated groups.

Results

PTZ/VPA treated group showed a neuroprotective effect with improvement in antioxidant levels, behavioral test, and histopathological changes induced by PTZ. VPA also exhibited an anti-inflammatory effect as its treatment resulted in the reduction of tumor necrosis factor-α (TNF-α). ASTA exhibited an anticonvulsant effect and enhanced anti-inflammatory effect as compared to VPA. During the combined therapy, ASTA potentiated the antiepileptic effect of the VPA by reducing the oxidative stress and TNF-α as well as increased the glutathione (GSH) levels. Also, there were substantial improvements in the behavioral and histopathological changes in the VPA/ASTA treated group as compared to the VPA treated group.

Conclusion

ASTA could have an antiepileptic and anti-inflammatory effect by reducing ROS generation. Therefore, co-administration of both the therapeutics (VPA/ASTA) has a synergistic effect in treating epilepsy and could potentially minimize recurrence and/or exacerbation of seizures.

Histopathological and Biochemical Assessment of Neuroprotective Effects of Sodium Valproate and Lutein on the Pilocarpine Albino Rat Model of Epilepsy

Epilepsy is one of the most frequent neurological disorders characterized by an enduring predisposition to generate epileptic seizures. Oxidative stress is believed to directly participate in the pathways of neurodegenerations leading to epilepsy. Approximately, one-third of the epileptic patients who suffer from seizures do not receive effective medical treatment. Sodium valproate (SVP) is a commonly used antiepileptic drug (AED); however, it has toxic effects. Lutein (L), a carotenoid, has potent antioxidant and anti-inflammatory properties. The aim of this study was to determine the neuroprotective effect of sodium valproate (SVP) and lutein (L) in a rat model of pilocarpine- (PLC-) induced epilepsy. To achieve this aim, fifty rats were randomly divided into five groups. Group I: control, group II: received PLC (400 mg/kg intraperitoneally), group III: received PLC + SVP (500 mg/kg orally), group IV: received PLC + SVP + L (100 mg/kg orally), and group V: received (PLC + L). Racine Scale (RC) and latency period to onset seizure were calculated. After eight weeks, the hippocampus rotarod performance and histological investigations were performed. Oxidative stress was investigated in hippocampal homogenates. Results revealed that SVP and L, given alone or in combination, reduced the RC significantly, a significant delay in latency to PLC-kindling onset, and improved rotarod performance of rats compared with the PLC group. Moreover, L was associated with a reduction of oxidative stress in hippocampal homogenate, a significant decrease in serum tumor necrosis factor-alpha (TNF-α) level, and inhibition of cerebral injury and displayed antiepileptic properties in the PLC-induced epileptic rat model. Data obtained from the current research elucidated the prominent neuroprotective, antioxidant, and anti-inflammatory activities of lutein in this model. In conclusion, lutein cotreatment with AEDs is likely to be a promising strategy to improve treatment efficacy in patients suffering from epilepsy.

Asiatic Acid Prevents Cognitive Deficits by Inhibiting Calpain Activation and Preserving Synaptic and Mitochondrial Function in Rats with Kainic Acid-Induced Seizure

Cognitive impairment is not only associated with seizures but also reported as an adverse effect of antiepileptic drugs. Thus, new molecules that can ameliorate seizures and maintain satisfactory cognitive function should be developed. The antiepileptic potential of asiatic acid, a triterpene derived from the medicinal herb Centella asiatica, has already been demonstrated; however, its role in epilepsy-related cognitive deficits is yet to be determined. In this study, we evaluated the effects of asiatic acid on cognitive deficits in rats with kainic acid (KA)-induced seizure and explored the potential mechanisms underlying these effects. Our results revealed that asiatic acid administrated intraperitoneally 30 min prior to KA (15 mg/kg) injection ameliorated seizures and significantly improved KA-induced memory deficits, as demonstrated by the results of the Morris water maze test. In addition, asiatic acid ameliorated neuronal damage, inhibited calpain activation, and increased protein kinase B (AKT) activation in the hippocampus of KA-treated rats. Asiatic acid also increased the levels of synaptic proteins and the number of synaptic vesicles as well as attenuated mitochondrial morphology damage in the hippocampus of KA-treated rats. Furthermore, proteomic and Western blot analyses of hippocampal synaptosomes revealed that asiatic acid reversed KA-induced changes in mitochondria function-associated proteins, including lipoamide dehydrogenase, glutamate dehydrogenase 1 (GLUD1), ATP synthase (ATP5A), and mitochondrial deacetylase sirtuin-3 (SIRT3). Our data suggest that asiatic acid can prevent seizures and improve cognitive impairment in KA-treated rats by reducing hippocampal neuronal damage through the inhibition of calpain activation and the elevation of activated AKT, coupled with an increase in synaptic and mitochondrial function.

Cognitive Effects of Astaxanthin Pretreatment on Recovery From Traumatic Brain Injury

Traumatic brain injury (TBI), caused by mechanical impact to the brain, is a leading cause of death and disability among young adults, with slow and often incomplete recovery. Preemptive treatment strategies may increase the injury resilience of high-risk populations such as soldiers and athletes. In this work, the xanthophyll carotenoid Astaxanthin was examined as a potential nutritional preconditioning method in mice (sabra strain) to increase their resilience prior to TBI in a closed head injury (CHI) model. The effect of Astaxanthin pretreatment on heat shock protein (HSP) dynamics and functional outcome after CHI was explored by gavage or free eating (in pellet form) for 2 weeks before CHI. Assessment of neuromotor function by the neurological severity score (NSS) revealed significant improvement in the Astaxanthin gavage-treated group (100 mg/kg, ATX) during recovery compared to the gavage-treated olive oil group (OIL), beginning at 24 h post-CHI and lasting throughout 28 days (p < 0.007). Astaxanthin pretreatment in pellet form produced a smaller improvement in NSS vs. posttreatment at 7 days post-CHI (p < 0.05). Cognitive and behavioral evaluation using the novel object recognition test (ORT) and the Y Maze test revealed an advantage for Astaxanthin administration via free eating vs. standard chow during recovery post-CHI (ORT at 3 days, p < 0.035; improvement in Y Maze score from 2 to 29 days, p < 0.02). HSP profile and anxiety (open field test) were not significantly affected by Astaxanthin. In conclusion, astaxanthin pretreatment may contribute to improved recovery post-TBI in mice and is influenced by the form of administration.

[1-(4-chloro-3-nitrobenzenesulfonyl)-1H-indol-3-yl]-methanol, an indole-3-carbinol derivative, inhibits glutamate release in rat cerebrocortical nerve terminals by suppressing the P/Q-type Ca2+ channels and Ca2+/calmodulin/protein kinase A pathway

Indole-3-carbinol (I3C), found in cruciferous vegetables, has been proposed to exhibit neuroprotective effects. This study aimed to investigate the effect of the I3C derivative [1(4-chloro-3-nitrobenzenesulfonyl)-1H-indol-3-yl]-methanol (CIM), which has superior pharmacokinetic properties to I3C, on glutamate release in rat cerebrocortical nerve terminals (synaptosomes). We observed that CIM dose-dependently inhibited glutamate release evoked by the potassium channel blocker 4-aminopyridine (4-AP). CIM-mediated inhibition of glutamate release was attributed to reduced exocytosis, as it correlated with the removal of extracellular calcium and blocking of the vesicular glutamate transporter but not the glutamate transporter. In addition, CIM decreased 4-AP-evoked intrasynaptosomal Ca²⁺ elevation; however, it did not alter the synaptosomal membrane potential. The inhibition of P/Q-typeCa²⁺ channels abolished the effect of CIM on 4-AP-evoked glutamate release, and the effect was not prevented by intracellular Ca²⁺ release inhibitors. Moreover, the molecular docking study showed that CIM exhibited the highest binding affinity with the P/Q-type Ca²⁺channels. Finally, the CIM-mediated inhibition of glutamate release was sensitive to calmodulin, adenylate cyclase (AC), and protein kinase A (PKA) inhibitors. Based on these results, we propose that CIM, through the direct suppression of P/Q-type Ca²⁺ channels, decreases Ca²⁺ influx and the activation of Ca²⁺/calmodulin/AC/PKA signaling, thereby inhibiting glutamate release. This finding is crucial for understanding the role of CIM in the central nervous system and for exploiting its potential in therapeutic interventions.