Kainic acid-induced neurodegenerative model: potentials and limitations

How is Excitotoxicity Being Modelled in iPSC-Derived Neurons?

Excitotoxicity linked either to environmental causes (pesticide and cyanotoxin exposure), excitatory neurotransmitter imbalance, or to intrinsic neuronal hyperexcitability, is a pathological mechanism central to neurodegeneration in amyotrophic lateral sclerosis (ALS). Investigation of excitotoxic mechanisms using in vitro and in vivo animal models has been central to understanding ALS mechanisms of disease. In particular, advances in induced pluripotent stem cell (iPSC) technologies now provide human cell-based models that are readily amenable to environmental and network-based excitotoxic manipulations. The cell-type specific differentiation of iPSC, combined with approaches to modelling excitotoxicity that include editing of disease-associated gene variants, chemogenetics, and environmental risk-associated exposures make iPSC primed to examine gene-environment interactions and disease-associated excitotoxic mechanisms. Critical to this is knowledge of which neurotransmitter receptor subunits are expressed by iPSC-derived neuronal cultures being studied, how their activity responds to antagonists and agonists of these receptors, and how to interpret data derived from multi-parameter electrophysiological recordings. This review explores how iPSC-based studies have contributed to our understanding of ALS-linked excitotoxicity and highlights novel approaches to inducing excitotoxicity in iPSC-derived neurons to further our understanding of its pathological pathways.

PDCD4 silencing alleviates KA‑induced neurotoxicity of HT22 cells by inhibiting endoplasmic reticulum stress via blocking the MAPK/NF‑κB signaling pathway

Human programmed cell death 4 (PDCD4) has been reported to participate in multiple neurological diseases. However, the role of PDCD4 in epilepsy, as well as its underlying mechanism, remains unclear. To induce excitotoxicity, 100 µM kainic acid (KA) was applied for the stimulation of HT22 cells for 12 h. Initially, the mRNA and protein expression levels of PDCD4 were evaluated using reverse transcription-quantitative PCR and western blotting. A lactate dehydrogenase assay was performed to detect cell injury. Cell apoptosis was assessed using flow cytometry and western blotting was performed to determine the expression levels of apoptosis-related proteins. Oxidative stress was detected using dichlorodihydrofluorescein diacetate staining, and malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) assay kits. Furthermore, the expression levels of MAPK/NF-κB signaling-related proteins and endoplasmic reticulum (ER) stress-related proteins C/EBP homologous protein, glucose-regulated protein 78, activating transcription factor 4 and phosphorylated-eukaryotic initiation factor-2α were assessed by western blotting. It was revealed that PDCD4 expression was markedly elevated in KA-induced HT22 cells, whereas PDCD4 silencing alleviated KA-induced neurotoxicity of HT22 cells by alleviating cell injury and inhibiting apoptosis. In addition, PDCD4 silencing reduced the levels of reactive oxygen species and MDA, but elevated those of SOD and GSH-Px. PDCD4 silencing also suppressed ER stress by blocking the MAPK/NF-κB signaling pathway. By contrast, the MAPK agonist phorbol myristate acetate reversed the effects of PDCD4 silencing on KA-induced neurotoxicity and oxidative stress in HT22 cells. In conclusion, PDCD4 silencing alleviated KA-induced neurotoxicity and oxidative stress in HT22 cells by suppressing ER stress through the inhibition of the MAPK/NF-κB signaling pathway, which may provide novel insights into the treatment of epilepsy.

The effects of Src tyrosine kinase inhibitor, saracatinib, on the markers of epileptogenesis in a mixed-sex cohort of adult rats in the kainic acid model of epilepsy

Neurodegeneration and neuroinflammation are key processes of epileptogenesis in temporal lobe epilepsy (TLE). A considerable number (∼30%) of patients with epilepsy are resistant to currently available antiseizure drugs and thus there is a need to develop adjunct therapies to modify disease progression. A vast majority of interventional strategies to treat TLE have utilized males which limits the translational nature of the studies. In this study, we investigated the effects of repeated low-dose kainic acid (KA) injection on the initial status epilepticus (SE) and the effects of Src kinase inhibitor, saracatinib (SAR/AZD0530; 20 mg/kg, oral, daily for 7 days), in a mixed-sex cohort of adult Sprague Dawley rats during early epileptogenesis. There were no sex differences in response to KA-induced SE, and neither did the stage of estrus influence SE severity. KA-induced SE caused significant astrogliosis and microgliosis across the hippocampus, piriform cortex, and amygdala. SAR treatment resulted in a significant reduction of microgliosis across brain regions. Microglial morphometrics such as branch length and the endpoints strongly correlated with CD68 expression in the vehicle-treated group but not in the SAR-treated group, indicating mitigation by SAR. KA-induced SE caused significant neuronal loss, including parvalbumin-positive inhibitory neurons, in both vehicle (VEH) and SAR-treated groups. SAR treatment significantly mitigated FJB-positive neuronal counts as compared to the VEH group. There was an increase in C3-positive reactive astrocytes in the VEH-treated group, and SAR treatment significantly reduced the increase in the piriform cortex. C3-positive astrogliosis significantly correlated with CD68 expression in the amygdala (AMY) of VEH-treated rats, and SAR treatment mitigated this relationship. There was a significant increase of pSrc(Y419)-positive microglia in both KA-treated groups with a statistically insignificant reduction by SAR. KA-induced SE caused the development of classical glial scars in the piriform cortex (PIR) in both KA-treated groups, while SAR treatment led to a 42.17% reduction in the size of glial scars. We did not observe sex differences in any of the parameters in this study. SAR, at the dose tested in the rat kainate model for a week in this study mitigated some of the markers of epileptogenesis in both sexes.

Prolactin reduces the kainic acid-induced increase in intracellular Ca2+ concentration, leading to neuroprotection of hippocampal neurons

The aim of this study was to determine the effect of prolactin (PRL) on intracellular calcium (Ca2+) concentration and its neuroprotective role in a model of kainic acid (KA) excitotoxicity in primary cultures of hippocampal neurons. Cell viability and intracellular Ca2+ concentrations were determined by MTT and Fura-2 assays, respectively, either after induction by KA as an agonist or after treatment with NBQX antagonist alone or in combination with PRL administration. Expression of ionotropic glutamatergic receptors (iGluRs) subunits in neuronal cells was determined by RT-qPCR. Dose-response treatments with KA or glutamate (Glu), the latter used as endogenous agonist control, induced a significant increase in neuronal intracellular Ca2+ concentration followed by a significant decrease in hippocampal neuronal viability. Administration of PRL induced a significant increase in neuronal viability after treatment with KA. Furthermore, administration of PRL decreased intracellular Ca2+ concentrations induced by KA treatment. Independent administration of the AMPAR-KAR antagonist reversed cell death and reduced intracellular Ca2+ concentration in a similar manner as PRL. Additionally, mRNA expression of AMPAR, KAR and NMDAR subtypes were detected in hippocampal neurons; however, no significant changes in iGluRs subunit expression were observed due to excitotoxicity or PRL treatment. The results suggest that PRL inhibits the increase in intracellular Ca2+ concentration induced by KA, leading to neuroprotection.

A detection method for neuronal death indicates abnormalities in intracellular membranous components in neuronal cells that underwent delayed death

Acute neuronal degeneration is always preceded under the light and electron microscopes by a stage called microvacuolation, which is characterized by a finely vacuolar alteration in the cytoplasm of the neurons destined to death. In this study, we reported a method for detecting neuronal death using two membrane-bound dyes, rhodamine R6 and DiOC₆(3), which may be associated with the so-called microvacuolation. This new method produced a spatiotemporally similar staining pattern to Fluoro-Jade B in kainic acid-damaged brains in mice. Further experiments showed that increased staining of rhodamine R6 and DiOC₆(3) was observed only in degenerated neurons, but not in glia, erythrocytes, or meninges. Different from Fluoro-Jade-related dyes, rhodamine R6 and DiOC₆(3) staining is highly sensitive to solvent extraction and detergent exposure. Staining with Nile red for phospholipids and filipin III for non-esterified cholesterol supports that the increased staining of rhodamine R6 and DiOC₆(3) might be associated with increased levels of phospholipids and free cholesterol in the perinuclear cytoplasm of damaged neurons. In addition to kainic acid-injected neuronal death, rhodamine R6 and DiOC₆(3) were similarly useful for detecting neuronal death in ischemic models either in vivo or in vitro. As far as we know, the staining with rhodamine R6 or DiOC₆(3) is one of a few histochemical methods for detecting neuronal death whose target molecules have been well defined and therefore may be useful for explaining experimental results as well as exploring the mechanisms of neuronal death. (250 words).

Pulsed Focused Ultrasound Reduces Hippocampal Volume Loss and Improves Behavioral Performance in the Kainic Acid Rat Model of Epilepsy

Focused ultrasound (FUS) has the potential to modulate regional brain excitability and possibly aid seizure control; however, effects on behavior of FUS used as a seizure therapy are unknown. This study explores behavioral effects and hippocampal restoration induced by pulsed FUS in a kainic acid (KA) animal model of temporal lobe epilepsy. Twenty-nine male Sprague-Dawley rats were observed for 20 weeks with anatomical magnetic resonance imaging (MRI) and behavioral performance evaluations, comprising measures of anxiety, limb usage, sociability, and memory. FUS targeted to the right hippocampus was given 9 and 14 weeks after KA was delivered to the right amygdala. Ultrasound pulsations were delivered with the acoustic settings of 0.25 of mechanical index, 0.5 W/cm2 of intensity spatial peak temporal average (ISPTA), 100 Hz of pulse repetition frequency, and 30% of duty cycle, during three consecutive pulse trains of 10 min separated by 5-min rests. Controls included normal animals with sham injections and KA-exposed animals without FUS exposure. Longitudinal MRI observations showed that FUS substantially protected hippocampal and striatal structures from KA-induced atrophy. KA alone increased anxiety, impaired contralateral limb usage, and reduced sociability and learning. Two courses of FUS sonications partially ameliorated these impairments by enhancing exploring and learning, balancing limb usage, and increasing social interaction. The histology results indicated that two sonications enhanced neuroprotection effect and decreased the inflammation markers induced by KA. This study supports existence of both neuroprotective and beneficial behavioral effects from low-intensity pulsed ultrasound in the KA animal model of epilepsy.

Plant based food bioactives: A boon or bane for neurological disorders

Neurological disorders are the foremost occurring diseases across the globe resulting in progressive dysfunction, loss of neuronal structure ultimately cell death. Therefore, attention has been drawn toward the natural resources for the search of neuroprotective agents. Plant-based food bioactives have emerged as potential neuroprotective agents for the treatment of neurodegenerative disorders. This comprehensive review primarily focuses on various plant food bioactive, mechanisms, therapeutic targets, in vitro and in vivo studies in the treatment of neurological disorders to explore whether they are boon or bane for neurological disorders. In addition, the clinical perspective of plant food bioactives in neurological disorders are also highlighted. Scientific evidences point toward the enormous therapeutic efficacy of plant food bioactives in the prevention or treatment of neurological disorders. Nevertheless, identification of food bioactive components accountable for the neuroprotective effects, mechanism, clinical trials, and consolidation of information flow are warranted. Plant food bioactives primarily act by mediating through various pathways including oxidative stress, neuroinflammation, apoptosis, excitotoxicity, specific proteins, mitochondrial dysfunction, and reversing neurodegeneration and can be used for the prevention and therapy of neurodegenerative disorders. In conclusion, the plant based food bioactives are boon for neurological disorders.

The Clock gene regulates kainic acid-induced seizures through inhibiting ferroptosis in mice

OBJECTIVES

Temporal lobe epilepsy (TLE) is a common and intractable form of epilepsy. There is a strong need to better understand molecular events underlying TLE and to find novel therapeutic agents. Here we aimed to investigate the role of Clock and ferroptosis in regulating TLE.

METHODS

TLE model was established by treating mice with kainic acid (KA). Regulatory effects of the Clock gene on KA-induced seizures and ferroptosis were evaluated using Clock knockout (Clock-/-) mice. mRNA and protein levels were determined by quantitative real-time PCR and western blotting, respectively. Ferroptosis was assessed by measuring the levels of iron, GSH and ROS. Transcriptional regulation was studied using a combination of luciferase reporter, mobility shift and chromatin immunoprecipitation (ChIP) assays.

KEY FINDINGS

We found that Clock ablation exacerbated KA-induced seizures in mice, accompanied by enhanced ferroptosis in the hippocampus. Clock ablation reduced the hippocampal expression of GPX4 and PPAR-γ, two ferroptosis-inhibitory factors, in mice and in N2a cells. Moreover, Clock regulates diurnal expression of GPX4 and PPAR-γ in mouse hippocampus and rhythmicity in KA-induced seizures. Consistent with this finding, Clock overexpression up-regulated GPX4 and PPAR-γ and protected against ferroptosis in N2a cells. In addition, luciferase reporter, mobility shift and ChIP assays showed that CLOCK trans-activated Gpx4 and Ppar-γ through direct binding to the E-box elements in the gene promoters.

CONCLUSION

CLOCK protects against KA-induced seizures through increased expression of GPX4 and PPAR-γ and inhibition of ferroptosis.

Blood Neurofilament Light Chain as a Potential Biomarker for Central and Peripheral Nervous Toxicity in Rats

Neurotoxicity is a principal concern in nonclinical drug development. However, standardized and universally accepted fluid biomarkers for evaluating neurotoxicity are lacking. Increasing clinical evidence supports the potential use of neurofilament light (NfL) chain as a biomarker of several neurodegenerative diseases; therefore, we investigated changes in the cerebrospinal fluid (CSF) and serum levels of NfL in Sprague Dawley rats treated with central nervous system (CNS) toxicants (trimethyltin [TMT, 10 mg/kg po, single dose], kainic acid [KA, 12 mg/kg sc, single dose], MK-801 [1 mg/kg sc, single dose]), and a peripheral nervous system (PNS) toxicant (pyridoxine, 1200 mg/kg/day for 3 days). Animals were euthanized 1 (day 2), 3 (day 4), or 7 days after administration (day 8). Increased serum NfL was observed in TMT- and KA-treated animals, which indicated neuronal cell death in the brain on days 2, 4, and/or 8. MK-801-treated animals exhibited no changes in the serum and CSF levels of NfL and no histopathological changes in the brain at any time point. Pyridoxine-induced chromatolysis of the dorsal root ganglion on day 2 and degeneration of peripheral nerve fiber on day 4; additionally, serum NfL was increased. A strong correlation was observed between the serum and CSF levels of NfL and brain lesions caused by TMT and KA, indicating that NfL could be a useful biomarker for detecting CNS toxicity. Additionally, PNS changes were correlated with serum NfL levels. Therefore, serum NfL could serve as a useful peripheral biomarker for detecting both CNS and PNS toxicity in rats.

Repeated exposure to microcystin-leucine-arginine potentiates excitotoxicity induced by a low dose of kainate

Microcystin-leucine-arginine (MLCR) is a cyanobacterial toxin, and has been demonstrated to cause neurotoxicity. In addition, MCLR has been identified as an inhibitor of protein phosphatase (PP)1 and PP2A, which are known to regulate the phosphorylation of various molecules related to synaptic excitability. Thus, in the present study, we examined whether MCLR exposure affects seizures induced by a low dose of kainic acid (KA; 0.05 μg, i.c.v.) administration. KA-induced seizure occurrence and seizure score significantly increased after repeated exposure to MCLR (2.5 or 5.0 μg/kg, i.p., once a day for 10 days), but not after acute MCLR exposure (2.5 or 5.0 μg/kg, i.p., 2 h and 30 min prior to KA administration), and hippocampal neuronal loss was consistently facilitated by repeated exposure to MCLR. In addition, repeated MCLR significantly elevated the membrane expression of kainate receptor GluK2 subunits, p-pan-protein kinase C (PKC), and p-extracellular signal-related kinase (ERK) at 1 h after KA. However, KA-induced membrane expression of Ca²⁺/calmodulin-dependent kinase II (CaMKII) was significantly reduced by repeated MCLR exposure. Consistent with the enhanced seizures and neurodegeneration, MCLR exposure significantly potentiated KA-induced oxidative stress and microglial activation, which was accompanied by increased expression of p-ERK and p-PKCδ in the hippocampus. The combined results suggest that repeated MCLR exposure potentiates KA-induced excitotoxicity in the hippocampus by increasing membrane GluK2 expression and enhancing oxidative stress and neuroinflammation through the modulation of p-CaMKII, p-PKC, and p-ERK.

Revealing NOTCH-dependencies in synaptic targets associated with Alzheimer's disease

Recent studies have identified NOTCH signaling as a contributor of neurodegeneration including Alzheimer's disease' (AD) pathophysiology. As part of the efforts to understand molecular mechanisms and players involved in neurodegenerative dementia, we employed transgenic mouse models with Notch1 and Rbpjk loss of function (LOF) mutation in pyramidal neurons of the CA fields. Using RNA-seq, we have investigated the differential expression of NOTCH-dependent genes either upon environmental enrichment (EE) or upon kainic acid (KA) injury. We found a substantial genetic diversity in absence of both NOTCH1 receptor or RBPJK transcriptional activator. Among differentially expressed genes, we observed a significant upregulation of Gabra2a in both knockout models, suggesting a role for NOTCH signaling in the modulation of E/I balance. Upon excitotoxic stimulation, loss of RBPJK results in decreased expression of synaptic proteins with neuroprotective effects. We confirmed Nptx2, Npy, Pdch8, TncC as direct NOTCH1/RBPJK targets and Bdnf and Scg2 as indirect targets. Finally, we translate these findings into human entorhinal cortex containing the hippocampal region from AD patients performing targeted transcripts analysis. We observe an increased trend for RBPJK and the ligand DNER starting in the mild-moderate stage of the disease with no change of NOTCH1 expression. Alongside, expression of the Notch targets Hes5 and Hey1 tend to rise in the intermediate stage of the disease and drop in severe AD. Similarly the newly discovered NOTCH targets, NPTX2, NPY, BDNF show an up-warding tendency during the mild-moderate stage, and decline in the severe phase of the disease. This study identifies NOTCH as a central signaling cascade capable of modulating synaptic transmission in response to excitatory insult through the activation of neuroprotective genes that have been associated to AD.

Kainate-Induced Degeneration of Hippocampal Neurons. Protective Effect of Activation of the Endocannabinoid System

We studied the prolonged action of kainic acid on glutamatergic neurons in the dorsal hippocampus and the endocannabinoid-dependent protection against neurodegeneration. The pyramidal neurons of the CA3 field of the hippocampus, as well as granular and mossy cells of the dentate gyrus were examined. Light and electron microscopy revealed substantial damage to the components of the protein-synthesizing (rough endoplasmic reticulum, Golgi apparatus, and polyribosomes) and catabolic (lysosomes, autophagosomes, multivesicular structures, and lipofuscin formations) systems in all cells. Pyramidal and mossy neurons die mainly by the necrotic pathway. The death of granular cells occurred through both apoptosis and necrosis. The most vulnerable cells are mossy neurons located in the hilus. Activation of the endocannabinoid system induced by intracerebral injection of URB597, an inhibitor of degradation of endocannabinoid anandamide, protected the normal structure of the hippocampus and prevented neuronal damage and death induced by KA.

Activation modes in biocatalytic radical cyclization reactions

Radical cyclizations are essential reactions in the biosynthesis of secondary metabolites and the chemical synthesis of societally valuable molecules. In this review, we highlight the general mechanisms utilized in biocatalytic radical cyclizations. We specifically highlight cytochrome P450 monooxygenases (P450s) involved in the biosynthesis of mycocyclosin and vancomycin, nonheme iron- and α-ketoglutarate-dependent dioxygenases (Fe/αKGDs) used in the biosynthesis of kainic acid, scopolamine, and isopenicillin N, and radical S-adenosylmethionine (SAM) enzymes that facilitate the biosynthesis of oxetanocin A, menaquinone, and F420. Beyond natural mechanisms, we also examine repurposed flavin-dependent "ene"-reductases (ERED) for non-natural radical cyclization. Overall, these general mechanisms underscore the opportunity for enzymes to augment and enhance the synthesis of complex molecules using radical mechanisms.

Analysis of KATP Channels Opening Probability of Hippocampus Cells Treated with Kainic Acid

Background

Kainic acid (KA)-induced seizures may be a valuable tool in the assessment of anti-epileptic drug efficacy in complex partial seizures. This study investigated the effects of KA on ATP-sensitive K⁺ (K_ATP) channels opening probability (NPo), which plays a crucial role in neuronal activities.

Methods

For the optimisation and validation protocol, β-cells were plated onto 35 mm plastic petri dishes and maintained in RPMI-1640 media supplemented with 10 mM glucose, 10% FCS and 25 mM of N-2-hydroxyethylpiperazine-N-ethanesulfonic acid (HEPES). The treatment effects of 10 mM glucose and 30 μM fluoxetine on K_ATP channels NPo of β-cells were assessed via cell-attached patch-clamp recordings. For hippocampus cell experiments, hippocampi were harvested from day 17 of maternal Lister-hooded rat foetus, and then transferred to a Ca²⁺ and Mg²⁺-free HEPES-buffered Hank's salt solution (HHSS). The dissociated cells were cultured and plated onto a 25 mm round cover glasses coated with poly-d-lysine (0.1 mg/mL) in a petri dish. The K_ATP channels NPo of hippocampus cells when perfused with 1 mM and 10 mM of KA were determined.

Results

NPo of β-cells showed significant decreasing patterns (P < 0.001) when treated with 10 mM glucose 0.048 (0.027) as well as 30 μM fluoxetine 0.190 (0.141) as compared to basal counterpart. In hippocampus cell experiment, a significant increase (P < 0.001) in mean NPo 2.148 (0.175) of neurons when applied with 1 mM of KA as compared to basal was observed.

Conclusion

The two concentrations of KA used in the study exerted contrasting effects toward the mean of NPo. It is hypothesised that KA at lower concentration (1 mM) opens more K_ATP channels, leading to hyperpolarisation of the neurons, which may prevent neuronal hyper excitability. No effect was shown in 10 mM KA treatment, suggesting that only lower than 10 mM KA produced significant changes in K_ATP channels. This implies further validation of KA concentration to be used in the future.

Ictal activation of oxygen-conserving reflexes as a mechanism for sudden death in epilepsy

OBJECTIVE

To test the hypothesis that death with physiological parallels to human cases of sudden unexpected death in epilepsy (SUDEP) can be induced in seizing rats by ictal activation of oxygen-conserving reflexes (OCRs).

METHODS

Urethane-anesthetized female Long-Evans rats were implanted with electrodes for electrocardiography (ECG), electrocorticography (ECoG), and respiratory thermocouple; venous and arterial cannulas; and a laryngoscope guide and cannula or nasal cannula for activation of the laryngeal chemoreflex (LCR) or mammalian diving reflex (MDR), respectively. Kainic acid injection, either systemic or into the ventral hippocampus, induced prolonged acute seizures.

RESULTS

Reflex challenges during seizures caused sudden death in 18 of 20 rats-all MDR rats (10) and all but two LCR rats (8) failed to recover from ictal activation of OCRs and died within minutes of the reflexes. By comparison, 4 of 4 control (ie, nonseizing) rats recovered from 64 induced diving reflexes (16 per rat), and 4 of 4 controls recovered from 64 induced chemoreflexes (16 per rat). Multiple measures were consistent with reports of human SUDEP. Terminal central apnea preceded terminal asystole in all cases. Heart and respiratory rate fluctuations that paralleled those seen in human SUDEP occurred during OCR-induced sudden death, and mean arterial pressure (MAP) was predictive of death, showing a 17 or 15 mm Hg drop (MDR and LCR, respectively) in the 20 s window centered on the time of brain death. OCR activation was never fatal in nonseizing rats.

SIGNIFICANCE

These results present a method of inducing sudden death in two seizure models that show pathophysiology consistent with that observed in human cases of SUDEP. This proposed mechanism directly informs previous findings by our group and others in the field; provides a repeatable, inducible animal model for the study of sudden death; and offers a potential explanation for observations made in cases of human SUDEP.

Hippocampal Degeneration and Behavioral Impairment During Alzheimer-Like Pathogenesis Involves Glutamate Excitotoxicity

The hallmarks of Alzheimer's disease (AD) pathology include senile plaques accumulation and neurofibrillary tangles, which is thought to underlie synaptic failure. Recent evidence however supports that synaptic failure in AD may instead be instigated by enhanced N-methyl-D-aspartate (NMDA) activity, via a reciprocal relationship between soluble amyloid-β (Aβ) accumulation and increased glutamate agonist. While previous studies have shown Aβ-mediated alterations to the glutamatergic system during AD, the underlying etiology of excitotoxic glutamate-induced changes has not been explored. Here, we investigated the acute effects of stereotaxic dentate gyrus (DG) glutamate injection on behavior and molecular expression of specific proteins and neurochemicals modulating hippocampal functions. Dependence of glutamate-mediated effects on NMDA receptor (NMDAR) hyperactivation was tested using NMDARs antagonist memantine. DG of Wistar rats (12-weeks-old) were bilaterally microinjected with glutamate (500 mM) with or without daily intraperitoneal (i.p.) memantine injection (20 mg/kg) for 14 days, while controls received either intrahippocampal/i.p. PBS or i.p. memantine. Behavioral characterization in open field and Y-maze revealed that glutamate evoked anxiogenic responses and perturbed spatial memory were inhibited by memantine. In glutamate-treated rats, increased NO expression was accompanied by marked reduction in profiles of glutathione-s-transferase and glutathione peroxidase. Similarly, glutamate-mediated increase in acetylcholinesterase expression corroborated downregulation of synaptophysin and PSD-95, coupled with initiation of reactive astrogliosis (GFAP). While neurofilament immunolocalization/immunoexpression was unperturbed, we found glutamate-mediated reduction in neurogenic markers Ki67 and PCNA immunoexpression, with a decrease in NR2B protein expression, whereas mGluR1 remains unchanged. In addition, increased expression of apoptotic regulatory proteins p53 and Bax was seen in glutamate infused rats, corroborating chromatolytic degeneration of granule neurons in the DG. Interestingly, memantine abrogated most of the degenerative changes associated with glutamate excitotoxicity in this study. Taken together, our findings causally link acute glutamate dyshomeostasis in the DG with development of AD-related behavioral impairment and molecular neurodegeneration.

Prolactin neuroprotective action against excitotoxic insult in the hippocampus of male mice

Prolactin (PRL) is known to exert neuroprotective effects against excitotoxic damage in the hippocampus of female rats, both in vitro and in vivo. It is still unknown whether this effect can be seen in the male hippocampus and intracellular signaling mediating such action. To assess this, adult male CD-1 mice were subjected to excitotoxic damage with kainic acid (KA; i.c.v.), after a) no manipulation (control group), b) treatment with saline, and c) treatment with PRL (8 μg of PRL/100 μl of saline s.c.). Treatments consisted of one daily injection of the mentioned dosage for seven consecutive days until the day of the excitotoxic lesion. Neurodegeneration (Fluoro-Jade C), neuronal survival (NeuN) and astrogliosis (GFAP) markers were identified with immunohistochemistry in the CA1, CA3 and CA4 areas of the dorsal hippocampus, as well as PRL-related protein levels by Western blot in the whole hippocampus 48 h after excitotoxicity. Anatomical measurements revealed a preferential protective effect of PRL against excitotoxic damage in the CA3 hippocampal subfield, with lower levels of cell death and neurodegeneration, compared to controls. In CA4, the results were not conclusive, and no damage was observed in CA1 after KA administration. PRL treatment provoked an upregulation of active Akt, a well-known cell survival pathway, after KA administration. PRL also caused downregulation of active MAPK, independently of the excitotoxic damage. The present results indicate a neuroprotective role for PRL preferentially located in the CA3 area of the hippocampus of male mice, possibly mediated by Akt-related survival mechanisms.

Combined Cell Therapy in the Treatment of Neurological Disorders

Cell therapy of neurological diseases is gaining momentum. Various types of stem/progenitor cells and their derivatives have shown positive therapeutic results in animal models of neurological disorders and in clinical trials. Each tested cell type proved to have its advantages and flaws and unique cellular and molecular mechanism of action, prompting the idea to test combined transplantation of two or more types of cells (combined cell therapy). This review summarizes the results of combined cell therapy of neurological pathologies reported up to this point. The number of papers describing experimental studies or clinical trials addressing this subject is still limited. However, its successful application to the treatment of neurological pathologies including stroke, spinal cord injury, neurodegenerative diseases, Duchenne muscular dystrophy, and retinal degeneration has been reported in both experimental and clinical studies. The advantages of combined cell therapy can be realized by simple summation of beneficial effects of different cells. Alternatively, one kind of cells can support the survival and functioning of the other by enhancing the formation of optimum environment or immunomodulation. No significant adverse events were reported. Combined cell therapy is a promising approach for the treatment of neurological disorders, but further research needs to be conducted.

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.

TGF-β3/Smad3 Contributes to Isoflurane Postconditioning Against Cerebral Ischemia-Reperfusion Injury by Upregulating MEF2C

Isoflurane postconditioning alleviates cerebral ischemic-reperfusion injury (CIRI), but the underlying mechanism has not been fully clarified. We previously demonstrated that the transforming growth factor beta-1 (TGF-β1)/Smads signaling pathway is involved in the neuroprotective effect of isoflurane postconditioning. TGF-β3 has a highly homologous sequence relative to that of TGF-β1. In this study, we explored the roles of the TGF-β3/Smad3 signaling pathway and myocyte enhancer factor 2C (MEF2C) in neuroprotection induced by isoflurane postconditioning. A CIRI rat model was established by middle cerebral artery occlusion for 1.5 h, followed by 24 h of reperfusion. Isoflurane postconditioning led to lower infarct volumes and neurologic deficit scores, more surviving neurons, and less damaged and apoptotic neurons as compared with those of CIRI rats. Moreover, isoflurane postconditioning upregulated the expressions of TGF-β3, p-Smad3, and MEF2C. However, the neuroprotective effect was reversed by pirfenidone, a TGF-β3/Smad3 signaling pathway inhibitor. Also, pirfenidone treatment downregulated the expression of MEF2C. These results indicate that the TGF-β3/Smad3 signaling pathway contributes to the neuroprotection of isoflurane postconditioning after CIRI and is possibly related to MEF2C.

Dietary omega-3 fatty acids prevent neonatal seizure-induced early alterations in the hippocampal glutamatergic system and memory deficits in adulthood

OBJECTIVE

We investigated the influence of dietary omega-3 polyunsaturated fatty acids (n-3 PUFAs) on glutamatergic system modulation after a single episode of neonatal seizures and their possible effects on seizure-induced long-lasting behavioral deficits.

METHODS

Male Wistar rats receiving an omega-3 diet (n-3) or an n-3 deficient diet (D) from the prenatal period were subjected to a kainate-induced seizure model at P7. Glutamate transporter activity and immunocontents (GLT-1 and GLAST) were assessed in the hippocampus at 12, 24, and 48 h after the seizure episode. Fluorescence intensity for glial cells (GFAP) and neurons (NeuN) was assessed 24 h after seizure in the hippocampus. Behavioral analysis (elevated-plus maze and inhibitory avoidance memory task) was performed at 60 days of age.

RESULTS

The D group showed a decrease in glutamate uptake 24 h after seizure. In this group only, the GLT1 content increased at 12 h, followed by a decrease at 24 h. GLAST increased up to 24 h after seizure. GFAP fluorescence was higher, and NeuN fluorescence decreased, in the D group independent of seizures. In adulthood, the D group presented memory deficits independent of seizures, but short-term memory (1.5 h after a training session) was abolished in the D group treated with kainate.

SIGNIFICANCE

N-3 PUFA positively influenced the glutamatergic system during seizure and prevented seizure-related memory deficits in adulthood.

The stress-responsive gene GDPGP1/mcp-1 regulates neuronal glycogen metabolism and survival

Maladaptive responses to stress might play a role in the sensitivity of neurons to stress. To identify novel cellular responses to stress, we performed transcriptional analysis in acutely stressed mouse neurons, followed by functional characterization in Caenorhabditis elegans. In both contexts, we found that the gene GDPGP1/mcp-1 is down-regulated by a variety of stresses. Functionally, the enzyme GDPGP1/mcp-1 protects against stress. Knockdown of GDPGP1 in mouse neurons leads to widespread neuronal cell death. Loss of mcp-1, the single homologue of GDPGP1 in C. elegans, leads to increased degeneration of GABA neurons as well as reduced survival of animals following environmental stress. Overexpression of mcp-1 in neurons enhances survival under hypoxia and protects against neurodegeneration in a tauopathy model. GDPGP1/mcp-1 regulates neuronal glycogen levels, indicating a key role for this metabolite in neuronal stress resistance. Together, our data indicate that down-regulation of GDPGP1/mcp-1 and consequent loss of neuronal glycogen is a maladaptive response that limits neuronal stress resistance and reduces survival.

Harnessing the biocatalytic potential of iron- and α-ketoglutarate-dependent dioxygenases in natural product total synthesis

Covering: up to the end of 2019Iron- and α-ketoglutarate-dependent dioxygenases (Fe/αKGs) represent a versatile and intriguing enzyme family by virtue of their ability to directly functionalize unactivated C-H bonds at the cost of αKG and O2. Fe/αKGs play an important role in the biosynthesis of natural products, valuable biologically active secondary metabolites frequently pursued as drug leads. The field of natural product total synthesis seeks to contruct these molecules as effeciently as possible, although natural products continue to challenge chemists due to their intricate structural complexity. Chemoenzymatic approaches seek to remedy the shortcomings of traditional synthetic methodology by combining Nature's biosynthetic machinery with traditional chemical methods to efficiently construct natural products. Although other oxygenase families have been widely employed for this purpose, Fe/αKGs remain underutilized. The following review will cover recent chemoenzymatic total syntheses involving Fe/αKG enzymes. Additionally, related information involving natural product biosynthesis, methods development, and non-chemoenzymatic total syntheses will be discussed to inform retrosynthetic logic and synthetic design.

Map kinase signaling as therapeutic target for neurodegeneration

Aging is known to be one of the major risk factors in many neurodegenerative diseases (ND) whose prevalence is estimated to rise in the coming years due to the increase in life expectancy. Examples of neurodegenerative diseases include Huntington's, Parkinson's, and Alzheimer's diseases, along with Amyotrophic Lateral Sclerosis, Spinocerebellar ataxias and Frontotemporal Dementia. Given that so far these ND do not have effective pharmacological therapies, a better understanding of the molecular and cellular mechanisms can contribute to development of effective treatments. During the previous decade, the data indicated that dysregulation of MAP kinases [which included c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1 and 2 (ERK1/2), and p38] are associated with several stages of the inflammatory process which in turn contributes to age-related neurodegenerative diseases. This evidence suggests that control of inflammation through regulation of MAP kinase could be a worthwhile approach against neurodegenerative diseases. In this review we summarize the pathways of MAP kinase signal transduction and different pharmacological inhibitors that can be used in its modulation against ND.

Kainic acid Induces production and aggregation of amyloid β-protein and memory deficits by activating inflammasomes in NLRP3- and NF-κB-stimulated pathways

Kainic acid (KA) treatment causes neuronal degeneration, which is a feature of Alzheimer’s disease (AD) symptoms such as amyloid β-protein production and memory deficits. Inflammasomes are known to be critical for the progression of AD. However, the underlying mechanism by which inflammasomes influence AD progression remains unknown. The present study investigated the damaging effect of KA on neurons by focusing on the inflammasome-mediated signaling pathways. Assessments using cultured microglia and mouse brains demonstrated that KA treatment specifically induced inflammasome activation. Mechanistic evaluations showed that KA activated two major components of inflammasomes, nucleotide binding oligomerization domain (NOD)-like receptor (NLR) protein 3 (NLRP3) and nuclear factor (NF)-κB, which resulted in the production of interleukin-1β (IL-1β) and brain-derived neurotrophic factor (BDNF). Inhibition of NLRP3 or NF-κB by Bay11-7082 caused a reduction in the KA-induced expression of interleukin (IL)-1β and BDNF. Moreover, knockdown of the expression of KA receptors (KARs) such as Grik1 and Grik3 induced suppression of NLRP3 and NF-κB, suggesting that KARs function upstream of NLRP3 and NF-κB to mediate the effects of KA on regulation of IL-1β and BDNF expression. Notably, IL-1β was shown to exert positive effects on the expression of BACE1, which is blocked by Bay11-7082. Overall, our results revealed that Bay11-7082 acts against KA-induced neuronal degeneration, amyloid β-protein (Aβ) deposition, and memory defects via inflammasomes and further highlighted the protective role of Bay11-7082 in KA-induced neuronal defects.

Marine Excitatory Amino Acids: Structure, Properties, Biosynthesis and Recent Approaches to Their Syntheses

This review considers the results of recent studies on marine excitatory amino acids, including kainic acid, domoic acid, dysiherbaine, and neodysiherbaine A, known as potent agonists of one of subtypes of glutamate receptors, the so-called kainate receptors. Novel information, particularly concerning biosynthesis, environmental roles, biological action, and syntheses of these marine metabolites, obtained mainly in last 10–15 years, is summarized. The goal of the review was not only to discuss recently obtained data, but also to provide a brief introduction to the field of marine excitatory amino acid research.

Apolipoprotein D

ApoD is a 25 to 30 kDa glycosylated protein, member of the lipocalin superfamily. As a transporter of several small hydrophobic molecules, its known biological functions are mostly associated to lipid metabolism and neuroprotection. ApoD is a multi-ligand, multi-function protein that is involved lipid trafficking, food intake, inflammation, antioxidative response and development and in different types of cancers. An important aspect of ApoD's role in lipid metabolism appears to involve the transport of arachidonic acid, and the modulation of eicosanoid production and delivery in metabolic tissues. ApoD expression in metabolic tissues has been associated positively and negatively with insulin sensitivity and glucose homeostasis in a tissue dependent manner. ApoD levels rise considerably in association with aging and neuropathologies such as Alzheimer's disease, stroke, meningoencephalitis, moto-neuron disease, multiple sclerosis, schizophrenia and Parkinson's disease. ApoD is also modulated in several animal models of nervous system injury/pathology.

Revisiting the Impact of Neurodegenerative Proteins in Epilepsy: Focus on Alpha-Synuclein, Beta-Amyloid, and Tau

Lack of disease-modifying therapy against epileptogenesis reflects the complexity of the disease pathogenesis as well as the high demand to explore novel treatment strategies. In the pursuit of developing new therapeutic strategies against epileptogenesis, neurodegenerative proteins have recently gained increased attention. Owing to the fact that neurodegenerative disease and epileptogenesis possibly share a common underlying mechanism, targeting neurodegenerative proteins against epileptogenesis might represent a promising therapeutic approach. Herein, we review the association of neurodegenerative proteins, such as α-synuclein, amyloid-beta (Aβ), and tau protein, with epilepsy. Providing insight into the α-synuclein, Aβ and tau protein-mediated neurodegeneration mechanisms, and their implication in epileptogenesis will pave the way towards the development of new agents and treatment strategies.

Neuroprotection from Excitotoxic Injury by Local Administration of Lipid Emulsion into the Brain of Rats

Lipid emulsion was recently shown to attenuate cell death caused by excitotoxic conditions in the heart. There are key similarities between neurons and cardiomyocytes, such as excitability and conductibility, which yield vulnerability to excitotoxic conditions. However, systematic investigations on the protective effects of lipid emulsion in the central nervous system are still lacking. This study aimed to determine the neuroprotective effects of lipid emulsion in an in vivo rat model of kainic acid-induced excitotoxicity through intrahippocampal microinjections. Kainic acid and/or lipid emulsion-injected rats were subjected to the passive avoidance test and elevated plus maze for behavioral assessment. Rats were sacrificed at 24 h and 72 h after kainic acid injections for molecular study, including immunoblotting and qPCR. Brains were also cryosectioned for morphological analysis through cresyl violet staining and Fluorojade-C staining. Anxiety and memory functions were significantly preserved in 1% lipid emulsion-treated rats. Lipid emulsion was dose-dependent on the protein expression of β-catenin and the phosphorylation of GSK3-β and Akt. Wnt1 mRNA expression was elevated in lipid emulsion-treated rats compared to the vehicle. Neurodegeneration was significantly reduced mainly in the CA1 region with increased cell survival. Our results suggest that lipid emulsion has neuroprotective effects against excitotoxic conditions in the brain and may provide new insight into its potential therapeutic utility.

Edaravone inhibits procaspase-3 denitrosylation and activation through FasL-Trx2 pathway in KA-induced seizure

Previous studies have demonstrated that excessive free radicals play an essential role in the initiation and progression of epilepsy and that a novel exogenous free radical scavenger edaravone (Ed) exerts some neuroprotective effects on seizure-induced neuronal damage. The purpose of this study was to elucidate the possible molecular mechanisms of Ed associated with procaspase-3 denitrosylation and activation through the FasL-Trx2 pathway in seizures rats. In this study, we investigated the effects of Ed on the regulation of the combination of Fas ligand/Fas receptor and the major components of the death-inducing signaling complex (DISC) in the hippocampus of kainic acid (KA)-treated Sprague Dawley (SD) rats. Treatment with Ed can attenuate the increased expression of FasL induced by KA and prevent procaspase-3 denitrosylation and activation via suppression of the FasL-Trx2 signaling pathway, which alleviates the neuronal damage in seizures. These results provide experimental evidence that Ed functions by preventing the denitrosylation and activation of procaspase-3 and that Ed acts as a therapeutic option for epilepsy.

Natural Products and Their Bioactive Compounds: Neuroprotective Potentials against Neurodegenerative Diseases

In recent years, natural products, which originate from plants, animals, and fungi, together with their bioactive compounds have been intensively explored and studied for their therapeutic potentials for various diseases such as cardiovascular, diabetes, hypertension, reproductive, cancer, and neurodegenerative diseases. Neurodegenerative diseases, including Alzheimer's disease, Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis are characterized by the progressive dysfunction and loss of neuronal structure and function that resulted in the neuronal cell death. Since the multifactorial pathological mechanisms are associated with neurodegeneration, targeting multiple mechanisms of actions and neuroprotection approach, which involves preventing cell death and restoring the function to damaged neurons, could be promising strategies for the prevention and therapeutic of neurodegenerative diseases. Natural products have emerged as potential neuroprotective agents for the treatment of neurodegenerative diseases. This review focused on the therapeutic potential of natural products and their bioactive compounds to exert a neuroprotective effect on the pathologies of neurodegenerative diseases.

NADPH protects against kainic acid-induced excitotoxicity via autophagy-lysosome pathway in rat striatum and primary cortical neurons

PURPOSE

To investigate the effects and mechanisms of NADPH on Kainic acid (KA)-induced excitotoxicity.

METHODS

KA, a non-N-methyl-d-aspartate glutamate receptor agonist, was exposed to adult SD rats via intrastriatal injection and rat primary cortical neurons to establish excitotoxic models in vivo and in vitro, respectively. To determine the effects of NADPH on KA-induced excitotoxicity, neuronal survival, neurologically behavioral score and oxidative stress were evaluated. To explore the mechanisms of neuroprotective effects of NADPH, the autophagy-lysosome pathway related proteins were detected.

RESULTS

In vivo, NADPH (1 mg/kg or 2 mg/kg) diminished KA (2.5 nmol)-induced enlargement of lesion size in striatum, improved KA-induced dyskinesia and reversed KA-induced activation of glial cells. Nevertheless, the neuroprotective effect of NADPH was not significant under the condition of autophagy activation. NADPH (2 mg/kg) inhibited KA (2.5 nmol)-induced down-regulation of TP-53 induced glycolysis and apoptosis regulator (TIGAR) and p62, and up-regulation of the protein levels of LC3-II/LC3-I, Beclin-1 and Atg5. In vitro, the excitotoxic neuronal injury was induced after KA (50 μM, 100 μM or 200 μM) treatment as demonstrated by decreased cell viability. Moreover, KA (100 μM) increased the intracellular levels of calcium and reactive oxygen species (ROS) and declined the levels of the reduced form of glutathione (GSH). Pretreatment of NADPH (10 μM) effectively reversed these changes. Meanwhile NADPH (10 μM) inhibited KA (100 μM)-induced down-regulation of TIGAR and p62, and up-regulation of the ratio of LC3-II/LC3-I, Beclin-1, Atg5, active-cathepsin B and active-cathepsin D.

CONCLUSIONS

Our data provide a possible mechanism that NADPH ameliorates KA-induced excitotoxicity by blocking the autophagy-lysosome pathway and up-regulating TIGAR along with its antioxidant properties.

Kainic acid-induced status epilepticus decreases mGlu5 receptor and phase-specifically downregulates Homer1b/c expression

Globally, over 50 million people are affected by epilepsy, which is characterized by the occurrence of spontaneous recurrent seizures. Almost one-third of the patients show resistance to current anti-epileptic drugs, making the exploration of new molecular targets necessary. An interesting target may be Homer1, due to its diverse roles in epileptogenesis and synaptic plasticity. Indeed, Homer1 regulates group I metabotropic glutamate (mGlu) receptors (i.e. mGlu₁ and mGlu₅) scaffolding and signaling in neurons. In the present work, using the systemic kainic acid (KA)-induced status epilepticus (SE) model in adult rats, we investigated the mRNA and protein expression patterns of the mGlu₅ receptor, Homer1a and Homer1b/c at 10, 80 and 120 days post-SE (i.e. T10, T80 and T120). Epileptogenesis was validated by electrophysiological recordings of seizures via electroencephalography (EEG) monitoring and through upregulation of glial fibrillary acidic protein. At the protein level, the mGlu₅ receptor was downregulated in the late latent phase (T10) and the early- and late exponential growth phase (T80 and T120, respectively), which was best observed in the hippocampal CA1 region. At mRNA level, significant downregulation of the mGlu₅ receptor was only detected in the late exponential growth phase. Homer1a expression did not change at any investigated time point. Interestingly, Homer1b/c was only downregulated in the late latent phase, a period where spontaneous seizures are extremely rare. Thus, this phase-specific downregulation may be indicative of an endogenous neuroprotective mechanism. In conclusion, these results suggest that Homer1b/c may be an interesting molecular target to prevent epileptogenesis and/or control seizures.

Genetic backgrounds have unique seizure response profiles and behavioral outcomes following convulsant administration

Three highly utilized strains of mice, common for preclinical genetic studies, were evaluated for seizure susceptibility and behavioral outcomes common to the clinical phenotypes of numerous psychiatric disorders following repeated low-dose treatment with either a gamma-aminobutyric acid (GABA) receptor antagonist (pentylenetetrazole (PTZ)) or a glutamate agonist (kainic acid (KA)). Effects of strain and treatment were evaluated with classic seizure scoring and a tailored behavior battery focused on behavioral domains common in neuropsychiatric research: learning and memory, social behavior, and motor abilities, as well as seizure susceptibility and/or resistance. Seizure response was induced by a single daily treatment of either PTZ (30 mg/kg, intraperitoneally (i.p.)) or KA (5 mg/kg, i.p.) for 10 days. Pentylenetetrazole-treated FVB/NJ and C57BL/6NJ strains of mice showed strong, clear seizure responses. This also resulted in cognitive and social deficits, and increased susceptibility to a high dose of PTZ. Kainic acid-treated FVB/NJ and C57BL/6NJ strains of mice had a robust seizure response, which resulted in hyperactivity. Pentylenetetrazole-treated C57BL/6J mice demonstrated mild hyperactivity, while KA-treated C57BL/6J displayed cognitive deficits and resistance to a high dose of KA but no social deficits. Overall, a uniquely different seizure response profile was detected in the C57BL/6J strain with few observable instances of seizure response despite repeated convulsant administration by two mechanisms. This work illustrated that differing background genetic strains have unique seizure susceptibility profiles and distinct social and cognitive behavior following PTZ and/or KA treatment and that it is, therefore, necessary to consider strain differences before attributing behavioral phenotypes to gene(s) of interest during preclinical evaluations of genetic mouse models, especially when outcome measures are focused on cognitive and/or social behaviors common to the clinical features of numerous neurological disorders.

Kainic Acid-Based Agonists of Glutamate Receptors: SAR Analysis and Guidelines for Analog Design

A comprehensive survey of kainic acid analogs that have been tested for their biological activity is presented. Specifically, this review (1) gathers and compares over 100 kainoids according to a relative activity scale, (2) exposes structural features required to optimize affinity for kainate receptors, and (3) suggests design rules to create next-generation KA analogs. Literature SAR data are analyzed systematically and combined with the most recent crystallographic studies. In view of the renewed interest in neuroactive molecules, this review aims to help guide the efforts of organic synthesis laboratories, as well as to inform newcomers to KA/GluK research.

Kainic Acid Impairs the Memory Behavior of APP23 Mice by Increasing Brain Amyloid Load through a Tumor Necrosis Factor-α-Dependent Mechanism

Kainic acid (KA) was recently identified as an epileptogenic and neuroexcitotoxic agent that is responsible for inducing learning and memory deficits in various neurodegenerative diseases, such as Alzheimer's disease (AD). However, the mechanism by which KA acts upon AD remains unclear. To this end, we presently investigated the roles of KA in processing amyloid-β protein precursor (AβPP) and amyloid-β protein (Aβ) loads during the course of AD development and progression. Specifically, KA treatment clearly caused the upregulation of tumor necrosis factor α (TNF-α) via activation of the PI3-K/AKT, ERK1/2, and p65 pathways in glial cells. TNF-α secreted from glial cells was then found to be responsible for stimulating the expression of BACE-1 and PS1/2, which resulted in the production and deposition of Aβ in neurons. Finally, the accumulation and aggregation of Aβ lead to the cognitive decline of APP23 mice. These results indicate that KA accelerates the progression of AD by inducing the crosstalk between glial cells and neurons.

Scalable Biosynthesis of the Seaweed Neurochemical, Kainic Acid

Kainic acid, the flagship member of the kainoid family of natural neurochemicals, is a widely used neuropharmacological agent that helped unravel the key role of ionotropic glutamate receptors, including the kainate receptor, in the central nervous system. Worldwide shortages of this seaweed natural product in the year 2000 prompted numerous chemical syntheses, including scalable preparations with as few as six-steps. Herein we report the discovery and characterization of the concise two-enzyme biosynthetic pathway to kainic acid from l-glutamic acid and dimethylallyl pyrophosphate in red macroalgae and show that the biosynthetic genes are co-clustered in genomes of Digenea simplex and Palmaria palmata. Moreover, we applied a key biosynthetic α-ketoglutarate-dependent dioxygenase enzyme in a biotransformation methodology to efficiently construct kainic acid on the gram scale. This study establishes both the feasibility of mining seaweed genomes for their biotechnological prowess.

Downregulation of 14-3-3 Proteins in a Kainic Acid-Induced Neurotoxicity Model

The 14-3-3 proteins are among the most abundant proteins expressed in the brain, comprising about 1% of the total amount of soluble brain proteins. Through phosphoserine- and phosphothreonine-binding motifs, 14-3-3 proteins regulate many signaling proteins and cellular processes including cell death. In the present study, we utilized a well-known kainic acid (KA)-induced excitotoxicity rat model and examined the expression of 14-3-3 and its isoforms in the frontal cortex of KA-treated and control animals. Among the different 14-3-3 isoforms, abundant levels of eta and tau were detected in the frontal cortex, followed by sigma, epsilon, and gamma, while the expression levels of alpha/beta and zeta/delta isoforms were low. Compared to the control animals, KA treatment induced a significant downregulation of the overall 14-3-3 protein level as well as the levels of the abundant isoforms eta, tau, epsilon, and gamma. We also investigated two 14-3-3-interacting proteins that are involved in the cell death process: Bcl-2-associated X (BAX) and extracellular signal-regulated kinase (ERK). Both BAX and phosphorylated ERK showed increased levels following KA treatment. Together, these findings demonstrate an abundance of several 14-3-3 isoforms in the frontal cortex and that KA treatment can cause a downregulation of 14-3-3 expression and an upregulation of 14-3-3-interacting proteins BAX and phospho-ERK. Thus, downregulation of 14-3-3 proteins could be one of the early molecular events associated with excitotoxicity. This could lead to subsequent upregulation of 14-3-3-binding proteins such as BAX and phospho-ERK that contribute to further downstream apoptosis processes, eventually leading to cell death. Maintaining sufficient levels of 14-3-3 expression and function may become a target of therapeutic intervention for excitotoxicity-induced neurodegeneration.

Embelin Prevents Seizure and Associated Cognitive Impairments in a Pentylenetetrazole-Induced Kindling Zebrafish Model

Epilepsy is a neuronal disorder associated with several neurological and behavioral alterations characterized by recurrent spontaneous epileptic seizures. Despite having more than 20 anti-epileptic drugs (AEDs), they only provide a symptomatic treatment. As well as, currently available AEDs also displayed cognitive alterations in addition to retarding seizure. This leads to the need for exploring new molecules that not only retard seizure but also improve cognitive impairment. Embelin (EMB) is a benzoquinone derivative which has already demonstrated its pharmacological potentials against arrays of neurological conditions. The current study developed a chronic kindling model in adult zebrafish by using repeated administration of small doses of pentylenetetrazole (PTZ) and a single dose of Kainic acid (KA) to investigate the associated memory impairment. This has been done by using the three-axis maze which is a conventional method to test the learning ability and egocentric memory in zebrafish. As well as, the ameliorative potential of EMB has been evaluated against chronic epilepsy-related memory alterations. Moreover the expression level of pro-inflammatory genes such as C-C motif ligand 2 (CCL2), toll-like receptor-4 (TLR4), tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) and interferon-γ (IFN-γ) were evaluated. The level of several neurotransmitters such as γ-aminobutyric acid (GABA), acetylcholine (Ach) and glutamate (Glu) was evaluated by liquid chromatography-mass spectrometry (LC-MS). The results showed that daily dose of PTZ 80 mg/kg for 10 days successfully induces a kindling effect in zebrafish, whereas the single dose of KA did not. As compared to control, the PTZ and KA group demonstrates impairment in memory as demonstrated by the three-axis maze. The PTZ group treated with a series of EMB doses (ranging from 0.156 to 0.625 mg/kg) was found to have retarded seizure as well as significantly reduces epilepsy-induced memory alteration. In addition, EMB treatment reduces the expression of inflammatory markers implicating its anti-inflammatory potential. Moreover, levels of GABA, Ach, and glutamate are increased in EMB administered group as compared to the PTZ administered group. Overall, findings demonstrate that EMB might be a potential candidate against chronic epilepsy-related cognitive dysfunction as EMB prevents the seizures, so we expect it to prevent the associated neuroinflammation and learning deficit.

Promising Neuroprotective Function for M2 Microglia in Kainic Acid-Induced Neurotoxicity Via the Down-Regulation of NF-κB and Caspase 3 Signaling Pathways

Activated microglia have two functional states (M1 and M2) which play dual roles in neurodegenerative diseases. In the present study, we explored a possible neuroprotective function of M2 microglia against kainic acid (KA)-induced neurodegeneration in primary neurons co-cultured with different microglial populations. Neurons were isolated from the hippocampi and cortices of C57BL/6 embryos (embryonic day 16) and microglia were extracted from neonatal pups (postnatal days 0-2). Microglia were either unstimulated (M0-phenotype) or stimulated with lipopolysaccharide and interferon-γ to form the M1-phenotype, or with interleukin (IL)-4, IL-10, and transforming growth factor -β for the M2-phenotype. Neurons were co-cultured with each of the three microglial phenotypes and treated with KA for 24 h. Next, we analyzed the cell survival rate, nitric oxide (NO) levels, and lactate dehydrogenase production, cytokines levels, and expression of nuclear factor κB (NF-κB) and caspase 3 among the three groups before and after KA insult. Our results indicated that M2 microglia played a neuroprotective role in KA-induced neurotoxicity, as demonstrated by high neuronal survival as well as decreased production of NO and pro-inflammatory cytokines. In contrast, neurons co-cultured with M1 microglia exhibited the lowest survival rate as well as increased levels of NO and pro-inflammatory cytokines. Further, the expression of NF-κB and caspase 3 were significantly decreased in M2 microglia co-cultures compared to M1 or M0 microglia co-cultures after KA insult. Therefore, M2 microglia may exert a neuroprotective function in KA-induced neurotoxicity via the down-regulation of NF-κB and caspase 3 signaling pathways.

The validation of Short Interspersed Nuclear Elements (SINEs) as a RT-qPCR normalization strategy in a rodent model for temporal lobe epilepsy

Background

In gene expression studies via RT-qPCR many conclusions are inferred by using reference genes. However, it is generally known that also reference genes could be differentially expressed between various tissue types, experimental conditions and animal models. An increasing amount of studies have been performed to validate the stability of reference genes. In this study, two rodent-specific Short Interspersed Nuclear Elements (SINEs), which are located throughout the transcriptome, were validated and assessed against nine reference genes in a model of Temporal Lobe Epilepsy (TLE). Two different brain regions (i.e. hippocampus and cortex) and two different disease stages (i.e. acute phase and chronic phase) of the systemic kainic acid rat model for TLE were analyzed by performing expression analyses with the geNorm and NormFinder algorithms. Finally, we performed a rank aggregation analysis and validated the reference genes and the rodent-specific SINEs (i.e. B elements) individually via Gfap gene expression.

Results

GeNorm ranked Hprt1, Pgk1 and Ywhaz as the most stable genes in the acute phase, while Gusb and B2m were ranked as the most unstable, being significantly upregulated. The two B elements were ranked as most stable for both brain regions in the chronic phase by geNorm. In contrast, NormFinder ranked the B1 element only once as second best in cortical tissue for the chronic phase. Interestingly, using only one of the two algorithms would have led to skewed conclusions. Finally, the rank aggregation method indicated the use of the B1 element as the best option to normalize target genes, independent of the disease progression and brain region. This result was supported by the expression profile of Gfap.

Conclusion

In this study, we demonstrate the potential of implementing SINEs -notably the B1 element- as a stable normalization factor in a rodent model of TLE, independent of brain region or disease progression.

Neurobiology and Therapeutic Potential of Cyclooxygenase-2 (COX-2) Inhibitors for Inflammation in Neuropsychiatric Disorders

Neuropsychiatric disorders, such as depression, bipolar disorder, schizophrenia, obsessive-compulsive disorder, and neurodevelopmental disorders such as autism spectrum disorder, are associated with significant illness burden. Accumulating evidence supports an association between these disorders and inflammation. Consequently, anti-inflammatory agents, such as the cyclooxygenase-2 inhibitors, represent a novel avenue to prevent and treat neuropsychiatric illness. In this paper, we first review the role of inflammation in psychiatric pathophysiology including inflammatory cytokines' influence on neurotransmitters, the hypothalamic-pituitary-adrenal axis, and microglial mechanisms. We then discuss how cyclooxygenase-2-inhibitors influence these pathways with potential therapeutic benefit, with a focus on celecoxib, due to its superior safety profile. A search was conducted in PubMed, Embase, and PsychINFO databases, in addition to Clinicaltrials.gov and the Stanley Medical Research Institute trial registries. The results were presented as a narrative review. Currently available outcomes for randomized controlled trials up to November 2017 are also discussed. The evidence reviewed here suggests cyclooxygenase-2 inhibitors, and in particular celecoxib, may indeed assist in treating the symptoms of neuropsychiatric disorders; however, further studies are required to assess appropriate illness stage-related indication.

Effect of early-life inflammation and magnesium sulfate on hyperthermia-induced seizures in infant rats: Susceptibility to pentylenetetrazol-induced seizures later in life

This study investigated the effect of inflammation and MgSO₄ pretreatment on behaviors caused by hyperthermia (HT) and the effect of these interventions on PTZ-induced seizure a week later. In this experimental study, rat pups experienced inflammation on postnatal day 10 (P10). On P18-19, the pups received either saline or MgSO₄ then subjected to hyperthermia. On P25-26, PTZ-induced seizure was initiated in the rats. Neonatal inflammation increased the susceptibility to HT-induced seizure. Inflammation and HT increased the susceptibility to PTZ-induced seizure. Pretreatment with MgSO₄ before hyperthermia decreased the susceptibility to both HT- and PTZ-induced seizure. Furthermore, calcium and magnesium blood levels significantly decreased compared to control rats. It can be concluded that neonatal inflammation potentiates while pretreatment with MgSO₄ attenuates HT-induced seizures. Also, neonatal inflammation and HT potentiate PTZ-induced seizure initiated one week later.

Neurotoxic Agent-Induced Injury in Neurodegenerative Disease Model: Focus on Involvement of Glutamate Receptors

Glutamate receptors play a crucial role in the central nervous system and are implicated in different brain disorders. They play a significant role in the pathogenesis of neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Although many studies on NDDs have been conducted, their exact pathophysiological characteristics are still not fully understood. In in vivo and in vitro models of neurotoxic-induced NDDs, neurotoxic agents are used to induce several neuronal injuries for the purpose of correlating them with the pathological characteristics of NDDs. Moreover, therapeutic drugs might be discovered based on the studies employing these models. In NDD models, different neurotoxic agents, namely, kainic acid, domoic acid, glutamate, β-N-Methylamino-L-alanine, amyloid beta, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1-methyl-4-phenylpyridinium, rotenone, 3-Nitropropionic acid and methamphetamine can potently impair both ionotropic and metabotropic glutamate receptors, leading to the progression of toxicity. Many other neurotoxic agents mainly affect the functions of ionotropic glutamate receptors. We discuss particular neurotoxic agents that can act upon glutamate receptors so as to effectively mimic NDDs. The correlation of neurotoxic agent-induced disease characteristics with glutamate receptors would aid the discovery and development of therapeutic drugs for NDDs.

Microglial TREM2/DAP12 Signaling: A Double-Edged Sword in Neural Diseases

Microglia are activated after neuronal injury and in neurodegenerative diseases, and trigger neuroinflammation in the central nervous system (CNS). Microglia-derived neuroinflammation has both beneficial and detrimental effects on neurons. Because the timing and magnitude of microglial activation is thought to be a critical determinant of neuronal fate, understanding the molecular mechanisms underlying microglial activation is required to enable establishment of microglia-targeted therapies for neural diseases. Plasma membrane receptors play primary roles as activators of microglia and in this review, we focus on a receptor complex involving triggering receptor expressed on myeloid cells 2 (TREM2) and DNAX-activating protein of 12 kDa (DAP12), both of which are causative genes for Nasu-Hakola disease, a dementia with bone cysts. Recent transcriptome approaches demonstrated TREM2/DAP12 signaling as the principal regulator that transforms microglia from a homeostatic to a neural disease-associated state. Furthermore, animal model studies revealed critical roles for TREM2/DAP12 in the regulation of microglial activity, including survival, phagocytosis, and cytokine production, not only in Alzheimer's disease but also in other neural diseases, such as Parkinson's disease, demyelinating disease, ischemia, and peripheral nerve injury. Intriguingly, while TREM2/DAP12-mediated microglial activation is detrimental for some diseases, including peripheral nerve injury, it is beneficial for other diseases. As the role of activated microglia differs among disease models, TREM2/DAP12 signaling may result in different outcomes in different diseases. In this review we discuss recent perspectives on the role of TREM2/DAP12 in microglia and their contribution to neural diseases.