Kainate-induced genes in the hippocampus: lessons from expression patterns

Neuronal activation affects the organization and protein composition of the nuclear speckles

Nuclear speckles, also known as interchromatin granule clusters (IGCs), are subnuclear domains highly enriched in proteins involved in transcription and mRNA metabolism and, until recently, have been regarded primarily as their storage and modification hubs. However, several recent studies on non-neuronal cell types indicate that nuclear speckles may directly contribute to gene expression as some of the active genes have been shown to associate with these structures. Neuronal activity is one of the key transcriptional regulators and may lead to the rearrangement of some nuclear bodies. Notably, the impact of neuronal activation on IGC/nuclear speckles organization and function remains unexplored. To address this research gap, we examined whether and how neuronal stimulation affects the organization of these bodies in granular neurons from the rat hippocampal formation. Our findings demonstrate that neuronal stimulation induces morphological and proteomic remodelling of the nuclear speckles under both in vitro and in vivo conditions. Importantly, these changes are not associated with cellular stress or cell death but are dependent on transcription and splicing.

Extracellular Matrix Recycling as a Novel Plasticity Mechanism With a Potential Role in Disease

The extracellular matrix (ECM) stabilizes neural circuits and synapses in the healthy brain, while also retaining the ability to be remodeled, to allow synapses to be plastic. A well-described mechanism for ECM remodeling is through the regulated secretion of proteolytic enzymes at the synapse, together with the synthesis of new ECM molecules. The importance of this process is evidenced by the large number of brain disorders that are associated with a dysregulation of ECM-cleaving protease activity. While most of the brain ECM molecules are indeed stable for remarkable time periods, evidence in other cell types, as cancer cells, suggests that at least a proportion of the ECM molecules may be endocytosed regularly, and could even be recycled back to the ECM. In this review, we discuss the involvement of such a mechanism in the brain, under physiological activity conditions and in relation to synapse and brain disease.

Cnestis ferruginea Vahl ex DC (Connaraceae) downregulates expression of immediate early genes in kainic acid-induced temporal lobe epilepsy in mice

OBJECTIVES

This study investigates the influence of Cnestis ferruginea (CF) on kainic acid (KA)-induced immediate early genes (IEGs) associated with hippocampal sclerosis in temporal lobe epilepsy (TLE) in mice.

METHODS

Animals were randomly divided into preventive treatment; vehicle (10 mL/kg, p.o.) or CF (400 mg/kg, p.o.) for three consecutive days before KA (5 mg/kg, i.p.) on days 4 and 5. In the reversal model, KA (5 mg/kg, i.p.) was administered on days 1 and 2 before CF (400 mg/kg) administration on days 3-5. Animals were euthanized on day 5, 6 h after KA exposure in preventive model and 1 h after CF administration in reversal model to estimate markers of IEGs.

RESULTS

KA upregulated the expression of c-Fos protein by 3.32-, 9.45-, 8.13-, and 8.66-fold in the hippocampal CA1, CA2, CA3, and DG regions, respectively. Also, KA elevated inducible nitric oxide synthase protein expression by 10.9-, 10.6-, 9.78-, and 9.51-fold. Besides, mRNA expression of brain-derived neurotrophic factors and heat shock protein was increased by 2.38- and 1.39-fold, respectively, after exposure to KA which were attenuated by CF.

CONCLUSIONS

CF attenuated KA-induced IEGs and could be used as an adjunct in TLE.

Advances in the Potential Biomarkers of Epilepsy

Epilepsy is a group of chronic neurological disorders characterized by recurrent, spontaneous, and unpredictable seizures. It is one of the most common neurological disorders, affecting tens of millions of people worldwide. Comprehensive studies on epilepsy in recent decades have revealed the complexity of epileptogenesis, in which immunological processes, epigenetic modifications, and structural changes in neuronal tissues have been identified as playing a crucial role. This review discusses the recent advances in the biomarkers of epilepsy. We evaluate the possible molecular background underlying the clinical changes observed in recent studies, focusing on therapeutic investigations, and the evidence of their safety and efficacy in the human population. This article reviews the pathophysiology of epilepsy, including recent reports on the effects of oxidative stress and hypoxia, and focuses on specific biomarkers and their clinical implications, along with further perspectives in epilepsy research.

Exposing immature hippocampal neurons to excitotoxins reveals distinct transcriptome and protein regulation with induction of common survival signaling pathways

Early life traumas lead to neuroprotection by preconditioning mechanisms. To determine which genes and pathways are most likely involved in specific adaptive effects, immature hippocampal cultures were exposed to a single high dose of glutamate (250 μM), NMDA (100 μM), or KA (300 μM) for 48 h (5-7 DIV) based on our prior "two hit" in vitro model of preconditioning. Transcriptome profiling and immunocytochemistry of gene candidates were performed 7 days later when cultured neurons mature (14 DIV). Many genes were up- and down- regulated involving distinct Ca²⁺-binding protein families, G-coupled proteins, various growth factors, synaptic vesicle docking factors, certain neurotransmitter receptors, heat shock, oxidative stress, and certain anti-apoptotic Bcl-2 gene members that influence neuronal survival. Immunohistochemistry showed a marked decrease in the number of Calb1 and Calm2 positive neurons following NMDA but not after glutamate exposure whereas ryanodine and Cav1.2 voltage gated channel expression was less affected. Survivors had marked increases in Calm2 immunostaining; however, high-density neural clusters observed in controls, were depleted after NMDA and partly diminished after glutamate. While NR1 mRNA expression was decreased in the microarray, specific antibodies revealed selective loss of the NR1C1 splice variant. Calm2 which can inactivate NMDA receptors by binding to C1 but not C2 regions of its NR1 subunit suggests that loss of the C1 splice variant will reduce co-regulation with Calm2 and alter NR1 trafficking, phosphorylation, and NMDA currents following early life NMDA exposure. A dramatic reduction in the density of GABAAα5 and GABAB receptor expressing neurons was observed after NMDA exposure but immunodensity measurements were unchanged as was the expression of the GABA synthesizing enzyme, GAD, suggesting that fast inhibitory neurotransmission and response to benzodiazepines and GABAB-mediated IPSPs may be preserved in matured survivors. Selective upregulation of Chat and CNRIP was detected after glutamate treatment suggesting this condition would decrease cholinergic and excitatory neurotransmission by decreasing Ach content and CB1 interacting protein function. This decrease likely contributes to memory and attention tasks deficits that follow a single early neurological insult. Diverse changes that follow overactivation of excitatory networks of immature neurons appear long-lasting or permanent and are expected to have profound effects on network function and adaptive responses to further insult.

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.

Protective effect of compound Danshen (Salvia miltiorrhiza) dripping pills alone and in combination with carbamazepine on kainic acid-induced temporal lobe epilepsy and cognitive impairment in rats

CONTEXT

Temporal lobe epilepsy (TLE) is resistant to antiepileptic drugs (AEDs) and is associated with cognitive impairment. The modern Chinese medicine, compound Danshen dripping pills (CDDP), is clinically effective in treating epilepsy and improving cognitive impairment.

OBJECTIVE

This study evaluated the protective effects of CDDP alone and in combination with carbamazepine (CBZ) on kainic acid-induced TLE and cognitive impairment in rats.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into five groups: control (sham operated), model, CDDP, CBZ and combined. A TLE model was then created via bilateral intrahippocampal injection of 0.35 μg kainic acid (KA). Rats received CDDP (85 mg/kg), CBZ (100 mg/kg) or combined (85 mg/kg CDDP +100 mg/kg CBZ) via intragastric administration for 90 d, respectively. Seizure intensity, apoptosis and glial cell line-derived neurotrophic factor (GDNF) were measured. Furthermore, the improvement in cognitive impairment and hippocampal neuronal damage was evaluated.

RESULTS

CDDP combined with CBZ significantly decreased seizure severity and frequency (p < 0.05) and ameliorated cognitive impairment (p < 0.05). The model group showed a significant reduction of neurons and Bcl-2/Bax expression in the hippocampus CA3 area (p < 0.01), the combined groups significantly reversed these change (p < 0.01). GDNF expression in the combined groups showed a clear increase over the model group (p < 0.05).

CONCLUSION

These findings support the use of CDDP as an adjuvant drug for the treatment of TLE and cognitive deficit. Its mechanism might be related to an anti-apoptosis effect and up-regulation of GDNF.

Neuroprotective effect of Arthrospira (Spirulina) platensis against kainic acid-neuronal death

Context Arthrospira (Spirulina) platensis (SP) is a cyanobacterium which has attracted attention because of its nutritional value and pharmacological properties. It was previously reported that SP reduces oxidative stress in the hippocampus and protects against damaging neurobehavioural effects of systemic kainic acid (KA). It is widely known that the systemic administration of KA induces neuronal damage, specifically in the CA3 hippocampal region. Objective The present study determines if the SP sub-chronic treatment has neuroprotective properties against KA. Materials and methods Male SW mice were treated with SP during 24 d, at doses of 0, 200, and 800 mg/kg, once daily, and with KA (35 mg/kg, ip) as a single dose on day 14. After the treatment, a histological analysis was performed and the number of atrophic neuronal cells in CA3 hippocampal region was quantified. Results Pretreatment with SP does not protect against seizures induced by KA. However, mortality in the SP 200 and the SP 800 groups was of 20%, while for the KA group, it was of 60%. A single KA ip administration produced a considerable neuronal damage, whereas both doses of SP sub-chronic treatment reduced the number of atrophic neurons in CA3 hippocampal region with respect to the KA group. Discussion The SP neurobehaviour improvement after KA systemic administration correlates with the capacity of SP to reduce KA-neuronal death in CA3 hippocampal cells. This neuroprotection may be related to the antioxidant properties of SP. Conclusion SP reduces KA-neuronal death in CA3 hippocampal cells.

Sinapic Acid and Its Derivatives as Medicine in Oxidative Stress-Induced Diseases and Aging

Sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid) is an orally bioavailable phytochemical, extensively found in spices, citrus and berry fruits, vegetables, cereals, and oilseed crops and is known to exhibit antioxidant, anti-inflammatory, anticancer, antimutagenic, antiglycemic, neuroprotective, and antibacterial activities. The literature reveals that sinapic acid is a bioactive phenolic acid and has the potential to attenuate various chemically induced toxicities. This minireview is an effort to summarize the available literature about pharmacokinetic, therapeutic, and protective potential of this versatile molecule in health related areas.

Post-status epilepticus treatment with the cannabinoid agonist WIN 55,212-2 prevents chronic epileptic hippocampal damage in rats

Repeated seizures are often associated with development of refractory chronic epilepsy, the most common form of which is temporal lobe epilepsy. G-protein-coupled cannabinoid receptors (CB1 and CB2 receptors) regulate neuronal excitability and have been shown to mediate acute anticonvulsant effects of cannabinoids in animal models. However, the potential of cannabinoids to prevent chronic neuronal damage and development of epilepsy remains unexplored. We hypothesized that treatment with a CB receptor agonist after an episode of status epilepticus--but before development of spontaneous recurrent seizures--might prevent the development of functional changes that lead to chronic epilepsy. Using the rat pilocarpine model, a therapeutic approach was simulated by administering the CB agonist, WIN 55,212-2 after an episode of status epilepticus. Epileptic behavior was monitored during development of spontaneous recurrent seizures for up to 6 months. Histology, neurochemistry, redox status and NMDA receptor subunit expression were assessed at 6 months after pilocarpine-induced seizures. Sub-acute treatment with WIN 55,212-2 (for 15 days starting 24h after PILO injection) dramatically attenuated the severity, duration and frequency of spontaneous recurrent seizures. Further, in contrast to vehicle-treated animals, hippocampi from WIN 55,212-2-treated animals showed: normal thiol redox state, normal NR2A and NR2B subunit expression, preservation of GABAergic neurons and prevention of abnormal proliferation of GABAergic progenitors. This study shows for the first time that, after a known inciting event, treatment with a compound targeting CB receptors has the potential to prevent the epileptogenic events that result in chronic epileptic damage.

Matrix metalloproteinase-9 involvement in the structural plasticity of dendritic spines

Dendritic spines are the locus for excitatory synaptic transmission in the brain and thus play a major role in neuronal plasticity. The ability to alter synaptic connections includes volumetric changes in dendritic spines that are driven by scaffolds created by the extracellular matrix (ECM). Here, we review the effects of the proteolytic activity of ECM proteases in physiological and pathological structural plasticity. We use matrix metalloproteinase-9 (MMP-9) as an example of an ECM modifier that has recently emerged as a key molecule in regulating the morphology and dysmorphology of dendritic spines that underlie synaptic plasticity and neurological disorders, respectively. We summarize the influence of MMP-9 on the dynamic remodeling of the ECM via the cleavage of extracellular substrates. We discuss its role in the formation, modification, and maintenance of dendritic spines in learning and memory. Finally, we review research that implicates MMP-9 in aberrant synaptic plasticity and spine dysmorphology in neurological disorders, with a focus on morphological abnormalities of dendritic protrusions that are associated with epilepsy.

DP-b99 modulates matrix metalloproteinase activity and neuronal plasticity

DP-b99 is a membrane-activated chelator of zinc and calcium ions, recently proposed as a therapeutic agent. Matrix metalloproteinases (MMPs) are zinc-dependent extracellularly operating proteases that might contribute to synaptic plasticity, learning and memory under physiological conditions. In excessive amounts these enzymes contribute to a number of neuronal pathologies ranging from the stroke to neurodegeneration and epileptogenesis. In the present study, we report that DP-b99 delays onset and severity of PTZ-induced seizures in mice, as well as displays neuroprotective effect on kainate excitotoxicity in hippocampal organotypic slices and furthermore blocks morphological reorganization of the dendritic spines evoked by a major neuronal MMP, MMP-9. Taken together, our findings suggest that DP-b99 may inhibit neuronal plasticity driven by MMPs, in particular MMP-9, and thus may be considered as a therapeutic agent under conditions of aberrant plasticity, such as those subserving epileptogenesis.

Delayed treatments with pharmacological modulators of pre- and postsynaptic mGlu receptors rescue the hippocampus from kainate-induced neurodegeneration

Gene expression of mGluR2, mGluR3 and mGluR5 was evaluated in the hippocampus and frontal cortex in Wistar rats in 1 and 4 weeks after bilateral microinjection of kainic acid into the dorsal hippocampus. The time-course of the receptors' expression suggested their adaptive role in response on the induction of excitotoxicity. It was assumed that the decrease of kainate-induced neurodegeneration could be achieved through simultaneous activation of presynaptic mGluRs and inhibition of mGlu postsynaptic receptors. Both negative allosteric modulator of mGluR5, MPEP, and agonist of mGluR2, LY354740, were administered intraperitoneally 5 days after microinjection of kainic acid. As shown by histochemical studies with cresyl violet and Fluoro-Jade, kainate induced significant damage of hippocampal neurons in the CA3 and CA1 fields. Pharmacological treatment with the negative modulator of mGlu5 receptors in common with the agonist of mGluR2 decreased kainate-induced neurodegeneration in dorsal hippocampus.

Effects of nateglinide and repaglinide administered intracerebroventricularly on the CA3 hippocampal neuronal cell death and hyperglycemia induced by kainic acid in mice

Meglitinides (nateglinide and repaglinide) are widely used oral drugs for the treatment of type II diabetes mellitus. In the present study, the effects of meglinitides administered supraspinally on kainic acid (KA)-induced hippocampal neuronal cell death and hyperglycemia were studied in ICR mice. Mice were pretreated intracerebroventricularly (i.c.v.) with 30 μg of nateglinide and repaglinide for 10 min and then, mice were administered i.c.v. with KA (0.1 μg). The neuronal cell death in the CA3 region in the hippocampus was assessed 24h after KA administration and the blood glucose level was measured 30, 60, and 120 min after KA administration. We found that i.c.v. pretreatment with repaglinide attenuated the KA-induced neuronal cell death in CA3 region of the hippocampus and hyperglycemia. However, nateglinide pretreated i.c.v. did not affect the KA-induced neuronal cell death and hyperglycemia. In addition, KA administered i.c.v. caused an elevation of plasma corticosterone level and a reduction of the plasma insulin level. Furthermore, i.c.v. pretreatment with repaglinide attenuated KA-induced up-regulation of plasma corticosterone level. Furthermore, i.c.v. administration of repaglinide alone increased plasma insulin level and repaglinide pretreated i.c.v. caused a reversal of KA-induced hypoinsulinemic effect. Our results suggest that supraspinally administered repaglinide, but not nateglinide, exerts a protective effect against the KA-induced neuronal cells death in CA3 region of the hippocampus. The neuroprotective effect of repaglinide appears to be mediated by lowering the blood glucose level induced by KA.

Neural ECM proteases in learning and synaptic plasticity

Recent studies implicate extracellular proteases in synaptic plasticity, learning, and memory. The data are especially strong for such serine proteases as thrombin, tissue plasminogen activator, neurotrypsin, and neuropsin as well as matrix metalloproteinases, MMP-9 in particular. The role of those enzymes in the aforementioned phenomena is supported by the experimental results on the expression patterns (at the gene expression and protein and enzymatic activity levels) and functional studies, including knockout mice, specific inhibitors, etc. Counterintuitively, the studies have shown that the extracellular proteolysis is not responsible mainly for an overall degradation of the extracellular matrix (ECM) and loosening perisynaptic structures, but rather allows for releasing signaling molecules from the ECM, transsynaptic proteins, and latent form of growth factors. Notably, there are also indications implying those enzymes in the major neuropsychiatric disorders, probably by contributing to synaptic aberrations underlying such diseases as schizophrenia, bipolar, autism spectrum disorders, and drug addiction.

Role of α-CGRP in the regulation of neurotoxic responses induced by kainic acid in mice

Kainic acid (KA) is an excitatory and neurotoxic substance. The role of α-calcitonin gene-related peptide (α-CGRP) in the regulation of KA-induced hippocampal neuronal cell death was investigated in the present study. The intracerebroventricular (i.c.v.) administration with KA (0.07 μg) increased hippocampal α-CGRP mRNA level in ICR mice. The α-CGRP mRNA level began to increase at 1h, reached at maximal level at 6 and 12h, and returned to the control level by 24h after i.c.v. administration with KA. In addition, KA-induced hippocampal CA3 neuronal death in C57BL6 (wild type) group was more pronounced compared to KA-induced hippocampal CA3 pyramidal cell death in α-CGRP knock-out (KO) group. Furthermore, sumatriptan, a CGRP releasing inhibitor, significantly protected the pyramidal cell death in CA3 hippocampal region induced by KA administered i.c.v. in ICR mice. Our results suggest that α-CGRP may play an important role in the regulation of KA-induced pyramidal cell death in CA3 region of the hippocampus.

Changes in the Density of Nitrergic Neurons in the Hippocampus of Rats Following Kainic Acid and Melatonin Administration

Nitric oxide (NO) may play a role in the pathophysiology of excitotoxicity. It is also possible that increase in Ca2+ overload and NO-mediated events are involved in neuronal loss during excitotoxicity. Using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry, we have investigated the effects of melatonin on NADPH-d positive hippocampal neurons after kainic acid (KA) induced excitotoxicity in female rats of Wistar strain. Cytosolic Ca2+ (free calcium) in all the respective experimental groups was also studied. Kainic acid was administered, with a single dose of 10 mg/kg/bw (body weight) to the animals. KA treated rats were given melatonin at a dose of 20 mg/kg/bw (for 14 day). On the last day of treatment, animals were transcardially perfused with 4 % paraformaldehyde under deep thiopental anaesthesia. Cryostat sections (20 µm) were cut and stained for NADPH-d positive neurons. KA exposed animals showed a significantly increased number of NADPH-d positive neurons in the dorsal and ventral blade of the dentate gyrus (DG), hilus, CA1 and CA3 area of hippocampus, with a parallel increase in intracellular free Ca2+ ion concentration, as compared to the control group. KA + melatonin-treated animal groups showed reduced number of NADPH-d positive neurons in DG, hilus, CA1 and CA3 areas and a decline in cytosolic Ca2+ concentration, as compared to KA treated group. Our study suggests that the enhanced levels of cytosolic Ca2+ and nitric oxide (NO) play an important role in kainate induced excitotoxicity. Inhibition of NO production may be another means whereby melatonin can reduce oxidative damage and seems to play important role in neuroprotection.

Novel higher-order epigenetic regulation of the Bdnf gene upon seizures

Studies in cultured cells have demonstrated the existence of higher-order epigenetic mechanisms, determining the relationship between expression of the gene and its position within the cell nucleus. It is unknown, whether such mechanisms operate in postmitotic, highly differentiated cell types, such as neurons in vivo. Accordingly, we examined whether the intranuclear positions of Bdnf and Trkb genes, encoding the major neurotrophin and its receptor respectively, change as a result of neuronal activity, and what functional consequences such movements may have. In a rat model of massive neuronal activation upon kainate-induced seizures we found that elevated neuronal expression of Bdnf is associated with its detachment from the nuclear lamina, and translocation toward the nucleus center. In contrast, the position of stably expressed Trkb remains unchanged after seizures. Our study demonstrates that activation-dependent architectural remodeling of the neuronal cell nucleus in vivo contributes to activity-dependent changes in gene expression in the brain.

Activity-dependent local translation of matrix metalloproteinase-9

Local, synaptic synthesis of new proteins in response to neuronal stimulation plays a key role in the regulation of synaptic morphogenesis. Recent studies indicate that matrix metalloproteinase-9 (MMP-9), an endopeptidase that regulates the pericellular environment through cleavage of its protein components, plays a critical role in regulation of spine morphology and synaptic plasticity. Here, we sought to determine whether MMP-9 mRNA is transported to dendrites for local translation and protein release. First, dendritic transport of MMP-9 mRNA was seen in primary hippocampal neuronal cultures treated with glutamate and in dentate gyrus granule cells in adult anesthetized rats after induction of long-term potentiation. Second, rapid, activity-dependent polyadenylation of MMP-9 mRNA; association of the mRNA with actively translating polysomes; and de novo MMP-9 protein synthesis were obtained in synaptoneurosomes isolated from rat hippocampus. Third, glutamate stimulation of cultured hippocampal neurons evoked a rapid (in minutes) increase in MMP-9 activity, as measured by cleavage of its native substrate, β-dystroglycan. This activity was reduced by the polyadenylation inhibitor, thus linking MMP-9 translation with protein function. In aggregate, our findings show that MMP-9 mRNA is transported to dendrites and locally translated and that the protein is released in an activity-dependent manner. Acting in concert with other dendritically synthesized proteins, locally secreted MMP-9 may contribute to the structural and functional plasticity of the activated synapses.

Differential patterns of synaptotagmin7 mRNA expression in rats with kainate- and pilocarpine-induced seizures

Previous studies in rat models of neurodegenerative disorders have shown disregulation of striatal synaptotagmin7 mRNA. Here we explored the expression of synaptotagmin7 mRNA in the brains of rats with seizures triggered by the glutamatergic agonist kainate (10 mg/kg) or by the muscarinic agonist pilocarpine (30 mg/kg) in LiCl (3 mEq/kg) pre-treated (24 h) rats, in a time-course experiment (30 min-1 day). After kainate-induced seizures, synaptotagmin7 mRNA levels were transiently and uniformly increased throughout the dorsal and ventral striatum (accumbens) at 8 and 12 h, but not at 24 h, followed at 24 h by somewhat variable upregulation within different parts of the cerebral cortex, amigdala and thalamic nuclei, the hippocampus and the lateral septum. By contrast, after LiCl/pilocarpine-induced seizures, there was a more prolonged increase of striatal Synaptotagmin7 mRNA levels (at 8, 12 and 24 h), but only in the ventromedial striatum, while in some other of the aforementioned brain regions there was a decline to below the basal levels. After systemic post-treatment with muscarinic antagonist scopolamine in a dose of 2 mg/kg the seizures were either extinguished or attenuated. In scopolamine post-treated animals with extinguished seizures the striatal synaptotagmin7 mRNA levels (at 12 h after the onset of seizures) were not different from the levels in control animals without seizures, while in rats with attenuated seizures, the upregulation closely resembled kainate seizures-like pattern of striatal upregulation. In the dose of 1 mg/kg, scopolamine did not significantly affect the progression of pilocarpine-induced seizures or pilocarpine seizures-like pattern of striatal upregulation of synaptotagmin7 mRNA. In control experiments, equivalent doses of scopolamine per se did not affect the expression of synaptotagmin7 mRNA. We conclude that here described differential time course and pattern of synaptotagmin7 mRNA expression imply regional differences of pathophysiological brain activation and plasticity in these two models of seizures.

Kainic acid-induced changes in the opioid/nociceptin system and the stress/toxicity pathways in the rat hippocampus

Excitotoxicity is a contributing factor to the pathogenesis of acute or chronic neurodegenerative disease states. Kainic acid (KA) is an excitotoxic substance and the administration of it to rodents induces seizure activity (status epilepticus, SE) and leads to neurodegeneration. In this study the effect of KA-induced excitotoxicity on the G-protein activations and the gene expression levels of the opioid/nociceptin system receptors as MOPr, KOPr, DOPr, ORL-1, and PNOC (N/OFQ) were investigated, and the regulator effect of naloxone (Nal) on the gene expressions of the opioid system receptors against KA-induced seizures in the rat hippocampus was tested. In addition, the expression levels of stress-toxicity genes were assessed in the hippocampus following KA-induced excitotoxicity in order to determine the potential genetic targets which can be helpful for neuroprotective interventions. Our results indicate that the KA-induced excitotoxicity increased the mRNA levels of MOPr, DOPr, KOPr, PNOC, and ORL-1. However, G-protein activations of MOPr, DOPr, and KOPr remained relatively unchanged while both the potency and efficacy of N/OFQ were significantly increased. The PCR array data showed that KA-induced excitotoxicity altered the expression levels of genes in the cellular stress or toxicity pathways. Our data suggests that the induction of the opioid/nociceptin system may be involved in the cellular stress response following a neurodegenerative insult and that the genes modulated by the KA-treatment in the stress-toxicity pathways may be evaluated as targets of potential neuroprotective interventions.

Tamalin is a critical mediator of electroconvulsive shock-induced adult neuroplasticity

The molecular mechanisms underlying the effects of electroconvulsive shock (ECS) therapy, a fast-acting and very effective antidepressant therapy, are poorly understood. Changes related to neuroplasticity, including enhanced adult hippocampal neurogenesis and neuronal arborization, are believed to play an important role in mediating the effects of ECS. Here we show a dynamic upregulation of the scaffold protein tamalin, selectively in the hippocampus of animals subjected to ECS. Interestingly, this gene upregulation is functionally significant because tamalin deletion in mice abrogated ECS-induced neurogenesis in the adult mouse hippocampus. Furthermore, loss of tamalin blunts mossy fiber sprouting and dendritic arborization caused by ECS. These data suggest an essential role for tamalin in ECS-induced adult neuroplasticity and provide new insight into the pathways that are involved in mediating ECS effects.

COMPUTATIONAL NEUROGENETIC MODELLING: A PATHWAY TO NEW DISCOVERIES IN GENETIC NEUROSCIENCE

The paper presents a methodology for using computational neurogenetic modelling (CNGM) to bring new original insights into how genes influence the dynamics of brain neural networks. CNGM is a novel computational approach to brain neural network modelling that integrates dynamic gene networks with artificial neural network model (ANN). Interaction of genes in neurons affects the dynamics of the whole ANN model through neuronal parameters, which are no longer constant but change as a function of gene expression. Through optimization of interactions within the internal gene regulatory network (GRN), initial gene/protein expression values and ANN parameters, particular target states of the neural network behaviour can be achieved, and statistics about gene interactions can be extracted. In such a way, we have obtained an abstract GRN that contains predictions about particular gene interactions in neurons for subunit genes of AMPA, GABAA and NMDA neuro-receptors. The extent of sequence conservation for 20 subunit proteins of all these receptors was analysed using standard bioinformatics multiple alignment procedures. We have observed abundance of conserved residues but the most interesting observation has been the consistent conservation of phenylalanine (F at position 269) and leucine (L at position 353) in all 20 proteins with no mutations. We hypothesise that these regions can be the basis for mutual interactions. Existing knowledge on evolutionary linkage of their protein families and analysis at molecular level indicate that the expression of these individual subunits should be coordinated, which provides the biological justification for our optimized GRN.

Metabolic gene expression changes in the hippocampus of obese epileptic male rats in the pilocarpine model of temporal lobe epilepsy

Chronically epileptic male adult rats in the pilocarpine model of temporal lobe epilepsy (TLE), exhibited gross expansion of abdominal fat mass and significant weight gain several months after induction of status epilepticus (SE) when compared to control rats. We hypothesized that epileptogenesis can induce molecular changes in the hippocampus that may be associated with metabolism. We determined the expression levels of genes Hsd11b1, Nr3c1, Abcc8, Kcnj11, Mc4r, Npy, Lepr, Bdnf, and Drd2 that are involved in regulation of energy metabolism, in the hippocampus of age-matched control and chronic epileptic animals. Taqman-based quantitative real time polymerase chain reaction (qPCR) and the delta-delta cycle threshold (CT) methods were used for the gene expression assays. Gene expression of Hsd11b1 (cortisol generating enzyme) was significantly higher in epileptic versus control rats at 24h and 2 months, after induction of SE. Nr3c1 (glucocorticoid receptor) mRNA levels on the other hand were down-regulated at 24h, 10 days and 2 months, post SE. Abcc8 (Sur1; subunit of ATP-sensitive potassium (K(ATP)) channel) was significantly down-regulated at 10 days post SE. Kcnj11 (Kir6.2; subunit of ATP-sensitive potassium (K(ATP)) channel) was significantly up-regulated at 24h, 1 month and 2 months post SE. Thus, we demonstrated development of obesity and changes in the expression of metabolic genes in the hippocampus during epileptogenesis in male rats in the pilocarpine model of TLE.

Pilocapine alters NMDA receptor expression and function in hippocampal neurons: NADPH oxidase and ERK1/2 mechanisms

The molecular basis for epileptogenesis remains poorly defined, but repeated or prolonged seizures can cause altered hippocampal N-methyl D-aspartate receptor (NMDAR) stoichiometry, loss of hippocampal neurons, and aberrant mossy fiber sprouting. Using the muscarinic receptor 1 (m1R) agonist, pilocarpine (PILO), in hippocampal cell cultures we explored the early sequence of molecular events that occur within 24h of the initial insult and result in altered neuronal function during epileptogenesis. Our findings show that PILO-induced, m1R-mediated, inositol 1,4,5-trisphosphate (IP3) synthesis constitutes an early, crucial biochemical event required for NMDAR hyperactivation and subsequent NADPH oxidase (NOX) activation and NMDAR-independent ERK1/2 phoshorylation. Together, but not separately, NOX activation and ERK1/2 phosphorylation induce alterations in NMDAR stoichiometry through the upregulation of NR1 and NR2B subunits. Lastly, we demonstrated that PILO-mediated oxidative stress alters NMDAR function through the redox modulation of cysteine residues. The in vitro results related to thiol oxidation, NOX activation, ERK1/2 phosphorylation and NMDAR upregulation were confirmed in vivo, 24h after treatment of adult rats with PILO. These results obtained in PILO-treated primary hippocampal neurons--and confirmed in vivo at the same time-point after PILO--provide a better understanding of the early cellular responses during epileptogenesis and identify potential therapeutic targets to prevent development of chronic epilepsy.

Effects of structural analogues of nociceptin(1-13)NH₂ on brain antioxidant status in kainic acid-treated rats

The in vivo effects of nociceptin (N/OFQ(1-13)NH(2) ) and its structural analogues ([Dab(9) ]N/OFQ(1-13)NH(2) , [Dap(9) ]N/OFQ(1-13)NH(2) and [Cav(9) ]N/OFQ(1-13)NH(2) ) on the levels of lipid peroxidation and cell antioxidants (enzyme and non-enzyme) in brain of control and kainic acid (KA)-treated rats were studied. In control animals, [Dab(9) ]N/OFQ(1-13)NH(2) and [Dap(9) ]N/OFQ(1-13)NH(2) , unlike N/OFQ(1-13)NH(2) and [Cav(9) ]N/OFQ(1-13)NH(2) , slightly increased the brain lipid peroxidation; the rest of the parameters were unchanged by all neuropeptides tested. KA (0.25 µg in 0.5 µl, i.c.v) increased the lipid peroxidation (4 and 24 h after KA-injection) and decreased the glutathione level (1 h after KA-administration). One hour after KA-administration, the neuropeptides (2 µg in 0.5 µl, injected 30 min before KA) showed the following effects: a slight decrease in the KA-induced lipid peroxidation by all nociceptin analogues and an enhancement of the KA-decreased GSH level, but by [Cav(9) ]N/OFQ(1-13)NH(2) only. The brain antioxidant enzyme activities were unchanged in all used experimental groups. In addition, the nociceptin analogues, especially [Can(9) ]N/OFQ(1-13)NH(2) , showed a good antioxidant capacity in chemical systems, generating reactive oxygen species. In conclusion, the substitution of lysin (Lys) in N/OFQ(1-13)NH(2) molecule with other amino acids might contribute to changes in its antioxidant properties. Copyright © 2011 John Wiley & Sons, Ltd.

Metzincin proteases and their inhibitors: foes or friends in nervous system physiology?

Members of the metzincin family of metalloproteinases have long been considered merely degradative enzymes for extracellular matrix molecules. Recently, however, there has been growing appreciation for these proteinases and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs), as fine modulators of nervous system physiology and pathology. Present all along the phylogenetic tree, in all neural cell types, from the nucleus to the synapse and in the extracellular space, metalloproteinases exhibit a complex spatiotemporal profile of expression in the nervous parenchyma and at the neurovascular interface. The irreversibility of their proteolytic activity on numerous biofactors (e.g., growth factors, cytokines, receptors, DNA repair enzymes, matrix proteins) is ideally suited to sustain structural changes that are involved in physiological or postlesion remodeling of neural networks, learning consolidation or impairment, neurodegenerative and neuroinflammatory processes, or progression of malignant gliomas. The present review provides a state of the art overview of the involvement of the metzincin/TIMP system in these processes and the prospects of new therapeutic strategies based on the control of metalloproteinase activity.

Cholinergic regulation of striatal Nova mRNAs

Alternative splicing is an important mechanism for expanding proteome diversity from a limited number of genes, especially in higher vertebrates. Brain-specific splicing factors play an important role in establishing specific patterns of alternative splicing in the brain and thereby contribute to its complex architecture and function. Nova proteins are splicing factors that are expressed specifically in the central nervous system, where they regulate a large number of pre-mRNAs encoding synaptic proteins that are important for the balance of neuronal excitation and inhibition. Since this balance is interrupted in epileptic seizures, we explored whether LiCl/pilocarpine- or kainate-induced epileptic seizures would induce changes in the levels of Nova mRNAs in the rat brain. We found that the muscarinic agonist, pilocarpine, but not the glutamatergic agonist, kainate, induced a significant downregulation of Nova2 mRNA and upregulation of all three Nova1 mRNA isoforms in the striatum. Treatment with the muscarinic antagonist, scopolamine, at the onset of pilocarpine-induced seizures inhibited the seizures and the changes in Nova mRNA levels. Therefore it seems likely that pilocarpine stimulation of muscarinic acetylcholine receptors was a prerequisite for the observed changes, while the contribution of other striatal neurotransmitter systems activated by seizures could not be excluded. We propose that the LiCl/pilocarpine seizure model could serve as a valuable tool for studying mechanisms of Nova-regulated alternative splicing in rat striatum.

Sinapic acid attenuates kainic acid-induced hippocampal neuronal damage in mice

Excitotoxin induces neurodegeneration via glutamatergic activation or oxidative stress, which means that the blockade of glutamate receptors and the scavenging of free radicals are potential therapeutic targets in neurodegenerative diseases. Sinapic acid (SA) has a GABA(A) receptor agonistic property and free radical scavenging activity. We investigated the neuroprotective effects of SA on kainic acid (KA)-induced hippocampal brain damage in mice. SA (10 mg/kg) by oral administration has an anticonvulsant effect on KA-induced seizure-like behavior. Moreover, SA (10 mg/kg) significantly attenuated KA-induced neuronal cell death in the CA1 and CA3 hippocampal regions when administered as late as 6 h after KA. In addition, flumazenil, a GABA(A) antagonist, blocked the effect of SA administered immediately after KA but not the effect of SA administered 6 h after KA. This late protective effect of SA was accompanied by reduced levels of reactive gliosis, inducible nitric oxide synthase expression, and nitrotyrosine formation in the hippocampus. In the passive avoidance task, KA-induced memory impairments were ameliorated by SA. These results suggest that the potential therapeutic effect of SA is due to its attenuation of KA-induced neuronal damage in the brain via its anti-convulsive activity through GABA(A) receptor activation and radical scavenging activity.

Matrix metalloproteinase-9 activity increased by two different types of epileptic seizures that do not induce neuronal death: a possible role in homeostatic synaptic plasticity

Matrix metalloproteases (MMPs) degrade or modify extracellular matrix or membrane-bound proteins in the brain. MMP-2 and MMP-9 are activated by treatments that result in a sustained neuronal depolarization and are thought to contribute to neuronal death and structural remodeling. At the synapse, MMP actions on extracellular proteins contribute to changes in synaptic efficacy during learning paradigms. They are also activated during epileptic seizures, and MMP-9 has been associated with the establishment of aberrant synaptic connections after neuronal death induced by kainate treatment. It remains unclear whether MMPs are activated by epileptic activities that do not induce cell death. Here we examine this point in two animal models of epilepsy that do not involve extensive cell damage. We detected an elevation of MMP-9 enzymatic activity in cortical regions of secondary generalization after focal seizures induced by 4-aminopyridine (4-AP) application in rats. Pro-MMP-9 levels were also higher in Wistar Glaxo Rijswijk (WAG/Rij) rats, a genetic model of generalized absence epilepsy, than they were in Sprague-Dawley rats, and this elevation was correlated with diurnally occurring spike-wave-discharges in WAG/Rij rats. The increased enzymatic activity of MMP-9 in these two different epilepsy models is associated with synchronized neuronal activity that does not induce widespread cell death. In these epilepsy models MMP-9 induction may therefore be associated with functions such as homeostatic synaptic plasticity rather than neuronal death.

Coactivation of GABA receptors inhibits the JNK3 apoptotic pathway via disassembly of GluR6-PSD-95-MLK3 signaling module in KA-induced seizure

PURPOSE

Past work has demonstrated that kainic acid (KA)-induced seizures could cause the enhancement of excitation and lead to neuronal death in rat hippocampus. To counteract such an imbalance between excitation and inhibition, we designed experiments by activating the inhibitory gamma-aminobutyric acid (GABA) receptor to investigate whether such activation suppresses the excitatory glutamate signaling induced by KA and to elucidate the underlying molecular mechanisms.

METHODS

Muscimol coapplied with baclofen was intraperitoneally administrated to the rats 40 min before KA injection by intracerebroventricular infusion. Subsequently we used a series of methods including immunoprecipitation, immunoblotting, histologic analysis, and immunohistochemistry to analyze the interaction, expression, and phosphorylation of relevant proteins as well as the survival of the CA1/CA3 pyramidal neurons.

RESULTS

Coadministration of muscimol and baclofen exerted neuroprotection against neuron death induced by KA; inhibited the increased assembly of the GluR6-PSD-95-MLK3 module induced by KA; and suppressed the activation of MLK3, MKK7, and JNK3.

DISCUSSION

Taken together, we demonstrate that coactivation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module induced by KA. This provides a new insight into the therapeutic approach to epileptic seizure.

Meta-analysis of kindling-induced gene expression changes in the rat hippocampus

Numerous studies have been performed to examine gene expression patterns in the rodent hippocampus in the kindling model of epilepsy. However, recent reviews of this literature have revealed limited agreement among studies. Because this conclusion was based on retrospective comparison of reported “hit lists” from individual studies, we hypothesized that re-analysis of the original expression data would help address this concern. In this paper, we reanalyzed four genome-wide expression studies of excitotoxin-induced kindling in rat and performed a statistical meta-analysis. The meta-analysis revealed over 800 genes which show significant change in expression 24 h after initial seizure induction, and 59 genes altered after 10 days. To evaluate our results in light of previous work, we assembled a reference list of genes formed from a consensus of the published literature. Our profiles include most of the genes in this reference list, and most of the additional genes are from pathways or biological processes previously recognized to be altered in kindling. In addition our results emphasized expression changes in lipid metabolism and protein degradation pathways. We conclude that a cautious re-analysis of published expression data can help illuminate genes and pathways underling kindling. Supplementary Material is available at http://www.chibi.ubc.ca/faculty/pavlidis/meta-analysis-of-brain-kindling/

Krüppel-like factor 9 is necessary for late-phase neuronal maturation in the developing dentate gyrus and during adult hippocampal neurogenesis

The dentate gyrus (DG) is modified throughout life by integration of new adult-born neurons. Similarities in neuronal maturation during DG development and adult hippocampal neurogenesis suggest that genetically encoded intrinsic regulatory mechanisms underlying these temporally distinct processes are conserved and reused. Here, we identify a novel transcriptional regulator of dentate granule neuron maturation, Krüppel-like factor 9 (Klf-9). We show that Klf-9 expression is induced by neuronal activity and as dentate granule neurons functionally integrate in the developing and adult DG. During development, dentate granule neurons lacking Klf-9 show delayed maturation as reflected by altered expression of early-phase markers, dendritic spine formation, and electrophysiological properties. Adult Klf-9-null mice exhibit normal stem cell proliferation and cell fate specification in the DG but show impaired differentiation of adult-born neurons and decreased neurogenesis-dependent synaptic plasticity. Behavioral analysis of Klf-9-null mice revealed a subtle increase in anxiety-like behavior and an impairment in contextual fear discrimination learning. Thus, Klf-9 is necessary for late-phase maturation of dentate granule neurons both in DG development and during adult hippocampal neurogenesis. Klf-9-dependent neuronal maturation may therefore represent a candidate regulatory mechanism underlying these temporally distinct processes.

JunB is a repressor of MMP-9 transcription in depolarized rat brain neurons

Matrix Metalloproteinase-9 (MMP-9) is an extracellularly operating enzyme involved in the synaptic plasticity, hippocampal-dependent long term memory and neurodegeneration. Previous studies have shown its upregulation following seizure-evoking stimuli. Herein, we show that in the rat brain, MMP-9 mRNA expression in response to pentylenetetrazole-evoked neuronal depolarization is transient. Furthermore, we demonstrate that in the rat hippocampus neuronal activation strongly induces JunB expression, simultaneously leading to an accumulation of JunB/FosB complexes onto the -88/-80 bp site of the rat MMP-9 gene promoter in vivo. Surprisingly, manipulations with JunB expression levels in activated neurons revealed its moderate repressive action onto MMP-9 gene expression. Therefore, our study documents the active repressive influence of AP-1 onto MMP-9 transcriptional regulation by the engagement of JunB.

Increased expression of the lysosomal protease cathepsin S in hippocampal microglia following kainate-induced seizures

To examine lesions caused by seizures in the developing brain, seizures were induced by the intraperitoneal injection of kainate and nicotine into juvenile mice. After a week, whole brain sections were examined using histochemistry and the gene expression profiles in the neocortices and hippocampi were analyzed using a DNA microarray. Propidium iodide and Fluoro-Jade C staining revealed that kainate but not nicotine-induced degeneration of the hippocampal pyramidal neurons. Comparative analyses of 12,488 probe sets on the microarray chip revealed the differential expression of 208 and 1243 probe sets in the neocortices and hippocampi of kainate-injected mice, respectively, as well as that of 535 and 436 probe sets in the neocortices and hippocampi of nicotine-injected mice, respectively, the patterns of change were largely drug-specific and region-specific. Among a variety of kainate-modified genes including those representing neurodegeneration and astrogliosis, we identified an increased gene expression of the lysosomal cysteine protease cathepsin S in the hippocampi of kainate-injected mice. Western blot analysis of the hippocampal homogenates revealed that kainate induced a 3.3-fold increase in cathepsin S expression. Immunohistochemistry using cell type-specific markers showed that cathepsin S was induced in microglia, especially those surrounding degenerating pyramidal neurons, but not in neurons themselves or astroglia, in the hippocampal CA1 region of kainate-injected mice. These results indicate that seizures induced by kainate elicit neurodegeneration, astrogliosis, and microglial activation accompanied by the expression of cathepsin S while those induced by nicotine do not.

Synaptic localization of seizure-induced matrix metalloproteinase-9 mRNA

The phenomenon of dendritic transport and local translation of mRNA is considered to be one of the most fundamental mechanisms underlying long-term synaptic plasticity. Matrix metalloproteinase 9 (gelatinase B) (MMP-9) is a matrix metalloproteinase implicated in synaptic long-term potentiation and hippocampus-dependent memory. It was recently shown to be prominently up-regulated in the hippocampal dentate gyrus (DG) upon kainate-mediated seizures. Here, using a high resolution nonradioactive in situ hybridization at the light- and electron-microscopic levels, as well as subcellular fractionation, we provide evidence that in the rat hippocampus, MMP-9 mRNA is associated with dendrites and dendritic spines bearing asymmetric (excitatory) synapses. Moreover we observe that after kainate treatment the number of dendrites and synapses containing MMP-9 mRNA increases markedly. Our results indicate that we are observing the phenomenon of dendritic transport of seizure-induced MMP-9 mRNA.

Epileptogenesis in experimental models

Epileptogenesis refers to a phenomenon in which the brain undergoes molecular and cellular alterations after a brain-damaging insult, which increase its excitability and eventually lead to the occurrence of recurrent spontaneous seizures. Common epileptogenic factors include traumatic brain injury (TBI), stroke, and cerebral infections. Only a subpopulation of patients with any of these brain insults, however, will develop epilepsy. Thus, there are two great challenges: (1) identifying patients at risk, and (2) preventing and/or modifying the epileptogenic process. Target identification for antiepileptogenic treatments is difficult in humans because patients undergoing epileptogenesis cannot currently be identified. Animal models of epileptogenesis are therefore necessary for scientific progress. Recent advances in the development of experimental models of epileptogenesis have provided tools to investigate the molecular and cellular alterations and their temporal appearance, as well as the epilepsy phenotype after various clinically relevant epileptogenic etiologies, including TBI and stroke. Studying these models will lead to answers to critical questions such as: Do the molecular mechanisms of epileptogenesis depend on the etiology? Is the spectrum of network alterations during epileptogenesis the same after various clinically relevant etiologies? Is the temporal progression of epileptogenesis similar? Work is ongoing, and answers to these questions will facilitate the identification of molecular targets for antiepileptogenic treatments, the design of treatment paradigms, and the determination of whether data from one etiology can be extrapolated to another.

β-Dystroglycan as a Target for MMP-9, in Response to Enhanced Neuronal Activity

Matrix metalloproteinase-9 has recently emerged as an important molecule in control of extracellular proteolysis in the synaptic plasticity. However, no synaptic targets for its enzymatic activity had been identified before. In this report, we show that beta-dystroglycan comprises such a neuronal activity-driven target for matrix metalloproteinase-9. This notion is based on the following observations. (i) Recombinant, autoactivating matrix metalloproteinase-9 produces limited proteolytic cleavage of beta-dystroglycan. (ii) In neuronal cultures, beta-dystroglycan proteolysis occurs in response to stimulation with either glutamate or bicuculline and is blocked by tissue inhibitor of metalloproteinases-1, a metalloproteinase inhibitor. (iii) Beta-dystroglycan degradation is also observed in the hippocampus in vivo in response to seizures but not in the matrix metalloproteinase-9 knock-out mice. (iv) Beta-dystroglycan cleavage correlates in time with increased matrix metalloproteinase-9 activity. (v) Finally, beta-dystroglycan and matrix metalloproteinase-9 colocalize in postsynaptic elements in the hippocampus. In conclusion, our data identify the beta-dystroglycan as a first matrix metalloproteinase-9 substrate digested in response to enhanced synaptic activity. This demonstration may help to understand the possible role of both proteins in neuronal functions, especially in synaptic plasticity, learning, and memory.

Upregulation of synaptotagmin IV protein in kainate-induced seizures

Synaptotagmin IV is a product of immediate early-response gene. It is involved in the regulated neurosecretion in the brain. Its putative role, however, in vesicular transport and localization in secretor y vesicles is still a matter of debate. Here we followed the spatiotemporal pattern of synaptotagmin IV protein upregulation in the hippocampus, caudate putamen, nucleus accumbens, nucleus amygdalae, piriform and entorhinal cortices of rats with kainate-induced seizures. We found that upregulation pattern paralleled the direction of depolarization through the hippocampus and also reflecting seizure activity spreading to other brain regions. We speculate that synaptotagmin IV may have a role in the vesicular transport of the upregulated peptides and proteins involved in the plasticity and/or neurodegeneration provoked by the kainate.