Effect of status epilepticus on expression of brain UDP-glucuronosyltransferase 1a in rats

Status epilepticus (SE) involves severe epileptic seizures that cause oxidative stress in the brain. Oxidative stress is known to influence uridine 5'-diposphate-glucuronosyltransferase (UGT) 1A expression. The present study aimed at elucidating the effect of SE on Ugt1a1, Ugt1a6 and Ugt1a7 expression in the rat brain. Kainic acid was used to create an animal model of SE. Sprague-Dawley rats were treated intraperitoneally with 10 mg/kg kainic acid. Ugt1a1 and Ugt1a7 mRNA levels were increased by SE in the cortex and hippocampus (Ugt1a1: 4.0- and 5.3-fold, respectively; Ugt1a7: 2.8- and 2.5-fold, respectively). Moreover, the induction degree of heme oxygenase-1 mRNA, an oxidative stress marker, was high in these regions, suggesting that oxidative stress could be involved in Ugt1a1 and Ugt1a7 induction. Ugt1a6 was elevated by 1.8-fold in the cortex in both SE and non-response (non-epileptic seizure response) rats, implying that Ugt1a6 induction may be independent from SE. An intraperitoneal single administration of 25 mg/kg diazepam (DZP) for the treatment of SE could attenuate heme oxygenase-1 induction in the cortex, whereas Ugt1a1 was decreased in the hippocampus, but not in the cortex, suggesting that there likely exists an alternative mechanism for Ugt1a1 reduction by DZP treatment. Continuous 14-day administration of DZP inhibited Ugt1a1 induction in the cortex, but did not have an effect on Ugt1a7 induction. This study indicated that SE altered the expression of brain Ugt1a1 and Ugt1a7, which could alter glucuronidation in the brain.

Status Epilepticus Decreases Brain Cytochrome P450 2D4 Expression in Rats

Status epilepticus (SE) is a life-threatening neurological emergency characterized by frequent seizures. The present study aims at elucidating the effect of SE on CYP2D4 expression in the rat brain. To create a rat model of SE, Sprague-Dawley rats were intraperitoneally administered 10 mg/kg kainic acid. The CYP2D4 mRNA levels in the cortex and hippocampus of the SE rats were decreased by 0.38- and 0.39-fold, respectively. The protein level of octamer transcription factor 1 (Oct-1), which is involved in the transcriptional activation of CYP2D4 by binding to the CYP2D4 regulatory element, was also attenuated by 0.64- and 0.51-fold in these regions of the SE rat, suggesting that a reduction in Oct-1 may be involved in the CYP2D4 suppression. Yin yang 1 can function as a cofactor of histone deacetylase 1 and inhibit the binding of Oct-1 to the CYP2D4 regulatory element. The coimmunoprecipitation assay revealed that the interaction between yin yang 1 and histone deacetylase 1 in the cortex and hippocampus was enhanced during SE, indicating that this interaction is also responsible for the CYP2D4 suppression. This study clarified that SE led to a decrease in the expression of CYP2D4, thus altering the pharmacokinetics and efficacy of the drugs in the brain.

Sevoflurane activates hippocampal CA3 kainate receptors (Gluk2) to induce hyperactivity during induction and recovery in a mouse model

BACKGROUND

In addition to general anaesthetic effects, sevoflurane can also induce hyperactive behaviours during induction and recovery, which may contribute to neurotoxicity; however, the mechanism of such effects is unclear. Volatile anaesthetics including isoflurane have been found to activate the kainate (GluK2) receptor. We developed a novel mouse model and further explored the involvement of kainate (GluK2) receptors in sevoflurane-induced hyperactivity.

METHODS

Maximal speed, mean speed, total movement distance and resting percentage of C57BL/6 mice were quantitatively measured using behavioural tracking software before and after sevoflurane anaesthesia. Age dependence of this model was also analysed and sevoflurane-induced hyperactivity was evaluated after intracerebral injection of the GluK2 receptor blocker NS-102. Neurones from the hippocampal CA3 region were used to undertake in vitro electrophysiological measurement of kainate currents and miniature excitatory postsynaptic potential (mEPSP).

RESULTS

Sevoflurane induced significant hyperactivities in mice under sevoflurane 1% anaesthesia and during the recovery period, characterized as increased movement speed and total distance. The hyperactivity was significantly increased in young mice compared with adults (P<0.01) and pre-injection of NS-102 significantly prevented this sevoflurane-induced hyperactivity. In electrophysiological experiments, sevoflurane significantly increased the frequency of mEPSP at low concentrations and evoked kainate currents at high concentrations.

CONCLUSIONS

We developed a behavioural model in mice that enabled characterization of sevoflurane-induced hyperactivity. The kainate (GluK2) receptor antagonist attenuated these sevoflurane-induced hyperactivities in vivo, suggesting that kainate receptors might be the underlying therapeutic targets for sevoflurane-induced hyperactivities in general anaesthesia.

Silencing phosphodiesterase 7B gene by lentiviral-shRNA interference attenuates neurodegeneration and motor deficits in hemiparkinsonian mice

Different studies have suggested that the nucleotide cyclic adenosine 3', 5'-monophosphate can actively play an important role as a neuroprotective and anti-inflammatory agent after a brain injury. The phosphodiesterase 7 (PDE7) enzyme is one of the enzymes responsible for controlling specifically the intracellular levels of cyclic adenosine 3', 5'-monophosphate in the immune and central nervous systems. Therefore, this enzyme could play an important role in brain inflammation and neurodegeneration. In this regard, using different chemical inhibitors of PDE7 we have demonstrated their neuroprotective and anti-inflammatory activity in different models of neurodegenerative disorders, including Parkinson's disease (PD). In the present study, we have used the toxin 6-hydroxydopamine and lipopolysaccharide to model PD and explore the protective effects of PDE7B deficiency in dopaminergic neurons cell death. Lentivirus-mediated PDE7B deprivation conferred marked in vitro and in vivo neuroprotection against 6-hydroxydopamine and lipopolysaccharide toxicity in dopaminergic neurons and preserved motor function involving the dopamine system in mouse. Our results substantiate previous data and provide a validation of PDE7B enzyme as a valuable new target for therapeutic development in the treatment of PD.

Treatment of status epilepticus with ketamine, are we there yet?

Status epilepticus (SE), a neurological emergency both in adults and in children, could lead to brain damage and even death if untreated. Generalized convulsive SE (GCSE) is the most common and severe form, an example of which is that induced by organophosphorus nerve agents. First- and second-line pharmacotherapies are relatively consensual, but if seizures are still not controlled, there is currently no definitive data to guide the optimal choice of therapy. The medical community seems largely reluctant to use ketamine, a noncompetitive antagonist of the N-methyl-d-aspartate glutamate receptor. However, a review of the literature clearly shows that ketamine possesses, in preclinical studies, antiepileptic properties and provides neuroprotection. Clinical evidences are scarcer and more difficult to analyze, owing to a use in situations of polytherapy. In absence of existing or planned randomized clinical trials, the medical community should make up its mind from well-conducted preclinical studies performed on appropriate models. Although potentially active, ketamine has no real place for the treatment of isolated seizures, better accepted drugs being used. Its best usage should be during GCSE, but not waiting for SE to become totally refractory. Concerns about possible developmental neurotoxicity might limit its pediatric use for refractory SE.

The protective effect of myo-inositol on hippocamal cell loss and structural alterations in neurons and synapses triggered by kainic acid-induced status epilepticus

It is known that myo-inositol pretreatment attenuates the seizure severity and several biochemical changes provoked by experimentally induced status epilepticus. However, it remains unidentified whether such properties of myo-inositol influence the structure of epileptic brain. In the present light and electron microscopic research we elucidate if pretreatment with myo-inositol has positive effect on hippocampal cell loss, and cell and synapses damage provoked by kainic acid-induced status epilepticus. Adult male Wistar rats were treated with (i) saline, (ii) saline + kainic acid, (iii) myo-inositol + kainic acid. Assessment of cell loss at 2, 14, and 30 days after treatment demonstrate cytoprotective effect of myo-inositol in CA1 and CA3 areas. It was strongly expressed in pyramidal layer of CA1, radial and oriental layers of CA3 and in less degree-in other layers of both fields. Ultrastructural alterations were described in CA1, 14 days after treatment. The structure of neurons, synapses, and porosomes are well preserved in the rats pretreated with myo-inositol in comparing with rats treated with only kainic acid.

Kainic Acid-induced neurotoxicity: targeting glial responses and glia-derived cytokines

Glutamate excitotoxicity contributes to a variety of disorders in the central nervous system, which is triggered primarily by excessive Ca²⁺ influx arising from overstimulation of glutamate receptors, followed by disintegration of the endoplasmic reticulum (ER) membrane and ER stress, the generation and detoxification of reactive oxygen species as well as mitochondrial dysfunction, leading to neuronal apoptosis and necrosis. Kainic acid (KA), a potent agonist to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate class of glutamate receptors, is 30-fold more potent in neuro-toxicity than glutamate. In rodents, KA injection resulted in recurrent seizures, behavioral changes and subsequent degeneration of selective populations of neurons in the brain, which has been widely used as a model to study the mechanisms of neurodegenerative pathways induced by excitatory neurotransmitter. Microglial activation and astrocytes proliferation are the other characteristics of KA-induced neurodegeneration. The cytokines and other inflammatory molecules secreted by activated glia cells can modify the outcome of disease progression. Thus, anti-oxidant and anti-inflammatory treatment could attenuate or prevent KA-induced neurodegeneration. In this review, we summarized updated experimental data with regard to the KA-induced neurotoxicity in the brain and emphasized glial responses and glia-oriented cytokines, tumor necrosis factor-α, interleukin (IL)-1, IL-12 and IL-18.

Anticonvulsant and depressant effects of aqueous extracts of Carum copticum seeds in male rats

In this study, the effects of aqueous extracts of Carum copticum seeds (CCS) were evaluated in kindling models of epilepsy. Additionally, the sedative and anxiolytic effects of the extract were assessed. For pentylenetetrazole (PTZ) kindling, rats received a subconvulsant dose of PTZ (40 mg/kg, ip) every second day and seizure stages were recorded. CCS aqueous extract (200, 400, or 600 mg/kg, ip) was injected 30 minutes prior to each PTZ injection. In electrical kindling, bipolar stimulating and monopolar recording electrodes were implanted stereotaxically in the right basolateral amygdala of male Sprague-Dawley rats. After kindling, the effect of aqueous extracts of CCS (200, 400, or 600 mg/kg, ip) on afterdischarge duration, duration of rearing, forelimb clonus, and loss of equilibrium (stage 5 seizure), and latency to the onset of bilateral forelimb clonus were measured. The sedative and the anxiolytic effects of CCS extracts were evaluated in an open-field apparatus and elevated plus maze, respectively. The results indicate that aqueous extracts of CCS have a significant anticonvulsant effect. Different doses of extract significantly delayed the incidence of every seizure stage in the PTZ model of kindling. Moreover, CCS extract (400 and 600 mg/kg, ip) suppressed afterdischarge duration, latency to the onset of bilateral forelimb clonus, and stage 5 seizure in the electrical kindling model. These results suggest that CCS extract has remarkable antiepileptic and central depressant effects.

Phosphodiesterase 7 inhibition preserves dopaminergic neurons in cellular and rodent models of Parkinson disease

Background

Phosphodiesterase 7 plays a major role in down-regulation of protein kinase A activity by hydrolyzing cAMP in many cell types. This cyclic nucleotide plays a key role in signal transduction in a wide variety of cellular responses. In the brain, cAMP has been implicated in learning, memory processes and other brain functions.

Methodology/Principal Findings

Here we show a novel function of phosphodiesterase 7 inhibition on nigrostriatal dopaminergic neuronal death. We found that S14, a heterocyclic small molecule inhibitor of phosphodiesterase 7, conferred significant neuronal protection against different insults both in the human dopaminergic cell line SH-SY5Y and in primary rat mesencephalic cultures. S14 treatment also reduced microglial activation, protected dopaminergic neurons and improved motor function in the lipopolysaccharide rat model of Parkinson disease. Finally, S14 neuroprotective effects were reversed by blocking the cAMP signaling pathways that operate through cAMP-dependent protein kinase A.

Conclusions/Significance

Our findings demonstrate that phosphodiesterase 7 inhibition can protect dopaminergic neurons against different insults, and they provide support for the therapeutic potential of phosphodiesterase 7 inhibitors in the treatment of neurodegenerative disorders, particularly Parkinson disease.

Voltage-dependent calcium channel and NMDA receptor antagonists augment anticonvulsant effects of lithium chloride on pentylenetetrazole-induced clonic seizures in mice

Although lithium is still a mainstay in the treatment of bipolar disorder, its underlying mechanisms of action have not been completely elucidated. Several studies have shown that lithium can also modulate seizure susceptibility in a variety of models. In the present study, using a model of clonic seizures induced with pentylenetetrazole (PTZ) in male Swiss mice, we investigated whether there is any interaction between lithium and either calcium channel blockers (CCBs: nifedipine, verapamil, and diltiazem) or N-methyl-D-aspartate (NMDA) receptor antagonists (ketamine and MK-801) in modulating seizure threshold. Acute lithium administration (5-100mg/kg, ip) significantly (P<0.01) increased seizure threshold. CCBs and NMDA receptor antagonists also exerted dose-dependent anticonvulsant effects on PTZ-induced seizures. Noneffective doses of CCBs (5mg/kg, ip), when combined with a noneffective dose of lithium (5mg/kg, ip), exerted significant anticonvulsant effects. Moreover, co-administration of a noneffective dose of either MK-801 (0.05mg/kg, ip) or ketamine (5mg/kg, ip) with a noneffective dose of lithium (5mg/kg, ip) significantly increased seizure threshold. Our findings demonstrate that lithium increases the clonic seizure threshold induced by PTZ in mice and interacts with either CCBs or NMDA receptor antagonists in exerting this effect, suggesting a role for Ca(2+) signaling in the anticonvulsant effects of lithium in the PTZ model of clonic seizures in mice.