Administration of simvastatin after kainic acid-induced status epilepticus restrains chronic temporal lobe epilepsy

The potential of antiseizure drugs and agents that act on novel molecular targets as antiepileptogenic treatments

A major goal of contemporary epilepsy research is the identification of therapies to prevent the development of recurrent seizures in individuals at risk, including those with brain injuries, infections, or neoplasms; status epilepticus; cortical dysplasias; or genetic epilepsy susceptibility. In this review we consider the evidence largely from preclinical models for the antiepileptogenic activity of a diverse range of potential therapies, including some marketed antiseizure drugs, as well as agents that act by immune and inflammatory mechanisms; reduction of oxidative stress; activation of the mammalian target of rapamycin or peroxisome proliferator-activated receptors γ pathways; effects on factors related to thrombolysis, hematopoesis, and angiogenesis; inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reducatase; brain-derived neurotrophic factor signaling; and blockade of α2 adrenergic and cannabinoid receptors. Antiepileptogenesis refers to a therapy of which the beneficial action is to reduce seizure frequency or severity outlasting the treatment period. To date, clinical trials have failed to demonstrate that antiseizure drugs have such disease-modifying activity. However, studies in animal models with levetiracetam and ethosuximide are encouraging, and clinical trials with these agents are warranted. Other promising strategies are inhibition of interleukin 1β signaling by drugs such as VX-765; modulation of sphingosine 1-phosphate signaling by drugs such as fingolimod; activation of the mammalian target of rapamycin by drugs such as rapamycin; the hormone erythropoietin; and, paradoxically, drugs such as the α2 adrenergic receptor antagonist atipamezole and the CB1 cannabinoid antagonist SR141716A (rimonabant) with proexcitatory activity. These approaches could lead to a new paradigm in epilepsy drug therapy where treatment for a limited period prevents the occurrence of spontaneous seizures, thus avoiding lifelong commitment to symptomatic treatment.

Novel frontiers in epilepsy treatments: preventing epileptogenesis by targeting inflammation

Currently available epilepsy drugs only affect the symptoms (seizures), and there is a need for innovative treatments that target the underlying disease. Increasing evidence points to inflammation as a potentially important mechanism in epileptogenesis. In the last decade, a new generation of etiologically realistic syndrome-specific experimental models have been developed, which are expected to capture the epileptogenic mechanisms operating in corresponding patient populations, and to exhibit similar treatment responsiveness. Recently, an intervention known to have broad-ranging anti-inflammatory effects (selective brain cooling) has been found to prevent the development of spontaneously occurring seizures in an etiologically realistic rat model of post-traumatic epilepsy. Several drugs used clinically for other indications also have the potential for inhibiting inflammation, and should be investigated for antiepileptogenic activity in these models. If results of such studies are positive, these compounds could rapidly enter Phase III trials in patients at high risk of developing epilepsy.

Chronic intermittent hypoxia promotes expression of 3-mercaptopyruvate sulfurtransferase in adult rat medulla oblongata

The present experiments were carried out to investigate the expression of 3-mercaptopyruvate sulfurtransferase (3MST) in medulla oblongata of rats and effects of chronic intermittent hypoxia (CIH) on its expression. Sprague Dawley adult rats were randomly divided into two groups, including control (Con) group and CIH group. The endogenous production of hydrogen sulfide (H2S) in medulla oblongata tissue homogenates was measured using the methylene blue assay method, 3MST mRNA and protein expression were analyzed by RT-PCR and Western blotting, respectively, and the expression of 3MST in the neurons of respiratory-related nuclei in medulla oblongata of rats was investigated with immunohistochemical technique. CIH elevated the endogenous H2S production in rat medulla oblongata (P<0.01). The RT-PCR and Western blotting analyses showed that 3MST mRNA and protein were expressed in the medulla oblongata of rats and CIH promoted their expression (P<0.01). Immunohistochemical staining indicated that 3MST existed in the neurons of pre-Bötzinger complex (pre-BötC), hypoglossal nucleus (12N), ambiguous nucleus (Amb), facial nucleus (FN) and nucleus tractus solitarius (NTS) in the animals and the mean optical densities of 3MST-positive neurons in the pre-BötC, 12N and Amb, but not in FN and NTS, were significantly increased in CIH group (P<0.05). In conclusion, 3MST exists in the neurons of medullary respiratory nuclei and its expression can be up-regulated by CIH in adult rat, suggesting that 3MST-H2S pathway may be involved in regulation of respiration and protection on medullary respiratory centers from injury induced by CIH.

Thymoquinone attenuates astrogliosis, neurodegeneration, mossy fiber sprouting, and oxidative stress in a model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is a rather common and difficult-to-treat variant of epilepsy. Nearly one third of people with epilepsy do not respond effectively to currently available anticonvulsants. In this study, we evaluated the protective effect of thymoquinone (TQ), the main constituent of black seed with antioxidant and anti-inflammatory effects, in the intrahippocampal kainate model of TLE in rat. Following kainate injection, seizure activity was observed that was significantly diminished by TQ pretreatment at a dose of 10 mg/kg, p.o. Intrahippocampal kainate also increased malondialdehyde (MDA), nitrite, and nitrate levels and decreased activity of superoxide dismutase and TQ only significantly attenuated MDA. In addition, intrahippocampal kainate caused a significant reduction of neurons in CA1, CA3 and the hilar regions, and TQ significantly attenuated these changes. Timm histochemistry showed a marked mossy fiber sprouting (MFS) in the dentate gyrus of kainate-lesioned rats, and TQ significantly lowered MFS intensity. Meanwhile, a number of reactive astrocytes (astrogliosis) increased significantly in the kainate group, and TQ pretreatment significantly decreased it. These data suggest that TQ pretreatment could attenuate seizure activity and lipid peroxidation, lower hippocampal neuronal loss and MFS, and mitigate astrogliosis in kainate model of TLE.

Lovastatin corrects excess protein synthesis and prevents epileptogenesis in a mouse model of fragile X syndrome

Many neuropsychiatric symptoms of fragile X syndrome (FXS) are believed to be a consequence of altered regulation of protein synthesis at synapses. We discovered that lovastatin, a drug that is widely prescribed for the treatment of high cholesterol, can correct excess hippocampal protein synthesis in the mouse model of FXS and can prevent one of the robust functional consequences of increased protein synthesis in FXS, epileptogenesis. These data suggest that lovastatin is potentially disease modifying and could be a viable prophylactic treatment for epileptogenesis in FXS.

Protective action of tetramethylpyrazine on the medulla oblongata in rats with chronic hypoxia

Tetramethylpyrazine (TMP), one of the active ingredients of the Chinese herb Lingusticum Wallichii Frantchat (Chuan Xiong), plays an important role in neuroprotection. However, the protective effect of TMP on the medulla oblongata, the most important region of the brain for cardiovascular and respiratory control, during chronic hypoxia remains unclear. In this study, we examined the neuroprotective effect of TMP on the medulla oblongata after chronic hypoxic injury in rats. Male Sprague-Dawley rats were randomly divided into four groups: control group, TMP group, chronic hypoxia group, and chronic hypoxia+TMP group. Rats were exposed to hypoxia (10% (v/v) O₂) or normoxia for 6 h daily for 14 days. TMP (80 mg/kg) or vehicle (saline) was injected intraperitoneally 30 min before experimentation. Loss of neurons in the pre-Bötzinger complex, the nucleus ambiguus, the nucleus tractus solitarius, the hypoglossal nucleus and the facial nucleus were evaluated by Nissl staining. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured, and apoptosis was monitored using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. The level of Bcl-2 mRNA and Bax mRNA was quantitatively measured by RT-PCR analysis. TMP protected Nissl bodies of neurons from injury in all nuclei observed, and reduced the loss of neurons in the nucleus ambiguus, the nucleus tractus solitarius, and the hypoglossal nucleus in rats subjected to chronic hypoxia. TMP upregulated SOD activity and inhibited the increase in MDA content in the medulla oblongata of hypoxic rats. In addition, TMP decreased the rate of apoptosis index (the percentage of apoptotic cells against the total number of cells) in all medullary structures examined, excepting the nucleus ambiguus and inhibited the decrease in Bcl-2 mRNA levels in the medulla oblongata following hypoxia. Our findings indicate that TMP may protect the medullary structures that are involved in cardiovascular and respiratory control from injury induced by chronic hypoxia in rats via its anti-oxidant and anti-apoptotic effects.

Fingolimod (FTY720) inhibits neuroinflammation and attenuates spontaneous convulsions in lithium-pilocarpine induced status epilepticus in rat model

Accumulating evidence has shown that neuroinflammation plays a key role in epileptogenesis. However, the efficacy of anti-inflammatory agents for preventing epilepsy remains controversial. Fingolimod (FTY720), a sphingosine-1-phosphate (S1P) analog, has potent anti-inflammatory effects in multiple sclerosis (MS) patients and animal models. Here, we tested whether FTY720 could exert antiepileptogenic effects in an adult rat model of lithium-pilocarpine induced epilepsy. 24h after onset of status epilepticus (SE), the epileptic rats received saline or 1mg/kg FTY720 i.p. once daily for 14 consecutive days. Thereafter, spontaneous convulsions (SCs), mossy fiber sprouting (MFS), neuronal loss, activation of microglia and astrocytes, expressions of interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNFα) were evaluated in the SE rats. We found that FTY720 treatment reduced neuronal loss and decreased activation of microglia and astrocytes in hippocampus at four days post-SE. Simultaneously, abnormal expressions of IL-1β and TNFα in hippocampus were restrained by FTY720 treatment. In addition, neuroprotective effects of FTY720 were demonstrated by increasing neuronal nuclei (NeuN)-positive cells and decreasing Fluoro-Jade B (FJB)-positive cells in the hippocampus. During 21-34days post-SE, the incidence, duration, frequency and severity of SCs significantly decreased in FTY720 treated rats compared with saline treated rats. Aberrant MFS was also attenuated by FTY720 administration. These results suggest that FTY720 exerts anti-inflammatory and antiepileptogenic effects in lithium-pilocarpine model of epilepsy and it may provide a new therapeutic approach for prevention of epileptogenesis.

Lovastatin modulates glycogen synthase kinase-3β pathway and inhibits mossy fiber sprouting after pilocarpine-induced status epilepticus

This study was undertaken to assay the effect of lovastatin on the glycogen synthase kinase-3 beta (GSK-3β) and collapsin responsive mediator protein-2 (CRMP-2) signaling pathway and mossy fiber sprouting (MFS) in epileptic rats. MFS in the dentate gyrus (DG) is an important feature of temporal lobe epilepsy (TLE) and is highly related to the severity and the frequency of spontaneous recurrent seizures. However, the molecular mechanism of MFS is mostly unknown. GSK-3β and CRMP-2 are the genes responsible for axonal growth and neuronal polarity in the hippocampus, therefore this pathway is a potential target to investigate MFS. Pilocarpine-induced status epilepticus animal model was taken as our researching material. Western blot, histological and electrophysiological techniques were used as the studying tools. The results showed that the expression level of GSK-3β and CRMP-2 were elevated after seizure induction, and the administration of lovastatin reversed this effect and significantly reduced the extent of MFS in both DG and CA3 region in the hippocampus. The alteration of expression level of GSK-3β and CRMP-2 after seizure induction proposes that GSK-3β and CRMP-2 are crucial for MFS and epiletogenesis. The fact that lovastatin reversed the expression level of GSK-3β and CRMP-2 indicated that GSK-3β and CRMP-2 are possible to be a novel mechanism of lovatstain to suppress MFS and revealed a new therapeutic target and researching direction for studying the mechanism of MFS and epileptogenesis.