Levetiracetam inhibits kindling-induced synaptic potentiation in the dentate gyrus of freely moving rats

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

Levetiracetam promoted rat embryonic neurogenesis via NMDA receptor-mediated mechanism in vitro

AIMS

Levetiracetam (LEV) is a broad-spectrum antiepileptic drug with neuroprotective properties and novel mechanisms of action. Some evidence suggests that LEV may impact adult neurogenesis, but the results are controversial. The present study was aimed to evaluate the effects of LEV on the proliferation and differentiation of rat embryonic neural stem cells (NSCs) and to explore the role of GABAB or NMDA receptors.

MAIN METHODS

NSCs were isolated from rat fetal ganglionic eminence at embryonic day 14.5. The effects of LEV on viability, proliferation, neurosphere formation, and neuronal or astroglial differentiation of NSCs were assessed using resazurin, BrdU incorporation, immunocytochemistry, quantitative real-time PCR, and western blotting. Additionally, we addressed the relationship between treatment with NMDA and GABAB receptor antagonists (MK801 and saclofen, respectively) in combination with LEV on these parameters.

KEY FINDINGS

The data showed that LEV (50 μM) significantly increased the number (p < 0.01) and diameter of neurospheres (p < 0.05), enhanced proliferation (p < 0.01), and promoted neuronal differentiation, as revealed by significantly increased expressions of DCX and NeuN. The expressions of astroglial markers, GFAP and Olig2, were markedly reduced. The addition of MK801 (10 μM) significantly diminished neurospheres growth (p < 0.001), decreased the number of proliferating cells (p < 0.01), and reduced the number of new neurons (p < 0.001) but increased the astroglial cells (p < 0.001) induced by LEV. Co-treatment with saclofen (25 μM) did not significantly affect LEV-induced NSCs proliferation and differentiation.

SIGNIFICANCE

Our findings suggest that LEV may enhance rat embryonic neurogenesis mainly through an NMDA receptor-mediated mechanism.

Chronic treatment with levetiracetam reverses deficits in hippocampal LTP in vivo in experimental temporal lobe epilepsy rats

Temporal lobe epilepsy (TLE), the common form of epilepsy in adults, often displays complex partial seizures and cognitive deficits. The underlying mechanisms of such deficits are not yet well understood. Many contributing factors, such as initial epileptogenic lesion, seizure type, age of onset, and treatment side effects have been proposed. Levetiracetam (LEV) is a novel anti-epileptic drug (AED) used to treat partial seizures and idiopathic generalized epilepsy. It has been suggested that LEV exerts antiepileptic properties by modulation of synaptic release of neurotransmitters. However, its neuroprotective effects on learning and memory are not yet well demonstrated. Here we showed the impairment of spatial memory in the pilocarpine-induced experimental TLE rats, which can be improved by LEV. Furthermore, we found chronic LEV treatment partially reversed the SE-induced synaptic dysfunction in hippocampal LTP induction in vivo. In addition, LEV treatment can alleviate the SE-induced abnormal GluR1 phosphorylation at Ser(831) site, which may contribute to the rescue of synaptic transmission. These results indicate the neuroprotective role for LEV while it exhibits an antiseizure effect on experimental epileptic models.

Prospects of levetiracetam as a neuroprotective drug against status epilepticus, traumatic brain injury, and stroke

Levetiracetam (LEV) is an anti-epileptic drug commonly used for the treatment of partial onset and generalized seizures. In addition to its neuromodulatory and neuroinhibitory effects via its binding to the synaptic vesicle protein SV2A, multiple studies have suggested neuroprotective properties for LEV in both epileptic and non-epileptic conditions. The purpose of this review is to discuss the extent of LEV-mediated protection seen in different neurological conditions, the potential of LEV for easing epileptogenesis, and the possible mechanisms that underlie the protective properties of LEV. LEV has been found to be particularly beneficial for restraining seizures in animal models of spontaneous epilepsy, acute seizures, and status epilepticus (SE). However, its ability for easing epileptogenesis and cognitive dysfunction following SE remains controversial with some studies implying favorable outcomes and others reporting no beneficial effects. Efficacy of LEV as a neuroprotective drug against traumatic brain injury (TBI) has received much attention. While animal studies in TBI models have showed significant neuroprotection and improvements in motor and memory performance with LEV treatment, clinical studies suggest that LEV has similar efficacy as phenytoin in terms of its ability to prevent post-traumatic epilepsy. LEV treatment for TBI is also reported to have fewer adverse effects and monitoring considerations but electroencephalographic recordings suggest the presence of increased seizure tendency. Studies on stroke imply that LEV is a useful alternative to carbamazepine for preventing post-stroke seizures in terms of efficacy and safety. Thus, LEV treatment has promise for restraining SE-, TBI-, or stroke-induced chronic epilepsy. Nevertheless, additional studies are needed to ascertain the most apt dose, timing of intervention, and duration of treatment after the initial precipitating injury and the mechanisms underlying LEV-mediated beneficial effects.

The endocannabinoid 2-arachidonoylglycerol negatively regulates habituation by suppressing excitatory recurrent network activity and reducing long-term potentiation in the dentate gyrus

Endocannabinoids are known to mediate retrograde suppression of synaptic transmission, modulate synaptic plasticity, and influence learning and memory. The 2-arachidonoylglycerol (2-AG) produced by diacylglycerol lipase α (DGLα) is regarded as the major endocannabinoid that causes retrograde synaptic suppression. To determine how 2-AG signaling influences learning and memory, we subjected DGLα knock-out mice to two learning tasks. We tested the mice using habituation and odor-guided transverse patterning tasks that are known to involve the dentate gyrus and the CA1, respectively, of the hippocampus. We found that DGLα knock-out mice showed significantly faster habituation to an odor and a new environment than wild-type littermates with normal performance in the transverse patterning task. In freely moving animals, long-term potentiation (LTP) induced by theta burst stimulation was significantly larger at perforant path-granule cell synapses in the dentate gyrus of DGLα knock-out mice. Importantly, prior induction of synaptic potentiation at this synapse caused a significant retardation of habituation in DGLα knock-out but not in wild-type littermates. The excitability of granule cells became higher in DGLα knock-out mice after they generated action potentials. Since no differences were found in intrinsic membrane properties and responses to odor stimuli in granule cells, the elevated excitability is considered to result from enhanced activity of an excitatory recurrent network composed of granule cells and mossy cells. These results suggest that retrograde 2-AG signaling negatively regulates habituation by suppressing excitatory recurrent network activity and reducing LTP in the dentate gyrus.