Neuroprotective effect of lithium after pilocarpine-induced status epilepticus in mice

Neuroprotective potential of topiramate, pregabalin and lacosamide combination in a rat model of acute SE and intractable epilepsy: Perspectives from electroencephalographic, neurobehavioral and regional degenerative analysis

The lithium-pilocarpine model is commonly used to recapitulate characteristics of human intractable focal epilepsy. In the current study, we explored the impact of topiramate (TPM) alone and in combination with pregabalin and lacosamide administration for 6 weeks on the evolution of spontaneous recurrent seizures (SRS) and disease-modifying potential on associated neuropsychiatric comorbidities. In addition, redox impairments and neurodegeneration in hippocampus regions vulnerable to temporal lobe epilepsy (TLE) were assessed by cresyl violet staining. Results revealed that acute electrophysiological (EEG) profiling of the ASD cocktail markedly halted sharp ictogenic spikes as well as altered dynamics of brain wave oscillations thus validating the need for polytherapy vs. monotherapy. In TLE animals, pharmacological intervention for 6 weeks with topiramate 10 mg/kg in combination with PREG and LAC at the dose of 20 mg/kg exhibited marked protection from SRS incidence, improved body weight, offensive aggression, anxiety-like behavior, cognitive impairments, and depressive-like behavior (p < 0.05). Moreover, combination therapy impeded redox impairments as evidenced by decreased MDA and AchE levels and increased activity of antioxidant SOD, GSH enzymes. Furthermore, polytherapy rescued animals from SE-induced neurodegeneration with increased neuronal density in CA1, CA3c, CA3ab, hilus, and granular cell layer (GCL) of the dentate gyrus. In conclusion, early polytherapy with topiramate in combination with pregabalin and lacosamide prompted synergy and prevented epileptogenesis with associated psychological and neuropathologic alterations.

Prion therapeutics: Lessons from the past

Prion diseases are a group of incurable zoonotic neurodegenerative diseases (NDDs) in humans and other animals caused by the prion proteins. The abnormal folding and aggregation of the soluble cellular prion proteins (PrPC) into scrapie isoform (PrPSc) in the Central nervous system (CNS) resulted in brain damage and other neurological symptoms. Different therapeutic approaches, including stalling PrPC to PrPSc conversion, increasing PrPSc removal, and PrPC stabilization, for which a spectrum of compounds, ranging from organic compounds to antibodies, have been explored. Additionally, a non-PrP targeted drug strategy using serpin inhibitors has been discussed. Despite numerous scaffolds being screened for anti-prion activity in vitro, only a few were effective in vivo and unfortunately, almost none of them proved effective in the clinical studies, most likely due to toxicity and lack of permeability. Recently, encouraging results from a prion-protein monoclonal antibody, PRN100, were presented in the first human trial on CJD patients, which gives a hope for better future for the discovery of other new molecules to treat prion diseases. In this comprehensive review, we have re-visited the history and discussed various classes of anti-prion agents, their structure, mode of action, and toxicity. Understanding pathogenesis would be vital for developing future treatments for prion diseases. Based on the outcomes of existing therapies, new anti-prion agents could be identified/synthesized/designed with reduced toxicity and increased bioavailability, which could probably be effective in treating prion diseases.

Photobiomodulation regulates adult neurogenesis in the hippocampus in a status epilepticus animal model

Status epilepticus (SE) refers to a single seizure that lasts longer than typical seizures or a series of consecutive seizures. The hippocampus, which is vulnerable to the effects of SE, has a critical role in memory storage and retrieval. The trisynaptic loop in the hippocampus connects the substructures thereof, namely the dentate gyrus (DG), CA3, and CA1. In an animal model of SE, abnormal neurogenesis in the DG and aberrant neural network formation result in sequential neural degeneration in CA3 and CA1. Photobiomodulation (PBM) therapy, previously known as low-level laser (light) therapy (LLLT), is a novel therapy for the treatment of various neurological disorders including SE. However, the effects of this novel therapeutic approach on the recovery process are poorly understood. In the present study, we found that PBM transformed SE-induced abnormal neurogenesis to normal neurogenesis. We demonstrated that PBM plays a key role in normal hippocampal neurogenesis by enhancing the migration of maturing granular cells (early neuronal cells) to the GCL, and that normal neurogenesis induced by PBM prevents SE-induced hippocampal neuronal loss in CA1. Thus, PBM is a novel approach to prevent seizure-induced neuronal degeneration, for which light devices may be developed in the future.

What is the Role of Lithium in Epilepsy?

Lithium is a well-known FDA-approved treatment for bipolar and mood disorders. Lithium has been an enigmatic drug with multifaceted actions involving various neurotransmitters and intricate cell signalling cascades. Recent studies highlight the neuroprotective and neurotrophic actions of lithium in amyotrophic lateral sclerosis, Alzheimer's disease, intracerebral hemorrhage, and epilepsy. Of note, lithium holds a significant interest in epilepsy, where the past reports expose its non-specific proconvulsant action, followed lately by numerous studies for anti-convulsant action. However, the exact mechanism of action of lithium for any of its effects is still largely unknown. The present review integrates findings from several reports and provides detailed possible mechanisms of how a single molecule exhibits marked pro-epileptogenic as well as anti-convulsant action. This review also provides clarity regarding the safety of lithium therapy in epileptic patients.

Sex-related Differences in Glial Fibrillary Acidic Protein-positive GABA Regulate Neuropathology Following Pilocarpine-induced Status Epilepticus

Status epilepticus (SE) is a life-threatening neurological disorder that causes neuronal death and glial activation. Studies have explained the clinical side effects and lack of effectiveness of neurological disorder treatments based on sex-related differences in brain structure and function. However, the sex-specific outcomes of seizure disorders and the underlying mechanisms remain unknown. We compared SE-induced behavioral and pathophysiological changes in male and female mice. The time taken to reach stage 6 seizure following pilocarpine injection was shorter in male mice than in female mice, and the prevalence of SE was higher in male mice than in female mice. Fluoro-Jade B staining revealed more extensive SE-induced hippocampal neuronal death in male mice than in female mice. Glial cells were more activated in male mice than in female mice. In contrast, astrocyte-derived γ-aminobutyric acid (GABA)-immunostaining was less expressed in male mice than in female mice. Moreover, the mRNA levels of inflammatory cytokines released from activated glial cells were higher in male mice than in female mice. Notably, the mRNA level of astrocytic γ-aminobutyric acid transporter (GAT-3) involved in extracellular GABA uptake was lower in female mice than in male mice, while the mRNA levels of glutamate/aspartate transporter (GLAST (EAAT1)) and glutamate transporter (GLT-1 (EAAT2)) involved in extracellular glutamate uptake were higher in female mice. Our findings suggest that male mice are more vulnerable to SE than female mice, resulting in more extensive neuronal cell death and glial activation in male mice, partly due to increased GAT-3 expression that subsequently leads to reduced glial fibrillary acidic protein (GFAP)-positive GABA content assessed with anti-GABA antibodies.

Lithium as a disease-modifying agent for prion diseases

Prion diseases still remain incurable despite multiple efforts to develop a treatment. Therefore, it is important to find strategies to at least reduce the symptoms. Lithium has been considered as a neuroprotective agent for years, and the objective of this preclinical study was to evaluate the efficacy of lithium delivered as a water-in-oil microemulsion (Aonys^®). This delivery system allows using low doses of lithium and to avoid the toxicity observed in chronic treatments. C57BL/6J mice were intracranially inoculated with ME7 prion-infected brain homogenates and then were treated with lithium from day 90 post inoculation until their death. Lithium was administered at traditional doses (16 mg/kg/day) by the gavage route and at lower doses (40 or 160 µg/kg/day; Aonys^®) by the rectal mucosa route. Low doses of lithium (Aonys^®) improved the survival of prion-inoculated mice, and also decreased vacuolization, astrogliosis, and neuronal loss compared with controls (vehicle alone). The extent of the protective effects in mice treated with low-dose lithium was comparable or even higher than what was observed in mice that received lithium at the traditional dose. These results indicate that lithium administered using this innovative delivery system could represent a potential therapeutic approach not only for prion diseases but also for other neurodegenerative diseases.

Inverted-U response of lacosamide on pilocarpine-induced status epilepticus and oxidative stress in C57BL/6 mice is independent of hippocampal collapsin response mediator protein-2

OBJECTIVE

Currently, lacosamide (LCM) is not approved for use in status epilepticus (SE) but several shreds of evidence are available to support its use. The present study was, therefore, undertaken to evaluate the effect of LCM on pilocarpine (PILO) induced SE and neurodegeneration in C57BL/6 mice and to ascertain the involvement of CRMP-2 in mediating above effect.

METHODS

Pilocarpine-induced SE model was developed to explore the effect of LCM 20, 40 and 80 mg/kg in mice. We assessed the seizure severity, seizure latency, spontaneous alternation behavior (SAB) and motor coordination by behavioral observation. Histopathological evaluation and measurement of the levels of CRMP-2, reduced glutathione (GSH) and malondialdehyde (MDA) were carried out in mice hippocampus.

RESULTS

LCM exhibited a biphasic effect i.e., protection against SE at 20 mg/kg and 40 mg/kg dose whilst aggravated seizure-like behavior and mortality at 80 mg/kg. Further, it increased percentage alternation (i.e., restored spatial memory) in SAB and elevated motor impairment with increasing dose. Histologically, LCM 20 mg/kg and 40 mg/kg (but not 80 mg/kg) reduced neurodegeneration. LCM 20 mg/kg and 40 mg/kg reversed the elevated MDA and GSH levels while 80 mg/kg showed a tendency to increase oxidative stress. In contrast, LCM (at all doses) reversed the pilocarpine-induced elevation of collapsin response mediator protein-2 (CRMP-2).

CONCLUSION

LCM protected against pilocarpine-induced SE, associated neurodegeneration and improved pilocarpine-associated impairment of spatial memory. The study reveals that CRMP-2 may not be mediating the inverted-U-response of LCM at least in pilocarpine model. Therefore, the anti-oxidant effect of LCM (and not its ability to modulate CRMP-2) was anticipated as the mechanism underlying neuroprotection.