Evaluation of neurotoxic and neuroprotective pathways affected by antiepileptic drugs in cultured hippocampal neurons

May anti-seizure medications alter brain structure in temporal lobe epilepsy? A prospective study

Mild mesial temporal lobe epilepsy (MTLE) patients may remain untreated for a considerable time after disease onset or achieve seizure control with a single anti-seizures medication (ASM). Thus, they represent an optimal population to investigate whether ASMs might have influence on brain structure. We consecutively enrolled 56 mild MTLE patients (22/56 untreated, 34/56 on-monotherapy) and 58 healthy controls, matched for age and gender. All subjects underwent 3T-brain MRI, using FreeSurfer for automated morphometry. Differences in gray matter were assessed using one-way Analysis of Covariance (ANCOVA), adjusting for age, disease duration and intracranial volume. No significant change was observed between treated and untreated patients. We observed a significant reduction in cortical thickness of left inferior parietal, inferior temporal, middle temporal gyri, and right inferior parietal gyrus, temporal pole in monotherapy patients compared to healthy controls, as well as an increase in left isthmus of cingulate gyrus in untreated MTLE subjects compared to controls. Surface and subcortical volumes analysis revealed no differences among groups. Our study demonstrated no substantial morphological abnormalities between untreated mild MTLE patients and those undergoing monotherapy. Although exploratory, these results may reassure about safety of commonly used drugs and their marginal role in influencing neuroimaging results. PLAIN LANGUAGE SUMMARY: This study investigated the following question: can medications against epileptic seizures have an effect on brain structure in mild mesial temporal lobe? Preliminary results from our analyses suggest not, as we did not find any difference in brain gray matter between untreated patients and those treated with a single anti-seizures medication. On the other hand, epilepsy patients presented cortical thinning compared to healthy controls in several regions of the temporal and parietal lobes, in line with previous studies investigating the disease.

1H-MRS reveals metabolic alterations in generalized tonic-clonic seizures before and after treatment

AIMS

To explore the possible metabolic alterations of bilateral dorsolateral prefrontal cortices (DLPFC) of generalized tonic-clonic seizures (GTCS) patients before and after antiepileptic drugs treatment as compared with healthy controls (HCs) using proton magnetic resonance spectroscopy (1H-MRS).

METHODS

We included 23 newly diagnosed and unmedicated GTCS patients and 23 sex- and age-matched HCs. Metabolites including N-acetyl aspartate (NAA), myo-inositol (Ins), choline (Cho), creatine (Cr), and glutamate + glutamine (Glu + Gln, Glx) concentrations were quantified by using LCModel software and then corrected for the partial volume effect of cerebrospinal fluid.

RESULTS

The results demonstrated that metabolite concentrations were not equal between the left and the right DLPFC. Compared with HC, NAA of the left DLPFC and Cr of the right DLPFC were significantly lower in pre-treatment patients. Self-controlled study revealed that the patients' NAA of the left DLPFC increased while their Cr of the right DLPFC decreased after treatment. Correlation analysis showed a negative correlation between the duration of medication and the pre- and post-treatment difference of Cr.

CONCLUSION

These findings may shed a light on the metabolic mechanism of GTCS and the neurobiochemical mechanisms of AEDs.

Protective Role of UCP2 in Oxidative Stress and Apoptosis during the Silent Phase of an Experimental Model of Epilepsy Induced by Pilocarpine

Neuroprotection is a desirable process in many neurological disorders, yet complex mechanisms involved in this field are not completely understood. The pilocarpine epilepsy model causes potent, seizure-induced excitotoxicity cell death and mitochondria impairment. The present study is aimed at investigating the role of UCP2, a ROS negative regulator, in the neuroprotection after cholinergic insult. Our data demonstrated that UCP2 expression was augmented in the rat hippocampus 3 days after status epilepticus (SE), reaching a peak on the fifth day, then returning to basal levels. Concomitantly, phospho-AKT expression levels were higher in the hippocampus during the early silent phase (5 days after SE). Additionally, it was demonstrated that the blockade of UCP2 by antisense oligonucleotides (ASO) in SE rats successfully diminished both UCP2 mRNA and protein contents. SE ASO rats presented increased mitochondrial proapoptotic factor expression, caspase-3 activity, inflammatory cytokine expression, and ROS formation. Moreover, ASO treatment diminished p-AKT expression and antioxidant enzyme activities after pilocarpine insult. In conclusion, the present results highlight the neuroprotective actions of UCP2, acting in the inhibition of apoptotic factors and oxidative stress, to increase neuron survival after SE onset.

Neurodevelopmental Effects of Antiepileptic Drugs

Increasing evidence suggests that exposure to certain antiepileptic drugs (AEDs) during critical periods of development may induce transient or long-lasting neurodevelopmental deficits across cognitive, motor and behavioral domains. The developing nervous system may endure prolonged chronic exposure to AEDs during pregnancy (in utero) or during childhood, which can lead to neurodevelopmental defects such as congenital neural tube defects, lower IQ, language deficits, autism and ADHD. To date, valproate is the most widely recognized AED to significantly negatively affect neurodevelopment, and demonstrates greater adverse effects than any other AEDs that have been assessed. Although some AEDs appear to have low risk (i.e., lamotrigine, levetiracetam), other AEDs have been implicated in a variety of studies detailed below, and many AEDs have not been adequately assessed. The purpose of this review article is to summarize our current understanding of the neurodevelopmental effects of AEDs.

Short-term use of antiepileptic drugs is neurotoxic to the immature brain

Previous studies have shown that the long-term use of antiepileptic drugs can cause nervous system damage. However, short-term antiepileptic drug treatment is frequently given to infants, especially neonates, to control seizure. Whether the short-term use of antiepileptic drugs is neurotoxic remains unclear. In the present study, immature rats, 3–21 days of age, were intraperitoneally injected with phenobarbital and/or topiramate for 3 consecutive days. Hematoxylin-eosin and immunohistochemical staining revealed that phenobarbital and topiramate, individually or in combination, were cytotoxic to hippocampal CA1 neurons and inhibited the expression of GluR1 and NR2B, excitatory glutamate receptor subunits. Furthermore, the combination of the two drugs caused greater damage than either drug alone. The results demonstrate that the short-term use of antiepileptic drugs damages neurons in the immature brain and that the combined use of antiepileptic drugs exacerbates damage. Our findings suggest that clinicians should consider the potential neurotoxic risk associated with the combined use of antiepileptic drugs in the treatment of seizure.