Effects of phenytoin and lamotrigine treatment on serum BDNF levels in offsprings of epileptic rats

Relationship between plasma brain-derived neurotrophic factor levels and neurological disorders: An investigation using Mendelian randomisation

Background

Altered brain-derived neurotrophic factor (BDNF) concentrations have been detected in the central nervous system tissues and peripheral blood. These alterations are associated with a series of neurological disorders.

Objective

To investigate the potential causal relationships between genetically determined plasma BDNF levels and various neurological diseases using a two-sample Mendelian randomisation study.

Methods

We selected single nucleotide polymorphisms strongly related to plasma BDNF levels as instrumental variables. Within the Mendelian randomisation framework, we used summary-level statistics for exposure (plasma BDNF levels) and outcomes (neurological disorders).

Results

We observed suggestive evidence of a relation between higher plasma BDNF levels and less risk of nontraumatic intracranial haemorrhage (nITH) (odds ratio [OR] = 0.861, 95 % confidence interval [CI]: 0.774-0.958, P = 0.006, PFDR = 0.078), epilepsy (OR = 0.927, 95 % CI: 0.880-0.976, P = 0.004, PFDR = 0.078), focal epilepsy (OR = 0.928, 95 % CI: 0.874-0.986, P = 0.016, PFDR = 0.139), and non-lesional focal epilepsy (OR = 0.981, 95 % CI: 0.964-0.999, P = 0.041, PFDR = 0.267). Combined with the UK Biobank dataset, the association of plasma BDNF levels with nITH remained significant (OR = 0.88, 95 % CI: 0.81-0.96, P < 0.01). The combined analysis of three consortium datasets demonstrated a considerable impact of plasma BDNF on epilepsy (OR = 0.94, 95 % CI: 0.90-0.98, P < 0.01) and a suggestive impact on focal epilepsy (OR = 0.94, 95 % CI: 0.89-0.99, P = 0.02). However, there was no apparent correlation between plasma BDNF levels and other neurological disorders or related subtypes.

Conclusions

Our study supports a possible causal relationship between elevated plasma BDNF levels and a reduced risk of nITH, epilepsy, and focal epilepsy.

The Possible Role of Brain-derived Neurotrophic Factor in Epilepsy

Epilepsy is a neurological disease characterized by repeated seizures. Despite of that the brain-derived neurotrophic factor (BDNF) is implicated in the pathogenesis of epileptogenesis and epilepsy, BDNF may have a neuroprotective effect against epilepsy. Thus, the goal of the present review was to highlight the protective and detrimental roles of BDNF in epilepsy. In this review, we also try to find the relation of BDNF with other signaling pathways and cellular processes including autophagy, mTOR pathway, progranulin (PGN), and α-Synuclein (α-Syn) which negatively and positively regulate BDNF/tyrosine kinase receptor B (TrkB) signaling pathway. Therefore, the assessment of BDNF levels in epilepsy should be related to other neuronal signaling pathways and types of epilepsy in both preclinical and clinical studies. In conclusion, there is a strong controversy concerning the potential role of BDNF in epilepsy. Therefore, preclinical, molecular, and clinical studies are warranted in this regard.

Neuroprotective effects of glucagon-like peptide-1 (GLP-1) analogues in epilepsy and associated comorbidities

Epilepsy is a common neurological condition induced by losing equilibrium of different pathway as well as neurotransmitters that affects over 50 million people globally. Furthermore, long-term administration of anti-seizure medications has been associated with psychological adverse effects. Also, epilepsy has been related to an increased prevalence of obesity and called type 2 diabetes mellitus. On the other hand, GLP-1 receptors are located throughout the brain, including the hippocampus, which have been associated to majority of neurological conditions, such as epilepsy and psychiatric disorders. Moreover, the impact of different GLP-1 analogues on diverse neurotransmitter systems and associated cellular and molecular pathways as a potential therapeutic target for epilepsy and associated comorbidities has piqued curiosity. In this regard, the anticonvulsant effects of GLP-1 analogues have been investigated in various animal models and promising results such as anticonvulsants as well as cognitive improvements have been observed. For instance, GLP-1 analogues like liraglutide in addition to their possible anticonvulsant benefits, could be utilized to alleviate mental cognitive problems caused by both epilepsy and anti-seizure medication side effects. In this review and growing protective function of GLP-1 in epilepsy induced by disturbed neurotransmitter pathways and the probable mechanisms of action of GLP-1 analogues as well as the GLP-1 receptor in these effects have been discussed.

H19 silencing decreases kainic acid-induced hippocampus neuron injury via activating the PI3K/AKT pathway via the H19/miR-206 axis

Temporal lobe epilepsy (TLE) is the most common type of intractable epilepsy and is refractory to medications. However, the role and mechanism of H19 in regulating TLE remains largely undefined. Expression of H19 and miR-206 was detected using real-time quantitative PCR (RT-qPCR). Cell apoptosis, autophagy and inflammatory response were determined by flow cytometry, western blotting and enzyme-linked immunosorbent assay (ELISA). The interaction between H19 and miR-206 was predicted on the miRcode database and confirmed by luciferase reporter assay, RNA immunoprecipitation (RIP) and RNA pull-down. H19 was upregulated and miR-206 was downregulated in the rat hippocampus neurons after kainic acid (KA) treatment. Functionally, both H19 knockdown and miR-206 overexpression weakened KA-induced apoptosis, autophagy, inflammatory response, and oxidative stress in hippocampus neurons. Mechanically, the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway was activated by H19 knockdown and miR-206 was confirmed to be targeted and negatively regulated by H19. Moreover, downregulation of miR-206 could counteract the effects of H19 knockdown in KA-induced hippocampus neurons. Knockdown of H19 suppressed hippocampus neuronal apoptosis, autophagy and inflammatory response presumably through directly upregulating miR-206 and activating the PI3K/AKT signaling pathway.

Impact of maternal desvenlafaxine exposure on brain development in pregnant albino rats and their fetuses

Depression during pregnancy adversely affects fetal development. Desvenlafaxine drug is used for the treatment of gestational depression. In light of the well-established role of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in regulating neurogenesis and neural survival, the role of S100b in nerve cell energetic metabolism, differentiation of neurons and glial cells, an aberrant increase in NGF, BDNF and S100b expression in the fetal brain may contribute to desvenlafaxine cognitive disorders by altering brain development. This study is trying to determine the effect of desvenlafaxine on brain development. Thirty timed pregnant rats (from the 5th to the 20th day) were divided into three groups: control, low dose (5.14 mg/kg/day) and high dose (10.28 mg/kg/day) of desvenlafaxine where all animals received the corresponding doses by gavage. Maternal and fetal brain samples were fixed for histological, immunohistochemical (IHC) study of NGF and evaluated for BDNF and S100b genes expression. Desvenlafaxine induced some of the histopathological alterations in maternal and fetal rat brains. Moreover, IHC analysis of maternal and fetal rat brains showed that groups treated with desvenlafaxine demonstrated a significant increase of NGF protein immunoreactivity compared with that in the controls. Gene expression results revealed upregulation of messenger RNA BDNF and S100B expression. According to developmental changes in the brain, desvenlafaxine affects neonatal growth during pregnancy, which may lead to delay of brain development. So, it is essential to survey the roles of antidepressant drugs on neonatal development during pregnancy.

The Role of Brain-Derived Neurotrophic Factor in Epileptogenesis: an Update

Epilepsy, which is characterized by spontaneous recurrent seizures, is one of the most common and serious chronic neurological diseases in the world. 30% patients failed to control seizures with multiple anti-seizure epileptic drugs, leading to serious outcomes. The pathogenesis of epilepsy is very complex and remains unclear. Brain-derived neurotrophic factor (BDNF), as a member of the neurotrophic factor family, is considered to play an important role in the survival, growth and differentiation of neurons during the development of the central nervous system. Recent years, a series of studies have reported that BDNF can maintain the function of the nervous system and promotes the regeneration of neurons after injury, which is believed to be closely related to epileptogenesis. However, two controversial views (BDNF inhibits or promotes epileptogenesis) still exist. Thus, this mini-review focuses on updating the new evidence of the role of BDNF in epileptogenesis and discussing the possibility of BDNF as an underlying target for the treatment of epilepsy.

An Insight into Molecular Mechanisms and Novel Therapeutic Approaches in Epileptogenesis

Epilepsy is the second most common neurological disease with abnormal neural activity involving the activation of various intracellular signalling transduction mechanisms. The molecular and system biology mechanisms responsible for epileptogenesis are not well defined or understood. Neuroinflammation, neurodegeneration and Epigenetic modification elicit epileptogenesis. The excessive neuronal activities in the brain are associated with neurochemical changes underlying the deleterious consequences of excitotoxicity. The prolonged repetitive excessive neuronal activities extended to brain tissue injury by the activation of microglia regulating abnormal neuroglia remodelling and monocyte infiltration in response to brain lesions inducing axonal sprouting contributing to neurodegeneration. The alteration of various downstream transduction pathways resulted in intracellular stress responses associating endoplasmic reticulum, mitochondrial and lysosomal dysfunction, activation of nucleases, proteases mediated neuronal death. The recently novel pharmacological agents modulate various receptors like mTOR, COX-2, TRK, JAK-STAT, epigenetic modulators and neurosteroids are used for attenuation of epileptogenesis. Whereas the various molecular changes like the mutation of the cell surface, nuclear receptor and ion channels focusing on repetitive episodic seizures have been explored by preclinical and clinical studies. Despite effective pharmacotherapy for epilepsy, the inadequate understanding of precise mechanisms, drug resistance and therapeutic failure are the current fundamental problems in epilepsy. Therefore, the novel pharmacological approaches evaluated for efficacy on experimental models of epilepsy need to be identified and validated. In addition, we need to understand the downstream signalling pathways of new targets for the treatment of epilepsy. This review emphasizes on the current state of novel molecular targets as therapeutic approaches and future directions for the management of epileptogenesis. Novel pharmacological approaches and clinical exploration are essential to make new frontiers in curing epilepsy.

Ameliorative Effects of α-Tocopherol and/or Coenzyme Q10 on Phenytoin-Induced Cognitive Impairment in Rats: Role of VEGF and BDNF-TrkB-CREB Pathway

Phenytoin is one of the most well-known antiepileptic drugs that cause cognitive impairment which is closely related to cAMP response element-binding protein (CREB) brain-derived neurotrophic factor (BDNF) signaling pathway. Moreover, vascular endothelial growth factor (VEGF), an endothelial growth factor, has a documented role in neurogenesis and neuronal survival and cognitive impairment. Therefore, this study aimed to investigate the influence of powerful antioxidants: α-Toc and CoQ10 alone or combined in the preservation of brain tissues and the maintenance of memory formation in phenytoin-induced cognitive impairment in rats. The following behavioral test novel object recognition and elevated plus maze were assessed after 14 days of treatment. Moreover, VEGF, BDNF, TrkB, and CREB gene expression levels in the hippocampus and prefrontal cortex were estimated using RT-PCR. Both α-Toc and CoQ10 alone or combined with phenytoin showed improvement in behavioral tests compared to phenytoin. Mechanistically, α-Toc and/or CoQ10 decreases the VEGF mRNA expression, while increases BDNF-TrKB-CREB mRNA levels in hippocampus and cortex of phenytoin-treated rats. Collectively, α-Toc and/or CoQ10 alleviated the phenytoin-induced cognitive impairment through suppressing oxidative damage. The underlying molecular mechanism of the treating compounds is related to the VEGF and enhancing BDNF-TrkB-CREB signaling pathway. Our study indicated the usefulness α-Toc or CoQ10 as an adjuvant to antiepileptic drugs with an advantage of preventing cognitive impairment and oxidative stress.

Brain-derived neurotrophic factor and epilepsy: a systematic review

Several in vitro, ex vivo and in vivo studies imply brain-derived neurotrophic factor (BDNF) in the pathophysiology of epilepsy. Aim of our work is to report the most important findings regarding BDNF and its potential role in epilepsy. We targeted those publications addressing both in vitro and in vivo evidences of relationship between BDNF and epilepsy. Basic researches, randomized trials, cohort studies, and reviews were contemplated to give a breadth of clinical data. Medline, CENTRAL, and Science Direct were searched till August 2017 using keywords agreed by the authors. Together with a defined role in developmental and mature brain, BDNF has excitatory effects in neuronal cultures and animal brain slices. Furthermore, both BDNF and its conjugated receptor (i.e. Tropomyosin receptor kinase B or TrkB) are increased in animal models and humans with epilepsy, particularly in the temporal and hippocampal areas. Acute injection of BDNF in brain of mice induces seizures, which are almost or totally abolished blocking its transcription and pathway. Chronic infusion of BDNF is conversely associated with a decreased neuronal excitability, probably via several mechanism including an increase in central levels of neuropeptide Y (NPY), altered conductance of chloride, and downregulation of TrkB. While genetic studies are inconclusive, serum BDNF is more frequently higher in patients with epilepsy and appears to be correlated to severity of disease. Current evidences suggest that inhibiting BDNF-TrkB signaling and reinforcing the NPY system could represent a potential therapeutic strategy for epilepsy, especially for temporal lobe epilepsy.

Serum Levels of Brain-Derived Neurotrophic Factor and Insulin-Like Growth Factor 1 Are Associated With Autonomic Dysfunction and Impaired Cerebral Autoregulation in Patients With Epilepsy

Background: Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1) may regulate the autonomic nervous system (ANS) in epilepsy. The present study investigated the role of IGF-1 and BDNF in the regulation of autonomic functions and cerebral autoregulation in patients with epilepsy. Methods: A total of 57 patients with focal epilepsy and 35 healthy controls were evaluated and their sudomotor, cardiovagal, and adrenergic functions were assessed using a battery of ANS function tests, including the deep breathing, Valsalva maneuver, head-up tilting, and Q-sweat tests. Cerebral autoregulation was measured by transcranial doppler during the breath-holding test and the Valsalva maneuver. Interictal serum levels of BDNF and IGF-1 were measured with enzyme-linked immunosorbent assay kits. Results: During interictal period, reduced serum levels of BDNF and IGF-1, impaired autonomic functions, and decreased cerebral autoregulation were noted in patients with epilepsy compared with healthy controls. Reduced serum levels of BDNF correlated with age, adrenergic and sudomotor function, overall autonomic dysfunction, and the autoregulation index calculated in Phase II of the Valsalva maneuver, and showed associations with focal to bilateral tonic-clonic seizures. Reduced serum levels of IGF-1 were found to correlate with age and cardiovagal function, a parameter of cerebral autoregulation (the breath-hold index). Patients with a longer history of epilepsy, higher seizure frequency, and temporal lobe epilepsy had lower serum levels of IGF-1. Conclusions: Long-term epilepsy and severe epilepsy, particularly temporal lobe epilepsy, may perturb BDNF and IGF-1 signaling in the central autonomic system, contributing to the autonomic dysfunction and impaired cerebral autoregulation observed in patients with focal epilepsy.

Chronic treatment with the new anticonvulsant drug lacosamide impairs learning and memory processes in rats: A possible role of BDNF/TrkB ligand receptor system

Cognitive impairment is considered a frequent side effect in the drug treatment of epilepsy. The objective of the present study was to investigate the effects of lacosamide (LCM) on learning and memory processes in rats, on the serum level of brain-derived neurotrophic factor (BDNF) and BDNF/TrkB ligand receptor system expression in the hippocampal formation. Male Wistar rats underwent long-term treatment with three different doses of lacosamide - 3 mg/kg (LCM 3), 10 mg/kg (LCM 10) and 30 mg/kg (LCM 30). All rats were subjected to one active and one passive avoidance tests. The BDNF/TrkB immunohistochemical expression in the hippocampus was measured and serum BDNF was determined. The LCM-treated rats made fewer avoidance responses than controls during acquisition training and in the memory retention test. The number of escapes in the LCM 10 and LCM 30 groups decreased throughout the test, while the rats in the LCM 3 group showed fewer escapes only in the memory test in the active avoidance task. In the step-down test, the latency time of the LCM-30 treated rats was reduced as compared with the controls during the learning session and the short- and long-term memory retention tests. Lacosamide induced a dose-dependent reduction of the hippocampal expression of BDNF and its receptor TrkB. We found no significant difference between BDNF serum levels in the test animals and controls. The results of the study suggest that LCM suppresses the learning and memory processes in rats, with the inhibition of hippocampal BDNF/TrkB ligand receptor system being one of the possible mechanisms causing this effect.

Effect of dexmedetomidine on rats with convulsive status epilepticus and association with activation of cholinergic anti-inflammatory pathway

Convulsive status epilepticus (CSE) is a neurological disease with contraction and extension of limbs, leading to damage of hippocampus and cognition. This study aimed to explore the effects of dexmedetomidine (DEX) on the cognitive function and neuroinflammation in CSE rats. All rats were divided into control group, CSE group and DEX group. Morris water maze test was used to measure cognitive function. Acute hippocampal slices were made to detect long-term potentiation (LTP). Immunohistochemistry was used to determine the expression of α7-nicotinic acetylcholine receptor (α7-nAChR) and interleukin-1β (IL-1β). Enzyme-linked immunosorbent assay (ELISA) was used to measure serum levels of IL-1β, tumor necrosis factor-α (TNF-α), S-100β and brain-derived neurotrophic factor (BDNF). Our results showed that DEX improved the memory damage caused by CSE. DEX reduced seizure severity and increased the amplitudes and sustainable time of LTP, and also inhibited the hippocampal expression of α7-nAChR and IL-1β in CSE rats. DEX treatment decreased serum IL-1β, TNF-α and S-100β levels and increased BDNF levels. The effects of DEX on seizure severity and LTP could be simulated by nicotine or attenuated by concurrent α-bungarotoxin (α-BGT) treatment. In conclusions, DEX significantly improved spatial cognitive dysfunction, reduced seizure severity and increased LTP in CSE rats. Improvements by DEX were closely related to enhancement of cholinergic anti-inflammatory pathway.

Possible involvement of CREB/BDNF signaling pathway in neuroprotective effects of topiramate against methylphenidate induced apoptosis, oxidative stress and inflammation in isolated hippocampus of rats: Molecular, biochemical and histological evidences

Chronic abuse of methylphenidate (MPH) can cause serious neurotoxicity. The neuroprotective effects of topiramate (TPM) were approved, but its putative mechanism remains unclear. In current study the role of CREB/BDNF signaling pathway in TPM protection against methylphenidate-induced neurotoxicity in rat hippocampus was evaluated. 60 adult male rats were divided randomly into six groups. Groups received MPH (10mg/kg) only and concurrently with TPM (50mg/kg and 100mg/kg) and TPM (50 and 100mg/kg) only for 14 days. Open field test (OFT) was used to investigate motor activity. Some biomarkers of apoptotic, anti-apoptotic, oxidative, antioxidant and inflammatory factors were also measured in hippocampus. Expression of total (inactive) and phosphorylated (active) CREB and BDNF were also measured in gene and protein levels in dentate gyrus (DG) and CA1 areas of hippocampus. MPH caused significant decreases in motor activity in OFT while TPM (50 and 100mg/kg) inhibited MPH-induced decreases in motor activity. On the other hand, MPH caused remarkable increases in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels in hippocampal tissue. MPH also caused significant decreases of superoxide dismutase, activity and also decreased CREB, in both forms, BDNF and Bcl-2 protein levels. TPM, by the mentioned doses, attenuated these effects and increased superoxide dismutase, glutathione peroxidase and glutathione reductase activities and also increased CREB, in both forms, BDNF and Bcl-2 protein levels and inhibited MPH induced increase in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels. TPM also inhibited MPH induced decreases in cell number and changes in cell shapes in DG and CA1 areas. TPM can probably act as a neuroprotective agent against MPH induced neurotoxicity and this might have been mediated by CREB/BDNF signaling pathway.

The effect of lamotrigine on learning in mice using the passive avoidance model

INTRODUCTION

Lamotrigine (LTG) is an antiepileptic drug that inhibits the release of glutamate by blocking sodium channels. The present study was conducted to evaluate the effect of LTG in different stages of memory using a passive avoidance learning task in mice.

METHODS

Male albino mice in the weight range 20-25g were used. They were divided into four groups (control group and three groups receiving various doses of LTG). LTG was given in three doses of 10, 25, and 50mg/kg as intraperitoneal (IP) injections. The doses of LTG were used in three injection groups: before acquisition, after consolidation, and before retrieval at 24h. The retention latency times in each group were recorded using a step-through passive avoidance task 24h and one week after consolidation.

RESULTS

Retention latency in the group receiving a high dose of LTG (25mg/kg) after one week was significantly increased in comparison to the group receiving a low dose of LTG (10mg/kg) (267±49.96 vs. 198.87±57.22, P=0.015). With injection of LTG after consolidation, the retention latency times were increased in all doses after a one-week retrieval compared to the control (P=0.023). Kaplan-Mayer surveillance analysis also showed significant differences in the latencies of the LTG-receiving group after 24h and one week's retrieval (P=0.041). Administration of LTG before retrieval at 24h showed a significant difference in retention latency time, which was increased for two doses of LTG (10 and 50mg/kg) after one week (203.5±63.67 vs. 270.25±19.78, P=0.024).

CONCLUSION

LTG at higher doses may facilitate the learning process in mice and appears to improve memory function at different stages.