BDNF as potential biomarker of epilepsy severity and psychiatric comorbidity: pitfalls in the clinical population

Comparison of neurological and psychiatric profiles of people with epilepsy based on the presence and timing of potentially psychologically traumatic experiences

Objective: While psychological trauma in people with epilepsy (PWE) is a major issue, there is limited research on the interactions between such trauma and epilepsy. Therefore, our primary aim is to describe types and timing of potentially psychologically traumatic experiences (PPTE) in relation to epilepsy onset. Our secondary objective is to evaluate the impact of the timing of the PPTE on patients' psychiatric and neurological profiles.Methods: We conducted an observational study involving 182 PWE, excluding patients with comorbid functional/dissociative seizures. All participants underwent a comprehensive psychiatric evaluation, including biographical, neurological, psychiatric, and traumatic data collection through a semi-structured clinical interview and standardized scales. We compared the neurological and psychiatric characteristics of three groups of patients: those without PPTE, those with PPTE occurring before the onset of epilepsy, and those with PPTE occurring after the onset of their epilepsy.Results: Sixty-one patients (33.5%) reported having experienced PPTE before the onset of epilepsy, 65 patients (35.7%) reported having experienced PPTE after the onset of their epilepsy, and 56 patients (30.8%) had no history of PPTE neither before nor after the onset of epilepsy. The 'before' group had a significantly higher prevalence of epilepsy localized in the temporal lobe (p = .043). The 'after' group showed significantly more general psychiatric symptoms (p = .026), as well as more postictal mood and anxiety symptoms (p = .014). Additionally, the 'before' group reported a higher number of past traumatic experiences, with childhood traumatic experiences being more prevalent. According to our multinomial logistic regression model, higher temporal localization (p = .028) and fewer febrile seizures (p = .030) were significant predictors for the 'before' group.Significance: This study highlights the potential impact of the timing of PPTE on patients' psychiatric and neurological profiles. It underscores the importance of systematically assessing psychiatric and posttraumatic comorbidities in PWE. The role of trauma in temporal epilepsy requires further investigation.

Altered Neuroplasticity in Epilepsy is Associated with Neuroinflammation and Oxidative Stress: In vivo Evidence of Brain-Derived Extracellular Vesicles

Purpose

Recurrent seizures lead to self-reconstruction of the central nervous system, which is termed the neuroplasticity of epilepsy. While preclinical studies implicate neuroinflammation and oxidative stress in epilepsy-associated neuroplasticity, in vivo molecular-level evidence in humans is lacking.

Patients and Methods

We used astrocyte-derived extracellular vesicles (ADEVs) and neuron-derived extracellular vesicles (NDEVs) as brain-derived biomarkers to explore biomarkers of neuroplasticity, neuroinflammation, and oxidative stress. A total of 50 patients in the epilepsy group (EP) and 25 matched healthy controls (HC) were recruited for this study. Plasma ADEVs and NDEVs were isolated and confirmed, and the levels of the EV marker CD81, the neuroplasticity marker brain-derived neurotrophic factor (BDNF), and the neuroinflammation marker tumor necrosis factor α (TNF-α) in ADEVs, as well as the markers of oxidative stress, superoxide dismutase 1 (SOD1) and malondialdehyde (MDA), in NDEVs were measured.

Results

BDNF levels in ADEVs and SOD1 levels in NDEVs from EP were significantly lower than those in HC, whereas TNF-α levels in ADEVs and MDA levels in NDEVs were significantly increased, and the results remained stable after normalization by CD81. Spearman correlation analysis revealed that BDNF levels in ADEVs were negatively correlated with TNF-α levels in ADEVs and MDA levels in NDEVs and positively correlated with SOD1 levels in NDEVs.

Conclusion

The innovative use of ADEVs and NDEVs as brain-derived biomarkers in this study provides in vivo evidence that epilepsy may result in impaired neuroplasticity and may be associated with increased neuroinflammation and oxidative stress.

Nuclei-Specific Amygdala Enlargement Is Linked to Psychiatric Comorbidities in Drug-Resistant Focal Epilepsy

OBJECTIVE

Amygdala enlargement has been the subject of controversial studies regarding its significance in terms of pathogenicity both in epilepsy and in psychiatric comorbidities such as anxiety, depression, and post-traumatic stress disorder. However, no causal link has been established in either direction, and the role of distinct amygdala nuclei remains unknown. We investigated volumetric changes of the amygdala and its nine main nuclei and their associations with psychiatric comorbidities in patients with drug-resistant focal epilepsy.

METHODS

Eighty-seven adult patients with drug-resistant focal epilepsy, available 7 T MRI, and completed standardized psychiatric assessments were included. Whole amygdala and nuclei volumes were quantified and compared to healthy controls. Correlations between the amygdala or nuclei volumes and psychiatric scores were analyzed, as well as the prevalence and severity of each comorbidity depending on the presence of enlargement.

RESULTS

Amygdala enlargement was present in 41% of patients, with bilateral enlargement observed in 30% of these cases, while atrophy was noted in 2%. Bilateral enlargement correlated with higher posttraumatic stress disorder and depression scores. Central nucleus enlargement was associated with a greater prevalence of depression and more severe anxiety. Bilateral enlargement of distinct nuclei in the basolateral group was linked to more severe depression or posttraumatic stress disorder.

INTERPRETATION

These findings suggest that bilateral amygdala enlargement, particularly in specific nuclei, may serve as a morphological marker of psychiatric comorbidities in epilepsy. Further research is needed to explore the specific roles of amygdala nuclei in psycho-epileptogenesis.

Unlocking Alzheimer's Disease: The Role of BDNF Signaling in Neuropathology and Treatment

Alzheimer's disease (AD) remains one of the most debilitating neurodegenerative disorders, with its pathological hallmark being progressive cognitive decline and memory loss. Recent research has illuminated the crucial role of the brain-derived neurotrophic factor (BDNF) in the central nervous system (CNS), highlighting its impact on neurogenesis, synaptic plasticity, and neuronal survival. Dysregulation of the BDNF signaling axis, particularly the imbalance between its precursor form and mature BDNF, is strongly implicated in the pathophysiology of AD. This review explores the molecular mechanisms through which BDNF modulates AD neuropathology and presents novel therapeutic strategies to activate BDNF signaling. We focus on the potential of BDNF activators, such as TrkB agonists and mimetic molecules, to restore synaptic function and ameliorate cognitive deficits in AD. Furthermore, we examine the challenges in translating these findings into clinical practice, including issues with blood-brain barrier penetration and the need for precise receptor targeting. The review emphasizes the therapeutic potential of repurposed drugs, including statins and metformin, in enhancing BDNF signaling and offers new insights into the future of AD treatment. Ultimately, this work provides a compelling argument for BDNF-based therapies as a promising avenue for mitigating the cognitive decline associated with Alzheimer's disease, signaling a hopeful direction for future research and clinical trials.

Cathodal weak direct current decreases epileptic excitability with reduced neuronal activity and enhanced delta oscillations

Seizures are manifestations of hyperexcitability in the brain. Non-invasive weak current stimulation, delivered through cathodal transcranial direct current stimulation (ctDCS), has emerged to treat refractory epilepsy and seizures, although the cellular-to-populational electrophysiological mechanisms remain unclear. Using the ctDCS in vivo model, we investigate how neural excitability is modulated through weak direct currents by analysing the local field potential (LFP) and extracellular unit spike recordings before, during and after ctDCS versus sham stimulation. In rats with kainic acid (KA)-induced acute hippocampal seizures, ctDCS reduced seizure excitability by decreasing the number and amplitude of epileptic spikes in LFP and enhancing delta (δ) power. We identified unit spikes of putative excitatory neurons in CA1 stratum pyramidale based on waveform sorting and validated via optogenetic inhibitions which increased aberrantly in seizure animals. Notably, cathodal stimulation significantly reduced these unit spikes, whereas anodal stimulation exhibited the opposite effect, showing polarity-specific and current strength-dependent responses. The reduced unit spikes after ctDCS coupled to δ oscillations with an increased coupling strength. These effects occurred during stimulation and lasted 90 min post-stimulation, accompanied by inhibitory short-term synaptic plasticity changes shown in paired-pulse stimulation after ctDCS. Consistently, neuronal activations measured by c-Fos significantly decreased after ctDCS, particularly in CaMKII+-excitatory neurons while increased in GAD+-inhibitory neurons. In conclusion, epileptic excitability was alleviated with cathodal weak direct current stimulation by diminishing excitatory neuronal activity and enhancing endogenous δ oscillations through strengthened coupling between unit spikes and δ waves, along with inhibitory plasticity changes, highlighting the potential implications to treat brain disorders characterized by hyperexcitability. KEY POINTS: Electric fields generated by transcranial weak electric current stimulation were measured at CA1, showing polarity-specific and current strength-dependent modulation of unit spike activity. Polyspike epileptiform discharges were observed in rats with kainic acid (KA)-induced hippocampal seizures. Cathodal transcranial direct current stimulation (ctDCS) reduced the number and amplitude of the epileptic spikes in local field potentials (LFPs) while increased δ oscillations. Neuronal unit spikes aberrantly increased in seizures and coupled with epileptiform discharges. ctDCS reduced excitatory neuronal firings at CA1 and strengthened the coupling between unit spikes and δ waves. Neuronal activations, measured by c-Fos, decreased in CaMKII+-excitatory neurons while increased in GAD+-inhibitory neurons after ctDCS. These effects on LFP and unit spikes lasted up to 90 min post-stimulation. Inhibitory short-term plasticity changes detected through paired-pulse stimulation underpin the enduring effects of ctDCS on seizures.

Role of Serum Brain-Derived Neurotrophic Factor as a Biomarker of Chronic Pain in Older Adults

BACKGROUND

Serum brain-derived neurotrophic factor (BDNF) has emerged as a promising biomarker for chronic pain (CP) research and treatment. Yet, most human studies have been limited by small sample sizes, inadequate control of confounders and a lack of focus on sex and mental health differences.

METHODS

This study included data from 1932 community-dwelling individuals aged ≥ 65 years, randomly sampled from the Spanish general population. Serum BDNF was quantified by ELISA. CP characteristics were assessed using the European Chronic Pain Survey and classified according to electronic medical records (ICPC-2 codes). Linear regression models-adjusted for sociodemographic, lifestyle and clinical factors-and stratified analyses by sex and depression status (defined by Geriatric Depression Scale score, recent physician diagnosis or antidepressant use) were performed.

RESULTS

Among 962 men and 970 women, mean BDNF concentrations were 18.55 (5.66) ng/mL and 19.39 (5.77) ng/mL, respectively. Most participants reported pain in multiple locations (median 3 sites, interquartile range: 2-4). In 511 participants with CP, probable musculoskeletal pain was predominant (n = 446), followed by nociplastic (n = 71), neuropathic (n = 54), visceral (n = 51) and vascular pain (n = 22). Notably, in non-depressed participants (n = 1639), women with severe or interfering pain showed lower BDNF concentrations [β coefficient (95% confidence interval) = -2.62 ng/mL (-5.03, -0.22) and -3.09 ng/mL (-4.71, -1.47), respectively] compared to those without CP-a pattern not seen in men. Conversely, among men with depression (n = 293), both severe [-5.12 g/mL (-9.26, -0.99)] and interfering [-4.95 g/mL (-8.29, -1.61)] pain were linked to lower BDNF, a trend absent in depressed women. Similar associations were observed in analyses of musculoskeletal and nociplastic pain subtypes.

CONCLUSIONS

While serum BDNF is a promising biomarker for CP, its reliability for gauging pain severity depends on patient sex and depression status. These factors must be considered to enhance the accuracy and clinical relevance of BDNF in CP evaluation.

SIGNIFICANCE

Our study is the first to reveal that the relationship between serum BDNF and chronic pain is distinctly modulated by sex and depression. This novel insight challenges one-size-fits-all biomarker approaches and paves the way for more personalised, precision-based strategies in chronic pain diagnosis and management.

Mitigating seizure-induced cognitive deficits in mice induced with pentylenetetrazol by roflumilast through targeting the NLRP3 inflammasome/BDNF/SIRT3 pathway and regulating ferroptosis

AIMS

Comorbidities with epilepsy and antiseizure medications (ASMs) are currently the main challenges in treating epilepsy. The current study evaluates for the first time the neuroprotective effect of roflumilast (ROF) alone or combined with phenytoin (PHT) against pentylenetetrazol (PTZ)-induced kindling in mice. It focuses on the crosstalk between the NOD-like receptor protein 3 (NLRP3)/caspase 1/interleukin 1β (IL-1β) cascade and the brain-derived neurotrophic factor (BDNF)/sirtuin 3 (SIRT3) pathway as possible strategies to treat epilepsy.

MAIN METHODS

The kindled mouse model was induced via fifteen (35 mg/kg) intraperitoneal injections every other day. Roflumilast (0.4 mg/kg) and phenytoin (30 mg/kg) were orally administered daily from the start until the end of the experiment. Following the PTZ injection, the seizure severity score was assessed. The Morris water maze (MWM) test was performed to evaluate cognition. Histopathological examinations of hippocampi were conducted.

KEY FINDINGS

Roflumilast significantly improved neurobehavioral and histological assessments, whereas Racine scores declined. The improvement was confirmed through BDNF upregulation in contrast to NLRP3 and caspase-1 in the hippocampus, as revealed immunohistochemically. In addition, roflumilast induced a prominent elevation in gamma-aminobutyric acid (GABA), sirtuin 3 (SIRT3), and glutathione peroxidase (GPX4), whereas malondialdehyde (MDA), and arachidonic acid 15-lipoxygenase (ALOX15) expressions were downregulated.

SIGNIFICANCE

Our findings demonstrate that roflumilast conferred neuroprotective benefits against PTZ-induced kindling seizures, suggesting its potential as a novel adjuvant therapy for epilepsy-related disorders. This effect might be due to the modification of the NLRP3 inflammasome/BDNF pathway, ferroptosis, and a decrease in oxidative stress and neuroinflammation.

Integrated Proteomics and Lipidomics Analysis of Hippocampus to Reveal the Metabolic Landscape of Epilepsy

Epilepsy encompasses a spectrum of chronic brain disorders characterized by transient central nervous system dysfunctions induced by recurrent, aberrant, synchronized neuronal discharges. Hippocampal sclerosis (HS) is identified as the predominant pathological alteration in epilepsy, particularly in temporal lobe epilepsy. This study investigates the metabolic profiles of epileptic hippocampal tissues using proteomics and lipidomics techniques. An epilepsy model was established in Sprague-Dawley (SD) rats via intraperitoneal injection of pentylenetetrazole (PTZ), with hippocampal tissue samples subsequently extracted for histopathological examination. Proteomics analysis was conducted using isobaric tags for relative and absolute quantitation (iTRAQ) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS), while lipidomics analysis employed ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC Q-TOF/MS). Proteomic analysis identified 144 proteins with significant differential expression in acute epileptic hippocampal tissue and 83 proteins in chronic epileptic hippocampal tissue. Key proteins, including neurofilament heavy (Nefh), vimentin (Vim), gelsolin (Gsn), NAD-dependent protein deacetylase (Sirt2), 2',3'-cyclic-nucleotide 3'-phosphodiesterase (Cnp), myocyte enhancer factor 2D (Mef2d), and Cathepsin D (Ctsd), were pivotal in epileptic hippocampal tissue injury and validated through parallel reaction monitoring (PRM). Concurrently, lipid metabolomics analysis identified 32 metabolites with significant differential expression in acute epileptic hippocampal tissue and 61 metabolites in chronic epileptic hippocampal tissue. Bioinformatics analysis indicated that glycerophospholipid (GP) metabolism, glycosylphosphatidylinositol (GPI)-anchor biosynthesis, and glycerolipid (GL) metabolism were crucial in epileptic hippocampal tissue injury. Integrated proteomics and lipidomics analysis revealed key protein-lipid interactions in acute and chronic epilepsy and identified critical pathways such as sphingolipid signaling, autophagy, and calcium signaling. These findings provide deeper insights into the pathophysiological mechanisms of epileptic hippocampal tissue damage, potentially unveiling novel therapeutic avenues for clinicians.

BDNF/Cyclin D1 Signaling System and Cognitive Performance After Perampanel and Lacosamide Treatment Singly or in Combination in an Experimental Model of Temporal Lobe Epilepsy

Epilepsy is a common brain function disorder. The present study aims to evaluate the long-term effect of perampanel (PRM) and lacosamide (LCM), administered singly in a high-dose or in a low-dose combination of both, on comorbid anxiety, cognitive impairment, BDNF, and Cyclin D1 hippocampal expression in an experimental model of temporal lobe epilepsy with lithium-pilocarpine. PRM (3 mg/kg, p.o.)/LCM (30 mg/kg, p.o.) or PRM+LCM (0.5 mg/kg + 3 mg/kg, p.o.) treatments were administered three hours after the lithium-pilocarpine-induced status epilepticus and continued for up to ten weeks in adult Wistar rats. Our study demonstrated that perampanel and lacosamide administered singly in high doses improved epilepsy-associated cognitive impairment through ameliorating anxiety and facilitating passive learning and memory, with spatial and recognition memory measured in the elevated plus maze, step-through, Y-maze, and object recognition tests, respectively. In addition, the combination of both drugs in low doses demonstrated similar anxiolytic and cognitive-improving effects compared to the singly administered drugs. Moreover, the three experimental groups enhanced the hippocampal expression of the neurotrophic factor BDNF and mitigated the increased levels of the apoptotic factor Cyclin D1. These beneficial effects could be essential mechanisms through which administered anticonvulsants preserve neuronal survival and homeostasis in the CNS and especially in the hippocampus.

Reduced Levels of Lacrimal Glial Cell Line-Derived Neurotrophic Factor (GDNF) in Patients with Focal Epilepsy and Focal Epilepsy with Comorbid Depression: A Biomarker Candidate

Our previous studies showed that in patients with brain diseases, neurotrophic factors in lacrimal fluid (LF) may change more prominently than in blood serum (BS). Since glial cell line-derived neurotrophic factor (GDNF) is involved in the control of neuronal networks in an epileptic brain, we aimed to assess the GDNF levels in LF and BS as well as the BDNF and the hypothalamic-pituitary-adrenocortical and inflammation indices in BS of patients with focal epilepsy (FE) and epilepsy and comorbid depression (FE + MDD) and to compare them with those of patients with major depressive disorder (MDD) and healthy controls (HC). GDNF levels in BS were similar in patients and HC and higher in FE taking valproates. GDNF levels in LF were significantly lower in all patient groups compared to controls, and independent of drugs used. GDNF concentrations in LF and BS positively correlated in HC, but not in patient groups. BDNF level was lower in BS of patients compared with HC and higher in FE + MDD taking valproates. A reduction in the GDNF level in LF might be an important biomarker of FE. Logistic regression models demonstrated that the probability of FE can be evaluated using GDNF in LF and BDNF in BS; that of MDD using GDNF in LF and cortisol and TNF-α in BS; and that of epilepsy with MDD using GDNF in LF and TNF-α and BDNF in BS.

Stress and Epilepsy: Towards Understanding of Neurobiological Mechanisms for Better Management

Stress has been identified as a major contributor to human disease and is postulated to play a substantial role in epileptogenesis. In a significant proportion of individuals with epilepsy, sensitivity to stressful events contributes to dynamic symptomatic burden, notably seizure occurrence and frequency, and presence and severity of psychiatric comorbidities [anxiety, depression, posttraumatic stress disorder (PTSD)]. Here, we review this complex relationship between stress and epilepsy using clinical data and highlight key neurobiological mechanisms including the hypothalamic-pituitary-adrenal (HPA) axis dysfunction, altered neuroplasticity within limbic system structures, and alterations in neurochemical pathways such as brain-derived neurotrophic factor (BNDF) linking epilepsy and stress. We discuss current clinical management approaches of stress that help optimize seizure control and prevention, as well as psychiatric comorbidities associated with epilepsy. We propose that various shared mechanisms of stress and epilepsy present multiple avenues for the development of new symptomatic and preventative treatments, including disease modifying therapies aimed at reducing epileptogenesis. This would require close collaborations between clinicians and basic scientists to integrate data across multiple scales, from genetics to systems biology, from clinical observations to fundamental mechanistic insights. In future, advances in machine learning approaches and neuromodulation strategies will enable personalized and targeted interventions to manage and ultimately treat stress-related epileptogenesis.