Brain-derived neurotrophic factor ameliorates brain stem cardiovascular dysregulation during experimental temporal lobe status epilepticus

The role of angiotensin receptor blockers in treating epilepsy: a review

Epilepsy is a chronic brain disease with a global prevalence of 70 million people. According to the World Health Organization, roughly 5 million new cases are diagnosed every year. Anti-seizure drugs are the treatment of choice. However, in roughly one third of the patients, these drugs fail to produce the desired effect. As a result, finding novel treatments for epilepsy becomes inevitable. Recently, angiotensin receptor blockers have been proposed as a treatment to reduce the over-excitation of neurons in epilepsy. For this purpose, we conducted a review using Medline/PubMed and Google Scholar using the relevant search terms and extracted the relevant data in a table. Our review suggests that this novel approach has a very high potential to treat epilepsy, especially in those patients who fail to respond to conventional treatment options. However, more extensive and human-based trials should be conducted to reach a decisive conclusion. Nevertheless, the use of ARBs in patients with epilepsy should be carefully monitored keeping the adverse effects in mind.

Alzheimer's Disease and Protein Kinases

Alzheimer's disease (AD) is the most common neurodegenerative disorder and accounts for more than 60-80% of all cases of dementia. Loss of pyramidal neurons, extracellular amyloid beta (Abeta) accumulated senile plaques, and neurofibrillary tangles that contain hyperphosphorylated tau constitute the main pathological alterations in AD.Synaptic dysfunction and extrasynaptic N-methyl-D-aspartate receptor (NMDAR) hyperactivation contributes to excitotoxicity in patients with AD. Amyloid precursor protein (APP) and Abeta promoted neurodegeneration develop through the activation of protein kinase signaling cascade in AD. Furthermore, ultimate neuronal death in AD is under control of protein kinases-related signaling pathways. In this chapter, critical check-points within the cross-talk between neuron and protein kinases have been defined regarding the initiation and progression of AD. In this context, amyloid cascade hypothesis, neuroinflammation, oxidative stress, granulovacuolar degeneration, loss of Wnt signaling, Abeta-related synaptic alterations, prolonged calcium ions overload and NMDAR-related synaptotoxicity, damage signals hypothesis and type-3 diabetes are discussed briefly.In addition to clinical perspective of AD pathology, recommendations that might be effective in the treatment of AD patients have been reviewed.

Involvement of H2 S, NO and BDNF-TrkB signalling pathway in the protective effects of simvastatin against pentylenetetrazole-induced kindling and cognitive impairments in mice

Cognitive dysfunction was observed in pentylenetetrazole (PTZ)-kindled mice. The potential effectiveness of simvastatin (SIM) on PTZ-induced kindling and cognitive impairments in mice was evaluated. The influence of SIM on hydrogen sulphide (H2 S), nitric oxide (NO), reactive aldehydes and brain-derived neurotrophic factor/tyrosine receptor kinase B (BDNF-TrkB) signalling was also investigated. Kindling and cognitive impairments in mice were induced by 12 ip injections of PTZ (35 mg/kg) once every alternate day. The levels of reactive aldehydes and nitrite were increased while H2 S was decreased in PTZ-treated mice. These results were accompanied by a reduction in the gene expression of aldehyde dehydrogenase 2, cystathionine β-synthase, BDNF and TrkB. In PTZ-kindled mice, a rise in brain inducible nitric oxide synthase protein expression associated with histopathological changes was observed. SIM administration (1, 5 and 10 mg/kg, daily orally) along with alternate day of PTZ (35 mg/kg) resulted in a decrease in PTZ-induced kindling with a dose-dependent improvement in cognitive function. SIM (10 mg/kg) prevented, to variable extent, the disturbances associated with PTZ-kindled mice with cortical, cerebellar and hippocampal structural improvement. These results suggested that SIM triggers multiple mechanisms that improve cognitive function in PTZ-kindled mice through modulation of oxidative stress, H2 S, NO and BDNF-TrkB signalling pathway.

Role of the Angiotensin Pathway and its Target Therapy in Epilepsy Management

Despite extensive research on epileptogenesis, there is still a need to investigate new pathways and targeted therapeutic approaches in this complex process. Inflammation, oxidative stress, neurotoxicity, neural cell death, gliosis, and blood–brain barrier (BBB) dysfunction are the most common causes of epileptogenesis. Moreover, the renin–angiotensin system (RAS) affects the brain’s physiological and pathological conditions, including epilepsy and its consequences. While there are a variety of available pharmacotherapeutic approaches, information on new pathways is in high demand and the achievement of treatment goals is greatly desired. Therefore, targeting the RAS presents an interesting opportunity to better understand this process. This has been supported by preclinical studies, primarily based on RAS enzyme, receptor-inhibition, and selective agonists, which are characterized by pleiotropic properties. Although there are some antiepileptic drugs (AEDs) that interfere with RAS, the main targeted therapy of this pathway contributes in synergy with AEDs. However, the RAS-targeted treatment alone, or in combination with AEDs, requires clinical studies to contribute to, and clarify, the evidence on epilepsy management. There is also a genetic association between RAS and epilepsy, and an involvement of pharmacogenetics in RAS, so there are possibilities for the development of new diagnostic and personalized treatments for epilepsy.

Metabolic and Homeostatic Changes in Seizures and Acquired Epilepsy-Mitochondria, Calcium Dynamics and Reactive Oxygen Species

Acquired epilepsies can arise as a consequence of brain injury and result in unprovoked seizures that emerge after a latent period of epileptogenesis. These epilepsies pose a major challenge to clinicians as they are present in the majority of patients seen in a common outpatient epilepsy clinic and are prone to pharmacoresistance, highlighting an unmet need for new treatment strategies. Metabolic and homeostatic changes are closely linked to seizures and epilepsy, although, surprisingly, no potential treatment targets to date have been translated into clinical practice. We summarize here the current knowledge about metabolic and homeostatic changes in seizures and acquired epilepsy, maintaining a particular focus on mitochondria, calcium dynamics, reactive oxygen species and key regulators of cellular metabolism such as the Nrf2 pathway. Finally, we highlight research gaps that will need to be addressed in the future which may help to translate these findings into clinical practice.

More Insight into BDNF against Neurodegeneration: Anti-Apoptosis, Anti-Oxidation, and Suppression of Autophagy

In addition to its well-established neurotrophic action, brain-derived neurotrophic factor (BDNF) also possesses other neuroprotective effects including anti-apoptosis, anti-oxidation, and suppression of autophagy. We have shown before that BDNF triggers multiple mechanisms to confer neuronal resistance against 3-nitropropionic acid (3-NP)-induced mitochondrial dysfunction in primary rat cortical cultures. The beneficial effects of BDNF involve the induction of anti-oxidative thioredoxin with the resultant expression of anti-apoptotic B-cell lymphoma 2 (Bcl-2) as well as erythropoietin (EPO)-dependent stimulation of sonic hedgehog (SHH). We further revealed that BDNF may bring the expression of sulfiredoxin, an ATP-dependent antioxidant enzyme, to offset mitochondrial inhibition in cortical neurons. Recently, we provided insights into another novel anti-oxidative mechanism of BDNF, which involves the augmentation of sestrin2 expression to endow neuronal resistance against oxidative stress induced by 3-NP; BDNF induction of sestrin2 entails the activation of a pathway involving nitric oxide (NO), cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG), and nuclear factor-κB (NF-κB). Apart from anti-apoptosis and anti-oxidation, we demonstrated in our most recent study that BDNF may activate the mammalian target of rapamycin (mTOR) with resultant activation of transcription factor c-Jun, thereby stimulating the expression of p62/sequestosome-1 to suppress heightened autophagy as a result of 3-NP exposure. Together, our results provide in-depth insight into multi-faceted protective mechanisms of BDNF against mitochondrial dysfunction commonly associated with the pathogenesis of many chronic neurodegenerative disorders. Delineation of the protective signaling pathways elicited by BDNF would endow a rationale to develop novel therapeutic regimens to halt or prevent the progression of neurodegeneration.

Sumoylation of IkB attenuates NF-kB-induced nitrosative stress at rostral ventrolateral medulla and cardiovascular depression in experimental brain death

BACKGROUND

Small ubiquitin-related modifier (SUMO) is a group of proteins that participates in post-translational modifications. One known SUMO target is the transcription factor nuclear factor-kB (NF-kB) that plays a pivotal role in many disease processes; sumoylation inactivates NF-kB by conjugation with inhibitors of NF-kB (IkB). Our laboratory demonstrated previously that transcriptional upregulation of nitric oxide synthase II (NOS II) by NF-kB, leading to nitrosative stress by the formation of peroxynitrite in the rostral ventrolateral medulla (RVLM), underpins the defunct brain stem cardiovascular regulation that precedes brain death. Based on an experimental endotoxemia model, this study evaluated the hypothesis that sumoylation plays a pro-life role in brain death by interacting with the NF-kB/NOS II/peroxynitrite signaling pathway in the RVLM.

RESULTS

In Sprague-Dawley rats, intravenous administration of Escherichia coli lipopolysaccharide (LPS; 10 mg kg-1) elicited an augmentation of SUMO-1 and ubiquitin-conjugase 9 (Ubc9) mRNA or protein levels, alongside SUMO-1-conjugated proteins in the RVLM. Immunoneutralization of SUMO-1 or Ubc9 in the RVLM significantly potentiated the already diminished sumoylation of IkBα and intensified NF-kB activation and NOS II/peroxynitrite expression in this brain stem substrate, together with exacerbated fatality, cardiovascular depression and reduction of an experimental index of a life-and-death signal detected from arterial pressure that disappears in comatose patients signifying failure of brain stem cardiovascular regulation before brain death.

CONCLUSION

We conclude that sumoylation of IkB in the RVLM ameliorates the defunct brain stem cardiovascular regulation that underpins brain death in our experimental endotoxemia modal by reducing nitrosative stress via inhibition of IkB degradation that diminishes the induction of the NF-kB/NOS II/peroxynitrite signaling cascade.

Status epilepticus: Using antioxidant agents as alternative therapies

The epileptic state, or status epilepticus (SE), is the most serious situation manifested by individuals with epilepsy, and SE events can lead to neuronal damage. An understanding of the molecular, biochemical and physiopathological mechanisms involved in this type of neurological disease will enable the identification of specific central targets, through which novel agents may act and be useful as SE therapies. Currently, studies have focused on the association between oxidative stress and SE, the most severe epileptic condition. A number of these studies have suggested the use of antioxidant compounds as alternative therapies or adjuvant treatments for the epileptic state.

The pathophysiology of cardiac dysfunction in epilepsy

Alterations in cardiac electrophysiology are an established consequence of long-standing drug resistant epilepsy. Patients with chronic epilepsy display abnormalities in both sinoatrial node pacemaker current as well as ventricular repolarizing current that places them at a greater risk of developing life-threatening cardiac arrhythmias. The development of cardiac arrhythmias secondary to drug resistant epilepsy is believed to be a key mechanism underlying the phenomenon of Sudden Unexpected Death in EPilepsy (SUDEP). Though an increasing amount of studies examining both animal models and human patients have provided evidence that chronic epilepsy can detrimentally affect cardiac function, the underlying pathophysiology remains unclear. Recent work has shown the expression of several key cardiac ion channels to be altered in animal models of genetic and acquired epilepsies. This has led to the currently held paradigm that cardiac ion channel expression may be secondarily altered as a consequence of seizure activity-resulting in electrophysiological cardiac dysfunction. Furthermore, cortical autonomic dysfunction - resulting from seizure activity-has also been suggested to play a role, whereby seizure activity may indirectly influence cardiac function via altering centrally-mediated autonomic output to the heart. In this review, we discuss various cardiac dysrhythmias associated with seizure events-including tachycardia, bradycardia and QT prolongation, both ictally and inter-ictally, as well as the role of the autonomic nervous system. We further discuss key ion channels expressed in both the heart and the brain that have been shown to be altered in epilepsy and may be responsible for the development of cardiac dysrhythmias secondary to chronic epilepsy.

Interictal serum brain-derived neurotrophic factor level reflects white matter integrity, epilepsy severity, and cognitive dysfunction in chronic temporal lobe epilepsy

OBJECTIVE

Most patients with temporal lobe epilepsy (TLE) have epileptic foci originating from the medial temporal lobe, particularly the hippocampus. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin growth factor mainly expressed in the hippocampus, though it is not known whether the circulating level of BDNF reflects cognitive performance or white matter structural changes in chronic TLE.

METHODS

Thirty-four patients with TLE and 22 healthy controls were enrolled for standardized cognitive tests, diffusion tensor imaging, and serum BDNF measurement. The patients were further divided into a subgroup with unilateral TLE (n=23) and a subgroup with bilateral TLE (n=11) for clinical and neuroimaging comparisons.

RESULTS

There were significantly lower BDNF levels in the patients with TLE compared with the controls, with significance contributed mainly from the subgroup with bilateral TLE, which also had more frequent seizures. The BDNF levels correlated with epilepsy duration (σ=-0.355; p=0.040) and fractional anisotropy (FA) in the left temporal lobe, left thalamus, and right hippocampus. Using a regression model, BDNF level predicted verbal memory score. Further, design fluency scores were predicted by serum BDNF level via the interactions with left temporal FA.

CONCLUSIONS

Serum BDNF levels reflected longer epilepsy duration, impaired white matter integrity, and poor cognitive function in patients with chronic TLE.

Upregulation of FLJ10540, a PI3K-association protein, in rostral ventrolateral medulla impairs brain stem cardiovascular regulation during mevinphos intoxication

FLJ10540, originally identified as a microtubule-associated protein, induces cell proliferation and migration during tumorigenesis via the formation of FLJ10540-PI3K complex and enhancement of PI3K kinase activity. Interestingly, activation of PI3K/Akt cascade, leading to upregulation of nitric oxide synthase II (NOS II)/peroxynitrite signaling in the rostral ventrolateral medulla (RVLM), the brain stem site that maintains blood pressure and sympathetic vasomotor tone, mediates the impairment of brain stem cardiovascular regulation induced by the pesticide mevinphos. We evaluated the hypothesis that upregulation of FLJ10540 in the RVLM is upstream to this repertoire of signaling cascade that underpins mevinphos-induced circulatory depression. Microinjection bilaterally of mevinphos (10nmol) into the RVLM of anesthetized Sprague-Dawley rats induced a progressive hypotension that was accompanied by an increase (Phase I), followed by a decrease (Phase II) of an experimental index for baroreflex-mediated sympathetic vasomotor tone. There was augmentation in FLJ10540 mRNA in the RVLM or FLJ10540 protein in RVLM neurons, both of which were causally and temporally related to an augmentation of binding between the catalytic subunit (p110) and regulatory subunit (p85) of PI3K, phosphorylation of Akt at Thr308 site, and NOS II, superoxide or peroxynitrite level in the RVLM. Immunoneutralization of FJL10540 in the RVLM significantly antagonized those biochemical changes, and blunted the progressive hypotension and the reduced baroreflex-mediated sympathetic vasomotor tone during mevinphos intoxication. We conclude that upregulation of FLJ10540 in the RVLM elicits impairment of brain stem cardiovascular regulation that underpins circulatory depression during mevinphos intoxication via activation of PI3K/Akt/NOS II/peroxynitrite signaling cascade in the RVLM.

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism affects sympathetic tone in a gender-specific way

The Val/Val genotype of the brain-derived neurotrophic factor (BDNF) polymorphism (Val66Met) has been reported to affect human anxiety-related phenotypes. Substantial research has demonstrated that anxiety is associated with sympathetic activation, while sex steroid hormones have been shown to exert differential actions in regulating BDNF expression. Thus, we examined whether the BDNF variant modulates autonomic function in a gender-dependent manner. From 708 adults initially screened for medical and psychiatric illnesses, a final cohort of 583 drug-free healthy Han Chinese (355 males, 228 females; age 34.43±8.42 years) was recruited for BDNF genotyping (Val/Val: 136, 23.3%, Val/Met: 294, 50.4%, and Met/Met: 153, 26.2%). Time- and frequency-domain analyses of heart rate variability (HRV) were used to assess autonomic outflow to the heart. Significant genotype-by-gender interaction effects were found on HRV indices. Even after adjusting for possible confounders, male participants bearing the Val/Val genotype had significant increases in low frequency (LF), LF% and LF/high frequency (HF) ratio, indicating altered sympathovagal balance with increased sympathetic modulation, compared to male Met/Met homozygotes. Females, however, showed an opposite but non-significant pattern. These results suggest that the studied BDNF polymorphism is associated with sympathetic control in a gender-specific way. The findings here support the view that male subjects with the Val/Val genotype have increased risk of anxiety by association with sympathetic activation.

Evidence for involvement of the CD40/CD40L system in post-stroke epilepsy

Post-stroke epilepsy (PSE) has a negative effect on stroke prognosis and quality of life. The CD40/CD40L system is reported to be involved in the progression of multiple disease states. We investigated the association between functional polymorphism of CD40 and PSE susceptibility, and we also explored the role of the CD40/CD40L system in PSE. A case-control study was performed in 410 ischemic stroke (IS) patients and in 389 PSE patients. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The CD40 mRNA and protein levels were determined by real-time PCR and western blotting, respectively. The plasma sCD40L level was detected using an ELISA kit. The frequency of the T allele in PSE patients was significantly higher than in IS patients (P<0.05). The plasma sCD40L level was significantly higher in the PSE patients than in the healthy controls and IS patients (P<0.01, P<0.05, respectively). The peripheral blood mononuclear cells (PBMCs) from PSE patients showed significantly higher CD40 mRNA and protein expression than the healthy controls and IS patients (P<0.01, P<0.05, respectively). In the PSE patients, the T-allele carriers showed increased plasma sCD40L levels and increased CD40 mRNA expression. Our study suggested that the T allele of the CD40 -1C/T polymorphism may be associated with PSE susceptibility. The CD40/CD40L system is involved in the process of PSE.

Changes in gene expression in the frontal cortex of rats with pilocarpine-induced status epilepticus after sleep deprivation

Sleep and epilepsy present a bidirectional interaction. Sleep complaints are common in epilepsy, and sleep deprivation may provoke seizures. However, the mechanisms underlying this relationship are unknown. Thus, this study investigated the effects of paradoxical sleep deprivation (PSD24h) and total sleep deprivation (TSD6h) in the expression of genes related to reactive oxygen species and nitric oxide production in the frontal cortex of a rodent model of temporal lobe epilepsy (PILO). The data show that PILO rats had increased NOX-2 expression and decreased SOD expression, independent of sleep. Higher NOX-2 expression was observed only in PILO rats subjected to the control condition and TSD6h. Also, eNOS and DDAH1 were increased in the PILO group submitted to TSD6h. Moreover, CAT expression in the frontal cortex of PILO rats submitted to PSD24h was reduced compared to that of PILO rats that were not sleep-deprived. The molecular changes found in the frontal cortex of PILO rats following sleep deprivation suggest a mechanism via oxidative stress.

Brain stem oxidative stress and its associated signaling in the regulation of sympathetic vasomotor tone

There is now compelling evidence from studies in humans and animals that overexcitation of the sympathetic nervous system plays an important role in the pathogenesis of cardiovascular diseases. An excellent example is neurogenic hypertension, in which central sympathetic overactivation is involved in the development, staging, and progression of the disease, and one of the underlying mechanisms involves oxidative stress in key brain stem sites that are engaged in the regulation of sympathetic vasomotor tone. Using the rostral ventrolateral medulla (RVLM) and nucleus tractus solitarii (NTS) as two illustrative brain stem neural substrates, this article provides an overview of the impact of reactive oxygen species and antioxidants on RVLM and NTS in the pathogenesis of neurogenic hypertension. This is followed by a discussion of the redox-sensitive signaling pathways, including several kinases, ion channels, and transcription factors that underpin the augmentation in sympathetic vasomotor tone. In addition, the emerging view that brain stem oxidative stress is also causally related to a reduction in sympathetic vasomotor tone and hypotension during brain stem death, methamphetamine intoxication, and temporal lobe status epilepticus will be presented, along with the causal contribution of the oxidant peroxynitrite formed by a reaction between nitric oxide synthase II (NOS II)-derived nitric oxide and superoxide. Also discussed as a reasonable future research direction is dissection of the cellular mechanisms and signaling cascades that may underlie the contributory role of nitric oxide generated by different NOS isoforms in the differential effects of oxidative stress in the RVLM or NTS on sympathetic vasomotor tone.