Blood-brain barrier damage and brain penetration of antiepileptic drugs: role of serum proteins and brain edema

Challenges and prospects in geriatric epilepsy treatment: the role of the blood-brain barrier in pharmacotherapy and drug delivery

The blood-brain barrier (BBB) is pivotal in maintaining neuronal physiology within the brain. This review delves into the alterations of the BBB specifically in the context of geriatric epilepsy. We examine how age-related changes in the BBB contribute to the pathogenesis of epilepsy in the elderly and present significant challenges in pharmacotherapy. Subsequently, we evaluate recent advancements in drug delivery methods targeting the BBB, as well as alternative approaches that could bypass the BBB's restrictive nature. We particularly highlight the use of neurotropic viruses and various synthetic nanoparticles that have been investigated for delivering a range of antiepileptic drugs. Additionally, the advantage and limitation of these diverse delivery methods are discussed. Finally, we analyze the potential efficacy of different drug delivery approaches in the treatment of geriatric epilepsy, aiming to provide insights into more effective management of this condition in the elderly population.

Pluronic P85 decreases the delivery of phenytoin to the brain in drug-resistant rats with P-glycoprotein overexpressed chronic mesial temporal lobe epilepsy

P-glycoprotein (Pgp) overexpressed in blood brain barrier (BBB) is hypothesized to lower brain drug concentrations and thus inhibit anticonvulsant effects in drug-resistant epilepsy. Pluronic P85 (P85) was proved to enhance the delivery of drugs into the brain by inhibition of Pgp. To determine whether the surfactant P85 [versus Pgp inhibitor tariquidar (TQD)] enhance phenytoin (PHT) into the brain in drug-resistant rats with chronic mesial temporal lobe epilepsy (MTLE) induced by lithium-pilocarpine, in brain of which Pgp were overexpressed, then direct verification of PHT transport via measurement of PHT concentration in brain using microdialysis. The drug-resistant model rats were randomly divided into three groups, which were treated with PHT, 1%P85 + PHT, or PHT+TQD, respectively. 1%P85 + PHT treatment displayed a lower ratio of the area under the curve (AUC) of the PHT concentration in the brain/plasma even than that of the PHT treatment in model rats (p < 0.05), while PHT+TQD showed the highest ratio of the AUC of all treatments. However, the ratio of the PHT concentration in the liver/plasma was similar in three model groups (p > 0.05). For the ratio of the kidney/plasma, PHT+TQD treatment model group had the highest ratio of the other treatments in model rats. Thus, P85 oppositely decreased PHT concentration in brain in drug-resistant model rats with Pgp overexpressed MTLE while TQD could increase PHT distribution in brain.

Understanding Lamotrigine's Role in the CNS and Possible Future Evolution

The anti-epileptic drug lamotrigine (LTG) has been widely used to treat various neurological disorders, including epilepsy and bipolar disorder. However, its precise mechanism of action in the central nervous system (CNS) still needs to be determined. Recent studies have highlighted the involvement of LTG in modulating the activity of voltage-gated ion channels, particularly those related to the inhibition of neuronal excitability. Additionally, LTG has been found to have neuroprotective effects, potentially through the inhibition of glutamate release and the enhancement of GABAergic neurotransmission. LTG's unique mechanism of action compared to other anti-epileptic drugs has led to the investigation of its use in treating other CNS disorders, such as neuropathic pain, PTSD, and major depressive disorder. Furthermore, the drug has been combined with other anti-epileptic drugs and mood stabilizers, which may enhance its therapeutic effects. In conclusion, LTG's potential to modulate multiple neurotransmitters and ion channels in the CNS makes it a promising drug for treating various neurological disorders. As our understanding of its mechanism of action in the CNS continues to evolve, the potential for the drug to be used in new indications will also be explored.

Determination of brain water content by dry/wet weight measurement for the detection of experimental brain edema

Brain edema is a fatal pathological state in which brain volume increases as a result of abnormal accumulation of fluid within the brain parenchyma. A key attribute of experimentally induced brain edema - increased brain water content (BWC) - needs to be verified. Various methods are used for this purpose: specific gravimetric technique, electron microscopic examination, magnetic resonance imaging (MRI) and dry/wet weight measurement. In this study, the cohort of 40 rats was divided into one control group (CG) and four experimental groups with 8 rats in each group. The procedure for determining BWC using dry/wet weight measurement was initiated 24 h after the completion of edema induction by the water intoxication method (WI group); after the intraperitoneal administration of Methylprednisolone (MP) together with distilled water during edema induction (WI+MP group); 30 min after osmotic blood brain barrier disruption (BBBd group); after injection of MP via the internal carotid artery immediately after BBBd (BBBd + MP group). While induction of brain edema (WI, BBBd) resulted in significantly higher BWC, there was no increase in BWC in the MP groups (WI+MP, BBBd+MP), suggesting a neuroprotective effect of MP in the development of brain edema.

Membrane Vesicles Derived from Gut Microbiota and Probiotics: Cutting-Edge Therapeutic Approaches for Multidrug-Resistant Superbugs Linked to Neurological Anomalies

Multidrug-resistant (MDR) superbugs can breach the blood-brain barrier (BBB), leading to a continuous barrage of pro-inflammatory modulators and induction of severe infection-related pathologies, including meningitis and brain abscess. Both broad-spectrum or species-specific antibiotics (β-lactamase inhibitors, polymyxins, vancomycin, meropenem, plazomicin, and sarecycline) and biocompatible poly (lactic-co-glycolic acid) (PLGA) nanoparticles have been used to treat these infections. However, new therapeutic platforms with a broad impact that do not exert off-target deleterious effects are needed. Membrane vesicles or extracellular vesicles (EVs) are lipid bilayer-enclosed particles with therapeutic potential owing to their ability to circumvent BBB constraints. Bacteria-derived EVs (bEVs) from gut microbiota are efficient transporters that can penetrate the central nervous system. In fact, bEVs can be remodeled via surface modification and CRISPR/Cas editing and, thus, represent a novel platform for conferring protection against infections breaching the BBB. Here, we discuss the latest scientific research related to gut microbiota- and probiotic-derived bEVs, and their therapeutic modifications, in terms of regulating neurotransmitters and inhibiting quorum sensing, for the treatment of neurodegenerative diseases, such as Parkinson's and Alzheimer's diseases. We also emphasize the benefits of probiotic-derived bEVs to human health and propose a novel direction for the development of innovative heterologous expression systems to combat BBB-crossing pathogens.

A sensitive LC-MS/MS method for quantification of phenytoin and its major metabolite with application to in vivo investigations of intravenous and intranasal phenytoin delivery

Phenytoin is a powerful antiseizure drug with complex pharmacokinetic properties, making it an interesting model drug to use in preclinical in vivo investigations, especially with regards to formulations aiming to improve drug delivery to the brain. Moreover, it has a major metabolite, 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin, which can be simultaneously studied to achieve a better assessment of its behaviour in the body. Here, we describe the development and validation of a sensitive LCMS/MS method for quantification of phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain which can be used in such preclinical studies. Calibration curves produced covered a range of 7.81 to 250 ng/mL (plasma) and 23.4 to 750 ng/g (brain tissue) for both analytes. The method was validated for specificity, sensitivity, accuracy, and precision and found to be within the acceptable limits of ±15% over this range in both tissue types. The method when applied in two in vivo investigations: validation of a seizure model and to study the behaviour of a solution of intranasally administered phenytoin as a foundation for future studies into direct nose‐to‐brain delivery of phenytoin using specifically developed particulate systems, was highly sensitive for detecting phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain.

Microvascular stabilization via blood-brain barrier regulation prevents seizure activity

Blood-brain barrier (BBB) dysfunction is associated with worse epilepsy outcomes however the underlying molecular mechanisms of BBB dysfunction remain to be elucidated. Tight junction proteins are important regulators of BBB integrity and in particular, the tight junction protein claudin-5 is the most enriched in brain endothelial cells and regulates size-selectivity at the BBB. Additionally, disruption of claudin-5 expression has been implicated in numerous disorders including schizophrenia, depression and traumatic brain injury, yet its role in epilepsy has not been fully deciphered. Here we report that claudin-5 protein levels are significantly diminished in surgically resected brain tissue from patients with treatment-resistant epilepsy. Concomitantly, dynamic contrast-enhanced MRI in these patients showed widespread BBB disruption. We show that targeted disruption of claudin-5 in the hippocampus or genetic heterozygosity of claudin-5 in mice exacerbates kainic acid-induced seizures and BBB disruption. Additionally, inducible knockdown of claudin-5 in mice leads to spontaneous recurrent seizures, severe neuroinflammation, and mortality. Finally, we identify that RepSox, a regulator of claudin-5 expression, can prevent seizure activity in experimental epilepsy. Altogether, we propose that BBB stabilizing drugs could represent a new generation of agents to prevent seizure activity in epilepsy patients.

The mechanisms underlying epilepsy development are not well understood. Here the authors show that loss of a key component of the so called blood-brain barrier drives seizures in mice and is also lost in humans with treatment resistant epilepsy

Beta-caryophyllene attenuates short-term recurrent seizure activity and blood-brain-barrier breakdown after pilocarpine-induced status epilepticus in rats

BACKGROUND

Status epilepticus (SE) is a neurological life-threatening condition, resulting from the failure of the mechanisms responsible for seizure termination. SE is often pharmacoresistant and associated with significant morbidity and mortality. Hence, ceasing or attenuating SE and its consequences is of fundamental importance. Beta-caryophyllene is a functional CB2 receptor agonist and exhibit a good safety profile. Besides, it displays beneficial effects in several experimental conditions, including neuroprotective activity. In the present study we aimed to investigate the effects of beta-caryophyllene on pilocarpine-induced SE.

METHODS

Wistar rats were submitted to pilocarpine-induced SE and monitored for 24 hours by video and EEG for short-term recurrence of seizure activity (i.e. seizures occurring within 24 hours after termination of SE). Rats received beta-caryophyllene (100 mg/kg, ip) at 1, 8- and 16-hours after SE. Twenty-four hours after SE we evaluated sensorimotor response, neuronal damage (fluoro jade C staining) and serum albumin infiltration into brain parenchyma.

RESULTS

Beta-caryophyllene-treated animals presented fewer short-term recurrent seizures than vehicle-treated counterparts, suggesting an anticonvulsant effect after SE. Behavioral recovery from SE and the number of fluoro jade C positive cells in the hippocampus and thalamus were not modified by beta-caryophyllene. Treatment with beta-caryophyllene attenuated the SE-induced increase of albumin immunoreactivity in the hippocampus, indicating a protective effect against blood-brain-barrier breakdown.

CONCLUSIONS

Given the inherent difficulties in the treatment of SE and its consequences, present results suggest that beta-caryophyllene deserve further investigation as an adjuvant therapeutic strategy for SE.

Detection of Label-Free Drugs within Brain Tissue Using Orbitrap Secondary Ion Mass Spectrometry as a Complement to Neuro-Oncological Drug Delivery

Historically, pre-clinical neuro-oncological drug delivery studies have exhaustively relied upon overall animal survival as an exclusive measure of efficacy. However, with no adopted methodology to both image and quantitate brain parenchyma penetration of label-free drugs, an absence of efficacy typically hampers clinical translational potential, rather than encourage re-formulation of drug compounds using nanocarriers to achieve greater tissue penetration. OrbiSIMS, a next-generation analytical instrument for label-free imaging, combines the high resolving power of an OrbiTrapTM mass spectrometer with the relatively high spatial resolution of secondary ion mass spectrometry. Here, we develop an ex vivo pipeline using OrbiSIMS to accurately detect brain penetration of drug compounds. Secondary ion spectra were acquired for a panel of drugs (etoposide, olaparib, gemcitabine, vorinostat and dasatinib) under preclinical consideration for the treatment of isocitrate dehydrogenase-1 wild-type glioblastoma. Each drug demonstrated diagnostic secondary ions (all present molecular ions [M-H]− which could be discriminated from brain analytes when spiked at >20 µg/mg tissue. Olaparib/dasatinib and olaparib/etoposide dual combinations are shown as exemplars for the capability of OrbiSIMS to discriminate distinct drug ions simultaneously. Furthermore, we demonstrate the imaging capability of OrbiSIMS to simultaneously illustrate label-free drug location and brain chemistry. Our work encourages the neuro-oncology community to consider mass spectrometry imaging modalities to complement in vivo efficacy studies, as an analytical tool to assess brain distribution of systemically administered drugs, or localised brain penetration of drugs released from micro- or nano-scale biomaterials.

Visualization of blood-brain barrier disruption with dual-wavelength high-resolution photoacoustic microscopy

The blood-brain barrier (BBB) strictly regulates the substance exchange between the vascular network and the central nervous system, and plays a critical role in maintaining normal brain homeostasis. Impaired BBB is often accompanied with the emergence of cerebral diseases and probably further leads to severe neuroinflammation or even neurological degeneration. Hence, there is an urgent need to precisely monitor the impaired BBB to understand its pathogenesis and better guide the enactment of therapeutic strategies. However, there is a lack of high-resolution imaging techniques to visualize and evaluate the large-scale BBB disruption in pre-clinical and clinical aspects. In this study, we propose a dual-wavelength photoacoustic imaging (PAI) methodology that simultaneously reveals the abnormal microvasculature and impaired BBB within the cerebral cortex. In in vivo studies, BBB disruption in both mice and rats were induced by local hot-water stimulation and unilateral carotid arterial perfusion of hyperosmolar mannitol, respectively. Subsequently, the exogenous contrast agent (CA) was injected into the microcirculation via the tail vein, and photoacoustic (PA) images of the microvasculature and leaked CA within the cerebral cortex were obtained by dual-wavelength photoacoustic microscopy to evaluate the BBB disruption. Besides, analysis of distribution and concentration of leaked CA in lesion region was further conducted to quantitatively reveal the dynamic changes of BBB permeability. Furthermore, we exploited this approach to investigate the reversibility of BBB disruption within the two distinct models. Based on the experimental results, this new proposed approach presents excellent performance in visualizing microvasculature and leaked CA, and enabling it possesses great potential in evaluating the abnormal microvasculature and impaired BBB result from cerebrovascular diseases.

Cortical Dysplasia in Rats Provokes Neurovascular Alterations, GLUT1 Dysfunction, and Metabolic Disturbances That Are Sustained Post-Seizure Induction

Focal cortical dysplasia (FCD) is associated with blood-brain barrier (BBB) dysfunction in patients with difficult-to-treat epilepsy. However, the underlying cellular and molecular factors in cortical dysplasia (CD) associated with progressive neurovascular challenges during the pro-epileptic phase, post-seizure, and during epileptogenesis remain unclear. We studied the BBB function in a rat model of congenital (in utero radiation-induced, first hit) CD and longitudinally examined the cortical brain tissues at baseline and the progressive neurovascular alterations, glucose transporter-1 (GLUT1) expression, and glucose metabolic activity at 2, 15, and 30 days following a second hit using pentylenetetrazole-induced seizure. Our study revealed through immunoblotting, immunohistochemistry, and biochemical analysis that (1) altered vascular density and prolongation of BBB albumin leakages in CD rats continued through 30 days post-seizure; (2) CD brain tissues showed elevated matrix metalloproteinase-9 levels at 2 days post-seizure and microglial overactivation through 30 days post-seizure; (3) BBB tight junction protein and GLUT1 levels were decreased and neuronal monocarboxylate transporter-2 (MCT2) and mammalian target of rapamycin (mTOR) levels were increased in the CD rat brain: (4) ATPase activity is elevated and a low glucose/high lactate imbalance exists in CD rats; and (5) the mTOR pathway is activated and MCT2 levels are elevated in the presence of high lactate during glucose starvation in vitro. Together, this study suggests that BBB dysfunction, including decreased GLUT1 expression and metabolic disturbance, may contribute to epileptogenesis in this CD rat model through multiple mechanisms that could be translated to FCD therapy in medically refractory epilepsy.

Effect of methylprednisolone on experimental brain edema in rats - own experience reviewed

Brain edema - a frequently fatal pathological state in which brain volume increases resulting in intracranial pressure elevation - can result from almost any insult to the brain, including traumatic brain injury. For many years, the objective of experimental studies was to find a method to prevent the development of brain edema at the onset. From this perspective, the use of methylprednisolone (MP) appears promising. High molecular MP (MW>50 kDa) can be incorporated into the brain - in the conditions of the experimental model - either by osmotic blood-brain barrier disruption (BBBd) or during the induction of cellular edema by water intoxication (WI) - a condition that increases the BBB permeability. The time window for administration of the MP should be at the earliest stages of edema. The neuroprotective effect of MP on the permeability of cytoplasmatic membranes of neuronal populations was proved. MP was administrated in three alternative ways: intraperitoneally during the induction of cytotoxic edema or immediately after finishing cytotoxic edema induction in a dose of 100 mg/kg b.w.; into the internal carotid artery within 2 h after finishing cytotoxic edema induction in a dose of 50 mg/kg b.w.; into internal carotid artery 10 min after edema induction by BBBd in a dose of 50 mg/kg b.w.

Drug Delivery Challenges in Brain Disorders across the Blood-Brain Barrier: Novel Methods and Future Considerations for Improved Therapy

Due to the physiological and structural properties of the blood-brain barrier (BBB), the delivery of drugs to the brain poses a unique challenge in patients with central nervous system (CNS) disorders. Several strategies have been investigated to circumvent the barrier for CNS therapeutics such as in epilepsy, stroke, brain cancer and traumatic brain injury. In this review, we summarize current and novel routes of drug interventions, discuss pharmacokinetics and pharmacodynamics at the neurovascular interface, and propose additional factors that may influence drug delivery. At present, both technological and mechanistic tools are devised to assist in overcoming the BBB for more efficient and improved drug bioavailability in the treatment of clinically devastating brain disorders.

Potentially Detrimental Effects of Hyperosmolality in Patients Treated for Traumatic Brain Injury

Hyperosmotic therapy is commonly used to treat intracranial hypertension in traumatic brain injury patients. Unfortunately, hyperosmolality also affects other organs. An increase in plasma osmolality may impair kidney, cardiac, and immune function, and increase blood-brain barrier permeability. These effects are related not only to the type of hyperosmotic agents, but also to the level of hyperosmolality. The commonly recommended osmolality of 320 mOsm/kg H2O seems to be the maximum level, although an increase in plasma osmolality above 310 mOsm/kg H2O may already induce cardiac and immune system disorders. The present review focuses on the adverse effects of hyperosmolality on the function of various organs.

Attenuation of cerebral edema facilitates recovery of glymphatic system function after status epilepticus

Status epilepticus (SE) is a neurological emergency usually accompanied by acute cerebral edema and long-term cognitive impairment, and is characterized by neurodegeneration and aberrant hyperphosphorylated tau protein (p-tau) aggregation. The glia-lymphatic (glymphatic) system plays a central role in facilitating the clearance of metabolic waste from the brain, but its relationship with cerebral edema and cognitive dysfunction after SE is unclear. We hypothesized that cerebral edema after SE might impair glymphatic system function through compression, thus leading to impaired removal of metabolic waste, and ultimately affecting long-term cognitive function. Our results showed that glymphatic system function was temporarily impaired, as evidenced by 2-photon imaging, MRI enhancement, imaging of brain sections, and astrocytic water channel aquaporin 4 (AQP4) protein polarization. The severity of cerebral edema on MRI correlated well with glymphatic system dysfunction within 8 days following SE. Moreover, when cerebral edema was alleviated by glibenclamide treatment or genetic deletion of Trpm4, post-SE glymphatic system function recovered earlier, along with fewer p-tau–deposited neurons and neuronal degeneration and better cognitive function. These findings suggest that SE-induced cerebral edema may cause glymphatic system dysfunction and render the post-SE brain vulnerable to p-tau aggregation and neurocognitive impairment.

Contrast-Free Detection of Focused Ultrasound-Induced Blood-Brain Barrier Opening Using Diffusion Tensor Imaging

OBJECTIVE

Focused ultrasound (FUS) has emerged as a non-invasive technique to locally and reversibly disrupt the blood-brain barrier (BBB). Here, we investigate the use of diffusion tensor imaging (DTI) as a means of detecting FUS-induced BBB opening at the absence of an MRI contrast agent. A non-human primate (NHP) was repeatedly treated with FUS and preformed circulating microbubbles to transiently disrupt the BBB (n = 4). T1- and diffusion-weighted MRI scans were acquired after the ultrasound treatment, with and without gadolinium-based contrast agent, respectively. Both scans were registered with a high-resolution T1-weighted scan of the NHP to investigate signal correlations. DTI detected an increase in fractional anisotropy from 0.21 ± 0.02 to 0.38 ± 0.03 (82.6 ± 5.2% change) within the targeted area one hour after BBB opening. Enhanced DTI contrast overlapped by 77.22 ± 9.2% with hyper-intense areas of gadolinium-enhanced T1-weighted scans, indicating diffusion anisotropy enhancement only within the BBB opening volume. Diffusion was highly anisotropic and unidirectional within the treated brain region, as indicated by the direction of the principal diffusion eigenvectors. Polar and azimuthal angle ranges decreased by 35.6% and 82.4%, respectively, following BBB opening. Evaluation of the detection methodology on a second NHP (n = 1) confirmed the across-animal feasibility of the technique. In conclusion, DTI may be used as a contrast-free MR imaging modality in lieu of contrast-enhanced T1 mapping for detecting BBB opening during focused-ultrasound treatment or evaluating BBB integrity in brain-related pathologies.

Aneurysmal Subarachnoid Hemorrhage: Impact on Phenytoin Permeability across the Blood-Brain Barrier

Background

Phenytoin (PHT) is a routinely prescribed prophylactic antiepileptic following aneurysmal subarachnoid hemorrhage (aSAH). However, its prophylactic use in aSAH is controversial as emerging evidence suggests worsening of the neurological and functional outcomes. In addition, there is profound damage to the blood-brain barrier (BBB) in aSAH, posing uncertainty about the permeability of PHT across BBB in these patients. This pilot study was designed to evaluate the alteration in PHT permeability across BBB in aSAH patients.

Materials and Methods

For conducting the study, 20 patients (control n = 10; aSAH (grade 3 or 4) n = 10) were recruited from a tertiary care hospital. The patients undergoing cranial surgery for pathology with intracerebral mass lesions on MRI were chosen as control for aSAH group. Both groups were administered PHT loading dose (20 mg/kg), infused in 5% dextrose, at a rate not more than 50 mg/min, followed by a maintenance dose (5 mg/kg). Quantification of PHT concentration was performed in brain tissue, plasma, and cerebrospinal fluid (CSF) by LC-MS/MS.

Results

The median PHT concentration in brain was found to be significantly decreased (64.8%) in aSAH group (3.78 μg/g) as compared to control (10.73 μg/g), P = 0.010. Similarly, median PHT brain concentration as fraction of plasma was significantly decreased in aSAH group (36.72%) compared to that of control (89.55%), P = 0.003. There was no significant difference in PHT concentration in plasma, CSF, and CSF as a fraction of plasma between both the groups.

Conclusion

There is a definite decrease in the penetration of PHT to the brain in patients with grade 3 and 4 aSAH.

In vitro Models of the Blood-Brain Barrier: Tools in Translational Medicine

Medical progress has historically depended on scientific discoveries. Until recently, science was driven by technological advancements that, once translated to the clinic, fostered new treatments and interventions. More recently, technology-driven medical progress has often outpaced laboratory research. For example, intravascular devices, pacemakers for the heart and brain, spinal cord stimulators, and surgical robots are used routinely to treat a variety of diseases. The rapid expansion of science into ever more advanced molecular and genetic mechanisms of disease has often distanced laboratory-based research from day-to-day clinical realities that remain based on evidence and outcomes. A recognized reason for this hiatus is the lack of laboratory tools that recapitulate the clinical reality faced by physicians and surgeons. To overcome this, the NIH and FDA have in the recent past joined forces to support the development of a "human-on-a-chip" that will allow research scientists to perform experiments on a realistic replica when testing the effectiveness of novel experimental therapies. The development of a "human-on-a-chip" rests on the capacity to grow in vitro various organs-on-a-chip, connected with appropriate vascular supplies and nerves, and our ability to measure and perform experiments on these virtually invisible organs. One of the tissue structures to be scaled down on a chip is the human blood-brain barrier. This review gives a historical perspective on in vitro models of the BBB and summarizes the most recent 3D models that attempt to fill the gap between research modeling and patient care. We also present a summary of how these in vitro models of the BBB can be applied to study human brain diseases and their treatments. We have chosen NeuroAIDS, COVID-19, multiple sclerosis, and Alzheimer's disease as examples of in vitro model application to neurological disorders. Major insight pertaining to these illnesses as a consequence of more profound understanding of the BBB can reveal new avenues for the development of diagnostics, more efficient therapies, and definitive clarity of disease etiology and pathological progression.

Lorazepam timing for acute convulsive seizure control (LoTASC)

INTRODUCTION

Guidelines specify early administration of benzodiazepines (BZD) for the management of convulsive status epilepticus. The distinction between acute convulsive seizure and status epilepticus can be misconstrued resulting in BZD administration prior to a patient meeting criteria of status epilepticus. Early BZD administration may theoretically lead to systemic vital instability. Our study aims to assess if administering lorazepam, for convulsive seizures <5 min, causes vital instability.

METHODS

This is a retrospective study analyzing patients who presented with a seizure lasting <5 min between 2011 and 2016. Continuous variables of lorazepam receivers versus non- receivers were analyzed using t-test for parametric and Mann-Whitney U test for nonparametric data. Categorical variables were analyzed using Chi-Square Test. Subsequently, subjects were analyzed through univariate and multivariate regression models to determine predictors of vital instability.

RESULTS

Out of 1052 subjects initially screened, 165 were included. Of these, 91 (55 %) received lorazepam, and 74 (45 %) did not. Through univariate and multivariate analyses, there was a significantly higher incidence of vital instability (defined as receipt of a vasopressor or intubation) in patients who received lorazepam (OR = 6.76, 95 % CI = 1.48, 30.95) (p = 0.014). This was dose-dependent (p < 0.0001). It was responsible for 22.5 % of the vital instability. Lorazepam administration significantly prolonged the intensive care unit (ICU) length of stay (0 days [IQR 0 - 0] vs [IQR 0-2.3]; p = 0.038).

CONCLUSION

Our study suggests that lorazepam administration for acute convulsive seizures not meeting convulsive status epilepticus criteria may lead to iatrogenic vital instability and need for ICU admission.

Increase in cognitive function is seen in many single-operated pediatric patients after epilepsy surgery

PURPOSE

The recurrent seizures of pediatric drug-resistant epilepsy (DRE) are known to impair brain development and can lead to a loss in cognitive functioning. Surgery is increasingly being used to treat children with DRE. This study investigates the pre- and postoperative cognitive function in a pediatric epilepsy surgery cohort as well as predictive determinants of change in intelligence quotient (IQ) following surgery.

METHODS

A consecutive series of 91 Danish children who underwent focal resective epilepsy surgery between January 1996 and December 2016 were included. All underwent preoperative cognitive evaluation and were reevaluated at 1-year and/or 2-year follow-up. Single-operated and multi-operated patients were examined separately.

RESULTS

79 of 91 patients were single-operated. Single-operated patients received less anti-epileptic drugs (AED) and experienced a decrease in seizure frequency postoperatively, p < 0.001. IQ increased postoperatively (IQ change ± standard deviation: 3.3 ± 14.0), p < 0.05. High preoperative seizure frequency was a significant predictor for decreased IQ, p < 0.01. Multi-operated patients did not experience a reduction in AED treatment. Surgery and continued AED treatment did, however, result in significantly better seizure control, p < 0.01. IQ remained unchanged in multi-operated patients.

CONCLUSION

Epilepsy surgery allowed for IQ gains in single-operated patients. Preoperative seizure frequency was a significant predictor of IQ change following surgery. Interactions between other, not included, possible predictors remain to be examined. Single-operated patients had the best cognitive outcome. The inclusion of a non-surgical control group is needed to assess the extent of the beneficial effects of surgery on cognitive ability.

Advances in drug delivery technology for the treatment of glioblastoma multiforme

Glioblastoma multiforme (GBM) is a particularly aggressive and malignant type of brain tumor, notorious for its high recurrence rate and low survival rate. The treatment of GBM is challenging mainly because several issues associated with the GBM microenvironment have not yet been resolved. These obstacles originate from a variety of factors such as genetics, anatomy, and cytology, all of which collectively hinder the treatment of GBM. Recent advances in materials and device engineering have presented new perspectives with regard to unconventional drug administration methods for GBM treatment. Such novel drug delivery approaches, based on the clear understanding of the intrinsic properties of GBM, have shown promise in overcoming some of the obstacles. In this review, we first recapitulate the first-line therapy and clinical challenges in the current treatment of GBM. Afterwards, we introduce the latest technological advances in drug delivery strategies to improve the efficiency for GBM treatment, mainly focusing on materials and devices. We describe such efforts by classifying them into two categories, systemic and local drug delivery. Finally, we discuss unmet challenges and prospects for the clinical translation of these drug delivery technologies.

Heat Shock Proteins Accelerate the Maturation of Brain Endothelial Cell Glucocorticoid Receptor in Focal Human Drug-Resistant Epilepsy

Pharmacoresistance in epilepsy is a major challenge to successful clinical therapy. Glucocorticoid receptor (GR) dysregulation can affect the underlying disease pathogenesis. We recently reported that local drug biotransformation at the blood-brain barrier is upregulated by GR, which controls drug-metabolizing enzymes (e.g., cytochrome P450s, CYPs) and efflux drug transporters (MDR1) in human epileptic brain endothelial cells (EPI-ECs). Here, we establish that this mechanism is influenced upstream by GR and its association with heat shock proteins/co-chaperones (Hsps) during maturation, which differentially affect human epileptic (EPI) tissue and brain endothelial cells. Overexpressed GR, Hsp90, Hsp70, and Hsp40 were found in EPI vs. NON-EPI brain regions. Elevated neurovascular GR expression and co-localization with Hsps was evident in the EPI regions with cortical dysplasia, predominantly in the brain micro-capillaries and neurons. A corresponding increase in ATPase activity (*p < 0.05) was found in the EPI regions. The GR-Hsp90/Hsp70 binding patterns indicated a faster chaperone-promoted maturation of GR, leading to its overactivation in both the tissue and EPI-ECs derived from EPI/focal regions and GR silencing in EPI-ECs slowed such GR-Hsp interactions. Significantly accelerated GR nuclear translocation was determined in EPI-ECs following treatment with GR modulators/ligands dexamethasone, rifampicin, or phenytoin. Our findings reveal that overexpressed GR co-localizes with Hsps in the neurovasculature of EPI brain, increased GR maturation by Hsps accelerates EPI GR machinery, and furthermore this change in EPI and NON-EPI GR-Hsp interaction alters with the age of seizure onset in epileptic patients, together affecting the pathophysiology and drug regulation in the epileptic brain endothelium.

The 3D Brain Unit Network Model to Study Spatial Brain Drug Exposure under Healthy and Pathological Conditions

PURPOSE

We have developed a 3D brain unit network model to understand the spatial-temporal distribution of a drug within the brain under different (normal and disease) conditions. Our main aim is to study the impact of disease-induced changes in drug transport processes on spatial drug distribution within the brain extracellular fluid (ECF).

METHODS

The 3D brain unit network consists of multiple connected single 3D brain units in which the brain capillaries surround the brain ECF. The model includes the distribution of unbound drug within blood plasma, coupled with the distribution of drug within brain ECF and incorporates brain capillaryblood flow, passive paracellular and transcellular BBB transport, active BBB transport, brain ECF diffusion, brain ECF bulk flow, and specific and nonspecific brain tissue binding. All of these processes may change under disease conditions.

RESULTS

We show that the simulated disease-induced changes in brain tissue characteristics significantly affect drug concentrations within the brain ECF.

CONCLUSIONS

We demonstrate that the 3D brain unit network model is an excellent tool to gain understanding in the interdependencies of the factors governing spatial-temporal drug concentrations within the brain ECF. Additionally, the model helps in predicting the spatial-temporal brain ECF concentrations of existing drugs, under both normal and disease conditions.

Shedding light on human cerebral lipofuscin: An explorative study on identification and quantification

Increased oxidative stress has been associated with several neurodegenerative diseases such as Alzheimer's disease, but also with neurological diseases sharing pathophysiological pathways like epilepsy. Lipofuscin is a nondegradable end-product of oxidative stress; its cerebral presence reflects the cumulative amount of oxidative stress the brain has endured. In this study, we have observed prominent autofluorescent particles in the pial arterial wall and in neocortical parenchyma of young, drug-resistant epilepsy patients (18-28 years old) who underwent resective brain surgery (n = 6), as well as in older control patients (n = 3). With fluorescence spectroscopic imaging, brightfield microscopy, histochemistry and fluorescence lifetime imaging, these autofluorescent particles were identified as the age pigment lipofuscin. An evaluation of these lipofuscin particles using Imaris© software allowed robust quantification, while the 3D properties allowed visualization of the complex configuration. We elaborate on the usefulness of lipofuscin as a marker of cumulative oxidative stress in the brain. Furthermore, we speculate on the observed differences in particle size and density that we found between young patients and older controls, which could imply a role for lipofuscin in the pathophysiology of epilepsy and possibly other neurological diseases.

Teicoplanin-Modified HPLC Column as a Source of Experimental Parameters for Prediction of the Anticonvulsant Activity of 1,2,4-Triazole-3-Thiones by the Regression Models

The cell membrane is a complex system that consists of lipids, proteins, polysaccharides, and amphiphilic phospholipids. It plays an important role in ADME processes that are responsible for the final pharmaceutical effects of xenobiotics (bioavailability, activity). To study drug-membrane interaction at the molecular level, several high-performance liquid chromatography (HPLC) membrane model systems have been proposed which are mimicking mainly its lipid character. The aim of this work was to study interactions of new synthesized antiepileptic compounds of 4-alkyl-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione derivatives with Chirobiotic column containing glycoprotein ligand attached to the silica matrix. The affinity of the analytes to immobilized glycoprotein ligand was examined chromatographically in reversed-phase mode. The thermodynamics of interactions between bioactive compounds and teicoplanin was studied in terms of the van't Hoff linear relationship ln k vs. 1/T in the range of 5-45 °C. Change in enthalpy (ΔH°), change in entropy (ΔS°) and change in Gibbs free energy (ΔG°) were estimated utilizing graphical extrapolation and interpolation methods. The density functional theory (DFT) approach and docking simulations were used to get the molecular interpretation and prove the obtained experimental results. Cross-correlations of chromatographic and thermodynamic parameters with non-empirical topological and quantum chemical indices suggest that the polarizability of analytes appears to be responsible for the interactions of the tested molecules with teicoplanin and, ultimately, their retention on the column. Experimental and theoretical parameters were subjected to statistical analysis using regression models. Partial least squares (PLS) regression model showed the usefulness of the experimentally measured parameter φ0 (MeOH) to discriminate between anticonvulsant active and inactive 1,2,4-triazole-3-thione derivatives. Obtained results point out the usefulness of interaction of potential anticonvulsants with glycoprotein class of compounds to anticipate their activity.

Vascular Abnormalities and the Role of Vascular Endothelial Growth Factor in the Epileptic Brain

Epilepsy is a chronic neurological disorder generally defined to be caused by excessive neuronal activity. Thus, excessive neuronal activity is the main target of the currently used antiepileptic drugs (AEDs). However, as many as 30% of epileptic patients show drug resistance to currently available AEDs, which suggests that epilepsy should be attributed not only to neuronal cells but also to other brain cells, such as glial cells and vascular cells. Astrocytes, pericytes, and endothelial cells in particular comprise the blood–brain barrier (BBB), which tightly regulates the exchange of substances between the brain parenchyma and the circulating blood. It has been proposed that BBB dysfunction, especially barrier leakage, exacerbates epileptic progression, and conversely, that epileptic seizures induce barrier leakage. Furthermore, several studies have shown that BBB dysfunction is one of the main causes of drug resistance in epilepsy. To better understand the mechanisms that link BBB dysfunction and intractable epilepsy to gain insights for the future development of treatments, we review and discuss the relationships between epilepsy and brain vascular abnormalities, mainly by focusing on vascular malformation, BBB dysfunction, and excessive angiogenesis. Because these abnormalities have been reported to be caused by vascular endothelial growth factor (VEGF) in the ischemic brain, we discuss the possible role of VEGF in vascular abnormalities in the epileptic brain, in which the upregulation of VEGF levels has been reported. Both glial cells and endothelial cells express VEGF receptors (VEGFRs); thus, these cells are likely affected by increases in VEGF during seizures, which in turn could cause vascular abnormalities. In this review, we review the possible role of VEGF in epilepsy and discuss the mechanisms that link vascular abnormalities and intractable epilepsy.

Structural, Molecular, and Functional Alterations of the Blood-Brain Barrier during Epileptogenesis and Epilepsy: A Cause, Consequence, or Both?

The blood-brain barrier (BBB) is a dynamic, highly selective barrier primarily formed by endothelial cells connected by tight junctions that separate the circulating blood from the brain extracellular fluid. The endothelial cells lining the brain microvessels are under the inductive influence of neighboring cell types, including astrocytes and pericytes. In addition to the anatomical characteristics of the BBB, various specific transport systems, enzymes and receptors regulate molecular and cellular traffic across the BBB. While the intact BBB prevents many macromolecules and immune cells from entering the brain, following epileptogenic brain insults the BBB changes its properties. Among BBB alterations, albumin extravasation and diapedesis of leucocytes from blood into brain parenchyma occur, inducing or contributing to epileptogenesis. Furthermore, seizures themselves may modulate BBB functions, permitting albumin extravasation, leading to activation of astrocytes and the innate immune system, and eventually modifications of neuronal networks. BBB alterations following seizures are not necessarily associated with enhanced drug penetration into the brain. Increased expression of multidrug efflux transporters such as P-glycoprotein likely act as a 'second line defense' mechanism to protect the brain from toxins. A better understanding of the complex alterations in BBB structure and function following seizures and in epilepsy may lead to novel therapeutic interventions allowing the prevention and treatment of epilepsy as well as other detrimental neuro-psychiatric sequelae of brain injury.

Preparation and characterisation of PHT-loaded chitosan lecithin nanoparticles for intranasal drug delivery to the brain

The use of nanoparticles (NPs) for intranasal (IN) drug delivery to the brain represents a hopeful strategy to enhance brain targeting of anti-epileptic drugs.

Epilepsy and Alterations of the Blood-Brain Barrier: Cause or Consequence of Epileptic Seizures or Both?

The blood-brain barrier (BBB) is a dynamic, highly selective barrier primarily formed by endothelial cells connected by tight junctions that separate the circulating blood from the brain extracellular fluid, thereby preserving a narrow and stable homeostatic control of the neuronal environment. The endothelial cells lining the brain microvessels are under the inductive influence of neighboring cell types within the "neurovascular unit" including astrocytes and pericytes. In addition to the morphological characteristics of the BBB, various specific transport systems, enzymes, and receptors regulate the molecular and cellular traffic across the barrier. Furthermore, the intact BBB prevents many macromolecules and immune cells from entering the brain. This changes dramatically following epileptogenic brain insults; such insults, among other BBB alterations, lead to albumin extravasation and diapedesis of leukocytes from blood into brain parenchyma, inducing or contributing to epileptogenesis, which finally leads to development of spontaneous recurrent seizures and epilepsy. Furthermore, seizures themselves may cause BBB disruption with albumin extravasation, which has been shown to be associated with activation of astrocytes, activation of innate immune systems, and modifications of neuronal networks. However, seizure-induced BBB disruption is not necessarily associated with enhanced drug penetration into the brain, because the BBB expression of multidrug efflux transporters such as P-glycoprotein increases, most likely as a "second line defense" mechanism to protect the brain from drug toxicity. Hopefully, a better understanding of the complex BBB alterations in response to seizures and epilepsy can lead to novel therapeutic intervention to prevent epileptogenesis and the development of other detrimental sequelae of brain injury.

Neurovascular Drug Biotransformation Machinery in Focal Human Epilepsies: Brain CYP3A4 Correlates with Seizure Frequency and Antiepileptic Drug Therapy

Pharmacoresistance is a major clinical challenge for approximately 30% of patients with epilepsy. Previous studies indicate nuclear receptors (NRs), drug efflux transporters, and cytochrome P450 enzymes (CYPs) control drug passage across the blood-brain barrier (BBB) in drug-resistant epilepsy. Here, we (1) evaluate BBB changes, neurovascular nuclear receptors, and drug transporters in lesional/epileptic (EPI) and non-lesional/non-epileptic (NON-EPI) regions of the same brain, (2) examine regional CYP expression and activity, and (3) investigate the association among CYP brain expression, seizure frequency, duration of epilepsy, and antiepileptic drug (AED) combination. We used surgically resected brain specimens from patients with medically intractable epilepsy (n = 22) where the epileptogenic loci were well-characterized by invasive and non-invasive methods; histology confirmed distinction of small NON-EPI regions from EPI tissues. NRs, transporters, CYPs, and tight-junction proteins were assessed by western blots/immunohistochemistry, and CYP metabolic activity was determined and compared. The relationship of CYP expression with seizure frequency, duration of epilepsy, and prescribed AEDs was evaluated. Decreased BBB tight-junction proteins accompanied IgG leakage in EPI regions and correlated with upregulated NR and efflux transporter levels. CYP expression and activity significantly increased in EPI compared to NON-EPI tissues. Change in EPI and NON-EPI CYP3A4 expression increased in patients taking AEDs that were CYP substrates, was downregulated when CYP- and non-CYP-substrate AEDs were given together, and correlated with seizure frequency. Our studies suggest focal neurovascular CYP-NR-transporter alterations, as demonstrated by the relationship of seizure frequency and AED combination to brain CYP3A4, might together impact biotransformation machinery of human pharmacoresistant epilepsy.

Central nervous system lymphatic unit, immunity, and epilepsy: Is there a link?

The recent definition of a network of lymphatic vessels in the meninges surrounding the brain and the spinal cord has advanced our knowledge on the functional anatomy of fluid movement within the central nervous system (CNS). Meningeal lymphatic vessels along dural sinuses and main nerves contribute to cerebrospinal fluid (CSF) drainage, integrating the cerebrovascular and periventricular routes, and forming a circuit that we here define as the CNS-lymphatic unit. The latter unit is important for parenchymal waste clearance, brain homeostasis, and the regulation of immune or inflammatory processes within the brain. Disruption of fluid drain mechanisms may promote or sustain CNS disease, conceivably applicable to epilepsy where extracellular accumulation of macromolecules and metabolic by-products occur in the interstitial and perivascular spaces. Herein we address an emerging concept and propose a theoretical framework on: (a) how a defect of brain clearance of macromolecules could favor neuronal hyperexcitability and seizures, and (b) whether meningeal lymphatic vessel dysfunction contributes to the neuroimmune cross-talk in epileptic pathophysiology. We propose possible molecular interventions targeting meningeal lymphatic dysfunctions, a potential target for immune-mediated epilepsy.

Improving the Prediction of Local Drug Distribution Profiles in the Brain with a New 2D Mathematical Model

The development of drugs that target the brain is very challenging. A quantitative understanding is needed of the complex processes that govern the concentration–time profile of a drug (pharmacokinetics) within the brain. So far, there are no studies on predicting the drug concentration within the brain that focus not only on the transport of drugs to the brain through the blood–brain barrier (BBB), but also on drug transport and binding within the brain. Here, we develop a new model for a 2D square brain tissue unit, consisting of brain extracellular fluid (ECF) that is surrounded by the brain capillaries. We describe the change in free drug concentration within the brain ECF, by a partial differential equation (PDE). To include drug binding, we couple this PDE to two ordinary differential equations that describe the concentration–time profile of drug bound to specific as well as non-specific binding sites that we assume to be evenly distributed over the brain ECF. The model boundary conditions reflect how free drug enters and leaves the brain ECF by passing the BBB, located at the level of the brain capillaries. We study the influence of parameter values for BBB permeability, brain ECF bulk flow, drug diffusion through the brain ECF and drug binding kinetics, on the concentration–time profiles of free and bound drug.

Blood-brain barrier (BBB) and the complement landscape

The brain is an immune privileged organ, uniquely placed in the body. Two systems involved in maintaining brain homeostasis and in protecting the brain are the blood-brain barrier (BBB) and the complement system. The BBB is present in the vasculature of the brain and is the dynamic interface between brain and body that regulates what enters and leaves the brain, thereby maintaining the brain microenvironment optimal for brain function. The complement system is ubiquitous, being present systemically and in the brain, both membrane bound and in circulation. It is an important arm of the body's defense that helps maintain homeostasis by eliminating debris and damaged cells, participating in destroying pathogens, promoting inflammation and conveying 'danger signals'. Recent studies reveal that the complement system plays an important role in normal brain development. However, when the complement system is overwhelmed, complement activation could contribute to loss of BBB integrity resulting in brain pathology. Studies support an association between complement proteins and BBB dysfunction, with the mechanisms being slowly unraveled. This review will provide an overview of both these systems, how they intersect and interact with each other.

Real-time monitoring of human blood-brain barrier disruption

Chemotherapy aided by opening of the blood-brain barrier with intra-arterial infusion of hyperosmolar mannitol improves the outcome in primary central nervous system lymphoma. Proper opening of the blood-brain barrier is crucial for the treatment, yet there are no means available for its real-time monitoring. The intact blood-brain barrier maintains a mV-level electrical potential difference between blood and brain tissue, giving rise to a measurable electrical signal at the scalp. Therefore, we used direct-current electroencephalography (DC-EEG) to characterize the spatiotemporal behavior of scalp-recorded slow electrical signals during blood-brain barrier opening. Nine anesthetized patients receiving chemotherapy were monitored continuously during 47 blood-brain barrier openings induced by carotid or vertebral artery mannitol infusion. Left or right carotid artery mannitol infusion generated a strongly lateralized DC-EEG response that began with a 2 min negative shift of up to 2000 μV followed by a positive shift lasting up to 20 min above the infused carotid artery territory, whereas contralateral responses were of opposite polarity. Vertebral artery mannitol infusion gave rise to a minimally lateralized and more uniformly distributed slow negative response with a posterior-frontal gradient. Simultaneously performed near-infrared spectroscopy detected a multiphasic response beginning with mannitol-bolus induced dilution of blood and ending in a prolonged increase in the oxy/deoxyhemoglobin ratio. The pronounced DC-EEG shifts are readily accounted for by opening and sealing of the blood-brain barrier. These data show that DC-EEG is a promising real-time monitoring tool for blood-brain barrier disruption augmented drug delivery.

Sterile Neuroinflammation and Strategies for Therapeutic Intervention

Sterile neuroinflammation is essential for the proper brain development and tissue repair. However, uncontrolled neuroinflammation plays a major role in the pathogenesis of various disease processes. The endogenous intracellular molecules so called damage-associated molecular patterns or alarmins or damage signals that are released by activated or necrotic cells are thought to play a crucial role in initiating an immune response. Sterile inflammatory response that occurs in Alzheimer's disease (AD), Parkinson's disease (PD), stroke, hemorrhage, epilepsy, or traumatic brain injury (TBI) creates a vicious cycle of unrestrained inflammation, driving progressive neurodegeneration. Neuroinflammation is a key mechanism in the progression (e.g., AD and PD) or secondary injury development (e.g., stroke, hemorrhage, stress, and TBI) of multiple brain conditions. Hence, it provides an opportunity for the therapeutic intervention to prevent progressive tissue damage and loss of function. The key for developing anti-neuroinflammatory treatment is to minimize the detrimental and neurotoxic effects of inflammation while promoting the beneficial and neurotropic effects, thereby creating ideal conditions for regeneration and repair. This review outlines how inflammation is involved in the pathogenesis of major nonpathogenic neuroinflammatory conditions and discusses the complex response of glial cells to damage signals. In addition, emerging experimental anti-neuroinflammatory drug treatment strategies are discussed.

Design and comparative anticonvulsant activity assessment of CNS-active alkyl-carbamoyl imidazole derivatives

A novel series of carbamoyl derivatives of alkylimidazole has been designed and their anticonvulsant activity was comparatively evaluated in the mice- and rats-maximal-electroshock (MES), subcutaneous-metrazol (scMet) seizure tests and the mice-6Hz psychomotor (6Hz) models. The ten new designed molecules contain in their chemical structure imidazole, alkyl side-chain and carbamate as three potential active moieties. In spite of the close structural features of the carbamoyl imidazole derivatives only compounds 7, 8, 13 and 16 were active at the MES test with ED50 values ranging from 12 to 20mg/kg coupled with high protective index (PI=TD50/ED50) values of 4.1-7.3 after ip administration to rats. A similar phenomenon was observed in mice where compounds 7, 8, 9, 12 had MES-ED50 values of 14-26mg/kg. Compounds 7 and 13 also demonstrated anticonvulsant activity in the 6Hz model with ED50 values of 32 and 44mg/kg, respectively. As the most active entities, compounds 7, 8 followed by 13 and 16, thus offer an optimal efficacy-safety profile and consequently, might be promising candidates for development as new antiepileptics.

Fit for purpose application of currently existing animal models in the discovery of novel epilepsy therapies

Animal seizure and epilepsy models continue to play an important role in the early discovery of new therapies for the symptomatic treatment of epilepsy. Since 1937, with the discovery of phenytoin, almost all anti-seizure drugs (ASDs) have been identified by their effects in animal models, and millions of patients world-wide have benefited from the successful translation of animal data into the clinic. However, several unmet clinical needs remain, including resistance to ASDs in about 30% of patients with epilepsy, adverse effects of ASDs that can reduce quality of life, and the lack of treatments that can prevent development of epilepsy in patients at risk following brain injury. The aim of this review is to critically discuss the translational value of currently used animal models of seizures and epilepsy, particularly what animal models can tell us about epilepsy therapies in patients and which limitations exist. Principles of translational medicine will be used for this discussion. An essential requirement for translational medicine to improve success in drug development is the availability of animal models with high predictive validity for a therapeutic drug response. For this requirement, the model, by definition, does not need to be a perfect replication of the clinical condition, but it is important that the validation provided for a given model is fit for purpose. The present review should guide researchers in both academia and industry what can and cannot be expected from animal models in preclinical development of epilepsy therapies, which models are best suited for which purpose, and for which aspects suitable models are as yet not available. Overall further development is needed to improve and validate animal models for the diverse areas in epilepsy research where suitable fit for purpose models are urgently needed in the search for more effective treatments.

OTX015 (MK-8628), a novel BET inhibitor, displays in vitro and in vivo antitumor effects alone and in combination with conventional therapies in glioblastoma models

Bromodomain and extraterminal (BET) bromodomain (BRD) proteins are epigenetic readers that bind to acetylated lysine residues on chromatin, acting as co-activators or co-repressors of gene expression. BRD2 and BRD4, members of the BET family, are significantly increased in glioblastoma multiforme (GBM), the most common primary adult brain cancer. OTX015 (MK-8628), a novel BRD2/3/4 inhibitor, is under evaluation in dose-finding studies in solid tumors, including GBM. We investigated the pharmacologic characteristics of OTX015 as a single agent and combined with targeted therapy or conventional chemotherapies in glioblastoma cell lines. OTX015 displayed higher antiproliferative effects compared to its analog JQ1, with GI50 values of approximately 0.2 µM. In addition, C-MYC and CDKN1A mRNA levels increased transiently after 4 h-exposure to OTX015, while BRD2, SESN3, HEXIM-1, HIST2H2BE, and HIST1H2BK were rapidly upregulated and sustained after 24 h. Studies in three additional GBM cell lines supported the antiproliferative effects of OTX015. In U87MG cells, OTX015 showed synergistic to additive activity when administered concomitant to or before SN38, temozolomide or everolimus. Single agent oral OTX015 significantly increased survival in mice bearing orthotopic or heterotopic U87MG xenografts. OTX015 combined simultaneously with temozolomide improved mice survival over either single agent. The passage of OTX015 across the blood-brain barrier was demonstrated with OTX015 tumor levels 7 to 15-fold higher than in normal tissues, along with preferential binding of OTX015 to tumor tissue. The significant antitumor effects seen with OTX015 in GBM xenograft models highlight its therapeutic potential in GBM patients, alone or combined with conventional chemotherapies.

Blood-brain barrier, bulk flow, and interstitial clearance in epilepsy

Understanding the pathophysiology of epilepsy implies elucidating the neurovascular modifications occurring before or at time of seizures. Cerebrovascular dysfunction provokes or sustains seizures and loss of selective blood-brain barrier (BBB) permeability is a modulator of seizure threshold. However, cerebrovascular pathology in epilepsy extends beyond BBB "leakage" to encompass vascular and parenchymal events. Whenever abnormal accumulation of protein is observed surrounding brain blood vessels, BBB disruption (BBBD) was invoked. Recent clinical and laboratory findings challenged an exclusive role of BBBD in perivascular accumulation of serum-derived products. The circulation of interstitial fluid (ISF) and its bulk flow have emerged as candidate mechanisms which play a role in clearance of CNS waste. Although controversy exists, changes of ISF flow may contribute to CNS disorders through a mechanism encompassing incomplete parenchymal clearance and accompanying accumulation of toxic byproducts. We summarize the evidence in favor and against ISF bulk flow and propose a scenario where abnormal ISF in the epileptic brain allows accumulation of brain protein, sustaining pathophysiology and altering the pharmacology of antiepileptic drugs. We also describe the methods routinely used to dissect out the contribution of BBB-dependent, vascular or paracellular mechanisms to altered neuronal excitability.

Pharmacokinetics and pharmacodynamics of antiretrovirals in the central nervous system

HIV-positive patients may be effectively treated with highly active antiretroviral therapy and such a strategy is associated with striking immune recovery and viral load reduction to very low levels. Despite undeniable results, the central nervous system (CNS) is commonly affected during the course of HIV infection, with neurocognitive disorders being as prevalent as 20-50 % of treated subjects. This review discusses the pathophysiology of CNS infection by HIV and the barriers to efficacious control of such a mechanism, including the available data on compartmental drug penetration and on pharmacokinetic/pharmacodynamic relationships. In the reviewed articles, a high variability in drug transfer to the CNS is highlighted with several mechanisms as well as methodological issues potentially influencing the observed results. Nevirapine and zidovudine showed the highest cerebrospinal fluid (CSF) to plasma ratios, although target concentrations are currently unknown for the CNS. The use of the composite CSF concentration effectiveness score has been associated with better virological outcomes (lower HIV RNA) but has been inconsistently associated with neurocognitive outcomes. These findings support the CNS effectiveness of commonly used highly antiretroviral therapies. The use of antiretroviral drugs with increased CSF penetration and/or effectiveness in treating or preventing neurocognitive disorders however needs to be assessed in well-designed prospective studies.

Both water intoxication and osmotic BBB disruption increase brain water content in rats

Our previous experiments revealed that water intoxication and osmotic BBB disruption in the rat allow penetration of high-molecular substances into the brain and that resulting changes in the internal environment of the CNS lead to pathological development, such as the loss of integrity of myelin. The aim of the present study was to determine whether the previously described phenomena are associated with increased water content in the brain. To answer the question following methods were used: a) water intoxication: intraperitoneal administration of distilled water, b) osmotic BBB disruption: application of mannitol (20 %) selectively into the internal carotid artery, c) brain wet weight was measured after decapitation, and subsequently (after six days in thermostat set at 86 °C) the dry weight were estimated d) in animals with 20 % and 30 % hyperhydration the degree of myelin deterioration was estimated e) animal locomotor activity was tested by continuous behavior tracking and analysis. Brain water content after water intoxication and following the administration of mannitol was higher than in the control group. Different degrees of hyperhydration led to different levels of brain water content and to different degrees of myelin impairment. Hyperhydration corresponding to 20 % of the body weight brought about lower locomotor activity. Increased water content in the brain after the BBB osmotic disruption is surprising because this method is frequently used in the clinical practice.

Exogenous IGFBP-2 promotes proliferation, invasion, and chemoresistance to temozolomide in glioma cells via the integrin β1-ERK pathway

BACKGROUND

Insulin-like growth factor binding protein-2 (IGFBP-2) is significantly increased in the serum of patients with malignant gliomas. High plasma IGFBP-2 levels are correlated with poor prognosis in glioma patients. However, the exact role of exogenous IGFBP-2 in gliomas is unclear.

METHODS AND RESULTS

Using the MTT cell viability assay, cell cycle analysis, and the transwell migration assay, it was demonstrated that IGFBP-2 treatment stimulated proliferation and invasion in U87 and U251 cell lines and primary SU3 glioma cells. Western blot analysis and immunofluorescence staining revealed that IGFBP-2 promoted ERK phosphorylation and nuclear translocation. Moreover, blocking ERK activation using the inhibitor PD98059 markedly reduced the effects of IGFBP-2 in glioma cells. As IGFBP-2 has an integrin-binding domain, the contribution of integrin β1 to these IGFBP-2-mediated processes was examined. Neutralisation or knockdown of the expression of integrin β1 inhibited IGFBP-2-induced ERK activation, cell proliferation, and cell invasion. Significantly, IGFBP-2 induced temozolomide resistance in glioma cells in an integrin β1/ERK-dependent manner.

CONCLUSIONS

Exogenous IGFBP-2 induces proliferation, invasion, and chemoresistance in glioma cells via integrin β1/ERK signaling, suggesting that targeting this pathway could represent a potential therapeutic strategy for the treatment of gliomas. The identification of this pathway in glioma progression provides insight into the mechanism by which serum IGFBP-2 levels can predict the prognosis of glioma patients.

Circulating angiotensin II gains access to the hypothalamus and brain stem during hypertension via breakdown of the blood-brain barrier

Angiotensin II-mediated vascular brain inflammation emerged as a novel pathophysiological mechanism in neurogenic hypertension. However, the precise underlying mechanisms and functional consequences in relation to blood-brain barrier (BBB) integrity and central angiotensin II actions mediating neurohumoral activation in hypertension are poorly understood. Here, we aimed to determine whether BBB permeability within critical hypothalamic and brain stem regions involved in neurohumoral regulation was altered during hypertension. Using digital imaging quantification after intravascularly injected fluorescent dyes and immunohistochemistry, we found increased BBB permeability, along with altered key BBB protein constituents, in spontaneously hypertensive rats within the hypothalamic paraventricular nucleus, the nucleus of the solitary tract, and the rostral ventrolateral medulla, all critical brain regions known to contribute to neurohumoral activation during hypertension. BBB disruption, including increased permeability and downregulation of constituent proteins, was prevented in spontaneously hypertensive rats treated with the AT1 receptor antagonist losartan, but not with hydralazine, a direct vasodilator. Importantly, we found circulating angiotensin II to extravasate into these brain regions, colocalizing with neurons and microglial cells. Taken together, our studies reveal a novel angiotensin II-mediated feed-forward mechanism during hypertension, by which circulating angiotensin II evokes increased BBB permeability, facilitating in turn its access to critical brain regions known to participate in blood pressure regulation.

High interpatient variability of raltegravir CSF concentrations in HIV-positive patients: a pharmacogenetic analysis

OBJECTIVES

To analyse the determinants of raltegravir CSF penetration, including the pharmacogenetics of drug transporters located at the blood-brain barrier or blood-CSF barrier.

METHODS

Plasma and CSF raltegravir concentrations were determined by a validated HPLC coupled with mass spectrometry method in adults on raltegravir-based combination antiretroviral therapy undergoing a lumbar puncture. Single nucleotide polymorphisms in the genes encoding drugs transporters (ABCB1 3435, SLCO1A2, ABCC2 and SLC22A6) and the gene encoding hepatocyte nuclear factor 4 α (HNF4α) were determined by real-time PCR.

RESULTS

In 41 patients (73.2% male, 95.1% Caucasians), the median raltegravir plasma and CSF concentrations were 165 ng/mL (83-552) and 31 ng/mL (21-56), respectively. CSF-to-plasma ratios (CPRs) ranged from 0.005 to 1.33 (median 0.20, IQR 0.04-0.36). Raltegravir trough CSF concentrations (n = 35) correlated with raltegravir plasma levels (ρ = 0.395, P = 0.019); CPRs were higher in patients with blood-brain barrier damage (0.47 versus 0.18, P = 0.02). HNF4α 613 CG genotype carriers had lower trough CSF concentrations (20 versus 37 ng/mL, P = 0.03) and CPRs (0.12 versus 0.27, P = 0.02). Following multivariate linear regression analysis, the CSF-to-serum albumin ratio was the only independent predictor of raltegravir penetration into the CSF.

CONCLUSIONS

Raltegravir penetration into the CSF shows a large interpatient variability, although CSF concentrations were above the wild-type IC50 in all patients (and above IC95 in 28.6%). In this cohort, blood-brain barrier permeability is the only independent predictor of raltegravir CPR. The impact of single nucleotide polymorphisms in selected genes on raltegravir penetration warrants further studies.

Animal and human data: where are our concepts for drug-resistant epilepsy going?

Drug-resistant epilepsy remains a challenge in the therapeutic management of patients with epilepsy. Identification of factors contributing to drug resistance might render a basis for the development of novel therapeutic approaches, for the reorganization of screening programs in drug development, and for the design of personalized treatment concepts. Therefore, experimental and clinical studies need to link efforts and collaborate in order to elucidate drug-resistance mechanisms, to define the relative clinical relevance of selected mechanisms, and to develop and validate novel therapeutic concepts in overcoming resistance.

A new dynamic in vitro modular capillaries-venules modular system: cerebrovascular physiology in a box

Background

The study of the cerebrovascular physiology is crucial to understand the pathogenesis of neurological disease and the pharmacokinetic of drugs. Appropriate models in vitro often fail to represent in vivo physiology. To address these issues we propose the use of a novel artificial vascular system that closely mimics capillary and venous segments of human cerebrovasculature while also allowing for an extensive control of the experimental variables and their manipulation.

Results

Using hollow fiber technology, we modified an existing dynamic artificial model of the blood–brain barrier (BBB) (DIV-capillary) to encompass the distal post-capillary (DIV-venules) segments of the brain circulatory system. This artificial brain vascular system is comprised of a BBB module serially connected to a venule segment. A pump generates a pulsatile flow with arterial pressure feeding the system. The perfusate of the capillary module achieves levels of shear stress, pressure, and flow rate comparable to what observed in situ. Endothelial cell exposure to flow and abluminal astrocytic stimuli allowed for the formation of a highly selective capillary BBB with a trans-endothelial electrical resistance (TEER; >700 ohm cm²) and sucrose permeability (< 1X10^-u cm/sec) comparable to in vivo. The venule module, which attempted to reproduce features of the hemodynamic microenvironment of venules, was perfused by media resulting in shear stress and intraluminal pressure levels lower than those found in capillaries. Because of altered cellular and hemodynamic factors, venule segments present a less stringent vascular bed (TEER <250 Ohm cm²; P_sucrose > 1X10^-4 cm/sec) than that of the BBB. Abluminal human brain vascular smooth muscle cells were used to reproduce the venular abluminal cell composition.

Conclusion

The unique characteristics afforded by the DIV-BBB in combination with a venule segment will realistically expand our ability to dissect and study the physiological and functional behavior of distinct segments of the human cerebrovascular network.