The effects of magnesium sulfate on blood-brain barrier disruption caused by intracarotid injection of hyperosmolar mannitol in rats

Teriflunomide Promotes Blood-Brain Barrier Integrity by Upregulating Claudin-1 via the Wnt/β-catenin Signaling Pathway in Multiple Sclerosis

The blood-brain barrier (BBB) and tight junction (TJ) proteins maintain the homeostasis of the central nervous system (CNS). The dysfunction of BBB allows peripheral T cells infiltration into CNS and contributes to the pathophysiology of multiple sclerosis (MS). Teriflunomide is an approved drug for the treatment of MS by suppressing lymphocytes proliferation. However, whether teriflunomide has a protective effect on BBB in MS is not understood. We found that teriflunomide restored the injured BBB in the EAE model. Furthermore, teriflunomide treatment over 6 months improved BBB permeability and reduced peripheral leakage of CNS proteins in MS patients. Teriflunomide increased human brain microvascular endothelial cell (HBMEC) viability and promoted BBB integrity in an in vitro cell model. The TJ protein claudin-1 was upregulated by teriflunomide and responsible for the protective effect on BBB. Furthermore, RNA sequencing revealed that the Wnt signaling pathway was affected by teriflunomide. The activation of Wnt signaling pathway increased claudin-1 expression and reduced BBB damage in cell model and EAE rats. Our study demonstrated that teriflunomide upregulated the expression of the tight junction protein claudin-1 in endothelial cells and promoted the integrity of BBB through Wnt signaling pathway.

Protective effects of KLF4 on blood-brain barrier and oxidative stress after cerebral ischemia-reperfusion in rats through the Nrf2/Trx1 pathway

PURPOSE

To investigate the role of KLF4 in CI/R injury and whether Nrf2/Trx1 axis acted as a downstream pathway of KLF4 to exert the protective role in blood-brain barrier destruction after CI/R.

METHODS

The tMCAO rat model in vivo was constructed and received the intracerebroventricular injection of 5 μg/kg and 10 μg/kg rhKLF4 before operation. TTC, brain water content, neurological function, ELISA, behavioral tests, HE, TUNEL, and qRT-PCR were performed to detect the protective role of KLF4 on CIR. Double-fluorescence staining and western blot were performed to determine the localization and spatiotemporal expression in brain tissues. Furthermore, we also analyzed the effect of KLF4 on the blood-brain barrier (BBB) and related mechanisms in vivo and in vitro. Nrf2 inhibitor tretinoin was applied, which was intraperitoneally injected into CIR rat. Evans blue staining was conducted. In vitro OGD/R models of bEnd.3 cells were also established, and received KLF4 overexpressed transfection and 12.5 µM tretinoin incubation. The permeability of bEnd.3 cells was evaluated by TEER and FITC-dextran leakage. BBB-related factors and oxidative stress were also analyzed, respectively. The tubular ability of KLF4 on OGD/R bEnd3 cells was also evaluated.

RESULTS

In vivo study confirmed that KLF4 was expressed in astrocyte, and its content increased with time. KLF4 protected against brain injury caused by cerebral ischemia-reperfusion, reduced cerebral infarction area and oxidative stress levels, and promoted the recovery of behavioral ability in rats. Simultaneously, mechanism experiments confirmed that the repair effect of KLF4 on cerebral ischemia-reperfusion injury was closely related to the Nrf2/Trx1 pathway. KLF4 exerted the neuroprotective effect through upregulating Nrf2/Trx1 pathway. Consistent with in vivo animal study, in vitro study also confirmed the effect of KLF4 on the permeability of bEnd.3 cells after OGD/R injury through Nrf2/Trx1 pathway.

CONCLUSION

Collectively, KLF4 played neuroprotective role in CIR induced MCAO and OGD/R, and the beneficial effects of KLF4 was partly linked to Nrf2/Trx1 pathway.

Drug Permeability: From the Blood-Brain Barrier to the Peripheral Nerve Barriers

Drug delivery into the peripheral nerves and nerve roots has important implications for effective local anesthesia and treatment of peripheral neuropathies and chronic neuropathic pain. Similar to drugs that need to cross the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) to gain access to the central nervous system (CNS), drugs must cross the peripheral nerve barriers (PNB), formed by the perineurium and blood-nerve barrier (BNB) to modulate peripheral axons. Despite significant progress made to develop effective strategies to enhance BBB permeability in therapeutic drug design, efforts to enhance drug permeability and retention in peripheral nerves and nerve roots are relatively understudied. Guided by knowledge describing structural, molecular and functional similarities between restrictive neural barriers in the CNS and peripheral nervous system (PNS), we hypothesize that certain CNS drug delivery strategies are adaptable for peripheral nerve drug delivery. In this review, we describe the molecular, structural and functional similarities and differences between the BBB and PNB, summarize and compare existing CNS and peripheral nerve drug delivery strategies, and discuss the potential application of selected CNS delivery strategies to improve efficacious drug entry for peripheral nerve disorders.

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.

Hyperosmolar blood-brain barrier opening using intra-arterial injection of hyperosmotic mannitol in mice under real-time MRI guidance

The blood-brain barrier (BBB) is the main obstacle to the effective delivery of therapeutic agents to the brain, compromising treatment efficacy for a variety of neurological disorders. Intra-arterial (IA) injection of hyperosmotic mannitol has been used to permeabilize the BBB and improve parenchymal entry of therapeutic agents following IA delivery in preclinical and clinical studies. However, the reproducibility of IA BBB manipulation is low and therapeutic outcomes are variable. We demonstrated that this variability could be highly reduced or eliminated when the procedure of osmotic BBB opening is performed under the guidance of interventional MRI. Studies have reported the utility and applicability of this technique in several species. Here we describe a protocol to open the BBB by IA injection of hyperosmotic mannitol under the guidance of MRI in mice. The procedures (from preoperative preparation to postoperative care) can be completed within ~1.5 h, and the skill level required is on par with the induction of middle cerebral artery occlusion in small animals. This MRI-guided BBB opening technique in mice can be utilized to study the biology of the BBB and improve the delivery of various therapeutic agents to the brain.

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.

Sesame Oil-Based Nanostructured Lipid Carriers of Nicergoline, Intranasal Delivery System for Brain Targeting of Synergistic Cerebrovascular Protection

Nicergoline (NIC) is a semisynthetic ergot alkaloid derivative applied for treatment of dementia and other cerebrovascular disorders. The efficacy of sesame oil to slow and reverse the symptoms of neurodegenerative cognitive disorders has been proven. This work aimed to formulate and optimize sesame oil-based NIC-nanostructured lipid carriers (NIC–NLCs) for intranasal (IN) delivery with expected synergistic and augmented neuroprotective properties. The NIC–NLC were prepared using sesame oil as a liquid lipid. A three-level, three-factor Box–Behnken design was applied to statistically optimize the effect of sesame oil (%) of the total lipid, surfactant concentration, and sonication time on particle size, zeta potential, and entrapment efficacy as responses. Solid-state characterization, release profile, and ex vivo nasal permeation in comparison to NIC solution (NIC–SOL) was studied. In vivo bioavailability from optimized NIC–NLC and NIC–SOL following IN and IV administration was evaluated and compared. The optimized NIC–NLC formula showed an average particle size of 111.18 nm, zeta potential of −15.4 mV, 95.11% entrapment efficacy (%), and 4.6% loading capacity. The NIC–NLC formula showed a biphasic, extended-release profile (72% after 48 h). Permeation of the NIC–NLC formula showed a 2.3 enhancement ratio. Bioavailability studies showed a 1.67 and 4.57 fold increase in plasma and brain following IN administration. The results also indicated efficient direct nose-to-brain targeting properties with the brain-targeting efficiency (BTE%) and direct transport percentage (DTP%) of 187.3% and 56.6%, respectively, after IN administration. Thus, sesame oil-based NIC–NLC can be considered as a promising IN delivery system for direct and efficient brain targeting with improved bioavailability and expected augmented neuroprotective action for the treatment of dementia.

Neuroprotective effect of magnesium supplementation on cerebral ischemic diseases

Ischemic encephalopathy is associated with a high mortality and rate of disability. The most common type of ischemic encephalopathy, ischemic stroke, is the second leading cause of death in the world. At present, the main treatment for ischemic stroke is to reopen blocked blood vessels. However, despite revascularization, many patients are not able to achieve good functional results. At the same time, the strict time window (<4.5 h) of thrombolytic therapy limits clinical application. Therefore, it is important to explore effective neuroprotective drugs for the treatment of ischemic stroke. Magnesium is a natural calcium antagonist, which exerts neuroprotective effects through various mechanisms. However, while most basic studies have shown that magnesium supplementation can help treat cerebral ischemia, intravenous magnesium supplementation in large clinical trials has failed to improve prognosis of ischemic patients. Therefore, we review the basic and clinical studies of magnesium supplementation for cerebral ischemia. According to the route of administration, treatment can be divided into intraperitoneal magnesium supplementation, intravenous magnesium supplementation, arterial magnesium supplementation and intracranial magnesium supplementation. We also summarized the potential influencing factors of magnesium ion intervention in cerebral ischemia injury. Finally, in combination with influencing factors derived from basic research, this article proposes three future research directions, including magnesium supplementation into the circulatory system combined with magnesium supplementation in the lateral ventricle, magnesium supplementation in the lateral ventricle combined with hypothermia therapy, and lateral ventricle magnesium supplementation combined with intracarotid magnesium supplementation combined with selective hypothermia.

Basic physiology of the blood-brain barrier in health and disease: a brief overview

The blood-brain barrier (BBB), a dynamic interface between blood and brain constituted mainly by endothelial cells of brain microvessels, robustly restricts the entry of potentially harmful blood-sourced substances and cells into the brain, however, many therapeutically active agents concurrently cannot gain access into the brain at effective doses in the presence of an intact barrier. On the other hand, breakdown of BBB integrity may involve in the pathogenesis of various neurodegenerative diseases. Besides, certain diseases/disorders such as Alzheimer's disease, hypertension, and epilepsy are associated with varying degrees of BBB disruption. In this review, we aim to highlight the current knowledge on the cellular and molecular composition of the BBB with special emphasis on the major transport pathways across the barrier type endothelial cells. We further provide a discussion on the innovative brain drug delivery strategies in which the obstacle formed by BBB interferes with effective pharmacological treatment of neurodegenerative diseases/disorders.

Strategies for Improved Intra-arterial Treatments Targeting Brain Tumors: a Systematic Review

Conventional treatments for brain tumors relying on surgery, radiation, and systemic chemotherapy are often associated with high recurrence and poor prognosis. In recent decades, intra-arterial administration of anti-cancer drugs has been considered a suitable alternative drug delivery route to intravenous and oral administration. Intra-arterial administration is believed to offer increasing drug responses by primary and metastatic brain tumors, and to be associated with better median overall survival. By directly injecting therapeutic agents into carotid or vertebral artery, intra-arterial administration rapidly increases intra-tumoral drug concentration but lowers systemic exposure. However, unexpected vascular or neural toxicity has questioned the therapeutic safety of intra-arterial drug administration and limits its widespread clinical application. Therefore, improving targeting and accuracy of intra-arterial administration has become a major research focus. This systematic review categorizes strategies for optimizing intra-arterial administration into five categories: (1) transient blood-brain barrier (BBB)/blood-tumor barrier (BTB) disruption, (2) regional cerebral hypoperfusion for peritumoral hemodynamic changes, (3) superselective endovascular intervention, (4) high-resolution imaging techniques, and (5) others such as cell and gene therapy. We summarize and discuss both preclinical and clinical research, focusing on advantages and disadvantages of different treatment strategies for a variety of cerebral tumor types.

Optimization of osmotic blood-brain barrier opening to enable intravital microscopy studies on drug delivery in mouse cortex

Intra-arterial (IA) infusion of mannitol induces osmotic blood-brain barrier opening (OBBBO) and that method has been used for decades to improve drug delivery to the brain. However, high variability of outcomes prevented vast clinical adoption. Studies on dynamic multi-scale imaging of OBBBO as well as extravasation of IA injected therapeutic agents are essential to develop strategies assuring precision and reproducibility of drug delivery. Intravital microscopy is increasingly used to capture the dynamics of biological processes at the molecular level in convenient mouse models. However, until now OBBBO has been achieved safely in subcortical structures, which prevented direct insight into the process of extravasation through the skull window. Here, we used our previously developed real-time MRI to adjust the procedure to achieve robust cortical OBBBO. We found that catheter-mediated delivery to the cortex from the ipsilateral carotid artery can be improved by temporarily occluding the contralateral carotid artery. The reproducibility and safety of the method were validated by MRI and histology. This experimental platform was further exploited for studying with intravital microscopy the extravasation of 0.58 kDa rhodamine and 153 kDa anti-VEGF monoclonal antibody (bevacizumab) upon IA injection. Dynamic imaging during IA infusion captured the spatiotemporal dynamic of infiltration for each molecule into the brain parenchyma upon OBBBO. Small-sized rhodamine exhibited faster and higher penetration than the antibody. Histological analysis showed some uptake of the monoclonal antibody after IA delivery, and OBBBO significantly amplified the extent of its uptake. For quantitative assessment of cortical uptake, bevacizumab was radiolabeled with zirconium-89 and infused intraarterially. As expected, OBBBO potentiated brain accumulation, providing 33.90 ± 9.06% of injected dose per gram of brain tissue (%ID/g) in the cortex and 17.09 ± 7.22%ID/g in subcortical structures. In contrast IA infusion with an intact BBB resulted in 3.56 ± 1.06%ID/g and 3.57 ± 0.59%ID/g in the same brain regions, respectively. This study established reproducible cortical OBBBO in mice, which enabled multi-photon microscopy studies on OBBBO and drug targeting. This approach helped demonstrate in a dynamic fashion extravasation of fluorescently-tagged antibodies and their effective delivery into the brain across an osmotically opened BBB.

Effects of irisin on the dysfunction of blood-brain barrier in rats after focal cerebral ischemia/reperfusion

OBJECTIVE

To investigate whether irisin could protect against blood-brain barrier (BBB) dysfunction following focal cerebral ischemia/reperfusion in rats.

METHODS AND MATERIALS

Seventy-two adult male Sprague Dawley rats weighing 280-320 g were randomly divided into three groups: sham operation group (S), focal cerebral ischemia/reperfusion group (FC), and irisin group (IR). Focal cerebral ischemia was induced by improved thread occlusion of right middle cerebral artery (MCAO) for 2 hr followed by reperfusion for 24 hr in rats. After 24 hr of reperfusion, the neurological evaluation was performed by the method of Longa's score. The histopathological changes were observed by HE staining. The brain water content was determined by detecting the wet weight and dry weight. The BBB permeability was assessed by fluorescence spectrophotometer and fluorescence microscopy for Evans blue (EB) extravasation. The activity and expression of matrix metalloproteinase-9 (MMP-9) in different groups were detected by immunohistochemical staining, Western blot, and gel gelatin zymography.

RESULTS

After MCAO, the neurological deficit scores, the infarct volume, the brain water content, and the EB content were higher in the FC group than those in the S group (p < .05). While after irisin treatment, these indicators mentioned above were lower than those in the IR group (p < .05). Moreover, the protein expression of MMP-9 in the cortex increased significantly after MCAO, while irisin treatment could decrease the protein expression of MMP-9 in the cortex (p < .05).

CONCLUSION

Our data suggest that irisin can attenuate brain damage both morphologically and functionally and protect BBB from disruption after focal cerebral ischemia/reperfusion, which is highly associated with the inhibition of the expression and activity of MMP-9 in the brain tissue.

Magnesium sulfate protects blood-brain barrier integrity and reduces brain edema after acute ischemic stroke in rats

Brain edema is a fatal complication of acute ischemic stroke and associated with worse outcomes in patients. This study was designed to evaluate the effects of magnesium sulfate on vasogenic brain edema formation and blood-brain barrier (BBB) disruption caused by ischemia-reperfusion (IR) in a rat model of ischemic stroke. A total of 72 male Sprague-Dawley rats were categorized into the following three primary groups: sham, control ischemic, magnesium-sulfate-treated (300 mg/kg loading dose, followed by an additional 100 mg/kg) ischemic (n = 24 in each group). Transient focal cerebral ischemia was induced by 60-min-long occlusion of the left middle cerebral artery, followed by 24-h-long reperfusion. Sensorimotor deficits, infarct volume, and brain edema were evaluated at the end of the reperfusion period. The BBB permeability was assessed by Evans Blue extravasation technique. Lipid peroxidation levels were assessed by measuring the malondialdehyde content in the brain tissue homogenate, and the activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase were detected according to the technical manual of the assay kits. Induction of cerebral ischemia in the control group produced considerable BBB damage in conjunction with severe brain edema formation. Treatment with magnesium sulfate significantly attenuated brain edema and protected BBB integrity in the ischemic lesioned hemisphere. In addition, magnesium sulfate reduced lipid peroxidation and increased antioxidant protection of brain tissue by upregulating the activities of antioxidant enzymes. Treatment with magnesium sulfate protected BBB integrity against IR-induced damage and reduced vasogenic edema formation partly via antioxidant mechanisms in a rat model of acute ischemic stroke.

Magnesium sulfate ameliorates carbon monoxide‑induced cerebral injury in male rats

Carbon monoxide (CO) has been shown to induce several cardiovascular abnormalities, as well as necrosis, apoptosis and oxidative stress in the brain. Magnesium sulfate (MS) has been shown to have beneficial activities against hypoxia in the brain. In the present study, the possible protective effects of MS against CO‑induced cerebral ischemia were investigated. For this purpose, 25 male Wistar rats were exposed to 3,000 ppm CO for 1 h. The animals were divided into 5 groups (n=5 in each group) as follows: The negative control group (not exposed to CO), the positive control group (CO exposed and treated with normal saline), and 3 groups of CO‑exposed rats treated with MS (75, 150 and 300 mg/kg/day) administered intraperitoneally for 5 consecutive days. On the 5th day, the animals were sacrificed and the brains were harvested for the evaluation of necrosis, apoptosis and oxidative stress. Histopathological evaluation revealed that MS reduced the number and intensity of necrotic insults. The Bax/Bcl2 ratio and malondialdehyde (MDA) levels were significantly decreased in a dose‑dependent manner in the MS‑treated rats compared to the positive control group, while a significant dose‑dependent increase in Akt expression, a pro‑survival protein, was observed. In addition, MS administration reduced pro‑apoptotic indice levels, ameliorated histological insults, favorably modulated oxidative status and increased Akt expression levels, indicating a possible neuroprotective effect in the case of CO poisoning. On the whole, the findings of this study indicate that MS may prove to be useful in protecting against CO‑induced cerebral injury.

Real-Time MRI Guidance for Reproducible Hyperosmolar Opening of the Blood-Brain Barrier in Mice

The blood-brain barrier (BBB) prevents effective delivery of most therapeutic agents to the brain. Intra-arterial (IA) infusion of hyperosmotic mannitol has been widely used to open the BBB and improve parenchymal targeting, but the extent of BBB disruption has varied widely with therapeutic outcomes often being unpredictable. In this work, we show that real-time MRI can enable fine-tuning of the infusion rate to adjust and predict effective and local brain perfusion in mice, and thereby can be allowed for achieving the targeted and localized BBB opening (BBBO). Both the reproducibility and safety are validated by MRI and histology. The reliable and reproducible BBBO we developed in mice will allow cost-effective studies on the biology of the BBB and drug delivery to the brain. In addition, the IA route for BBBO also permits subsequent IA delivery of a specific drug during the same procedure and obtains high targeting efficiency of the therapeutic agent in the targeted tissue, which has great potential for future clinical translation in neuro-oncology, regenerative medicine and other neurological applications.

One month of hyperglycemia alters spectral responses of the zebrafish photopic electroretinogram

Prolonged hyperglycemia can alter retinal function, ultimately resulting in blindness. Adult zebrafish adults exposed to alternating conditions of 2% glucose/0% glucose display a 3× increase in blood sugar levels. After 4 weeks of treatment, electroretinograms (ERGs) were recorded from isolated, perfused, in vitro eyecups. Control animals were exposed to alternating 2% mannitol/0% mannitol (osmotic control) or to alternating water (0% glucose/0% glucose; handling control). Two types of ERGs were recorded: (1) native ERGs measured using white-light stimuli and medium without synaptic blockers; and (2) spectral ERGs measured with an AMPA/kainate receptor antagonist, isolating photoreceptor-to-ON-bipolar-cell synapses, and a spectral protocol that separated red (R), green (G), blue (B) and UV cone signals. Retinas were evaluated for changes in layer thickness and for the inflammatory markers GFAP and Nf-κB (RelA or p65). In native ERGs, hyperglycemic b- and d-waves were lower in amplitude than the b- and d-waves of mannitol controls. Alteration of waveshape became severe, with b-waves becoming more transient and ERG responses showing more PIII-like (a-wave) characteristics. For spectral ERGs, waveshape appeared similar in all treatment groups. However, a1- and b2-wave implicit times were significantly longer, and amplitudes were significantly reduced, in response to hyperglycemic treatment, owing to the functional reduction in signals from R, G and B cones. Nf-κB increased significantly in hyperglycemic retinas, but the increase in GFAP was not significant and retinal layer thickness was unaffected. Thus, prolonged hyperglycemia triggers an inflammatory response and functional deficits localized to specific cone types, indicating the rapid onset of neural complications in the zebrafish model of diabetic retinopathy.

Summary: Zebrafish can be used to examine diabetic complications, including vision loss. Here, in zebrafish, we show that prolonged (4 week) hyperglycemia causes an inflammatory response associated with functional deficits localized to specific cone types.

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

Ischemic stroke leads to vasogenic cerebral edema and subsequent primary brain injury, which is mediated through destruction of the blood-brain barrier (BBB). Rats with induced ischemic stroke were established and used as in vivo models to investigate the functional integrity of the BBB. Spectrophotometric detection of Evans blue (EB) in the brain samples with ischemic injury could provide reliable justification for the research and development of novel therapeutic modalities. This method generates reproducible results, and is applicable in any laboratory without a need for special equipment. Here, we present a visualized and technical guideline on the detection of the extravasation of EB following induction of ischemic stroke in rats.

Magnesium Sulfate Provides Neuroprotection in Eclampsia-Like Seizure Model by Ameliorating Neuroinflammation and Brain Edema

Eclampsia is a hypertensive disorder of pregnancy that is defined by the new onset of grand mal seizures on the basis of preeclampsia and a leading cause of maternal and fetal mortality worldwide. Presently, magnesium sulfate (MgSO₄) is the most effective treatment, but the mechanism by which MgSO₄ prevents eclampsia has yet to be fully elucidated. We previously showed that systemic inflammation decreases the seizure threshold in a rat eclampsia-like model, and MgSO₄ treatment can decrease systemic inflammation. Here, we hypothesized that MgSO₄ plays a neuroprotective role in eclampsia by reducing neuroinflammation and brain edema. Pregnant Sprague-Dawley rats were given an intraperitoneal injection of pentylenetetrazol following a tail vein injection of lipopolysaccharide to establish the eclampsia-like seizure model. Seizure activity was assessed by behavioral testing. Neuronal loss in the hippocampal CA1 region (CA1) was detected by Nissl staining. Cerebrospinal fluid levels of S100-B and ferritin, indicators of neuroinflammation, were detected by enzyme-linked immunosorbent assay, and ionized calcium binder adapter molecule 1 (Iba-1, a marker for microglia) and glial fibrillary acid protein (GFAP, a marker for astrocytes) expression in the CA1 area was determined by immunofluorescence staining. Brain edema was measured. Our results revealed that MgSO₄ effectively attenuated seizure severity and CA1 neuronal loss. In addition, MgSO₄ significantly reduced cerebrospinal fluid levels of S100-B and ferritin, Iba-1 and GFAP activation in the CA1 area, and brain edema. Our results indicate that MgSO₄ plays a neuroprotective role against eclampsia-like seizure by reducing neuroinflammation and brain edema.

Magnesium sulfate treatment reverses seizure susceptibility and decreases neuroinflammation in a rat model of severe preeclampsia

Eclampsia, defined as unexplained seizure in a woman with preeclampsia, is a life-threatening complication of pregnancy with unclear etiology. Magnesium sulfate (MgSO₄) is the leading eclamptic seizure prophylactic, yet its mechanism of action remains unclear. Here, we hypothesized severe preeclampsia is a state of increased seizure susceptibility due to blood-brain barrier (BBB) disruption and neuroinflammation that lowers seizure threshold. Further, MgSO₄ decreases seizure susceptibility by protecting the BBB and preventing neuroinflammation. To model severe preeclampsia, placental ischemia (reduced uteroplacental perfusion pressure; RUPP) was combined with a high cholesterol diet (HC) to cause maternal endothelial dysfunction. RUPP+HC rats developed symptoms associated with severe preeclampsia, including hypertension, oxidative stress, endothelial dysfunction and fetal and placental growth restriction. Seizure threshold was determined by quantifying the amount of pentylenetetrazole (PTZ; mg/kg) required to elicit seizure in RUPP+HC±MgSO₄ and compared to normal pregnant controls (n = 6/group; gestational day 20). RUPP+HC rats were more sensitive to PTZ with seizure threshold being ∼65% lower vs. control (12.4±1.7 vs. 36.7±3.9 mg/kg PTZ; p<0.05) that was reversed by MgSO₄ (45.7±8.7 mg/kg PTZ; p<0.05 vs. RUPP+HC). BBB permeability to sodium fluorescein, measured in-vivo (n = 5–7/group), was increased in RUPP+HC vs. control rats, with more tracer passing into the brain (15.9±1.0 vs. 12.2±0.3 counts/gram ×1000; p<0.05) and was unaffected by MgSO₄ (15.6±1.0 counts/gram ×1000; p<0.05 vs. controls). In addition, RUPP+HC rats were in a state of neuroinflammation, indicated by 35±2% of microglia being active compared to 9±2% in normal pregnancy (p<0.01; n = 3–8/group). MgSO₄ treatment reversed neuroinflammation, reducing microglial activation to 6±2% (p<0.01 vs. RUPP+HC). Overall, RUPP+HC rats were in a state of augmented seizure susceptibility potentially due to increased BBB permeability and neuroinflammation. MgSO₄ treatment reversed this, increasing seizure threshold and decreasing neuroinflammation, without affecting BBB permeability. Thus, reducing neuroinflammation may be one mechanism by which MgSO₄ prevents eclampsia during severe preeclampsia.

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.

Dendrimer-based postnatal therapy for neuroinflammation and cerebral palsy in a rabbit model

Cerebral palsy (CP) is a chronic childhood disorder with no effective cure. Neuroinflammation, caused by activated microglia and astrocytes, plays a key role in the pathogenesis of CP and disorders such as Alzheimer's disease and multiple sclerosis. Targeting neuroinflammation can be a potent therapeutic strategy. However, delivering drugs across the blood-brain barrier to the target cells for treating diffuse brain injury is a major challenge. We show that systemically administered polyamidoamine dendrimers localize in activated microglia and astrocytes in the brain of newborn rabbits with CP, but not healthy controls. We further demonstrate that dendrimer-based N-acetyl-l-cysteine (NAC) therapy for brain injury suppresses neuroinflammation and leads to a marked improvement in motor function in the CP kits. The well-known and safe clinical profile for NAC, when combined with dendrimer-based targeting, provides opportunities for clinical translation in the treatment of neuroinflammatory disorders in humans. The effectiveness of the dendrimer-NAC treatment, administered in the postnatal period for a prenatal insult, suggests a window of opportunity for treatment of CP in humans after birth.

Intra-carotid cold magnesium sulfate infusion induces selective cerebral hypothermia and neuroprotection in rats with transient middle cerebral artery occlusion

Local hypothermia induced by intra-arterial infusion of cold saline reduces brain injury in ischemic stroke. Administration of magnesium sulfate through the internal carotid artery is also known to reduce ischemic brain damage. The neuroprotective effects of combination therapy with local endovascular hypothermia and intra-carotid magnesium sulfate infusion has not been evaluated. The aim of the study was to determine whether infusion of intra-carotid cold magnesium offers neuroprotective efficacy superior to cold saline infusion alone. Sixty-eight Sprague-Dawley rats were subjected to 3 h of middle cerebral artery occlusion and were randomly divided into six groups: sham-operated group; stroke control group; local cold magnesium infusion group; local cold saline infusion group; local normothermic magnesium infusion group; and local normothermic saline infusion group. Before reperfusion, ischemic rats received local infusion or no treatment. Infarct volume, neurological deficit, and brain water content were evaluated at 48 h after reperfusion. Selective brain hypothermia (33-34 °C) was successfully induced by intra-carotid cold infusion. Local cold saline infusion and local cold magnesium infusion reduced the infarct volumes by 48 % (p < 0.001) and 65 % (p < 0.001), respectively, compared with stroke controls. Brain water content was decreased significantly in animals treated with local cold magnesium infusion. Furthermore, the rats given a local cold magnesium infusion had the best neurological outcome. Local normothermic infusion failed to improve ischemic brain damage. These data suggest that local hypothermia induced by intra-carotid administration of cold magnesium is more effective in reducing acute ischemic damage than infusion of cold saline alone.

The protective role of 5-hydroxymethyl-2-furfural (5-HMF) against acute hypobaric hypoxia

Our previous study showed that pretreatment with 5-hydroxymethyl-2-furfural (5-HMF) led to protection against hypoxic injury via a p-ERK-mediated pathway in vitro. Whether the protection of 5-HMF against hypoxia is effective in vivo is unknown. The present study is aimed to verify the role of 5-HMF in acute hypobaric hypoxia using Kunming mice as an in vivo model and further investigate the underlying mechanisms. Mice pretreated with or without 5-HMF for 1 h were exposed to acute hypobaric hypoxic condition for 6 h and then the survival time, the survival rate, the permeability of blood-brain barrier (BBB), the histological analysis in hippocampus and cortex, and the phosphorylation level of mitogen-activated protein kinases (ERK, JNK, and p38) were investigated. The results showed that 5-HMF significantly increased the survival time and the survival rate of mice. Accordingly, pretreatment with 5-HMF markedly attenuated acute hypobaric hypoxia-induced permeability of BBB (P < 0.01). In addition, the cellular damage extent of the hippocampus and the cortex induced by hypoxia for 6 h was also attenuated by pretreatment with 5-HMF, especially in the hippocampus CA1 region. Furthermore, the activation of ERK rather than JNK and p38 was involved in the protection of 5-HMF against acute hypobaric hypoxia. In summary, 5-HMF enhanced the survival capability of mice and decreased acute hypoxic damage to the brain, which may be associated with the effects on BBB and p-ERK.

Assessment of permeability in barrier type of endothelium in brain using tracers: Evans blue, sodium fluorescein, and horseradish peroxidase

Blood-brain barrier (BBB) constituted primarily by the capillary endothelial cells functions to maintain a constant environment for the brain, by preventing or slowing down the passage of a variety of blood-borne substances, such as serum proteins, chemical compounds, ions, and hormones from the circulation into the brain parenchyma. Various diseases such as brain tumors, epilepsy, and sepsis disturb the BBB integrity leading to enhanced permeability of brain microvessels. In animal models, a variety of experimental insults targeted to the BBB integrity have been shown to increase BBB permeability causing enhanced passage of molecules into the brain paranchyma by transcellular and/or paracellular pathways. This alteration can be demonstrated by intravascular infusion of exogenous tracers and subsequent detection of extravasated molecules in the brain tissue. A number of exogenous BBB tracers are available, and they can be used for functional and structural analysis of BBB permeability. In this chapter, we aimed to highlight the basic knowledge on the use of three most commonly performed tracers, namely Evans blue dye, sodium fluorescein, and horseradish peroxidase. The experimental methodologies that we use in our laboratory for the detection of these tracers by macroscopy, spectrophotometry, spectrophotofluorometry, and electron microscopy are also discussed. While tracing studies at the morphological level are mainly aimed at the identification and characterization of the tracers both in the barrier related cells and brain parenchyma, spectrophotometric and spectrophotofluorometric assays enable quantification of BBB permeability. The results of our studies that we performed using the mentioned tracers indicate that barrier type of endothelial cells in brain play an important role in paracellular and/or transcytoplasmic trafficking of macromolecules across BBB under various experimental settings, which may provide new insights in both designing approaches for the management of diseases with BBB breakdown and developing novel trans-BBB drug delivery strategies.

A comparative study on the efficacy of 10% hypertonic saline and equal volume of 20% mannitol in the treatment of experimentally induced cerebral edema in adult rats

Background

Hypertonic saline and mannitol are commonly used in the treatment of cerebral edema and elevated intracranial pressure (ICP) at present. In this connection, 10% hypertonic saline (HS) alleviates cerebral edema more effectively than the equal volume of 20% mannitol. However, the exact underlying mechanism for this remains obscure. This study aimed to explore the possible mechanism whereby 10% hypertonic saline can ameliorate cerebral edema more effectively than mannitol.

Results

Adult male Sprague-Dawley (SD) rats were subjected to permanent right-sided middle cerebral artery occlusion (MCAO) and treated with a continuous intravenous infusion of 10% HS, 20% mannitol or D-[1-³H(N)]-mannitol. Brain water content (BWC) as analyzed by wet-to-dry ratios in the ischemic hemisphere of SD rats decreased more significantly after 10% HS treatment compared with 20% mannitol. Concentration of serum Na⁺ and plasma crystal osmotic pressure of the 10% HS group at 2, 6, 12 and 18 h following permanent MCAO increased significantly when compared with 20% mannitol treated group. Moreover, there was negative correlation between the BWC of the ipsilateral ischemic hemisphere and concentration of serum Na⁺, plasma crystal osmotic pressure and difference value of concentration of serum Na⁺ and concentration of brain Na⁺ in ipsilateral ischemic hemisphere in the 10% HS group at the various time points after MCAO. A remarkable finding was the progressive accumulation of mannitol in the ischemic brain tissue.

Conclusions

We conclude that 10% HS is more effective in alleviating cerebral edema than the equal volume of 20% mannitol. This is because 10% HS contributes to establish a higher osmotic gradient across BBB and, furthermore, the progressive accumulation of mannitol in the ischemic brain tissue counteracts its therapeutic efficacy on cerebral edema.

Effect of exposure to 50 Hz magnetic field with or without insulin on blood-brain barrier permeability in streptozotocin-induced diabetic rats

We investigated the effect of long-term exposure to modulation magnetic field (MF), insulin, and their combination on blood-brain barrier (BBB) permeability in a diabetic rat model. Fifty-three rats were randomly assigned to one of six groups: sham, exposed to no MF; MF, exposed to MF; diabetes mellitus (DM), DM induced with streptozotocin (STZ); DM plus MF (DMMF); DM plus insulin therapy (DMI); and DM plus insulin therapy plus MF (DMIMF). All the rats underwent Evans blue (EB) measurement to evaluate the BBB 30 days after the beginning of experiments. The rats in MF, DMMF, and DMIMF groups were exposed to MF (B = 5 mT) for 165 min every day for 30 days. Mean arterial blood pressure (MABP), body mass, and serum glucose level of the study rats were recorded. The extravasation of brain EB of the MF, DM, DMMF, DMI, and DMIMF groups was higher than that of the sham group and the extravasation of right hemisphere of the DMIMF group was highest (P < 0.05). The post-procedure body mass of the sham and MF groups were significantly higher than those of the DM and DMMF groups (P < 0.05). In the DM, DMMF, DMI, and DMIMF groups, the baseline glucose was significantly lower than the post-procedure glucose (P < 0.05). DM and MF increase BBB permeability; in combination, they cause more increase in BBB permeability, and insulin decreases their effect on BBB. Improved glucose metabolism may prevent body mass loss and the hypoglycemic effect of MF. DM increases MABP but MF causes no additional effect.

Magnesium sulfate for the treatment of eclampsia: a brief review

BACKGROUND AND PURPOSE

Magnesium sulfate is used extensively for prevention of eclamptic seizures. Empirical and clinical evidence supports the effectiveness of magnesium sulfate; however, questions remain as to its safety and mechanism. This review summarizes current evidence supporting the possible mechanisms of action and several controversies for magnesium sulfate treatment.

SUMMARY OF REVIEW

Several mechanisms are presented, including the effects of magnesium sulfate on peripheral and cerebral vasodilation, blood-brain barrier protection, and as an anticonvulsant.

CONCLUSIONS

Though the specific mechanisms of action remain unclear, the effect of magnesium sulfate in the prevention of eclampsia is likely multi-factorial. Magnesium sulfate may act as a vasodilator, with actions in the peripheral vasculature or the cerebrovasculature, to decrease peripheral vascular resistance or relieve vasoconstriction. Additionally, magnesium sulfate may also protect the blood-brain barrier and limit cerebral edema formation, or it may act through a central anticonvulsant action.

Intracarotid delivery of drugs: the potential and the pitfalls

The major efforts to selectively deliver drugs to the brain in the past decade have relied on smart molecular techniques to penetrate the blood-brain barrier, whereas intraarterial drug delivery has drawn relatively little attention. Meanwhile, rapid progress has been made in the field of endovascular surgery. Modern endovascular procedures can permit highly targeted drug delivery by the intracarotid route. Intracarotid drug delivery can be the primary route of drug delivery or it could be used to facilitate the delivery of smart neuropharmaceuticals. There have been few attempts to systematically understand the kinetics of intracarotid drugs. Anecdotal data suggest that intracarotid drug delivery is effective in the treatment of cerebral vasospasm, thromboembolic strokes, and neoplasms. Neuroanesthesiologists are frequently involved in the care of such high-risk patients. Therefore, it is necessary to understand the applications of intracarotid drug delivery and the unusual kinetics of intracarotid drugs.

Enhanced disruption of the blood brain barrier by intracarotid mannitol injection during transient cerebral hypoperfusion in rabbits

Fairly large volumes of intracarotid mannitol (20% to 25%) are required to disrupt the blood brain barrier (BBB), that is, 200 to 300 mL/30 s in humans or 10 mL/40 s in rabbits. During transient cerebral hypoperfusion blood flow to the rabbit brain is decreased to 0.2 to 0.3 mL/30 s. We therefore hypothesized that if the disruption of the BBB by intracarotid mannitol was primarily due to its osmotic effects, injection of 0.2 to 0.3 mL of mannitol during transient cerebral hypoperfusion will be sufficient to disrupt the BBB, thereby dramatically (by 20-folds) decrease the dose requirements compared with injections during normal blood flow. After preliminary studies, 4 doses of intracarotid mannitol were first tested: (1) 2 mL with cerebral hypoperfusion, (2) 4 mL with cerebral hypoperfusion, (3) 4 mL without cerebral hypoperfusion, and (4) 8 mL without cerebral hypoperfusion. Next, we compared the extent to which methods of drug delivery (infusion vs. bolus injection) affected BBB disruption in 12 rabbits. Finally, we assessed the duration of BBB disruption with intracarotid mannitol in another 12 rabbits. We observed that BBB disruption during injection of 4 mL of mannitol with cerebral hypoperfusion was comparable to 8 mL mannitol without cerebral hypoperfusion. Bolus injections of 4 mL mannitol were more effective than steady-state infusions. The BBB disruption with intracarotid mannitol lasted for 60 minutes postinjection. We conclude that cerebral hypoperfusion decreases the dose of intracarotid mannitol by a modest 2-fold. Our results suggest that mechanical factors may play a significant role in the osmotic disruption of the BBB by intracarotid mannitol.

Magnesium sulphate treatment decreases blood-brain barrier permeability during acute hypertension in pregnant rats

Eclampsia is associated with increased blood-brain barrier (BBB) permeability and formation of cerebral oedema. Magnesium sulphate is used to treat eclampsia despite an unclear mechanism of action. This study was to determine the effect of magnesium sulphate on in vivo BBB permeability and formation of cerebral oedema during acute hypertension and on brain aquaporin-4 (AQP4) protein expression. An in vivo model of hypertensive encephalopathy was used in late-pregnant (LP) rats following magnesium sulphate treatment, 270 mg kg(-1) i.p. injection every 4 h for 24 h. Permeability of the BBB was determined by in situ brain perfusion of Evan's Blue (EB) and sodium fluorescein (NaFl), and dye clearance determined by fluorescence spectrophotometry. Cerebral oedema was determined following acute hypertension by measuring brain water content. The effect of magnesium treatment on AQP4 expression was determined by Western blot analysis. Acute hypertension with autoregulatory breakthrough increased BBB permeability to EB in both brain regions studied (P < 0.05). Magnesium attenuated BBB permeability to EB during acute hypertension by 41% in the posterior cerebrum (P < 0.05) but had no effect in the anterior cerebrum (P > 0.05). Treatment with magnesium did not change NaFl permeability, cerebral oedema formation or AQP4 expression. In summary, BBB permeability to Evan's Blue was increased by acute hypertension in LP rats, and this was attenuated by treatment with magnesium sulphate. The greatest effect on BBB permeability to EB was in the posterior cerebrum, an area particularly susceptible to oedema formation during eclampsia.

Targeting the brain: rationalizing the novel methods of drug delivery to the central nervous system

Drug delivery to the brain has remained one of the most vexing problems in translational neuroscience research. This review rationalizes the strategies to target drugs to the brain. Factors such as the speed of intervention, the scale of intervention, the state of BBB, and the permissible risks, will all be critical in deciding how best to deliver drugs to a target site in the brain for a specific clinical situation.

Post-trauma Lipitor treatment prevents endothelial dysfunction, facilitates neuroprotection, and promotes locomotor recovery following spinal cord injury

We have previously reported neuroprotection in spinal cord injury (SCI) by Lipitor [atorvastatin (AT)]-pre-treatment. Though informative, pre-treatment studies find only limited clinical application as trauma occurrence is unpredictable. Therefore, this study investigates the efficacy of AT treatment post-SCI. In a rat model of contusion-SCI resulting in complete hindlimb paralysis, AT treatment (5 mg/kg; gavage) was begun 2, 4, or 6 h post-SCI followed by a once daily dose thereafter for 6 weeks. While the placebo vehicle (VHC)-SCI rats showed substantial functional deficit, AT-SCI animals exhibited significant functional recovery. AT diminished injury-induced blood-spinal cord barrier (BSCB) dysfunction with significantly reduced infiltration and tumor necrosis factor-alpha/interleukin-1beta/inducible nitric oxide synthase expression at site of injury. BSCB protection in AT-SCI was attributable to attenuated matrix metalloproteinase-9 (MMP9) expression - a central player in BSCB disruption. Furthermore, endothelial MMP9 expression was found to be RhoA/ROCK pathway-mediated and regulated by AT through an isoprenoid-dependent mechanism. Attenuation of these early inflammatory events reduced secondary damage. Significant reduction in axonal degeneration, myelin degradation, gliosis, and neuronal apoptosis with resultant enhancement in tissue sparing was observed in AT-SCI compared with VHC-SCI. In summary, this novel report presenting the efficacy of post-injury AT treatment might be of critical therapeutic value as effective treatments are currently unavailable for SCI.

Streptozotocin-induced diabetes progressively increases blood-brain barrier permeability in specific brain regions in rats

This study investigated the effects of streptozotocin-induced diabetes on the functional integrity of the blood-brain barrier in the rat at 7, 28, 56, and 90 days, using vascular space markers ranging in size from 342 to 65,000 Da. We also examined the effect of insulin treatment of diabetes on the formation and progression of cerebral microvascular damage and determined whether observed functional changes occurred globally throughout the brain or within specific brain regions. Results demonstrate that streptozotocin-induced diabetes produced a progressive increase in blood-brain barrier permeability to small molecules from 28 to 90 days and these changes in blood-brain barrier permeability were region specific, with the midbrain most susceptible to diabetes-induced microvascular damage. In addition, results showed that insulin treatment of diabetes attenuated blood-brain barrier disruption, especially during the first few weeks; however, as diabetes progressed, it was evident that microvascular damage occurred even when hyperglycemia was controlled. Overall, results of this study suggest that diabetes-induced perturbations to cerebral microvessels may disrupt homeostasis and contribute to long-term cognitive and functional deficits of the central nervous system.