Extent Of Blood-brain Barrier Disruption Research Articles

FUS-mediated blood–brain barrier disruption for delivering anti-Aβ antibodies in 5XFAD Alzheimer’s disease mice

PurposeAmyloid-β (Aβ) peptides, the main component of amyloid plaques found in the Alzheimer's disease (AD) brain, are implicated in its pathogenesis, and are considered a key target in AD therapeutics. We herein propose a reliable strategy for non-invasively delivering a specific anti-Aβ antibody in a mouse model of AD by microbubbles-enhanced Focused Ultrasound (FUS)-mediated Blood–brain barrier disruption (BBBD), using a simple single stage MR-compatible positioning device.MethodsThe initial experimental work involved wild-type mice and was devoted to selecting the sonication protocol for efficient and safe BBBD. Pulsed FUS was applied using a single-element FUS transducer of 1 MHz (80 mm radius of curvature and 50 mm diameter). The success and extent of BBBD were assessed by Evans Blue extravasation and brain damage by hematoxylin and eosin staining. 5XFAD mice were divided into different subgroups; control (n = 1), FUS + MBs alone (n = 5), antibody alone (n = 5), and FUS + antibody combined (n = 10). The changes in antibody deposition among groups were determined by immunohistochemistry.ResultsIt was confirmed that the antibody could not normally enter the brain parenchyma. A single treatment with MBs-enhanced pulsed FUS using the optimized protocol (1 MHz, 0.5 MPa in-situ pressure, 10 ms bursts, 1% duty factor, 100 s duration) transiently disrupted the BBB allowing for non-invasive antibody delivery to amyloid plaques within the sonicated brain regions. This was consistently reproduced in ten mice.ConclusionThese preliminary findings should be confirmed by longer-term studies examining the antibody effects on plaque clearance and cognitive benefit to hold promise for developing disease-modifying anti-Aβ therapeutics for clinical use.

Evaluation of association between parameters related to penetration into cerebrospinal fluid and the microbiological efficacy of vancomycin in patients with bacterial meningitis

Vancomycin (VM) is used as empirical therapy for bacterial meningitis (BM). We investigated the relationship of the microbiological efficacy of VM for BM with VM minimum inhibitory concentration (MICVM), serum VM trough concentration (VMser) and cerebrospinal fluid (CSF) protein (P)/serum albumin (SA) ratio, which may reflect the extent of blood–brain barrier (BBB) disruption. Twelve BM patients were enrolled and VM was microbiologically effective in seven (58.3%). VMser, MICVM, and CSF-P/SA ratio were not associated with the microbiological efficacy of VM. The microbiological efficacy of VM was significantly associated with CSF-P/SA ratio multiplied by VMser relative to the MICVM (η = 0.61, p = 0.04). These results indicate that the parameter combining VMser, MICVM, and the extent of BBB disruption could be associated with the microbiological efficacy of VM in BM patients.

Carveol Attenuates Seizure Severity and Neuroinflammation in Pentylenetetrazole-Kindled Epileptic Rats by Regulating the Nrf2 Signaling Pathway.

Epilepsy is a neurodegenerative brain disorder characterized by recurrent seizure attacks. Numerous studies have suggested a strong correlation between oxidative stress and neuroinflammation in several neurodegenerative disorders including epilepsy. This study is aimed at investigating the neuroprotective effects of the natural compound carveol against pentylenetetrazole- (PTZ-) induced kindling and seizure model. Two different doses of carveol (10 mg/kg and 20 mg/kg) were administered to male rats to determine the effects and the effective dose of carveol and to further demonstrate the mechanism of action of nuclear factor E2-related factor (Nrf2) in PTZ-induced kindling model. Our results demonstrated reduced levels of innate antioxidants such as superoxide dismutase (SOD), catalase, glutathione-S-transferase (GST), and glutathione (GSH), associated with elevated lipid peroxidation (LPO) and inflammatory cytokines level such as tumor necrosis factor-alpha (TNF-α), and mediators like cyclooxygenase (COX-2) and nuclear factor kappa B (NFκB). These detrimental effects exacerbated oxidative stress and provoked a marked neuronal alteration in the cortex and hippocampus of PTZ-intoxicated animals that were associated with upregulated Nrf2 gene expression. Furthermore, carveol treatment positively modulated the antioxidant gene Nrf2 and its downstream target HO-1. To further investigate the role of Nrf2, an inhibitor of Nrf2 called all-trans retinoic acid (ATRA) was used, which further exacerbated PTZ toxicity. Moreover, carveol treatment induced cholinergic system activation by mitigating acetylcholinesterase level which is further linked to attenuated neuroinflammatory cascade. The extent of blood-brain barrier disruption was evaluated based on vascular endothelial growth factor (VEGF) expression. Taken together, our findings suggest that carveol acts as an Nrf2 activator and therefore induces downstream antioxidants and mitigates inflammatory insults through multiple pathways. This eventually alleviates PTZ-induced neuroinflammation and neurodegeneration.

CTNI-31. INTERIM RESULTS OF A PHASE I/IIA STUDY TO EVALUATE THE SAFETY AND EFFICACY OF BBB OPENING WITH THE SONOCLOUD-9 IMPLANTABLE ULTRASOUND DEVICE IN RECURRENT GLIOBLASTOMA PATIENTS PRIOR TO IV CARBOPLATIN

Abstract Low intensity pulsed ultrasound (LIPU), in combination with systemic injection of microbubbles, can be used to transiently disrupt the blood-brain barrier (BBB) and increase brain-drug concentrations. In pre-clinical models, carboplatin can be enhanced by a factor of 5x in the brain using LIPU and increase the survival of GBM-bearing mice. In clinical studies, a single emitter, implantable ultrasound device (SonoCloud-1) was used to disrupt the BBB in 19 rGBM patients prior to carboplatin chemotherapy (NCT02253212). The feasibility of this approach was demonstrated, and safe acoustic parameters were determined. The primary objective of this subsequent Phase 1/2a study (NCT03744026) was to demonstrate the safety of BBB disruption over a larger volume, including the tumor and surrounding peritumoral region using a nine-emitter version of the device (SonoCloud-9). This study was a 3 + 3 design using escalating numbers of activated 1-cm diameter emitters (3, 6, 9). GBM patients at any recurrence, with a maximum tumor size of < 70 mm were included. The SonoCloud-9 device was implanted during tumor debulking/resection surgery and replaced the bone flap. The device was activated every four weeks for 270 seconds, concomitantly with DEFINITY® microbubbles to disrupt the BBB prior to administration of carboplatin. Magnetic resonance imaging was performed to verify safety and the extent of BBB disruption. As of June 2020, the escalation phase of the study (9 patients) was complete, with a median of four monthly cycles of sonication and carboplatin chemotherapy per patient. No DLTs were observed. The overall tolerance of the SonoCloud-9 implant was good, with only a few, transient, and manageable related adverse events. The safety of administration of multiple repeat treatments of BBB opening using nine emitters of the device at an acoustic pressure of 1.03 MPa will be confirmed in an additional 12 patients to be included in the ongoing expansion phase.

ACTR-57. A PHASE 1/2 STUDY TO EVALUATE THE SAFETY AND EFFICACY OF BLOOD-BRAIN BARRIER (BBB) OPENING WITH A NINE-EMITTER IMPLANTABLE ULTRASOUND DEVICE IN RECURRENT GLIOBLASTOMA PATIENTS PRIOR TO CARBOPLATIN

Abstract The blood-brain barrier (BBB) limits penetration of systemically administered therapies to brain tumors and peritumoral tissue and may be responsible for the failure of numerous drugs in recent clinical trials for glioblastoma (GBM). Low intensity pulsed ultrasound (LIPU), with concomitant intravenous microbubble injection (DEFINITY®), can temporarily disrupt the BBB for 6–24 hours and allow for enhanced delivery of drugs to the brain. In previous clinical studies, a 1-cm ultrasound (US) device, SonoCloud-1, was implanted in a burr hole of recurrent GBM patients (n=27) and used to disrupt the BBB prior to carboplatin infusion at AUC5. This ongoing pilot phase 1/2 study (NCT03744026) aims to evaluate the safety and efficacy of transient opening of the BBB by LIPU in rGBM with the SonoCloud-9, a larger nine-emitter implantable device, designed to cover the tumor and surrounding infiltrative regions. The ultrasound device is implanted in a 6 cm x 6 cm bone flap window after tumor debulking surgery. Patients receive a 270-second sonication every month with concomitant microbubble injection to disrupt the BBB followed by carboplatin infusion at AUC4-6. Magnetic resonance imaging (MRI) is performed to verify safety and extent of BBB disruption. This study began enrollment in early 2019 and is an international, open-label, single arm, multi-site, dose-escalation and expansion trial to evaluate the safety of escalating sonication volume (“dose”) with concurrent carboplatin. The number of activated emitters in the implant (3, 6, 9) is increased using a 3 + 3 dose escalation design. Safety data of the escalation phase of the study will be presented.

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.

Severe Blood-Brain Barrier Disruption in Cardioembolic Stroke.

Previous studies demonstrated that cardioembolism (CE) was prone to develop hemorrhagic transformation (HT), whereas hyper-permeability of blood-brain barrier (BBB) might be one reason for the development of HT. We, thus, aimed to investigate whether the BBB permeability (BBBP) was higher in CE stroke than other stroke subtypes in acute ischemic stroke (AIS) patients. This study was a retrospective review of prospectively collected clinical and imaging database of AIS patients who underwent CT perfusion. Hypoperfusion was defined as Tmax >6 s. The average relative permeability-surface area product (rPS), reflecting the BBBP, was calculated within the hypoperfusion region (rPShypo). CE was diagnosed according to the international Trial of Org 10172 in Acute Stroke Treatment criteria. Receiver operating characteristics (ROC) curve analysis was used to determine predictive value of rPShypo for CE. Logistic regression was used to identify independent predictors for CE. A total of 187 patients were included in the final analysis [median age, 73 (61-80) years; 75 (40.1%) females; median baseline National Institutes of Health Stroke Scale score, 12 (7-16)]. Median rPShypo was 65.5 (35.8-110.1)%. Ninety-seven (51.9%) patients were diagnosed as CE. ROC analysis revealed that the optimal rPShypo threshold for CE was 86.71%. The value of rPShypo and the rate of rPShypo>86.71% were significantly higher in patients with CE than other stroke subtypes (p < 0.05), after adjusting for the potential confounds. The extent of BBB disruption is more severe in CE stroke than other stroke subtypes during the hyperacute stage.

Regulation of Caveolin-1 Expression Determines Early Brain Edema After Experimental Focal Cerebral Ischemia.

Most patients with cerebral infarction die of brain edema because of the breakdown of the blood-brain barrier (BBB) in ischemic tissue. Caveolins (a group of proteins) are key modulators of vascular permeability; however, a direct role of caveolin-1 (Cav-1) in the regulation of BBB permeability during ischemic injury has yet to be identified. Cav-1 expression was measured by immunoblotting after photothrombotic ischemia. A direct functional role of Cav-1 in cerebral edema and BBB permeability during cerebral ischemia was investigated by genetic manipulation (gene disruption and re-expression) of Cav-1 protein expression in mice. There was a significant correlation between the extent of BBB disruption and the Cav-1 expression. In Cav-1-deficient (Cav-1(-/-)) mice, the extent of BBB disruption after cerebral ischemia was increased compared with wild-type (Cav-1(+/+)) mice, whereas the increase in cerebral edema volume was ameliorated by lentiviral-mediated re-expression of Cav-1. Furthermore, Cav-1(-/-) mice had significantly higher degradation of tight junction proteins and proteolytic activity of matrix metalloproteinase than Cav-1(+/+) mice. Conversely, re-expression of Cav-1 in Cav-1(-/-) mice restored tight junction protein expression and reduced matrix metalloproteinase proteolytic activity. These results indicate that Cav-1 is a critical determinant of BBB permeability. Strategies for regulating Cav-1 represent a novel therapeutic approach to controlling BBB disruption and subsequent neurological deterioration during cerebral ischemia.

Assessment of Blood–Brain Barrier Disruption in Stroke

The disease burden of acute ischemic stroke (AIS) is rising in the United States and Canada. It is estimated that in the United States 795 000 people have a stroke each year, which amounts to $34 billion in medical expenses and lost productivity.1 Recent trials have shown the potential benefit of procedural thrombectomy in the management of AIS.2 However, despite substantial research expenditures over the past 2 decades, there have been no new pharmacological agents for the initial treatment of AIS since the approval of recombinant tissue-type plasminogen activator in 1996.3 Recently, the role of the blood–brain barrier (BBB) in the pathogenesis of AIS has emerged as a focus for new therapeutic strategies. After the onset of AIS, the BBB is rapidly disrupted and this disruption persists for days through the acute and early subacute phases of AIS. The disruption of the BBB can be quantified as an increase in the permeability of the BBB (Figure 1).4 In the setting of AIS, disruption of the BBB is thought to be a precursor to serious clinical consequences such as hemorrhagic transformation (HT),5–7 which refers to the development of a hemorrhage within the ischemic brain tissue. Current research is attempting to elucidate the mechanisms of BBB disruption after AIS and develop therapeutic strategies to mitigate the clinical consequences of BBB disruption. Figure 1. An illustration of the evolution of blood–brain barrier (BBB) disruption after stroke. The extent of BBB disruption is depicted qualitatively and is based on data gathered at our center. The period during which there is greatest disruption of the BBB coincides with the maximum risk of hemorrhagic transformation. Recombinant tissue-type plasminogen activator (r-tPA) can exacerbate BBB disruption. Given these developments, a greater number of preclinical and clinical studies are incorporating assessment of BBB …

Dual-energy CT Immediately after Endovascular Stroke Intervention: Prognostic Implications

Posttreatment intracerebral hemorrhage (ICH) after recanalization therapy of acute ischemic stroke increases morbidity and mortality. Dual-energy (DE) computed tomography (CT) allows differentiation of blood-brain barrier disruption (BBBD) and ICH. We evaluated the incidence of ICH and BBBD immediately after endovascular recanalization therapy, the correlation between BBBD and final infarction or ICH size, and the prognostic value of postinterventional BBBD. Imaging data sets (pretreatment CT, posttreatment DE-CT, and follow-up imaging by CT and/or magnetic resonance imaging) of 60 consecutive patients after endovascular recanalization therapy of acute ischemic stroke were retrospectively analyzed. After material differentiation, areas of increase attenuation in posttreatment DE-CT were correlated to ICH and infarction in follow-up imaging. Areas of hyperattenuation were observed in 80.0 % (48 of 60) of all posttreatment CT. In 10.4 % (5 of 48) of these, hyperattenuating areas matched the hyperdensities on virtual nonenhanced CT and were rated as hemorrhage. The remaining 89.6 % (43 of 48) of scans with hyperattenuating areas demonstrated hyperdensities exclusively on iodine-only images and were rated as BBBD. All suspected ICH on DE-CT were proven in follow-up imaging. There were no false-positive or false-negative findings of ICH in DE-CT. In 98.3 % (59 of 60) of cases, at least small ischemic infarctions were identified in follow-up imaging. No correlation between the extent of BBBD and the final infarct size and/or early ICH size was found. BBBD is a frequent finding after endovascular revascularization therapy. DE-CT allows for a reliable differentiation between frequent BBBD and rare ICH immediately after endovascular recanalization therapy.

Non-invasive delivery of small interfering ribonucleic acid for reduction of Huntingtin expression in the brain is achieved using focused ultrasound to disrupt the blood-brain barrier

Huntington’s disease is caused by a mutation in the Huntingtin (Htt) gene, which leads to neuronal dysfunction and cell death. Silencing of the Htt gene can halt or reverse the progression of the disease indicating that RNA interference is the most effective strategy for disease treatment. However, small interfering RNA (siRNA) does not cross the blood-brain barrier and therefore delivery to the brain is limited. Here, we demonstrate that focused ultrasound (FUS), combined with intravascular delivery of microbubble contrast agent, was used to locally and transiently disrupt the BBB in the right striatum of adult rats. 48 hours following treatment with siRNA, the right (treated) and left (control) striatum was dissected and analyzed for Htt mRNA levels. We demonstrate that FUS can non-invasively deliver siRNA-Htt directly to the striatum leading to a significant reduction of Htt expression in a dose dependent manner. Furthermore, we show that reduction of Htt with siRNA-Htt was greater when the extent of BBB disruption was increased. This study demonstrates that siRNA treatment for knockdown of mutant Htt is feasible without the surgical intervention previously required for direct delivery to the brain. Non-invasive delivery of siRNA through the blood-brain barrier (BBB) would be a significant advantage for translating this therapy to HD patients.

Focused ultrasound for targeted delivery of siRNA and efficient knockdown of Htt expression

RNA interference is a promising strategy for the treatment of Huntington's disease (HD) as it can specifically decrease the expression of the mutant Huntingtin protein (Htt). However, siRNA does not cross the blood–brain barrier and therefore delivery to the brain is limited to direct CNS delivery. Non-invasive delivery of siRNA through the blood–brain barrier (BBB) would be a significant advantage for translating this therapy to HD patients. Focused ultrasound (FUS), combined with intravascular delivery of microbubble contrast agent, was used to locally and transiently disrupt the BBB in the right striatum of adult rats. 48h following treatment with siRNA, the right (treated) and the left (control) striatum were dissected and analyzed for Htt mRNA levels. We demonstrate that FUS can non-invasively deliver siRNA-Htt directly to the striatum leading to a significant reduction of Htt expression in a dose dependent manner. Furthermore, we show that reduction of Htt with siRNA-Htt was greater when the extent of BBB disruption was increased. This study demonstrates that siRNA treatment for knockdown of mutant Htt is feasible without the surgical intervention previously required for direct delivery to the brain.

Neuroprotection and Sensorimotor Functional Improvement by Curcumin after Intracerebral Hemorrhage in Mice

Previous studies revealed that curcumin is neuroprotective in diseases of the central nervous system such as cerebral ischemia and traumatic brain injury. However, the effect of curcumin on intracerebral hemorrhage remains unclear. We, therefore, investigated the pre-clinical effect of curcumin treatment on neurological outcomes following intracerebral hemorrhage, using a mouse model. Intracerebral hemorrhage was induced by autologous blood injection into the right basal ganglia. Curcumin (150 mg/kg) was administered 15 min after intracerebral hemorrhage. Grid walk and neurological scores were evaluated at 1, 3, 7, and 14 days post-injury. Mice were killed at 24 h or 28 days following injury, for histological examination. Evans Blue and water content in the ipsilateral and contralateral hemispheres were measured to evaluate the extent of blood-brain barrier disruption and brain edema. Zonula occludens-1 was detected by immunostaining. In situ zymography was used to measure the localization and focal enzymatic activity of matrix metalloproteinase. Our results demonstrated that curcumin reduced brain edema, measured by alleviated water content and Evans Blue leakage at 24 h (p<0.05). Lateral ventricle measurements indicated that curcumin reduced brain tissue loss in the ipsilateral hemisphere (p<0.05). The same dose of curcumin also significantly attenuated neurological deficits at 1 and 3 days of intracerebral hemorrhage (p<0.05). Immunostaining showed that tight junction continuity around the hematoma was better sustained in curcumin-treated mice than in vehicle-treated mice. At 24 h, the number of matrix metalloproteinase-positive cells was significantly reduced by curcumin (p<0.05). Our study suggests that curcumin ameliorates intracerebral hemorrhage damage by preventing matrix metalloproteinase-mediated blood-brain barrier damage and brain edema, which might provide therapeutic potential for intracerebral hemorrhage.

MGMT expression in low-grade gliomas

e13001 Background: To evaluate the expression of MGMT in low-grade gliomas, and explore the relationship between its expression and the histological type of the tumour and the corresponding MRI characteristics. Methods: We assessed 389 low-grade gliomas (182 astrocytomas, 145 oligoastrocytomas, 61 oligodendrocytomas) with immunohistochemistry staining. We also recorded the preoperational MRI criteria such as tumor volume on T2 image, enhancing volume, tumor location, and relationship with ventricles. Results: The expression of MGMT in astrocytomas, oligoastrocytomas, and oligocytomas were 1.67 ± 0.78, 1.41 ± 0.86,1.44 ± 0.78, respectively. Significant stronger expression of MGMT was observed in astrocytomas than oligoastrocytomas and oligodendrocytomas (t = 3.00, p = 0.03), but no significant difference was observed between the latter two (t = 0.28, p = 0.78). MGMT expression level was significantly correlated with the enhancing volume of the tumor (r = -0.605, p = 0.002), but did not correlate with the total tumor volume (p = 0.504). Conclusions: MGMT is more strongly expressed in tumors of solely astrocyte component, and its expression level is negatively correlated with the extent of blood-brain barrier disruption. This suggest that MGMT may contribute to the tumor resistance to radiotherapy and chemotherapy in low-grade gliomas. No significant financial relationships to disclose.

Biomarkers Indicative of Blood‐Brain Barrier Disruption in Multiple Sclerosis

Blood-brain barrier (BBB) disruption is one of the hallmarks of multiple sclerosis (MS). It is incompletely understood whether BBB disruption is the initial MS event leading to MS lesion formation or whether it is merely a consequence of cellular infiltration in the central nervous system (CNS). The presence of gadolinium enhancing (Gd+) lesions on serial brain MRI scans is frequently used to evaluate BBB disruption. The presence of Gd enhancement has therefore been used as a reference for most works evaluating promising biomarkers of BBB disruption that are reviewed here. These promising biomarkers include cytokines and chemokines, and their receptors, cell surface markers, and matrix metalloproteinases and their natural inhibitors. At this time, none of these markers have been shown as sensitive as the presence of Gd enhancement to reflect BBB disruption. However, MRI scanning is not only unpractical and expensive; it may also under represent the overall extent of BBB disruption. Developing new MS biomarkers that are sensitive and specific for BBB disruption could 1) improve the monitoring of disease activity; 2) improve the monitoring of response to MS therapies which target BBB disruption; and 3) advance our understanding of dynamic MS processes participating in BBB disruption.

Changes in lCBF, morphology and related parameters by fluid percussion injury.

We investigated the pathophysiological and morphological responses of anaesthetized rats to fluid percussion brain injury generated by an original midline fluid percussion injury device. Following different grades of trauma, lCBF was measured continuously in the right parietal cortex through a burr hole using laser Doppler flowmeter, and physiological parameters were monitored. Pathological changes also were evaluated microscopically. During the first 2 hours following trauma, we found four patterns of cerebral circulatory responses. Little measurable pathophysiological response occurred after percussion pulses of less than 1.33 atmospheres (atm). In animals subjected to pulses of greater than 4.30 atm, lCBF increased synchronously with blood pressure, and then both parameters decreased continuously until death. In animals subjected to pulses of 1.53 to 2.33 atm, trauma produced a transient increase in lCBF with no synchronous rise in blood pressure. In animals subjected to pulses of 2.70 to 3.87 atm, lCBF increased synchronously with blood pressure immediately following the injury, but had decreased markedly by 60 seconds and remained below the pre-injury baseline. Blood pressure recovered to baseline within 4 minutes of the injury. The transient increase in lCBF occurred within 5 seconds following percussion pulses of greater than 1.53 atm and appeared to be independent of the rise in systemic blood pressure. Apnoea occurred in animals subjected to pulses of greater than 1.53 atm, and the duration of apnoea and mortality rate correlated with the magnitude of the applied injury. A power decrease in the electroencephalogram post-injury and a delay in its recovery, both depended on the magnitude of the injury with few regional differences in the beta-2 band power. The distribution and extent of blood-brain barrier disruption and small haemorrhages also correlated with the magnitude of the injury. The number of neurons decreased significantly in both hippocampi by 2 weeks following moderate trauma. The four patterns of lCBF changes demonstrated in the present study, as well as the other responses to injury, may be useful for studying graded models of various diffuse brain injuries.

Early changes of blood-brain barrier and superoxide scavenging activity in rat cryogenic brain injury.

Cryogenic brain injury results in blood-brain barrier (BBB) disruption which may be mediated in part by oxygen free radicals. In this study, sequential changes of BBB and endogenous superoxide scavenging activity were investigated in brains subjected to cryogenic injury. 92 male Wistar rats were sacrificed at 15, 30 minutes, 1, 2, 3, 4, 6, 24 and 48 hours after the lesion. The extent of BBB disruption was determined by quantitative assessment of Evans blue (EB) uptake based on extraction from tissue using dimethylformamide. Determination of endogenous superoxide scavenging activity in the injured brain was performed by electron spin resonance spectrometry using a spin trapping agent. Superoxide scavenging activity was significantly decreased within one hour after the injury relative to normal rat brain (p < 0.05, student's t test) persisting for at least 6 hours. The EB content in the lesioned hemisphere was significantly increased within one hour after the injury relative to the normal rat brain (p < 0.01) and continued to increase for 24 hours. In conclusion, early changes of BBB and endogenous superoxide scavenging activity in rat cryogenic injured brain indicate that BBB may be an early target for oxygen free radicals in cryogenic brain injury.

The protective effect of experimental subarachnoid haemorrhage on sodium dehydrocholate-induced blood-brain barrier disruption.

The potential interactive effects between subarachnoid hemorrhage (SAH) and blood brain barrier (BBB) disruption were studied in a rat model. Experimental subarachnoid hemorrhage was produced in twenty rats (experimental group) by the intracisternal injection of blood. In ten additional rats (control group), saline was administered in place of blood. Analysis of mean blood pressure (MBP), intracranial pressure (ICP) and cerebral perfusion pressure (CPP) demonstrated an increase in ICP and MBP and a drop in CPP in all animals following intracisternal injection. Subsequent infusion of the left internal carotid artery with sodium dehydrocholate resulted in blood-brain barrier (BBB) disruption in both groups as evidenced by Evans blue staining of the infused cortex. The extent of BBB disruption was significantly greater in the control group than the experimental group. Analysis of the experimental group demonstrated that animals with the lowest pre-SAH MBP and the lowest CPP during the maximum blood pressure response to SAH demonstrated the greatest resistance to experimental BBB disruption. The possibility of ischemia as a contributing factor in BBB protection subsequent to SAH is discussed.