Reduction In Blood-brain Barrier Permeability Research Articles

MRI Metrics of Cerebral Endothelial Cell-Derived Exosomes for the Treatment of Cognitive Dysfunction Induced in Aging Rats Subjected to Type 2 Diabetes.

Ongoing neurovascular dysfunction contributes to type 2 diabetes mellitus (T2DM)-induced cognitive deficits. However, it is not known whether early post onset of T2DM interventions may reduce evolving neurovascular dysfunction and thereby lead to diminution of T2DM-induced cognitive deficits. Using multiple MRI metrics, we evaluated neurovascular changes in T2DM rats treated with exosomes derived from cerebral endothelial cells (CEC-Exos). Two months after induction of T2DM in middle-aged male rats by administration of streptozotocin nicotinamide, rats were randomly treated with CEC-Exos twice weekly or saline for 4 consecutive weeks (n = 10/group). MRI measurements were performed at the end of the treatment, which included cerebral blood flow (CBF), contrast-enhanced T1-weighted imaging, and relaxation time constants T1 and T2. MRI analysis showed that compared with controls, the CEC-Exo-treated T2DM rats exhibited significant elevation of T2 and CBF in white matter and significant augmentation of T1 and reduction of blood-brain barrier permeability in gray matter. In the hippocampus, CEC-Exo treatment significantly increased T1 and CBF. Furthermore, CEC-Exo treatment significantly reduced T2DM-induced cognitive deficits measured by the Morris water maze and odor recognition tests. Collectively, our corresponding MRI data demonstrate that treatment of T2DM rats with CEC-Exos robustly reduced neurovascular dysfunction in gray and white matter and the hippocampus.

Design, Synthesis and Biological Evaluation of Carbazole Derivatives as Antitubercular and Antibacterial Agents

Background:The neuroleptic chlorpromazine has been reported for antitubercular activity but the associated antipsychotic activity restricted its clinical presentation.Objectives:Novel derivatives of carbazole having structural similarity with chlorpromazine were designed, in an attempt to reduce the associated side effects, while retaining the antitubercular activity.Materials and Methods:The designed molecules were synthesized and screened for antitubercular and antibacterial activities. The blood-brain barrier (BBB) permeability and mammalian cell (VERO) cytotoxicity (CC50) were examined to determine the safety of compounds.Results:Among the developed compounds, 14c, 15c, 16c and 17c were found to be promising against Mtb H37Rv at MIC of 1.56 µg/ml. They were also effective against S. aureus and E. coli at MIC of 0.98 and 7.81 µg/ml, respectively. The BBB permeability of the compounds was found to be less than chlorpromazine. Therefore, the developed compounds are expected to have diminished antipsychotic effect. The compounds were further marked safe against mammalian VERO cells at CC50 > 90 µg/ml.Conclusion:The profound antitubercular activity with a concomitant reduction in BBB permeability of carbazole derivatives can pave new vista in the discovery of antitubercular drugs.

Roflumilast Reduces Cerebral Inflammation in a Rat Model of Experimental Subarachnoid Hemorrhage.

Roflumilast, a selective inhibitor for PDE4, is approved by FDA as an anti-inflammation drug for treatment of chronic obstructive pulmonary disease (COPD). This study investigates the effects of roflumilast on cerebral inflammation in the rat SAH model. Here, we show that subcutaneous administration of roflumilast (3mg/kg) significantly improved the neurological deficits. Measurement of evans blue extravasation and brain water content revealed a significant reduction of blood-brain barrier permeability and brain edema. Importantly, roflumilast treatment remarkably decreased levels of IL-1β, IL-6, and TNF-α and the number of apoptotic neurons in the brain after SAH. These results indicate that roflumilast is effective in treating cerebral inflammation following SAH.

Influence of blood-brain barrier permeability on O-(2-18F-fluoroethyl)-L-tyrosine uptake in rat gliomas.

O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) is an established tracer for the diagnosis of brain tumors with PET. This study investigates the influence of blood-brain barrier (BBB) permeability on 18F-FET uptake in two rat glioma models and one human xenograft model. F98 glioma, 9L gliosarcoma or human U87 glioblastoma cells were implanted into the striatum of 56 Fischer or RNU rats. Thereafter, animals were divided into a control group and a group receiving injections of the glucocorticoid dexamethasone (Dex). After 12-13 days of tumor growth animals received injection of Evans blue dye (EBD) to visualize BBB disturbance and underwent 18F-FET PET followed by autoradiography. Time activity curves, standardized uptake values (SUV) and Tumor-to-brain ratios (TBR) of 18F-FET uptake [18-61min post injection (p.i.)] were evaluated using a volume-of-Interest (VOI) analysis. BBB disturbance was quantitatively evaluated by EBD fluorescence. The membrane gaps of blood vessel endothelial tight junctions were measured using electron microscopy to visualize ultrastructural BBB alterations in one untreated and one Dex treated F98 glioma. Data were analyzed by two-way ANOVAs. In Dex treated animals EBD extravasation was significantly reduced in 9L (P < 0.001) and U87 (P = 0.008) models and showed a trend in F98 models (P = 0.053). In contrast, no significant differences of 18F-FET uptake were observed between Dex treated animals and control group except a decrease of the TBR in the 9L tumor model in PET (P < 0.01). Ultrastructural evaluation of tumor blood vessel endothelia revealed significant reduction of the cleft diameter between endothelial cells after Dex treatment in F98 model (P = 0.010). Despite a considerable reduction of BBB permeability in rat gliomas after Dex treatment, no relevant changes of 18F-FET uptake were noted in this experimental study. Thus, 18F-FET uptake in gliomas appears to be widely independent of the permeability of the BBB.

Abstract WP257: A New microCT-based Blood-Brain Barrier Imaging to Study Hemorrhagic Transformation of Ischemic Stroke

Background: The breakdown of the blood-brain barrier (BBB) can accelerate the progression of cerebral ischemic injury, and vice versa. Hemorrhagic transformation (HT) of ischemic stroke is linked with the loss of the BBB integrity, which has been reported to have a biphasic dynamics: a significant reduction in BBB permeability at 24h after reperfusion. Objectives: To develop a new microCT-based in vivo BBB imaging technique for small animals and investigate if (1) acute HT after ischemic stroke could be predicted with the severity of earlier BBB dysfunction and (2) BBB opening is biphasic regardless of the HT. Methods: Focal cerebral ischemia was induced by transient occlusion of middle cerebral artery (tMCAO) for 1h in 11-week-old C57/BL6 mice (n=29). Thereafter, serial microCT imaging was performed 5min after ipsi-lesional intra-carotid infusion of iopromide (240μl, 5min) at 4h, 24h, and 48h after the tMCAO. Then, animals were sacrificed after intravenous injection of 2% Evans-Blue (EB) and the extent of BBB damage was visualized in the ex vivo brain sections by measuring EB leakage with a near-infrared fluorescent (NIRF) imaging machine. Results: microCT signal due to the leakage of iopromide into the infarct lesion was clearly observed at 5min after each infusion at 4h, 24h, and 48h after stroke, which gradually decreased over 60~180min, and then completely disappeared. The iopromide-leakage on microCT corresponded closely with the EB-leakage on NIRF imaging and the infarct lesion on TTC staining. At 48h after tMCAO, the leakage of iopromide (arbibrary-unit, A.U.) was more extensive in the animals with parenchymal hematoma (n=13) than in those without (n=16): 26.3±11.7A.U. vs. 9.8±5.9A.U. (p&lt;0.001). At 24h, iopromide-leakage was non-significantly lower in the former (8.2±8.2A.U.) than in the latter (17.6±12.7A.U., p=0.07). At 4h, it did not differ between the groups (10.6±8.3A.U. vs. 7.9±5.4A.U., p=0.50). In both groups, compared with the 4h time-point, iopromide-leakage was not significantly attenuated at 24h. Conclusions: We introduce a new BBB imaging technique for small animals in vivo and show that acute HT could not be predicted with earlier microCT BBB imaging. Regardless of the HT, the biphasic BBB opening was not observed.

Cerebral Ischemia–Reperfusion Injury in Rats—A 3 T MRI Study on Biphasic Blood–Brain Barrier Opening and the Dynamics of Edema Formation

Serial magnetic resonance imaging (MRI) was performed to investigate the temporal and spatial relationship between the biphasic nature of blood-brain barrier (BBB) opening and, in parallel, edema formation after ischemia-reperfusion (I/R) injury in rats. T(2)-weighted imaging combined with T(2)-relaxometry, mainly for edema assessment, was performed at 1 h after ischemia, after reperfusion, and at 4, 24 and 48 h after reperfusion. T(1)-weighted imaging was performed before and after gadolinium contrast at the last three time points to assess BBB integrity. The biphasic course of BBB opening with a significant reduction in BBB permeability at 24 h after reperfusion, associated with a progressive expansion of leaky BBB volume, was accompanied by a peak ipsilateral edema formation. In addition, at 4 h after reperfusion, edema formation could also be detected at the contralateral striatum as determined by the elevated T(2)-values that persisted to varying degrees, indicative of widespread effects of I/R injury. The observations of this study may indicate a dynamic temporal shift in the mechanisms responsible for biphasic BBB permeability changes, with complex relations to edema formation. Stroke therapy aimed at vasogenic edema and drug delivery for neuroprotection may also be guided according to the functional status of the BBB, and these findings have to be confirmed in human stroke.

Effect of synthetic matrix metalloproteinase inhibitors on lipopolysaccharide-induced blood–brain barrier opening in rodents: Differences in response based on strains and solvents

Matrix metalloproteinase inhibitors (MMPIs) reduce blood–brain barrier (BBB) disruption and prevent cell death. Animal models of multiple sclerosis, cerebral ischemia and hemorrhage, and bacterial meningitis respond to treatment with MMPIs. We have used the intracerebral injection of lipopolysaccharide (LPS) in rat, which induces MMP production and results in a delayed opening of the BBB, to screen MMPIs to identify therapeutic agents. We hypothesized that the mouse would respond similarly to LPS and that the mouse/LPS model of BBB damage would be more useful for screening of MMPIs. Therefore, we adapted the rat LPS model to the mouse and compared the response to LPS and treatment with MMPIs. Wistar–Kyoto rats (WKY) and three strains of mice had stereotactic injections of LPS into the caudate. 14C-sucrose was used to measure permeability of the BBB 24 h after injection. Initially, we tested three broad-spectrum MMPIs in the rat, BB-1101, BB-94, and BB-2293, and a MMP-2 selective inhibitor, IW449; both BB-1101 and BB-94 significantly suppressed LPS-induced BBB damage ( p < 0.05). In the 3 mouse strains, C57/BL6, C57/BL10, and C57/BL10HIIIR2, LPS significantly opened the BBB in C57/BL6, and it was the only strain that showed a reduction in BBB permeability with BB-94. Treatment with methylprednisolone and several broad-spectrum MMPIs, including BB-1101, was ineffective in the C57/BL6. There was a significant reduction in BBB permeability seen with 10% dimethyl sulfoxide (DMSO) alone, which was used to dissolve the selective MMP-2 and-9 inhibitor, SB-3CT. The tetracycline derivative, minocycline, reduced the BBB injury in mouse by blocking the production of MMP-9. Our results show variability in rats and mice to LPS and MMPIs, which most likely is based on genetic make-up. Understanding these differences may provide important clues that could guide selection of MMPIs in treatment of neurological diseases.

Hyperthermia influences excitatory and inhibitory amino acid neurotransmitters in the central nervous system. An experimental study in the rat using behavioural, biochemical, pharmacological, and morphological approaches

Role of excitatory amino acids, glutamate, aspartate, and inhibitory amino acids, gamma aminobutyric acid (GABA) and glycine in brain damage caused by heat stress was examined in a rat model. Subjection of rats to 4 h heat stress at 38 degrees C in a biological oxygen demand (BOD) incubator resulted in a marked increase in glutamate and aspartate in some brain regions, whereas a significant decline in GABA and glycine was observed in several brain areas. Profound behavioural alterations and impairment of motor and cognitive functions were seen at this time. Breakdown of the blood-brain barrier (BBB), reduction in regional cerebral blood flow (CBF), edema formation and cell injuries are prominent in several parts of the brain. Pretreatment with multiple opioid receptor antagonist, naloxone (10 mg/kg, i.p.) significantly restored the heat stress induced decline in GABA and glycine and thwarted the elevation of glutamate and aspartate in various brain areas. The motor or cognitive deficits were also attenuated. A significant reduction in BBB permeability, cerebral blood flow abnormalities, edema formation and cell injuries was evident. These novel observations suggest that (i) glutamate, aspartate, GABA and glycine are involved in the pathophysiology of heat stress, and (ii) a balance between excitatory and inhibitory amino acids in brain is crucial in hyperthermia induced brain injuries or repair.

Effects of hypothermia on thrombin-induced brain edema formation

Recent studies have shown that thrombin plays an important role in brain edema formation after intracerebral hemorrhage (ICH). The possible mechanisms of thrombin-induced brain edema formation include blood–brain barrier (BBB) disruption and inflammatory response involving polymorphonuclear (PMN) leukocyte. Animal experiments have revealed that moderate therapeutic hypothermia improves pathological and functional outcome in various models of brain injury. In this study, we examined the effect of hypothermia on thrombin-induced brain edema formation. Effects of hypothermia on BBB permeability and the accumulation of PMN leukocytes were also determined to clarify the protective mechanism of hypothermia in this model. Anesthetized adult rats received an injection of 10 Units of thrombin into the basal ganglia. Animals were separated into the normothermic and hypothermic groups, which were housed in a room maintained at 25°C and in a cold room maintained at 5°C, respectively, for 24 h after the thrombin injection. The brain temperature in rats housed in a cold room reduced temporarily to approximately 30°C and then gradually recovered to 35°C by the end of the observation. Brain water content in the basal ganglia was significantly reduced in rats treated with hypothermia compared to the normothermic rats (84.3±0.2 vs. 82.4±0.1%; P<0.01). The decrease of brain water content was accompanied with a significant reduction in BBB permeability to Evan’s blue dye and in accumulation of PMN leukocytes. This study indicates that hypothermic treatment significantly reduces thrombin-induced brain edema formation in the rat. Inhibition of thrombin-induced BBB breakdown and inflammatory response by hypothermia appear to contribute to brain protection in this model. Hypothermic treatment may provide an approach to potentially reduce ongoing edema after ICH.

Effect of steroids on edema and sodium uptake of the brain during focal ischemia in rats.

Steroids reduce permeability of the blood-brain barrier and inhibit active sodium transport by brain capillaries in vitro. Since the rate of edema formation during the early stages of ischemia is related to the rate of sodium transport from blood to brain, this study was designed to determine whether steroids reduce ischemic edema formation by inhibiting blood-brain barrier sodium transport. Dexamethasone was compared with progesterone since the latter is a more potent inhibitor of sodium transport in isolated capillaries. Sprague-Dawley rats were treated with vehicle (n = 22) or 2 mg/kg of either dexamethasone (n = 22) or progesterone (n = 17) 1 hour before occlusion of the middle cerebral artery. After 4 hours of ischemia, brain water content and blood-brain barrier permeability to [3H] alpha-aminoisobutyric acid and sodium-22 were determined. In controls, mean +/- SEM water content of tissue in the center of the ischemic zone was 82.4 +/- 0.2%. Brain edema was significantly reduced following pretreatment with either dexamethasone (80.6 +/- 0.1%, p less than 0.001) or progesterone (81.5 +/- 0.3%, p less than 0.05). There was also a significant reduction in blood-brain barrier permeability to alpha-aminoisobutyric acid in normal brain following either treatment (e.g., 2.21 +/- 0.19 and 1.37 +/- 0.10 microliters/g/min, p less than 0.001, for control and dexamethasone treatments, respectively), but no effect on the permeability to sodium (e.g., 1.19 +/- 0.05 and 1.12 +/- 0.11 microliters/g/min for control and dexamethasone treatments, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

FACILITATION OF DRUG ENTRY INTO BRAIN BY OSMOTIC OPENING OF THE BLOOD‐BRAIN BARRIER

1. After osmotic opening, the blood-brain barrier (BBB) has been shown to reclose more rapidly to large than to small neutral, water-soluble molecules. Quantitative analysis of these data supports the creation of interendothelial pores with radii of about 200 A through which such molecules pass by both restricted diffusion and bulk flow (with solute drag) from blood to brain. 2. The major reduction in BBB permeability from 6 to 35 min following osmotic opening seems to be due to a reduction in bulk flow by a factor of about 10, rather than marked decreases in pore densities or effective pore size. On this basis, quantitative predictions of brain uptake of neutral, water soluble substances are made for various times after osmotic opening of the BBB, as a function of molecular size. 3. Implications of these results are discussed for enhancement of uptake of drugs, including enzymes and certain anti-cancer agents, by the brain. 4. The idea of a 'therapeutic window' as the period of time, following reversible osmotic opening, during which the permeability of the BBB is enhanced significantly for a particular compound, is introduced. Since the BBB is normally highly impermeable to plasma proteins, the effect of BBB opening on the uptake of highly protein-bound drugs is discussed briefly. 5. The effect of molecular charge on the passage of molecules through interendothelial pores into the brain is also discussed.