The Effects of Lipopolysaccharide on the Disrupted Blood-Brain Barrier in a Rat Model of Preeclampsia.

BACKGROUND: Preeclampsia is a disorder characterized by high blood pressure and often proteinuria during pregnancy. It is known that a subseptic dose of bacterial lipopolysaccharide (LPS) induces production of proinflammatory cytokines, and possibly increasing the risk for developing preeclampsia. We investigated the effects of LPS on the blood-brain barrier (BBB) integrity in pregnant rats with N(omega)-nitro-l-arginine methyl ester (L-NAME) induced preeclampsia. METHODS: Starting from the 10th day of gestation, pregnant rats were given L-NAME for 10 days to produce hypertension and proteinuria. Animals were then treated with a single injection of LPS on the 19th day of pregnancy. Arterial blood pressure and proteinuria were measured on the day of the experiment, which was 24 hours after the LPS injection. The BBB integrity was assessed by using Evans blue (EB) and horseradish peroxidase (HRP) tracers. RESULTS: Proteinuria was observed in varying degrees, and the arterial blood pressure increased in L-NAME-treated pregnant rats (P < .01). The overall brain EB content did not increase in these preeclamptic rats when compared to pregnant animals, and LPS treatment also did not change EB content. Ultrastructurally, frequent vesicles containing HRP reaction products were observed in the capillary endothelial cells in the cerebral cortex and hippocampus of pregnant rats treated with L-NAME (P < .01). However, LPS did not change the amounts of HRP that mainly accumulated in brain capillary endothelial cells of these animals. CONCLUSION: Our results suggest that, in this experimental setting, LPS does not change the severity of BBB disruption observed in preeclamptic animals.

Hyperbaric oxygen therapy for five days increases blood-brain barrier permeability.

This study aimed to explore the effects of hyperbaric oxygen (HBO2) on blood-brain barrier (BBB) integrity in rats, when administered for one (at 2.5 ATA, 3 HBO2 sessions a day) and five days (at 2.5 ATA, 3 HBO2 sessions a day for the first two days, and twice a day for the last three days). Horseradish peroxidase (HRP) was used to evaluate the BBB permeability. Superoxide dismutase (SOD) activity, glutathione (GSH) and malondialdehyde (MDA) levels were measured in the cerebral cortex and hippocampus regions. Frequent vesicles containing HRP reaction products were observed in capillary endothelial cells in the cerebral cortex and hippocampus of rats subjected to HBO2. The accumulation of HRP reaction products in these brain regions was significantly higher than that of control animals (P ⟨ 0.01). In animals that received HBO2, MDA levels (P ⟨ 0.01 for five days) and GSH (p ⟨ 0.05 for one day, and P ⟨ 0.01 for five days) were decreased in the cerebral cortex, whereas SOD activities slightly increased in this region. In animals that received HBO2 significant decreases in MDA (P ⟨ 0.05 for one day; P ⟨ 0.01 for five days) and GSH (P ⟨ 0.05 for five days) levels were observed in the hippocampus region, but SOD activities decreased in this region. We showed that HBO2 administered with the doses described above impaired BBB integrity in otherwise healthy rats. Therefore, we suggest that the results of this study should be taken into consideration when patients are exposed to HBO2 with the same doses.

Intravenous immunoglobulins prevent the breakdown of the blood-brain barrier in experimentally induced sepsis.

INTERVENTIONS: The effects of immunoglobulin G and immunoglobulins enriched with immunoglobulin A and immunoglobulin M on blood-brain barrier integrity and survival rates in septic rats were comparatively investigated. MEASUREMENTS: Sepsis was induced by cecal ligation and perforation in Sprague-Dawley rats. The animals were divided into the following groups: Sham, cecal ligation and perforation, cecal ligation and perforation plus immunoglobulin G (250 mg/kg, intravenous), and cecal ligation and perforation plus immunoglobulins enriched with immunoglobulin A and immunoglobulin M (250 mg/kg, intravenous). Immunoglobulins were administered 5 mins before cecal ligation and perforation and the animals were observed for behavioral changes for 24 hrs following cecal ligation and perforation. Blood-brain barrier permeability was functionally and structurally evaluated by determining the extravasation of Evans Blue and horseradish peroxidase tracers, respectively. Immunohistochemistry and Western blotting for occludin were performed. MAIN RESULTS: The high mortality rate (34%) noted in the septic rats was decreased to 15% and 3% by immunoglobulin G and immunoglobulins enriched with immunoglobulin A and immunoglobulin M, respectively (p < .01). Both immunoglobulin G and immunoglobulins enriched with immunoglobulin A and immunoglobulin M alleviated the symptoms of sickness behavior in the septic rats, with the animals becoming healthy and active. Increased extravasation of Evans Blue into the brain tissue of the septic rats was markedly decreased with the administration of both immunoglobulin G and immunoglobulins enriched with immunoglobulin A and immunoglobulin M (p < .01). Occludin expression remained essentially unchanged in all groups, including the cecal ligation and perforation group. In the cecal ligation and perforation group, increased luminal and abluminal vesicles containing electron-dense horseradish peroxidase-reaction product were noted in the cytoplasm of endothelial cells located in the hippocampus and the cerebral cortex. Tight junction was ultrastructurally intact, suggesting that the transcellular pathway is responsible for the blood-brain barrier breakdown in sepsis. Following immunoglobulin G or immunoglobulins enriched with immunoglobulin A and immunoglobulin M treatment, no ultrastructural evidence of leaky capillaries in the brain was observed in the septic rats, indicating the blockade of the transcellular pathway by immunoglobulins administration. CONCLUSIONS: Our study suggests that immunoglobulin G and immunoglobulins enriched with immunoglobulin A and immunoglobulin M improve the integrity of the blood-brain barrier and inhibits cecal ligation and perforation-induced symptoms of sickness behavior in rats.

Blood-brain barrier targeted delivery of lacosamide-conjugated gold nanoparticles: Improving outcomes in absence seizures.

OBJECTIVE: Most currently available antiepileptics are not fully effective in the prevention of seizures in absence epilepsy owing to the presence of blood-brain barrier (BBB). We aimed to test whether binding an antiepileptic drug, lacosamide (LCM), to glucose-coated gold nanoparticles (GNPs) enables efficient brain drug delivery to suppress the epileptic activity in WAG/Rij rats with absence epilepsy. METHODS: In these animals, intracranial-EEG recording, behavioral test, in vivo imaging of LCM and LCM-GNP conjugate distribution in the brain, inductively coupled plasma mass spectrometry analysis, immunofluorescence staining of glucose transporter (Glut)- 1, glial fibrillary acidic protein (GFAP), and p-glycoprotein (P-gp) and electron microscopy were performed. RESULTS: Lacosamide-GNP conjugates decreased the amplitude and frequency of spike-wave-like discharges (SWDs) and alleviated the anxiety-like behavior as assessed by EEG and elevated plus-maze test, respectively (p < 0.01). The in vivo imaging system results showed higher levels of fluorescein dye tagged to LCM-GNP in the brain during the 5-day injection period (p < 0.01). Immunofluorescence staining displayed decreased P-gp, Glut-1, and GFAP expression by LCM-GNP conjugate treatment predominantly in the cerebral cortex suggesting a potential functionality of this brain region in the modulation of neuronal activity in our experimental setting (p < 0.01). SIGNIFICANCE: We suggest that the conjugation of LCM to GNPs may provide a novel approach for efficient brain drug delivery in light of the effectiveness of our strategy not only in suppressing the seizure activity but also in decreasing the need to use high dosages of the antiepileptics to reduce the frequently encountered side effects in drug-resistant epilepsy.

Targeted delivery of lacosamide-conjugated gold nanoparticles into the brain in temporal lobe epilepsy in rats.

Temporal lobe epilepsy (TLE) is the most common form of epilepsy with focal seizures, and currently available drugs may fail to provide a thorough treatment of the patients. The present study demonstrates the utility of glucose-coated gold nanoparticles (GNPs) as selective carriers of an antiepileptic drug, lacosamide (LCM), in developing a strategy to cross the blood-brain barrier to overcome drug resistance. Intravenous administration of LCM-loaded GNPs to epileptic animals yielded significantly higher nanoparticle levels in the hippocampus compared to the nanoparticle administration to intact animals. The amplitude and frequency of EEG-waves in both ictal and interictal stages decreased significantly after LCM-GNP administration to animals with TLE, while a decrease in the number of seizures was also observed though statistically insignificant. In these animals, malondialdehyde was unaffected, and glutathione levels were lower in the hippocampus compared to sham. Ultrastructurally, LCM-GNPs were observed in the brain parenchyma after intravenous injection to animals with TLE. We conclude that glucose-coated GNPs can be efficient in transferring effective doses of LCM into the brain enabling elimination of the need to administer high doses of the drug, and hence, may represent a new approach in the treatment of drug-resistant TLE.

Influence of hypercholesterolemia and hypertension on the integrity of the blood-brain barrier in rats.

Hypercholesterolemia and/or hypertension impair endothelial function in peripheral vasculature; however, their impact on endothelial cells of brain microvessels is unclear. We investigated the effects of hypercholesterolemia on the integrity of the blood-brain barrier (BBB) and the activity of astrocytes during N(omega)-nitro-L-arginine methyl ester (L-NAME) hypertension followed by angiotensin (ANG) II. We found significant decreases in superoxide dismutase levels with all treatments except ANG II and L-NAME plus ANG II, and in catalase concentrations except ANG II and cholesterol plus L-NAME. Nitric oxide (NO) concentrations were significantly decreased by L-NAME but significantly increased by cholesterol. L-NAME-stimulated plasma malondialdehyde (MDA), Ox-LDL, and cholesterol levels were significantly augmented by cholesterol. Glutathione (GSH) levels significantly decreased, while MDA, TNF-alpha, and Ox-LDL levels significantly increased in cholesterol and/or L-NAME. The increase in BBB permeability by acute hypertension in hypercholesterolemic hypertensive animals was less than that observed in chronically hypertensive animals. Brain vessels of L-NAME-treated animals showed a considerable loss of immunoreactivity for tight junction proteins, occludin, and ZO-1. Immunoreactivity for occludin and ZO-1 increased in cholesterol plus L-NAME and decreased in cholesterol. Glial fibrillary acidic protein (GFAP) immunoreactivity was seen in few astrocytes in the brain sections of L-NAME-treated animals, but increased in cholesterol plus L-NAME. Positive immunoreactivity for vascular endothelial growth factor (VEGF) was observed in cholesterol and cholesterol plus L-NAME plus ANG II. We suggest that hypercholesterolemia may affect BBB integrity through increasing the expression of tight junction proteins and GFAP and leading to the production of VEGF, at least partly, via increased NO, TNF-alpha, and catalase in hypertensive conditions.

Morphological and functional changes of blood-brain barrier in kindled rats with cortical dysplasia.

Cortical dysplasia (CD) is one of the major causes contributing to epileptogenesis associated with blood-brain-barrier (BBB) disturbances. The current study investigated the functional and ultrastructural changes of BBB in pentylenetetrazole (PTZ)-kindled rats with CD. Pregnant rats on E17 were exposed to 145 cGy of gamma-irradiation and offspring were used for experiments. The rats were given PTZ three times per week to induce kindling. The permeability of BBB was determined by using sodium fluorescein (NaFlu). Immunohistochemistry for occludin, GFAP and c-fos, western-blot analysis for occludin and electron microscopy for the ultrastructural alterations in BBB were performed. The brain level of NaFlu did not increase in rats with CD and/or kindling. Following administration of a convulsive dose of PTZ, a significant increase in BBB permeability was observed in kindled rats with CD. Occludin immunoreactivity and expression remained essentially unchanged in all groups. Slightly enhanced immunoreactivity for GFAP was observed in all groups except control. c-fos immunoreactivity in brain sections of kindled rats with CD displayed a striking increase by convulsive PTZ challenge. Tight junctions were ultrastructurally intact, whereas markedly increased number of pinocytotic vesicles was noted in brain endothelium of kindled rats with CD by convulsive dose of PTZ. The present study showed that epileptic seizures induced by convulsive PTZ challenge during kindling-mediated epileptogenesis in the presence of CD changed both functional and ultrastructural properties of the BBB and considerably enhanced transendothelial vesicular transport, while paracellular pathway was apparently not involved in this setting.

Long-term L-NAME treatment potentiates the blood-brain barrier disruption during pentylenetetrazole-induced seizures in rats.

We investigated whether the severity of blood-brain barrier disruption caused by pentylenetetrazole-induced seizures is modified by long-term nitric oxide synthase inhibition in rats. Rats were given N-omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, in drinking water for 4 weeks, and then treated with pentylenetetrazole to induce seizures. Damage to the blood-brain barrier was investigated using Evans blue dye extravasation. Serum nitric oxide concentration was decreased in L-NAME-treated rats (P<0.01). L-NAME and/or pentylenetetrazole treatments elevated systolic blood pressure of animals (P<0.01). L-NAME caused an increase in the mortality rate after pentylenetetrazole injection leading to the death of animals at about 15 min after the onset of the seizure. Pentylenetetrazole-induced seizures in rats treated with L-NAME caused a significant increase in Evans blue dye extravasation into cerebral cortex, diencephalon and cerebellum, as compared with seizures evoked by pentylenetetrazole injection to L-NAME-untreated rats (P<0.01). Data presented here suggest that the degree of blood-brain barrier disruption induced by seizures is more pronounced in long-term nitric oxide deficiency.

Effects of lipopolysaccharide on blood-brain barrier permeability during pentylenetetrazole-induced epileptic seizures in rats.

We investigated the effects of lipopolysachharide (LPS) on functional and structural properties of the blood-brain barrier (BBB) during pentylenetetrazole (PTZ)-induced epileptic seizures in rats. Arterial blood pressure was significantly elevated during epileptic seizures irrespective of LPS pretreatment. Plasma levels of interleukin (IL)-1, interleukin (IL)-6, nitric oxide (NO) and malondialdehyde (MDA) increased while catalase concentrations decreased in animals treated with LPS, PTZ and LPS plus PTZ. The significantly increased BBB permeability to Evans blue (EB) dye in the cerebral cortex, diencephalon and cerebellum regions of rats by PTZ-induced seizures was markedly reduced upon LPS pretreatment. Immunoreactivity for tight junction proteins, zonula occludens-1 and occludin, did not change in brain vessels of animals treated with PTZ and LPS plus PTZ. Glial fibrillary acidic protein immunoreactivity was increased in LPS, but not in PTZ and LPS plus PTZ. These results indicate that LPS pretreatment reduces the passage of EB dye bound to albumin into the brain, at least partly, by increasing plasma NO and IL-6 levels during PTZ-induced epileptic seizures. We suggest that LPS may provide protective effects on the BBB integrity during epileptic seizures through transcellular pathway, since the paracellular route remained unaffected by LPS and LPS plus PTZ.

Effects of beta-hydroxybutyrate on brain vascular permeability in rats with traumatic brain injury.

This study investigates the effect of beta-hydroxybutyrate (BHB) on blood-brain barrier (BBB) integrity during traumatic brain injury (TBI) in rats. Evans blue (EB) and horseradish peroxidase (HRP) were used as determinants of BBB permeability. Glutathione (GSH) and malondialdehyde (MDA) levels were estimated in the right (injury side) cerebral cortex of animals. The gene expression levels for occludin, glucose transporter (Glut)-1, aquaporin4 (AQP4) and nuclear factor-kappaB (NF-κB) were performed, and Glut-1 and NF-κB activities were analyzed. BHB treatment decreased GSH and MDA levels in intact animals and in those exposed to TBI (P<0.05). Glut-1 protein levels decreased in sham, BHB and TBI plus BHB groups (P<0.05). NF-κB protein levels increased in animals treated with BHB and/or exposed to TBI (P<0.05). The expression levels of occludin and AQP4 did not significantly change among experimental groups. Glut-1 expression levels increased in BHB treated and untreated animals exposed to TBI (P<0.05). While NF-κB expression levels increased in animals in TBI (P<0.01), a decrease was noticed in these animals upon BHB treatment (P<0.01). In animals exposed to TBI, EB extravasation was observed in the ipsilateral cortex regardless of BHB treatment. Ultrastructurally, BHB attenuated but did not prevent the presence of HRP in brain capillary endothelial cells of animals with TBI; moreover, the drug also led to the observation of the tracer when used in intact rats (P<0.01). Altogether, these results showed that BHB not only failed to provide overall protective effects on BBB in TBI but also led to BBB disruption in healthy animals.

Association Between Polymorphisms of DNA Repair Genes and Risk of Schizophrenia.

AIMS: DNA repair gene polymorphisms have recently been implicated as potential pathogenic contributors of mental disorders. The aims of our study were to investigate the participation of nucleotide and base excision repair mechanisms in schizophrenia and to identify novel candidate DNA repair susceptibility genes. MATERIALS AND METHODS: For these purposes, we genotyped apurinic/apyrimidinic endonuclease 1 (APE1), human 8-oxoguanine DNA N-glycosylase 1 (hOGG1), X-ray repair cross-complementation group 1 (XRCC1), XRCC3, xeroderma pigmentosum group D (XPD), and xeroderma pigmentosum group G (XPG) genes in schizophrenia subjects, their healthy relatives, and unrelated healthy controls. RESULTS: Carriers of XRCC1 glutamine (Gln), XRCC3 threonine (Thr), hOGG1 cysteine (Cys), and XPD lysine (Lys) alleles were significantly more frequent among the cohort of schizophrenia patients than in controls. In contrast, the frequencies of XRCC3 methionine (Met) and XPD Gln allele carriers and hOGG1 serine (Ser)/Ser genotype carriers were higher among controls than in patients, suggesting a possible protective role for these gene variants against schizophrenia. Moreover, healthy relatives had significantly higher frequencies of XRCC3 Thr+ and XPD Lys+ genotypes than unrelated healthy controls. Minor allele frequencies, haplotypes, and overtransmitted alleles of DNA repair genes were also identified. CONCLUSION: Our findings support XRCC1, XRCC3, hOGG1, and XPD as risk genes for schizophrenia and suggest that altered DNA repair functions may be involved in schizophrenia pathophysiology.

Effects of atorvastatin on blood-brain barrier permeability during L-NAME hypertension followed by angiotensin-II in rats.

Recent studies suggest that 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, statins, can have direct effects on blood vessels beyond their cholesterol-lowering effects. We investigated the effects of atorvastatin on the functional and structural properties of blood-brain barrier (BBB) and the activity of astrocytes during the N(omega)-nitro-L-arginine methyl ester (L-NAME) hypertension followed by angiotensin (ANG) II. We found that decreases in concentration of serum catalase and plasma nitric oxide (NO) induced by L-NAME were significantly ameliorated by atorvastatin, whereas L-NAME-induced serum malondialdehyde and cholesterol concentration increases were significantly reduced by atorvastatin. The content of Evans blue (EB) dye significantly increased in cerebellum, left cerebral cortex and diencephalon regions but atorvastatin markedly reduced the increased BBB permeability to EB in the brain regions of animals treated with L-NAME and L-NAME plus ANG II. Brain vessels of L-NAME-treated animals showed a considerable loss of immunoreactivity of tight junction proteins, zonula occludens (ZO)-1 and occludin. Immunoreactivity for ZO-1 and occludin increased in animals treated with atorvastatin and L-NAME plus atorvastatin. Glial fibrillary acidic protein (GFAP) immunoreactivity was seen in few astrocytes in the brain sections of L-NAME, but immunoreactivity for GFAP increased in L-NAME plus atorvastatin-treated animals. We suggest that long-term L-NAME treatment may affect BBB permeability through disruption of tight junction proteins, at least partly, via decreased NO concentration and increased oxidant capacity; the improvement of BBB integrity and astrocytic activity would be more closely associated with the action of atorvastatin favoring the increase in anti-oxidant capacity and expression of tight junction proteins and GFAP.

Microbiologic, Pharmacokinetic, and Clinical Effects of Corneal Collagen Cross-Linking on Experimentally Induced Pseudomonas Keratitis in Rabbits.

PURPOSE: To determine the effects of corneal collagen cross-linking (CXL) on the penetration of topical 0.5% moxifloxacin, on the number of colony-forming units (CFUs) in the cornea, and on the clinical course in a rabbit eye model of experimentally induced Pseudomonas aeruginosa keratitis. METHODS: In this prospective animal study, experimental Pseudomonas corneal ulcers were induced in 56 corneas of 28 albino New Zealand rabbits. The corneas were randomly divided into the following 4 groups: the control group (14 eyes), the MOX group (moxifloxacin) (14 eyes), the MOX + CXL group (14 eyes), and the CXL group (14 eyes). On day 4 of the experiment, the eyes in the control group were enucleated and CFU counting was performed. On day 10 of the experiment, all eyes were enucleated and CFU counting was performed. In the MOX and MOX + CXL groups, the moxifloxacin level in the cornea, aqueous humor, iris, plasma, and serum was measured by reverse-phase high-performance liquid chromatography. RESULTS: The difference in the corneal CFU count between the MOX group and the MOX + CXL group was not significant (P = 0.317). Clinical improvement was greatest in the MOX + CXL group (P < 0.001). The mean corneal moxifloxacin level was 0.391 ± 0.09 µg·mg in the MOX group versus 0.291 ± 0.09 µg·mg in the MOX + CXL group; as such, CXL did not have a significant effect on antibiotic penetrance (P = 0.386). CONCLUSIONS: Clinical improvement was greatest in the MOX + CXL group. The synergistic effect of CXL on corneal ulcer treatment is not through antibiotic penetrance.

Effects of lipopolysaccharide on the radiation-induced changes in the blood-brain barrier and the astrocytes.

The use of radiation to improve the efficacy of chemotherapy on malignant brain tumors is also known to cause side effects on vascular endothelial cells and astrocytes in normal parts of the brain. We investigated the effects of lipopolysaccharide (LPS) on the functional and structural properties of blood-brain barrier (BBB) and the activity of astrocytes during whole-brain irradiation in rats. The permeability of the BBB to Evans blue (EB) dye significantly increased in the cerebral cortex, diencephalon and cerebellum regions of rats exposed to irradiation (P<0.01). In contrast, the BBB permeability in irradiated rats was significantly reduced by LPS (P<0.05). Tumor necrosis factor-alpha (TNF-alpha) levels were increased following LPS, irradiation and irradiation plus LPS (P<0.05, P<0.01). Irradiated brain vessels showed a considerable loss of staining intensity of tight junction proteins Zonula occludens-1 (ZO-1) and occludin. Staining for Zonula occludens-1 and occludin was intensive in animals treated with LPS and irradiation plus LPS. Glial fibrillary acidic protein (GFAP) immunoreactivity was seen in very few astrocytes of irradiated brains. However, this staining showed an increased positive intensity in the brain sections of LPS-treated as well as of irradiation plus LPS-treated animals. These results indicate that LPS reduces the passage of exogenous vascular tracer EB-binding albumin into the brain, at least partly, by increasing the expression of tight junction proteins and GFAP, following the irradiation. We suggest that irradiation may affect paracellular permeability through disruption of tight junction proteins, Zonula occludens-1 and occludin, and LPS could provide beneficial effects on the BBB integrity and the astrocytes against irradiation damage.

Influence of hypoosmolality on the blood-brain barrier permeability during epileptic seizures.

Changes in the blood-brain barrier permeability to macromolecules were investigated during pentylenetetrazol-induced seizures, using Evans-blue as an indicator, in water-intoxicated and nonintoxicated Wistar albino (210-250 g) adult rats of both sexes. Evans-blue albumin extravasation was judged visually and estimated quantitatively with a spectrophotometer using homogenized brain to release the dye. Hypoosmolar treatment (water intoxication) was performed by the intraperitoneal administration of distilled water to a volume of 10% of the body weight; Six groups of rats were studied. Group I: female control (n=10), Group II: male control (n=10), Group III: nonwater-intoxicated female+seizure (n=15), Group IV: nonwater-intoxicated male+seizure (n=15), Group V: water-intoxicated female+seizure (n=15), Group VI: water-intoxicated male+seizure (n=15). Approximately 2 h after the injection of water, the plasma osmolarity had decreased by 25-30 mosm. Our results revealed that in female rats, the extravasation of Evans-blue albumin was greater in the brains of water-intoxicated rats compared to nonwater-intoxicated rats after pentylenetetrazol-induced seizures. In addition, hypoosmotic female rats were shown to have a larger increase in blood-brain barrier permeability than hypoosmotic male rats after pentylenetetrazol-induced seizures. This difference between male and female rats was found to be significant (P=.005).

Effects of losartan on the blood-brain barrier permeability in long-term nitric oxide blockade-induced hypertensive rats.

Hypertension is closely associated with vascular endothelial dysfunction. The aim of this study was to investigate the effects of Angiotensin II (ANG II) receptor antagonist losartan on the blood-brain barrier (BBB) permeability in L-NAME-induced hypertension and/or in ANG II-induced acute hypertension in normotensive and hypertensive rats. Systolic blood pressure was measured by tail cuff method before, during and following L-NAME treatment (1 g/L). Losartan (3 mg/kg) was given to the animal for five days. Acute hypertension was induced by ANG II (60 microg/kg). Arterial blood pressure was directly measured on the day of the experiment. BBB disruption was quantified according to the extravasation of the albumin-bound Evans blue dye. Losartan significantly reduced the mean arterial blood pressure from 169 +/- 3.9 mmHg to 82 +/- 2.9 mmHg in L-NAME and from 171 +/- 2.9 mmHg to 84 +/- 2.9 in L-NAME plus losartan plus ANG II groups (p < 0.05). The content of Evans blue dye in the cerebral cortex significantly increased in L-NAME (p < 0.01). Moreover, the content of Evans blue dye markedly increased in the cerebellum (p < 0.001) and slightly increased in diencephalon region (p < 0.05) in L-NAME plus ANG II. Losartan reduced the increased BBB permeability to Evans blue dye in L-NAME (p < 0.01) and L-NAME plus ANG II (p < 0.001). These results indicate that L-NAME and L-NAME plus ANG II both lead to an increase in microvascular Evans blue dye efflux to brain, and losartan treatment attenuates this protein-bound dye transport into brain tissue presumably due to its protective effect on endothelial cells of brain vessels.

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

The study was performed to evaluate whether magnesium sulfate could alter the degree of disruption of the blood-brain barrier (BBB) caused by hyperosmotic mannitol. Wistar adult female rats were infused with 25% mannitol into the left internal carotid artery. Each animal received intraperitoneally a 300 mg/kg loading dose of magnesium sulfate, dissolved in 0.9% saline, followed by a further 100 mg/kg dose. In the other group, intracarotid infusion of magnesium sulfate was performed at a dose of 150 mg/kg 10 min before mannitol administration. Evans blue (EB) dye was used as a marker of BBB disruption. The measured serum glucose and magnesium levels increased after mannitol and/or magnesium administration when compared with their initial values before treatment (P < 0.01). Water content of the left hemisphere was significantly increased by hyperosmotic mannitol (P < 0.01). The increased water content in the mannitol-perfused hemisphere was significantly decreased by magnesium treatment (P < 0.05). The content of EB dye in the mannitol-perfused hemisphere markedly increased when compared with the right hemisphere of the same brain (P < 0.01). The EB dye content in the mannitol-perfused hemisphere following both intraperitoneal and intraarterial administration of magnesium decreased when compared with mannitol alone (P < 0.01). We conclude that although magnesium sulfate administration by both intracarotid arterial and intraperitoneal routes attenuates BBB disruption caused by hyperosmolar mannitol, particularly intraperitoneal route of magnesium sulfate administration may provide a useful strategy to limit the transient osmotic opening of the BBB.

Effects of acute cold exposure on blood-brain barrier permeability in acute and chronic hyperglycemic rats.

These experiments were carried out to study, the effects of cold exposure on the permeability of blood-brain barrier (BBB) in hyperglycemic rats. The integrity of the BBB was investigated using Evans blue albumin (EBA) extravasation. Serum glucose levels in hyperglycemic rats were significantly higher than that obtained from normoglycemic rats (P < 0.05). Mean arterial blood pressure in hypothermic groups significantly dropped into lower levels, than that obtained in normothermic groups (P < 0.05). The EBA extravasation to the cerebellum in the group of cold exposure+acute hyperglycemia significantly increased compared with the values obtained from the cold exposure group (P < 0.05). The EBA extravasation to the brain regions of diabetic rats exposed to cold increased more than that in normotermic control rats (P < 0.05), but did not exceed the levels in cold controls. The result of this study suggests that, acute hyperglycemia superimposed upon the permeability of BBB in the rat exposed to cold, only in selected regions of the brain, especially the cerebellum, and this result could be an important factor to explain the mechanisms of death related with hyperglycemia+cold exposure in forensic medicine.

The effect of betaine treatment on triglyceride levels and oxidative stress in the liver of ethanol-treated guinea pigs.

We investigated the effect of betaine supplementation on ethanol induced steatosis and alterations in prooxidant and antioxidant status in the liver of guinea pigs. Animals were fed with normal chow or betaine containing chow (2% w/w) for 30 days. Ethanol (3 g/kg, i.p.) was given for the last 10 days. We found that ethanol treatment caused significant increases in plasma transaminase activities, hepatic triglyceride and lipid peroxide levels. Significant decreases in glutathione (GSH), alpha-tocopherol and total ascorbic acid (AA) levels were also observed, but hepatic superoxide dismutase, glutathione peroxidase and glutathione transferase activities remained unchanged as compared with those in controls. Betaine treatment together with ethanol in guinea pigs is found to decrease hepatic triglyceride, lipid peroxide levels and serum transaminase activities and to increase GSH levels. No changes in alpha-tocopherol and total AA levels and antioxidant enzyme activities were observed with betaine treatment in alcohol treated guinea pigs. In addition, histopathological assessment of guinea pigs showed that betaine reduced the alcoholic fat accumulation in the liver. Based on these data, betaine treatment has a restoring effect on the alterations in triglyceride, lipid peroxide and GSH levels following ethanol ingestion.

The effects of superoxide dismutase mimetic MnTMPyP on the altered blood-brain barrier integrity in experimental preeclampsia with or without seizures in rats.

We investigated the effects of a cell-permeable superoxide dismutase mimetic, manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) on blood-brain barrier (BBB) integrity following pentylenetetrazole (PTZ)-induced seizures in experimental preeclampsia symptoms induced by N(omega)-nitro-l-arginine methyl ester (l-NAME) in pregnant rats. To show the functional and morphological alterations in BBB integrity, quantitative analysis of sodium fluorescein (NaFlu) extravasation, immunohistochemistry and electron microscopic assessment of horseradish peroxidase (HRP) permeability were performed. Varying degrees of proteinuria were seen and arterial blood pressure increased in l-NAME-treated pregnant rats (p<0.01). MnTMPyP pretreatment and convulsive PTZ challenge significantly decreased the immunoreactivity of occludin in hippocampal capillaries in l-NAME-treated pregnant rats (p<0.01). BBB permeability to NaFlu significantly increased in pregnant rats treated with l-NAME plus PTZ (p<0.01), but MnTMPyP pretreatment did not significantly decrease NaFlu penetration into the brain parenchyma in these animals. Ultrastructurally, frequent vesicles containing HRP reaction products were observed in the capillary endothelial cells in the cerebral cortex and hippocampus of pregnant rats treated with l-NAME and l-NAME plus PTZ with the abundance being more in the latter group. MnTMPyP pretreatment caused a marked reduction in the frequency of HRP reaction product containing vesicles in both experimental settings. In conclusion, the results of the present study provide evidence that MnTMPyP plays an important role in limiting the enhanced vesicle-mediated transcellular transport in BBB endothelium in a rat model of preeclampsia and the differences in the way of transports of NaFlu and HRP might be responsible for the different effects of MnTMPyP on the BBB permeability to these two tracers.