As part of the neurovascular unit, the blood-brain barrier (BBB) is a unique, dynamic regulatory boundary that limits and regulates the exchange of molecules, ions, and cells between the blood and the central nervous system. Disruption of the BBB plays an important role in the development of neurological dysfunction in ischemic stroke. Blood-borne substances and cells have restricted access to the brain due to the presence of tight junctions between the endothelial cells of the BBB. Following stroke, there is loss of BBB tight junction integrity, leading to increased paracellular permeability, which results in vasogenic edema, hemorrhagic transformation, and increased mortality. Thus, understanding principal mediators and molecular mechanisms involved in BBB disruption is critical for the development of novel therapeutics to treat ischemic stroke. This review discusses the current knowledge of how neuroinflammation contributes to BBB damage in ischemic stroke. Specifically, we provide an updated overview of the role of cytokines, chemokines, oxidative and nitrosative stress, adhesion molecules, matrix metalloproteinases, and vascular endothelial growth factor as well as the role of different cell types in the regulation of BBB permeability in ischemic stroke.

With the wide availability of massively parallel sequencing technologies, genetic mapping has become the rate limiting step in mammalian forward genetics. Here we introduce a method for real-time identification of N-ethyl-N-nitrosourea-induced mutations that cause phenotypes in mice. All mutations are identified by whole exome G1 progenitor sequencing and their zygosity is established in G2/G3 mice before phenotypic assessment. Quantitative and qualitative traits, including lethal effects, in single or multiple combined pedigrees are then analyzed with Linkage Analyzer, a software program that detects significant linkage between individual mutations and aberrant phenotypic scores and presents processed data as Manhattan plots. As multiple alleles of genes are acquired through mutagenesis, pooled "superpedigrees" are created to analyze the effects. Our method is distinguished from conventional forward genetic methods because it permits (1) unbiased declaration of mappable phenotypes, including those that are incompletely penetrant (2), automated identification of causative mutations concurrent with phenotypic screening, without the need to outcross mutant mice to another strain and backcross them, and (3) exclusion of genes not involved in phenotypes of interest. We validated our approach and Linkage Analyzer for the identification of 47 mutations in 45 previously known genes causative for adaptive immune phenotypes; our analysis also implicated 474 genes not previously associated with immune function. The method described here permits forward genetic analysis in mice, limited only by the rates of mutant production and screening.N-ethyl-N-nitrosourea | genetic mapping | forward genetics | mutagenesis | massively parallel sequencing P henotypic variation in mice can be induced with N-ethyl-Nnitrosourea (ENU), which creates single base pair substitutions in germ line DNA. However, the positional cloning of ENU-induced mutations causative for phenotypes of interest has historically been a time-consuming process, beginning with generation of an outcrossed recombinant mapping population of phenotypically mutant and WT mice, genotyping individual mice at genetic markers across the genome to create a linkage map, and finally targeted sequencing to identify the causative mutation within the critical region. The advent of massively parallel sequencing techniques has given rise to more rapid "mapping-bysequencing" methods in which genome-wide marker genotyping and DNA sequencing are combined into a single step applied to either individual or pooled groups of organisms (1). For ENUmutagenized mice, early experiments used massively parallel sequencing for mutation identification within a critical region defined by traditional or bulk segregation mapping using recombinant mapping populations produced by outcrossing the mutant to another inbred laboratory strain and backcrossing or intercrossing a second time (2-4). Later reports demonstrated mapping with the identified sequence variants themselves as markers, which eliminated...

Hepatitis B virus (HBV) infections continue to occur in adult hemodialysis units. A possible contributing factor is the presence of occult HBV (serum hepatitis B surface antigen [HBsAg] negative but HBV DNA positive). Two hundred forty-one adult hemodialysis patients were screened for occult HBV. HBV DNA testing was performed by real-time polymerase chain reaction (PCR) with 2 independent primer sets (core promoter and surface). Two (0.8%) of the 241 patients were HBsAg positive. Of the remaining 239 HBsAgnegative patients, 9 (3.8%) were HBV DNA positive. Viral loads in these individuals were low (10 2 -10 4 viral copies/mL). Seven of the 9 (78%) were nt 587 mutation (sG145R mutant) positive. Demographic, biochemical, and HBV serological testing did not help to identify those with occult HBV. In conclusion, the prevalence of occult HBV in adult hemodialysis patients in this North American urban center is approximately 4 to 5 times higher than standard HBsAg testing would suggest. The majority of these infections are associated with low viral loads and a high prevalence of the sG145R mutant. Finally, the demographic, biochemical, and/or serological features of HBV DNA-positive subjects do not distinguish these individuals from the remainder of the dialysis patient population. (HEPATOLOGY 2004; 40:1072-1077.) D espite the development of an effective hepatitis B virus (HBV) vaccine and extensive infection control guidelines, HBV infections continue to occur in dialysis units throughout North America and Europe. 1-3 Based on the results of hepatitis B surface antigen (HBsAg) testing, the incidence of such infections is thought to be 0.05%-1% per year. 4 However, this likely represents an underestimate of the true incidence, as the use of more sensitive monoclonal-based assays for HBsAg detection increase positive findings in dialysis patients by 120%. 5 The relatively low acceptance and response rates to the HBV vaccine among dialysis patients likely contributes to ongoing transmission, as does the need for vaccine boosts to maintain antibody to HBsAg (anti-HBs) at protective levels. 4,6 -8 Additional contributing factors include "breakdowns" in the application of universal and/or dialysis-specific infection control measures. 4,7,9 With the development of specific and sensitive polymerase chain reaction (PCR)-based testing for HBV DNA, the presence of occult HBV infection (HBV DNA positivity in the setting of negative serum HBsAg) represents yet another possible explanation for ongoing transmission.To date, few studies have documented the prevalence of occult HBV infection in renal dialysis patients. In 3 small studies of 33, 5, and 67 HBsAg-negative dialysis patients, 50%, 40%, and 0%, respectively, were HBV DNA positive. 10 -12 Of note, the majority of HBV DNApositive individuals in these studies had serological evidence of previous HBV infection (HBV seropositive), but as many as 39% were HBV seronegative.The present study documents the prevalence of HBV DNA positivity in a large, North American renal dialys...

Cyclooxygenase-2 (COX-2) is activated in response to ischemia and significantly contributes to the neuroinflammatory process. Accumulation of COX-2-derived prostaglandin E2 (PGE2) parallels the substantial increase in stroke-mediated blood-brain barrier (BBB) breakdown. Disruption of the BBB is a serious consequence of ischemic stroke, and is mainly mediated by matrix metalloproteinases (MMPs). This study aimed to investigate the role of PGE2 EP1 receptor in neurovascular injury in stroke. We hypothesized that pharmacological blockade or genetic deletion of EP1 protects against BBB damage and hemorrhagic transformation by decreasing the levels and activity of MMP-3 and MMP-9. We found that post-ischemic treatment with the EP1 antagonist, SC-51089, or EP1 genetic deletion results in a significant reduction in BBB disruption and reduced hemorrhagic transformation in an experimental model of transient focal cerebral ischemia. These neurovascular protective effects of EP1 inactivation are associated with a significant reduction in MMP-9/-3, less peripheral neutrophil infiltration, and a preservation of tight junction proteins (ZO-1 and occludin) composing the BBB. Our study identifies the EP1 signaling pathway as an important link between neuroinflammation and MMP-mediated BBB breakdown in ischemic stroke. Targeting the EP1 receptor could represent a novel approach to diminish the devastating consequences of stroke-induced neurovascular damage.

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Resolution of inflammation is an emerging new strategy to reduce damage following ischemic stroke. Lipoxin A4 (LXA4) is an anti-inflammatory, pro-resolution lipid mediator with high affinity binding to its receptor ALX. Since LXA4 is rapidly inactivated, potent analogs have been created, including the ALX agonist BML-111. We hypothesized that post-ischemic intravenous administration of BML-111 would provide protection to the neurovascular unit and reduce neuroinflammation in a rat stroke model. Animals were subjected to 90 min of middle cerebral artery occlusion (MCAO) and BML-111 was injected 100 min and 24 h after stroke onset and animals sacrificed at 48 h. Post-ischemic treatment with BML-111 significantly reduced infarct size, decreased vasogenic edema, protected against blood-brain barrier (BBB) disruption, and reduced hemorrhagic transformation. Matrix metalloproteinase (MMP)-9 and MMP-3 were significantly reduced following BML-111 treatment. Administration of BML-111 dramatically decreased microglial activation, as seen with CD68, and neutrophil infiltration and recruitment, as assessed by levels of myeloperoxidase (MPO) and intracellular adhesion molecule (ICAM)-1. The tight junction protein zona occludens-1 (ZO-1) was protected from degradation following treatment with BML-111. These results indicate that post-ischemic activation of ALX has pro-resolution effects that limit the inflammatory damage in the cerebral cortex and helps maintain BBB integrity after ischemic stroke.

BackgroundResolution of inflammation is an emerging new strategy to reduce damage following ischemic stroke. Lipoxin A4 (LXA 4) is an anti‐inflammatory, pro‐resolution lipid mediator that reduces neuroinflammation in stroke. Since LXA 4 is rapidly inactivated, potent analogs have been synthesized, including BML‐111. We hypothesized that post‐ischemic, intravenous treatment with BML‐111 for 1 week would provide neuroprotection and reduce neurobehavioral deficits at 4 weeks after ischemic stroke in rats. Additionally, we investigated the potential protective mechanisms of BML‐111 on the post‐stroke molecular and cellular profile.MethodsA total of 133 male Sprague‐Dawley rats were subjected to 90 min of transient middle cerebral artery occlusion (MCAO) and BML‐111 administration was started at the time of reperfusion. Two methods of week‐long BML‐111 intravenous administration were tested: continuous infusion via ALZET ® osmotic pumps (1.25 and 3.75 μg μl−1 hr−1), or freshly prepared daily single injections (0.3, 1, and 3 mg/kg). We report for the first time on the stability of BML‐111 and characterized an optimal dose and a dosing schedule for the administration of BML‐111.ResultsOne week of BML‐111 intravenous injections did not reduce infarct size or improve behavioral deficits 4 weeks after ischemic stroke. However, post‐ischemic treatment with BML‐111 did elicit early protective effects as demonstrated by a significant reduction in infarct volume and improved sensorimotor function at 1 week after stroke. This protection was associated with reduced pro‐inflammatory cytokine and chemokine levels, decreased M1 CD40+ macrophages, and increased alternatively activated, anti‐inflammatory M2 microglia/macrophage cell populations in the post‐ischemic brain.ConclusionThese data suggest that targeting the endogenous LXA 4 pathway could be a promising therapeutic strategy for the treatment of ischemic stroke. More work is necessary to determine whether a different dosing regimen or more stable LXA 4 analogs could confer long‐term protection.

P-glycoprotein (P-gp) is known to transport a diverse array of xenobiotics, including therapeutic drugs. A member of the ATP-binding cassette (ABC) transporter family, P-gp is a protein encoded by the gene Mdr1 in humans and Abcb1 in rodents (represented by 2 isoforms Abcb1a and Abcb1b). Lining the luminal and abluminal membrane of brain capillary endothelial cells, P-gp is a promiscuous efflux pump extruding a variety of exogenous toxins and drugs. In this study, we measured dynamic changes in Abcb1a and Abcb1b transcripts and P-gp protein in the brain, liver, and kidney after experimental stroke. P-glycoprotein has been shown to increase in brain endothelial cells following hypoxia in vitro or after exposure to proinflammatory cytokines. Using a rat model of ischemic stroke, we hypothesized that P-gp expression will be increased in the brain, liver, and kidney in response to neuroinflammation following ischemic stroke. Adult Sprague Dawley rats underwent middle cerebral artery occlusion (MCAO) for 90 minutes and were killed at 4, 14, 24, and 48 hours postreperfusion onset to determine the time course of P-gp expression. To mimic ischemia occurring at the blood-brain barrier, rat brain endothelial (RBE4) cells were subjected to hypoxia and low glucose (HLG) for 16 hours. Immunoblotting analyses showed P-gp increases in brain and liver following 90-minute MCAO, as well as in cultured RBE4 cells after 16-hour HLG treatment, but fluctuated in the kidney depending on the time point. The relative roles of each isoform in the protein expression were analyzed with quantitative reverse transcriptase polymerase chain reaction. Ischemic stroke leads to significant increases in P-gp levels not only in the brain but also in the liver. The increase in P-gp could dramatically reduce the bioavailability and efficacy of neuroprotective drugs. Therefore, P-gp represents a big hurdle to drug delivery to the ischemic brain.