Glial type specific regulation of CNS angiogenesis by HIFα-activated different signaling pathways.

The mechanisms by which oligodendroglia modulate CNS angiogenesis remain elusive. Previous in vitro data suggest that oligodendroglia regulate CNS endothelial cell proliferation and blood vessel formation through hypoxia inducible factor alpha (HIFα)-activated Wnt (but not VEGF) signaling. Using in vivo genetic models, we show that HIFα in oligodendroglia is necessary and sufficient for angiogenesis independent of CNS regions. At the molecular level, HIFα stabilization in oligodendroglia does not perturb Wnt signaling but rather activates VEGF. At the functional level, genetically blocking oligodendroglia-derived VEGF but not Wnt significantly decreases oligodendroglial HIFα-regulated CNS angiogenesis. Blocking astroglia-derived Wnt signaling reduces astroglial HIFα-regulated CNS angiogenesis. Together, our in vivo data demonstrate that oligodendroglial HIFα regulates CNS angiogenesis through Wnt-independent and VEGF-dependent signaling. These findings suggest an alternative mechanistic understanding of CNS angiogenesis by postnatal glial cells and unveil a glial cell type-dependent HIFα-Wnt axis in regulating CNS vessel formation.

Spatiotemporal Progression of Microcalcification in the Hippocampal CA1 Region following Transient Forebrain Ischemia in Rats: An Ultrastructural Study.

Calcification in areas of neuronal degeneration is a common finding in several neuropathological disorders including ischemic insults. Here, we performed a detailed examination of the onset and spatiotemporal profile of calcification in the CA1 region of the hippocampus, where neuronal death has been observed after transient forebrain ischemia. Histopathological examinations showed very little alizarin red staining in the CA1 pyramidal cell layer until day 28 after reperfusion, while prominent alizarin red staining was detected in CA1 dendritic subfields, particularly in the stratum radiatum, by 14 days after reperfusion. Electron microscopy using the osmium/potassium dichromate method and electron probe microanalysis revealed selective calcium deposits within the mitochondria of degenerating dendrites at as early as 7 days after reperfusion, with subsequent complete mineralization occurring throughout the dendrites, which then coalesced to form larger mineral conglomerates with the adjacent calcifying neurites by 14 days after reperfusion. Large calcifying deposits were frequently observed at 28 days after reperfusion, when they were closely associated with or completely engulfed by astrocytes. In contrast, no prominent calcification was observed in the somata of CA1 pyramidal neurons showing the characteristic features of necrotic cell death after ischemia, although what appeared to be calcified mitochondria were noted in some degenerated neurons that became dark and condensed. Thus, our data indicate that intrahippocampal calcification after ischemic insults initially occurs within the mitochondria of degenerating dendrites, which leads to the extensive calcification that is associated with ischemic injuries. These findings suggest that in degenerating neurons, the calcified mitochondria in the dendrites, rather than in the somata, may serve as the nidus for further calcium precipitation in the ischemic hippocampus.

Association between respiratory and postural adaptations and self-perception of school-aged children with mouth breathing in relation to their quality of life

Objective: To investigate the respiratory and postural adaptations associated with mouth and nasal breathing and to evaluate the associations of such adaptations in mouth breathers' self-perceived quality of life. Method: Cross-sectional study with mouth breathers (initial n=116 and final n=48) and nasal breathers (initial n=131 and final n=24) from elementary school, aged between 7 and 14 years. Chest expansion, using cirtometry, the breathing pattern and the use of accessory muscles, by means of clinical evaluations and photogrammetry, and flexibility tests were evaluated in both groups. Subsequently, the mouth breathers were asked to complete the quality of life questionnaire. Statistical tests: Chi-square, odds ratio, Mann-Whitney, and binomial tests were first applied followed by logistic regressions. Results: Thoracic breathing (p=0.04), using of accessory muscles (p=0.03) and reductions in flexibility (p=0.001) increased the chances of an individual being a mouth breather when compared to nasal breathers. Subsequently, using of accessory muscles decreased the chances of snoring among mouth breathers (p=0.03); the presence of shoulder asymmetry reduced the chances of experiencing quiet sleep (p=0.05) and increased the chances of coughing or being tired when playing or running (p=0.008). Finally, forward head position reduced the chances of waking up at night (p=0.04) and experiencing shortness of breath (p=0.05). Conclusions: Respiratory and postural adaptations increased the chances of individuals persisting with mouth breathing. Additionally, these adaptations could be associated with mouth breathers' self-perceived quality of life. .

Ultrasound-microbubble transplantation of bone marrow stromal cells improves neurological function after forebrain ischemia in adult mice.

In this study, bone marrow stromal cells (MSCs) were transplanted into the brain of adult rats after forebrain ischemia induced by 4VO. SD rats (n = 60) were randomly divided into three groups: (I) rats (n = 20) were subjected to 4VO and transplanted with MSCs into the ischemic region using ultrasound-microbubble method, (2) rats (n = 20) were subjected to 4VO and transplanted with MSCs into the ischemic region (n = 20), and (3) 4VO alone (n = 20). Rats were sacrificed 28 days after treatment. Neurological functions of rats were evaluated by Morris Water Maze. The current findings suggest that the ultrasound microbubble transplanted MSCs survived in the ischemic brain and significantly improved functional recovery of adult rats compared to regular transplantation.

Long-term effects of post-ischaemic oestrogen on brain injury in a rat transient forebrain ischaemia model.

BACKGROUND: The current study was conducted to compare the effects of post-treatment with oestrogen on histological and neurological outcomes after short (7-day) and long (28-day) recovery periods in rats subjected to transient forebrain ischaemia. METHODS: Male Sprague-Dawley rats were randomly assigned to one of five groups: vehicle (7-day recovery period), vehicle (28-day recovery period), oestrogen (17ß-estradiol 200 µg/kg, 7-day), oestrogen (17ß-estradiol 200 µg /kg, 28-day), or sham surgical (n = 8 in each group). After forebrain ischaemia was induced with bilateral carotid artery occlusion and haemorrhagic hypotension (mean arterial pressure = 40 mmHg) for 10 min, the brain was reperfused for 7 or 28 days. Either 17ß-estradiol or vehicle was injected intravenously during the initial 2 min of reperfusion. To evaluate histological damage, the number of intact neurons per 1 mm in the hippocampal CA1 subfield was counted at 7 or 28 days after transient forebrain ischaemia. RESULTS: At 7 days after ischaemia, the number of intact neurons in the hippocampal CA1 subfield was significantly greater in the oestrogen group [57.5 (46.5)/mm: median (interquartile range)] than in the vehicle group [10 (19.5) /mm; P = 0.014]. However, there was no difference between groups at 28 days after ischaemia [vehicle: 11 (20)/mm vs. oestrogen: 6 (11)/mm]. The neurological deficit scores in the oestrogen and vehicle groups were not different from the sham group at any point post-ischaemia. CONCLUSION: The current study indicates that post-ischaemic administration of oestrogen provided short-term but not long-term neuroprotective effects in transient forebrain ischaemia in rats.

Overexpression of vascular endothelial growth factor in the germinal matrix induces neurovascular proteases and intraventricular hemorrhage.

Intracranial hemorrhage in preterm neonates may result in neonatal mortality and functional disabilities, but its pathogenic mechanisms are poorly defined and better therapies are needed. We used a tetracycline-regulated transgenic system to test whether the induction of vascular endothelial growth factor (VEGF) in the germinal matrix leads to intracranial hemorrhage. This genetic strategy initially induced a dense network of loosely adjoined endothelial cells and pericytes near lateral ventricles, similar to the immature vascular rete in human fetal brains. Yet, this rich vascular network transformed into low-vasculature patches correlated with hemorrhage and caspase-3 activation near birth. Gene expression and biochemical analyses suggested that downstream mediators of VEGF in this network include transcriptional factors ETS1 and HIF2α (hypoxia-inducible factor 2α), components of the PDGFß (platelet-derived growth factor ß) and TGFß (transforming growth factor-ß) receptor signaling pathways, matrix metalloproteinase-9 (MMP-9), and cathepsins. Prenatal administration of glucocorticoids markedly reduced mortality and cerebral hemorrhage in mutant animals, as in human neonates. This protective effect was not due to blocking vasculogenesis, but was instead associated with inhibition of neurovascular proteases, notably MMP-9, cathepsin B, and caspase-3. Collectively, these results support a causative role of VEGF in perinatal cerebral hemorrhage and implicate its downstream proteases as potential therapeutic targets.

Chronological changes and effects of AMP-activated kinase in the hippocampal CA1 region after transient forebrain ischemia in gerbils.

OBJECTIVES: Adenosine monophosphate-activated kinase (AMPK) is an energy-specific sensor within the central nervous system. In this study, we observed AMPK and its phosphorylated form (pAMPK) in the hippocampal CA1 region after 5 minutes of transient forebrain ischemia. In addition, we also investigated the effects of Compound C, an AMPK inhibitor, against ischemic damage in gerbils. METHODS: Adenosine monophosphate-activated kinase and pAMPK immunoreactivity was observed in the hippocampal CA1 region at various time points after ischemia and Compound C was intraperitoneally administered to gerbils immediately after reperfusion and the animals were sacrificed at 5 days after ischemia/reperfusion. RESULTS: Adenosine monophosphate-activated kinase immunoreactivity was transiently increased in the hippocampal CA1 region 1-2 days after ischemia/reperfusion, while AMPK immunoreactivity was almost undetectable in the stratum pyramidale of the CA1 region 4-7 days after ischemia/reperfusion. The administration of Compound C caused a dose-dependent decrease in the ischemia-induced hyperactive behavior, the depletion of ATP, and lactate accumulation in the hippocampal CA1 region within 24 hours after ischemia/reperfusion. In addition, the administration of Compound C decreased reactive gliosis (astrocytes and microglia) and increased the number of cresyl violet-positive neurons when compared to the vehicle-treated group at 5 days post-ischemia/reperfusion. CONCLUSION: These results suggest that AMPK is transiently phosphorylated following forebrain ischemia in the hippocampal CA1 region and inhibition of AMPK has neuroprotective effects against ischemic damage through the reduction of ATP depletion and lactate accumulation in the hippocampal CA1 region.

Tsc1 (hamartin) confers neuroprotection against ischemia by inducing autophagy.

Previous attempts to identify neuroprotective targets by studying the ischemic cascade and devising ways to suppress it have failed to translate to efficacious therapies for acute ischemic stroke. We hypothesized that studying the molecular determinants of endogenous neuroprotection in two well-established paradigms, the resistance of CA3 hippocampal neurons to global ischemia and the tolerance conferred by ischemic preconditioning (IPC), would reveal new neuroprotective targets. We found that the product of the tuberous sclerosis complex 1 gene (TSC1), hamartin, is selectively induced by ischemia in hippocampal CA3 neurons. In CA1 neurons, hamartin was unaffected by ischemia but was upregulated by IPC preceding ischemia, which protects the otherwise vulnerable CA1 cells. Suppression of hamartin expression with TSC1 shRNA viral vectors both in vitro and in vivo increased the vulnerability of neurons to cell death following oxygen glucose deprivation (OGD) and ischemia. In vivo, suppression of TSC1 expression increased locomotor activity and decreased habituation in a hippocampal-dependent task. Overexpression of hamartin increased resistance to OGD by inducing productive autophagy through an mTORC1-dependent mechanism.

Polyunsaturated fatty acids and blood circulation in the forebrain during a mental arithmetic task.

The effects of polyunsaturated fatty acids on human cerebral blood oxygenation have yet to be extensively investigated. In this study, healthy participants (14 men, 40 women) aged between 20 and 49 years were recruited. All female participants entered the trial at the start of their menstrual cycle. Blood was sampled before measuring cerebral blood oxygenation in the prefrontal cortex (PFC) and prior to administering two kinds of questionnaires, the Profile of Mood States (POMS) and a questionnaire regarding participants' arousal level. Blood oxygenation in the PFC was continuously monitored immediately before and during the Uchida-Kraepelin Performance (UKP) test as a mental arithmetic task. Changes in the tissue oxygenation index (the ratio of oxyhemoglobin to oxyhemoglobin+deoxyhemoglobin; TOI, a simplified index for cerebral blood circulation) were measured by near-infrared spectroscopy. Multiple regression analysis was performed with sex, age, smoking and drinking as confounding factors. Eicosapentaenoic acid (EPA) was positively associated with TOI, which was positively associated with arousal level and inversely associated with negative mood (POMS). EPA and docosahexaenoic acid were inversely associated with depression-dejection (POMS) and positively associated with arousal level and overall performance in the UKP test. We suggest that EPA might increase the oxygenation level in the PFC, in turn improving various psychological parameters and performance.

EphB4 is developmentally and differentially regulated in blood vessels throughout the forebrain neurogenic niche in the mouse brain: Implications for vascular remodeling.

Neurogenesis is a process influenced by environmental cues that create highly specific functional niches. Recently, the role of blood vessels in the maintenance and functioning of neurogenic niches during development and in adult life has been hallmarked. In addition to their trophic support for the highly demanding neurogenic process, blood vessels regulate neuroblast differentiation and migration and define functional domains. Since neurogenesis along the forebrain neurogenic niche (FNN) is a multistage process, in which neuroblast proliferation, differentiation and migration are spatially restricted to specific locations; we evaluated the structural features of vascular beds that support these processes during critical time points in their development. Additionally, we studied the molecular identity of the endothelial components of vascular beds using the expression of the venous marker EphB4. Our results show that blood vessels along the FNN: 1) are present very early in development; 2) define the borders of the FNN since early developmental stages; 3) experience constant remodeling until achieving their mature structure; 4) show venous features during perinatal developmental times; and 5) down-regulate their EphB4 expression as development proceeds. Collectively, our results describe the formation of the intricate vascular network that may support neurogenesis along the FNN and show that blood vessels along this neurogenic niche are dynamic entities that experience significant structural and molecular remodeling throughout development.

Delta opioid peptide [D-Ala2, D-Leu5] enkephalin (DADLE) triggers postconditioning against transient forebrain ischemia.

Preconditioning with selective delta opioid peptide [d-Ala2, d-Leu5] enkephalin (DADLE) provides ischemic tolerance following transient forebrain ischemia in rats. However, whether DADLE postconditioning retains its neuroprotective efficacy and the underlying molecular mechanism in ischemic brain is largely unknown. We investigated DADLE postconditioning protection of hippocampal CA1 neurons against transient forebrain ischemia. 6 days after being implanted with cannula at the right lateral ventricle, rats underwent 10 min of forebrain ischemia by four vessel occlusion. Hippocampal CA1 neuronal survival and degeneration were measured in the hippocampi of rats at 3 days after ischemia. The behavioral and cognitive improvements of DADLE treatment in rats were also evaluated on days 5-9 using open-field and Morris water maze tests. The results showed that DADLE at doses of 0.25 and 2.5 nmol, but not 25 nmol, could significantly protect CA1 neurons against ischemia/reperfusion injury. Co-administration with the delta-opioid receptor antagonist naltrindole or pretreatment with the Akt antagonist LY294002 completely abolished the DADLE postconditioning effect. Furthermore, DADLE postconditioning exhibited cognitive benefits in rats with transient forebrain ischemia. The study thus suggested a therapeutic opportunity of postconditioning neuroprotection by DADLE and also provided important information in understanding the mechanism of DADLE action in the ischemic brain.

Essential regulation of CNS angiogenesis by the orphan G protein-coupled receptor GPR124.

The orphan G protein-coupled receptor (GPCR) GPR124/tumor endothelial marker 5 is highly expressed in central nervous system (CNS) endothelium. Here, we show that complete null or endothelial-specific GPR124 deletion resulted in embryonic lethality from CNS-specific angiogenesis arrest in forebrain and neural tube. Conversely, GPR124 overexpression throughout all adult vascular beds produced CNS-specific hyperproliferative vascular malformations. In vivo, GPR124 functioned cell-autonomously in endothelium to regulate sprouting, migration, and developmental expression of the blood-brain barrier marker Glut1, whereas in vitro, GPR124 mediated Cdc42-dependent directional migration to forebrain-derived, vascular endothelial growth factor-independent cues. Our results demonstrate CNS-specific angiogenesis regulation by an endothelial receptor and illuminate functions of the poorly understood adhesion GPCR subfamily. Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies.

Age-dependent vascular changes induced by status epilepticus in rat forebrain: implications for epileptogenesis.

Brain inflammation, angiogenesis and increased blood-brain barrier (BBB) permeability occur in adult rodent and human epileptogenic brain tissue. We addressed the role of these events in epileptogenesis using a developmental approach since the propensity to develop spontaneous seizures, therefore the induction of epileptogenesis, is age-dependent and increases with brain maturation. Inflammation, angiogenesis and BBB permeability were studied in postnatal day (PN)9 and PN21 rats, 1 week and 4 months after pilocarpine-induced status epilepticus. Brain inflammation was evaluated by interleukin(IL)-1beta immunohistochemistry; angiogenesis was quantified by measuring the density of microvessels identified by an anti-laminin antibody or by the intraluminal signal of FITC-albumin; BBB integrity was assessed by extravascular IgG immunostaining or detection of parenchymal extravasation of FITC-albumin. Neither inflammation nor angiogenesis or changes in BBB permeability were detected in PN9 rats after status epilepticus, and these rats did not develop spontaneous seizures in adulthood as assessed by video-EEG monitoring. Differently, status epilepticus in PN21 rats induced chronic inflammation, angiogenesis and BBB leakage in the hippocampus in 62% of rats, while in the remaining rats only transient inflammation in forebrain was observed. Epilepsy developed in about 62% of PN21 rats exposed to SE and these epileptic rats showed the three phenomena concomitantly in the hippocampus. PN21 rats that did not develop epilepsy 4 months after status epilepticus, as assessed by video-EEG monitoring, they did not show inflammation, angiogenesis or BBB damage in forebrain at this time. Our data show that age-dependent vascular changes and brain inflammation induced by status epilepticus are associated with epileptogenesis, suggesting that these phenomena are implicated in the mechanisms underlying the occurrence of spontaneous seizures.

Fructose-1,6-bisphosphate and fructose-2,6-bisphosphate do not influence brain carbohydrate or high-energy phosphate metabolism in a rat model of forebrain ischemia.

Phosphorylated fructose compounds have been reported to lessen neuronal injury in in vitro models of hypoxia and in vivo models of ischemia. Although a variety of mechanisms have been proposed to account for this finding, it is unknown if intracellular uptake and incorporation of these compounds into the glycolytic pathway contribute to the benefit. We evaluated phosphorylated fructose administration in an adult rat model of transient, near-complete cerebral ischemia to determine its impact on brain metabolism before, during, and after ischemia. Fifty-four pentobarbital anesthetized rats were randomly assigned to receive IV infusions of either fructose-1,6-bisphosphate, fructose-2,6-bisphosphate, or 0.9% saline. After 2 hours of infusion, 18 rats (6/treatment group) were subjected to brain harvesting before any ischemia, 18 additional rats had brain harvesting at the completion of 10 minutes of forebrain ischemia (2-vessel occlusion plus induced hypotension), and 18 rats had harvesting after ischemia and 15 minutes of reperfusion. Cortical brain samples were analyzed for ATP, ADP, AMP, phosphocreatine, glucose, and glycogen. When compared with placebo, neither phosphorylated fructose compound altered preischemic, intraischemic, or postischemic concentrations of brain high-energy phosphates, glucose, glycogen, or lactate, nor did they influence the intraischemic metabolism of endogenous brain glucose or glycogen. On the basis of these results, we conclude that mechanisms other than augmented carbohydrate metabolism are responsible for previous reports of neuronal protection by the bisphosphonates.

Differential regulation of osteopontin receptors, CD44 and the alpha(v) and beta(3) integrin subunits, in the rat hippocampus following transient forebrain ischemia.

We have examined the spatiotemporal regulation of CD44 and the alpha(v)beta(3) integrin subunits, which have been identified as receptors for osteopontin (OPN), in the rat hippocampus following transient forebrain ischemia. Immunoreactivity for CD44 and the integrin subunits, alpha(v) and beta(3), showed characteristic time- and cell-dependent patterns in the ischemic hippocampus. CD44 immunoreactivity was induced at day 1 after reperfusion, reached a peak at day 3, and returned to basal levels by day 7. CD44 was induced in a subset of activated microglial cells within sites of intense neural damage, and the concomitant induction of OPN and CD44 was observed in the same cells in the ischemic hippocampus. In contrast, increased immunoreactivity for alpha(v) and beta(3), which shared overlapping expression patterns in the ischemic hippocampus, occurred in the majority of reactive astrocytes and only a few microglia at day 3 after reperfusion, and was sustained for more than 2 weeks. Immunoreactivity for both integrin subunits colocalized with OPN immunoreactivity in reactive astrocytes, and OPN immunoreactivity was also diffusely localized over the extracellular matrix around the reactive astrocytes. These data indicated that the rapid and transient induction of CD44 and OPN occurred in activated microglia/macrophages, whereas the long-lasting induction of alpha(v) and beta(3) integrin subunits and OPN occurred in reactive astrocytes, suggesting that the multifunctional role of OPN in the ischemic brain may be attributed, in part, to a time- and cell-dependent interaction with CD44 or integrin alpha(v)beta(3).

Specific subtypes of cortical GABA interneurons contribute to the neurovascular coupling response to basal forebrain stimulation.

Neurovascular coupling, or the tight coupling between neuronal activity and regional cerebral blood flow (CBF), seems largely driven by the local processing of incoming afferent signals within the activated area. To test if cortical gamma-aminobutyric acid (GABA) interneurons-the local integrators of cortical activity-are involved in this coupling, we stimulated the basalocortical pathway in vivo, monitored cortical CBF, and identified the activated interneurons (c-Fos-immunopositive) and the neuromediators involved in this response. Basal forebrain (BF) stimulation induced ipsilateral increases in CBF and selective activation of layers II to VI somatostatin- and/or neuropeptide Y-containing, as well as layer I GABA interneurons. Nitric oxide synthase interneurons displayed weak bilateral activation, whereas vasoactive intestinal polypeptide- or acetylcholine (ACh)-containing GABA interneurons were not activated. Selective cholinergic deafferentation indicated that ACh released from stimulated BF afferents triggered the CBF response, but the latter was mediated, in part, by the local release of GABA from cholinoceptive cortical interneurons, and through GABA-A receptor-mediated transmission. These data show that activation of specific subsets of GABA interneurons and their GABA-A-mediated effects on neuronal, vascular, and/or astroglial targets are necessary for the full expression of the hemodynamic response to BF stimulation. Further, these findings highlight the importance of understanding the cellular networks and circuitry that underlie hemodynamic signals, as only specific subsets of neurons may be activated by a given stimulus, depending on the afferent inputs they receive and integrate.

Postischemic administration of Z-Ligustilide ameliorates cognitive dysfunction and brain damage induced by permanent forebrain ischemia in rats.

Previous studies have demonstrated that Z-Ligustilide (LIG), a characterized phthalide constituent present in numerous medical Umbelliferae plants, has significant neuroprotective effects in transient forebrain ischemia and permanent cerebral focal ischemia. The present study further investigated the effect of LIG on chronic cerebral hypoperfusion. Male Wistar rats were subjected to permanent ligation of both common carotid arteries (2VO). On Days 8-12 postsurgery, rat cognition was assessed in the Morris water maze. Rats with significantly impaired acquisition of spatial information were randomly allocated to three groups and orally administered LIG (10 or 40 mg/kg/day) or volume-matched vehicle on Days 13-40 post-2VO surgery. The sham-operated group served as controls. After long-term treatment with LIG, the impaired animals' behavioral, biochemical, and histopathological features were examined. Compared to the sham-operated group, significant cognitive impairment was observed in the vehicle-treated group 40 days after 2VO. Shortened mean escape latency was detected in the Morris water maze in rats treated with LIG (p<0.01 vs. vehicle-treated group) during the same trial days. Chronic 2VO-induced pathological changes included neuronal loss and an increase of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the hippocampus. These effects were prevented with LIG treatment (p<0.01 vs. vehicle-treated group). LIG also significantly reduced malondialdehyde levels and increased superoxide dismutase activity in ischemic brain tissue (p<0.05 and p<0.01 vs. vehicle-treated group). In addition, LIG significantly increased choline acetyltransferase activity and inhibited acetylcholinesterase activity in ischemic brain tissues (p<0.05 and p<0.01 vs. vehicle-treated group). The present data demonstrate that LIG significantly prevented chronically hypoperfused cognitive deficits and brain damage at least partly through an antioxidant effect and improved cholinergic activity. The present findings suggest that LIG may have therapeutic potential in treating vascular dementia and cerebrovascular insufficiency.

Relation of postischemic delayed hypoperfusion and cerebral edema after transient forebrain ischemia.

Postischemic delayed hypoperfusion (PDH) is based on the imbalance between local vasodilators and vasoconstrictors. We evaluated the time course of cerebral blood flow and cerebral specific gravity representing cerebral edema after transient forebrain ischemia induced by bilateral occlusion of the common carotid arteries in anesthetized gerbils to determine whether PDH is a significant factor in development of cerebral edema. PDH appeared 45 minutes after reperfusion followed by the increase of cerebral edema. Thereafter, the local cerebral blood flow recovered from PDH 24 hours after reperfusion in spite of the stable cerebral specific gravity. Furthermore, cerebral specific gravity established a linear correlation with the local cerebral blood flow 120 minutes after reperfusion in the 3 different durations of cerebral ischemia (30, 60, and 90 minutes). It is suggested that cerebral edema is not the cause in PDH development, but PDH may cause cerebral edema.

Forebrain ischemia-reperfusion simulating cardiac arrest in mice induces edema and DNA fragmentation in the brain.

Brain injury affects one-third of persons who survive after heart attack, even with restoration of spontaneous circulation by cardiopulmonary resuscitation. We studied brain injury resulting from transient bilateral carotid artery occlusion (BCAO) and reperfusion by simulating heart attack and restoration of circulation, respectively, in live C57Black6 mice. This model is known to induce neuronal death in the hippocampus, striatum, and cortex. We report the appearance of edema after transient BCAO of 60 minutes and 1 day of reperfusion. Hyperintensity in diffusion-weighted magnetic resonance imaging (MRI) was detectable in the striatum, thalamus, and cortex but not in the hippocampus. To determine whether damage to the hippocampus can be detected in live animals, we infused a T(2) susceptibility magnetic resonance contrast agent (superparamagnetic iron oxide nanoparticles [SPIONs]) that was linked to single-stranded deoxyribonucleic acid (DNA) complementary in sequence to c-fos messenger ribonucleic acid (SPION-cfos); we acquired in vivo T(2)*-weighted MRI 3 days later. SPION retention was measured as T(2)* (milliseconds) signal reduction or R(2)* value (s(-1)) elevation. We found that animals treated with 60-minute BCAO and 7-day reperfusion exhibited significantly less SPION retention in the hippocampus and cortex than sham-operated animals. These findings suggest that brain injury induced by cardiac arrest can be detected in live animals.

Transient forebrain ischemia effects FAK-coupled signaling in gerbil hippocampus.

Focal adhesion kinase (FAK) is thought to play a major role in transducing extracellular matrix (ECM)-derived survival signals into cells. The function of FAK is linked to its autophosphorylation at Tyr-397 and then recruitment of several effector molecules. Thus, modulation of FAK activity may affect several intracellular signaling pathways and may participate in a variety of pathological settings. In the present study, we investigated the effect of short-term 5 min forebrain ischemia on levels and Tyr-397 phosphorylation of focal adhesion kinase and the interaction of this enzyme with Src protein tyrosine kinase and adapter protein p130Cas, involved in FAK-mediated signaling pathway in gerbil hippocampus. The total amount of focal adhesion kinase as well as its Tyr-397 phosphorylation declined substantially between 24 and 48 h after the insult, particularly in CA1 region of hippocampus. Concomitantly, a decreased amount of FAK/Src kinase complex has been observed. These data indicate that inhibition of FAK/Src-coupled signaling pathway may participate in the ischemia-induced neuronal degeneration in gerbil hippocampus. The temporal profile of FAK down-regulation in CA1 area coincides with metalloproteinases (MMPs) activation. These results suggest that extracellular proteolysis might belong to the mechanisms which govern the FAK-coupled pathway in ischemic hippocampus.