Orhan Altay

Fingolimod reduces cerebral lymphocyte infiltration in experimental models of rodent intracerebral hemorrhage.

T-lymphocytes promote cerebral inflammation, thus aggravating neuronal injury after stroke. Fingolimod, a sphingosine 1-phosphate receptor analog, prevents the egress of lymphocytes from primary and secondary lymphoid organs. Based on these findings, we hypothesized fingolimod treatment would reduce the number of T-lymphocytes migrating into the brain, thereby ameliorating cerebral inflammation following experimental intracerebral hemorrhage (ICH). We investigated the effects of fingolimod in two well-established murine models of ICH, implementing intrastriatal infusions of either bacterial collagenase (cICH) or autologous blood (bICH). Furthermore, we tested the long term neurological improvements by Fingolimod in a collagenase-induced rat model of ICH. Fingolimod, in contrast to vehicle administration alone, improved neurological functions and reduced brain edema at 24 and 72 h following experimental ICH in CD-1 mice (n=103; p<0.05). Significantly fewer lymphocytes were found in blood and brain samples of treated animals when compared to the vehicle group (p<0.05). Moreover, fingolimod treatment significantly reduced the expression of intercellular adhesion molecule-1 (ICAM-1), interferon-γ (INF-γ), and interleukin-17 (IL-17) in the mouse brain at 72 h post-cICH (p<0.05 compared to vehicle). Long-term neurocognitive performance and histopathological analysis were evaluated in Sprague-Dawley rats between 8 and 10 weeks post-cICH (n=28). Treated rats showed reduced spatial and motor learning deficits, along with significantly reduced brain atrophy and neuronal cell loss within the basal ganglia (p<0.05 compared to vehicle). We conclude that fingolimod treatment ameliorated cerebral inflammation, at least to some extent, by reducing the availability and subsequent brain infiltration of T-lymphocytes, which improved the short and long-term sequelae after experimental ICH in rodents.

Transition of research focus from vasospasm to early brain injury after subarachnoid hemorrhage.

Subarachnoid hemorrhage is a devastating disease that can be difficult to manage. Not only is the initial bleeding and rebleeding associated with high mortality, but a large fraction of patients also develop a delayed neurological deficit even when the aneurysm was successfully secured with clipping or coiling. Past research effort has traditionally been focused on vasospasm, which was conceived to be the sole factor for delayed neurological deficit. The failure of anti‐vasospastic drugs to improve outcome in clinical trials has brought into focus the significance of early brain injury. The immediate events associated with subarachnoid hemorrhage, including increased intracranial pressure, decreased cerebral blood flow and global ischemia initiate a cascade of pathological changes that occur before the onset of delayed vasospasm. These pathological changes in the very early stage of the hemorrhage propagate and cause blood–brain barrier disruption, inflammation, oxidative stress and cell death. Focusing only on the treatment of vasospasm with complete disregard for early brain injury is insufficient for the management of subarachnoid hemorrhage. Instead, a therapeutic intervention has to aim at stopping the molecular cascades of early brain injury that may lead to long‐term deficits in addition to vasospasm. We review the pathological mechanisms of early brain injury, which may reveal new therapeutic avenues that can be exploited to serve as combination therapy with anti‐vasospasm medications in the future.

Apoptotic Mechanisms for Neuronal Cells in Early Brain Injury After Subarachnoid Hemorrhage

OBJECTS The major causes of death and disability in subarachnoid hemorrhage (SAH) may be early brain injury (EBI) and cerebral vasospasm. Although cerebral vasospasm has been studied and treated by a lot of drugs, the outcome is not improved even if vasospasm is reversed. Based on these data, EBI is considered a primary target for future research, and apoptosis may be involved in EBI after experimental SAH. METHODS We reviewed the published literature about the relationship between SAH induced EBI and apoptosis in PubMed. RESULT Most available information can be obtained from the endovascular filament perforation animal model. After onset of SAH, intracranial pressure is increased and then cerebral blood flow is reduced. Many factors are involved in the mechanism of apoptotic cell death in EBI after SAH. In the neuronal cells, both intrinsic and extrinsic pathways of apoptosis can occur. Some antiapoptotic drugs were studied and demonstrated a protective effect against EBI after SAH. However, apoptosis in EBI after SAH has been little studied and further studies will provide us more beneficial findings. CONCLUSIONS The study of apoptosis in EBI after experimental SAH may give us new therapies for SAH.

Isoflurane Attenuates Blood–Brain Barrier Disruption in Ipsilateral Hemisphere After Subarachnoid Hemorrhage in Mice

Background and Purpose— We examined effects of isoflurane, volatile anesthetics, on blood–brain barrier disruption in the endovascular perforation model of subarachnoid hemorrhage (SAH) in mice. Methods— Animals were assigned to sham-operated, SAH+vehicle–air, SAH+1%, or 2% isoflurane groups. Neurobehavioral function, brain water content, Evans blue dye extravasation, and Western blotting for sphingosine kinases, occludin, claudin-5, junctional adhesion molecule, and vascular endothelial cadherin were evaluated at 24 hours post-SAH. Effects of sphingosine kinase (N,N-dimethylsphingosine) or sphingosine-1-phosphate receptor-1/3 (S1P1/3) inhibitors (VPC23019) on isofluranes action were also examined. Results— SAH aggravated neurological scores, brain edema, and blood–brain barrier permeability, which were prevented by 2% but not 1% isoflurane posttreatment. Two percent isoflurane increased sphingosine kinase-1 expression and prevented a post-SAH decrease in expressions of the blood–brain barrier-related proteins. Both N,N-dimethylsphingosine and VPC23019 abolished the beneficial effects of isoflurane. Conclusions— Two percent isoflurane can suppress post-SAH blood–brain barrier disruption, which may be mediated by sphingosine kinase 1 expression and sphingosine-1-phosphate receptor-1/3 activation.

α7 Nicotinic Acetylcholine Receptor Agonism Confers Neuroprotection Through GSK-3β Inhibition in a Mouse Model of Intracerebral Hemorrhage

Background and Purpose— Perihematomal edema formation and consequent cell death contribute to the delayed brain injury evoked by intracerebral hemorrhage (ICH). We aimed to evaluate the effect of &agr;7 nicotinic acetylcholine receptor (&agr;7nAChR) stimulation on behavior, brain edema, and neuronal apoptosis. Furthermore, we aimed to determine the role of the proapoptotic glycogen synthase kinase-3&bgr; (GSK-3&bgr;) after experimental ICH. Methods— Male CD-1 mice (n=109) were subjected to intracerebral infusion of autologous blood (n=88) or sham surgery (n=21). ICH animals received vehicle administration, 4 or 12 mg/kg of &agr;7nAChR agonist PHA-543613, 12 mg/kg of &agr;7nAChR agonist PNU-282987, 6 mg/kg of &agr;7nAChR antagonist methyllycaconitine (MLA), 15 &mgr;g/kg of phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, or PHA-543613 combined with MLA or wortmannin. Behavioral deficits and brain water content were evaluated at 24 and 72 hours after surgery. Western blotting and immunofluorescence staining were used for the quantification and localization of activated Akt (p-Akt), GSK-3&bgr; (p-GSK-3&bgr;), and cleaved caspase-3 (CC3). Neuronal cell death was quantified through terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling (TUNEL). Results— &agr;7nAChR stimulation improved neurological outcome and reduced brain edema at 24 and 72 hours after surgery (P<0.05 compared with vehicle). Furthermore, PHA-543613 treatment increased p-Akt and decreased p-GSK-3&bgr; and CC3 expressions in the ipsilateral hemisphere (P<0.05, respectively), which was reversed by MLA and wortmannin. P-Akt, p-GSK-3&bgr;, and CC3 were generally localized in neurons. PHA-543613 reduced neuronal cell death in the perihematomal area (P<0.05). Conclusions— &agr;7nAChR stimulation improved functional and morphological outcomes after experimental ICH in mice. PHA-543613 reduced the expression of proapoptotic GSK-3&bgr; through the PI3K-Akt signaling pathway.

Etiology of stroke and choice of models

Animal models of stroke contribute to the development of better stroke prevention and treatment through studies investigating the pathophysiology of different stroke subtypes and by testing promising treatments before trials in humans. There are two broad types of animal models: those in which stroke is induced through artificial means, modeling the consequences of a vascular insult but not the vascular pathology itself; and those in which strokes occur spontaneously. Most animal models of stroke are in rodents due to cost, ethical considerations, availability of standardized neurobehavioral assessments, and ease of physiological monitoring. While there are similarities in cerebrovascular anatomy and pathophysiology between rodents and humans, there are also important differences, including brain size, length and structure of perforating arteries, and gray to white matter ratio, which is substantially lower in humans. The wide range of rodent models of stroke includes models of global and focal ischemia, and of intracerebral and sub-arachnoid hemorrhage. The most widely studied model of spontaneous stroke is the spontaneously hypertensive stroke-prone rat, in which the predominant lesions are small subcortical infarcts resulting from a vascular pathology similar to human cerebral small vessel disease. Important limitations of animal models of stroke – they generally model only certain aspects of the disease and do not reflect the heterogeneity in severity, pathology and comorbidities of human stroke – and key methodological issues (especially the need for adequate sample size, randomization, and blinding in treatment trials) must be carefully considered for the successful translation of pathophysiological concepts and therapeutics from bench to bedside.

Nasal Administration of Recombinant Osteopontin Attenuates Early Brain Injury After Subarachnoid Hemorrhage

Background and Purpose— Neuronal apoptosis is a key pathological process in subarachnoid hemorrhage (SAH)–induced early brain injury. Given that recombinant osteopontin (rOPN), a promising neuroprotectant, cannot pass through the blood–brain barrier, we aimed to examine whether nasal administration of rOPN prevents neuronal apoptosis after experimental SAH. Methods— Male Sprague–Dawley rats (n=144) were subjected to the endovascular perforation SAH model. rOPN was administered via the nasal route and neurological scores as well as brain water content were evaluated at 24 and 72 hours after SAH induction. The expressions of cleaved caspase-3, phosphorylated focal adhesion kinase (FAK), and phosphorylated Akt were examined using Western blot analysis. Neuronal cell death was demonstrated with terminal deoxynucleotid transferase-deoxyuridine triphosphate (dUTP) nick end labeling. We also administered FAK inhibitor 14 and phosphatidylinositol 3-kinase inhibitor, Wortmannin, prior to rOPN to establish its neuroprotective mechanism. ELISA was used to measure rOPN delivery into the cerebrospinal fluid. Results— Cerebrospinal fluid level of rOPN increased after its nasal administration. This was associated with improved neurological scores and reduced brain edema at 24 hours after SAH. rOPN increased phosphorylated FAK and phosphorylated Akt expressions and decreased caspase-3 cleavage, resulting in attenuation of neuronal cell death within the cerebral cortex. These effects were abolished by FAK inhibitor 14 and Wortmannin. Conclusions— Nasal administration of rOPN decreased neuronal cell death and brain edema and improved the neurological status in SAH rats, possibly through FAK–phosphatidylinositol 3-kinase–Akt–induced inhibition of capase-3 cleavage.

Isoflurane delays the development of early brain injury after subarachnoid hemorrhage through sphingosine-related pathway activation in mice

Objective:Isoflurane, a volatile anesthetic agent, has been recognized for its potential neuroprotective properties and has antiapoptotic effects. We examined whether isoflurane posttreatment is protective against early brain injury after subarachnoid hemorrhage and determined whether this effect needs sphingosine-related pathway activation. Design:Controlled in vivo laboratory study. Setting:Animal research laboratory. Subjects:One hundred seventy-nine 8-wk-old male CD-1 mice weighing 30–38 g. Interventions:Subarachnoid hemorrhage was induced in mice by endovascular perforation. Animals were randomly assigned to sham-operated, subarachnoid hemorrhage–vehicle, and subarachnoid hemorrhage+2% isoflurane. Neurobehavioral function and brain edema were evaluated at 24 and 72 hrs. The expression of sphingosine kinase, phosphorylated Akt, and cleaved caspase-3 was determined by Western blotting and immunofluorescence. Neuronal cell death was examined by terminal deoxynucleotidyl transferase–mediated uridine 5′-triphosphate-biotin nick end-labeling staining. Effects of a sphingosine kinase inhibitor N, N-dimethylsphingosine or a sphingosine 1 phosphate receptor inhibitor VPC23019 on isoflurane’s protective action against postsubarachnoid hemorrhage early brain injury were also examined. Measurements and Main Results:Isoflurane significantly improved neurobehavioral function and brain edema at 24 hrs but not 72 hrs after subarachnoid hemorrhage. At 24 hrs, isoflurane attenuated neuronal cell death in the cortex, associated with an increase in sphingosine kinase 1 and phosphorylated Akt, and a decrease in cleaved caspase-3. The beneficial effects of isoflurane were abolished by N, N-dimethylsphingosine and VPC23019. Conclusions:Isoflurane posttreatment delays the development of postsubarachnoid hemorrhage early brain injury through antiapoptotic mechanisms including sphingosine-related pathway activation, implying its use for anesthesia during acute aneurysm surgery or intervention.

Rodent neonatal germinal matrix hemorrhage mimics the human brain injury, neurological consequences, and post-hemorrhagic hydrocephalus

Germinal matrix hemorrhage (GMH) is the most common neurological disease of premature newborns. GMH causes neurological sequelae such as cerebral palsy, post-hemorrhagic hydrocephalus, and mental retardation. Despite this, there is no standardized animal model of spontaneous GMH using newborn rats to depict the condition. We asked whether stereotactic injection of collagenase type VII (0.3 U) into the ganglionic eminence of neonatal rats would reproduce the acute brain injury, gliosis, hydrocephalus, periventricular leukomalacia, and attendant neurological consequences found in humans. To test this hypothesis, we used our neonatal rat model of collagenase-induced GMH in P7 pups, and found that the levels of free-radical adducts (nitrotyrosine and 4-hyroxynonenal), proliferation (mammalian target of rapamycin), inflammation (COX-2), blood components (hemoglobin and thrombin), and gliosis (vitronectin and GFAP) were higher in the forebrain of GMH pups, than in controls. Neurobehavioral testing showed that pups with GMH had developmental delay, and the juvenile animals had significant cognitive and motor disability, suggesting clinical relevance of the model. There was also evidence of white-matter reduction, ventricular dilation, and brain atrophy in the GMH animals. This study highlights an instructive animal model of the neurological consequences after germinal matrix hemorrhage, with evidence of brain injuries that can be used to evaluate strategies in the prevention and treatment of post-hemorrhagic complications.

Preservation of Tropomyosin-Related Kinase B (TrkB) Signaling by Sodium Orthovanadate Attenuates Early Brain Injury After Subarachnoid Hemorrhage in Rats

Background and Purpose— Recent studies reported that apoptosis was involved in the pathogenesis of early brain injury after subarachnoid hemorrhage (SAH). The aim of this study was to examine whether sodium orthovanadate (SOV) prevents post-SAH apoptosis by modulating growth factors and its downstream receptor tyrosine kinases. Method— Rats were operated on with the endovascular perforation model. SAH animals were treated with vehicle, 3 mg/kg and 10 mg/kg SOV, and evaluated regarding neurofunction and brain edema. The expression of growth factors such as mature brain-derived neurotrophic factor, insulin-like growth factor-1, and vascular endothelial growth factor and phosphorylation of tropomyosin-related kinase B, which is a receptor tyrosine kinase for brain-derived neurotrophic factor and the downstream pathway in antiapoptosis, was examined by Western blot analysis. Neuronal cell death was measured with terminal deoxynucleotidyl transferase-mediated uridine 5′-triphosphate-biotin nick end-labeling staining. We also administered K252a, a tropomyosin-related kinase B antagonist, to examine the mechanisms for neuroprotective effects by SOV. Results— SOV significantly improved neurofunction and reduced brain edema after SAH. SOV increased mature brain-derived neurotrophic factor and prevented post-SAH tropomyosin-related kinase B inactivation and caspase-3 activation, resulting in attenuation of neuronal cell death in the cortex and hippocampal CA1 region. Preinjection of K252a abolished the beneficial effects of SOV. Conclusions— The current study showed that brain-derived neurotrophic factor-induced tropomyosin-related kinase B activation by SOV was necessary for protection against early brain injury after SAH.