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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mammalian cells require a constant supply of oxygen to maintain energy balance, and sustained hypoxia can result in cell death. It is therefore not surprising that sophisticated adaptive mechanisms have evolved that enhance cell survival during hypoxia. During the past few years, there have been a growing number of reports on hypoxia-induced transcription of specific genes. In this review, we describe a unique experimental approach that utilizes focused cDNA libraries coupled to microarray analyses to identify hypoxia-responsive signal transduction pathways and genes that confer the hypoxia-tolerant phenotype. We have used the subtractive suppression hybridization (SSH) method to create a cDNA library enriched in hypoxia-regulated genes in oxygen-sensing pheochromocytoma cells and have used this library to create microarrays that allow us to examine hundreds of genes at a time. This library contains over 300 genes and expressed sequence tags upregulated by hypoxia, including tyrosine hydroxylase, vascular endothelial growth factor, and junB. Hypoxic regulation of these and other genes in the library has been confirmed by microarray, Northern blot, and real-time PCR analyses. Coupling focused SSH libraries with microarray analyses allows one to specifically study genes relevant to a phenotype of interest while reducing much of the biological noise associated with these types of studies. When used in conjunction with high-throughput, dye-based assays for cell survival and apoptosis, this approach offers a rapid method for discovering validated therapeutic targets for the treatment of cardiovascular disease, stroke, and tumors.
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PMID:Functional genomics approach to hypoxia signaling. 1471 86

Sendai virus (SeV) vector-mediated gene delivery of glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) prevented the delayed neuronal death induced by transient global ischemia in gerbils, even when the vector was administered several hours after ischemia. Intraventricular administration of SeV vector directed high-level expression of the vector-encoded neurotrophic factor genes, which are potent candidates for the treatment of neurodegenerative diseases. After occlusion of the bilateral carotid arteries of gerbils, SeV vector carrying GDNF (SeV/GDNF), NGF (SeV/NGF), brain-derived neurotrophic factor (SeV/BDNF), insulin-like growth factor-1 (SeV/IGF-1) or vascular endothelial growth factor (SeV/VEGF) was injected into the lateral ventricle. Administration of SeV/GDNF, SeV/NGF or SeV/BDNF 30 min after the ischemic insult effectively prevented the delayed neuronal death of the hippocampal CA1 pyramidal neurons. Furthermore, the administration of SeV/GDNF or SeV/NGF as late as 4 or 6 h after the ischemic insult also prevented the death of these neurons. These results indicate that SeV vector-mediated gene transfer of neurotrophic factors has high therapeutic potency for preventing the delayed neuronal death induced by transient global ischemia, and provides an approach for gene therapy of stroke.
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PMID:Postischemic administration of Sendai virus vector carrying neurotrophic factor genes prevents delayed neuronal death in gerbils. 1496 Oct 67

Attention-deficit/hyperactivity disorder (AD/HD) is a common pediatric behavioral disorder associated, in part, with male preponderance and reduced regional cerebral blood flow (rCBF). However, mechanism(s) underlying male preponderance and reduced rCBF in AD/HD are unclear. The present study profiles the expression of angiogenic and hormonal factors likely to underlie these symptoms using a recently characterized AD/HD animal model, juvenile male stroke-prone spontaneously hypertensive rats (SHRSP). Because vascular endothelial growth factor (VEGF) signaling cascade and gonadal steroids are key regulators of angiogenesis and gender-based behavior, respectively, we profiled their patterns of expression in the frontal cortex of SHRSP to elucidate their roles in the genesis of AD/HD male preponderance and rCBF. Interestingly, levels of VEGF, VEGF receptors (KDR, Flt-1), endothelial nitric oxide synthase, phosphorylated Akt (pAkt), estrogen receptor-alpha, aromatase, and capillary density in sham-operated SHRSP were remarkably down-regulated, whereas androgen receptor levels were up-regulated, compared with age-matched genetic control, Wistar-Kyoto rats. Castration, estrogen, and androgen receptor antagonist (flutamide) counteracted these effects. Dihydrotestosterone, but not testosterone, reversed the beneficiary effects of castration. Estrogen receptor-beta levels remained unchanged in all groups examined. We postulate that changes in androgen metabolism that tend to up-regulate local dihydrotestosterone concentration and diminish estrogen synthesis, in the frontal cortex of juvenile male SHRSP, may lower levels and/or activity of VEGF and its signaling cascade and, subsequently, reduce rCBF. These findings could, in part, help explain the pathogenesis of reduced rCBF and male preponderance in AD/HD.
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PMID:Gonadal hormones and frontocortical expression of vascular endothelial growth factor in male stroke-prone, spontaneously hypertensive rats, a model for attention-deficit/hyperactivity disorder. 1517 44

It has been shown that vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) are upregulated in severe carotid stenosis. However, it is unknown whether carotid endarterectomy (CEA) affects serum level of these molecules. We investigated changes in concentration of VEGF and VEGFR-2 in patients undergoing carotid endarterectomy. Forty-three patients with extracranial carotid stenosis (>70%), were studied. Patients with severe vertebrobasilar stenosis, recent (<1 month) vascular event (stroke, coronary infarction, arterial thromboembolism), critical ischemia of lower extremity, recent infection, autoimmune disease or malignancy were excluded from the study. Blood samples were taken before CEA and on the second post-operative day. Thirty healthy blood donors served as a control group. We used enzyme linked immuno-absorbent assay as a method for the determination of VEGF and VEGFR-2. Pre-operative levels of VEGF (371+/-42 pg/ml) and VEGFR-2 (8424+/-356 pg/ml) were significantly elevated. There was significant decrease in both VEGF (152 pg/ml) and VEGFR-2 (1297 pg/ml) after CEA, without however reaching normal values. In asymptomatic patients and in patients with a contralateral carotid stenosis of >50%, however, the observed reduction of VEGF did not reach statistical significance. On the other hand, in the same subgroups, a major decrease of VEGFR-2 values was observed. VEGF and VEGFR-2 showed a very significant increase in serum of patients with severe carotid stenosis. These pre-operative levels decreased significantly after endarterectomy, and the changes emphasize the importance of these molecules in carotid disease progression.
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PMID:Changes in circulating levels of vascular endothelial growth factor and vascular endothelial growth factor receptor-2 after carotid endarterectomy. 1520 28

After ischemic stroke, there is neovascularization around the infarcted area, which is called penumbra. Angiogenesis and arteriogenesis are responsible for the new vessel formation. Until recently, vasculogenesis has been proved to involve mechanisms in postischemic neovascularization, which was thought to be restricted to embryonic development. New blood vessels' formation is a complex pathologic process after ischemic stroke, in which many factors are properly involved. There are factors stimulating neovascularization, such as vascular endothelial growth factor, platelet-derived growth factor, basic fibroblast growth factor and angiopoietin; there are also factors inhibiting neovascularization, such as thrombospondin. Functional recovery was found after stroke, which may contribute to angiogensis in the periinfarct tissue. Thus, therapeutic angiogenesis has been initially studied in animal models, but there is still a long way to go for therapeutic angiogenesis to be used in the treatment of stroke patient.
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PMID:[Neovascularization after ischemic stroke]. 1525 Jan 70

Hypoxia and acidosis are common features of several physiological and pathological situations, including cancer and stroke. The HIF (hypoxia-inducible factor) transcription factor plays a seminal role in orchestrating cellular responses to alterations in oxygen availability. HIF is degraded in normal oxygen tension by the VHL (von Hippel-Lindau) tumor suppressor protein but stabilized by hypoxia to activate an array of genes implicated in oxygen homeostasis including vascular endothelial growth factor. Cells respond to a comparatively mild decline in oxygen tension by converting to an anaerobic state of respiration and secreting lactic acid. We recently reported that a decrease in environmental pH triggers sequestration of VHL into the nucleolus neutralizing its ability to degrade HIF. This implies that cells have evolved a parallel mechanism of HIF activation that responds to changes in oxygen levels by sensing extracellular [H+]. Here we discuss the implications of this new VHL regulatory mechanism on oxygen homeostasis and hypoxic cell memory.
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PMID:Oxygen sensing by H+: implications for HIF and hypoxic cell memory. 1528 Jun 64

Angiogenesis is a critical component of stroke, head injury, cerebral vascular malformation development, and brain tumor growth. An understanding of the mechanisms of adult cerebral angiogenesis is fundamental to therapeutic vessel modulation for these diseases. To study angiogenesis in the central nervous system, we injected an adenoviral vector engineered to express vascular endothelial growth factor (VEGF-A164) into adult murine striatum. Vector-infected astrocytes expressed VEGF-A164 resulting in vascular permeability, hemorrhage, and the formation of greatly enlarged "mother" vessels. Subsequently, endothelial cells and pericytes lining mother vessels proliferated and assembled into glomeruloid bodies, complex cellular arrays interspersed by small vessel lumens. As VEGF-A164 expression declined, glomeruloid bodies involuted through apoptotic processes to engender numerous small daughter vessels. Characterized by modestly enlarged lumens with prominent pericyte coverage, daughter vessels were distributed with a density greater than normal cerebral vessels. Daughter vessels remained stable and patent to 16 months and represented the final stage of VEGF-A-induced cerebral angiogenesis. Together, these findings provide a mechanistic understanding of angiogenesis in cerebral disease processes. Furthermore, the long-term stability of daughter vessels in the absence of exogenous VEGF-A164 expression suggests that VEGF-A may enable therapeutic angiogenesis in brain.
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PMID:VEGF-A angiogenesis induces a stable neovasculature in adult murine brain. 1533 Mar 39

Effective therapies for stroke must interdict multiple parallel and sequential pathophysiological events. A paradigm which offers insight into multivalent but thoughtfully coordinated protective programs is ischemic preconditioning. A central hypothesis of our group and others is that pharmacological agents that activate programs of gene expression normally induced by ischemic preconditioning will be effective agents for the prevention and treatment of stroke. Inhibitors of a class of enzymes, the hypoxia inducible factor-1 (HIF-1) prolyl hydroxylases stabilize the transcriptional activator HIF-1 and activate target genes involved in compensation for ischemia, including erythropoeitin (Epo) and vascular endothelial growth factor (VEGF). Here, we review evidence suggesting that the HIF-1 prolyl hyroxylases are inhibited during ischemic preconditioning and that pharmacological inhibitors of these enzymes are viable targets for stroke therapy.
Stroke 2004 Nov
PMID:Translation of ischemic preconditioning to the patient: prolyl hydroxylase inhibition and hypoxia inducible factor-1 as novel targets for stroke therapy. 1547 13

Therapeutic angiogenesis with vascular endothelial growth factor (VEGF) is a clinically promising strategy in ischaemic disease. The pathophysiological consequences of enhanced vessel formation, however, are poorly understood. We established mice overexpressing human VEGF165 under a neuron-specific promoter, which exhibited an increased density of brain vessels under physiological conditions and enhanced angiogenesis after brain ischaemia. Following transient intraluminal middle cerebral artery (MCA) occlusions, VEGF overexpression significantly alleviated neurological deficits and infarct volume, and reduced disseminated neuronal injury and caspase-3 activity, confirming earlier observations that VEGF has neuroprotective properties. Brain swelling was not influenced in VEGF-overexpressing animals, while sodium fluorescein extravasation was moderately increased, suggesting that VEGF induces a mild blood-brain barrier leakage. To elucidate whether enhanced angiogenesis improves regional cerebral blood flow in the ischaemic brain, [14C]iodoantipyrine autoradiography was performed. Autoradiographies revealed that VEGF induces haemodynamic steal phenomena with reduced blood flow in ischaemic areas and increased flow values only outside the MCA territory. Our data demonstrate that VEGF protects neurons from ischaemic cell death by a direct action rather than by promoting angiogenesis, and suggest that strategies aiming at increasing vascular density in the whole brain, e.g. by VEGF overexpression, may worsen rather than improve cerebral haemodynamics after stroke.
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PMID:VEGF overexpression induces post-ischaemic neuroprotection, but facilitates haemodynamic steal phenomena. 1550 18

Attention-deficit/hyperactivity disorder (AD/HD) is a common pediatric behavioral disorder associated with male preponderance and reduction of regional cerebral blood flow (rCBF). However, lack of an appropriate animal model exhibiting appropriate AD/HD symptoms stands in the way of studying mechanism(s) underlying reduced rCBF and male preponderance. Our group has been investigating the suitability of juvenile male stroke-prone spontaneously hypertensive rats (SHRSP), a substrain of the commonly used AD/HD animal model SHR, as a model for AD/HD because, unlike SHR, SHRSP displays cognitive impairment and male preponderance. Our more recent studies revealed alterations in the synthesis of sex steroid hormones and angiogenic factors in the frontal cortex of male SHRSP compared to the genetic control WKY. Based on these observations, the present study utilizes laser-Doppler flowmetry, histochemistry, enzyme immunoassay, immunoblotting, and real-time PCR to characterize and compare the patterns of regional cerebral blood flow and synthesis of angiogenic molecules [basic fibroblast growth factor; nitric oxide synthase isoforms (endothelial, neuronal and inducible); vascular endothelial growth factor (VEGF) and its signaling molecules (VEGF receptors, phosphorylated Akt, endothelial nitric oxide synthase eNOS] between male SHRSP and SHR. Overall, consistent with our previous data showing alteration in VEGF/Akt/NO signaling, there was a marked reduction in the profile of rCBF (35%) and angiogenic factors of SHRSP, compared to age-matched genetic control Wistar-Kyoto rats (WKY) and SHR. We conclude that, unlike SHR, the profiles of rCBF and angiogenic factors in SHRSP are altered in juvenile male. Thus, SHRSP appears to be a more suitable animal model for studying changes in rCBF in AD/HD.
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PMID:Characterization of regional cerebral blood flow and expression of angiogenic growth factors in the frontal cortex of juvenile male SHRSP and SHR. 1557 67


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