Hypoxia-ischemia induces DNA synthesis without cell proliferation in dying neurons in adult rodent brain

Recent studies suggest that postmitotic neurons can reenter the cell cycle as a prelude to apoptosis after brain injury. However, most dying neurons do not pass the G1/S-phase checkpoint to resume DNA synthesis. The specific factors that trigger abortive DNA synthesis are not characterized. Here we show that the combination of hypoxia and ischemia induces adult rodent neurons to resume DNA synthesis as indicated by incorporation of bromodeoxyuridine (BrdU) and expression of G1/S-phase cell cycle transition markers. After hypoxia-ischemia, the majority of BrdU- and neuronal nuclei (NeuN)-immunoreactive cells are also terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL)-stained, suggesting that they undergo apoptosis. BrdU+ neurons, labeled shortly after hypoxia-ischemia, persist for >5 d but eventually disappear by 28 d. Before disappearing, these BrdU+/NeuN+/TUNEL+ neurons express the proliferating cell marker Ki67, lose the G1-phase cyclin-dependent kinase (CDK) inhibitors p16INK4 and p27Kip1 and show induction of the late G1/S-phase CDK2 activity and phosphorylation of the retinoblastoma protein. This contrasts to kainic acid excitotoxicity and traumatic brain injury, which produce TUNEL-positive neurons without evidence of DNA synthesis or G1/S-phase cell cycle transition. These findings suggest that hypoxia-ischemia triggers neurons to reenter the cell cycle and resume apoptosis-associated DNA synthesis in brain. Our data also suggest that the demonstration of neurogenesis after brain injury requires not only BrdU uptake and mature neuronal markers but also evidence showing absence of apoptotic markers. Manipulating the aberrant apoptosis-associated DNA synthesis that occurs with hypoxia-ischemia and perhaps neurodegenerative diseases could promote neuronal survival and neurogenesis.

Genomic abnormalities in patients with migraine and chronic migraine: preliminary blood gene expression suggests platelet abnormalities

BACKGROUND

Migraine has strong genetic and environmental components and may also be a significant contributor to chronic migraine (CM). It is hypothesized that gene expression changes in peripheral blood cells can be used to detect the interaction of these influences.

OBJECTIVE

Distinct genomic expression patterns for migraine and CM will be present. These genomic profiles will help clarify the interactions of inheritance and environment. This initial study begins to examine the feasibility of peripheral blood cell genomic analysis to assist in the understanding of the pathophysiology of migraine and CM.

METHODS

Blood samples from patients were obtained either during an acute migraine or CM. Genomic expression patterns were analyzed using Affymetrix U95A microarrays.

RESULTS

Expression patterns of 7 migraine and 15 CM patients were compared to four distinct control groups (total patients, n=56) including healthy subjects. A group of platelet genes were upregulated in both migraine and CM samples. Different gene expression patterns were also seen between migraine and CM. A group of immediate early genes including c-fos and cox-2 were expressed at higher levels in migraine, whereas specific mitochondrial genes were expressed at higher levels in CM.

CONCLUSIONS

Increased expression of platelet genes in patients with migraine and CM suggests similar underlying pathophysiology. The differences seen between migraine and CM in other genes suggest an overlapping but not identical pathophysiology. Further genomic profiling studies will help define these relationships and provide further insights into headache pathogenesis.

Hsp70 mutant proteins modulate additional apoptotic pathways and improve cell survival

Although wild-type Hsp70 (Hsp70WT) inhibits procaspase-3 processing by preventing apoptosome formation, Hsp70WT does not block active caspase-3. Because all caspase-3 inhibitors bear canonical DXXD caspase-3 recognition motifs, we determined whether mutated Hsp70s with caspase-binding motifs act as direct caspase-3 inhibitors. Based on Hsp70 molecular modeling, the DNQP, DEVQ, and EEVD regions localized on the surface of Hsp70WT were chosen, allowing us to design mutants while trying to avoid disrupting the global fold of the molecule and losing the possibility of protein-protein interactions. We replaced DNQP with DQMD, and DEVQ and EEVD with DEVD residues that should be optimal substrates for caspase-3. The resultant Hsp70 mutants directly interacted with active caspase-3 and blocked its proteolytic activity while retaining the ability to reverse protein denaturation and disrupt the interaction between Apaf-1 and procaspase-9. The Hsp70C-terminal mutants interacted with Apaf-1 and active caspase-3 significantly longer than Hsp70WT. The Hsp70 DXXD mutants protected neuron and teratocarcinoma (NT) cells against cell death much better than Hsp70WT whether given before or after serum withdrawal. Hsp70 mutants represent a possible approach to antiapoptotic biotherapeutics. Similar rational designs could be used to engineer inhibitors of additional caspase family members.

Blood gene expression profiling of neurologic diseases: a pilot microarray study

BACKGROUND

Tissue gene expression profiling with arrays measures the transcription of thousands of genes. However, this approach cannot be readily used to guide clinical neurologic practice.

OBJECTIVES

To determine whether clinical neurologic diseases are associated with unique patterns of up- and down-regulated genes in whole blood and to explore the possibility of using peripheral blood as a surrogate tissue in these diseases.

DESIGN

Case-control study.

SETTING

University-based pediatric and adult neurology clinics.

PARTICIPANTS

Patients with neurofibromatosis type 1, epilepsy, or Tourette syndrome diagnosed using traditional clinical criteria; controls without disease; and controls with neurologic disease.

MAIN OUTCOME MEASURE

Blood gene expression levels of greater than 12,000 genes, measured using U95A arrays.

RESULTS

Neurofibromatosis type 1 and childhood epilepsy treated with carbamazepine or valproic acid are associated with distinct patterns of blood gene expression. Patients with valproic acid-responsive vs valproic acid-refractory epilepsy formed distinct subclusters. Tourette syndrome was characterized by several gene expression clusters. In 1 cluster, 6 genes-all associated with immune cell function-were overexpressed.

CONCLUSION

Blood gene expression profiling can provide surrogate markers for neurologic diseases without obvious blood phenotypes.

The impact of excitotoxic blockade on the evolution of injury following combined mechanical and hypoxic insults in primary rat neuronal culture

Traumatic brain injury (TBI) involves alterations in neuronal physiology, often complicated by secondary hypoxic or hypotensive events. Excitotoxicity is an important process induced in both TBI and hypoxic or ischemic insults to the brain. We investigated two hypotheses: (1) excitotoxicity is more prominent following combined mechanical and hypoxic injury than either alone; (2) both AMPA and NMDA receptor activation mediate combined mechanical and hypoxic injury. Media in primary mixed neuronal cultures were replaced with conditioned media containing MK801 (NMDA antagonist) and/or NBQX (AMPA/kainate antagonist). Cultures were then subjected to mechanical injury. Afterward, media were exchanged for hypoxic media containing the antagonist, and plates were placed in hypoxia chambers for 7 h. At 24 h following hypoxia, LDH release, trypan blue uptake, and morphologic changes were assessed. Blockade had no effect after mechanical injury. After hypoxia, MK801 and combined MK801/NBQX decreased LDH and trypan blue to control levels. NBQX alone after hypoxia had less impact. After combined mechanical injury and hypoxia, both MK801 and NBQX partially reduced LDH and trypan blue. Combining the antagonists led to reduction to control values for both endpoints. We conclude that excitotoxic processes are more prominent after combined than isolated injuries in neurons and that increased cell death is mediated by both NMDA and AMPA receptor activation following combined injuries.

Human blood genomics: distinct profiles for gender, age and neurofibromatosis type 1

Application of gene expression profiling to human diseases will be limited by availability of tissue samples. It was postulated that germline genetic defects affect blood cells to produce unique expression patterns. This hypothesis was addressed by using a test neurological disease-neurofibromatosis type 1 (NF1), an autosomal dominant genetic disease caused by mutations of the NF1 gene at chromosome 17q11.2. Oligonucleotide arrays were used to survey the blood gene expression pattern of 12 NF1 patients compared to 96 controls. A group of genes related to tissue remodeling, bone development and tumor suppression were down-regulated in NF1 blood samples. In addition, there were blood genomic patterns for gender and age: Y chromosome genes showing higher expression in males, indicating a gene-dosage effect; and genes related to lymphocyte functions showing higher expression in children. The results suggest that genetic mutations can be manifested at the transcriptional level in peripheral blood cells and blood gene expression profiling may be useful for studying phenotypic differences of human genetic diseases and possibly providing diagnostic and prognostic markers.

Blood expression profiles for tuberous sclerosis complex 2, neurofibromatosis type 1, and Down's syndrome

Blood gene expression profiling has been applied to a variety of hematological malignancies, autoimmune disorders, and infectious diseases. This study applies this approach to genetic diseases without obvious blood phenotypes. Three genetic diseases including tuberous sclerosis complex 2, neurofibromatosis type 1, and Down's syndrome were compared with a group of healthy controls. RNA from whole blood was surveyed using Affymetrix U133A arrays. Each disease was associated with a unique gene expression pattern in blood that can be accurately distinguished by a classifier. Genes on chromosome 21 were overexpressed in Down's syndrome, and genes controlling cell cycle and proliferation were associated with tuberous sclerosis complex type 2 or neurofibromatosis type 1. A subset of genes involved in cardiac development or remodeling were overexpressed in patients with Down's syndrome and congenital heart defects. These findings suggest that blood gene expression profiling on a broader basis might be useful for genetic disease screening/diagnosis and might help elucidate mechanisms and pathways that lead to genotype-phenotype differences.

Heat shock proteins and neuromuscular disease

The heat shock proteins are families of proteins with known activities that include chaperoning nascent peptides within the cell and cytoprotection. Most work on the nervous system has related to the role of heat shock proteins in neuroprotection from either hypoxic-ischemic or traumatic injury. The role of these proteins during normal physiological activity and injury is still under investigation. Heat shock proteins in neuromuscular disease have been investigated to some extent but were largely neglected until recently. The goal of this review is to summarize the evidence linking heat shock proteins with neuromuscular disease and to provide some insight into the roles or functions of these proteins in disease states.

Hemin induces heme oxygenase-1 in spinal cord vasculature and attenuates barrier disruption and neutrophil infiltration in the injured murine spinal cord

Heme oxygenase-1 (HO-1) has been shown to alter vascular function in part by attenuating inflammation. We induced HO-1 in blood vessels in the spinal cord by systemic administration of hemin. Twenty-four hours later, immediately prior to euthanasia, fluorescence conjugated Lycopersicon esculentum (tomato) lectin was given intravenously to label the vasculature. HO-1 was induced in blood vessels, particularly in the white matter, as evidenced by the immunolocalization of HO-1 in lectin positive vessels. Western blots confirmed the hemin-mediated induction of HO-1 in the uninjured spinal cord. We next examined the extent to which treatment with hemin or vehicle, 24 h prior to a moderate contusion injury, influenced early vascular dysfunction in the injured cord. All animals were euthanized 24 h after injury. Luciferase, a marker of barrier integrity, was given intravenously 30 min prior to euthanasia. The spinal cord was either prepared for quantification of luciferase activity or fixed by vascular perfusion and prepared for the immunolocalization of neutrophils. There was a significant attenuation of barrier permeability to luciferase and a significant reduction in the number of neutrophils in hemin treated animals as compared to the vehicle treated group. Together, these findings demonstrate that vascular induction of HO-1 modulates barrier function and neutrophil infiltration and suggest that this protein may be useful for limiting the early vascular dysfunction and inflammation that occurs in the acutely injured spinal cord.

The mGlu2/3 receptor agonist LY379268 injected into cortex or thalamus decreases neuronal injury in retrosplenial cortex produced by NMDA receptor antagonist MK-801: possible implications for psychosis

The non-competitive NMDA receptor antagonists, including PCP (phencyclidine), ketamine, and MK-801 (dizocilpine) produce psychosis in humans and injure neurons in retrosplenial cortex in adult rodent brain. This study examined the effects of the metabotropic mGlu2/3 agonist LY379268 and antagonist LY341495 on cortical injury produced by systemic MK-801 (1 mg/kg i.p.) in adult female rats. Systemic injections of mGlu2/3 agonist LY379268, but not mGlu2/3 antagonist LY341495, decreased the injury in the retrosplenial cortex produced by systemic MK-801 as assessed by Hsp70 induction. Bilateral injections of LY379268, but not vehicle, into retrosplenial cortex or bilateral injections of LY379268 into anterior thalamus also decreased the injury in retrosplenial cortex produced by systemic MK-801. The data show that bilateral activation of mGlu2/3 glutamate receptors in cortex or anterior thalamus decreases the neuronal injury in retrosplenial cortex produced by systemic MK-801. Because antipsychotic medications decrease cortical injury produced by NMDA antagonists in rodents and decrease psychosis in humans, mGlu2/3 agonists that decrease cortical injury produced by NMDA antagonists in rodents might be evaluated for decreasing psychosis in people.

Molecular Identification of the Ischemic Penumbra

Review of results of experimental and clinical studies indicates that the penumbra of physiologically impaired but potentially salvageable tissue surrounding the central core of focal cerebral ischemia that develops shortly after onset of major conducting vessel occlusion is complex and dynamic with severity and duration thresholds for hypoxic stress and injury that are specific to tissue site, cell type, molecular pathway or gene expression investigated and efficiency of collateral or residual flow and reperfusion. Imaging methods that have been utilized in vivo to identify penumbra and predict response to reperfusion and other protective therapies include magnetic resonance spectroscopy, diffusion- and perfusion-MRI as well as positron emission tomography. However, resolution of focal lesions characterized by lactic acidosis or cellular edema does not predict tissue survival, and imaging thresholds for resuscitation after reperfusion have not been determined experimentally. HSP-70 stress protein induction represents an endogenous protective mechanism that occurs in penumbra but not core neurones. A robust protective effect has been demonstrated during focal ischemia in transgenic mice overexpressing HSP-70 perhaps by suppressing early cytochrome c release. Delayed manganese mediated striatal neurodegeneration can be detected with T1 MRI after brief episodes of transient focal ischemia. Future studies may define endogenous cytotoxic and cytoprotective molecular penumbras that can be exploited to improve outcome after temporary focal ischemia.

Glutamate receptor blockade attenuates glucose hypermetabolism in perihematomal brain after experimental intracerebral hemorrhage in rat

BACKGROUND AND PURPOSE

Intracerebral hemorrhage has no effective treatment. The delayed appearance of edema, apoptosis, and inflammation in perihematomal brain suggests that these events may be targets for therapeutic intervention. To develop successful treatments, we must learn more about the effects of hemorrhage on brain tissue. In this study, we investigated the acute metabolic effects of intrastriatal hemorrhage in rat brain.

METHODS

Lysed blood or saline (50 microL each) was injected into the striatum of male Sprague-Dawley rats. The rats recovered for 1 to 72 hours before injection of [14C]-2-deoxyglucose (intraperitoneally) 30 minutes before decapitation. Animals were pretreated with the N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor antagonists dizolcilpine maleate (MK-801; 1 mg/kg) or 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[f]quinoxaline (NBQX; 30 mg/kg), or saline vehicle. Additional animals received intrastriatal injections of glutamate (1.0 mmol/L), NMDA (1.0 mmol/L), or AMPA (0.1 mmol/L) in the place of blood. Semiquantitative autoradiographs from the brains were analyzed to determine the effects of hemorrhage on relative glucose metabolism.

RESULTS

We found an acute phase of increased [14C]-2-deoxyglucose uptake in the perihematomal region that peaks 3 hours after lysed blood injection. Saline injections had no effect on striatal glucose utilization. The increased [14C]-2-deoxyglucose uptake produced by the hemorrhages was blocked by pretreatment with MK-801 and NBQX. Glutamate injections alone had no effect on striatal metabolism, whereas NMDA and AMPA injections increased [14C]-2-deoxyglucose uptake.

CONCLUSIONS

The data imply that glutamate activation of NMDA or AMPA receptors increases glucose metabolism in perihematomal brain at early times after intracerebral hemorrhage. This may provide a possible target for the treatment of intracerebral hemorrhage.

Expression of proinflammatory cytokines tumor necrosis factor-α and interleukin-1β in the brain during experimental Group B streptococcal meningitis

We performed mRNA in situ hybridization for TNF-alpha and IL-1beta from infant rats with group B streptococcal meningitis. Induction of both cytokines was seen in the ependyma and the meninges at 4 h. Both cytokines were expressed in the brain parenchyma at 12 h. Induction of IL-1beta mRNA was seen in vessels within the brain cortex. Neutrophilic infiltrate at all time points examined was minimal and could not account for the observed cytokine expression.

Hsp70 promotes TNF-mediated apoptosis by binding IKK gamma and impairing NF-kappa B survival signaling

The major heat shock protein, Hsp70, can protect against cell death by directly interfering with mitochondrial apoptosis pathways. However, Hsp70 also sensitizes cells to certain apoptotic stimuli like TNF. Little is known about how Hsp70 enhances apoptosis. We demonstrate here that Hsp70 promotes TNF killing by specifically binding the coiled-coil domain of I kappa B kinase gamma (IKK gamma) to inhibit IKK activity and consequently inhibit NF-kappa B-dependent antiapoptotic gene induction. An IKK gamma mutant, which interacts with Hsp70, competitively inhibits the Hsp70-IKK gamma interaction and relieves heat-mediated NF-kappa B suppression. Depletion of Hsp70 expression with RNA interference rescues TNF-mediated cell death. Although TNF may or may not be sufficient to trigger apoptosis on its own, TNF-triggered apoptosis was initiated or made worse when Hsp70 expression increased to high levels to disrupt NF-kappa B signaling. These results provide significant novel insights into the molecular mechanism for the pro-apoptotic behavior of Hsp70 in death-receptor-mediated cell death.

Cloning and expression of short interspersed elements B1 and B2 in ischemic brain

Global ischemia causes an extensive cell death 3 days after the ischemia in the CA1 region of the hippocampus, which is preceded by induction of a spectrum of genes with both neuroprotective and detrimental properties. This delayed cell death has been suggested to be mainly caused by programmed cell death. Here we applied differential display to characterize transcripts induced by global ischemia after 1 day in Mongolian gerbils, when the cells in the CA1 region are still viable, but initiating the cell death pathway. One of the cloned transcripts turned out to be a repeat sequence termed SINE B2. We also cloned the other member of the SINE family, SINE B1, and found it also to be slightly induced by ischemia in the CA1 region. The SINE repeat regions are not translated and their role in ischemia may be related the neurons' attempt to cope with decreased translational levels and/or genomic reorganization. Together with the previous data demonstrating the inducibility of the SINE transcripts using in vitro stress models, the present study shows that SINE transcripts are stress-inducible factors in the central nervous system.

Valproic acid blood genomic expression patterns in children with epilepsy - a pilot study

OBJECTIVE

Valproic acid (VPA) is a commonly used anticonvulsant with multiple systemic effects. The purpose of this pilot study is to examine the blood genomic expression pattern associated with VPA therapy in general and secondly VPA efficacy in children with epilepsy.

MATERIALS AND METHODS

Using oligonucleotide microarrays, gene expression in whole blood was assessed in pediatric epilepsy patients following treatment with VPA compared with children with epilepsy prior to initiation of anticonvulsant therapy (drug free patients).

RESULTS

The expression of 461 genes was altered in VPA patients (n = 11) compared with drug free patients (n = 7), among which a significant number of serine threonine kinases were down-regulated. Expression patterns in children seizure free on VPA therapy (n = 8) demonstrated 434 up-regulated genes, many in mitochondria, compared with VPA children with continuing seizures (n = 3) and drug free seizure patients (n = 7).

CONCLUSION

VPA therapy is associated with two significant and unique blood gene expression patterns: chronic VPA monotherapy in general and a separate blood genomic profile correlated with seizure freedom. These expression patterns provide new insight into previously undetected mechanisms of VPA anticonvulsant activity.

Differential cerebral protein synthesis and heat shock protein 70 expression in the core and penumbra of rat brain after transient focal ischemia

OBJECTIVE

The purpose of this study was to correlate the cerebral protein synthesis (CPS) reductions in the ischemic core and penumbra with the metabolic stress response indicated by heat shock protein 70 (HSP70) synthesis.

METHODS

Rats were subjected to 90 minutes of temporary focal cerebral ischemia produced by occlusion of the middle cerebral artery, using the endovascular suture model. Regional CPS was qualitatively evaluated, with [(35)S]methionine autoradiography, after reperfusion for 2 to 72 hours. The observed changes were correlated with HSP70 immunoreactivity, as assessed in the same brain sections. The ischemic core in the striatum was characterized by HSP70 expression only in endothelial and/or glial cells, with an absence of expression in neurons. The penumbra was delineated as the cortical middle cerebral artery territory region in which HSP70 was also expressed in metabolically stressed neurons.

RESULTS

After 2 hours of reperfusion, CPS was reduced to 30 +/- 16% of the homologous contralateral hemisphere value in the core and to 75 +/- 22% in the penumbra (P < 0.05). This difference was still present at 72 hours, when CPS values were 62 +/- 21% and 98 +/- 29% of the nonischemic contralateral hemisphere values in the core and penumbra, respectively (P < 0.05).

CONCLUSION

Persistent inhibition of CPS in regions in which neuronal HSP70 expression is absent may distinguish core areas of infarction from penumbral regions in which neuronal HSP70 is present, which eventually recover from sublethal metabolic stress during reperfusion after temporary focal ischemia.

Genomics of the periinfarction cortex after focal cerebral ischemia

Understanding transcriptional changes in brain after ischemia may provide therapeutic targets for treating stroke and promoting recovery. To study these changes on a genomic scale, oligonucleotide arrays were used to assess RNA samples from periinfarction cortex of adult Sprague-Dawley rats 24 h after permanent middle cerebral artery occlusions. Of the 328 regulated transcripts in ischemia compared with sham-operated animals, 264 were upregulated, 64 were downregulated, and 163 (49.7%) had not been reported in stroke. Of the functional groups modulated by ischemia: G-protein-related genes were the least reported; and cytokines, chemokines, stress proteins, and cell adhesion and immune molecules were the most highly expressed. Quantitative reverse transcription polymerase chain reaction of 20 selected genes at 2, 4, and 24 h after ischemia showed early upregulated genes (2 h) including Narp, Rad, G33A, HYCP2, Pim-3, Cpg21, JAK2, CELF, Tenascin, and DAF. Late upregulated genes (24 h) included Cathepsin C, Cip-26, Cystatin B, PHAS-I, TBFII, Spr, PRG1, and LPS-binding protein. Glycerol 3-phosphate dehydrogenase, which is involved in mitochondrial reoxidation of glycolysis derived NADH, was regulated more than 60-fold. Plasticity-related transcripts were regulated, including Narp, agrin, and Cpg21. A newly reported lung pathway was also regulated in ischemic brain: C/EBP induction of Egr-1 (NGFI-A) with downstream induction of PAI-1, VEGF, ICAM, IL1, and MIP1. Genes regulated acutely after stroke may modulate cell survival and death; also, late regulated genes may be related to tissue repair and functional recovery.

Heme and iron metabolism: role in cerebral hemorrhage

Heme and iron metabolism are of considerable interest and importance in normal brain function as well as in neurodegeneration and neuropathologically following traumatic injury and hemorrhagic stroke. After a cerebral hemorrhage, large numbers of hemoglobin-containing red blood cells are released into the brain's parenchyma and/or subarachnoid space. After hemolysis and the subsequent release of heme from hemoglobin, several pathways are employed to transport and metabolize this heme and its iron moiety to protect the brain from potential oxidative stress. Required for these processes are various extracellular and intracellular transporters and storage proteins, the heme oxygenase isozymes and metabolic proteins with differing localizations in the various brain-cell types. In the past several years, additional new genes and proteins have been discovered that are involved in the transport and metabolism of heme and iron in brain and other tissues. These discoveries may provide new insights into neurodegenerative diseases like Alzheimer's, Parkinson's, and Friedrich's ataxia that are associated with accumulation of iron in specific brain regions or in specific organelles. The present review will examine the uptake and metabolism of heme and iron in the brain and will relate these processes to blood removal and to the potential mechanisms underlying brain injury following cerebral hemorrhage.

Heme oxygenase-2 protects against lipid peroxidation-mediated cell loss and impaired motor recovery after traumatic brain injury

After traumatic brain injury (TBI), substantial extracellular heme is released from hemoproteins during hemorrhage and cell injury. Heme oxygenase (HO) isozymes are thought to detoxify the pro-oxidant heme to the potent antioxidant, bilirubin. HO-1, the inducible isozyme, is expressed in glial populations after injury and may play a protective role. However, the role of HO-2, the predominant and constitutively expressed isozyme in the brain, remains unclear after TBI. We used a controlled cortical impact injury model to determine the extent and mechanism of damage between HO-2 knock-out (KO) (-/-) and wild-type (WT) (+/+) mice. The specific cellular and temporal expressions of HO-2 and HO-1 were characterized by immunocytochemistry and Western blots. HO-2 was immunolocalized in neurons both before and after TBI, whereas HO-1 was highly upregulated in glia only after TBI. HO activity determined by gas chromatography using brain sonicates from injured HO-2 KO mice was significantly less than that of HO-2 wild types, despite the induction of HO-1 expression after TBI. Cell loss was significantly greater in KO mice in areas including the cortex, the CA3 region of hippocampus, and the lateral dorsal thalamus. Furthermore, motor recovery after injury, as measured by the rotarod assay and an inclined beam-walking task, was compromised in the KO mice. Finally, brain tissue from injured HO-2 KO mice exhibited decreased ability to reduce oxidative stress, as measured with an Fe(2+)/ascorbic acid-mediated carbon monoxide generation assay for lipid peroxidation susceptibility. These findings demonstrate that HO-2 expression protects neurons against TBI by reducing lipid peroxidation via the catabolism of free heme.

Blood genomic expression profile for neuronal injury

This study determined whether stroke and other types of insults produced a gene expression profile in blood that correlated with the presence of neuronal injury. Adult rats were subjected to ischemic stroke, intracerebral hemorrhage, status epilepticus, and insulin-induced hypoglycemia and compared with untouched, sham surgery, and hypoxia animals that had no brain injury. One day later, microarray analyses showed that 117 genes were upregulated and 80 genes were downregulated in mononuclear blood cells of the "injury" (n = 12) compared with the "no injury" (n = 9) animals. A second experiment examined the whole blood genomic response of adult rats after global ischemia and kainate seizures. Animals with no brain injury were compared with those with brain injury documented by TUNEL and PANT staining. One day later, microarray analyses showed that 37 genes were upregulated and 67 genes were downregulated in whole blood of the injury (n = 4) animals compared with the no-injury (n = 4) animals. Quantitative reverse transcription-polymerase chain reaction confirmed that the vesicular monoamine transporter-2 increased 2.3- and 1.6-fold in animals with severe and mild brain injury, respectively, compared with no-injury animals. Vascular tyrosine phosphatase-1 increased 2.0-fold after severe injury compared with no injury. The data support the hypothesis that there is a peripheral blood genomic response to neuronal injury, and that this blood response is associated with a specific blood mRNA gene expression profile that can be used as a marker of the neuronal damage.

Cyclooxygenase-2 mRNA expression is associated with c-fos mRNA expression and transient water ADC reduction detected with diffusion MRI during acute focal ischemia in rats

Cyclooxygenase-2 (COX-2) plays an important role in the development of injury during cerebral ischemia and inhibition of its activity can reduce infarct size. COX-2 expression during acute ischemia is caused by activation of post-synaptic glutamate receptors, which occurs during spreading depression and ischemic depolarization. Both of these phenomena cause a reduction in the apparent diffusion coefficient of water (ADC), which can be detected with diffusion-weighted magnetic resonance imaging. The reduction is believed to be caused by cellular swelling that occurs as cells depolarize. The goal of this work was to determine the spatial relationship between cyclooxygenase-2 mRNA (cox-2) expression, c-fos mRNA expression and ADC reduction during acute focal cerebral ischemia. Adult rats were subjected to either 30- or 60-min permanent occlusion of the middle cerebral artery. A 2-Tesla scanner was used to acquire diffusion-weighted echo-planar images throughout the ischemic period, which were used to calculate ADC maps. Cox-2 and c-fos mRNA were detected with (35)S in situ hybridization. The results indicate that, for rats subjected to 60-min ischemia, cox-2 was observed in superficial layers of cortex, where transient ADC reduction and c-fos expression were observed. The same was true for most rats subjected to 30-min ischemia. However, in a small number of rats of the 30-min group, cox-2 mRNA expression was observed in regions exhibiting transient and persistent ADC reduction with no c-fos expression. The results suggest that cox-2 mRNA expression during acute MCA occlusion is caused by either or both spreading depression and transient ischemic depolarization.