Overexpression of the glucose transporter gene with a herpes simplex viral vector protects striatal neurons against stroke

Hippocampal region-specific endogenous neuroprotection as an approach in the search for new neuroprotective strategies in ischemic stroke. Fiction or fact?

Ischemic stroke is the leading cause of death and long-term disability worldwide, and, while considerable progress has been made in understanding its pathophysiology, the lack of effective treatments remains a major concern. In that context, receiving more and more consideration as a promising therapeutic method is the activation of natural adaptive mechanisms (endogenous neuroprotection) - an approach that seeks to enhance and/or stimulate the endogenous processes of plasticity and protection of the neuronal system that trigger the brain's intrinsic capacity for self-defence. Ischemic preconditioning is a classic example of endogenous neuroprotection, being the process by which one or more brief, non-damaging episodes of ischemia-reperfusion (I/R) induce tissue resistance to subsequent prolonged, damaging ischemia. Another less-known example is resistance to an I/R episode mounted by the hippocampal region consisting of CA2, CA3, CA4 and the dentate gyrus (here abbreviated to CA2-4, DG). This can be contrasted with the ischemia-vulnerable CA1 region. There is not yet a good understanding of these different sensitivities of the hippocampal regions, and hence of the endogenous neuroprotection characteristic of CA2-4, DG. However, this region is widely reported to have properties distinct from CA1, and capable of generating resistance to an I/R episode. These include activation of neurotrophic and neuroprotective factors, greater activation of anti-excitotoxic and anti-oxidant mechanisms, increased plasticity potential, a greater energy reserve and improved mitochondrial function. This review seeks to summarize properties of CA2-4, DG in the context of endogenous neuroprotection, and then to assess the potential utility of these properties to therapeutic approaches. In so doing, it appears to represent the first such addressing of the issue of ischemia resistance attributable to CA2-4, DG.

Notoginsenoside R1 ameliorates mitochondrial dysfunction to circumvent neuronal energy failure in acute phase of focal cerebral ischemia

Due to sudden loss of cerebral blood circulation, acute ischemic stroke (IS) causes neuronal energy attenuation or even exhaustion by mitochondrial dysfunction resulting in aggravation of neurological injury. In this study, we investigated if Notoginsenoside R1 ameliorated cerebral energy metabolism by limiting neuronal mitochondrial dysfunction in acute IS. Male Sprague-Dawley rats (260-280 g) were selected and performed by permanent middle cerebral artery occlusion model. In vitro, the oxygen glucose deprivation (OGD) model of Neuro2a (N2a) cells was established. We found Notoginsenoside R1 treatment reduced rats' cerebral infarct volume and neurological deficits, with increased Adenosine triphosphate (ATP) level together with upregulated expression of glucose transporter 1/3, monocarboxylate transporter 1 and citrate synthase in brain peri-ischemic tissue. In vitro, OGD-induced N2a cell death was inhibited, cell mitochondrial morphology was improved. Mitochondrial amount, mitochondrial membrane potential, and mitochondrial DNA copy number were increased by Notoginsenoside R1 administration. Furthermore, mitochondrial energy metabolism-related mRNA array found Atp12a and Atp6v1g3 gene expression were upregulated more than twofold, which were also verified in rat ischemic tissue by quantitative polymerase chain reaction (qPCR) assay. Therefore, Notoginsenoside R1 administration increases cerebral glucose and lactate transportation and ATP levels, ameliorates neuronal mitochondrial function after IS. Notoginsenoside R1 may be a novel protective agent for neuronal mitochondria poststroke.

[Potential of the Cerebral Sodium-Glucose Transporter as a Novel Therapeutic Target in Cerebral Ischemia]

　Cerebral ischemic stress often induces a hyperglycemic condition. This postischemic hyperglycemia exacerbates the development of cerebral ischemic neuronal damage, although the mechanism of this exacerbation remains to be clarified. We previously discovered that the cerebral sodium-glucose transporter (SGLT) was closely involved in the development of cerebral ischemic neuronal damage. SGLT is a member of the glucose transporter family and moves glucose together with sodium ions. SGLT-1, -3, -4, and -6 are distributed in the brain. We conducted further experiments to elucidate the detailed mechanism of the exacerbation of cerebral ischemia by cerebral SGLT. The results clarified: 1) the relationship between cerebral SGLT and postischemic hyperglycemia; 2) the involvement of cerebral SGLT-1 (a cerebral SGLT isoform) in cerebral ischemic neuronal damage; and 3) the effects of sodium influx through cerebral SGLT on the development of cerebral ischemic neuronal damage. This paper presents our data on the involvement of cerebral SGLT in the exacerbation of cerebral ischemic neuronal damage.

Hypoxia Inducible Factor 1α Promotes Endogenous Adaptive Response in Rat Model of Chronic Cerebral Hypoperfusion

Hypoxia inducible factor 1α (HIF-1α), a pivotal regulator of gene expression in response to hypoxia and ischemia, is now considered to regulate both pro-survival and pro-death responses depending on the duration and severity of the stress. We previously showed that chronic global cerebral hypoperfusion (CCH) triggered long-lasting accumulation of HIF-1α protein in the hippocampus of rats. However, the role of the stabilized HIF-1α in CCH is obscure. Here, we knock down endogenous HIF-1α to determine whether and how HIF-1α affects the disease processes and phenotypes of CCH. Lentivirus expressing HIF-1α small hairpin RNA was injected into the bilateral hippocampus and bilateral ventricles to knock down HIF-1α gene expression in the hippocampus and other brain areas. Permanent bilateral common carotid artery occlusions, known as 2-vessel occlusions (2VOs), were used to induce CCH in rats. Angiogenesis, oxidative stress, histopathological changes of the brain, and cognitive function were tested. Knockdown of HIF-1α prior to 2VO significantly exacerbates the impairment of learning and memory after four weeks of CCH. Mechanically, reduced cerebral angiogenesis, increased oxidative damage, and increased density of astrocytes and microglia in the cortex and some subregions of hippocampus are also shown after four weeks of CCH. Furthermore, HIF-1α knockdown also disrupts upregulation of regulated downstream genes. Our findings suggest that HIF-1α-protects the brain from oxidative stress and inflammation response in the disease process of CCH. Accumulated HIF-1α during CCH mediates endogenous adaptive processes to defend against more severe hypoperfusion injury of the brain, which may provide a therapeutic benefit.

Lesion Size Is Exacerbated in Hypoxic Rats Whereas Hypoxia-Inducible Factor-1 Alpha and Vascular Endothelial Growth Factor Increase in Injured Normoxic Rats: A Prospective Cohort Study of Secondary Hypoxia in Focal Traumatic Brain Injury

BACKGROUND

Hypoxia following traumatic brain injury (TBI) is a severe insult shown to exacerbate the pathophysiology, resulting in worse outcome. The aim of this study was to investigate the effects of a hypoxic insult in a focal TBI model by monitoring brain edema, lesion volume, serum biomarker levels, immune cell infiltration, as well as the expression of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF).

MATERIALS AND METHODS

Female Sprague-Dawley rats (n = 73, including sham and naive) were used. The rats were intubated and mechanically ventilated. A controlled cortical impact device created a 3-mm deep lesion in the right parietal hemisphere. Post-injury, rats inhaled either normoxic (22% O2) or hypoxic (11% O2) mixtures for 30 min. The rats were sacrificed at 1, 3, 7, 14, and 28 days post-injury. Serum was collected for S100B measurements using ELISA. Ex vivo magnetic resonance imaging (MRI) was performed to determine lesion size and edema volume. Immunofluorescence was employed to analyze neuronal death, changes in cerebral macrophage- and neutrophil infiltration, microglia proliferation, apoptosis, complement activation (C5b9), IgG extravasation, HIF-1α, and VEGF.

RESULTS

The hypoxic group had significantly increased blood levels of lactate and decreased pO2 (p < 0.0001). On MRI post-traumatic hypoxia resulted in larger lesion areas (p = 0.0173), and NeuN staining revealed greater neuronal loss (p = 0.0253). HIF-1α and VEGF expression was significantly increased in normoxic but not in hypoxic animals (p < 0.05). A trend was seen for serum levels of S100B to be higher in the hypoxic group at 1 day after trauma (p = 0.0868). No differences were observed between the groups in cytotoxic and vascular edema, IgG extravasation, neutrophils and macrophage aggregation, microglia proliferation, or C5b-9 expression.

CONCLUSION

Hypoxia following focal TBI exacerbated the lesion size and neuronal loss. Moreover, there was a tendency to higher levels of S100B in the hypoxic group early after injury, indicating a potential validity as a biomarker of injury severity. In the normoxic group, the expression of HIF-1α and VEGF was found elevated, possibly indicative of neuro-protective responses occurring in this less severely injured group. Further studies are warranted to better define the pathophysiology of post-TBI hypoxia.

Elevated glucose level adversely affects infarct volume growth and neurological deterioration in non-diabetic stroke patients, but not diabetic stroke patients

BACKGROUND AND PURPOSE

Hyperglycemia is recognized as a common occurrence associated with a high risk of poor outcome in ischaemic stroke patients. However, little is known about the association between elevated glucose level, growth of infarct volume and neurological deterioration in ischaemic stroke patients without diabetes. The present study aimed to clarify this issue in acute ischaemic stroke patients with arterial occlusion.

METHODS

We studied 375 acute ischaemic stroke patients with arterial occlusion within 24 h of onset. Diabetes was diagnosed in patients with a known history of diabetes or HbA1c value ≥ 6.5%. Infarct volume was measured on admission and at follow-up within 48 h using diffusion-weighted imaging. Neurological deterioration was defined as an increase of ≥ 4 points in National Institutes of Health Stroke Scale score within 7 days of stroke onset. We examined the relationship between glucose level on admission, infarct volume growth and neurological deterioration in three categories (all patients, non-diabetes and diabetes) using multivariate modeling.

RESULTS

Diabetes was present in 104 patients (27.7%). Multivariate regression analysis showed that elevated glucose level was independently associated with infarct volume growth in all patients (P = 0.034) and non-diabetes (P = 0.002), but not in diabetes (P = 0.871). Moreover, elevated glucose level was independently associated with neurological deterioration in all patients [odds ratio (OR), 1.010; 95% confidence interval (CI), 1.004-1.017; P = 0.002] and non-diabetes (OR, 1.014; 95% CI, 1.002-1.026; P = 0.022), but not diabetes (OR, 1.006; 95% CI, 0.998-1.014; P = 0.151).

CONCLUSIONS

Glucose level appears to influence infarct volume growth and neurological deterioration, particularly in non-diabetic patients with ischaemic stroke.

The potential roles of 18F-FDG-PET in management of acute stroke patients

Extensive efforts have recently been devoted to developing noninvasive imaging tools capable of delineating brain tissue viability (penumbra) during acute ischemic stroke. These efforts could have profound clinical implications for identifying patients who may benefit from tPA beyond the currently approved therapeutic time window and/or patients undergoing neuroendovascular treatments. To date, the DWI/PWI MRI and perfusion CT have received the most attention for identifying ischemic penumbra. However, their routine use in clinical settings remains limited. Preclinical and clinical PET studies with [¹⁸F]-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) have consistently revealed a decreased ¹⁸F-FDG uptake in regions of presumed ischemic core. More importantly, an elevated ¹⁸F-FDG uptake in the peri-ischemic regions has been reported, potentially reflecting viable tissues. To this end, this paper provides a comprehensive review of the literature on the utilization of ¹⁴C-2-DG and ¹⁸F-FDG-PET in experimental as well as human stroke studies. Possible cellular mechanisms and physiological underpinnings attributed to the reported temporal and spatial uptake patterns of ¹⁸F-FDG are addressed. Given the wide availability of ¹⁸F-FDG in routine clinical settings, ¹⁸F-FDG PET may serve as an alternative, non-invasive tool to MRI and CT for the management of acute stroke patients.

Progesterone treatment before experimental hypoxia-ischemia enhances the expression of glucose transporter proteins GLUT1 and GLUT3 in neonatal rats

Progesterone is an efficient candidate for treating stroke and traumatic brain damage. The current study was designed to investigate the effects of progesterone on glucose transporter proteins (GLUT1 and GLUT3) during hypoxic-ischemic injury in a neonatal rat model. We demonstrated strong staining for GLUT1 in the walls of blood vessels and GLUT3 immunoreactivity in hippocampal neurons after hypoxiaischemia. Hypoxia-ischemia elevated GLUT1 and GLUT3 at both the mRNA and protein levels in the hippocampus, and pre-treatment with progesterone (8 mg/kg) further enhanced their accumulation until 24 h after hypoxic-ischemic injury. These results showed that progesterone treatment induced the accumulation of both GLUT1 and GLUT3 transporters, and an energy-compensation mechanism may be involved in the neuroprotective effect of progesterone during hypoxic-ischemic injury after cerebral ischemic attacks.

Differential effects of HIF-1 inhibition by YC-1 on the overall outcome and blood-brain barrier damage in a rat model of ischemic stroke

Hypoxia-inducible factor 1 (HIF-1) is a master regulator of cellular adaptation to hypoxia and has been suggested as a potent therapeutic target in cerebral ischemia. Here we show in an ischemic stroke model of rats that inhibiting HIF-1 and its downstream genes by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) significantly increases mortality and enlarges infarct volume evaluated by MRI and histological staining. Interestingly, the HIF-1 inhibition remarkably ameliorates ischemia-induced blood-brain barrier (BBB) disruption determined by Evans blue leakage although it does not affect brain edema. The result demonstrates that HIF-1 inhibition has differential effects on ischemic outcomes and BBB permeability. It indicates that HIF-1 may have different functions in different brain cells. Further analyses show that ischemia upregulates HIF-1 and its downstream genes erythropoietin (EPO), vascular endothelial growth factor (VEGF), and glucose transporter (Glut) in neurons and brain endothelial cells and that YC-1 inhibits their expression. We postulate that HIF-1-induced VEGF increases BBB permeability while certain other proteins coded by HIF-1's downstream genes such as epo and glut provide neuroprotection in an ischemic brain. The results indicate that YC-1 lacks the potential as a cerebral ischemic treatment although it confers certain protection to the cerebral vascular system.

Specific inhibition of hypoxia inducible factor 1 exaggerates cell injury induced by in vitro ischemia through deteriorating cellular redox environment

Hypoxia inducible factor 1 (HIF-1) has been suggested to play a critical role in the fate of cells exposed to hypoxic stress. However, the mechanism of HIF-1-regulated cell survival is still not fully understood in ischemic conditions. Redox status is critical for decisions of cell survival, death and differentiation. We investigated the effects of inhibiting HIF-1 on cellular redox status in SH-SY5Y cells exposed to hypoxia or oxygen and glucose deprivation (OGD), coupled with cell death analyses. Our results demonstrated that inhibiting HIF-1alpha expression by HIF-1alpha specific small interfering RNA (siRNA) transfection increased reactive oxygen species generation, and transformed the cells to more oxidizing environments (low GSH/GSSG ratio, low NADPH level) under either hypoxic or OGD exposure. Cell death increased dramatically in the siRNA transfected cells, compared to non-transfected cells after hypoxic/OGD exposures. In contrast, increasing HIF-1alpha expression by desferrioxamine, a metal chelator and hydroxylase inhibitor, induced a more reducing environment (high GSH/GSSG ratio, high NADPH level) and reduced cell death. Further studies showed that HIF-1 regulated not only glucose transporter-1 expression, but also the key enzymes of the pentose phosphate pathway such as glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. These enzymes are important in maintaining cellular redox homeostasis by generating NADPH, the primary reducing agent in cells. Moreover, catalase significantly decreased cell death in the siRNA-transfected cells induced by hypoxia and OGD. These results suggest that maintenance of cellular redox status by HIF-1 protects cells from hypoxia and ischemia mediated injuries.

Blocking glucocorticoid and enhancing estrogenic genomic signaling protects against cerebral ischemia

Glucocorticoids (GCs) and estrogen can modulate neuron death and dysfunction during neurological insults. Glucocorticoids are adrenal steroids secreted during stress, and hypersecretion of GCs during cerebral ischemia compromises the ability of hippocampal and cortical neurons to survive. In contrast, estrogen can be neuroprotective after cerebral ischemia. Here we evaluate the protective potential of a herpes viral vector expressing a chimeric receptor (ER/GR), which is composed of the ligand-binding domain of the GC receptor (GR) and the DNA-binding domain of the estrogen receptor-alpha (ER). This novel receptor can transduce an endangering GC signal into a protective estrogenic one. Using an in vitro oxygen glucose deprivation model (OGD), GCs exacerbated neuron death in primary cortical cultures, and this worsening effect was completely blocked by ER/GR expression. Moreover, blocking GC actions with a vector expressing a dominant negative GC receptor promoted neuron survival during postischemia, but not preischemia. Thus, gene therapeutic strategies to modulate GC and estrogen signaling can be beneficial during an ischemic insult.

Hypoxia inducible factor 1 as a therapeutic target in ischemic stroke

In stroke research, a significant focus is to develop therapeutic strategies that prevent neuronal death and improve recovery. Yet, few successful therapeutic strategies have emerged. Hypoxia-inducible factor 1 (HIF-1) is a key regulator in hypoxia. It has been suggested to be an important player in neurological outcomes following ischemic stroke due to the functions of its downstream genes. These include genes that promote glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Many lines of evidence have shown that HIF-1 is induced in ischemic brains. Importantly, it seems that HIF-1 is primarily induced in the salvageable tissue of an ischemic brain, penumbra. However, the effect of HIF-1 on neuronal tissue injuries is still debatable based on evidence from in vitro and preclinical studies. Furthermore, it is of importance to understand the mechanism of HIF-1 degradation after its induction in ischemic brain. This review provides a present understanding of the mechanism of HIF-1 induction in ischemic neurons and the potential effect of HIF-1 on ischemic brain tissue. The author also elaborates on potential therapeutic approaches through understanding of the induction mechanism and of the potential role of HIF-1 in ischemic stroke.

Acetylcholine esterase activity and behavioral response in hypoxia induced neonatal rats: effect of glucose, oxygen and epinephrine supplementation

Brain damage due to an episode of hypoxia remains a major problem in infants causing deficit in motor and sensory function. Hypoxia leads to neuronal functional failure, cerebral palsy and neuro-developmental delay with characteristic biochemical and molecular alterations resulting in permanent or transitory neurological sequelae or even death. During neonatal hypoxia, traditional resuscitation practices include the routine administration of 100% oxygen, epinephrine and glucose. In the present study, we assessed the changes in the cholinergic system by measuring the acetylcholinesterase (AChE) activity and the behavioral responses shown by hypoxia induced neonatal rats and hypoxic rats supplemented with glucose, oxygen and epinephrine using elevated plus-maze and open-field test. The acetylcholine esterase enzyme activity showed a significant decrease in cerebral cortex, whereas it increased significantly in the muscle of experimental rats when compared to control. Hypoxic rats supplemented with glucose, glucose and oxygen showed a reversal to the control status. Behavioral studies were carried out in experimental rats with elevated plus-maze test and open-field test. Hypolocomotion and anxiogenic behavioral responses were observed in all experimental rats when compared to control, hypoxic rats supplemented with glucose, glucose and oxygen. Thus, our results suggest that brain damage due to hypoxia, oxygen and epinephrine supplementation in the neonatal rats cause acetylcholine-neuromuscular-defect leading to hypolocomotion and anxiogenic behavioral response. Glucose and glucose with oxygen supplementation to hypoxic neonates protect the brain damage for a better functional status in the later life.

Neuroprotective role of Bacopa monnieri extract in epilepsy and effect of glucose supplementation during hypoxia: glutamate receptor gene expression

The experiments were designed to study the glutamate gene expression during epilepsy in adult and hypoxic insult to brain during the neonatal period and the therapeutic role of neuroprotective supplements. We investigated the role of metabotropic glutamate-8 receptor (mGluR8) gene expression in cerebellum during epilepsy and neuroprotective role of Bacopa monnieri extract in epilepsy. We also studied the effect of NMDA receptor 1 (NMDAR1) gene expression during neonatal hypoxia and therapeutic role of glucose, oxygen and epinephrine supplementation. During epilepsy a significant down-regulation (P < 0.01) of mGluR8 gene expression was observed which was up-regulated (P < 0.05) near control level after B. monnieri treatment which is supported by Morris water maze experiment. In hypoxic neonates we observed up-regulation (P < 0.001) of the NMDAR1 gene expression whereas glucose and glucose + oxygen was able to significantly reverse (P < 0.001) the gene expression to near control level when compared to hypoxia and epinephrine treatment which was supported by open field test. Our results showed that B. monnieri treatment to epileptic rats significantly brought the reversal of the down-regulated mgluR8 gene expression toward control level. In neonatal rats, hypoxia induced expressional and functional changes in the NMDAR1 receptors of neuronal cells which is corrected by supplementation of glucose alone or glucose followed by oxygen during the resuscitation to prevent the glutamate related neuronal damage. Thus, the results suggest the clinical significance of corrective measures for epileptic and hypoxic management.

A novel class of prolyl hydroxylase inhibitors induces angiogenesis and exerts organ protection against ischemia

OBJECTIVE

Hypoxia inducible factor (HIF) plays a pivotal role in the adaptation to ischemic conditions. Its activity is modulated by an oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHD).

METHODS AND RESULTS

We discovered 2 unique compounds (TM6008 and TM6089), which inhibited PHD and stabilized HIF activity in vitro. Our docking simulation studies based on the 3-dimensional structure of human PHD2 disclosed that they preferentially bind to the active site of PHD. Whereas PHD inhibitors previously reported inhibit PHD activity via iron chelation, TM6089 does not share an iron chelating motif and is devoid of iron chelating activity. In vitro Matrigel assays and in vivo sponge assays demonstrated enhancement of angiogenesis by local administration of TM6008 and TM6089. Their oral administration stimulated HIF activity in various organs of transgenic rats expressing a hypoxia-responsive reporter vector. No acute toxicity was observed up to 2 weeks after a single oral dose of 2000 mg/kg for TM6008. Oral administration of TM6008 protected neurons in a model of cerebrovascular disease. The protection was associated with amelioration of apoptosis but independent of enhanced angiogenesis.

CONCLUSIONS

The present study uncovered beneficial effects of novel PHD inhibitors preferentially binding to the active site of PHD.

Delayed administration of deferoxamine reduces brain damage and promotes functional recovery after transient focal cerebral ischemia in the rat

The mechanisms underlying functional recovery after stroke are poorly understood. Brain-adaptive responses to the hypoxic stress elicited by ischemia could contribute to these mechanisms. Indeed, hypoxia-inducible factor-1 (HIF-1), one of the main transcriptional factors regulated by oxygen level, increases the expression of several beneficial genes such as erythropoietin, glucose transporter-1 and vascular endothelial growth factor. In order to strengthen the expression of these hypoxia-inducible factors, we administered deferoxamine, an iron chelator known to stabilize HIF-1alpha protein expression, and examined its effects on the functional deficits induced by ischemia. Anesthetized Sprague-Dawley rats were subjected to 60 min of intraluminal occlusion of the middle cerebral artery. Chronic deferoxamine treatment (300 mg/kg, s.c.), or its vehicle, started 24 h after ischemia and was continued bi-weekly until the animals were killed. Sensorimotor deficits were periodically assessed over 2 months, and at this end point, the lesion volume was determined by histology. Treatment with deferoxamine significantly decreased the size of brain damage (-28%) after ischemia and improved behavioral recovery. Indeed, neurological score and sensorimotor performances in the adhesive removal test recovered earlier in the deferoxamine-treated animals. Moreover, the long-lasting skilled forepaw reaching deficits were attenuated by deferoxamine. Although an antioxidant effect of deferoxamine cannot be excluded, the hypothesis that its beneficial effects could be mediated by an increase in HIF-1 target genes merits further investigations. Our data suggest that delayed administration of deferoxamine could represent an interesting therapeutical approach to treat focal cerebral ischemia.

Herpes simplex virus-based vectors

Herpes simplex virus (HSV)-based vectors have primarily been developed for neuronal gene delivery, taking advantage of the virus' natural neurotropism. Two types of vector are available: replication defective viruses, whose cytotoxicity has been abolished by deleting viral gene products, and amplicon vectors, which are plasmids packaged into HSV particles with the aid of a helper virus. In this review I discuss how the cytotoxicity of the wild-type virus has been abolished, the progress which has been made toward defining promoter elements capable of directing long-term transgene expression form the latent viral genome and some of the potential clinical uses of these versatile vectors.

Postischemic Gene Transfer of Interleukin-10 Protects Against Both Focal and Global Brain Ischemia

Background— Gene therapy may be a promising approach for treatment of brain ischemia, although the efficiency of postischemic gene therapy is not established. Our goal in this study was to examine the effects of gene transfer of interleukin-10 (IL-10), an antiinflammatory cytokine, after induction of brain ischemia.

Methods and Results— Brain ischemia was produced by either photochemical occlusion of distal middle cerebral artery for focal ischemia or bilateral carotid occlusion for global ischemia in spontaneously hypertensive rats. Adenoviral vectors encoding human IL-10 (AdIL10) or β-galactosidase (control) were injected into the lateral ventricle 90 or 60 minutes after focal or global ischemia. Five days after ischemia, IL-10, IL-1β, or tissue necrosis factor-α in the cerebrospinal fluid, infarct volume, infiltrations of leukocytes/macrophages in the infarct area, or hippocampal neuronal damages were determined. The transduced IL-10 was released to the cerebrospinal fluid from the ventricular wall and increased to 7623±2965 pg/mL 5 days after AdIL10 transfection. Cerebral blood flow during ischemia was not different between treatments in either focal or global ischemia. Brain infarction of the AdIL10 group was significantly smaller and infiltrations of leukocytes and macrophages were fewer in the IL-10 treatment than control. Hippocampal neurons after global ischemia were more preserved, and the terminal deoxynucleotidyl transferase–mediated dUTP-biotin in situ nick end labeling–positive cells were diminished by the IL-10 gene transfer with attenuated IL-1β and augmented tissue necrosis factor-α.

Conclusions— Postischemic gene transfer of IL-10 into the lateral ventricle attenuated brain infarction and hippocampal damages, suggesting the promise for treatment of brain ischemia.

Anti-monocyte chemoattractant protein-1 gene therapy protects against focal brain ischemia in hypertensive rats

Monocyte chemoattractant protein-1 (MCP-1) is expressed in the ischemic cortex after focal brain ischemia and appears to exacerbate ischemic damage. The authors examined the effect of gene transfer of dominant negative MCP-1, called 7ND, 90 minutes after induction of focal brain ischemia in hypertensive rats. Adenoviral vectors encoding mutant MCP-1 (Ad7ND; n = 11), or Escherichia coli beta-galactosidase (AdlacZ; n = 17) as control were injected into the lateral ventricle of male spontaneously hypertensive rats. Both AdlacZ (n = 12) and Ad7ND (n = 6) administration provided transgene expression as early as 6 hours after injection and the expression further increased on day 1, followed by a sustained detection on day 5. Five days after ischemia, infarct volume (75 +/- 13 mm, n = 5, mean +/- SD) significantly reduced to 72% of control (104 +/- 22 mm3, n = 5, P < 0.05) by 7ND gene transfer. Numbers of leukocytes in the vessels (48.3 +/- 32.9/cm2) and macrophage/monocyte infiltration (475.2 +/- 125.5/mm2) of the infarct area in the Ad7ND group were significantly less than those measured in the AdlacZ group (143.8 +/- 72.1/cm2 and 671.8 +/- 125.5/mm2, P < 0.05, respectively). In summary, the postischemic gene transfer of dominant negative MCP-1 attenuated the infarct volume and infiltration of inflammatory cells, suggesting potential usefulness of the anti-MCP-1 gene therapy.

Genetic and Cellular Therapies for Cerebral Infarction

Neurosurgeons, working as surgical scientists, can have a prominent role in developing and implementing genetic and cellular therapies for cerebral ischemia. The rapid emergence of both genetic and cellular therapies for neural regeneration warrants a careful analysis before implementation of human studies to understand the pitfalls and promises of this strategy. In this article, we review the topic of genetic and cellular therapy for stroke to provide a foundation for practicing neurosurgeons and clinical scientists who may become involved in this type of work. In Part 1, we review preclinical approaches with gene transfer, such as 1) improved energy delivery, 2) reduction of intracellular calcium availability, 3) abrogation of effects of reactive oxygen species, 4) reduction of proinflammatory cytokine signaling, 5) inhibition of apoptosis mediators, and 6) restorative gene therapy, that are paving the way to develop new strategies to treat cerebral infarction. In Part 2, we discuss the results of studies that address the possibility of using cellular therapies for stroke in animal models and in human trials by reviewing 1) the basics of stem cell biology, 2) exogenous and 3) and endogenous cell sources for therapy, and 4) clinical considerations in cell therapy applications. These emerging technologies based on the advancements made in recent years in the fields of genetics, therapeutic cloning, neuroscience, stem cell biology, and gene therapy provide significant potential for new therapies for stroke.

Mild postischemic hypothermia prolongs the time window for gene therapy by inhibiting cytochrome C release

BACKGROUND AND PURPOSE

We showed previously that Bcl-2 overexpression with the use of herpes simplex viral (HSV) vectors improved striatal neuron survival when delivered 1.5 hours after stroke but not when delivered 5 hours after stroke onset. Here we determine whether hypothermia prolongs the therapeutic window for gene therapy.

METHODS

Rats were subjected to focal ischemia for 1 hour. Hypothermia (33 degrees C) was induced 2 hours after insult and maintained for 3 hours. Five hours after ischemia onset, HSV vectors expressing Bcl-2 plus beta-gal or beta-gal alone were injected into each striatum. Rats were killed 2 days later.

RESULTS

Striatal neuron survival of Bcl-2-treated, hypothermic animals was improved 2- to 3-fold over control-treated, hypothermic animals and Bcl-2-treated, normothermic animals. Neuron survival among normothermic, Bcl-2-treated animals was not different from control normothermics or control hypothermics. Double immunostaining of cytochrome c and beta-gal demonstrated that Bcl-2 plus hypothermia significantly reduced cytochrome c release.

CONCLUSIONS

Postischemic mild hypothermia extended the time window for gene therapy neuroprotection using Bcl-2 and reduced cytochrome c release.

A Genetic Approach to Ischemic Stroke Therapy

Stroke therapy will undergo a great revolution in the present decade. The knowledge of the human genome, gene interactions and proteomics will permit a new concept of drug development for stroke. Gene therapy by modification of gene expression will be useful to treat atherosclerosis and hypertensive microangiopathy, or in the acute phase, we will manipulate the acute gene expression induced by ischemia or the apoptotic gene program. However, a single abnormal gene, as in monogenic diseases, is easier to replace than several genes in complex multigenic disorders. Gene therapy, stem cell therapy and neurological grafts for stroke are still in the experimental phase, and many hurdles will have to be jumped before the introduction of these therapies into human clinical stroke trials. A more immediate clinical application of genetics to stroke therapy is the development of pharmacogenetics that analyzes the influence of genetic variability of individuals on drug response. A new era of personalized therapy is dawning where specific DNA biochips will help stroke clinicians to decide on the better use of thrombolytics, neuroprotectants, antithrombotics, statins or antihypertensives.

Brain ischemia augments exo-focal transgene expression of adenovirus-mediated gene transfer to ependyma in hypertensive rats

The ependyma is one of the feasible targets for gene transfer to the brain. Using two different replication-deficient recombinant adenoviral vectors, AdCMVbetaGal or AdRSVIL10, we examined effects of cortical brain ischemia on transgene expression in the ependyma after administration of the vector into the lateral ventricle of spontaneously hypertensive rats (SHR). Expression of the reporter gene lacZ at the lateral ventricle was detected by histochemistry for semiquantitative scoring or by biochemical assay for quantitative analysis. Ependymal cells in the ventricles expressed the transgene as early as 6 h after gene transfer in both sham treatment and ischemia treatment. In the sham treatment, the expression peaked at 12 h and slowly decreased toward day 4 and day 7. However, transgene expressions in the ischemic brain on day 4 and day 7 were significantly higher than sham treatment. In the biochemical assay, beta-galactosidase activity detected on day 4 at the periventricular area of the ischemic group (37 +/- 9 mU/mg protein) was significantly greater than that of the sham group (12 +/- 4, P < 0.01). In the enzyme-linked immunosorbent assay for gene transfer of interleukin-10 (IL-10), IL-10 in the cerebrospinal fluid (CSF) of the ischemic group (11,633 +/- 4322 pg/ml) was significantly greater than that in the sham group (2460 +/- 1486, P < 0.05) on day 5. These results suggest that transgene expression in the exo-focal remote area of ependyma is augmented by cortical ischemia, and the ependyma may be a promising target of gene transfer of brain ischemia.

HSV amplicon delivery of glial cell line-derived neurotrophic factor is neuroprotective against ischemic injury

Direct intracerebral administration of glial cell line-derived neurotrophic factor (GDNF) is neuroprotective against ischemia-induced cerebral injury. Utilizing viral vectors to deliver and express therapeutic genes presents an opportunity to produce GDNF within localized regions of an evolving infarct. We investigated whether a herpes simplex virus (HSV) amplicon-based vector encoding GDNF (HSVgdnf) would protect neurons against ischemic injury. In primary cortical cultures HSVgdnf reduced oxidant-induced injury compared to the control vector HSVlac. To test protective effects in vivo, HSVgdnf or HSVlac was injected into the cerebral cortex 4 days prior to, or 3 days, after a 60-min unilateral occlusion of the middle cerebral artery. Control stroke animals developed bradykinesia and motor asymmetry; pretreatment with HSVgdnf significantly reduced such motor deficits. Animals receiving HSVlac or HSVgdnf after the ischemic insult did not exhibit any behavioral improvement. Histological analyses performed 1 month after stroke revealed a reduction in ischemic tissue loss in rats pretreated with HSVgdnf. Similarly, these animals exhibited less immunostaining for glial fibrillary acidic protein and the apoptotic marker caspase-3. Taken together, our data indicate that HSVgdnf pretreatment provides protection against cerebral ischemia and supports the utilization of the HSV amplicon for therapeutic delivery of trophic factors to the CNS.

Gene therapy: a primer for neurosurgeons

Gene therapy involves the transfer of genes into cells with therapeutic intent. Although several methods can accomplish this, vectors based on viruses still provide the most efficient approach. For neurosurgical purposes, preclinical and clinical applications in the areas of glioma therapy, spinal neurosurgery, and neuroprotection for treatment of Parkinson's disease and cerebral ischemia are reviewed. In general, therapies applied in the neurosurgical realm have proven relatively safe, despite occasional, well-publicized cases of morbidity and death in non-neurosurgical trials. However, continued clinical and preclinical research in this area is critical, to fully elucidate potential toxicities and to generate truly effective treatments that can be applied in neurological diseases.

Gene therapy for cerebral vascular disease: update 2003

Gene therapy is a promising strategy for cerebrovascular diseases. Several genes that encode vasoactive products have been transferred via cerebrospinal fluid for the prevention of vasospasm after subarachnoid hemorrhage. Transfer of neuroprotective genes, including targeting of proinflammatory mediators, is a current strategy of gene therapy for ischemic stroke. Stimulation of growth of collateral vessels, stabilization of atherosclerotic plaques, inhibition of thrombosis, and prevention of restenosis are important objectives of gene therapy for coronary and limb arteries, but application of these approaches to carotid and intracranial arteries has received little attention. Several fundamental advances, including development of safer vectors, are needed before gene therapy achieves an important role in the treatment of cerebrovascular disease and stroke.

Brain ischemia as a potential target of gene therapy

Brain infarction is one of the most important age-associated medical conditions, and the age-related neuronal vulnerability to brain ischemia is suggested to play an important role. Recent advancements in gene transfer techniques have provided promising approaches to the treatment of brain ischemia. In experimental studies, the ischemic penumbra area can be targeted by gene transfer even after ischemic insult, and post-ischemic gene therapy seems effective in attenuation of ischemic damage in both global and focal brain ischemia. Perivascular approaches of gene transfer to the cerebral blood vessels through the subarachnoid space may lead to prevention of brain ischemia caused by vasospasm after subarachnoid hemorrhage. Gene transfer to cerebral blood vessels and ischemic brain tissue may offer future therapeutic approaches to stroke.

Reduced inflammatory reactions to the inoculation of helper-dependent adenoviral vectors in traumatically injured rat brain

Traumatic brain injury (TBI) causes delayed neuronal deficits that in principle could be prevented by timely intervention with therapeutic genes. However, appropriate vectors for gene transfer to the brain with TBI remain to be developed. First-generation adenoviruses (fgAd) are usually associated with inflammatory and toxic effects when inoculated into brains, despite their high efficiency of gene transfer to these tissues. In this study the authors attempted to determine whether a less immunogenic gene-transfer protocol can be established in the traumatically injured rat brain using helper-dependent adenoviruses (hdAd), a novel adenoviral construct with full deletion of viral coding sequences. Their results show that transgene expression from intrahippocampally inoculated hdAd is maintained for at least 2 months after TBI, in contrast to the much shorter duration of fgAd-mediated gene expression. There was only minimal secretion of proinflammatory IL-1beta and TNF-alpha after inoculation of hdAd. Furthermore, the hdAd-mediated gene expression was associated with less microglial proliferation, astrocytic activation, and macrophage infiltration than observed in fgAd-inoculated brains. There was no additional tissue loss after hdAd inoculation compared with PBS injection. Although both anti-adenoviral and neutralizing antibodies were found in serum after brain inoculation of hdAd, they did not appear to affect transgene expression. The results suggest that hdAd are less immunogenic vectors than conventional adenoviral vectors, and offer improved vehicles for long-term therapeutic transgene transfer to traumatically injured brains.

Normobaric hypoxia induces tolerance to focal permanent cerebral ischemia in association with an increased expression of hypoxia-inducible factor-1 and its target genes, erythropoietin and VEGF, in the adult mouse brain

Tolerance to cerebral ischemia is achieved by preconditioning sublethal stresses, such as ischemia or hypoxia, paradigms in which the decrease of O2 availability may constitute an early signal inducing tolerance. In accordance with this concept, this study shows that hypoxia induces tolerance against focal permanent ischemia in adult mice. Normobaric hypoxia (8% O2 of 1-hour, 3-hour, or 6-hour duration), performed 24 hours before ischemia, reduces infarct volume by approximately 30% when compared with controls. To elucidate the mechanisms underlying this neuroprotection, the authors investigated the effects of preconditioning on cerebral expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and its target genes, erythropoietin and vascular endothelial growth factor (VEGF). Hypoxia, whatever its duration (1 hour, 3 hours, 6 hours), rapidly increases the nuclear content of HIF-1alpha as well as the mRNA levels of erythropoietin and VEGF. Furthermore, erythropoietin and VEGF are upregulated at the protein level 24 hours after 6 hours of hypoxia. The authors' findings show that (1) hypoxia elicits a delayed, short-lasting (<72 hours) tolerance to focal permanent ischemia in the adult mouse brain; (2) HIF-1 target genes could contribute to the establishment of tolerance; and (3) this model might be a useful paradigm to further study the mechanisms of ischemic tolerance, to identify new therapeutic targets for stroke.

Gene therapy for acute diseases

The use of gene transfer systems to study cell function makes it apparent that overexpression of a transgene can restore or improve the function of a protein and positively influence cell function in a predetermined manner for purposes of counterbalancing cellular pathophysiology. The ability of some gene transfer vehicles to produce transgene product within hours of delivery positions gene transfer as a unique pharmaceutical administration system that can quickly affect production of biologic response modifiers in a highly compartmentalized fashion. This approach can be expected to overcome many of the adverse effects and high costs of systemic delivery of recombinant pharmaceuticals. This review highlights recent advances toward development of gene therapies for acute illnesses with particular emphasis on preclinical models of disease. In this context, a growing body of data suggests that gene therapies for polygenic and non-genetic diseases such as asthma, cardiogenic and non-cardiogenic pulmonary edema, stroke, subarachnoid hemorrhage, seizures, acute myocardial infarction, endovascular thrombosis, and infections may someday be options for the treatment of patients.

Gene therapy and the aging nervous system

In recent years, the first attempts have been made to apply gene transfer technology to protect neurons from death following neurological insults. There has been sufficient progress in this area that it becomes plausible to consider similar gene therapy approaches meant to delay aspects of aging of the nervous system. In this review, we briefly consider such progress and how it might be applied to the realm of the aging brain. Specifically, we consider: (a) the means of delivery of such therapeutic genes; (b) the choice of such genes; and (c) technical elaborations in gene delivery systems which can more tightly regulate the magnitude and duration of transgene protection.

Hypoxic preconditioning induces changes in HIF-1 target genes in neonatal rat brain

Hypoxic preconditioning induces tolerance to hypoxic-ischemic injury in neonatal rat brain and is associated with changes in gene expression. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that is strongly induced by hypoxia or the hypoxia-mimetic compound cobalt chloride (CoCl(2)). Hypoxia-inducible factor-1 modulates the expression of several target genes including the glycolytic enzymes, glucose transporter-1 (GLUT-1), and erythropoietin. Recently, HIF-1 expression was shown to increase after hypoxic and CoCl(2) preconditioning in newborn rat brain. To study the involvement of HIF-1 target genes in neonatal hypoxia-induced ischemic tolerance, the authors examined the brains of newborn rats after exposure to hypoxia (8% O(2) for 3 hours) or injection of CoCl(2) (60 mg/kg). Preconditioning with hypoxia or CoCl(2) 24 hours before hypoxia-ischemia afforded a 96% and 76% brain protection, respectively, compared with littermate control animals. Hypoxic preconditioning increased the expression of GLUT-1 mRNA and protein, and of aldolase, phosphofructokinase, and lactate dehydrogenase proteins but not mRNA. This suggests that the modulation of glucose transport and glycolysis by hypoxia may contribute to the development of hypoxia-induced tolerance. In contrast, preconditioning with CoCl(2) did not produce any change in HIF-1 target gene expression suggesting that different molecular mechanisms may be involved in the induction of tolerance by hypoxia and CoCl(2) in newborn brain.

Neuroprotective effects of an adenoviral vector expressing the glucose transporter: a detailed description of the mediating cellular events

Considerable knowledge exists concerning the events mediating neuron death following a necrotic insult; prompted by this, there have now been successful attempts to use gene therapy approaches to protect neurons from such necrotic injury. In many such studies, however, it is not clear what sequence of cellular events connects the overexpression of the transgene with the enhanced survival. We do so, exploring the effects of overexpressing the Glut-1 glucose transporter with an adenoviral vector in hippocampal cultures challenged with the excitotoxin kainic acid (KA). Such overexpression enhanced glucose transport, attenuated the decline in ATP concentrations, decreased the release of excitatory amino acid neurotransmitters, and decreased the total free cytosolic calcium load. Commensurate with these salutary effects, neuronal survival was enhanced with this gene therapy intervention. Thus, the neuroprotective effects of this particular gene therapy occurs within the known framework of the mechanisms of necrotic neuronal injury.

Gene therapy for treatment of cerebral ischemia using defective herpes simplex viral vectors

Significant advances have been made over the past few years concerning the cellular and molecular events underlying neuron death. Recently, it is becoming increasingly clear that some of the genes induced during cerebral ischemia may actually serve to rescue the cell from death. However, the injured cell may not be capable of expressing protein at levels high enough to be protective. One of the most exciting arenas of such interventions is the use of viral vectors to deliver potentially neuroprotective genes at high levels. Neurotrophic herpes simplex viral strains are an obvious choice for gene therapy to the brain, and we have utilized bipromoter vectors that are capable of transferring various genes to neurons. Using this system in experimental models of stroke, cardiac arrest and excitotoxicity, we have found that it is possible to enhance neuron survival against such cerebral insults by over-expressing genes that target various facets of injury. These include energy restoration by the glucose transporter (GLUT-1), buffering calcium excess by calbindin, preventing protein malfolding or aggregation by stress proteins and inhibiting apoptotic death by BCL-2. We show that in some cases, gene therapy is also effective after the onset of injury, and also address whether successful gene therapy necessarily spares function. Although gene therapy is limited to the few hundred cells the vector is capable of transfecting, we consider the possibility of such gene therapy becoming relevant to clinical neurology in the future.

Gene therapy for treatment of cerebral ischemia using defective herpes simplex viral vectors

Significant advances have been made over the past few years concerning the cellular and molecular events underlying neuron death. Recently, it is becoming increasingly clear that some of genes induced during cerebral ischemia may actually serve to rescue the cell from death. However, the injured cell may not be capable of expressing protein at high enough levels to be protective. One of the most exciting arenas of such interventions is the use of viral vectors to deliver potentially neuroprotective genes at high levels. Neurotropic herpes simplex viral (HSV) strains are an obvious choice for gene therapy to the brain, and we have used bipromoter vectors that are capable of transferring various genes to neurons. Using this system in experimental models of stroke, cardiac arrest, and excitotoxicity, we have found that it is possible to enhance neuron survival against such cerebral insults by overexpressing genes that target various facets of injury. These include energy restoration by the glucose transporter (GLUT-1), buffering calcium excess by calbindin, preventing protein malfolding or aggregation by stress proteins and inhibiting apoptotic death by BCL-2. We show that in some cases, gene therapy is also effective after the onset of injury, and also address whether successful gene therapy necessarily spares function. Although gene therapy is limited to the few hundred cells the vector is capable of transfecting, we consider the possibility of such gene therapy becoming relevant to clinical neurology in the future.

Calbindin d28k overexpression protects striatal neurons from transient focal cerebral ischemia

BACKGROUND AND PURPOSE

Increased intracellular calcium accumulation is known to potentiate ischemic injury. Whether endogenous calcium-binding proteins can attenuate this injury has not been clearly established, and existing data are conflicting. Calbindin D28K (CaBP) is one such intracellular calcium buffer. We investigated whether CaBP overexpression is neuroprotective against transient focal cerebral ischemia.

METHODS

Bipromoter, replication-incompetent herpes simplex virus vectors that encoded the genes for cabp and, as a reporter gene, lacZ were used. Sprague-Dawley rats received bilateral striatal injections of viral vector 12 to 15 hours before ischemia onset. With the use of an intraluminal occluding suture, animals were subjected to 1 hour of middle cerebral artery occlusion followed by 47 hours of reperfusion. Brains were harvested and stained with X-gal (to visualize beta-galactosidase, the gene product of lacZ). The number of remaining virally transfected, X-gal-stained neurons in both the ischemic and contralateral striata were counted and expressed as the percentage of surviving neurons in the ischemic striatum relative to the contralateral nonischemic striatum.

RESULTS

Striatal neuron survivorship among cabp-injected animals was 53.5+/-4.1% (n=10) versus 26.8+/-5.4% among those receiving lacZ (n=9) (mean+/-SEM; P<0.001).

CONCLUSIONS

We conclude that viral vector-mediated overexpression of CaBP leads to neuroprotection in this model of central nervous system injury. This is the first demonstration that CaBP overexpression protects neurons in a focal stroke model.