Effect of adenovirus-mediated nitric oxide synthase gene transfer on vasospasm after experimental subarachnoid hemorrhage

Tetrahydrobiopterin in cardiovascular health and disease

Tetrahydrobiopterin (BH4) functions as a cofactor for several important enzyme systems, and considerable evidence implicates BH4 as a key regulator of endothelial nitric oxide synthase (eNOS) in the setting of cardiovascular health and disease. BH4 bioavailability is determined by a balance of enzymatic de novo synthesis and recycling, versus degradation in the setting of oxidative stress. Augmenting vascular BH4 levels by pharmacological supplementation has been shown in experimental studies to enhance NO bioavailability. However, it has become more apparent that the role of BH4 in other enzymatic pathways, including other NOS isoforms and the aromatic amino acid hydroxylases, may have a bearing on important aspects of vascular homeostasis, inflammation, and cardiac function. This article reviews the role of BH4 in cardiovascular development and homeostasis, as well as in pathophysiological processes such as endothelial and vascular dysfunction, atherosclerosis, inflammation, and cardiac hypertrophy. We discuss the therapeutic potential of BH4 in cardiovascular disease states and attempt to address how this modulator of intracellular NO-redox balance may ultimately provide a powerful new treatment for many cardiovascular diseases.

Nitric oxide in cerebral vasospasm: theories, measurement, and treatment

In recent decades, a large body of research has focused on the role of nitric oxide (NO) in the development of cerebral vasospasm (CV) following subarachnoid hemorrhage (SAH). Literature searches were therefore conducted regarding the role of NO in cerebral vasospasm, specifically focusing on NO donors, reactive nitrogen species, and peroxynitrite in manifestation of vasospasm. Based off the assessment of available evidence, two competing theories are reviewed regarding the role of NO in vasospasm. One school of thought describes a deficiency in NO due to scavenging by hemoglobin in the cisternal space, leading to an NO signaling deficit and vasospastic collapse. A second hypothesis focuses on the dysfunction of nitric oxide synthase, an enzyme that synthesizes NO, and subsequent generation of reactive nitrogen species. Both theories have strong experimental evidence behind them and hold promise for translation into clinical practice. Furthermore, NO donors show definitive promise for preventing vasospasm at the angiographic and clinical level. However, NO augmentation may also cause systemic hypotension and worsen vasospasm due to oxidative distress. Recent evidence indicates that targeting NOS dysfunction, for example, through erythropoietin or statin administration, also shows promise at preventing vasospasm and neurotoxicity. Ultimately, the role of NO in neurovascular disease is complex. Neither of these theories is mutually exclusive, and both should be considered for future research directions and treatment strategies.

Tat peptide-decorated gelatin-siloxane nanoparticles for delivery of CGRP transgene in treatment of cerebral vasospasm

Background

Gene transfer using a nanoparticle vector is a promising new approach for the safe delivery of therapeutic genes in human disease. The Tat peptide-decorated gelatin-siloxane (Tat-GS) nanoparticle has been demonstrated to be biocompatible as a vector, and to have enhanced gene transfection efficiency compared with the commercial reagent. This study investigated whether intracisternal administration of Tat-GS nanoparticles carrying the calcitonin gene-related peptide (CGRP) gene can attenuate cerebral vasospasm and improve neurological outcomes in a rat model of subarachnoid hemorrhage.

Method

A series of gelatin-siloxane nanoparticles with controlled size and surface charge was synthesized by a two-step sol-gel process, and then modified with the Tat peptide. The efficiency of Tat-GS nanoparticle-mediated gene transfer of pLXSN-CGRP was investigated in vitro using brain capillary endothelial cells and in vivo using a double-hemorrhage rat model. For in vivo analysis, we delivered Tat-GS nanoparticles encapsulating pLXSN-CGRP intracisternally using a double-hemorrhage rat model.

Results

In vitro, Tat-GS nanoparticles encapsulating pLXSN-CGRP showed 1.71 times higher sustained CGRP expression in endothelial cells than gelatin-siloxane nanoparticles encapsulating pLXSN-CGRP, and 6.92 times higher CGRP expression than naked pLXSN-CGRP. However, there were no significant differences in pLXSN-CGRP entrapment efficiency and cellular uptake between the Tat-GS nanoparticles and gelatin-siloxane nanoparticles. On day 7 of the in vivo experiment, the data indicated better neurological outcomes and reduced vasospasm in the subarachnoid hemorrhage group that received Tat-GS nanoparticles encapsulating pLXSN-CGRP than in the group receiving Tat-GS nanoparticles encapsulating pLXSN alone because of enhanced vasodilatory CGRP expression in cerebrospinal fluid.

Conclusion

Overexpression of CGRP attenuated vasospasm and improved neurological outcomes in an experimental rat model of subarachnoid hemorrhage. Tat-GS nanoparticle-mediated CGRP gene delivery could be an innovative strategy for treatment of cerebral vasospasm after subarachnoid hemorrhage.

Developing a model of chronic subdural hematoma

Chronic subdural hematoma (CSDH) is a common neurosurgical condition that has a high incidence in the increasing elderly population of many countries. Pathologically, it is defined as a persistent liquefied hematoma in the subdural space more than 3 weeks old that is generally encased by a membraneous capsule. CSDHs likely originate after minor head trauma, with a key factor in its development being the potential for a subdural cavity to permit its expansion within, which is usually due to craniocerebral disproportion. The pathogenesis of CSDH has been attributed to osmotic or oncotic pressure differences, although measurements of these factors in the CSDH fluid do not support this theory. Current belief is that CSDH arises from recurrent bleeding in the subdural space, caused by a cycle of local angiogenesis, inflammation, coagulation and ongoing fibrinolysis. However, because of a lack of detailed knowledge about the precise mechanisms, treatment is often limited to surgical interventions that are invasive and often prone to recurrence. Thus, it is possible that an easily reproducible and representative animal model of CSDH would facilitate research in the pathogenesis of CSDH and aid with development of treatment options.

Aminoguanidine inhibition of iNOS activity ameliorates cerebral vasospasm after subarachnoid hemorrhage in rabbits via restoration of dysfunctional endothelial cells

BACKGROUND

This study was to delineate the therapeutic efficacy and potential cellular and molecular mechanisms of aminoguanidine (AG), a relatively selective inhibitor of iNOS activity, in cerebral vasospasm after subarachnoid hemorrhage (SAH) in rabbits.

METHODS

SAH was induced by a single injection of autologous arterial blood into the cisterna magna of adult male rabbits. An intravenous bolus injection of AG (150 mg/kg) was administrated 1h after SAH, and this dosage was repeated on the following day. Vasospasm was verified by computed tomography angiography (CTA) day 2 after SAH. Rabbit basilar arteries were harvested for transmission electron microscopy (TEM), immunohistochemical examination, RT-PCR, and western blot analysis.

RESULTS

CTA data revealed that cerebral vasospasm of SAH rabbits was significantly prevented via AG treatment. TEM results demonstrated the ultrastructural morphological changes of endothelial cells of SAH rabbits were ameliorated by AG treatment. In parallel, AG treatment increased eNOS mRNA and protein levels along with the reduced immunoreactivity of nitrotyrosine in rabbit basilar arteries.

CONCLUSIONS

Our discovery suggested AG inhibition of iNOS activity could significantly reverse cerebral vasospasm after SAH via restoration of dysfunctional endothelial cells by the upregulation of eNOS, indicating a regulatory cross-talk between eNOS and iNOS in the pathogenesis of SAH.

Effect of vasodilation by milrinone, a phosphodiesterase III inhibitor, on vasospastic arteries after a subarachnoid hemorrhage in vitro and in vivo: effectiveness of cisternal injection of milrinone

OBJECTIVE

Cerebral vasospasm remains a major cause of morbidity and mortality. Milrinone, a bipyridine phosphodiesterase III inhibitor, is a potent member of the inodilator class of cardiac agents for vasospasm and is injected intra-arterially or intracisternally. There have been no studies investigating the duration of action (context-sensitive half-life) of milrinone for vasospasm or the most effective route of administration (intra-arterial versus intracisternal). We examined the effects of intracisternal and intra-arterial injection of milrinone on chronic cerebral vasospasm in dogs.

METHODS

A double-hemorrhage canine model was used. In a preliminary isometric tension study of canine vasospastic basilar arteries, the vasodilatory effects of milrinone were examined 7 days after an initial injection of blood. Milrinone was injected intracisternally (0.1 mg, 0.47 mmol/L) or intra-arterially (0.3 mg/kg, 1.2 mmol/L), and angiograms were performed 30, 60, 120, 180, 240, 300, and 360 minutes later on day 7.

RESULTS

Milrinone produced concentration-dependent vasodilation and was effective intracisternally, resulting in significant dilation until 180 minutes after injection and a tendency for dilation until 240 minutes. The effect of intra-arterial injection was not as significant compared with an intracisternal injection, resulting in significant dilation only at 180 minutes after intra-arterial injection.

CONCLUSION

Intracisternal injection of milrinone was more effective than intra-arterial injection for chronic cerebral vasospasm in dogs because intracisternal injection produced a higher concentration in vasospastic arteries (0.034-0.068 mmol/L intracisternally versus 0.016 mmol/L intra-arterially).

Neuronal and astrocytic apoptosis after subarachnoid hemorrhage: a possible cause for poor prognosis

Clinical evidence suggests that factors other than cerebral vasospasm, such as delayed neuronal and astrocytic cell death, may play a role in the poor prognosis of patients with subarachnoid hemorrhage (SAH). Here we examined this using immunohistochemistry and confocal microscopy in 3 different brain areas in a dog model of SAH. Using antibodies against neuronal marker neuronal nuclear protein (NeuN) and astrocyte marker glial fibrillary acidic protein (GFAP) in conjunction with apoptosis marker (cleaved caspase-3), we quantified neurons and astrocytes to monitor the degree of apoptosis in both groups. Experimental SAH group showed 44 +/- 1% caspase-3 positive neurons in comparison to the 2.0 +/- 0.1% in the control group (P < 0.001, 6 animals each group). For astrocytes, a total 25 +/- 1% were caspase-3 positive in day 7 SAH group, as compared to 0.40 +/- 0.01% for controls (P < 0.001). Regional analysis revealed that neuronal caspase-3 immunoreactivity in all 3 regions were significantly higher (P < 0.001) in SAH animals than that in the control animals. However, the analysis of total area, size and signal co-localization of GFAP with caspase-3 indicated that astrocytic reactivity and proliferation are seen primarily in the hippocampal area, with the least changes detectable in the brainstem. We conclude that in the dog model, there was a significant increase of neuronal and astrocytic cleaved caspase-3, possibly reflecting apoptosis, following SAH induction. These changes coupled with neurological deterioration seen in patients may present a possible reason for the poor outcome in SAH patients.

Biological approaches to ischemic tissue repair: gene- and cell-based strategies

Gene therapy is a potential therapeutic strategy for treatment of ischemic vascular diseases; however, the clinical application of gene therapy has met some anticipated challenges. Recent randomized, controlled trials suggest that patients with cardiovascular disease may also benefit from cell-based therapies, and the optimal treatment regimen may combine both approaches to take advantage of potential synergy between the underlying therapeutic mechanisms. This review discusses recent research into both gene and cell therapy and considers the potential application of a combined treatment approach for cardiovascular and cerebrovascular ischemic diseases.

Dysfunction of nitric oxide synthases as a cause and therapeutic target in delayed cerebral vasospasm after SAH

Nitric oxide (NO), also known as endothelium-derived relaxing factor, is produced by endothelial nitric oxide synthase (eNOS) in the intima and by neuronal nitric oxide synthase (nNOS) in the adventitia of cerebral vessels. It dilates the arteries in response to shear stress, metabolic demands, pterygopalatine ganglion stimulation, and chemoregulation. Subarachnoid haemorrhage (SAH) interrupts this regulation of cerebral blood flow. Hemoglobin, gradually released from erythrocytes in the subarachnoid space destroys nNOS-containing neurons in the conductive arteries. This deprives the arteries of NO, leading to the initiation of delayed vasospasm. But such vessel narrowing increases shear stress, which stimulates eNOS. This mechanism normally would lead to increased production of NO and dilation of arteries. However, a transient eNOS dysfunction evoked by an increase of the endogenous competitive nitric oxide synthase (NOS) inhibitor, asymmetric dimethyl-arginine (ADMA), prevents this vasodilation. eNOS dysfunction has been recently shown to be evoked by increased levels of ADMA in CSF in response to the presence of bilirubin-oxidized fragments (BOXes). A direct cause of the increased ADMA CSF level is most likely decreased ADMA elimination due to the disappearance of ADMA-hydrolyzing enzyme (DDAH II) immunoreactivity in the arteries in spasm. This eNOS dysfunction sustains vasospasm. CSF ADMA levels are closely associated with the degree and time-course of vasospasm; when CSF ADMA levels decrease, vasospasm resolves. Thus, the exogenous delivery of NO, inhibiting the L-arginine-methylating enzyme (IPRMT3) or stimulating DDAH II, may provide new therapeutic modalities to prevent and treat vasospasm. This paper will present results of preclinical studies supporting the NO-based hypothesis of delayed cerebral vasospasm development and its prevention by increased NO availability.

Dysfunction of nitric oxide synthases as a cause and therapeutic target in delayed cerebral vasospasm after SAH

Nitric oxide (NO), also known as endothelium-derived relaxing factor, is produced by endothelial nitric oxide synthase (eNOS) in the intima and by neuronal nitric oxide synthase (nNOS) in the adventitia of cerebral vessels. It dilates the arteries in response to shear stress, metabolic demands, pterygopalatine ganglion stimulation and chemoregulation. Subarachnoid hemorrhage (SAH) interrupts this regulation of cerebral blood flow. Hemoglobin, gradually released from erythrocytes in the subarachnoid space, destroys nNOS-containing neurons in the conductive arteries. This deprives the arteries of NO, leading to initiation of delayed vasospasm. But such vessel narrowing increases shear stress, which stimulates eNOS. This mechanism normally would lead to increased production of NO and dilation of arteries. However, a transient eNOS dysfunction evoked by an increase in the endogenous competitive NOS inhibitor, asymmetric dimethylarginine (ADMA), prevents this vasodilation. eNOS dysfunction has been recently shown to be evoked by increased levels of ADMA in cerebrospinal fluid (CSF) in response to the presence of bilirubin-oxidized fragments (BOXes). A direct cause of the increased ADMA CSF level is most likely decreased ADMA elimination owing to disappearance of ADMA-hydrolyzing enzyme [dimethylarginine dimethylaminohydrolase II (DDAH II)] immunoreactivity in the arteries in spasm. This eNOS dysfunction sustains vasospasm. CSF ADMA levels are closely associated with the degree and time course of vasospasm; when CSF ADMA levels decrease, vasospasm resolves. Thus, exogenous delivery of NO, inhibiting the L-arginine-methylating enzyme or stimulating DDAH II, may provide new therapeutic modalities to prevent and treat vasospasm. This paper will present results of pre-clinical studies supporting the NO-based hypothesis of delayed cerebral vasospasm development and its prevention by increased NO availability.

PERSISTENCE OF THE NITRIC OXIDE-DEPENDENT VASODILATORPATHWAY OF CEREBRAL VESSELS AFTEREXPERIMENTAL SUBARACHNOID HEMORRHAGE

OBJECTIVE

Efficiency of the treatment of cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) by interfering with the nitric oxide-cyclic guanosine monophospate (cGMP) pathway seems to be inconsistent. So far, it remains unclear whether or not insufficient access to the drugs or impaired reactivity of the vessels is responsible for this inconsistency. Therefore, the aim of the present investigation was to characterize this pathway on cerebral arteries during CVS.

METHODS

CVS was induced using the rat double hemorrhage model and was determined by magnetic resonance perfusion weighted imaging. Rats were sacrificed on Day 3 and Day 5 after SAH. Immunohistochemical staining of the basilar artery for endothelial nitric oxide synthases and the alpha- and beta-subunits of the soluble guanylate cyclase was performed. Basilar artery ring segments on Day 5 were used for measurement of isometric force. Concentration effect curves for acetylcholine, sodium nitroprusside, and 8-bromo-cGMP were constructed and compared by maximum effect and pD2.

RESULTS

The immunohistochemical expression of endothelial nitric oxide synthase was comparable in all groups. The soluble guanylate cyclase alpha- and beta-subunits were significantly diminished on Day 3, but recovered by Day 5. The relaxation attributable to acetylcholine and 8-bromo-cGMP was virtually identical in controls and during CVS. Relaxation attributable to sodium nitroprusside, however, was significantly enhanced after SAH (maximum effect, control: 88 +/- 12%; Day 5: 117 +/- 26%).

CONCLUSION

The present investigations suggest the persistence of endothelium-, nitric oxide-, and cGMP-dependent relaxation during CVS. Therefore, the treatment of CVS interfering with this pathway seems not to be limited by alterations inside the vessel wall.

Nitric oxide in subarachnoid haemorrhage and its therapeutics implications

BACKGROUND

After the discovery that nitric oxide (NO) plays a major role in the regulation of vascular tone, this substance moved into the focus of interest with regard to vasospasm after subarachnoid haemorrhage (SAH). A multitude of interactions were discovered and some concepts of therapeutic intervention were developed.

METHOD

The present review is based on a Medline search with the terms "nitric oxide" and "subarachnoid haemorrhage".

FINDINGS

SAH and particularly liberated oxyhaemoglobin sequestrate the physiologically produced NO. Reactivity to NO appears to be principally preserved. As other types of injury, SAH leads to induction of inducible NO synthase (iNOS). The NO produced by this pathway cannot compensate for the lack of the physiological NO and may even lead to tissue damage by oxidative stress. Experimental therapeutic attempts use stimulation of NO production and delivery of NO donors. NO donors were also used in some small clinical trials. A final assessment of efficacy and safety is not yet possible.

CONCLUSION

NO physiology and pathophysiology are important in the genesis of vasospasm after subarachnoid haemorrhage. NO directed therapeutic strategies enlarge the spectrum of available instruments, but complete elimination of the problem of vasospasm cannot be expected.

Gene technology based therapies in the brain

Gene therapy potentially represents one of the most important developments in modern medicine. Gene therapy, especially of cancer, has created exciting and elusive areas of therapeutic research in the past decade. In fact, the first gene therapy performed in a human was not against cancer but was performed to a 14 year old child suffering from adenosine deaminase (ADA) deficiency. In addition to cancer gene therapy there are many other diseases and disorders where gene therapy holds exciting and promising opportunities. These include amongst others gene therapy within the central nervous system and the cardiovascular system. Improvements of the efficiency and safety of gene therapy is the major goal of gene therapy development. After the death of Jesse Gelsinger, the first patient in whom death could be directly linked to the viral vector used for the treatment, ethical doubts were raised about the feasibility of gene therapy in humans. Therefore, the ability to direct gene transfer vectors to specific target cells is also a crucial task to be solved and will be important not only to achieve a therapeutic effect but also to limit potential adverse effects.

Targeting cerebral arteries for gene therapy

After the steady progress towards application of gene therapy to cerebral arterial diseases, several applications, including modification of gene expression in cerebral arteries, are now feasible. There are several possible targets for cerebrovascular gene therapy, and numerous studies have tested gene therapy strategies in animal models of cerebrovascular disorders. However, some major obstacles, especially issues of safety, must be overcome before clinical use in humans. Gene therapy for cerebral arterial diseases is still in its infancy, and many basic and preclinical studies are yet to be done in order to develop effective and safe techniques.

Translational paradigms in cerebrovascular gene transfer

Gene transfer involves the use of an engineered biologic vehicle known as a vector to introduce a gene encoding a protein of interest into a particular tissue. In diseases with known defects at a genetic level, gene transfer offers a potential means of restoring a normal molecular environment via vector-mediated entry (transduction) and expression of genes encoding potentially therapeutic proteins selectively in diseased tissues. The technology of gene transfer therefore underlies the concept of gene therapy and falls under the umbrella of the current genomics revolution. Particularly since 1995, numerous attempts have been made to introduce genes into intracranial blood vessels to demonstrate and characterize viable transduction. More recently, in attempting to translate cerebrovascular gene transfer technology closer to the clinical arena, successful transductions of normal human cerebral arteries ex vivo and diseased animal cerebral arteries in vivo have been reported using vasomodulatory vectors. Considering the emerging importance of gene-based strategies for the treatment of the spectrum of human disease, the goals of the present report are to overview the fundamentals of gene transfer and review experimental studies germane to the clinical translation of a technology that can facilitate genetic modification of cerebral blood vessels.

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.

Effects of a nitric oxide donor on and correlation of changes in cyclic nucleotide levels with experimental vasospasm

OBJECTIVE

Vasospasm after subarachnoid hemorrhage (SAH) may result from hemoglobin-mediated removal of nitric oxide (NO) from the arterial wall. We tested the ability of the long-acting, water-soluble, NO donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-1,2-diolate (DETA/NO), delivered via continuous intracisternal infusion, to prevent vasospasm in a nonhuman primate model of SAH.

METHODS

First, vasorelaxation in response to DETA/NO was characterized in vitro by using monkey basilar artery rings under isometric tension. Next, monkeys were randomized to undergo angiography, unilateral SAH, and no treatment (SAH only, n = 4) or treatment with DETA/NO (1 mmol/L, 12 ml/d, n = 4) or decomposed DETA/NO (at the same dose, n = 4). Vasospasm was assessed by angiography, which was performed on Day 0 and Day 7. Levels of cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) were measured in cerebral arteries on Day 7.

RESULTS

DETA/NO produced significant relaxation of monkey arteries in vitro, which reached a maximum at concentrations of 10(-5) mol/L. In monkeys, angiography demonstrated significant vasospasm of the right intradural cerebral arteries in all three groups, with no significant difference in vasospasm among the groups (P > 0.05, analysis of variance). The ratios of cGMP or cyclic adenosine monophosphate levels in the right and left middle cerebral arteries were not different among the groups (P > 0.05, analysis of variance). There was no significant correlation between arterial cGMP contents and the severity of vasospasm.

CONCLUSION

DETA/NO did not prevent vasospasm. There was no correlation between the severity of vasospasm and cyclic adenosine monophosphate and cGMP levels in the cerebral arteries. These results suggest that events downstream of cyclic nucleotides may be abnormal during vasospasm.

Posttreatment with adenovirus-mediated gene transfer of calcitonin gene-related peptide to reverse cerebral vasospasm in dogs

OBJECT

Gene transfer to cerebral vessels is a promising new therapeutic approach for cerebral vasospasm after subarachnoid hemorrhage (SAH). This study was undertaken to explore whether a delayed treatment with adenovirus encoding the prepro-calcitonin gene-related peptide (CGRP), 2 days after initial blood injection, reduces cerebral vasospasm in a double-hemorrhage model of severe vasospasm in dogs.

METHODS

In 20 dogs, arterial blood was injected into the cisterna magna on Days 0 and 2. Thirty minutes after the second blood injection, the animals received either adenovirus encoding the prepro-CGRP gene (AdCMVCGRP-treated group, eight dogs) or adenovirus encoding the beta-galactosidase gene (AdCMVbeta gal-treated group, six dogs) under the cytomegalovirus (CMV) promoter. One group of dogs did not receive treatment and served as controls (control SAH group, six dogs). Angiography was performed on Days 0 and 7 to assess cerebral vasospasm. On Day 7 following angiography, the animals were killed and their brains were stained with X-gal to detect the distribution of gene expression. Cerebrospinal fluid (CSF) was also tested for CGRP immunoreactivity. Severe vasospasm was observed in control SAH dogs on Day 7, and the mean basilar artery (BA) diameter was 53.4 +/- 5.5% of the value measured on Day 0. Treatment with AdCMVbeta gal did not alter vasospasm (the BA diameter was 55 +/- 3.9% of that measured on Day 0). The leptomeninges and adventitia of the BAs of dogs treated using AdCMVbeta gal demonstrated positive staining with X-gal. High levels of CGRP were measured in CSF from dogs that received AdCMVCGRP. In the group treated with AdCMVCGRP, vasospasm was significantly reduced (the BA diameter was 78.2 +/- 5.3% of that measured on Day 0, p < 0.05 compared with the control SAH group and the AdCMVbeta gal group).

CONCLUSIONS

In a model of severe vasospasm in dogs, gene transfer of CGRP after injection of blood attenuated cerebral vasospasm after SAH.

Heme oxygenase-1 gene therapy for prevention of vasospasm in rats

OBJECT

Hemoglobin causes contraction of cerebral arteries and is also believed to cause vasospasm after subarachnoid hemorrhage (SAH). The goal in this study was to determine if overexpression of heme oxygenase-1 (HO-1), the principal enzyme involved in the metabolism of hemoglobin, would reduce contractions of cerebral arteries brought on by hemoglobin and decrease vasospasm after experimental SAH.

METHODS

Injection of adenovirus expressing HO-1 (Ad5HO-1) into the cisterna magna of rats produced a significant increase in expression of HO-1 messenger RNA, and protein and HO-1 activity in the basilar artery ([BA]; p < 0.05 for each measure compared with vehicle and/or control virus, according to analysis of variance or unpaired t-test). Injection of adenovirus expressing beta-galactosidase (Ad-betaGal) produced only mild, statistically nonsignificant increases. The HO-I immunoreactivity was localized to the BA adventitia after injection of Ad5HO-1 or Ad-betaGal. Injection of Ad5HO-1 and Ad-betaGal increased the baseline diameter of the BA (measured directly via a transclival window) and brainstem cerebral blood flow (CBF), measured by laser Doppler flowmetry, compared with vehicle. Contraction of the BA after addition of hemoglobin was significantly inhibited, reduction in brainstem CBF was significantly prevented, and carboxyhemoglobin concentration was significantly increased in rats injected with Ad5HO-1 compared with Ad-betaGal and vehicle. Vasospasm was significantly ameliorated in rats in which Ad5HO-1 was injected into the cisterna magna at the time of SAH in a double-hemorrhage model.

CONCLUSIONS

These results show that overexpression of HO-1 inhibits arterial contractions induced by hemoglobin and can reduce vasospasm after experimental SAH.

Vasospasm, its role in the pathogenesis of diseases with particular reference to the eye

Vasospasm can have many different causes and can occur in a variety of diseases, including infectious, autoimmune, and ophthalmic diseases, as well as in otherwise healthy subjects. We distinguish between the primary vasospastic syndrome and secondary vasospasm. The term "vasospastic syndrome" summarizes the symptoms of patients having such a diathesis as responding with spasm to stimuli like cold or emotional stress. Secondary vasospasm can occur in a number of autoimmune diseases, such as multiple sclerosis, lupus erythematosus, antiphospholipid syndrome, rheumatoid polyarthritis, giant cell arteritis, Behcet's disease, Buerger's disease and preeclampsia, and also in infectious diseases such as AIDS. Other potential causes for vasospasm are hemorrhages, homocysteinemia, head injury, acute intermittent porphyria, sickle cell disease, anorexia nervosa, Susac syndrome, mitochondriopathies, tumors, colitis ulcerosa, Crohn's disease, arteriosclerosis and drugs. Patients with primary vasospastic syndrome tend to suffer from cold hands, low blood pressure, and even migraine and silent myocardial ischemia. Valuable diagnostic tools for vasospastic diathesis are nailfold capillary microscopy and angiography, but probably the best indicator is an increased plasma level of endothelin-1. The eye is frequently involved in the vasospastic syndrome, and ocular manifestations of vasospasm include alteration of conjunctival vessels, corneal edema, retinal arterial and venous occlusions, choroidal ischemia, amaurosis fugax, AION, and glaucoma. Since the clinical impact of vascular dysregulation has only really been appreciated in the last few years, there has been little research in the according therapeutic field. The role of calcium channel blockers, magnesium, endothelin and glutamate antagonists, and gene therapy are discussed.

Review of medical prevention of vasospasm after aneurysmal subarachnoid hemorrhage: a problem of neurointensive care

Cerebral vasospasm remains a devastating medical complication of aneurysmal subarachnoid hemorrhage (SAH). It is associated with high morbidity and mortality rates, even after the aneurysm has been secured surgically or radiologically. A great deal of experimental and clinical research has been conducted in an effort to find ways to prevent this complication. The literature includes extensive coverage of in vivo animal model studies of SAH and vasospasm. These experimental studies have contributed to tremendous advances in the understanding of the mechanisms leading to cerebral vasospasm. Most of the experimental settings, however, have demonstrated varying levels of ability to predict accurately what occurs in human SAH. Therefore, although animal models have been developed to test new therapies, most of the treatment effects have been shown to be less compelling when trials have been conducted in clinical settings. The interpretation of current literature is complicated further by the imprecise estimation of the incidence of cerebral vasospasm, which is due to various degrees of clinical expression, ranging from the absence of symptoms in the presence of increased blood flow velocities at transcranial Doppler or vessel diameter reduction at angiography to neurological manifestations of severe ischemic deficits. In addition, a change over time in the incidence pattern of human SAH and vasospasm, possibly related to improved surgical techniques and overall patient management, may have occurred. This topic review collects the relevant literature on clinical trials investigating prophylactic therapies for cerebral vasospasm in patients with aneurysmal SAH and emphasizes the need for large clinical trials to confirm the results derived from clinical experience. In addition, it points out some experimental therapies that may hold promise in future clinical trials to prevent the occurrence of vasospasm.

The future of gene therapy for stroke

New diagnostic and treatment strategies are being developed for stroke. Gene therapy has several potential advantages over classical pharmacologic therapy. Direct administration of DNA into the brain offers the advantage of producing high concentrations of therapeutic agents in a relatively localized environment. Gene transfer also provides longer duration of effect than traditional drug therapy. Recent studies indicate that gene transfer can produce functional proteins in brain parenchyma and cerebral blood vessels after stroke. In animal models, gene transfer may reduce effects of cerebral ischemia or subarachnoid hemorrhage. This review summarizes some current methods of gene transfer to the brain and recent progress that may lead to gene therapy for stroke.

Gene transfer for cerebrovascular disease

Gene transfer is a powerful, evolving technique that uses a biologic vehicle (eg, an engineered adenovirus) to introduce a specific gene of interest (ie, a recombinant gene) into a target tissue. This approach, which has considerable therapeutic potential, underlies the concept of gene therapy. Several studies have characterized the morphologic, biochemical, and functional effects of recombinant gene expression in animal and human cerebral arteries, and support the possibility of gene therapy for cerebrovascular disease. However, for successful integration into future clinical practice, key issues concerning vector safety, delivery methods, and transduction specificity need to be addressed. Alongside completion of the Human Genome Project, transfer of novel genes into the central nervous system is likely to impact greatly on our ability to favorably modify diseased human tissue. Knowledge of the fundamental concepts of cerebrovascular gene transfer is therefore useful to understanding both its molecular basis and potential clinical utility.

Adenoviral gene transfer of nitric oxide synthase increases cerebral blood flow in rats

OBJECTIVE

Depletion of nitric oxide may play a role in the development of vasospasm after aneurysmal subarachnoid hemorrhage. Replenishment of nitric oxide might be a useful treatment for vasospasm. Using rats, we performed intracisternal injections of replication-defective adenovirus containing the endothelial nitric oxide synthase (eNOS) gene and determined the localization of and effect on cerebral blood flow of transgene expression.

METHODS

Rats underwent baseline measurement of cortical cerebral blood flow using laser Doppler flowmetry. Replication-defective adenovirus containing the Escherichia coli LacZ gene (Ad327beta-Gal, n = 2/time point) or the bovine eNOS gene (AdCD8-NOS, n = 4/time point) or physiological saline solution was injected into the cisterna magna. Cerebral blood flow was measured 1, 2, 4, 7, or 14 days later, and the animals were killed. Expression of beta-galactosidase activity from the LacZ gene was examined by histochemical staining and that of eNOS was examined by polymerase chain reaction assays of messenger ribonucleic acid. Brains were histopathologically examined for inflammation.

RESULTS

Beta-galactosidase activity was observed throughout the leptomeninges and in some cells in the adventitia of small subarachnoid blood vessels in the Ad327beta-Gal-injected rats. Messenger ribonucleic acid for eNOS was detected in the leptomeninges and brainstem 1 and 2 days after injection of AdCD8-NOS. Rats injected with Ad327beta-Gal or physiological saline solution exhibited decreased cerebral blood flow beginning 2 days after virus injection and lasting up to 14 days after injection. Rats injected with AdCD8-NOS developed significant transient increases in cerebral blood flow 2 days after virus injection, followed by slight decreases in blood flow. There was inflammation in the subarachnoid space of all animals; the inflammation was qualitatively worse in animals injected with Ad327beta-Gal, compared with rats injected with AdCD8-NOS or saline solution.

CONCLUSION

Intracisternal injection of replication-defective adenovirus containing the eNOS gene can transiently increase cerebral blood flow.