To Be-et, or Not to Be-et, That is the Question: The Role(s) of Nitrate and Nitrite in Health and Illness.

BACKGROUND: This manuscript addresses the multilevel role of dietary nitrate and nitrite in health and diseases because of increased interest in dietary supplementation. METHOD: Review of research devoted to both beneficial but also possible deleterious effects of uncontrolled indigestion of red beet-root juice and other sources of high concentrated nitrate and nitrite. RESULTS: The body of evidence strongly suggested that persons using nitrate/nitrite supplementation and particularly patients treated with sodium nitrite, having kidney disease or impaired methemoglobin reeducates activity, should closely monitor nitrate/nitrite indigestion. CONCLUSION: Oral intake of red beet-root juice, green leaved veggies, cured meat, as well as urine excretion of nitrate/ nitrite, methemoglobin reeducates activity should be carefully assessed especially in patients treated with sodium nitrite.

Molsidomine for the prevention of vasospasm-related delayed ischemic neurological deficits and delayed brain infarction and the improvement of clinical outcome after subarachnoid hemorrhage: a single-center clinical observational study.

OBJECT Delayed ischemic neurological deficits (DINDs) and cerebral vasospasm (CVS) are responsible fora poor outcome in patients with aneurysmal subarachnoid hemorrhage (SAH), most likely because of a decreased availability of nitric oxide (NO) in the cerebral microcirculation. In this study, the authors examined the effects of treatment with the NO donor molsidomine with regard to decreasing the incidence of spasm-related delayed brain infarctions and improving clinical outcome in patients with SAH. METHODS Seventy-four patients with spontaneous aneurysmal SAH were included in this post hoc analysis. Twenty-nine patients with SAH and proven CVS received molsidomine in addition to oral or intravenous nimodipine. Control groups consisted of 25 SAH patients with proven vasospasm and 20 SAH patients without. These patients received nimodipine therapy alone. Cranial computed tomography (CCT) before and after treatment was analyzed for CVS-related infarcts. A modified National Institutes of Health Stroke Scale (mNIHSS) and the modified Rankin Scale (mRS) were used to assess outcomes at a 3-month clinical follow-up. RESULTS Four of the 29 (13.8%) patients receiving molsidomine plus nimodipine and 22 of the 45 (48%) patients receiving nimodipine therapy alone developed vasospasm-associated brain infarcts (p < 0.01). Follow-up revealed a median mNIHSS score of 3.0 and a median mRS score of 2.5 in the molsidomine group compared with scores of 11.5 and 5.0, respectively, in the nimodipine group with CVS (p < 0.001). One patient in the molsidomine treatment group died, and 12 patients in the standard care group died (p < 0.01). CONCLUSIONS In this post hoc analysis, patients with CVS who were treated with intravenous molsidomine had a significant improvement in clinical outcome and less cerebral infarction. Molsidomine offers a promising therapeutic option in patients with severe SAH and CVS and should be assessed in a prospective study.

Blood clot placement model of subarachnoid hemorrhage in non-human primates.

Despite ongoing extensive and promising research to prevent and treat cerebrovascular vasospasm and delayed ischemic neurological deficits (DIND) after aneurysmal subarachnoid hemorrhage (aSAH), clinical outcomes remain unsatisfying. Neuroprotective strategies developed in basic science research laboratories need to be translated from bench-to-bedside using appropriate animal models. While a primate model is widely accepted as the best animal model mimicking development of delayed cerebral vasospasm after aSAH, its worldwide usage has dramatically decreased because of ethical and financial limitations. However, the use of primate models of subarachnoid hemorrhage (SAH) remains a recommended bridge for translation of early preclinical studies in rodents to human clinical trials. This paper discusses the technical aspects as well as advantages and disadvantages of a blood clot placement model of subarachnoid hemorrhage in non-human primates.

A non-human primate model of aneurismal subarachnoid hemorrhage (SAH).

Aneurismal subarachnoid hemorrhage (SAH) is relatively rare form of hemorrhagic stroke, which produces significant social and medical challenges. As it affects people in their high productivity age and leaves 50 % of them dead and almost 70 % of survivors disabled, many of them severely, the reasons of such a dismal outcome have been intensively researched all over the world. Nevertheless, despite more than a half a century of clinical and scientific effort and dramatic improvement of surgical repair of aneurysms, the causes of poor outcome remain enigmatic. Introduction of numerous in vitro and in vivo models to study the unleashed by SAH mechanisms that injured the brain significantly advanced our understanding of biology of cerebral vessels, brain responses to intracranial pressure changes, and the presence of blood clot in subarachnoid space. One of the most important animal models that significantly contributed to those advances has been a non-human primate model introduced at the Bryce Weir laboratory in the University of Alberta, Canada, in 1984. Since then, this model, with some modifications, has been successfully used in several animal laboratories in the USA, Canada, and Japan. We present the model characteristics and describe in details medical, surgical, imagining techniques that we have used at the Surgical Neurology Branch of the National Institute of Neurological Disorders and Stroke from 1989.

Aneurysmal subarachnoid hemorrhage models: do they need a fix?

The discovery of tissue plasminogen activator to treat acute stroke is a success story of research on preventing brain injury following transient cerebral ischemia (TGI). That this discovery depended upon development of embolic animal model reiterates that proper stroke modeling is the key to develop new treatments. In contrast to TGI, despite extensive research, prevention or treatment of brain injury following aneurysmal subarachnoid hemorrhage (aSAH) has not been achieved. A lack of adequate aSAH disease model may have contributed to this failure. TGI is an important component of aSAH and shares mechanism of injury with it. We hypothesized that modifying aSAH model using experience acquired from TGI modeling may facilitate development of treatment for aSAH and its complications. This review focuses on similarities and dissimilarities between TGI and aSAH, discusses the existing TGI and aSAH animal models, and presents a modified aSAH model which effectively mimics the disease and has a potential of becoming a better resource for studying the brain injury mechanisms and developing a treatment.

Prolonged intravenous infusion of sodium nitrite delivers nitric oxide (NO) in humans.

In preclinical studies, infusion of sodium nitrite delivers nitric oxide (NO) as treatment of vasospasm after subarachnoid hemorrhage. We evaluated safety and toxicity of intravenous nitrite administration in healthy volunteers infused with increasing doses of sodium nitrite for 48 h. Twelve volunteers (5 men, 7 women; mean age was 38.8 years, range 27-56 years) participated in the study. The starting sodium nitrite dose was 4.2 mg/kg/h, and it was doubled for each subsequent volunteer up to a maximal dose of 533.8 mg/kg/h at which a clinically silent dose-limiting toxicity (DLT) was observed. Toxicity included a transient decrease of mean arterial blood pressure or asymptomatic increase of methemoglobin level above 5%. The maximal tolerated dose (MTD) was 267 mg/kg/h. S-Nitrosothiols increased significantly in plasma, confirming in vivo sodium nitrite reduction to NO and encouraging its use against vasospasm and ischemia-reperfusion injury to the brain, kidneys, liver, and heart.

Relevance of animal models of subarachnoid hemorrhage for examining neurobehavioral changes.

BACKGROUND AND PURPOSE: For many years survival and neurological functionality of patients were the main outcome measures after treatment of intracranial aneurysms. But, the variable outcomes of patients operated on in a delayed fashion or before the aneurysm rupture indicate that more precise measures are needed for assessment of not only the neurological but also the neuropsychological outcome. However, development and testing of such new tools requires better understanding of pathomechanisms of neurobehavioral changes evoked by aneurysmal subarachnoid hemorrhage (aSAH), which can be achieved using animal models. METHODS: We reviewed and selected (1) animal models developed to investigate delayed cerebral vasospasm that could be useful for examining effects of brain injury evoked by aSAH and (2) a battery of neurobehavioral animal testing that can be used for assessment of patients after aSAH. RESULTS: For every species used as an aSAH model, a battery of neurobehavioral test exists. CONCLUSION: Albeit some limitations must be recognized, research using animal models of SAH should continue to play a critical role in assessment of cognitive and behavioral functions after aSAH.

The importance of early brain injury after subarachnoid hemorrhage.

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Reversal of cerebral vasospasm via intravenous sodium nitrite after subarachnoid hemorrhage in primates.

OBJECT: Subarachnoid hemorrhage (SAH)-induced vasospasm is a significant underlying cause of aneurysm rupture-related morbidity and death. While long-term intravenous infusion of sodium nitrite (NaNO(2)) can prevent cerebral vasospasm after SAH, it is not known if the intravenous administration of this compound can reverse established SAH-induced vasospasm. To determine if the intravenous infusion of NaNO(2) can reverse established vasospasm, the authors infused primates with the compound after SAH-induced vasospasm was established. METHODS: Subarachnoid hemorrhage-induced vasospasm was created in 14 cynomolgus macaques via subarachnoid implantation of a 5-ml blood clot. On Day 7 after clot implantation, animals were randomized to either control (saline infusion, 5 monkeys) or treatment groups (intravenous NaNO(2) infusion at 300 µg/kg/hr for 3 hours [7 monkeys] or 8 hours [2 monkeys]). Arteriographic vessel diameter was blindly analyzed to determine the degree of vasospasm before, during, and after treatment. Nitric oxide metabolites (nitrite, nitrate, and S-nitrosothiols) were measured in whole blood and CSF. RESULTS: Moderate-to-severe vasospasm was present in all animals before treatment (control, 36.2% ± 8.8% [mean ± SD]; treatment, 45.5% ± 12.5%; p = 0.9). While saline infusion did not reduce vasospasm, NaNO(2) infusion significantly reduced the degree of vasospasm (26.9% ± 7.6%; p = 0.008). Reversal of the vasospasm lasted more than 2 hours after cessation of the infusion and could be maintained with a prolonged infusion. Nitrite (peak value, 3.7 ± 2.1 µmol/L), nitrate (18.2 ± 5.3 µmol/L), and S-nitrosothiols (33.4 ± 11.4 nmol/L) increased significantly in whole blood, and nitrite increased significantly in CSF. CONCLUSIONS: These findings indicate that the intravenous infusion of NaNO(2) can reverse SAH-induced vasospasm in primates. Further, these findings indicate that a similar treatment paradigm could be useful in reversing cerebral vasospasm after aneurysmal SAH.