RESUMEN
Brain injury after intracerebral hemorrhage (ICH) occurs in cortex and white matter and may be mediated by blood breakdown products, including hemoglobin and heme. Effects of blood breakdown products, bilirubin and bilirubin oxidation products, have not been widely investigated in adult brain. Here, we first determined the effect of bilirubin and its oxidation products on the structure and function of white matter in vitro using brain slices. Subsequently, we determined whether these compounds have an effect on the structure and function of white matter in vivo. In all, 0.5 mmol/L bilirubin treatment significantly damaged both the function and the structure of myelinated axons but not the unmyelinated axons in brain slices. Toxicity of bilirubin in vitro was prevented by dimethyl sulfoxide. Bilirubin oxidation products (BOXes) may be responsible for the toxicity of bilirubin. In in vivo experiments, unmyelinated axons were found more susceptible to damage from bilirubin injection. These results suggest that unmyelinated axons may have a major role in white-matter damage in vivo. Since bilirubin and BOXes appear in a delayed manner after ICH, preventing their toxic effects may be worth investigating therapeutically. Dimethyl sulfoxide or its structurally related derivatives may have a potential therapeutic value at antagonizing axonal damage after hemorrhagic stroke.
Asunto(s)
Axones/metabolismo , Bilirrubina/metabolismo , Lesiones Encefálicas/metabolismo , Corteza Cerebral/metabolismo , Hemorragia Cerebral/metabolismo , Accidente Cerebrovascular/metabolismo , Animales , Axones/patología , Lesiones Encefálicas/patología , Corteza Cerebral/patología , Hemorragia Cerebral/patología , Masculino , Ratones , Oxidación-Reducción , Accidente Cerebrovascular/patologíaRESUMEN
Microcirculatory dysfunction may contribute to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). This study investigated structural changes in microvessels and their relationship to brain injury after SAH. We used 15 mice (n = 5 for each group) to create sham, saline-injected (100 µl 0.9% NaCl) or SAH (100 µl autologous blood) model by injection into the prechiasmatic cistern. We sacrificed mice 2 days after surgery and examined the brains using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and immunohistochemical staining of fibrinogen. We assessed neuronal apoptosis by terminal deoxynucleotidyl transferase dUTP (deoxyuridine triphosphate) nick end labeling (TUNEL). Nitric oxide (NO) was measured with 4,5-diaminofluorescein-2-diacetate. TEM and SEM demonstrated that mice with SAH had significantly more of them arterioles with lesion characteristics consistent with microthrombi. Microthrombi number correlated with the number of apoptotic neurons and decreased NO in the brain. In conclusion, SAH causes microthrombosis and constriction of arterioles, which correlates with neuronal death and decreased NO. These data suggest NO depletion may contribute to the formation of microthrombosis and arteriolar constriction, which in turn results in neuronal cell death.
Asunto(s)
Microvasos/patología , Hemorragia Subaracnoidea/complicaciones , Hemorragia Subaracnoidea/patología , Trombosis/etiología , Análisis de Varianza , Animales , Constricción Patológica/fisiopatología , Modelos Animales de Enfermedad , Fibrinógeno/metabolismo , Etiquetado Corte-Fin in Situ , Masculino , Ratones , Microcirculación/fisiología , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Microvasos/metabolismo , Microvasos/ultraestructura , Neuronas/patología , Óxido Nítrico/metabolismo , Hemorragia Subaracnoidea/etiologíaRESUMEN
Animal models have been developed to simulate angiographic vasospasm secondary to subarachnoid hemorrhage (SAH) and to test pharmacologic treatments. Our aim was to evaluate the effect of pharmacologic treatments that have been tested in humans and in preclinical studies to determine if animal models inform results reported in humans. A systematic review and meta-analysis of SAH studies was performed. We investigated predictors of -translation from animals to humans with multivariate logistic regression. Pharmacologic reduction of vasospasm was effective in mice, rats, rabbits, dogs, nonhuman primates, and humans. Animal studies were generally of poor methodologic quality, and there was evidence of publication bias. Fresh blood injection to simulate SAH (vs. clot placement) and evaluation of vasospasm more than 3 days after SAH were independently associated with successful translation. We conclude that reduction of vasospasm is effective in animals and humans, and that injection of fresh blood and evaluation of vasospasm more than 3 days after SAH may be preferable for preclinical models.
Asunto(s)
Modelos Animales de Enfermedad , Hemorragia Subaracnoidea/complicaciones , Vasodilatadores/uso terapéutico , Vasoespasmo Intracraneal/tratamiento farmacológico , Vasoespasmo Intracraneal/etiología , Animales , Angiografía Cerebral , Humanos , PubMed/estadística & datos numéricos , Vasoconstricción/efectos de los fármacos , Vasodilatadores/farmacologíaRESUMEN
Animal models have been developed to simulate angiographic vasospasm secondary to subarachnoid hemorrhage (SAH) and to test pharmacologic treatments. Our aim was to evaluate the effect of pharmacologic treatments that have been tested in humans and in preclinical studies to determine if animal models inform results reported in humans. A systematic review and meta-analysis of SAH studies was performed. We investigated predictors of translation from animals to humans with multivariate logistic regression. Pharmacologic reduction of vasospasm was effective in mice, rats, rabbits, dogs, nonhuman primates (standard mean difference of -1.74; 95% confidence interval -2.04 to -1.44) and humans. Animal studies were generally of poor methodologic quality and there was evidence of publication bias. Subgroup analysis by drug and species showed that statins, tissue plasminogen activator, erythropoietin, endothelin receptor antagonists, calcium channel antagonists, fasudil, and tirilazad were effective whereas magnesium was not. Only evaluation of vasospasm >3 days after SAH was independently associated with successful translation. We conclude that reduction of vasospasm is effective in animals and humans and that evaluation of vasospasm >3 days after SAH may be preferable for preclinical models.
Asunto(s)
Angiografía Cerebral , Hemorragia Subaracnoidea/tratamiento farmacológico , Vasoespasmo Intracraneal/tratamiento farmacológico , Animales , Interpretación Estadística de Datos , Modelos Animales de Enfermedad , Perros , Femenino , Humanos , Macaca , Masculino , Ratones , Sesgo de Publicación , Conejos , Ensayos Clínicos Controlados Aleatorios como Asunto , Ratas , Especificidad de la Especie , Hemorragia Subaracnoidea/complicaciones , Hemorragia Subaracnoidea/patología , Resultado del Tratamiento , Vasoespasmo Intracraneal/etiología , Vasoespasmo Intracraneal/patologíaRESUMEN
One of the major complications after subarachnoid hemorrhage (SAH) is angiographic vasospasm in the large arteries at the base of the brain. However, a clinical trial of clazosentan demonstrated a 65% relative risk reduction in angiographic vasospasm but no effect on mortality or clinical outcome, raising questions about the role of angiographic vasospasm played in outcome after SAH. The purpose of this study was to determine if reducing or reversing angiographic vasospasm with clazosentan reduced other secondary complications such as microthromboembolism, loss of long-term potentiation (LTP) and neuronal cell death in a rat model of SAH. SAH in rats was created by injection of 300 µl non-heparinized autologous blood into the pre-chiasmatic cistern. Clazosentan, 10mg/kg bolus, or vehicle control was administered 1h after SAH intravenously, followed by a continuous infusion (1mg/kg/h) into the jugular vein using an osmotic pump. Rats treated with clazosentan had less large-artery vasospsam compared to vehicle-treated controls. However, clazosentan did not prevent the formation of microthromboemboli, neuronal cell death and degeneration and loss of LTP, suggesting there is a dissociation between large-artery angiographic vasospasm and other secondary complications of SAH. This result suggests that alleviation of angiographic vasospasm alone may not be sufficient to prevent other secondary complications or that off-target drug effects after systemic administration of clazosentan counteract the beneficial effects on angiographic vasospasm.