RESUMO
Nitric oxide (NO) derived from the inducible isoform of NO synthase (iNOS) is an inflammatory product implicated both in secondary damage and in recovery from brain injury. To address the role of iNOS in experimental traumatic brain injury (TBI), we used 2 paradigms in 2 species. In a model of controlled cortical impact (CCI) with secondary hypoxemia, rats were treated with vehicle or with 1 of 2 iNOS inhibitors (aminoguanidine and L-N-iminoethyl-lysine), administered by Alzet pump for 5 days and 1. 5 days after injury, respectively. In a model of CCI, knockout mice lacking the iNOS gene (iNOS(-/-)) were compared with wild-type (iNOS(+/+)) mice. Functional outcome (motor and cognitive) during the first 20 days after injury, and histopathology at 21 days, were assessed in both studies. Treatment of rats with either of the iNOS inhibitors after TBI significantly exacerbated deficits in cognitive performance, as assessed by Morris water maze (MWM) and increased neuron loss in vulnerable regions (CA3 and CA1) of hippocampus. Uninjured iNOS(+/+) and iNOS(-/-) mice performed equally well in both motor and cognitive tasks. However, after TBI, iNOS(-/-) mice showed markedly worse performance in the MWM task than iNOS(+/+) mice. A beneficial role for iNOS in TBI is supported.
Assuntos
Dano Encefálico Crônico/prevenção & controle , Lesões Encefálicas/enzimologia , Proteínas do Tecido Nervoso/fisiologia , Óxido Nítrico Sintase/fisiologia , Óxido Nítrico/fisiologia , Animais , Dano Encefálico Crônico/etiologia , Dano Encefálico Crônico/patologia , Lesões Encefálicas/patologia , Transtornos Cognitivos/etiologia , Indução Enzimática , Inibidores Enzimáticos/farmacologia , Guanidinas/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Hipocampo/fisiopatologia , Hipocampo/efeitos da radiação , Hipóxia/enzimologia , Hipóxia/patologia , Lisina/análogos & derivados , Lisina/farmacologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos da radiação , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/deficiência , Proteínas do Tecido Nervoso/genética , Neurônios/efeitos dos fármacos , Neurônios/enzimologia , Neurônios/efeitos da radiação , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/deficiência , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase Tipo II , Reação em Cadeia da Polimerase , Lesões Experimentais por Radiação/tratamento farmacológico , Ratos , Ratos Sprague-Dawley , Irradiação Corporal Total , Ferimentos não Penetrantes/enzimologia , Ferimentos não Penetrantes/patologiaRESUMO
Platelet (P-) selectin and intercellular adhesion molecule-1 (ICAM-1) mediate accumulation of neutrophils in brain. However, the mechanisms regulating neutrophil accumulation and damage after traumatic brain injury (TBI) are poorly defined. We hypothesized that mice deficient in both P-selectin and ICAM-1 (-/-) would have decreased brain neutrophil accumulation and edema, and improved functional and histopathological outcome after TBI compared with wild-type (+/+). In Protocol I, neutrophils and brain water content were quantified at 24 h after TBI. No difference in brain neutrophil accumulation was observed between groups; however, brain edema was decreased in dual P-selectin and ICAM-1 -/- (P < 0.05 vs. +/+ mice). In Protocol II, after TBI, tests of motor and memory function and histopathology were assessed over 21 days. No difference in motor or memory function or histopathological damage was observed between +/+ and -/- mice. A role for adhesion molecules in the pathogenesis of brain edema independent of leukocyte accumulation in brain is suggested.
Assuntos
Edema Encefálico/prevenção & controle , Lesões Encefálicas/complicações , Molécula 1 de Adesão Intercelular/fisiologia , Selectina-P/fisiologia , Animais , Barreira Hematoencefálica , Edema Encefálico/etiologia , Edema Encefálico/metabolismo , Lesões Encefálicas/metabolismo , Quimiotaxia de Leucócito , Contusões/complicações , Contusões/metabolismo , Molécula 1 de Adesão Intercelular/genética , Masculino , Transtornos da Memória/etiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transtornos dos Movimentos/etiologia , Selectina-P/genética , Peritonite/imunologia , Ferimentos não Penetrantes/complicações , Ferimentos não Penetrantes/metabolismoAssuntos
Boxe/lesões , Lesões Encefálicas/etiologia , Hematoma Epidural Craniano/etiologia , Hematoma Subdural/etiologia , Futebol/lesões , Adolescente , Adulto , Lesões Encefálicas/diagnóstico por imagem , Hematoma Epidural Craniano/diagnóstico por imagem , Hematoma Subdural/diagnóstico por imagem , Humanos , Masculino , Recuperação de Função Fisiológica , Remissão Espontânea , Tomografia Computadorizada por Raios XRESUMO
Recent studies have suggested that under certain conditions, inhalation of stable xenon can cause an increase in CBF or intracranial pressure (ICP). We reviewed the ICP changes that occurred during 48 stable xenon/CT CBF studies in 23 comatose head-injured patients to determine if the concentration (32%) and duration of inhalation (4.5 min) of stable xenon we used caused an increase in ICP. In the group as a whole, there was no significant difference between the mean ICP at the start of xenon inhalation and the mean ICP immediately after completion of the studies. An increase in ICP also was not found in subgroups with low, normal, or high global CBF, or groups with or without intracranial hypertension. Changes in ICP that occurred during individual studies usually were related to corresponding changes in the arterial pCO2 (p less than 0.0001, Pearson's correlation test). Our data suggest that 32% stable xenon administered for 4.5 min does not cause a significant increase in ICP during xenon/CT CBF studies.
Assuntos
Lesões Encefálicas/fisiopatologia , Pressão Intracraniana/efeitos dos fármacos , Xenônio/efeitos adversos , Administração por Inalação , Adolescente , Adulto , Idoso , Pressão Sanguínea , Circulação Cerebrovascular/efeitos dos fármacos , Humanos , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X , Xenônio/administração & dosagem , Xenônio/farmacologiaRESUMO
The effect of posttraumatic hypothermia (brain temperature controlled at 32 degrees C for 4 h) on mortality after severe controlled cortical impact (CCI) was studied in rats. Four posttraumatic brain temperatures were compared: 37 degrees C (n = 10), 36 degrees C (n = 4), 32 degrees C (n = 10), and uncontrolled (UC; n = 6). Rats were anesthetized and subjected to severe CCI (4.0-m/s velocity, 3.0-mm depth) to the exposed left parietal cortex. At 10 min posttrauma the rats were cooled or maintained at their target brain temperature, using external cooling or warming. Brain temperature in the UC group was recorded but not regulated, and rectal temperature was maintained at 37 +/- 0.5 degrees C. After 4 h, rats were rewarmed over a 1-h period to 37 degrees C, extubated, and observed for 24 h. In the 37 and 36 degree C groups, 24-h mortality was 50% (37 degrees C = 5/10, 36 degrees C = 2/4). In the 32 degree C group, 24-h mortality was 10% (1/10). In the UC group, brain temperature was 35.4 +/- 0.6 degrees C during the 4-h treatment period and 24-h mortality was 0% (0/6). Mortality was higher in groups with brain temperatures > or = 36 degrees C versus those with brain temperatures < 36 degrees C (50 vs. 6%, respectively; p < 0.05). Additionally, electroencephalograms (EEG) were recorded in subsets of each temperature group and the percentage of time that the EEG was suppressed (isoelectric) was determined. Percentage of EEG suppression was greater in the hypothermic (32 degrees C, n = 6; UC, n = 4) groups than in the normothermic (36 degrees C, n = 3; 37 degrees C, n = 6) groups (23.3 +/- 14.3 vs. 1.2 +/- 3.1%, respectively; p < 0.05). Posttraumatic hypothermia suppressed EEG during treatment and reduced mortality after severe CCI. The threshold for this protective effect appears to be a brain temperature < 36 degrees C. Thus, even mild hypothermia may be beneficial after severe brain trauma.
Assuntos
Lesões Encefálicas/terapia , Hipotermia Induzida , Lobo Parietal/lesões , Animais , Temperatura Corporal , Lesões Encefálicas/fisiopatologia , Eletroencefalografia , Masculino , Ratos , Ratos Sprague-Dawley , Convulsões/etiologia , Convulsões/fisiopatologiaRESUMO
We measured CBF and CO2 reactivity after traumatic brain injury (TBI) produced by controlled cortical impact (CCI) using magnetic resonance imaging (MRI) and spin-labeled carotid artery water protons as an endogenous tracer. Fourteen Sprague-Dawley rats divided into TBI (CCI; 4.02 +/- 0.14 m/s velocity; 2.5 mm deformation), sham, and control groups were studied 24 hours after TBI or surgery. Perfusion maps were generated during normocarbia (Paco2 30 to 40 mm Hg) and hypocarbia (PaCO2 15 to 25 mm Hg). During normocarbia, CBF was reduced within a cortical region of interest (ROI, injured versus contralateral) after TBI (200 +/- 82 versus 296 +/- 65 mL.100 g-1.min-1, P < 0.05). Within a contusion-enriched ROI, CBF was reduced after TBI (142 +/- 73 versus 280 +/- 64 mL.100 g-1.min-1, P < 0.05). Cerebral blood flow in the sham group was modestly reduced (212 +/- 112 versus 262 +/- 118 mL.100 g-1.min-1, P < 0.05). Also, TBI widened the distribution of CBF in injured and contralateral cortex. Hypocarbia reduced cortical CBF in control (48%), sham (45%), and TBI rats (48%) versus normocarbia, P < 0.05. In the contusion-enriched ROI, only controls showed a significant reduction in CBF, suggesting blunted CO2 reactivity in the sham and TBI group. CO2 reactivity was reduced in the sham (13%) and TBI (30%) groups within the cortical ROI (versus contralateral cortex). These values were increased twofold within the contusion-enriched ROI but were not statistically significant. After TBI, hypocarbia narrowed the CBF distribution in the injured cortex. We conclude that perfusion MRI using arterial spin-labeling is feasible for the serial, noninvasive measurement of CBF and CO2 reactivity in rats.
Assuntos
Lesões Encefálicas/metabolismo , Lesões Encefálicas/fisiopatologia , Dióxido de Carbono/metabolismo , Circulação Cerebrovascular , Animais , Lesões Encefálicas/patologia , Imageamento por Ressonância Magnética , Masculino , Perfusão , Ratos , Ratos Sprague-Dawley , Marcadores de SpinRESUMO
Poly(ADP-ribose) polymerase (PARP), or poly-(ADP-ribose) synthetase, is a nuclear enzyme that consumes NAD when activated by DNA damage. The role of PARP in the pathogenesis of traumatic brain injury (TBI) is unknown. Using a controlled cortical impact (CCI) model of TBI and mice deficient in PARP, the authors studied the effect of PARP on functional and histologic outcome after CCI using two protocols. In protocol 1, naive mice (n = 7 +/+, n = 6 -/-) were evaluated for motor and memory acquisition before CCI. Mice were then subjected to severe CCI and killed at 24 hours for immunohistochemical detection of nitrated tyrosine, an indicator of peroxynitrite formation. Motor and memory performance did not differ between naive PARP +/+ and -/- mice. Both groups showed nitrotyrosine staining in the contusion, suggest ing that peroxynitrite is produced in contused brain. In protoco 2, mice (PARP +/+, n = 8; PARP -/-, n = 10) subjected to CCI were tested for motor and memory function, and contusion volume was determined by image analysis. PARP -/- mice demonstrated improved motor and memory function after CC versus PARP +/+ mice (P < 0.05). However, contusion volume was not different between groups. The results suggest a detri mental effect of PARP on functional outcome after TBI.
Assuntos
Lesões Encefálicas/fisiopatologia , Lesões Encefálicas/psicologia , Encéfalo/fisiopatologia , Cognição/fisiologia , Aprendizagem em Labirinto , Memória/fisiologia , Atividade Motora/fisiologia , Poli(ADP-Ribose) Polimerases/genética , Poli(ADP-Ribose) Polimerases/metabolismo , Animais , Encéfalo/enzimologia , Encéfalo/patologia , Lesões Encefálicas/genética , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/fisiopatologia , Sinais (Psicologia) , Imuno-Histoquímica , Camundongos , Camundongos Knockout , Poli(ADP-Ribose) Polimerases/deficiência , Percepção EspacialRESUMO
We tested the hypothesis that quinolinic acid, a tryptophan-derived N-methyl-D-aspartate agonist produced by macrophages and microglia, would be increased in CSF after severe traumatic brain injury (TBI) in humans, and that this increase would be associated with outcome. We also sought to determine whether therapeutic hypothermia reduced CSF quinolinic acid after injury. Samples of CSF (n = 230) were collected from ventricular catheters in 39 patients (16 to 73 years old) during the first week after TBI, (Glasgow Coma Scale [GCS] < 8). As part of an ongoing study, patients were randomized within 6 hours after injury to either hypothermia (32 degrees C) or normothermia (37 degrees C) treatments for 24 hours. Otherwise, patients received standard neurointensive care. Quinolinic acid was measured by mass spectrometry. Univariate and multivariate analyses were used to compare CSF quinolinic acid concentrations with age, gender, GCS, time after injury, mortality, and treatment (hypothermia versus normothermia). Quinolinic acid concentration in CSF increased maximally to 463 +/- 128 nmol/L (mean +/- SEM) at 72 to 83 hours after TBI. Normal values for quinolinic acid concentration in CSF are less than 50 nmol/L. Quinolinic acid concentration was increased 5- to 50-fold in many patients. There was a powerful association between time after TBI and increased quinolinic acid (P < 0.00001), and quinolinic acid was higher in patients who died than in survivors (P = 0.003). Age, gender, GCS, and treatment (32 degrees C versus 37 degrees C) did not correlate with CSF quinolinic acid. These data reveal a large increase in quinolinic acid concentration in CSF after TBI in humans and raise the possibility that this macrophage-derived excitotoxin may contribute to secondary damage.
Assuntos
Lesões Encefálicas/líquido cefalorraquidiano , Lesões Encefálicas/mortalidade , Ácido Quinolínico/líquido cefalorraquidiano , Adolescente , Adulto , Idoso , Lesões Encefálicas/terapia , Humanos , Hipotermia Induzida , Cinética , Pessoa de Meia-Idade , Prognóstico , Análise de RegressãoRESUMO
Fever above 38 degrees C that occurs in patients with acute neurosurgical diseases appears to worsen secondary brain injury and ultimate neurologic outcomes. Laboratory investigations are quite clear regarding the adverse effects of fever in terms not only of functional outcomes, but also histologic and neurochemical injury. Several preliminary clinical studies also suggest worsened neurologic outcomes in patients who are febrile compared to those who are not. Unfortunately, however, a large prospective study of 428 patients with acute neurosurgical diseases has shown that fever is extraordinarily common during the first seven days after subarachnoid hemorrhage, stroke, and TBI. The ability to eliminate fever in most of these patients during the first five to seven days after their injury would seem desirable. Based on a phase-I trial, it appears that intravascular cooling is a promising new method for avoiding fever in the neurosurgical ICU.
Assuntos
Lesões Encefálicas/terapia , Febre/terapia , Temperatura Corporal , Lesões Encefálicas/fisiopatologia , Febre/etiologia , Humanos , Hipotermia Induzida , Unidades de Terapia IntensivaRESUMO
The selective 5-HT(1A) receptor agonist Repinotan HCl (BAY x3702) has been reported to attenuate cortical damage and improve functional performance in experimental models of cerebral ischemia and acute subdural hematoma. Using a clinically relevant contusion model of traumatic brain injury, we tested the hypothesis that a 4-h continuous infusion of Repinotan HCl (10 microg/kg/h i.v.) commencing 5 min post-injury would ameliorate functional outcome and attenuate histopathology. Forty isoflurane-anesthetized male adult rats were randomly assigned to receive either a controlled cortical impact (2.7 mm tissue deformation, 4 m/s) or sham injury (Injury/Vehicle=10, Injury/MK-801=10, Injury/Repinotan HCl=10, Sham/Vehicle=10), then tested for vestibulomotor function on post-operative days 1-5 and for spatial learning on days 14-18. Neither Repinotan HCl nor the non-competitive N-methyl-D-aspartate receptor antagonist MK-801, which served as a positive control, improved vestibulomotor function on beam balance and beam walk tasks relative to the Injury/Vehicle group, but both did significantly attenuate spatial learning and memory deficits on a water maze task. Repinotan HCl also reduced hippocampal CA(1) and CA(3) neuronal loss, as well as cortical tissue damage, compared to the Injury/Vehicle group at 4 weeks post-trauma. No significant difference in histological outcome was revealed between the Repinotan HCl- and MK-801-treated groups.These findings extend the therapeutic efficacy of Repinotan HCl to a contusion model of experimental brain injury and demonstrate for the first time that 5-HT(1A) receptor agonists confer neuroprotection and attenuate spatial learning deficits following controlled cortical impact injury. This treatment strategy may be beneficial in a clinical context where memory impairments are common following human traumatic brain injury.
Assuntos
Benzopiranos/farmacologia , Lesões Encefálicas/tratamento farmacológico , Degeneração Neural/tratamento farmacológico , Fármacos Neuroprotetores/farmacologia , Receptores de Serotonina/efeitos dos fármacos , Agonistas do Receptor de Serotonina/farmacologia , Tiazóis/farmacologia , Animais , Temperatura Corporal/efeitos dos fármacos , Temperatura Corporal/fisiologia , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Encéfalo/fisiopatologia , Lesões Encefálicas/patologia , Lesões Encefálicas/fisiopatologia , Cognição/efeitos dos fármacos , Cognição/fisiologia , Transtornos Cognitivos/tratamento farmacológico , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/fisiopatologia , Maleato de Dizocilpina/farmacologia , Esquema de Medicação , Antagonistas de Aminoácidos Excitatórios/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Hipocampo/fisiopatologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Degeneração Neural/patologia , Degeneração Neural/fisiopatologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Equilíbrio Postural/efeitos dos fármacos , Equilíbrio Postural/fisiologia , Ratos , Ratos Sprague-Dawley , Receptores de Serotonina/metabolismo , Receptores 5-HT1 de Serotonina , Núcleos Vestibulares/efeitos dos fármacos , Núcleos Vestibulares/patologia , Núcleos Vestibulares/fisiopatologiaRESUMO
Studies of experimental traumatic brain injury have found that histologic injury is significantly reduced and behavioral outcome improved in animals treated with moderate hypothermia (32-33 degrees C) or a 21-aminosteroid. Because these treatments are thought to work through different neurochemical mechanisms, their combined use might be expected to be more efficacious than either treatment alone. To test this hypothesis, we studied each treatment separately and in combination in a rodent model of controlled cortical contusion. Treatment with moderate hypothermia (32 degrees C for 4 h), a 21-aminosteroid (U-74389G, Upjohn, 10 mg/kg intravenously, repeated 3 h after the first dose), or both, was initiated 10, 25, or 40 min after injury. The brains were perfused 24 h after injury, and sagittal sections were stained for the 68-kDa "core" neurofilament subunit, a marker of axonal injury. The total number of positively stained axons in the ipsilateral internal capsule were counted under light microscopy. Compared with the control group (injury but no treatment), treatment with each therapy alone or combined, initiated 10 min after injury, caused significant reductions in the number of stained axons (21-aminosteroid alone-35% reduction; hypothermia alone-55% reduction; combination-48% reduction). The number of positively stained axons was significantly reduced in the aminosteroid and combination therapy groups at all three postinjury times (p = 0.01) and in the hypothermia groups treated at 10 or 25 min (p = 0.01) but not at 40 min after injury. We concluded that combination therapy with hypothermia and 21-aminosteroids was no more efficacious than either therapy alone, and that 21-aminosteroid therapy was more efficacious than hypothermia when treatment was initiated 40 min after injury.
Assuntos
Axônios/ultraestrutura , Lesões Encefálicas/terapia , Hipotermia , Esteroides/farmacologia , Animais , Contagem de Células , Masculino , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
The exogenous administration of cytidine-5'-diphosphate (CDP)-choline has been used extensively as a brain activator in different neurological disorders that are associated with memory deficits. A total of 50 rats were utilized to (a) determine whether exogenously administered CDP-choline could attenuate posttraumatic motor and spatial memory performance deficits and (b) determine whether intraperitoneal (i.p.) administration of CDP-choline increases acetylcholine (ACh) release in the dorsal hippocampus and neocortex. In the behavioral study, traumatic brain injury (TBI) was produced by lateral controlled cortical impact (2-mm deformation/6 m/sec) and administered CDP-choline (100 mg/kg) or saline daily for 18 days beginning 1 day postinjury. At 1 day postinjury, rats treated with CDP-choline 15 min prior to assessment performed significantly better than saline-treated rats. Between 14-18 days postinjury, CDP-choline-treated rats had significantly less cognitive (Morris water maze performance) deficits that injured saline-treated rats. CDP-choline treatment also attenuated the TBI-induced increased sensitivity to the memory-disrupting effects of scopolamine, a muscarinic antagonist. The microdialysis studies demonstrated for the first time that a single i.p. administration of CDP-choline can significantly increase extracellular levels of ACh in dorsal hippocampus and neocortex in normal, awake, freely moving rats. This article provides additional evidence that spatial memory performance deficits are, at least partially, associated with deficits in central cholinergic neurotransmission and that treatments that enhance ACh release in the chronic phase after TBI may attenuate cholinergic-dependent neurobehavioral deficits.
Assuntos
Acetilcolina/metabolismo , Lesões Encefálicas/tratamento farmacológico , Córtex Cerebral/efeitos dos fármacos , Citidina Difosfato Colina/farmacologia , Hipocampo/efeitos dos fármacos , Animais , Córtex Cerebral/metabolismo , Hipocampo/metabolismo , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
Previous work in our laboratory and others using the weight drop (WD) model of traumatic brain injury (TBI) has shown that neutrophils accumulate in brain tissue during the initial 24 h posttrauma as measured by myeloperoxidase (MPO) activity and immunohistochemistry. This study compares the acute inflammatory response to TBI over time, as measured by MPO activity, in the WD and controlled cortical impact (CCI) models. Anesthetized adult Sprague-Dawley rats were traumatized using WD (10-g weight dropped 5 cm) or CCI (4 m/sec, 2.5 mm depth). At 2, 24, 48, or 168 h after trauma, rats (n = 4-5/group at each time) were anesthetized and killed, the brains were removed, and 6-mm coronal slices from traumatized and contralateral hemispheres were assayed for MPO activity. Nontraumatized rats (n = 4) served as controls. Three additional rats underwent a more severe CCI (3 mm depth) with MPO activity assayed at 24 h. A separate group of rats (n = 6) was subjected to WD trauma and killed at 2 weeks after injury for analysis of lesion volume. MPO activity in the traumatized hemisphere was demonstrated at 24 and 48 h in both the WD (0.3152 +/- 0.0472 and 0.3017 +/- 0.0228 U/g, respectively, p < 0.05 vs controls) and CCI (0.1866 +/- 0.0225 and 0.1937 +/- 0.0772 U/g, respectively, p < 0.05 vs controls) models. MPO activity was below the sensitivity of the assay in the control, 2 h, and 168 h groups in both models.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Lesões Encefálicas/patologia , Encéfalo/patologia , Córtex Cerebral/lesões , Neutrófilos/patologia , Análise de Variância , Animais , Encéfalo/enzimologia , Lesões Encefálicas/enzimologia , Imuno-Histoquímica , Masculino , Neutrófilos/enzimologia , Peroxidase/metabolismo , Ratos , Ratos Sprague-Dawley , Redução de PesoRESUMO
Moderate hypothermia has been shown to have therapeutic utility in the treatment of cerebral ischemia and to attenuate the rise in interstitial concentrations of the excitatory amino acid neurotransmitter L-glutamate. In this study, the influence of hypothermia on traumatic brain injury (TBI) was assessed using a controlled cortical impact model. Rats were cooled to 32.0-33.0 degrees C at least 30 min before injury and maintained at this temperature for 2 h after injury. The influence of hypothermia on the immediate increase in interstitial concentrations of aspartate and glutamate and the volume of the resultant lesion 14 days after TBI was then determined. The volume of the lesion (mean +/- SEM) in hypothermic animals (8.2 +/- 1.3 mm3, n = 9) was significantly smaller than that of normothermic animals (13.2 +/- 1.7 mm3, n = 8). By contrast, TBI-induced increases in dialysate concentrations of aspartate and glutamate were similar at the two temperatures. Thus, aspartate content (nmol/10 min) in animals maintained at 37.0-37.5 degrees C (n = 6) and 32.0-33.0 degrees C (n = 6) increased from respective mean preinjury values of 0.05 +/- 0.02 and 0.08 +/- 0.02 to much larger peak values (0.78 +/- 0.13 and 0.71 +/- 0.09, respectively). Similarly, under normothermic conditions glutamate content (nmol/10 min) increased from 0.13 +/- 0.03 to 3.08 +/- 0.52 and from 0.19 +/- 0.06 to a peak value of 3.09 +/- 0.26 under hypothermic conditions. These data clearly demonstrate the cytoprotective action of moderate hypothermia and further suggest that this action is not mediated by attenuation of the rise in interstitial concentrations of aspartate and glutamate.
Assuntos
Ácido Aspártico/metabolismo , Lesões Encefálicas/metabolismo , Lesões Encefálicas/terapia , Glutamatos/metabolismo , Hipotermia Induzida , Aminoácidos/análise , Animais , Encéfalo/patologia , Lesões Encefálicas/patologia , Cromatografia Líquida de Alta Pressão , Ácido Glutâmico , Histocitoquímica , Masculino , Microdiálise , Ratos , Ratos Sprague-Dawley , Espectrometria de FluorescênciaRESUMO
Cyclooxygenase, or prostaglandin G/H synthase, is the rate-limiting step in the production of prostaglandins. A new isoform, cyclooxygenase-2 (COX-2), has been cloned that is induced during inflammation in leukocytes and by synaptic activity in neurons. The objectives of this study are to determine the nature of COX-2 expression in normal and traumatized rat spinal cord, and to determine the effects of selective COX-2 inhibition on functional recovery following spinal cord injury. Using a weight-drop model of spinal cord injury, COX-2 mRNA expression was studied with in situ hybridization. COX-2 protein expression was examined by immunohistochemistry and Western analysis. Finally, using the highly selective COX-2 inhibitor, 1-[(4-methylsufonyl)phenyl]-3-tri-fluro-methyl-5-[(4-flur o)phenyl]prazole (SC58125), the effect of COX-2 inhibition on functional outcome following a spinal cord injury was determined. COX-2 was expressed in the normal adult rat spinal cord. COX-2 mRNA and protein production were increased following injury with increases in COX-2 mRNA production detectable at 2 h following injury. Increased levels of COX-2 protein were detectable for at least 48 h following traumatic spinal cord injury. Selective inhibition of COX-2 activity with SC58125 resulted in improved mean Basso, Beattie, and Bresnahan scores in animals with 12.5- and 25-g/cm spinal cord injuries; however, the effect was significant only for the 12.5g/cm injury group (p=0.0001 vs. p=0.0643 in the 25-g/cm group). These data demonstrate that COX-2 mRNA and protein expression are induced by spinal cord injury, and that selective inhibition of COX-2 improves functional outcome following experimental spinal cord injury.
Assuntos
Isoenzimas/genética , Peroxidases/genética , Prostaglandina-Endoperóxido Sintases/genética , Traumatismos da Medula Espinal/metabolismo , Medula Espinal/enzimologia , Doença Aguda , Animais , Western Blotting , Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase/farmacologia , Modelos Animais de Doenças , Regulação Enzimológica da Expressão Gênica , Imuno-Histoquímica , Hibridização In Situ , Isoenzimas/metabolismo , Masculino , Peroxidases/metabolismo , Prostaglandina-Endoperóxido Sintases/metabolismo , Pirazóis/farmacologia , RNA Mensageiro/análise , Ratos , Ratos Long-Evans , Traumatismos da Medula Espinal/tratamento farmacológico , Resultado do TratamentoRESUMO
DNA damage is a common sequela of traumatic brain injury (TBI). Available techniques for the in situ identification of DNA damage include DNA polymerase I-mediated biotin-dATP nick-translation (PANT), the Klenow fragment of DNA polymerase I-mediated biotin-dATP nick-end labeling (Klenow), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). While TUNEL has been widely utilized to detect primarily double-strand DNA breaks, the use of PANT to detect primarily single-strand DNA breaks and Klenow to detect both single- and double-strand DNA breaks has not been reported after TBI. Accordingly, coronal brain sections from naive rats and rats at 0, 0.5, 1, 2, 6, 24, and 72 h (n = 3-5/group) after controlled cortical impact with imposed secondary insult were processed using the PANT, Klenow, and TUNEL methods. Cells with DNA breaks were detected by PANT in the ipsilateral hemisphere as early as 0.5 h after injury and were maximal at 6 h (cortex = 66.3+/-15.8, dentate gyrus 58.6+/-12.8, CA1 = 15.8+/-5.9, CA3 = 12.8+/-4.2 cells/x 400 field, mean +/- SEM, all p < 0.05 versus naive). Cells with DNA breaks were detected by Klenow as early as 30 min and were maximal at 24 h (cortex = 56.3+/-14.3, dentate gyrus 78.0+/-16.7, CA1 = 25.8+/-4.7, CA3 = 29.3+/-15.1 cells/x 400 field, all p < 0.05 versus naive). Cells with DNA breaks were not detected by TUNEL until 2 h and were maximal at 24 h (cortex = 47.7+/-21.4, dentate gyrus 63.0+/-11.9, CA1 = 5.6+/-5.4, CA3 = 6.9+/-3.7 cells/x 400 field, cortex and dentate gyrus p < 0.05 versus naive). Dual-label immunofluorescence revealed that PANT-positive cells were predominately neurons. These data demonstrate that TBI results in extensive DNA damage, which includes both single- and double-strand breaks in injured cortex and hippocampus. The presence of multiple types of DNA breaks implicate several pathways in the evolution of DNA damage after TBI.
Assuntos
Lesões Encefálicas/genética , Dano ao DNA/genética , DNA Nucleotidilexotransferase/genética , DNA Polimerase I/genética , DNA de Cadeia Simples/genética , Animais , Lesões Encefálicas/patologia , Modelos Animais de Doenças , Marcação In Situ das Extremidades Cortadas , Masculino , Microscopia de Fluorescência , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Hypoxemia has detrimental effects after traumatic brain injury (TBI) in both experimental models and humans. The purpose of this study was to determine the effect of mild or moderate hypoxemia on early histologic and motor functional outcome after controlled cortical impact (CCI) in rats. Anesthetized rats underwent CCI and were randomized to receive mild (FiO2 = 13%, n = 6), moderate (FiO2 = 11%, n = 9), or no (FiO2 = 33%, n = 6) hypoxemia for 30 min after trauma. Sham-operated rats without hypoxemia (n = 7) were used as controls. Motor function (beam balance latency) was assessed on days 0-5. Rats were killed 7 days after injury and their brains removed for assessment of survival of hippocampal neurons and contusion volume. Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end labeling (TUNEL) was performed on brain sections from rats killed at 6, 24, and 72 h after CCI and moderate hypoxemia to assess DNA fragmentation in situ. Mild and moderate hypoxemia augmented motor function deficits after CCI in a dose-dependent manner. Moderate hypoxemia after CCI reduced 7-day survival of CA3 neurons but not CA1 neurons vs. sham (55 [46-86] vs. 99 [95-130], p < 0.05, and 79 [63-86] vs. 101 [81-123], NS, respectively; % uninjured hemisphere, median [range]). The addition of mild or moderate hypoxemia did not increase contusion volume. TUNEL-positive neurons were seen in ipsilateral cortex and dentate gyrus at 6, 24, and 72 h after trauma, and in ipsilateral CA3 hippocampal neurons and thalamus at 24 and 72 h. Moderate hypoxemia augments CA3 neuronal death and early motor functional deficits after CCI. The pattern of DNA fragmentation in selectively vulnerable neurons suggests that apoptosis may play a role in the delayed neuronal death seen after TBI.
Assuntos
Lesões Encefálicas/patologia , Córtex Cerebral/patologia , Hipocampo/patologia , Hipóxia/patologia , Análise de Variância , Animais , Apoptose , Pressão Sanguínea , Lesões Encefálicas/complicações , Lesões Encefálicas/fisiopatologia , Sobrevivência Celular , Córtex Cerebral/lesões , Fragmentação do DNA , Humanos , Hipóxia/complicações , Hipóxia/fisiopatologia , Masculino , Atividade Motora , Neurônios/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Despite considerable investigation in rodent models of traumatic brain injury (TBI), no novel therapy has been successfully translated from bench to bedside. Although well-described limitations of clinical trails may account for these failures, several modeling factors may also contribute to the lack of therapeutic translation from the laboratory to the clinic. Specifically, models of TBI may omit one or more critical, clinically relevant pathophysiologic features. In this invited review article, the impact of the limited incorporation of several important clinical pathophysiologic factors in TBI, namely secondary insults (i.e., hypotension and/or hypoxemia), coma, and aspects of standard neurointensive care monitoring and management strategies (i.e., intracranial pressure [ICP] monitoring and ICP-directed therapies, sedation, mechanical ventilation, and cardiovascular support) are discussed. Comparative studies in rodent and large animal models of TBI (which may, in some cases, represent super models) are also presented. We conclude that therapeutic breakthroughs will likely require a multidisciplinary approach, involving investigation in a range of models, including clinically relevant modifications of established animal models, along with development and application of new innovations in clinical trial design.
Assuntos
Lesões Encefálicas/patologia , Lesões Encefálicas/terapia , Animais , Lesões Encefálicas/complicações , Coma/etiologia , Modelos Animais de Doenças , Humanos , Camundongos , RatosRESUMO
The effect of varying brain temperature on neutrophil accumulation in brain and the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) on cerebrovascular endothelium after controlled cortical impact (CCI) was studied in rats. Sprague Dawley rats were anesthetized and subjected to CCI to the left parietal cortex. Ten minutes after CCI, brain temperature was modulated and maintained at 32 degrees C, 37 degrees C, or 39 degrees C (n = 8 per group) for 4 h. Rats were then decapitated and immunohistochemistry on brain sections was performed using monoclonal antibodies (MoAb) that recognize neutrophils (RP-3), ICAM-1 (TM-8, Athena Neurosciences), or MoAb that react with E-selectin (La-Roche). Each of these markers was quantified in 100 x fields. Neutrophil accumulation was also quantified with myeloperoxidase (MPO) assay. Absolute neutrophil count (ANC) was measured in blood samples before and 1 h and 4 h after CCI. Neutrophil accumulation in injured brain was decreased in rats maintained at 32 degrees C vs 39 degrees C (4-fold difference as assessed by immunohistochemistry, p < 0.05; 8-fold difference as assessed by MPO assay, p < 0.05). Peripheral blood ANC was not affected by temperature. E-selectin was induced on cerebrovascular endothelium after CCI (p < 0.05), but was only decreased modestly at 32 degrees C versus 39 degrees C (p = 0.11). ICAM-1 was not upregulated on cerebrovascular endothelium at this early time following CCI. Neutrophil accumulation is directly dependent on brain temperature during the initial 4 h after CCI. This appears to be mediated by mechanisms other than effects of temperature on E-selectin or ICAM-1 expression or systemic ANC.
Assuntos
Temperatura Corporal/fisiologia , Lesões Encefálicas/fisiopatologia , Encéfalo/fisiopatologia , Encefalite/fisiopatologia , Animais , Encéfalo/patologia , Química Encefálica/fisiologia , Lesões Encefálicas/complicações , Lesões Encefálicas/metabolismo , Encefalite/etiologia , Encefalite/metabolismo , Endotélio Vascular/patologia , Imuno-Histoquímica , Masculino , Neutrófilos/fisiologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Significant morbidity and mortality associated with traumatic brain injury (TBI) are allied with secondary posttrauma inflammatory complications. Hypothermia has been suggested as a possible treatment to lessen or suppress these inflammatory reactions. We report here that interleukin 1 beta, a cytokine responsible for initiating inflammatory cascades, is elevated in rat cortex within 6 h of TBI in the rat. Nerve growth factor (NGF) RNA and protein also increased subsequently, and NGF protein remained elevated for up to 7 days. Four hours of whole body hypothermia (32 degrees C), applied immediately after the TBI, attenuated the posttrauma increase in IL-1 beta RNA and eliminated the increase in NGF RNA and protein observed in cerebral cortex following TBI. Thus, hypothermia may be an effective therapy to diminish the posttrauma inflammatory cascade in the brain (as suggested by the decrease in IL-1 beta). However, the same treatment may hinder the brain's intrinsic repair mechanisms. Optimal treatment may, therefore, require supplemental administration of neurotrophic factors or other agents along with hypothermia.