RESUMEN
OBJECTIVE: Systemic PaO2 oscillations occur during cyclic recruitment and derecruitment of atelectasis in acute respiratory failure and might harm brain tissue integrity. DESIGN: Controlled animal study. SETTING: University research laboratory. SUBJECTS: Adult anesthetized pigs. INTERVENTIONS: Pigs were randomized to a control group (anesthesia and extracorporeal circulation for 20 hr with constant PaO2, n = 10) or an oscillation group (anesthesia and extracorporeal circulation for 20 hr with artificial PaO2 oscillations [3 cycles min⻹], n = 10). Five additional animals served as native group (n = 5). MEASUREMENTS AND MAIN RESULTS: Outcome following exposure to artificial PaO2 oscillations compared with constant PaO2 levels was measured using 1) immunohistochemistry, 2) real-time polymerase chain reaction for inflammatory markers, 3) receptor autoradiography, and 4) transcriptome analysis in the hippocampus. Our study shows that PaO2 oscillations are transmitted to brain tissue as detected by novel ultrarapid oxygen sensing technology. PaO2 oscillations cause significant decrease in NISSL-stained neurons (p < 0.05) and induce inflammation (p < 0.05) in the hippocampus and a shift of the balance of hippocampal neurotransmitter receptor densities toward inhibition (p < 0.05). A pathway analysis suggests that cerebral immune and acute-phase response may play a role in mediating PaO2 oscillation-induced brain injury. CONCLUSIONS: Artificial PaO2 oscillations cause mild brain injury mediated by inflammatory pathways. Although artificial PaO2 oscillations and endogenous PaO2 oscillations in lung-diseased patients have different origins, it is likely that they share the same noxious effect on the brain. Therefore, PaO2 oscillations might represent a newly detected pathway potentially contributing to the crosstalk between acute lung and remote brain injury.
Asunto(s)
Lesiones Encefálicas/etiología , Lesiones Encefálicas/fisiopatología , Respiración Artificial/efectos adversos , Respiración Artificial/métodos , Síndrome de Dificultad Respiratoria/terapia , Animales , Análisis de los Gases de la Sangre , Oxigenación por Membrana Extracorpórea/métodos , Mediadores de Inflamación/metabolismo , Atelectasia Pulmonar/prevención & control , ARN Complementario/metabolismo , Distribución Aleatoria , Reacción en Cadena en Tiempo Real de la Polimerasa , Porcinos , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/metabolismo , Ácido gamma-Aminobutírico/metabolismoRESUMEN
BACKGROUND: Experimental stroke studies use multiple techniques to evaluate histopathological damage. Unfortunately, sensitivity and reproducibility of these techniques are poorly characterized despite pivotal influence on results. METHOD: The present study compared several quantification methods to differentiate between two severities of global cerebral ischemia and reperfusion. Male Sprague-Dawley rats were randomized to moderate (10min) or severe (14min) ischemia by bilateral carotid occlusion (BCAO) with hemorrhagic hypotension. Neuronal cell count was determined in hippocampus at bregma -3.14mm and -3.8mm on day 3 and 28 post insult by counting neurons in the whole CA1 or in one to three defined regions of interest (ROI) placed in NeuN and Fluoro-Jade B stained sections. RESULTS: In healthy rats hippocampal neurons were arranged uniformly, while distribution became inhomogeneous after ischemia. The number of NeuN and Fluoro-Jade B positive cells was dependent on localization. Differences between ischemia severities became more prominent at 28 days compared to 3 days. Fluoro-Jade B positive cell count increased at 28 days, staining rather injured not dying neurons. COMPARISON WITH EXISTING METHODS: Placement of counting windows has a major influence on extent of differences between degree of neuronal injury and variations within groups. CONCLUSIONS: The investigated quantification methods result in inconsistent information on the degree of damage. To obtain consistent and reliable results observation period should be extended beyond 3 days. Due to inhomogeneous distribution of viable neurons in CA1 after ischemia neuronal counting should not be performed in a single ROI window, but should be performed in multiple ROIs or the whole CA1 band.
Asunto(s)
Isquemia Encefálica/patología , Región CA1 Hipocampal/patología , Histocitoquímica/métodos , Animales , Antígenos Nucleares/metabolismo , Benzoxazinas , Recuento de Células , Colorantes , Modelos Animales de Enfermedad , Fluoresceínas , Colorantes Fluorescentes , Hemorragias Intracraneales/patología , Hipotensión Intracraneal/patología , Masculino , Proteínas del Tejido Nervioso/metabolismo , Neuronas/patología , Distribución Aleatoria , Ratas Sprague-Dawley , Reproducibilidad de los Resultados , Índice de Severidad de la Enfermedad , Factores de TiempoRESUMEN
PURPOSE: Recent studies demonstrated anticoagulatory, antiinflammatory, antiapoptotic, and neuroprotective properties of activated protein C (APC) in rodent models of acute neurodegenerative diseases, suggesting APC as promising broad acting therapeutic agent. Unfortunately, continuous infusion of recombinant human APC (rhAPC) failed to improve brain damage following cardiac arrest in rats. The present study was designed to investigate the neuroprotective effect after global cerebral ischemia (GI) with an optimized infusion protocol. METHODS: Rats were subjected to bilateral clip occlusion of the common carotid arteries (BCAO) and controlled hemorrhagic hypotension to 40 mm Hg for 14 min and a subsequent 5h-infusion of rhAPC (2mg/kg bolus+6 mg/kg/h continuous IV) or vehicle (0.9% NaCl). The dosage was calculated to maintain plasma hAPC activity at 150%. Cerebral inflammation, apoptosis and neuronal survival was determined at day 10. RESULTS: rhAPC infusion did not influence cortical cerebral perfusion during reperfusion and failed to reduce neuronal cell loss, microglia activation, and caspase 3 activity. CONCLUSION: Even an optimized rhAPC infusion protocol designed to maintain a high level of APC plasma activity failed to improve the sequels following GI. Despite positive reports about protective effects of APC following, e.g., ischemic stroke, the present study supports the notion that infusion of APC during the early reperfusion phase does not result in sustained neuroprotection and fails to improve outcome after global cerebral ischemia.