RESUMEN
We have previously demonstrated aggregation of amyloid precursor protein (APP) and beta-amyloid (Abeta) to dense plaque-like deposits in the thalamus of rats subjected to transient middle cerebral artery occlusion (MCAO). Here, we investigated the underlying molecular effects of MCAO on APP processing and expression profiles of Abeta degrading enzymes in the cortex adjacent to the infarct (penumbra) and ipsilateral thalamus 2, 7 and 30 days after ischemic insult. Enhanced beta-amyloidogenic processing of APP and altered insulin degrading enzyme and neprilysin expression were observed in the thalamus, but not the penumbral cortex, 7 and 30 days after MCAO coinciding with increased calcium levels and beta-secretase (BACE) activity. Consecutively, increased BACE activity associated with depletion of BACE trafficking protein GGA3, suggesting a post-translational stabilization of BACE. These results demonstrate that focal cerebral ischemia leads to complex pathogenic events in the thalamus long after the initial insult.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Regulación de la Expresión Génica/fisiología , Infarto de la Arteria Cerebral Media/patología , Tálamo/metabolismo , Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Animales , Ácido Aspártico Endopeptidasas/metabolismo , Infarto Encefálico/etiología , Infarto Encefálico/patología , Calcio/metabolismo , Caspasa 3/metabolismo , Modelos Animales de Enfermedad , Lateralidad Funcional , Infarto de la Arteria Cerebral Media/complicaciones , Insulisina/genética , Insulisina/metabolismo , Masculino , Neprilisina/genética , Neprilisina/metabolismo , Estructura Terciaria de Proteína , Ratas , Ratas Wistar , Factores de TiempoRESUMEN
BACKGROUND AND PURPOSE: The present study examined the long-term presence of beta-amyloid precursor protein (APP) and beta-amyloid (Abeta) accumulation in the rat thalamus after focal cerebral ischemia. METHODS: Male Wistar rats were subjected to transient middle cerebral artery occlusion (MCAO) for 2 hours. Sensorimotor outcome was assessed using a tapered/ledged beam-walking task after operation. The distribution of APP and Abeta was examined immunohistochemically at 1 week, 1 month, and 9 months after MCAO. RESULTS: MCAO caused a long-lasting deficit in forelimb and hind limb function assessed using the beam-walking test. Histologic examination revealed a transient increase in APP and Abeta staining in axons in the corpus callosum and in neurons at the border of the ischemic region. APP and Abeta deposits persisted in the thalamic nuclei (ventroposterior lateral and ventroposterior medial nuclei), eventually leading to dense plaque-like deposits by the end of the 9-month follow-up. The deposits were surrounded by an astroglial scar. The deposits were positive for Abeta and N-terminal APP, but not for C-terminal APP. Antibodies against the C-terminal of Abeta, ie, Abeta42 and Abeta40, showed a preferential staining for Abeta42. Congo red or thioflavine S did not stain the deposits. CONCLUSIONS: The present results demonstrated the persistent presence and aggregation of APP and Abeta, or their fragments, to dense plaque-like deposits in the ventroposterior lateral and ventroposterior medial nuclei of rats subjected to focal cerebral ischemia.