Hypoxia induces actin cytoskeletal changes in neostriatal dendritic spines

E. SARACENO, L. AON, V. BOTI, M. KRUSE, J. C. FERNANDEZ, D. VALVERDE, F. GATO, D. MADUREIRA, L GIRALDEZ ALVAREZ, H. CORINI, F. CAPANI

San Diego, CA

Congreso; Society for Neuroscience 37th Annual Meeting; 2007

Society for Neuroscience

Cerebral hypoxia- ischemia damages synaptic proteins, resulting in protein aggregation and neuronal death. In previous work we have shown neuronal and synaptic changes in rat neostriatum subjected to hypoxia. Since dendritic spines are highly concentrated in F-actin, changes in the F-actin organization could be related with the neuronal changes induced by hypoxia. In this work we studied the effects of hypoxia-ischemia on the actin cytoskeleton of neostriatal post-synaptic densities (PSD) in 60 days olds rats by combining photooxidation, 3D reconstruction and Western blot. In addition we studied the effects of reduced temperature from 37¨¬C to 15¨¬C on dendritic spines. Staining with phalloidin-alexa 488 followed by confocal microscopy analysis showed an increase of F-actin fluorescent staining in the neostriatum of hypoxic animals (Relative fluorescen intensity: control 15.1 ¡¾ 3 vs hypoxic animals 33.5 ¡¾6 p < 001) . Electron microscopy and 3-D reconstruction confirmed these observations showing an increment in the number of F-actin staining spines in neostriatal excitatory synapses subjected to hypoxia (control 2 ¡¾ 0.1 vs hypoxic animals 3,6 ¡¾ 0.2 p < 001). Consistent with the microscopy data, Western blot revealed ¥â-actin increase in hypoxic animals. The optic relative density measurement showed a significant difference between the control (1.43 ¡¾ 0,05) versus the hypoxic animals (2.27 ¡¾ 0.41). When hypoxia was induced under hypothermic conditions the changes observed were prevented. These results suggest that the cellular and subcellular alterations in neostriatal PSDs could be related to F-actin increase probably due to an overexpression of the ¥â-actin gene (ACTB) after a hypoxic episode.