Interruption of the establishment of neuronal circuits by perinatal asphyxia induced long-term dendritic spine alterations

SARACENO, GUSTAVO EZEQUIEL; BROCCO, MARCELA ADRIANA; GALEANO, PABLO; ROMERO, JUAN IGNACIO; HOLUBIEC, MARIANA INÉS; LOGICA TORNATORE, TAMARA; CASTILLA LOZANO, MARÍA DEL ROCIO; KÖLLIKER FRERS, RODOLFO ALBERTO; CAPANI, FRANCISCO

Buenos Aires

Congreso; 5th Special Conference of the International Society for Neurochemistry (ISN); 2012

International Society for Neurochemistry (ISN)

Hypoxic ischemic damage in immature vulnerable regions of the brain has serious effects on brain maturation, particularly when it occurs during prenatal/neonatal stages and coincides with critical processes of cellular or tissue differentiation. In these cases, perinatal asphyxia (PA) is an important risk factor for a variety of neurodevelopmental disorders since it affects the establishment of neural circuit patterns. The lack of knowledge of the underlying mechanisms of this dysfunction, prompted us to investigate the morphological changes in the neuronal cytoskeleton induced by PA in a murine model. No significant morphological alterations were observed in microtubule associated protein 2 (MAP2) positive dendrites or in the phosphorylation status of medium and heavy neurofilaments (NF H/Mp) in Stratum radiatum of CA1 hippocampal area after 30 days of the Hypoxic ischemic event. Regarding the consequences of PA in dendritic spines, we studied the dendritic protrusions by different techniques. An increase in mushroom type protrusion was observed using the photooxidation technique, electron microscopy and 3D reconstruction in PA animals. Real time PCR assays revealed an over expression of beta actin mRNA, while Western blot analysis showed higher beta actin protein levels in synaptosome fractions of asphyctic animals. Moreover, these alterations were accompanied by an increase in the expression of M6a, a protein involved in spinogenesis. In contrast, 120 days after PA we observed morphological changes in MAP2 positive dendrites, as well as in the NF H/Mp, a decrease in mushroom type dendritic spines and Western blot analysis of beta actin showed no significant differences. After 4 months of PA, E-PTA technique showed an increase of postsynaptic densities (PSDs) thickness. These results suggest that interruption of brain development by PA induced long term synaptic disarrangement, possibly produced by early changes in actin organization, the misfolding or aggregation of proteins in dendritic spines or the morphological alterations in neurites. We hypothesize that early alterations in neural circuits of rat hippocampus, especially defects in dendritic spine morphology, might be related with neurodevelopmental disorders since they have been observed in the brains of patients with these pathologies.