NEUROTROPHINS AND NEUROPROTECTION IN A PRENATAL HYPOXIC MODEL

FISZER DE PLAZAS, S.; BOGETTI, MARÍA EUGENIA

Washington

Congreso; Society for Neuroscience; 2011

Society for Neuroscience

Hypoxia is an injury that consists in a decreased concentration of O2 in blood and tissues, which leads to cell death. During embryonic development, hypoxia causes irreversible damage in the CNS. Previous work in our model of acute hypoxia (60 min, 8% of O2) in chicken embryos has shown that in the optic tectum (OT), hypoxic cell death (HxCD) presents an apoptotic phenotype. The HxCD is delayed after the end of the hypoxia treatment, and it is not massive, i.e. only a small group of neurons die as consequence of hypoxia. In the OT there are mainly two great waves of NOCD (naturally occurring cell death) that differ in time, the later of which is known for being dependent on neurotrophins (NTF). We hypothesized that a NTF-regulated pathway, involved in neuronal survival/death during development, could be altered by the hypoxic insult. One of the objectives of the present work was to analyze the influence of NTF on NOCD and on HxCD in developing chick OT both in vivo and in vitro. For this purpose we aimed to determine the OT ontogenetic period in which neurotrophic death cells occurs. We have discovered that, in the OT, the second wave of NOCD occurs between embryonic day (ED) 14 and ED16. For our experiments, we designated ED15 as a representative day of this period. We demonstrated both in vivo and in vitro that cells in the OT at ED15 are vulnerable to acute hypoxia, showing a decrease in the number of living cells. Secondly, by means of the neutralization technique, we studied the effect of endogenous NGF (Nerve Growth Factor) when applying different amounts of anti-NGF antibody on primary cultures of OT neurons at ED 15, showing that neuronal cells seem to require self produced NGF for their survival. It is known that the NTF protect neurons against a wide varied of insults. We have determined that the NGF administration on neuron cultures of OT in ED15 (0.5ng/ml) 30 minutes before the hypoxia, reduces the HxCD, reaching values near the control ones. In conclusion, hypoxic cell death during the second wave of NOCD is sensible to the influence of endogenous NTF, and it is prevented when NGF is administrated before the injury.