Active forms of Akt and ERK are dominant in the cerebral cortex of newborn pigs that are unaffected by asphyxia

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Abstract

Aims:

Perinatal asphyxia (PA) often results in hypoxic–ischemic encephalopathy (HIE) in term neonates. Introduction of therapeutic hypothermia improved HIE outcome, but further neuroprotective therapies are still warranted. The present study sought to determine the feasibility of the activation of the cytoprotective PI-3-K/Akt and the MAPK/ERK signaling pathways in the subacute phase of HIE development in a translational newborn pig PA/HIE model.

Main methods:

Phosphorylated and total levels of Akt and ERK were determined by Western blotting in brain samples obtained from untreated naive, time control, and PA/HIE animals at 24–48 h survival (n = 3–3–6,respectively). PA (20 min) was induced in anesthetized piglets by ventilation with a hypoxic/hypercapnic (6%O220%CO2) gas mixture. Furthermore, we studied the effect of topically administered specific Akt1/2 and MAPK/ERK kinase inhibitors on Akt and ERK phosphorylation (n = 4–4) in the cerebral cortex under normoxic conditions.

Key findings:

PA resulted in significant neuronal injury shown by neuropathology assessment of haematoxylin/eosin stained sections. However, there were no significant differences among the groups in the high phosphorylation levels of both ERK and Akt in the cerebral cortex, hippocampus and subcortical structures. However, the Akt1/2 and MAPK/ERK kinase inhibitors significantly reduced cerebrocortical Akt and ERK phosphorylation within 30 min.

Significance:

The major finding of the present study is that the PI-3-K/Akt and the MAPK/ERK signaling pathways appear to be constitutively active in the piglet brain, and this activation remains unaltered during HIE development. Thus, neuroprotective strategies aiming to activate these pathways to limit apoptotic neuronal death may offer limited efficacy in this translational model.

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