Effects of prenatal hypoxia on expression of amyloid precursor protein and metallopeptidases in the rat brain

In the present study we have investigated the effect of prenatal hypoxia on expression of amyloid precursor protein (APP) and some metallopeptidases, which regulate β-amyloid peptide (Aβ) levels (neprilysin (NEP) and endothelin-converting enzyme (ECE-1)) in the cortex of rats during different periods of postnatal development. We have found that the level of APP in the sensorimotor cortex (SMC) of rats, analysed by Western blotting, increases from days 1 to 5 of postnatal development and then steadily decreases with age, with the most dramatic decline in the period from day 180 to 600. In the cortex of rats subjected to prenatal hypoxia on day 13.5 of embryogenesis, the postnatal levels of APP were higher than in the control. Secretion of the soluble form of APP (sAPP) by α-secretase was found to be the most active on day 30 of postnatal development and there was a significant decrease in the production of sAPP after prenatal hypoxia. NEP was found to be expressed in the cortex of rats only at the early stages of postnatal development and it was barely detectable in adult rats. The decline of NEP levels during ageing might contribute to accumulation of Aβ in later life in humans. Prenatal hypoxia resulted in a significant decrease of NEP expression on day 10, but its level was recovered when animals were preconditioned to mild hypoxia. A similar phenomenon was observed when the expression of ECE-1 was analysed. Overall, prenatal hypoxia leads to significant changes in the levels of APP and expression of metallopeptidases involved in amyloid metabolism during all postnatal life and preconditioning to hypoxia appeared to be neuroprotective.