CONICET | Buscador de Institutos y Recursos Humanos

Insulin-degrading enzyme (IDE) plays a key role in amyloid beta (Abeta) degradation in vivo. IDE expression and activity are reduced in Alzheimers disease (AD) brains. Moreover, in AD hippocampus, there is a remarkable activation of p-thirty-eight MAPK that correlates with disease severity. Our hypothesis is that in the aged human brain IDE expression may be dampened by hypoxia and p-thirty-eight MAPK activation. To evaluate hypoxia-mediated signaling pathways involved in IDE expression and activity, primary rat astrocytes were subjected to acute hypoxia. Pharmacological inhibitors of p-thirty-eight, ERK and Akt were used. Total RNA and proteins were extracted to perform RT-PCR and Western blotting, respectively. IDE activity was assessed in astrocyte lysates by radiolabel assay using radioactive iodo-insulin as substrate. In hypoxia, IDE protein, mRNA and proteolytic activity were significantly increased (eighty-eight, thirty-eight and seventy-four percent, respectively) in concordance with p-thirty-eight, ERK and Akt activation. Pharmacological inhibition of ERK and Akt resulted in decreased IDE mRNA (sixty-seven percent). Nonetheless, there was not a correlation between both expression levels, because we found only a little protein reduction after Akt inhibition (twenty-nine percent) while no differences were observed when ERK was blocked. In contrast, cells treated with a p-thirty-eight inhibitor exhibited increase in IDE protein (twenty-five percent) and mRNA (thirty-seven percent) compared to control cells. This study demonstrates that IDE expression in astrocytes is activated by Akt and ERK pathways, but is negatively regulated by p-thirty-eight cascade. Understanding the mechanisms involved in Abeta-degrading enzymes downregulation will open up new approaches to AD treatments.