Blockade of the Interaction of Calcineurin with FOXO in Astrocytes Protects Against Amyloid-beta-Induced Neuronal Death

Abstract

Astrocytes actively participate in neuro-inflammatory processes associated to Alzheimer's disease (AD), and other brain pathologies. We recently showed that an astrocyte-specific intracellular signaling pathway involving an interaction of the phosphatase calcineurin with the transcription factor FOXO3 is a major driver in AD-associated pathological inflammation, suggesting a potential new druggable target for this devastating disease. We have now developed decoy molecules to interfere with calcineurin/FOXO3 interactions, and tested them in astrocytes and neuronal co-cultures exposed to amyloid-beta (A beta) toxicity. We observed that interference of calcineurin/FOXO3 interactions exerts a protective action against A beta-induced neuronal death and favors the production of a set of growth factors that we hypothesize form part of a cytoprotective pathway to resolve inflammation. Furthermore, interference of the A beta-induced interaction of calcineurin with FOXO3 by decoy compounds significantly decreased amyloid-beta protein precursor (A beta PP) synthesis, reduced the A beta PP amyloidogenic pathway, resulting in lower A beta levels, and blocked the expression of pro-inflammatory cytokines TNF alpha and IL-6 in astrocytes. Collectively, these data indicate that interrupting pro-inflammatory calcineurin/FOXO3 interactions in astrocytes triggered by A beta accumulation in brain may constitute an effective new therapeutic approach in AD. Future studies with intranasal delivery, or brain barrier permeable decoy compounds, are warranted.