The caffeine-binding adenosine A 2A receptor induces age-like HPA-axis dysfunction by targeting glucocorticoid receptor function

Abstract

Caffeine is associated with procognitive effects in humans by counteracting overactivation of the adenosine A 2A receptor (A 2A R), which is upregulated in the human forebrain of aged and Alzheimer's disease (AD) patients. We have previously shown that an anti-A 2A R therapy reverts age-like memory deficits, by reestablishment of the hypothalamic-pituitary-adrenal (HPA) axis feedback and corticosterone circadian levels. These observations suggest that A 2A R over-activation and glucocorticoid dysfunction are key events in age-related hippocampal deficits; but their direct connection has never been explored. We now show that inducing A 2A R overexpression in an aging-like profile is sufficient to trigger HPA-axis dysfunction, namely loss of plasmatic corticosterone circadian oscillation, and promotes reduction of GR hippocampal levels. The synaptic plasticity and memory deficits triggered by GR in the hippocampus are amplified by A 2A R over-activation and were rescued by anti-A 2A R therapy; finally, we demonstrate that A 2A R act on GR nuclear translocation and GR-dependent transcriptional regulation. We provide the first demonstration that A 2A R is a major regulator of GR function and that this functional interconnection may be a trigger to age-related memory deficits. This supports the idea that the procognitive effects of A 2A R antagonists, namely caffeine, on Alzheimer's and age-related cognitive impairments may rely on its ability to modulate GR actions.