Cannabidiol releases CB₁R from A_2AR repression in ischemic stroke

Cannabidiol (CBD) is a phytocannabinoid with potential in one of the most prevalent syndromes occurring at birth, the hypoxia of the neonate. CBD targets a variety of proteins, adenosine A_2AR and cannabinoid CB₁R receptors included. These two receptors may interact to form heteromers (A_2AR-CB₁R Hets) that are also a target of CBD. Thus, we aimed to assess whether the expression and function of A_2AR-CB₁R-Hets is affected by CBD in animal models of hypoxia of the neonate and in glucose- and oxygen deprived (GOD) neurons and microglial cells. Results indicated that the formation of A_2AR-CB₁R heteromers increased A_2AR affinity for its selective agonist CGS21680. Moreover, resonance energy transfer assays showed that CBD and cannabigerol (CBG) affected the structure of the heteromer. Regarding functionallity, CBD partially bloked A_2AR induced signalling in transfected HEK-293 T cells, while it recovered CB₁R signalling in glucose/oxygen-deprived neurons and microglial cells. The expression of A_2AR-CB₁R Hets increased in GOD neurons and microglial cells. This increase was counteracted with a pre-treatment with CBD and CBG. Importantly, in brain sections of a hypoxia/ischemia animal model, administration of CBD led to a significant reduction in the expression of A_2AR-CB₁R Hets. In conclusion, CBD effects in the hypoxia of the neonate can be mediated by A_2AR-CB₁R complex. CBD partially blocks A_2AR signalling while potentiates the neuroprotective effect of CB₁R in hypoxic-ischemic conditions.