URB597 Administration decreases neuroinflammation and promotes autophagy in Alzheimer's disease models

In recent years, much attention has been focused on the endocannabinoid system as a therapeutic target for neurodegenerative diseases, including Alzheimer's disease (AD). The first endocannabinoid to be characterized was anandamide (N -arachidonoyl ethanolamine, AEA), which is hydrolyzed in postsynaptic neurons by the fatty acid amide hydrolase (FAAH). Notably, the post-mortem examination of brains from AD patients has revealed several alterations of the endocannabinoid system reporting a decrease in cortical AEA levels and a parallel increase in FAAH activity. On this ground, by using both cellular and a transgenic mouse model of AD, we aimed at determining whether pharmacological inhibition of FAAH via URB597 administration may affect microglia polarization and provide beneficial effects in restoring autophagic process and reducing amyloid-β (Aβ) aggregates, which are all neuropathological features of AD. The evaluation of morphological and major markers of microglial activation (iNOS and ARG-1) showed the ability of URB597 to revert microglial activation towards an anti-inflammatory condition, which was associated with the decrease of pro-inflammatory cytokines and an increase of anti-inflammatory cytokines together with the restoration of key factors involved in autophagic processes. These data were confirmed in vivo in the Tg2576 mice where the broad-spectrum action of endocannabinoids ranging from the anti-inflammatory action to the restoration of autophagic flux was demonstrated by the increase of proteins such as ATG7, Beclin1, LC3 and activation of ULK1 signaling following mTOR decrease after URB597 treatment. Moreover, treatment with URB597 decreases the expression of BACE1 through the modulation of CB2 receptors, leading to the reduction of amyloid plaques. Taken together, these data suggest that inhibition of FAAH can drive the polarization of microglia towards an anti-inflammatory phenotype and demonstrate that the modulation of the endocannabinoid system in AD, via URB597 administration, could be a potential and effective therapy not only to fight neuroinflammation but also to regulate the autophagic machinery.