Palmitoylethanolamide counteracts autistic-like behaviours in BTBR T+tf/J mice: Contribution of central and peripheral mechanisms

Abstract

Autism spectrum disorders (ASD) are a group of heterogeneous neurodevelopmental conditions characterized by impaired social interaction, and repetitive stereotyped behaviours. Interestingly, functional and inflammatory gastrointestinal diseases are often reported as a comorbidity in ASDs, indicating gut-brain axis as a novel emerging approach. Recently, a central role for peroxisome-proliferator activated receptor (PPAR)-α has been addressed in neurological functions, associated with the behaviour. Among endogenous lipids, palmitoylethanolamide (PEA), a PPAR-α agonist, has been extensively studied for its anti-inflammatory effects both at central and peripheral level. Based on this background, the aim of this study was to investigate the pharmacological effects of PEA on autistic-like behaviour of BTBR T+tf/J mice and to shed light on the contributing mechanisms. Our results showed that PEA reverted the altered behavioural phenotype of BTBR mice, and this effect was contingent to PPAR-α activation. Moreover, PEA was able to restore hippocampal BDNF signalling pathway, and improve mitochondrial dysfunction, both pathological aspects, known to be consistently associated with ASDs. Furthermore, PEA reduced the overall inflammatory state of BTBR mice, reducing the expression of pro-inflammatory cytokines at hippocampal, serum, and colonic level. The analysis of gut permeability and the expression of colonic tight junctions showed a reduction of leaky gut in PEA-treated BTBR mice. This finding together with PEA effect on gut microbiota composition suggests an involvement of microbiota-gut-brain axis. In conclusion, our results demonstrated a therapeutic potential of PEA in limiting ASD symptoms, through its pleiotropic mechanism of action, supporting neuroprotection, anti-inflammatory effects, and the modulation of gut-brain axis.

Keywords: Autism spectrum disorder (ASD); BDNF signalling pathway; Behaviour; Cytokines; Microbiota-gut brain axis; Neuroinflammation; Peroxisome-proliferator activated receptor (PPAR)-α.