α-linolenic acid mitigates microglia-mediated neuroinflammation of schizophrenia in mice by suppressing the NF-κB/NLRP3 pathway via binding GPR120-R-arrestin 2

Background: Schizophrenia (SCZ) is a heterogeneous psychiatric disorder that is poorly treated by current therapies. Emerging evidence indicates that SCZ is closely correlated with a persistent neuroinflammation. alpha-linolenic acid (ALA) is highly concentrated in the brain and represents a modulator of the immune system by decreasing the inflammatory response in chronic metabolic diseases. This study was first designed to investigate the potential role of dietary ALA on cognitive function and neuroinflammation in mice with SCZ. Methods: In vivo, after 2 weeks of modeling, mice were treated with dietary ALA treatment for 6 weeks. In vitro, inflammation model was created using lipopolysaccharide as an inducer in BV2 microglial cells. Results: Our results demonstrated that ALA alleviated cognitive impairment and enhanced synaptic plasticity in mice with SCZ. Moreover, ALA mitigated systematic and cerebral inflammation through elevating IL-10 and inhibiting IL-1R, IL-6, IL-18 and TNF-alpha. Furthermore, ALA notably inhibited microglia and pro-inflammatory monocytes, as well as microglial activation and polarization. Mechanistically, ALA up-regulated the expressions of G protein coupled receptor (GPR) 120 and associated R-inhibitor protein 2 (R-arrestin2), accompanied by observable weakened levels of transforming growth factor-R activated kinase 1 (TAK1), NF-kappa B p65, cysteine proteinase-1 (caspase-1), pro-caspase-1, associated speck-like protein (ASC) and NLRP3. In vitro, ALA directly restrained the inflammation of microglia by decreasing the levels of pro-inflammatory factors and regulating microglial polarization via GPR120-NF-kappa B/NLRP3 inflammasome signaling pathway, whereas AH7614 definitely eliminated this anti-inflammatory effect of ALA.