The Cannabinoid 2 Receptor (CB2R) Alleviates Inflammatory and Oxidative Stress in Lipopolysaccharide-Induced BV-2 Cells and Regulates M1/M2 Polarization

Abstract

Background: Microglia, which participates in the inflammatory responses in the CNS, can be polarized into M1 and M2 phenotypes, showing many functional properties such as the production of inflammation association molecules. The main aim of this study is to explore whether CB2R is involved in the transformation of BV-2 cells from M1 to M2 to reduce inflammation and oxidative stress, thus promoting the repair of damaged nerves. Material and Methods: The viability of BV-2 cells was detected by CCK-8 assay. For the analysis of the phenotypic properties of BV-2 cells, we further detected the expression of M1 markers (CD32, iNOS), M2 marker (Arg1) and CB2R using western blot or immunofluorescence. After transfection into cells, the overexpressed CB2R was treated with CB2R inhibitor (AM630), then the functional properties of BV-2 cell types regarding cytokine expression profiles were assessed by measuring the production of IL-6, IL-1β, TNF-α, and ROS with ELISA assay. In addition, the neurotrophic factors, including NRF-2, HO-1 and NGF, were detected by western blot. Results: Under M1 conditions, BV-2 cells were overexpressed with CD32 and iNOS, and M1-polarizing conditions induced the production of pro-inflammatory cytokines and ROS. The overexpression of CB2R promotes the transformation from M1 into M2 phenotype in BV-2 cells, following with the upregulation of Arg-1. Meanwhile, the neurotrophic factors were increased in LPS-induced BV-2 cells after CB2R transfection. All these effects were attenuated by AM630. Conclusion: Targeting CB2R might be a new therapeutic option for the treatment of nerve injury and neurological diseases associated with neuroinflammation.