Anti-inflammatory effects of blueberry extract in microglial cells

Background: Microglia (MG), the immunocompetent cells of the CNS, respond to brain injury activating and modifying their morphology. Microglia can exist broadly between two different activation states, namely the classical (M1) and the alternative activated (M2) phenotype. The first one is characterized by the production of pro-inflammatory cytokines, in contrast, the latter is characterized by the production of anti-inflammatory cytokines (Kettenmann et al., Neuron. 2013; 77:10–18). Blueberry is involved in the control of the redox state of the cell, cooperating with antioxidant mechanisms, whereas its anti-inflammatory activity is still poorly understood (Businaro et al., Curr. Alzheimer Res. 2018; 15: 363- 380). The aim of the present study is to determine the effect of blueberry extract in resting form or lipopolysaccharide (LPS)-stimulated BV-2 murine MG cells. Methods: The hydroalcoholic extract obtained from fresh blueberries was analyzed by UHPLC/MS. The cellular viability was evaluated by MTT test and Trypan blue assay. Cellular migration was determined by Boyden chamber and Scratch assay. Cytokines mRNA levels were determined by qPCR. Actin cytoskeletal organization and M1/M2 marker expression were analyzed by immunofluorescence. Results: Isomers of the chlorogenic acid, a powerful antioxidant, were detected in the blueberry extract, which, added to the cultures, had no cytotoxic effect, but induced increased cell viability and reduced LPS-driven migration. mRNA expression of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and that of iNOS (M1 marker) was decreased, whereas Arg-1 expression (M2 marker) was increased. Conclusion: Our results suggest that blueberry may promote MG polarization towards the M2 phenotype, and therefore may be used as a nutraceutical in the treatment of neuroinflammatory diseases.