Flavonoids have modulatory effects on neuroinflammation in microglia

Abstract

Microglia are the resident macrophages in the central nervous system. Under normal conditions, microglia cells contribute to brain development and maintenance of tissue homeostasis. However, chronic microglial activation can cause tissue damage and eventually lead to neurodegenerative diseases and neuronal death. In terms of phenotype,activated microglia can be divided into two different types: M1 state and M2 state. The first is classical activation, M1 state, which is typified by the production of inflammatory cytokines and reactive oxygen species (ROS). In contrast with pro-inflammatory M1 cells, alternative activation, M2 state has an anti-inflammatory phenotype promoting wound repair and debris clearance.Recently, the effects of flavonoids on a variety of inflammatory processes and immune functions have been reported. Flavonoids, which are plant pigments, are anti-oxidants that possess anti-inflammatory properties and may modulate signaling pathways. This study aims to investigate the anti-inflammatory effect of flavonoids and their role on the NF-kB pathway in BV2 microglial cells. Flavonoids treatment suppress production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), nitric oxide (NO) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated BV2 cells. Flavonoids treatment also attenuated activation of nuclear factor-kappaB (NF-κB) transcriptional activity. Furthermore,flavonoids suppress mRNA expressions related with pro-inflammatory M1 state. These observations suggest that flavonoids may contribute as an anti-inflammatory agent and provide evidence about its role in the prevention of neurodegenerative diseases associated with inflammation. ⓒ 2015 DGIST