Naringenin attenuates the release of pro-inflammatory mediators from lipopolysaccharide-stimulated BV2 microglia by inactivating nuclear factor-κB and inhibiting mitogen-activated protein kinases.

Naringenin, one of the most abundant flavonoids in citrus fruits and grapefruits, has been reported to exhibit anti-inflammatory and antitumor activities. However, the cellular and molecular mechanisms underlying the naringenin anti-inflammatory activity are poorly understood. In this study, we conducted an investigation of the inhibitory effects of naringenin on the production of lipopolysaccharide (LPS)-induced pro-inflammatory mediators in BV2 microglial cells. We found that pre-treatment with naringenin prior to treatment with LPS significantly inhibited excessive production of nitric oxide (NO) and prostaglandin E2 (PGE2) in a dose-dependent manner. The inhibition was associated with downregulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. Naringenin also attenuated the production of pro-inflammatory cytokines and chemokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) by suppressing expression of mRNAs for these proteins. In addition, the molecular mechanism underlying naringenin-mediated attenuation in BV2 cells has a close relationship to suppressing translocation of the nuclear factor-κB (NF-κB) p65 subunit into the nucleus and the phosphorylation of Akt and mitogen-activated protein kinases (MAPKs). These findings suggest that naringenin may provide neuroprotection through suppression of pro-inflammatory pathways in activated BV2 microglial cells.