Lonicera japonica THUNB. Extract Inhibits Lipopolysaccharide-Stimulated Inflammatory Responses by Suppressing NF-κB Signaling in BV-2 Microglial Cells

In the current study, we evaluated the anti-inflammatory effects of Lonicera japonica THUNB. (LJ) and its underlying molecular mechanism in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells. Our results indicated that LJ significantly inhibits LPS-stimulated production of nitric oxide (NO) and prostaglandin E₂ (PGE₂). In addition, LJ inhibited inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at both the protein and mRNA levels. In LPS-stimulated BV-2 microglial cells, LJ inhibited proinflammatory cytokines and chemokines, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9) enzymatic activities, and/or mRNA expression, as well as reactive oxygen species (ROS) production. LJ significantly suppressed activation of nuclear factor-κB (NF-κB) and its translocation from the cytosol to the nucleus and suppressed the DNA-binding activity of NF-κB. Furthermore, LJ significantly inhibited phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK 1/2), p38 mitogen-activated protein kinases (MAPKs), phosphatidylinositol 3-kinases (PI3K)/Akt, and Janus kinase 1 (JAK1)/signal transducer and activator of transcription (STAT)1/3. Collectively, our findings indicated that the antineuroinflammatory properties of LJ in LPS-induced BV-2 microglial cells is due to downregulation of proinflammatory cytokines and chemokines downstream of inhibition of NF-κB activation.