Isotrifoliol inhibits pro-inflammatory mediators by suppression of TLR/NF-κB and TLR/MAPK signaling in LPS-induced RAW264.7 cells

• Published in: International immunopharmacology 2017-04, Vol.45, p.110-119
• Main Authors: Li, Hua, Yoon, Jeong-Hyun, Won, Hyo-Jun, Ji, Hyeon-Seon, Yuk, Heong Joo, Park, Ki Hun, Park, Ho-Yong, Jeong, Tae-Sook
• Format: Article
• Language: English
• Subjects: Animals; Anti-inflammation; Anti-inflammatory agents; Anti-Inflammatory Agents - isolation & purification; Anti-Inflammatory Agents - pharmacology; Carbon tetrachloride; CCL3 protein; CCL4 protein; Chemokines; Coumestans; Cyclooxygenase-2; Cytokines - metabolism; Daidzein; Degradation; Diet; Extracellular signal-regulated kinase; Flavonoids; Flavonoids - isolation & purification; Flavonoids - pharmacology; Gene expression; Genistein; Glycine; Glycine max - immunology; Glycosides; Immune system; Immunology; Inflammation; Inflammation - drug therapy; Inflammation Mediators - metabolism; Interleukin 6; Isoflavones; Isotrifoliol; Leaves; Lipopolysaccharides; Lipopolysaccharides - immunology; Macrophages; Macrophages - drug effects; Macrophages - immunology; MAP kinase; MAPK; Mice; NF-kappa B - metabolism; NF-κB; Nitric oxide; Nitric-oxide synthase; p38 Mitogen-Activated Protein Kinases - metabolism; Phosphorylation; Plant Leaves; Prostaglandin E2; Protein kinase; Proteins; RAW 264.7 Cells; Reactive oxygen species; Signal transduction; Signal Transduction - drug effects; Soybeans; Toll-like receptors; Toll-Like Receptors - metabolism
• ISSN: 1567-5769; 1878-1705
• DOI: 10.1016/j.intimp.2017.01.033

Soybeans, produced by Glycine max (L.) Merr., contain high levels of isoflavones, such as genistein and daidzein. However, soy leaves contain more diverse and abundant flavonol glycosides and coumestans, as compared to the soybean. This study investigated the anti-inflammatory effects of the major coumestans present in soy leaf (coumestrol, isotrifoliol, and phaseol) in lipopolysaccharide (LPS)-induced RAW264.7 cells. Coumestans significantly reduced LPS-induced nitric oxide (NO), prostaglandin E2 (PGE2), and reactive oxygen species (ROS) production; isotrifoliol had the most potent anti-inflammatory activity. Isotrifoliol reduced LPS-mediated induction of mRNA expression of inducible nitric-oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin (IL)-1β, IL-6, tumor necrosis factor alpha (TNFα), and chemokines, such as chemokine (C-C motif) ligand (CCL) 2, CCL3, and CCL4. Isotrifoliol prevented NF-κB p65 subunit activation by reducing the phosphorylation and degradation of the inhibitor of NF-κB. And isotrifoliol significantly suppressed phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). Furthermore, isotrifoliol suppressed LPS-induced Toll-like Receptor (TLR) signaling pathway, including mRNA expression of TNF receptor associated factor 6, transforming growth factor beta-activated kinase 1 (TAK1), TAK1 binding protein 2 (TAB2), and TAB3. These results demonstrate that isotrifoliol exerts an anti-inflammatory effect by suppressing the expression of inflammatory mediators via inhibition of TLR/NF-κB and TLR/MAPK signaling in LPS-induced RAW264.7 macrophages. Therefore, isotrifoliol can be used as an anti-inflammatory agent, and coumestan-rich soy leaf extracts may provide a useful dietary supplement. [Display omitted] •This is the first study that describes the anti-inflammatory effect of isotrifoliol isolated from soy leaf extracts.•Isotrifoliol more strongly inhibits inflammatory response compared to coumestrol and phaseol in LPS-induced macrophages.•Isotrifoliol inhibits LPS-induced NF-κB and MAPK activation by inhibiting TLR signaling in macrophages.