Eriodictyol docked into the ATP-binding active site of JNK. immune responses for neutralizing invaders and repairing damaged cells, and finally it initiates healing processes(1). Inflammation is usually caused by the binding of a pathogen to toll-like receptor (TLR) 4 and CD14 receptors, which activates cellular signaling(2). Since nitric oxide (NO) is one of the inflammatory mediators, inflammation is usually characterized by the secretion of NO, and modulation of NO is considered a possible treatment for inflammatory disease(3). The increase in inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 causes cell damage following the increased production of NO and prostaglandins (PGs)(4). Suppressing the induction MKT 077 of COX-2 is usually a new strategy in the prevention of inflammation and COX-2 expression is also related to the activities of many intracellular signaling proteins, such as extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), and Jun-N terminal kinase (JNK)(5). Many research studies support the beneficial association between health and the intake of fruits and vegetables, and polyphenols in fruits and vegetables are known to induce functional benefits(6). Among polyphenols, flavonoids are naturally occurring compounds that are ubiquitous in plants and vegetables. Flavonoids have been recognized to exhibit biological effects in various diseases, including effects that are anti-hepatotoxic, anti-atherogenic, anti-allergic, and anti-cancerous, in addition to their anti-inflammatory activity(7). Flavonoids are known to interact with the ATP-binding sites of tyrosine kinase and serine kinase, resulting in the inhibition of these proteins(8). Many lines of evidence suggest a direct role for flavonoids in modulating the inflammatory responsein vitroor in cellular models. Quercetin, apigenin, luteolin, naringenin, and kaempferol suppress MKT 077 NO production in lipopolysaccharide (LPS)- or cytokine-stimulated macrophages, whereas catechin and a few flavanones were not active in reducing NO production in LPS-stimulated macrophages(9). In our previous study, we reported anti-inflammatory activities of amentoflavone found inGinko bilobaandHypericum perforatumand systematically decided the signal transduction pathways(10). Eriodictyol is an interesting flavonoid because it is usually distributed in common foods and shows beneficial biological activities. Several fruits and vegetables express eriodictyol, especially lemons(11,12). We have shown that eriodictyol is usually a potent antimicrobial inhibitor ofStaphylococcus aureus-ketoacyl acyl carrier protein synthase III (KAS III), MKT 077 with strong MKT 077 binding affinities of 2.01 105M-1as well as high antimicrobial activities againstS. aureusand 4 Methicillin-resistantStaphylococcus aureus(MRSA) strains(13). In addition, eriodictyol was selected as one of theEnterococcus faecalisKAS III inhibitors using docking studies, and it displays antimicrobial activity againstE. faecalisand vancomycin-resistantE. faecalis(VREF)(14). Eriodictyol was found to suppress NO production, nuclear factor (NF)-B activation, and MAPK phosphorylation Rabbit Polyclonal to SIRPB1 in mouse macrophages(15). In this study, we further investigated the anti-inflammatory activities of eriodictyol and its mechanism in mouse macrophages. Herein, we report that eriodictyol exhibits anti-inflammatory activity to inhibit production of LPS-stimulated pro-inflammatory cytokines and systematically present our understanding of the mechanisms by which it activated TLR4/CD14 following p38 MAPK, ERK1/2, JNK, and COX-2 regulation. We determined interactions between JNK and eriodictyol using fluorescence quenching analysis and saturation-transfer difference (STD)-NMR spectroscopy. We also propose a model of JNK binding with eriodictyol using the results of our docking study. == RESULTS == == Cytotoxicity in RAW264.7, NIH3T3, and HaCaT cells == In order to determine the nontoxic concentration of eriodictyol in RAW264.7, NIH3T3, and HaCaT cells, we investigated cytotoxicity by MTT assay, as shown inFig. 1. An eriodictyol concentration of up to 25 M did not affect cell viability; even at an eriodictyol concentration of up to 100 M, the survival rate was greater than 70% in mouse macrophage cells. The survival rates of NIH3T3 cells were 87.4%, 76.6%, and 48.4% at 25, 50, and 100 M eriodictyol, respectively. Interestingly, 100 M of eriodictyol did not affect cell survival at all for HaCaT cells. == Fig. 1. Dose-response curves of eriodictyol for cytotoxicity toward macrophage-derived RAW264.7 (), NIH3T3 (), and HaCaT () cells. == == Quantification of nitrite production in LPS-stimulated RAW264.7 cells == We.