Quercetin, a bioflavonoid produced from vegetables and fruits, exerts anti-inflammatory effects in various diseases

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Quercetin, a bioflavonoid produced from vegetables and fruits, exerts anti-inflammatory effects in various diseases. (MCP-1). It also attenuated the adherence of the human being monocytic leukemia cell collection THP-1 to IL-1-stimulated ARPE-19 cells. We also shown that quercetin inhibited signaling pathways related to the inflammatory process, including phosphorylation of mitogen-activated protein kinases (MAPKs), inhibitor of nuclear element -B kinase (IKK)/, c-Jun, cAMP response element-binding protein (CREB), activating transcription element 2 (ATF2) and nuclear element (NF)-B p65, and HOE 32021 clogged the translocation of NF-B p65 into the nucleus. Furthermore, MAPK inhibitors including an extracellular signal-regulated kinase (ERK) 1/2 inhibitor (U0126), a p38 inhibitor (SB202190) and a c-Jun N-terminal kinase (JNK) inhibitor (SP600125) decreased the manifestation of soluble ICAM-1 (sICAM-1), but not ICAM-1. U0126 and SB202190 could inhibit the manifestation of IL-6, IL-8 and MCP-1, but SP600125 could not. An NF-B inhibitor (Bay 11-7082) also reduced the expression of ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1. Taken together, these results provide evidence that quercetin protects ARPE-19 cells from the IL-1-stimulated increase in ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1 production by blocking the activation of MAPK and NF-B signaling pathways to ameliorate the inflammatory response. HOE 32021 0.05 compared with the basal level. 2.2. Quercetin Inhibits the Expression of ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1 in IL-1-Stimulated ARPE-19 Cells Numerous studies have reported the quercetin can inhibit the expression of IL-6, IL-8, ICAM-1 or MCP-1 induced by various stimuli such as LPS, TNF-, high glucose and calcium ionophore A23187 in human mast cells, mesangial cells, neutrophils, airway epithelial cells and rat intestinal microvascular endothelial cells, respectively [32,33,34,35,36]. In these experiments, the efficacy and modes of action of quercetin appear to be affected by a diversity of cell types and inflammatory stimulants. Therefore, we evaluated whether quercetin has anti-inflammatory properties in IL-1-stimulated ARPE-19 cells. We first assessed the cytotoxicity of quercetin in ARPE-19 cells by an MTT assay. As shown in Figure 2A, the viability of ARPE-19 cells was significantly reduced at quercetin concentrations higher than 30 M. Accordingly, quercetin concentrations from 2.5 to 20 M were chosen for all subsequent experiments (ELISA, Western blotting, and Reverse Transcription-Quantitative Polymerase Chain Reaction (RT-qPCR) tests). Before being stimulated with 1 ng/mL IL-1 for 24 h, ARPE-19 cells were pretreated with different concentrations of quercetin (2.5, 5, 10 or 20 M) for 1 h. As the quercetin concentration increased, the ICAM-1 level gradually decreased and the release of sICAM-1 into the culture medium was inhibited (Figure 2B,C). Twenty micromolar quercetin also significantly inhibited the expression of IL-6, IL-8 and MCP-1 (Figure 2DCF). To investigate whether quercetin affects the mRNA expression of ICAM-1, IL-6, IL-8 and MCP-1 in IL-1-stimulated ARPE-19 cells, cells were pretreated with 20 M quercetin for 1 HOE 32021 h and then incubated with IL-1 (1 ng/mL) for 4 h. Quercetin clearly reduced the IL-1-induced expression of mRNA for ICAM-1, IL-6, IL-8 and MCP-1 (Figure 3ACD). Open in a separate window Figure 2 Quercetin attenuates the expression of ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1 in IL-1-stimulated ARPE-19 cells. (A) Effects of quercetin on ARPE-19 cell viability. ARPE-19 cells were treated for 24 h with 2.5C40 M quercetin and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to analyze the cell viability. (B) ICAM-1 protein level was evaluated by Western blotting and then quantified using Image Lab software. (C) The degrees of sICAM-1, (D) IL-6, (E) IL-8 and (F) MCP-1 HOE 32021 had been evaluated by ELISA after cells had been incubated for 1 h with quercetin in the indicated dosages and then triggered with 1 ng/mL IL-1 for 24 h. The info are indicated as mean SD of three 3rd party tests. # 0.05 versus control cells. * 0.05 versus IL-1-activated cells. Open up in another window Shape 3 Quercetin attenuates the manifestation of ICAM-1, IL-6, IL-8 and MCP-1 mRNA in IL-1-activated ARPE-19 cells. ARPE-19 cells had been pretreated with 20 M quercetin for 1 h before excitement with 1 ng/mL IL-1 for 4 h. Change Transcription-Quantitative Rabbit Polyclonal to CDK8 Polymerase String Response (RT-qPCR) was utilized to look for the collapse adjustments in (A) ICAM-1, (B) IL-6, (C) IL-8 and (D) MCP-1 gene manifestation with -actin as an interior control. The info are indicated as mean SD of three 3rd party tests. # 0.05 versus control cells. * 0.05 versus IL-1-activated cells. 2.3. Quercetin Suppresses Inflammatory Signaling Pathways in ARPE-19 Cells Many reports have.