• Korean Journal of Food Science and Technology
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• v.50 no.4
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• pp.437-443
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• 2018

Activation of macrophages plays an important role in the host-immune system. In this study, we investigated the functional roles and related signaling mechanism of hot-water extracts of bee pollen (BPW) in RAW 264.7 macrophages. Since BPW did not exert cytotoxicity at concentrations ranging from 62.5 to $250{\mu}g/mL$ in macrophage cells, a concentration of $250{\mu}g/mL$ was used as the maximum dose of BPW throughout subsequent experiments. BPW increased inducible nitric oxide synthase-mediated nitric oxide production in a concentration-dependent manner. Additionally, BPW was found to induce macrophage activation by augmenting the expression of cell surface molecules (cluster of differentiation; CD80/86, and major histocompatibility complex; MHC class I/II) and production of pro-inflammatory cytokines (tumor necrosis $factor-{\alpha}$, interleukin-6, and $IL-1{\beta}$) through mitogen-activated protein kinase and nuclear $factor-{\kappa}B$ signaling pathways in RAW 264.7 macrophages. Taken together, our results indicate that BPW could potentially be used as an immunomodulatory agent.

• Biomedical Science Letters
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• v.18 no.2
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• pp.104-111
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• 2012

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases which degrade extracellular matrix (ECM) during embryogenesis, wound healing, and tissue remodeling. Dysregulation of MMP activity is also associated with various pathological inflammatory conditions. In this study, we examined the expression pattern of MMPs during PMA-induced differentiation of THP-1 monocytic cells into macrophages. We found that MMP1, MMP8, MMP3, MMP10, MMP12, MMP19, MMP9, and MMP7 were upregulated during differentiation whereas MMP2 remained unchanged. Expression of MMPs increased in a time-dependent manner; MMP1, MMP8, MMP3, MMP10, and MMP12 increased beginning at 60 hr post PMA treatment whereas MMP19, MMP9, and MMP7 increased beginning at 24 hr post PMA treatment. To identify signal transduction pathways involved in PMA-induced upregulation of MMPs, we treated PMA-differentiated THP-1 cells with specific inhibitors for PKC, MEK1, NF-${\kappa}B$, PI3K, p38 MAPK and PLC. We found that inhibition of the MEK1 pathway blocked PMA-induced upregulation of all MMPs to varying degrees except for MMP-2. In addition, expression of select MMPs was inhibited by PI3K, p38 MAPK and PLC inhibitors. In conclusion, we show that of the MMPs examined, most MMPs were up-regulated during differentiation of monocyte into macrophage via the MEK1 pathway. These results provide basic information for studying MMPs expression during macrophage differentiation.

• IMMUNE NETWORK
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• v.10 no.6
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• pp.219-229
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• 2010

Background: N-myc downstream regulated gene 2 (NDRG2) is a member of the NDRG gene family. Our previous report indicated a possible role for NDRG2 in regulating the cytokine, interleukin-10 (IL-10), which is an important immunosuppressive cytokine. Several pathways, including p38-MAPK, NF-${\kappa}B$, and JAK/STAT, are used for IL-10 production, and the JAK/STAT pathway can be inhibited in a negative feedback loop by the inducible protein, SOCS3. In the present study, we investigated the effect of NDRG2 gene expression on IL-10 signaling pathway that is modulated via SOCS3 and STAT3. Methods: We generated NDRG2-overexpressing U937 cell line (U937-NDRG2) and treated the cells with PMA to investigate the role of NDRG2 in IL-10 production. U937 cells were also transfected with SOCS3- or NDRG2-specific siRNAs to examine whether the knockdown of SOCS3 or NDRG2 influenced IL-10 expression. Lastly, STAT3 and SOCS3 induction was measured to identify the signaling pathway that was associated with IL-10 production. Results: RT-PCR and ELISA assays showed that IL-10 was increased in U937-mock cells upon stimulation with PMA, but IL-10 was inhibited by overexpression NDRG2. After PMA treatment, STAT3 phosphorylation was decreased in a time-dependent manner in U937-mock cells, whereas it was maintained in U937-NDRG2 cells. SOCS3 was markedly reduced in U937-NDRG2 cells compared with U937-mock cells. IL-10 production after PMA stimulation was reduced in U937 cells when SOCS3 was inhibited, but this effect was less severe when NDRG2 was inhibited. Conclusion: NDRG2 expression modulates SOCS3 and STAT3 activity, eventually leading to the inhibition of IL-10 production.