• BMB Reports
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• v.51 no.8
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• pp.373-377
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• 2018

Triple-negative breast cancer (TNBC) is considered to be a notorious type of cancer due to its aggressive metastatic potential and poor prognosis. Recent evidence suggests that BLT2, a low-affinity $LTB_4$ receptor is critically associated with the phenotypes of TNBC cells, including invasion, metastasis, and survival. Furthermore, in a group of 545 breast cancer patients with metastasis, we observed that the high-BLT2 subgroup had a lower disease-free-survival rate than the low-BLT2 subgroup. Thus, we theorized that anti-BLT2 strategies could facilitate the development of new therapies used for TNBC. This review focuses on recent discoveries regarding BLT2 and its roles in as a novel prognostic biomarker in TNBC.

• Parasites, Hosts and Diseases
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• v.62 no.3
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• pp.281-293
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• 2024

We previously reported that leukotriene B₄ (LTB₄) contained in Trichomonas vaginalis-derived secretory products (TvSP) play an essential role in interleukin-8 (IL-8) production in human mast cell line (HMC-1 cells) via LTB₄ receptor (BLT)-mediated Nuclear Factor-kappa B (NF-κB) activation. Dynamin, a GTPase, has been known to be involved in endocytosis of receptors for signaling of production of cytokine or chemokines. In the present study, we investigated the role of dynamin-mediated BLT1 endocytosis in TvSP-induced IL-8 production. When HMC-1 cells were transfected with BLT1 or BLT2 siRNA, TvSP-induced IL-8 production was significantly inhibited compared with that in cells transfected with control siRNA. In addition, pretreatment of HMC-1 cells with a dynamin inhibitor (Dynasore) reduced IL-8 production induced by TvSP or LTB₄. TvSP- or LTB₄-induced phosphorylation of NF-κB was also attenuated by pretreatment with Dynasore. After exposing HMC-1 cells to TvSP or LTB₄, BLT1 was translocated from the intracellular compartments to the plasma membrane within 30 min. At 60 min after stimulation with TvSP or LTB₄, BLT1 remigrated from the cell surface to intracellular areas. Pretreatment of HMC-1 cells with dynamin-2 siRNA blocked internalization of BLT1 induced by TvSP or LTB₄. Co-immunoprecipitation experiments revealed that dynamin-2 strongly interacted with BLT1 60 min after stimulation with TvSP or LTB₄. These results suggest that T. vaginalis-secreted LTB₄ induces IL-8 production in HMC-1 cells via dynamin 2-mediated endocytosis of BLT1 and phosphorylation of NF-κB.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.241-249
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• 1998

Platelet-activating factor(PAF) enhanced interleukin-1(IL-1) activity by the interaction with a specific receptor in rat alveolar macrophages. In this study, we investigated the role of endogenous arachidonate metabolites and intracellular calcium mobilization in the PAF-induced IL-1 activity. Alveolar macrophages were preincubated with 5-lipoxygenase and cyclooxygenase inhibitors 30 min before the addition of PAF and lipopolysaccharide(LPS). After 24h culture, IL-1 activity was measured in the supernate of sample using the thymocyte proliferation assay. Inhibition of 5-lipoxygenase by nordihydroguaiaretic acid and AA-861 completely blocked the PAF-induced enhancement of IL-1 activity with $IC_{50}\;of\;2\;{\mu}M\;and\;5\;{\mu}M$, respectively. In contrast, the inhibition of cyclooxygenase pathway by indomethacin and ibuprofen resulted in the potentiation in PAF-induced IL-1 activity with maximal effect at $1\;{\mu}M\;and\;5\;{\mu}M$, respectively. In addition, leukotriene $B_4$ and prostaglandin $E_2$ production were observed in PAF-stimulated alveolar macrophage culture. As could be expected, 5-lipoxygenase and cyclooxygenase inhibitors abolished PAF- stimulated leukotriene $B_4$ and prostaglandin $E_2$ production, respectively. The effects of PAF on intracellular calcium mobilization in alveolar macrophages were evaluated using the calcium-sensitive dye fura-2 at the single cell level. PAF at any dose between $10^{-16}\;and\;10^{-8}$ M did not increase intracellular calcium. Furthermore, there was no effective change of intracellular calcium level when PAF was added to alveolar macrophages in the presence of LPS or LPS+LTB4, and 4, 24 and 48h after treatment of these stimulants. Together, the results indicate that IL-1 activity induced by PAF is differently regulated through subsequent induction of endogenous 5-lipoxygenase and cyclooxygenase pathways, but not dependent on calcium signalling pathway.

• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.1005-1009
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• 2007

Leukotriene B4 (LTB4) is a potent chemoattractant for leukocytes and considered to be an inflammatory mediator. Human BLT2 (hBLT2) is a low-affinity G-protein coupled receptor for LTB4 and mediates pertussis toxin-sensitive chemotactic cell movement. Here, we dissected the interaction between hBLT2 and G-protein alpha subunits using GST fusion proteins containing intracellular regions of hBLT2 and various Gα protein including Gα i1, Gα i2, Gα i3, Gα s1, Gα o1, and Gα z. Among the tested Gα subunits, Gα i3 showed the highest binding to the third intracellular loop region of hBLT2 with a dissociation constant (KD) of 5.0 × 10?6 M. These results suggest that Gα i3 has the highest affinity to hBLT2, and the third intracellular loop region of hBLT2 is the major component for the interaction with Gα i3.

• Journal of Microbiology and Biotechnology
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• v.32 no.9
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• pp.1126-1133
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• 2022

This study investigated the contribution of lipoxygenase (LOX) inhibitors, nordihydroguaiaretic acid (NDGA), tetra-O-methyl nordihydroguaiaretic acid (M₄N) and zileuton (ZIL), and thromboxane A2 (TXA₂) inhibitor 4,5-diphenylimidazole (DPI) in the proliferation of Brucella abortus infection. None of the compounds affected the uptake of Brucella into the macrophages. We determined the effect of neutralizing leukotriene B4 (LTB4) receptor and showed that the uptake of the bacteria was inhibited at 30 min post-infection. M₄N treatment attenuated intracellular survival of Brucella at 2 h post-incubation but it was not observed in the succeeding time points. DPI treatment showed reduced survival of Brucella at 24 h post-incubation while blocking LTB4 receptor was observed to have a lower intracellular growth at 48 h post-incubation suggesting different action of the inhibitors in the course of the survival of Brucella within the cells. Reduced proliferation of the bacteria in the spleens of mice was observed in animals treated with ZIL or DPI. Increased serum cytokine level of TNF-α and MCP-1 was observed in mice treated with M₄N or ZIL while a lower IFN-γ level in ZIL-treated mice and a higher IL-12 serum level in DPI-treated mice were observed at 7 d post-infection. At 14 d post-infection, ZIL-treated mice displayed reduced serum level of IL-12 and IL-10. Overall, inhibition of 5-LOX or TXA₂ or a combination therapy promises a potential alternative therapy against B. abortus infection. Furthermore, strong ligands for LTB4 receptor could also be a good candidate for the control of Brucella infection.

• Molecules and Cells
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• v.44 no.12
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• pp.893-899
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• 2021

BLT2 is a low-affinity receptor for leukotriene B₄, a potent lipid mediator of inflammation generated from arachidonic acid via the 5-lipoxygenase pathway. The aim of this study was to investigate whether BLT2 plays any role in sepsis, a systemic inflammatory response syndrome caused by infection. A murine model of cecal ligation and puncture (CLP)-induced sepsis was used to evaluate the role of BLT2 in septic inflammation. In the present study, we observed that the levels of ligands for BLT2 (LTB₄ [leukotriene B₄] and 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid]) were significantly increased in the peritoneal lavage fluid and serum from mice with CLP-induced sepsis. We also observed that the levels of BLT2 as well as 5-lipoxygenase (5-LO) and 12-LO, which are synthesizing enzymes for LTB₄ and 12(S)-HETE, were significantly increased in lung and liver tissues in the CLP mouse model. Blockade of BLT2 markedly suppressed the production of sepsis-associated cytokines (IL-6 [interleukin-6], TNF-α [tumor necrosis factor alpha], and IL-1β [interleukin-β] as well as IL-17 [interleukin-17]) and alleviated lung inflammation in the CLP group. Taken together, our results suggest that BLT2 cascade contributes to lung inflammation in CLP-induced sepsis by mediating the production of inflammatory cytokines. These findings suggest that BLT2 may be a potential therapeutic target for sepsis patients.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.24 no.3
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• pp.134-145
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• 1998

Facial hyperpigmentation in women, which is considered to be a serious cosmetic disability and a cause of mental distress, requires proper management. Melanocyte dendricity is a crucial factor affecting epidermal pigmentation. We found that BQ-788, the endothelin-B (ETB) receptor antagonist, blocks the formation of multi-dendricity which is induced by cocultured keratinocytes. Melanocytes in vivo show numerous dendrites which are in close contact with multiple keratinocytes, forming the epidermal-melanin unit. While melanocytes transfer their melanosomes into the neighboring keratinocytes via dendrites, keratinocytes secrete many growth factors and cytokines that influence viability, morphology, and melanin formation of melanocytes. Endothelin-1 (ET-1), prostaglandin E2(PGE2), and leukotriene-C4 (LT-C4) have been suggested as the candidates for increasing dendricity. Other reports suggested that ET-1 has stimulatory effects on proliferation and melanin formation of melanocytes in vitro. In the present study, using type-specific ET receptor antagonists, we observed how the morphology of melanocytes could be modulated in a coculture system. In addition, the roles of ET-1 for morphology and proliferation on melanocytes were evaluated in different culture media. We suggest that ET-1 increases dendricity and proliferation of melanocytes, and that its dendrite-inducing effect and mitogenic effect are regulated independently.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.4
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• pp.379-389
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• 2018

A nucleobase adenine is a fundamental component of nucleic acids and adenine nucleotides. Various biological roles of adenine have been discovered. It is not produced from degradation of adenine nucleotides in mammals but produced mainly during polyamine synthesis by dividing cells. Anti-inflammatory roles of adenine have been supported in IgE-mediated allergic reactions, immunological functions of lymphocytes and dextran sodium sulfate-induced colitis. However adenine effects on Toll-like receptor 4 (TLR4)-mediated inflammation by lipopolysaccharide (LPS), a cell wall component of Gram negative bacteria, is not examined. Here we investigated anti-inflammatory roles of adenine in LPS-stimulated immune cells, including a macrophage cell line RAW264.7 and bone marrow derived mast cells (BMMCs) and peritoneal cells in mice. In RAW264.7 cells stimulated with LPS, adenine inhibited production of pro-inflammatory cytokines $TNF-{\alpha}$ and IL-6 and inflammatory lipid mediators, prostaglandin $E_2$ and leukotriene $B_4$. Adenine impeded signaling pathways eliciting production of these inflammatory mediators. It suppressed $I{\kappa}B$ phosphorylation, nuclear translocation of nuclear factor ${\kappa}B$ ($NF-{\kappa}B$), phosphorylation of Akt and mitogen activated protein kinases (MAPKs) JNK and ERK. Although adenine raised cellular AMP which could activate AMP-dependent protein kinase (AMPK), the enzyme activity was not enhanced. In BMMCs, adenine inhibited the LPS-induced production of $TNF-{\alpha}$, IL-6 and IL-13 and also hindered phosphorylation of $NF-{\kappa}B$ and Akt. In peritoneal cavity, adenine suppressed the LPS-induced production of $TNF-{\alpha}$ and IL-6 by peritoneal cells in mice. These results show that adenine attenuates the LPS-induced inflammatory reactions.

• BMB Reports
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• v.49 no.4
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• pp.232-237
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• 2016

Mulberry tree twigs (Ramulus mori) contain large amounts of oxyresveratrols and have traditionally been used as herbal medicines because of their anti-inflammatory properties. However, the signaling mechanism by which R. mori exerts its anti-inflammatory action remains to be elucidated. In this study, we observed that R. mori ethanol extracts (RME) exerted an inhibitory effect on the lipopolysaccharide (LPS)-induced production of the pro-inflammatory cytokine interleukin-6 (IL-6) in Raw264.7 macrophage cells. Additionally, RME inhibited IL-6 production by blocking the leukotriene B₄ receptor-2 (BLT2)-dependent-NADPH oxidase 1 (NOX1)-reactive oxygen species (ROS) cascade, leading to anti-inflammatory activity. Finally, RME suppressed the production of the BLT2 ligands LTB4 and 12(S)-HETE by inhibiting the p38 kinase-cytosolic phospholipase A₂-5-/12-lipoxygenase cascade in LPS-stimulated Raw264.7 cells. Overall, our results suggest that RME inhibits the 'BLT2 ligand-BLT2'-linked autocrine inflammatory axis, and that this BLT2-linked cascade is one of the targets of the anti-inflammatory action of R. mori.

• Parasites, Hosts and Diseases
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• v.62 no.3
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• pp.270-280
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• 2024

Trichomoniasis is caused by a sexually transmitted flagellate protozoan parasite Trichomonas vaginalis. T. vaginalis-derived secretory products (TvSP) contain lipid mediators such as leukotriene B₄ (LTB₄) and various cysteinyl leukotrienes (CysLTs) which included LTC₄, LTD₄, and LTE₄. However, the signaling mechanisms by which T. vaginalis-induced CysLTs stimulate interleukin (IL)-8 production in human mast cells remain unclear. In this study, we investigated these mechanisms in human mast cells (HMC-1). Stimulation with TvSP resulted in increased intracellular reactive oxygen species (ROS) generation and NADPH oxidase 2 (NOX2) activation compared to unstimulated cells. Pre-treatment with NOX2 inhibitors such as diphenyleneiodonium chloride (DPI) or apocynin significantly reduced ROS production in TvSP-stimulated HMC-1 cells. Additionally, TvSP stimulation increased NOX2 protein expression and the translocation of p47^phox from the cytosol to the membrane. Pretreatment of HMC-1 cells with PI3K or PKC inhibitors reduced TvSP-induced p47^phox translocation and ROS generation. Furthermore, NOX2 inhibitors or NOX2 siRNA prevented CREB phosphorylation and IL-8 gene expression or protein secretion induced by TvSP. Pretreatment with a CysLTR antagonist significantly inhibited TvSP-induced ROS production, CREB phosphorylation, and IL-8 production. These results indicate that CysLT-mediated activation of NOX2 plays a crucial role in ROS-dependent IL-8 production in human mast cells stimulated by T. vaginalis-secreted CysLTs. These findings enhance our understanding of the inflammatory response in trichomoniasis and may inform the development of targeted therapies to mitigate this response.