• Toxicological Research
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• 제8권2호
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• pp.343-357
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• 1992

Tumor necrosis factor-${\alpha}$(TNF), a polypeptide hormone secreted primarily by activated macrophages, was originally identified on the basis of its ability to cause hemorrhagic necrosis and tumor regression in vivo. Subsequently, TNF has been shown to be an important component of the host responses to infection and cancer and may mediate the wasting syndrome known as cachexia. These systemic actions of TNF are reflected in its diverse effects on target cells in vitro. TNF initiates its diverse cellular actions by binding to specific cell surface receptors. Although TNF receptors have been identified on most of animal cells, regulation of these receptors and the mechanisms which transduce TNF receptor binding into cellular responses are not well understood. Therefore, in the present study, the mechanisms how TNF receptors are being regulated and how TNF receptor binding is being transduced into cellular responses were investigated in rat liver plasma membranes (PM) and ME-180 human cervical carcinoma cell lines. $^{125}I$-TNF bound to high ($K_d=1.51{\pm}0.35nM$)affinity receptors in rat liver PM. Solubilization of PM with 1% Triton X-100 increased both high affinity (from $0.33{\pm}0.04\;to\;1.67{\pm}0.05$ pmoles/mg protein) and low affinity (from $1.92{\pm}0.16\;to\;7.57{\pm}0.50$ pmoles/mg protein) TNF binding without affecting the affinities for TNF, suggesting the presence of a large latent pool of TNF receptors. Affinity labeling of receptors whether from PM or solubilized PM resulted in cross-linking of $^{125}I$-TNF into $M_r$ 130 kDa, 90 kDa and 66kDa complexes. Thus, the properties of the latent TNF receptors were similar to those initially accessible to TNF. To determine if exposure of latent receptors is regulated by TNF, $^{125}I$-TNF binding to control and TNF-pretreated membranes were assayed. Specific binding was increased by pretreatment with TNF (P<0.05), demonstrating that hepatic PM contains latent TNF receptors whose exposure is promoted by TNF. Homologous up-regulation of TNF receptors may, in part, be responsible for sustained hepatic responsiveness during chronic exposure to TNF. As a next step, the post-receptor events induced by TNF were examined. Although the signal transduction pathways for TNF have not been delineated clearly, the actions of many other hormones are mediated by the reversible phosphorylation of specific enzymes or target proteins. The present study demonstrated that TNF induces phosphorylation of 28 kDa protein (p28). Two dimensional soidum dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) resolved the 28kDa phosphoprotein into two isoforms having pIs of 6.2 and 6.1. The pIs and relative molecular weight of p28 were consistent with those of a previously characterized mRNA cap binding protein. mRNA cap binding proteins are a class of translation initiation factors that recognize the 7-methylguanosine cap structure found on the 5' end of eukaryotic mRNAs. In vitro, these proteins are defined by their specific elution from affinity columns composed of 7-methylguanosine 5'-triphosphate($m^7$GTP)-Sepharose. Affinity purification of mRNA cap binding proteins from control and TNF treated ME-180 cells proved that TNF rapidly stimulates phosphorylation of an mRNA cap binding protein. Phosphorylation occurred in several cell types that are important in vitro models of TNF action. The mRNA cap binding protein phosphorylated in response to TNF treatment was purifice, sequenced, and identified as the proto-oncogene product eukaryotic initiation factor-4E(eIF-4E). These data show that phosphorylation of a key component of the cellular translational machinery is a common early event in the diverse cellular actions of TNF.

• 대한의생명과학회지
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• 제18권3호
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• pp.181-192
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• 2012

Toll-like receptors (TLRs) induce innate immune responses that are essential for host defense against invading microbial pathogens. In general, TLRs have two major downstream signaling pathways; myeloid differential factor 88 (MyD88) and Toll/IL-1R domain-containing adaptor inducing IFN-${\beta}$ (TRIF) leading to the activation of NF-${\kappa}B$ and IRF3. Numerous studies demonstrated that certain phytochemicals possessing anti-inflammatory effects inhibit NF-${\kappa}B$ activation induced by pro-inflammatory stimuli including lipopolysaccharide and tumor necrosis factor-${\alpha}$ ($TNF{\alpha}$). However, the direct molecular targets for such anti-inflammatory phytochemicals are not fully identified. In this paper, we will discuss about the molecular targets of phytochemicals in TLRs signaling pathways. These results present a novel anti-inflammatory mechanism of phytochemicals in TLRs signaling.

• Journal of Microbiology and Biotechnology
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• 제16권4호
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• pp.576-583
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• 2006

The alkali-soluble glucan of the yeast cell wall contains $\beta-(1,3)-$ and (1,6)-D-linkages and is known to systemically enhance the immune system. In the previous study [6], in order to isolate cell wall mutants, a wild-type strain was mutagenized by exposure to ultraviolet light, and the mutants were then selected via treatment with laminarinase $(endo-\beta-(1,3)-D-glucanase)$. The mass of alkali- and water-soluble glucans produced by the mutant was measured to be 33.8 mg/g of the dry mass of the yeast cell. Our results showed that the mutants generated the amount of alkali-soluble glucan 10-fold higher than that generated by the wild-type. Structural analysis showed that the alkali-soluble glucan from the mutants was associated with a higher degree of $\beta-(1,6)-D-linkage$ than was observed in conjunction with the wild-type. Yeast cell wall $\beta-glucan$ was shown to interact with macrophages via receptors, thereby inducing the release of tumor necrosis factor alpha $(TNF-\alpha)$ and nitric oxide. Alkali-soluble $\beta-glucans$, both from water-soluble and water-insoluble glucan, exhibited a higher degree of macrophage activity with regard to both the secretion of tumor necrosis factor alpha $(TNF-\alpha)$ and nitric oxide and direct phagocytosis, than did the positive control ($1{\mu}g$ of lipopolysaccharide).

• The Korean Journal of Physiology and Pharmacology
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• 제19권1호
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• pp.1-7
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• 2015

Our previous study has shown berberine prevents damage to the intestinal mucosal barrier during early phase of sepsis in rat through mechanisms independent of the NOD-like receptors signaling pathway. In this study, we explored the regulatory effects of berberine on Toll-like receptors during the intestinal mucosal damaging process in rats. Male Sprague-Dawlay (SD) rats were treated with berberine for 5 d before undergoing cecal ligation and puncture (CLP) to induce polymicrobial sepsis. The expression of Toll-like receptor 2 (TLR 2), TLR 4, TLR 9, the activity of nuclear factor-kappa B ($NF-{\kappa}B$), the levels of selected cytokines and chemokines, percentage of cell death in intestinal epithelial cells, and mucosal permeability were investigated at 0, 2, 6, 12 and 24 h after CLP. Results showed that the tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and interleukin-6 (IL-6) level were significantly lower in berberine-treated rats compared to the control animals. Conversely, the expression level of tight junction proteins, percentage of cell death in intestinal epithelial cells and the mucosal permeability were significantly higher in berberine-treated rats. The mRNA expression of TLR 2, TLR 4, and TLR 9 were significantly affected by berberine treatment. Our results indicate that pretreatment with berberine attenuates tissue injury and protects the intestinal mucosal barrier in early phase of sepsis and this may possibly have been mediated through the TLRs pathway.

• Clinical and Experimental Pediatrics
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• 제56권4호
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• pp.151-158
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• 2013

Purpose: We investigated the mRNA levels of peroxisome proliferator-activated receptor (PPAR)-${\alpha}$, PPAR-${\gamma}$, adipokines, and cytokines in the lung tissue of lean and obese mice with and without ovalbumin (OVA) challenge, and the effect of rosiglitazone, a PPAR-${\gamma}$ agonist. Methods: We developed 6 mice models: OVA-challenged lean mice with and without rosiglitazone; obese mice with and without rosiglitazone; and OVA-challenged obese mice with and without rosiglitazone. We performed real-time polymerase chain reaction for leptin, leptin receptor, adiponectin, vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-${\alpha}$, transforming growth factor (TGF)-${\beta}$, PPAR-${\alpha}$ and PPAR-${\gamma}$ from the lung tissue and determined the cell counts and cytokine levels in the bronchoalveolar lavage fluid. Results: Mice with OVA challenge showed airway hyperresponsiveness. The lung mRNA levels of PPAR${\alpha}$ and PPAR-${\gamma}$ increased significantly in obese mice with OVA challenge compared to that in other types of mice and decreased after rosiglitazone administeration. Leptin and leptin receptor expression increased in obese mice with and without OVA challenge and decreased following rosiglitazone treatment. Adiponectin mRNA level increased in lean mice with OVA challenge. Lung VEGF, TNF-${\alpha}$, and TGF-${\beta}$ mRNA levels increased in obese mice with and without OVA challenge compared to that in the control mice. However, rosiglitazone reduced only TGF-${\beta}$ expression in obese mice, and even augmented VEGF expression in all types of mice. Rosiglitazone treatment did not reduce airway responsiveness, but increased neutrophils and macrophages in the bronchoalveolar lavage fluid. Conclusion: PPAR-${\alpha}$ and PPAR-${\gamma}$ expressions were upregulated in the lung tissue of OVA-challenged obese mice however, rosiglitazone treatment did not downregulate airway inflammation in these mice.

• Asian Pacific Journal of Cancer Prevention
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• 제17권sup3호
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• pp.293-297
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• 2016

TRAIL, tumor necrosis factor (TNF)-related apoptosis-inducing ligand belongs to one of important cytokine superfamilIES, tumor necrosis factor ($TNF{\alpha}$). TRAIL-2 receptor agonists activate several cell signaling pathways in cells in different manners and could lead to apoptosis or necrosis. Agonistic egg yolk antibodies like IgY which have been developed in a selective manner could activate TRAIL death receptors such as TRAIL-2 (DR5) and thus apoptosis signaling. We here investigated induction of apoptosis in human breast cancer cells (MCF7 cell line) by an IgY produced against an 21 aminoacid epitope of the human TRAIL-2 receptor. As the first step a small peptide of 21 aminoacids choosen from the extracellular domain of DR5 protein was produced with a peptide synthesizer. After control assays and confirmation of the correct amino acid sequence, it was injected to hens immunized to achieve high affinity IgYs. At the next step, the produced IgYs were extracted and examined for specificity against DR5 protein by ELISA assay. Subsequently, the anticancer effect of such IgYs was determined by MTT assay in the MCF7 human breast cancer cell line. The produced peptides successfully immunized hens and the produced antibodies which accumulated in egg yolk specifically recognized the DR5 protein. IgYs exerted significant toxicity and killed MCF7 cells as shown by MTT assay.

• Biomolecules & Therapeutics
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• 제16권4호
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• pp.306-311
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• 2008

Although hepatic microcirculatory dysfunction occurs during endotoxemia, the mechanism responsible for this remains unclear. Since Kupffer cells provide signals that regulate hepatic response in inflammation, this study was designed to investigate the role of Kupffer cells in the imbalance in the expression of vasoactive mediators. Endotoxemia was induced by intraperitoneal E. coli endotoxin (LPS, 1 mg/kg body weight). Kupffer cells were inactivated with gadolinium chloride ($GdCl_3$, 7.5 mg/kg body weight, intravenously) 2 days prior to LPS exposure. Liver samples were taken 6 h following LPS exposure for RT-PCR analysis of mRNA for genes of interest: endothelin (ET-1), its receptors $ET_A$ and $ET_B$, inducible nitric oxide synthase (iNOS), heme oxygenase (HO-1), and tumor necrosis factor-$\alpha$ (TNF-$\alpha$). mRNA levels for iNOS and TNF-$\alpha$ were significantly increased 31.8-fold and 26.7-fold in LPS-treated animals, respectively. This increase was markedly attenuated by $GdCl_3$, HO-1 expression significantly increased in LPS-treated animals, with no significant difference between saline and $GdCl_3$ groups. ET-1 was increased by LPS. mRNA levels for $ET_A$ receptor showed no change, whereas $ET_B$ transcripts increased in LPS-treated animals. The increase in $ET_B$ transcripts was potentiated by $GdCl_3$. We conclude that activation of Kupffer cells plays an important role in the imbalanced hepatic vasoregulatory gene expression induced by endotoxin.

• Molecules and Cells
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• 제26권3호
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• pp.285-290
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• 2008

Estrogen-induced proliferation in estrogen receptor (ER)-positive breast cancer cells is primarily mediated through two distinct intracellular receptors, $ER{\alpha}$ and $ER{\beta}$. Although tumor necrosis factor alpha ($TNF{\alpha}$) and $E2/ER{\alpha}$ are known to exert opposing effects on cell proliferation in MCF-7 cells, the mechanism by which $TNF{\alpha}$ antagonizes $E2/ER{\alpha}$-mediated cell proliferation is not well understood. The present study suggests that reduced cell survival in response to $TNF{\alpha}$ treatment in MCF-7 cells may be associated with the down-regulation of $ER{\alpha}$ protein. The decrease in $ER{\alpha}$ protein level was accompanied by an inhibition of $ER{\alpha}$ gene transcription. Cell viability was decreased synergistically by the combined treatment with $ER{\alpha}$-siRNA and $TNF{\alpha}$. Furthermore, pretreatment of cells with the PI3-kinase (PI3K)/ Akt inhibitor, LY294002, markedly enhanced $TNF{\alpha}$-induced down-regulation of the $ER{\alpha}$ protein, suggesting that the PI3K/Akt pathway might be involved in control of the $ER{\alpha}$ level. Moreover, down-regulation of $ER{\alpha}$ by $TNF{\alpha}$ was not inhibited in cells that were pretreated with the proteasome inhibitors, MG132 and MG152, which suggests that proteasome-dependent proteolysis does not significantly influence $TNF{\alpha}$-induced down-regulation of $ER{\alpha}$ protein. In contrast, the effect of the PI3K/Akt inhibitor on $ER{\alpha}$ was blocked in cells that were treated with LY294002 in the presence of the proteasome inhibitors. Collectively, our findings show that the $TNF{\alpha}$ may partly regulate the growth of MCF-7 breast cancer cells through the down-regulation of $ER{\alpha}$ expression, which is primarily mediated by a PI3K/Akt signaling.

• 대한의생명과학회지
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• 제19권2호
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• pp.118-123
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• 2013

Tumor necrosis factor-alpha (TNF-${\alpha}$) is a proinflammatory cytokine that mediates the inflammatory response and immune functions, and modulates the proliferation, differentiation and cell death of cancer cells. The differential functions of TNF-${\alpha}$ in various human cells due to the formation of different stimulating pathway upon the binding of TNF-${\alpha}$ to its receptors. In the present study, we examined the different effects of TNF-${\alpha}$ on the survival and apoptosis between normal granulocytes and human myeloid leukemia HL-60 cells. Although TNF-${\alpha}$ did not affect on the constitutive apoptosis of granulocytes, TNF-${\alpha}$ strongly induced the apoptosis of HL-60 cells in a dose- and a time-dependent manner. TNF-${\alpha}$-induced apoptosis was occurred via the activation of caspase 8, caspase 9 and caspase 3/7 and the induction of ROS production in HL-60 cells. Also, BAY-11-7085, a NF-${\kappa}B$ inhibitor, blocked the TNF-${\alpha}$-induced apoptosis in HL-60 cells. NF-${\kappa}B$ may be involved in TNF-${\alpha}$-induced apoptotic signaling pathway in HL-60 cells. These results suggest that TNF-${\alpha}$ activates apoptotic pathways and its process depends on cell type and many cellular factors. A better understanding of the differential effect of TNF-${\alpha}$ on cell apoptosis and survival may provide important information that can be used to elucidate the specific inhibitory effect of TNF-${\alpha}$ on the cancer dis.

• 대한의생명과학회지
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• 제16권2호
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• pp.91-95
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• 2010

Meso-dihydroguaiaretic acid (MDGA) is a medicinal herbal product isolated from the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae). It exhibits a neuroprotective effect and also exerts cytotoxicity to certain cancer cells. In the present study, we investigated whether or not MDGA inhibits inflammatory reaction through the inhibition of nitric oxide (NO) generation. The results showed that MDGA (5~$25 {\mu}M$) inhibited 100 ng/ml lipopolysaccharide (LPS)- induced NO generation in macrophage Raw 264.7 cells in a concentration-dependent manner. We also measured the cytotoxic effects of MDGA on Raw 264.7 cells and found no evidence of cytotoxicity. The inhibition of NO generation by MDGA was consistent with the inhibitory effect on the expression of inducible nitric oxide synthase (iNOS). In addition, MDGA inhibited the LPS-induced gene expression of $interleukin-1{\beta}$ $(IL-1{\beta})$ as well as tumor necrosis $factor-{\alpha}$ $(TNF-{\alpha})$. The present results may provide that MDGA has anti-inflammatory properties through inhibition of the toll-like receptors (TLRs) pathway, and suggest that MDGA can be used as an anti-inflammatory agent.