Jin-Ku Lee

Interleukin-6 induces S100A9 expression in colonic epithelial cells through STAT3 activation in experimental ulcerative colitis.

Background Intestinal epithelium is essential for maintaining normal intestinal homeostasis; its breakdown leads to chronic inflammatory pathologies, such as inflammatory bowel diseases (IBDs). Although high concentrations of S100A9 protein and interleukin-6 (IL-6) are found in patients with IBD, the expression mechanism of S100A9 in colonic epithelial cells (CECs) remains elusive. We investigated the role of IL-6 in S100A9 expression in CECs using a colitis model. Methods IL-6 and S100A9 expression, signal transducer and activator of transcription 3 (STAT3) phosphorylation, and infiltration of immune cells were analyzed in mice with dextran sulfate sodium (DSS)-induced colitis. The effects of soluble gp130-Fc protein (sgp130Fc) and S100A9 small interfering (si) RNA (si-S100A9) on DSS-induced colitis were evaluated. The molecular mechanism of S100A9 expression was investigated in an IL-6-treated Caco-2 cell line using chromatin immunoprecipitation assays. Results IL-6 concentrations increased significantly in the colon tissues of DSS-treated mice. sgp130Fc or si-S100A9 administration to DSS-treated mice reduced granulocyte infiltration in CECs and induced the down-regulation of S100A9 and colitis disease activity. Treatment with STAT3 inhibitors upon IL-6 stimulation in the Caco-2 cell line demonstrated that IL-6 mediated S100A9 expression through STAT3 activation. Moreover, we found that phospho-STAT3 binds directly to the S100A9 promoter. S100A9 may recruit immune cells into inflamed colon tissues. Conclusions Elevated S100A9 expression in CECs mediated by an IL-6/STAT3 signaling cascade may play an important role in the development of colitis.

STAT3-RANTES Autocrine Signaling Is Essential for Tamoxifen Resistance in Human Breast Cancer Cells

The acquisition of tamoxifen resistance is a major therapeutic problem in breast cancer. We developed a tamoxifen-resistant MCF-7 (TRM-7) cell line to elucidate the molecular mechanisms and factors associated with acquisition of such resistance. We showed that phosphorylation of STAT3 at tyrosine 705 (Y705) and RANTES expression are increased in response to tamoxifen in human breast cancer cells. On the basis of these results, we hypothesize that upregulated STAT3 phosphorylation and RANTES may be correlated with the development of drug resistance. Here, we showed that STAT3 and RANTES contribute to the maintenance of drug resistance. STAT3 phosphorylation is constitutively retained via a RANTES autocrine loop, which in turn upregulates anti-apoptotic signals in TRM-7 cells. STAT3–RANTES autocrine signaling affected expression of anti-apoptotic BCL-2 family genes and prevented TRM-7 cells from undergoing programmed cell death by inhibiting PARP and caspase-9 cleavage. Subsequently, blockade of STAT3 and RANTES in TRM-7 cells resulted in reduction of anti-apoptotic signals, which was rescued by exogenous RANTES treatment; drug resistance was also restored. Taken together, our results suggested that STAT3–RANTES autocrine signaling is essential for maintenance of drug resistance and inhibition of programmed cell death. These mechanisms of STAT3–RANTES autocrine signaling suggest a novel strategy for management of patients with tamoxifen-resistant tumors. Mol Cancer Res; 11(1); 31–42. ©2012 AACR.

Relative antioxidant activities of quercetin and its structurally related substances and their effects on NF-κB/CRE/AP-1 signaling in murine macrophages

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced by the oxidative burst in activated macrophages and neutrophils cause oxidative stressimplicated diseases. Quercetin is flavonoid that occurs naturally in plants and is widely used as a nutritional supplement due to its antioxidant and anti-inflammatory properties. In this study, we investigated antioxidant activities and mechanisms of action in zymosan-induced macrophages of quercetin and quercetin-related flavonoids such as quercitrin, isoquercitrin, quercetin 3-O-β-(2″-galloyl)-rhamnopyranoside (QGR) and quercetin 3-O-β-(2″-galloyl)-glucopyranoside (QGG) as well as gallic acid, a building moiety of QGR and QGG. QGR and QGG exhibited stronger antioxidant activities compared with quercetin, whereas quercitrin, isoquercitrin and gallic acid exhibited weak-tono antioxidant activities, assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, superoxide production, superoxide scavenging, nitric oxide (NO) production, peroxynitrite (ONOO−) scavenging and myeloperoxidase (MPO) activity. Regarding mechanisms, the quercetincontaining flavonoids QGR and QGG differentially targeted compared with quercetin in the NF-κB signaling pathway that inhibited the DNA binding activity of the NF-κB complex without affecting the degradation and phosphorylation of IκBα and NF-κB phosphorylation. In addition, QGR and QGG inhibited CRE and activator protein (AP-1) transcriptional activity and JNK phosphorylation by inhibiting the cAMP/protein kinase A (PKA) and protein kinase C (PKC) signaling in a different manner than quercetin. Our results showed that although QGR and QGG exhibited stronger antioxidant activities than querce-tin in macrophages, their mechanisms of action in terms of the NF-κB, PKA and PKC signaling pathways were different.

Anti-adipogenic activity of compounds isolated from Idesia polycarpa on 3T3-L1 cells

Recently, obesity is a complex multifactorial chronic disease increasing the risk for type 2 diabetes, coronary heart disease and hypertension, and has become a major worldwide health problem. In the course of screening natural products employing 3T3-L1 cells as an in vitro system, the methanol extract of Idesia polycarpa Maxim. Fruits (Flacourtiaceae) significantly inhibited adipocyte differentiation by measuring lipid contents using oil red O staining. One new compound, 6-(oxymethyl)-2-hydroxyphenyl-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (8), was isolated along with nine known compounds (1-7 and 9-10) from CHCl3 and n-BuOH fractions of the methanol extract of I. polycarpa fruits. Among them, idescarpin (1) with 1-hydroxy-6-oxo-2-cyclohexenecarboxylate moiety showed the most potent inhibitory activity on adipocyte differentiation with IC50 values of 23.2 μM. Idescarpin (1) dramatically suppressed the induction of C/EBPα expression, whereas it significantly increased the induction of PPARγ expression, supported by quantitative real time PCR and Western blot analysis. The down-regulation in mRNA levels of SREBP1c, SCD-1, and FAS by idescarpin (1) during adipocyte differentiation revealed that the inhibition of adipocyte differentiation was mediated by the regulation of lipogenesis. Taken together, we suggest that idescarpin (1) shows a great potential against obesity and diabetes though the anti-adipogenic activity and the up-regulation of PPARγ.

Signal transducer and activator of transcription 3 (Stat3) contributes to T‐cell homeostasis by regulating pro‐survival Bcl‐2 family genes

The naive T‐cell pool in peripheral lymphoid tissues is fairly stable in terms of number, diversity and functional capabilities in spite of the absence of prominent stimuli. This stability is attributed to continuous tuning of the composition of the T‐cell pool by various homeostatic signals. Despite extensive research into the link between signal transducer and activator of transcription 3 (Stat3) and T‐cell survival, little is known about how Stat3 regulates homeostasis by maintaining the required naive T‐cell population in peripheral lymphoid organs. We assessed whether the elimination of Stat3 in T cells limits T‐cell survival. We demonstrated that the proportion and number of single‐positive thymocytes as well as T cells in the spleen and lymph nodes were significantly decreased in the Stat3‐deficient group as a result of the enhanced susceptibility of Stat3‐deleted T lymphocytes to apoptosis. Importantly, expression of the anti‐apoptotic Bcl‐2 and Bcl‐xL was markedly decreased in Stat3‐deleted single‐positive thymocytes and T lymphocytes, suggesting that Stat3 helps to maintain the T‐cell pool in the resting condition by promoting the expression of Bcl‐2 family genes. These findings suggest the importance of Stat3 in the integration of homeostatic cues for the maintenance and functional tuning of the T‐cell pool.

Simvastatin suppresses RANTES-mediated neutrophilia in polyinosinic–polycytidylic acid-induced pneumonia

Recently, statins have been shown to have anti-inflammatory effects on lung inflammatory diseases. However, the mechanisms of action of simvastatin in viral pneumonia have yet to be elucidated, although viral infection remains a considerable health threat. In this study, we hypothesised that simvastatin inhibits polyinosinic–polycytidylic acid (poly I:C)-induced airway inflammation, such as RANTES (regulated on activation, normal T-cell expressed and secreted) expression and inflammatory cell recruitment. In bronchial cells, the effect of simvastatin on poly I:C-induced RANTES expression and signal transducer and activator of transcription (STAT)3-mediated signal transduction was determined using an ELISA and short hairpin (sh)RNA system. In a poly I:C-induced pneumonia mouse model, immunological changes in the lungs after simvastatin inhalation, such as inflammatory cell recruitment and cytokine/chemokine release, were examined. In poly I:C-stimulated bronchial cells, RANTES secretion was increased by STAT3 activation, and simvastatin suppressed poly I:C-induced STAT3 activation, resulting in inhibition of RANTES expression. In BALB/c mice stimulated with inhaled poly I:C, RANTES expression and neutrophil infiltration into the airway were elevated. However, simvastatin treatment attenuated STAT3 activation, RANTES release and subsequent neutrophilia in the lungs. These findings suggest that simvastatin inhibits airway inflammation, but there are other mechanisms that need to be fully elucidated.

BST-2 is a potential activator of invasion and migration in tamoxifen-resistant breast cancer cells.

Bone marrow stromal cell antigen 2 (BST-2) is a type II transmembrane protein that is known to be a therapeutic target in several types of cancer. However, despite its clinical importance, the roles of BST-2 expression have remained elusive. Here, we found that BST-2 expression is up-regulated in tamoxifen-resistant MCF-7 human breast cancer (TRM-7) cells, resulting in enhanced invasiveness and migration. Matrigel and wound healing assays also showed that overexpression of BST-2 increased invasion and migration in MCF-7 cells, whereas invasion and migration were decreased by the silencing of BST-2 in TRM-7 cells. In addition, B16F10 cells expressing BST-2 showed increased metastatic melanoma nodule growth in a lung metastasis mouse model. Furthermore, BST-2 expression and promoter activity were regulated by activated signal transducer and activator of transcription 3 (STAT3). Taken together, our results indicate that BST-2 is an important factor in the invasiveness and motility of tamoxifen-resistant breast cancer cells, and that its expression and activity are regulated by activated STAT3. Therefore, regulation of BST-2 is a potential therapeutic target for tamoxifen-resistant breast cancer.