Hye Jin Hwang

Nrg1 Is a Transcriptional Repressor for Glucose Repression of STA1 Gene Expression in Saccharomyces cerevisiae

ABSTRACT Expression of genes encoding starch-degrading enzymes is regulated by glucose repression in the yeast Saccharomyces cerevisiae. We have identified a transcriptional repressor, Nrg1, in a genetic screen designed to reveal negative factors involved in the expression of STA1, which encodes a glucoamylase. TheNRG1 gene encodes a 25-kDa C2H2zinc finger protein which specifically binds to two regions in the upstream activation sequence of the STA1 gene, as judged by gel retardation and DNase I footprinting analyses. Disruption of theNRG1 gene causes a fivefold increase in the level of theSTA1 transcript in the presence of glucose. The expression of NRG1 itself is inhibited in the absence of glucose. DNA-bound LexA-Nrg1 represses transcription of a target gene 10.7-fold in a glucose-dependent manner, and this repression is abolished in bothssn6 and tup1 mutants. Two-hybrid and glutathione S-transferase pull-down experiments show an interaction of Nrg1 with Ssn6 both in vivo and in vitro. These findings indicate that Nrg1 acts as a DNA-binding repressor and mediates glucose repression of the STA1 gene expression by recruiting the Ssn6-Tup1 complex.

Naringenin up-regulates the expression of death receptor 5 and enhances TRAIL-induced apoptosis in human lung cancer A549 cells.

SCOPEnWhile TRAIL is relatively non-toxic to normal cells, it can selectively induce apoptosis in many types of transformed cells. Nevertheless, some non-small cell lung cancer (NSCLC) cells are particularly resistant to the effects of TRAIL. Here, we report that in combination with naringenin exposure to TRAIL induced apoptosis in TRAIL-resistant NSCLC A549 cells with no detectable inhibitory effects on cell proliferation of normal lung fibroblast cells.nnnMETHODS AND RESULTSnCytotoxicity was evaluated by MTT assay. Apoptosis was detected using DAPI staining, and flow cytometry. The protein levels were determined by Western blot analysis. Caspase activity was measured using a colorimetric assay. For knockdown of Bid and DR5 expression, Bid and DR5 siRNAs were transfected into cells via lipofection. We could show that following exposure to naringenin, DR5 proteins were up-regulated and knockdown of DR5 expression by siRNA attenuated naringenin plus TRAIL-induced apoptosis. Naringenin and TRAIL effectively induced Bid cleavage and siRNA-mediated silencing of Bid reduced the sensitizing effect of naringenin. Furthermore, co-treatment with naringenin and TRAIL resulted in reduction of the clonogenic capacity of A549 cells, and surviving clones could be re-sensitized for repeated TRAIL treatment.nnnCONCLUSIONnOur results indicate that treatment with a combination of TRAIL and naringenin may be a safe strategy for treatment of resistant NSCLC.

Inhibition of Matrix Metalloproteinase Activities and Tightening of Tight Junctions by Diallyl Disulfide in AGS Human Gastric Carcinoma Cells

The effect of diallyl disulfide (DADS), a major component of an oil-soluble allyl sulfide garlic (Allium sativum) derivative, on the correlation between anti-invasive activity and tightening of tight junctions (TJs) was investigated in human gastric adenocarcinoma AGS cells. Our data indicated that the inhibitory effects of DADS on cell motility and invasiveness were found to be associated with increased tightness of the TJs, which was demonstrated by an increase in transepithelial electrical resistance. Activities of matrix metalloprotease (MMP)-2 and -9 in AGS cells were dose-dependently inhibited by treatment with DADS, and this was also correlated with a decrease in expression of their mRNA and proteins; however, tissue inhibitor of metalloproteinase (TIMP)-1 and -2 mRNA levels and proteins were increased. Additionally, immunoblotting results indicated that DADS repressed the levels of claudin proteins (claudin-2, -3, and -4), major components of TJs that play key roles in control and selectivity of paracellular transport. Although further studies are needed, these results suggest that DADS treatment may inhibit tumor cell motility and invasion and, therefore, act as a dietary source to decrease the risk of cancer metastasis.

Induction of apoptosis by esculetin in human leukemia U937 cells: roles of Bcl-2 and extracellular-regulated kinase signaling.

In the present study, we reported that apoptosis induced by esculetin, a phenolic compound with apoptotic activity in cancer cells, was markedly blocked by Bcl-2-overexpression, but restored by HA14-1, a small-molecule Bcl-2 inhibitor, in human leukemic U937 cells. The combined use of esculetin and HA14-1 effectively induced Bid cleavage and loss of mitochondrial membrane potential (MMP, Deltapsi(m)) leading to the activation of caspases and cleavage of poly(ADP-ribose) polymerase (PARP) in Bcl-2-overexpressing (U937/Bcl-2) cells. Combined treatment with esculetin and HA14-1 upregulated the expression of death receptor 4 (DR4), and activation of extracellular-regulated kinase (ERK) in a time-dependent manner. In addition, esculetin and HA14-1-mediated apoptosis was reduced by ERK inhibitors through inhibition of DR4 expression, suggesting that the synergistic effect was at least partially mediated through ERK-dependent induction of DR4 expression. The results indicate that HA14-1-induced reversal of the anti-apoptotic effect of Bcl-2 confers apoptosis sensitivity to esculetin by a mitochondrial amplification step and through the ERK-dependent induction of DR4 expression in U937/Bcl-2 cells. Thus, HA14-1 reversal of Bcl-2-mediated esculetin resistance suggests a novel strategy for increasing esculetin sensitivity in Bcl-2-overexpressing leukemia cells.

Citrus aurantium L. exhibits apoptotic effects on U937 human leukemia cells partly through inhibition of Akt

Citrus fruits have been used as edible fruits and a traditional medicine since ancient times. In particular, the peels of immature citrus fruits are frequently prescribed in concert with other support herbs for many types of disease including cancer. We investigated the anti-proliferative activity of the peels of Citrus aurantium L. along with their effects on apoptosis. We prepared crude methanol extracts of the peels of Citrus aurantium L. (CMEs) and performed experiments using U937 human leukemia cells. The growth of U937 cells was inhibited by CME treatment in a dose-dependent manner, and CME induced caspase-dependent apoptosis. CME inhibited the expression of XIAP and Bcl-xL which are anti-apoptotic proteins. CME inhibited Akt activity in a dose-dependent manner. The apoptotic activity of CME was significantly attenuated by Akt augmentation. In conclusion, this study suggested that CME should induce caspase-dependent apoptosis at least in part through Akt inhibition, providing evidence that CMEs have anticancer activity on human leukemia cells.

Essential oils purified from Schisandrae semen inhibits tumor necrosis factor-α-induced matrix metalloproteinase-9 activation and migration of human aortic smooth muscle cells

BackgroundThe migration of vascular smooth muscle cells from the tunica media to the subendothelial region may be a key event in the development of atherosclerosis after arterial injury. In this study, we investigated the potential mechanisms underlying the anti-atherosclerotic effects of Schisandrae Semen essential oil (SSeo) in human aortic smooth muscle cells (HASMCs).MethodsMetalloproteinase-2/9 (MMP-2/9) activity was evaluated by gelatin zymography and gelatinase activity assay kit. The possible mechanisms underlying SSeo-mediated reduction of by tumor necrosis factor (TNF)-α-induced cell invasion and inhibition of secreted and cytosolic MMP-9 production in HASMCs were investigated.ResultsOur results indicate that SSeo treatment has an inhibitory effect on activation as well as expression of MMP-9 induced by TNF-α in HASMCs in a dose-dependent manner without significant cytotoxicity. SSeo attenuated nuclear translocation of TNF-α-mediated nuclear factor-kappa B (NF-κB) and blocked degradation of the NF-κB inhibitor proteins as well as the production of reactive oxygen species. SSeo also reduced TNF-α-induced production of pro-inflammatory mediators such as nitric oxide and prostaglandin E2 and inhibited inducible nitric oxide synthase and cyclooxygenase-2 expression in HASMCs. Furthermore, the Matrigel migration assay showed that SSeo effectively reduced TNF-α-induced HASMC migration compared with that in the control group.ConclusionsTaken together, these results suggest that SSeo treatment suppresses TNF-α-induced HASMC migration by selectively inhibiting MMP-9 expression, which was associated with suppression of the NF-κB signaling pathway. Taken together, these results suggest that SSeo has putative potential anti-atherosclerotic activity.

Schisandrae semen essential oil attenuates oxidative stress-induced cell damage in C2C12 murine skeletal muscle cells through Nrf2‑mediated upregulation of HO‑1

The aim of the present study was to examine the cytoprotective effects of Schisandrae semen essential oil (SSeo), purified from Schisandrae fructus, against oxidative stress-induced cell damage in C2C12 myoblasts. SSeo attenuated hydrogen peroxide (H2O2)-induced growth inhibition and exhibited scavenging activity against the intracellular reactive oxygen species (ROS) that were induced by H2O2. SSeo also inhibited comet tail formation, chromatin condensation and phosphor-histone γH2A.X expression, suggesting that it prevents H2O2-induced cellular DNA damage and apoptotic cell death. Furthermore, SSeo significantly enhanced the expression of heme oxygenase-1 (HO‑1) associated with the induction of nuclear factor erythroid-2-related factor 2 (Nrf2) in a time- and concentration‑dependent manner. In addition, the protective effect of SSeo on H2O2‑induced C2C12 cell damage was significantly inhibited by zinc protoporphyrin IX, an HO‑1 competitive inhibitor, in C2C12 cells. These findings suggest that SSeo augments the cellular antioxidant defense capacity through intrinsic free radical scavenging activity and activation of the Nrf2/HO‑1 pathway, thereby protecting the C2C12 cells from H2O2‑induced oxidative cytotoxicity. As a result, SSeo may have therapeutic potential in the development of functional foods and as the raw material for medicines to protect against oxidative stress.

Induction of reactive oxygen species-mediated apoptosis by purified Schisandrae semen essential oil in human leukemia U937 cells through activation of the caspase cascades and nuclear relocation of mitochondrial apoptogenic factors

The aim of this study was to evaluate the beneficial effects of Schisandrae semen essential oil (SSeo) on apoptosis events and the mechanisms associated with these effects in human leukemia U937 cells. The treatment of U937 cells with SSeo significantly inhibited survival and induced apoptosis. Schisandrae semen essential oil treatment increased the levels of death receptors and Fas, and activated caspases accompanied by proteolytic degradation of poly(ADP-ribose)-polymerase, which was associated with the downregulation of members of the inhibitor of apoptosis protein family protein expression; however, a pan-caspase inhibitor reversed SSeo-induced apoptosis. Treating the cells with SSeo also caused truncation of Bid, translocation of proapoptotic Bax to the mitochondria, and loss of mitochondrial membrane permeabilization, thereby inducing the release of cytochrome c into the cytosol. Subsequently, SSeo upregulated the translocation of mitochondrial apoptogenic factors, such as endonuclease G and apoptosis-inducing factor, into the nucleus during the apoptotic process. Notably, SSeo immediately increased the generation of intracellular reactive oxygen species (ROS); however, pretreatment with N-acetylcysteine, a common ROS quencher, almost completely blocked SSeo-induced apoptosis. Taken together, these findings indicate that SSeo caused ROS- and caspase-dependent cell death involving mitochondrial dysfunction and nuclear translocation of mitochondrial proapoptosis proteins. Based on our data, the consumption of Schisandrae semen or its essential oil is a good natural therapeutic agent for anticancer activity and regression.

Sargassum horneri methanol extract rescues C2C12 murine skeletal muscle cells from oxidative stress-induced cytotoxicity through Nrf2-mediated upregulation of heme oxygenase-1

BackgroundSargassum horneri, an edible marine brown alga, is typically distributed along the coastal seas of Korea and Japan. Although several studies have demonstrated the anti-oxidative activity of this alga, the regulatory mechanisms have not yet been defined. The aim of the present study was to examine the cytoprotective effects of S. horneri against oxidative stress-induced cell damage in C2C12 myoblasts.MethodsWe demonstrated the anti-oxidative effects of a methanol extract of S. horneri (SHME) in a hydrogen peroxide (H2O2)-stimulated C2C12 myoblast model. Cytotoxicity was determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyl-tetrazolium assay and mode of cell death by cell cycle analysis. DNA damage was measured using a comet assay and expression of phospho-histone γH2A.X (p-γH2A.X). Levels of cellular oxidative stress as reactive oxygen species (ROS) accumulation were measured using 2’,7’-dichlorofluorescein diacetate. The involvement of selected genes in the oxidative stress-mediated signaling pathway was explored using Western blot analysis.ResultsSHME attenuated H2O2-induced growth inhibition and exhibited scavenging activity against intracellular ROS that were induced by H2O2. The SHME also inhibited comet tail formation, p-γH2A.X expression, and the number of sub-G1 hypodiploid cells, suggesting that it prevents H2O2-induced cellular DNA damage and apoptotic cell death. Furthermore, the SHME significantly enhanced the expression of heme oxygenase-1 (HO-1) associated with induction of nuclear factor-erythroid 2 related factor 2 (Nrf2) in a time- and concentration-dependent manner. Moreover, the protective effect of the SHME on H2O2-induced C2C12 cell damage was significantly abolished by zinc protoporphyrin IX, a HO-1 competitive inhibitor, in C2C12 cells.ConclusionsThese findings suggest that the SHME augments cellular antioxidant defense capacity through both intrinsic free radical scavenging activity and activation of the Nrf2/HO-1 pathway, protecting C2C12 cells from H2O2-induced oxidative cytotoxicity.

Sargassum serratifolium attenuates RANKL-induced osteoclast differentiation and oxidative stress through inhibition of NF-κB and activation of the Nrf2/HO-1 signaling pathway

Sargassum serratifolium C. Agardh is a marine brown alga that has long been used as an ingredient for food and medicine by many people living along Asian coastlines. Recently, various beneficial effects of extracts or compounds isolated from S. serratifolium have been reported, but their efficacies against bone destruction are unclear. Therefore, in this study, we investigated the inhibitory property of an ethanol extract of S. serratifolium (EESS) on osteoclast differentiation by focusing on the receptor activator of nuclear factor-κB ligand (RANKL)-stimulated osteoclastogenesis model using RAW 264.7 macrophages. Our results demonstrated that EESS reduced RANKL-induced osteoclast differentiation in RAW 264.7 cells, by inhibiting tartrate-resistant acid phosphatase (TRAP) activity and destroying the F-actin ring formation. EESS also attenuated RANKL-induced expressions of key osteoclast-specific genes, such as nuclear factor of activated T cells cytoplasmic 1 (NFATC1), TRAP, cathepsin K and matrix metalloproteinase-9. These effects were mediated by impaired nuclear translocation of nuclear factor (NF)-κB and suppression of IκB-α degradation. In addition, EESS effectively inhibited the production of reactive oxygen species (ROS) by RANKL, which was associated with enhanced expression of nuclear translocation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Overall, our findings provide evidence that EESS suppresses RANKL-induced osteoclastogenesis and oxidative stress through suppression of NF-κB and activation of Nrf2/HO-1 signaling pathway, indicating that S. serratifolium has a potential application the prevention and treatment of osteoclastogenic bone disease.