Eun Hye Jho

Lignans inhibit cell growth via regulation of Wnt/β-catenin signaling

As aberrant activation of Wnt/beta-catenin signaling is one of the major mechanisms of carcinogenesis in colon cancer, identification of inhibitors of this pathway may aid in colon cancer prevention. We investigated the ability of the lignans arctiin, matairesinol and arctigenin from Saussurea salicifolia to inhibit Wnt/beta-catenin signaling in SW480 human colon cancer cells. The lignans inhibited SW480 cell growth. In addition, the transcriptional activity of a reporter construct containing the TCF binding element (TBE) was decreased after the treatment with all three lignans. Although arctiin, matairesinol and arctigenin have similar structures, arctigenin affected Wnt/beta-catenin signaling most significantly. Further, arctigenin reduced the level of beta-catenin by inducing its phosphorylation and thus its degradation. Arctigenin also decreased expression of the beta-catenin/TCF downstream genes CCND1, survivin and CTNNB1, and induced apoptosis. These results suggest that arctigenin, an aglycone with a methoxyl group, potently inhibits the growth of human colon cancer cells via the Wnt/beta-catenin signaling pathway.

Hepatoprotective Effect of Flavonoid Glycosides from Lespedeza cuneata against Oxidative Stress Induced by tert-Butyl Hyperoxide

The aerial parts of Lespedeza cuneata G. Don, perennial legume native to Eastern Asia, have been used therapeutically in traditional Asian medicine to protect the function of liver, kidneys and lungs. However, little is known about the pharmaceutical effect of extracts from this plant. In the present study, the aerial parts of L. cuneata were used to prepare an ethanol extract, which was then tested for hepatoprotective effects against injury by tert‐butyl hyperoxide (t‐BHP). At a dose of 20 μg/mL, the ethanol extract significantly protected HepG2 cells against the cytotoxicity of t‐BHP. Further fractionation of the extract with ethyl acetate allowed the isolation of five flavonoid compounds that were structurally identified by 1H and 13C NMR spectroscopy as isovitexin, hirsutrin, trifolin, avicularin and quercetin. Hirsutrin, avicularin and quercetin (10 μm) showed clear hepatoprotective activity against injury by t‐BHP in HepG2 cells, whereas isovitexin and trifolin showed no protective effects. The observed hepatoprotective effect of the investigated compounds showed a high correlation with radical scavenging activity, which followed the structure–activity relationships of the flavonoid aglycones. Copyright

Youngia denticulata Protects Against Oxidative Damage Induced by tert-Butylhydroperoxide in HepG2 Cells

Improvement of liver function is one of the most popular commercial health claims of functional foods in Asian countries, including Korea. After examining the potential of several traditional Korean wild vegetables for enhancing liver function, we found that Youngia denticulata Kitam. has strong hepatoprotective effects against oxidative stress induced by tert-butylhydroperoxide (t-BHP). We are the first to report that the extract and ethyl acetate fractions of Y. denticulata have radical scavenging activities and inhibit oxidative stress-induced cell death and DNA damage in HepG2 cells. The extract and ethyl acetate fractions significantly decreased cellular reactive oxygen species production and apoptosis induced by t-BHP in HepG2 cells. In addition, they prevented the depletion of cellular glutathione, which is an important defense molecule against oxidizing xenobiotics. Chlorogenic acid and 3,5-dicaffeoylquinic acid were found to be major active components responsible for the activity of Y. denticulata and could serve as marker compounds for standardization. These data suggest that Y. denticulata could be promoted as a potential antioxidative functional food candidate, particularly for hepatoprotection against oxidative stress.

A polyacetylene from Gymnaster koraiensis exerts hepatoprotective effects in vivo and in vitro.

In the present study, we isolated a polyacetylene, gymnasterkoreayne B (GKB), from Gymnaster koraiensis and investigated the effect of GKB on the protection from oxidative stress-induced cytotoxicity through induction of the expression of cellular defense enzymes. GKB induced mRNA expression and enzyme activity of NAD(P)H:quinone oxidoreductase (NQO1) in vitro and in vivo, and potently increased expression of many cellular defense genes including glutathione-S-transferases, UDP-glucuronosyltransferase, and glutathione reductase (GSR) in normal rat liver. The nuclear factor erythroid 2-related factor 2 (Nrf2) which is known to induce various antioxidant and cytoprotective genes, and the genes containing the antioxidant response element (ARE), including NQO1, hemeoxygenease-1, GSR were induced by GKB in HepG2 human hepatocarcinoma cells. Pre-treatment of the cells with GKB accelerated the production of glutathione and mitigated menadione-induced cytotoxicity in HepG2 cells. Taken together, we found that GKB was a novel inducer of phase II detoxification enzymes and cellular defense enzymes, resulting in protection of the cells from oxidative stress and hepatotoxicity through regulation of detoxifying and antioxidant systems.

Gymnaster koraiensis and its major components, 3,5-di-O-caffeoylquinic acid and gymnasterkoreayne B, reduce oxidative damage induced by tert-butyl hydroperoxide or acetaminophen in HepG2 cells

We investigated the protective effects of Gymnaster koraiensis against oxidative stress-induced hepatic cell damage. We used two different cytotoxicity models, i.e., the administration of tert-butyl hydroperoxide (t-BHP) and acetaminophen, in HepG2 cells to evaluate the protective effects of G. koraiensis. The ethyl acetate (EA) fraction of G. koraiensis and its major compound, 3,5-di-O-caffeoylquinic acid (DCQA), exerted protective effects in the t-BHP-induced liver cytotoxicity model. The EA fraction and DCQA ameliorated t-BHP-induced reductions in GSH levels and exhibited free radical scavenging activity. The EA fraction and DCQA also significantly reduced t-BHP-induced DNA damage in HepG2 cells. Furthermore, the hexane fraction of G. koraiensis and its major compound, gymnasterkoreayne B (GKB), exerted strong hepatoprotection in the acetaminopheninduced cytotoxicity model. CYP 3A4 enzyme activity was strongly inhibited by the extract, hexane fraction, and GKB. The hexane fraction and GKB ameliorated acetaminophen-induced reductions in GSH levels and protected against cell death. [BMB Reports 2013; 46(10): 513-518]

The chemopreventive effects of Carpesium abrotanoides are mediated by induction of phase II detoxification enzymes and apoptosis in human colorectal cancer cells.

Cancer chemoprevention is thought to occur either by blocking the initiation of or suppressing the promotion of carcinogenesis. Phase II detoxification enzymes are known to play important roles in cancer chemoprevention because they enhance cytoprotection through detoxification and elimination of activated carcinogens at tumor initiation. Apoptosis is one of the most important inhibitory targets for tumor promotion. In this study, we have investigated the cancer chemopreventive activity of the ethanolic extract of Carpesium abrotanoides (CAE). We found that CAE induced quinone reductase [also known as NAD(P)H:quinone oxidoreductase (NQO1)] activity, increased NQO1 mRNA and protein expression, and had a relatively high chemoprevention index (12.04). CAE also significantly activated the antioxidant response element through the nuclear accumulation of NF-E2-related factor 2 in HCT116. Interestingly, we also found that CAE induced apoptosis, as evidenced by the externalization of phosphatidylserine, increased sub-G(0)/G(1) content, chromatin condensation, poly(ADP-ribose) polymerase cleavage, and p53. These data suggest that the chemopreventive effects of C. abrotanoides can result from both the induction of phase II detoxification enzymes and from apoptosis. Thus, CAE could potentially be developed as a cancer chemopreventive agent for prevention or treatment of human cancers.

Cell and Nuclear Enlargement of SW480 Cells Induced by a Plant Lignan, Arctigenin: Evaluation of Cellular DNA Content Using Fluorescence Microscopy and Flow Cytometry

Arctigenin is a natural plant lignan previously shown to induce G(2)/M arrest in SW480 human colon cancer cells as well as AGS human gastric cancer cells, suggesting its use as a possible cancer chemopreventive agent. Changes in cell and nuclear size often correlate with the functionality of cancer-treating agents. Here, we report that arctigenin induces cell and nuclear enlargement of SW480 cells. Arctigenin clearly induced the formation of giant nuclear shapes in SW480, as demonstrated by fluorescence microscopic observation and quantitative determination of nuclear size. Cell and nuclear size were further assessed by flow cytometric analysis of light scattering and fluorescence pulse width after propidium iodide staining. FSC-H and FL2-W values (parameters referring to cell and nuclear size, respectively) significantly increased after arctigenin treatment; the mean values of FSC-H and FL2-W in arctigenin-treated SW480 cells were 572.6 and 275.1, respectively, whereas those of control cells were 482.0 and 220.7, respectively. Our approach may provide insights into the mechanism behind phytochemical-induced cell and nuclear enlargement as well as functional studies on cancer-treating agents.