Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report herein a novel finding that under an unstimulated condition, a group of four human hepatocellular carcinoma (HCC) cell lines with varying degrees of differentiation, can spontaneously activate NF-KB. The propensity of activation coincided inversely with the differentiation status, with order being SK-Hep-1 > J5 > Hep3B > HepG2. Further studies indicate that this pattern of activation correlates excellently with the descending order of intracellular GSH/GSSG ratios as well as with the ascending order in the ability of these cells to generate hydrogen peroxide. Taken together, our data suggest that differentiation status may play a pivotal role in modulating intracellular thiol redox status and the extent of catalase expression, which may be crucial in the control of NF-kappaB activity in these HCC cells.
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PMID:Differentiation status modulates transcription factor NF-kappaB activity in unstimulated human hepatocellular carcinoma cell lines. 1076 22

Salvia miltiorrhiza (SM) is a traditional Chinese herbal medicine, commonly used to treat liver diseases in China for centuries. Several earlier studies have indicated that SM exhibits anti-tumor properties, but its mechanism remains to be elucidated. In this study, we evaluated the molecular mechanism of SM in a human hepatoma cell line, HepG(2). Our results show that SM exerted clear cytotoxic effects, and strongly inhibited the proliferation of HepG(2) cells. It was also observed that SM treatment caused apoptotic cell death as evaluated by: (a), morphological changes by using acridine orange/ethidium bromide staining; (b), DNA fragmentation by TdT-mediated dUTP nick end labeling (TUNEL); and (c), sub-G(1) cell analysis. Furthermore, depletion of intracellular glutathione (GSH) and reduction of mitochondrial membrane potential were found to be involved in the initiation of apoptosis by SM.
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PMID:Salvia miltiorrhiza inhibits cell growth and induces apoptosis in human hepatoma HepG(2) cells. 1077 35

Cultured cells are commonly exposed to trypsin-containing solutions in order to prepare cell suspensions suitable for subculture. Conditions used to release and disperse monolayers of cultured murine hepatoma 1c1c7 and human breast epithelial MCF10A cells caused the loss (40-95%) of cellular glutathione (GSH), but did not affect viability. Glutathione contents returned to pretrypsinization values within 24 h of replating. In contrast, the GSH contents of cultured rat hepatoma 5L cells were not affected by trypsinization. Exposure of 1c1c7 cultures to H(2)O(2) or etoposide 1 or 24 h after replating resulted in concentration-dependent cytostatic and cytotoxic effects. The concentration-response curves defining the cytostatic and cytotoxic effects of etoposide, and the cytostatic effects of H(2)O(2) were not influenced by the timing of toxicant addition. However, 1c1c7 cultures treated with H(2)O(2) 1 h after replating were more susceptible to the cytotoxic actions of the peroxide than cultures treated 24 h after plating. These studies show that conditions commonly used for the passaging of cultured cells can lead to a transient, but profound loss of GSH in some cell lines. Furthermore, the outcome of cytotoxicity analyses can be influenced by the time elapsed between the plating of cultures and the addition of toxicant.
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PMID:Depletion of cellular glutathione by conditions used for the passaging of adherent cultured cells. 1080 91

Alachlor, metolachlor, and propachlor are widely used chloroacetanilide herbicides. Their cytotoxicity in rat (Fa32) and human (Hep G2) hepatoma-derived cells was investigated, in connection with their influence on the endogenous glutathione (GSH) content, on the xenobiotic-metabolizing phase I enzymes 7-ethoxyresorufin O-deethylase (EROD) and 7-pentoxyresorufin O-depentylase (PROD), and phase II glutathione transferase (GST). The cytotoxicity was measured by the neutral red uptake inhibition assay. The following toxicity range was observed in both cell lines: propachlor > alachlor > metolachlor. When the endogenous GSH content was reduced by pretreatment of the cells with L-buthionine (S,R)-sulfoximine, the cytotoxicity of the herbicides increased strongly in both cell lines. EROD and PROD activities were dose-dependently increased to different degrees in Fa32, as was EROD in Hep G2, but no PROD activity was observed in these cells. The GSH content was not altered after 1 h treatment, and was approximately doubled after 24 h. GST activity was increased in Fa32 cells but not in Hep G2. A comparable cytotoxicity was observed for the investigated chloroacetanilides in both the rat and the human cell lines. Different interactions with xenobiotic-metabolizing phase I and II enzymes were observed, and GSH showed a protective effect against the acetanilides in both cell lines.
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PMID:Glutathione-dependent cytotoxicity of the chloroacetanilide herbicides alachlor, metolachlor, and propachlor in rat and human hepatoma-derived cultured cells. 1081 65

Direct exposure of human hepatoma cell line SMMC-7721 to hydrogen peroxide (H2O2) can induce apoptosis. Apoptosis induced by H2O2 was inhibited by cycloheximide, actinomycin D, 3-aminobenzamide, EGTA or Zn2+. H2O2 can increase the level of intracellular Ca2+, downregulate GSH levels, slightly induce lipid peroxidation, and lead to change in the ratio of reduced ion components to oxidized ion components of cells. Analysis of flow cytometry indicates that H2O2 decreases the level of Bcl-2. The data indicate that H2O2-induced apoptosis requires new mRNA and protein syntheses; H2O2 can activate Ca2+/Mg2+-dependent endonuclease leading to internucleosomal DNA fragmentation and activation of poly (ADP-ribose) polymerase interfering with the energy metabolism of the cell. The H2O2 downregulation of GSH may be more important for apoptosis than H2O2 induction of lipid peroxidation, and the H2O2 induced changes in redox status of the cell may be among the original events which lead up to other biochemical changes.
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PMID:Hydrogen peroxide induces apoptosis in human hepatoma cells and alters cell redox status. 1082 69

It is well known that glutathione, the major intracellular antioxidant, is closely involved in the metabolism and bioactivity of selenium. In the present study, glutathione was demonstrated to play a dual role on selenite (Se)-induced oxidative stress and apoptosis in human hepatoma HepG(2) cells. The experiment was carried out in two different modes to modulate intracellular reduced glutathione (GSH) content. In Mode A (pretreatment), cells were pretreated with N-acetylcysteine (NAC), buthionine sulfoximine (BSO), or GSH prior to Se exposure. In Mode B (simultaneous treatment), cells were treated with Se and NAC, BSO, or GSH simultaneously. It was found that Se-induced oxidative stress and apoptosis are closely related to the intracellular level of GSH. Both the increase and depletion of GSH content significantly enhanced Se-induced oxidative stress and apoptosis in HepG(2) cells. Results from this study clearly demonstrated that GSH has a dual role in the effects of Se on cancer cells: (i) GSH acts as a pro-oxidant, facilitating Se-induced oxidative stress, and (ii) GSH acts as an antioxidant, protecting against Se-induced oxidative stress and apoptosis. Understanding such a unique association between GSH and Se may help to explain the controversy in the literature over the complex relationship between selenium and glutathione, and ultimately the capability of selenium to prevent cancer.
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PMID:Dual role of glutathione in selenite-induced oxidative stress and apoptosis in human hepatoma cells. 1083 73

Isothiocyanates (ITCs) are abundant in the human diet. Many potently inhibit tumorigenesis induced by a wide variety of chemical carcinogens in rodents. Recently, we observed that several ITCs accumulated to very high concentrations in cultured cells and that their accumulated levels were closely related to their potencies in inducing phase II enzymes [NAD(P)H:quinone reductase and glutathione transferases] that detoxify carcinogens. To elucidate the molecular mechanism responsible for this accumulation, the intracellular chemical identities of two ITCs, sulforaphane [SF, 1-isothiocyanato-(4R,S)-(methylsulfinyl)butane] and benzyl-ITC, were investigated in murine hepatoma cells. Both ITCs accumulated very rapidly to high intracellular concentrations, but, remarkably, most of the intracellular forms of the ITCs were dithiocarbamates resulting from conjugation with reduced glutathione (GSH). For example, the intracellular concentration reached 6.4 mM when cells were exposed to 100 microM SF for 30 min at 37 degrees C and 95% of the accumulated product was the GSH conjugate. Cellular accumulation of each ITC was accompanied by a profound reduction in cellular GSH levels. These findings, together with our previous observation that accumulation of ITCs depended on cellular GSH levels, strongly suggest that intracellular conjugation of ITCs with GSH is mainly responsible for ITC accumulation. Surprisingly, rapid accumulation to high concentrations also occurred when cells were exposed to the GSH-ITC conjugates. However, these conjugates were apparently not absorbed intact, but were hydrolyzed extracellularly to free ITCs that were taken up by the cells. This conclusion is supported by the finding that suppression of dissociation of the conjugates by excess GSH or other thiols blocks accumulation of the conjugates.
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PMID:Role of glutathione in the accumulation of anticarcinogenic isothiocyanates and their glutathione conjugates by murine hepatoma cells. 1083 7

A method is described for measuring bioreduction of hydroxyethyl disulfide (HEDS) or alpha-lipoate by human A549 lung, MCF7 mammary, and DU145 prostate carcinomas as well as rodent tumor cells in vitro. Reduction of HEDS or alpha-lipoate was measured by removing aliquots of the glucose-containing media and measuring the reduced thiol with DTNB (Ellman's reagent). Addition of DTNB to cells followed by disulfide addition directly measures the formation of newly reduced thiol. A549 cells exhibit the highest capacity to reduce alpha-lipoate, while Q7 rat hepatoma cells show the highest rate of HEDS reduction. Millimolar quantities of reduced thiol are produced for both substrates. Oxidized dithiothreitol and cystamine were reduced to a lesser degree. DTNB, glutathione disulfide, and cystine were only marginally reduced by the cell cultures. Glucose-6-phosphate deficient CHO cells (E89) do not reduce alpha-lipoate and reduce HEDS at a much slower rate compared to wild-type CHO-K1 cells. Depletion of glutathione prevents the reduction of HEDS. The depletion of glutathione inhibited reduction of alpha-lipoate by 25% and HEDS by 50% in A549 cells, while GSH depletion did not inhibit alpha-lipoate reduction in Q7 cells but completely blocked HEDS reduction. These data suggest that the relative participation of the thioltransferase (glutaredoxin) and thioredoxin systems in overall cellular disulfide reduction is cell line specific. The effects of various inhibitors of the thiol-disulfide oxidoreductase enzymes (1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), arsenite, and phenylarsine oxide) support this conclusion.
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PMID:A method for measuring disulfide reduction by cultured mammalian cells: relative contributions of glutathione-dependent and glutathione-independent mechanisms. 1084 13

Ebselen, a selenoorganic compound, has recently been shown to display a novel property of inducing apoptosis through rapid depletion of intracellular thiols in human hepatoma cells, HepG(2). The present study was thus designed to explore the mechanism of how ebselen triggers apoptosis upon depletion of intracellular thiols. The results demonstrated that ebselen treatment triggered mitochondrial permeability transition rather rapidly as revealed by redistribution of calcein green fluorescence from cytosol into mitochondria. Ebselen treatment also caused a dose- and time-dependent loss of mitochondrial membrane potential (MMP) and release of cytochrome c. Pretreatment with N-acetylcysteine, a precursor of intracellular reduced glutathione (GSH) synthesis, significantly attenuated the ebselen-induced MMP disruption and subsequently inhibited the apoptosis. In contrast, pretreatment with buthionine sulfoximine, a specific inhibitor of intracellular GSH synthesis, significantly augmented the ebselen-induced MMP alteration, and enhanced the apoptosis. Although ebselen treatment significantly increased the intracellular superoxide radical and calcium concentrations, superoxide dismutase, and BAPTA (a calcium chelator), however, failed to prevent ebselen-induced MMP loss and apoptosis. Neither caspase-9 nor caspase-3 activation was detected in ebselen-treated cells. Z-VAD-FMK, a general caspase inhibitor, also had no effect on ebselen-induced MMP decrease and apoptosis. The overall findings thus suggest that mitochondrial permeability transition resulted from intracellular thiol depletion is a critical event in ebselen-induced apoptosis.
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PMID:Intracellular thiol depletion causes mitochondrial permeability transition in ebselen-induced apoptosis. 1093 87

Persistent infection by hepatitis B virus (HBV) and exposure to chemical carcinogens correlates with the prevalence of hepatocellular carcinoma in endemic areas. The precise nature of the interaction between these factors is not known. Glutathione S-transferases (GST) are responsible for the cellular metabolism and detoxification of a variety of cytotoxic and carcinogenic compounds by catalysis of their conjugation with glutathione. Diminished GST activity could enhance cellular sensitivity to chemical carcinogens. We have investigated GST isozyme expression in hepatocellular HepG2 cells and in an HBV-transfected subline. Total GST activity and selenium-independent glutathione peroxidase activity are significantly decreased in HBV transfected cells. On immunoblotting, HBV transfected cells demonstrate a significant decrease in the level of GST Alpha class. Cytotoxicity assays reveal that the HBV transfected cells are more sensitive to a wide range of compounds known to be detoxified by GST Alpha conjugation. Although no significant difference in protein half-life between the two cell lines was found, semi-quantitative reverse transcription-polymerase chain reaction shows a reduced amount of GST Alpha mRNA in the transfected cells. Because the HBV x protein (HBx) seems to play a role in HBV transfection, we also demonstrated that expression of the HBx gene into HepG2 cells decreased the amount of GST Alpha protein. Transient transfection experiments using both rat and human GST Alpha (rGSTA5 and hGSTA1) promoters in HepG2 cells show a decreased CAT activity upon HBx expression, supporting a transcriptional regulation of both genes by HBx. This effect is independent of HBx interaction with Sp1. Treatment with oltipraz, an inducer of GST Alpha, partially overcomes the effect of HBx on both promoters. Promoter deletion studies indicate that oltipraz works through responsive elements distinct from AP1 or NF-kappaB transcription factors. Thus, HBV infection alters phase II metabolizing enzymes via different mechanisms than those modulated by treatment with oltipraz.
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PMID:Modulation of glutathione S-transferase alpha by hepatitis B virus and the chemopreventive drug oltipraz. 1093 96


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