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)

Glutathione-doxorubicin (GSH-DXR) effectively induced apoptosis in rat hepatoma cells (AH66) at a lower concentration than DXR. After 24 h of drug treatment, DNA fragmentation of the cells was observed at the concentration of 1.0 microM DXR or 0.01 microM GSH-DXR. Increase in caspase-3 activity and DNA fragmentation were observed within 12 h and 15 h after treatment with either drug. Intracellular caspase-3 activity was increased in a dose-dependent manner after treatment with DXR or GSH-DXR, and caspase-3 activity correlated well with the ability to induce DNA fragmentation. When the cells were treated with either DXR or GSH-DXR for only 6 h, apoptotic DNA degradation and caspase-3 activation occurred 24 h after treatment. DNA fragmentation caused by these drugs was prevented completely by simultaneous treatment with the caspase-3 inhibitor, acetyl-Asp-Glu-Val-Asp-aldehyde (DEVD-CHO), at 10 microM. By contrast, DNA fragmentation was not prevented by the caspase-1 inhibitor, acetyl-Tyr-Val-Ala-Asp-aldehyde (YVAD-CHO), at the same concentration as DEVD-CHO, and caspase-1 was not activated at all by the treatment of AH66 cells with both DXR and GSH-DXR. These results demonstrate that DXR and GSH-DXR induce apoptotic DNA fragmentation via caspase-3 activation, but not via caspase-1 activation, and that GSH-DXR enhances the activation of caspase-3 approximately 100-fold more than DXR. Moreover, the findings suggested that an upstream apoptotic signal that can activate caspase-3 is induced within 6 h by treating AH66 cells with the drug.
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PMID:Caspase-3 activation during apoptosis caused by glutathione-doxorubicin conjugate. 1036 Jun 48

In previous studies, we reported that fasting/refeeding has a role in sustaining the initiation of liver cancer by a subnecrogenic (noninitiating) dose of diethylnitrosamine (DENA). This research investigated whether the metabolic alterations imposed by fasting/refeeding provide an imbalance between the generation of carcinogenic molecules and the scavenger defense mechanisms in rat liver. Metabolism of DENA, levels of reduced glutathione (GSH) and GSH transferase (GST) activity, as well as basal and stimulated malondialdehyde (MDA) production, were examined. Rats fasted for 4 days showed a decrease in the liver levels of GSH, GST activity, monounsaturated fatty acids and % of labeled nuclei. After 1 day of refeeding, at which point DENA was administered, the levels of GSH recovered, GST activity remained below control values, basal and stimulated MDA production and content of total polyunsaturated fatty acids in liver phospholipids decreased. One day after DENA treatment, MDA production further decreased, although the % of labeled nuclei increased. No significant changes in the content of arachidonic acid, the main target of peroxidation, were observed at any time. The results indicated that the induction of the hepatocellular carcinoma was associated with a depression of GST activity and lipid peroxidation when rats were given 20 mg/kg of DENA after 1 day of refeeding after 4-day fasting.
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PMID:Liver cancer is induced by a subnecrogenic dose of DENA when associated with fasting/refeeding: role of glutathione-transferase and lipid peroxidation. 1038 Dec 5

Amiloride and its more potent analog, hexamethylene amiloride (HMA), inhibits Na+ :H+ exchange and decreases intracellular pH in a concentration-dependent way in two human hepatocarcinoma cell lines and in a rat hepatocarcinoma cell line that differs in its phenotypic characteristics, resembling the clinical situation encountered in human hepatocarcinomas. After 24 h of exposure, DNA synthesis and cell protein content of the cultures decreases according to the concentration of the drugs and in parallel to Na+ exchange inhibition and the drop in pHi promoted. RNA and protein syntheses are less sensitive to its action. The above effects induced by HMA are accompanied by an abrupt decrease in cell viability and lysosomal integrity at 24 h. These effects develop gradually with the exposure time as does the increase in free radical production. Decreased viability is totally or partially restored by N-acetylcysteine or deferoxamine, but the degree of intracellular acidification produced is not. These results tend to suggest that intracellular acidification can diminish cell growth and provoke cytotoxic cell death by diminishing reduced glutathione (GSH) levels and impairing lysosomal integrity, reflecting the sensitivity of hepatocarcinoma cells to Na+ exchange inhibition and intracellular acidosis.
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PMID:Na+ :H+ exchange inhibition induces intracellular acidosis and differentially impairs cell growth and viability of human and rat hepatocarcinoma cells. 1040 66

The antioxidant defence system which plays a critical role in carcinogenesis is severely altered in aflatoxin B1 induced hepatocellular carcinoma conditions. In order to assess the antitumour activity of Semecarpus anacardium nut extract, a flavonoid containing drug, non-enzymic antioxidant levels were analysed in control and experimental animals. Plasma was analysed for uric acid, vitamin E and vitamin C. Glutathione, total thiols, non-protein thiols, vitamin E, vitamin C and cytochrome P450 were estimated in liver and kidney homogenates. Depletion of all these antioxidants were recorded in cancer conditions. These deleterious effects are controlled by the administration of Semecarpus anacardium nut extract. Following drug administration, there was a marked increase in antioxidant levels and a dramatic elevation in cytochrome P450 content. It can be concluded that the observed anticancer property of Semecarpus anacardium nut extract may also be explained by its strong antioxidant capacity and capability to induce the in vivo antioxidant system.
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PMID:Semecarpus anacardium L. nut extract administration induces the in vivo antioxidant defence system in aflatoxin B1 mediated hepatocellular carcinoma. 1043 69

1. Several ozonides, peroxides and aldehydes are formed during ozone therapy, recently introduced in medicine. tert-Butyl hydroperoxide (t-BHP), H2O2 and diamide were investigated as model substrate in rat hepatoma-derived Fa32 cells. 2. The cytotoxicity was measured by the neutral red uptake inhibition assay after 1 h or 24 h treatment. The relative toxicities were quantified by the determination of the NI50. This is the concentration of test compound required to induce an inhibition of 50% in neutral red uptake as compared to the control cells. All test chemicals were more toxic after 24 h than after 1 h. 3. The influence of the glutathione (GSH) alteration on the cytotoxicity was measured by treating the cells with 2-oxo-4-thiazolidine carboxylic acid (OTC) or L-buthionine sulfoximine (BSO). OTC increased the endogenous GSH content in the cells. BSO pretreatment strongly decreased the NI50 of the three chemicals. OTC pretreatment increased the NI50 of H2O2 but not of t-BHP and diamide. This can be explained by the strong GSH-depletion after 1 h by t-BHP and diamide, which contrasted with a weak GSH-depletion by H2O2 after the same time period. 4. The three test chemicals increased the endogenous GSH content after 24 h. t-BHP and H2O2, but not diamide, increased the total GSH transferase (GST) activity. Several alterations of the GST subunits were observed. Most striking was the increase of class alpha GST subunits, also for diamide. 5. Since H2O2 and t-BHP are ozone metabolites thought to be responsible for the therapeutic effects of well-dosed ozone, the results show that Fa32 cells can be used as a valuable alternative model system for studying the effects encountered in human ozone therapy.
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PMID:Glutathione protection against hydrogen peroxide, tert-butyl hydroperoxide and diamide cytotoxicity in rat hepatoma-derived Fa32 cells. 1055 15

We describe a biphasic action of nitric oxide (NO) in its effects on oxidative killing of isolated cells: low concentrations protect against oxidative killing, while higher doses enhance killing, and these two effects occur by distinct mechanisms. While low doses of NO (from (Z)-1-[N-(3-ammonio propyl)-N-(n-propyl)-amino]-diazen-1-ium-1,2(2) diolate [PAPA/NO] or S-nitroso-N-acetyl-L-penicillamine [SNAP] prevent killing of rat hepatocytes by t-butylhydroperoxide (tBH), further increasing doses result in increased killing. Similar effects occur with rat hepatoma cells treated with PAPA/NO and tBH or H2O2. Increased killing with higher concentrations of NO donor is due to both NO and tBH, because NO donor alone is without effect. Glutathione (GSH) is not involved in either of these actions. Based on measurements of thiobarbituric acid-reactive substances (TBARS) and effects of lipid radical scavenger (DPPD) and deferoxamine, the protective effect, but not the enhancing effect, involves peroxidative chemistry. Fructose has no effect on tBH killing alone but provides substantial protection against killing by higher concentrations of NO plus tBH, suggesting that the enhancing effect involves mitochondrial dysfunction. Hepatocytes, when stimulated to produce NO endogenously, become resistant to tBH killing, indicative of the presence of an NO-triggered antioxidant defensive mechanism. The finding that the protective effects of low concentrations of NO and the harmful effects of high concentrations of NO are fundamentally different in nature suggest that therapeutic interventions could be designed, which selectively prevent its pro-oxidant activity at high concentrations, thus converting NO from a "Janus-faced" modulator of oxidant injury into a "pure" protectant.
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PMID:Cellular antioxidant and pro-oxidant actions of nitric oxide. 1064 30

Ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, is a synthetic seleno-organic compound with antioxidant capability. In the present study, we systematically examined the ability of ebselen to induce apoptosis in a human hepatoma cell line, HepG(2). Ebselen-induced apoptosis was evaluated by (i) TdT-mediated dUTP nick end labeling assay; (ii) analysis of sub-G1 cells; (iii) cell morphology, including cell size and granularity examination; and (iv) DNA gel electrophoresis. The results showed that ebselen was able to induce typical apoptosis in HepG(2) cells in a dose- and time-dependent manner. In order to explore the possible mechanisms involved in ebselen-induced apoptosis, the effect of ebselen on intracellular thiol concentrations including reduced glutathione (GSH) and protein thiols and the effect of N-acetylcysteine (NAC) and buthionine sulfoximine (BSO) pretreatment on ebselen-induced apoptosis were investigated. It was found that (i) ebselen rapidly depleted intracellular GSH and protein thiols, moreover, the depletion preceded the occurrence of apoptosis; (ii) NAC, a precursor of intracellular GSH synthesis, significantly alleviated ebselen-induced apoptosis; and (iii) BSO, a specific inhibitor of intracellular GSH synthesis, augmented ebselen-induced apoptosis significantly. Taken together, the present study demonstrates that ebselen is able to induce apoptosis in HepG(2) cells, most probably through rapid depletion of intracellular thiols.
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PMID:Ebselen induces apoptosis in HepG(2) cells through rapid depletion of intracellular thiols. 1066 92

Glutathione S-transferases, enzymes that defend cells against damage mediated by oxidant and electrophilic carcinogens, may be critical determinants of cancer pathogenesis. We report here that the pathogenesis of hepatocellular carcinoma (HCC), one of the most common cancers in the world, frequently involves an accumulation of somatic <CpG island> DNA methylation changes at GSTP1, the gene encoding the pi-class glutathione S-transferase. For our study, Hep3B HCC cells and a cohort of 20 HCC tissue specimens were subjected to analysis for GSTP1 expression and for somatic GSTP1 alterations. GSTP1 <CpG island> DNA hypermethylation in HCC DNA was assessed by Southern blot analysis, via a polymerase chain reaction (PCR) assay, and by using a genomic sequencing approach. Hep3B HCC cells failed to express GSTP1 mRNA or GSTP1 polypeptides. Similarly, HCC cells in 19 of 20 HCC cases were devoid of GSTP1 polypeptides. By Southern blot analysis, DNA from Hep3B HCC cells displayed abnormal GSTP1 <CpG island> hypermethylation. Treatment of Hep3B HCC cells in vitro with the DNA methyltransferase inhibitor 5-aza-deoxycytidine both reversed GSTP1 <CpG island> DNA hypermethylation and restored GSTP1 expression. Using a PCR assay, somatic GSTP1 <CpG island> DNA hypermethylation was also detected in HCC DNA from 17 of 20 HCC cases. Genomic sequencing analyses, undertaken to map 5-methyldeoxycytidine nucleotides located at the GSTP1 transcriptional regulatory region, frequently detected somatic DNA hypermethylation near the gene promoter in HCC DNA. The data indicate that GSTP1 <CpG island> DNA hypermethylation changes appear frequently in human HCC. In addition, the data raise the possibility that somatic GSTP1 inactivation, via <CpG island> hypermethylation, may contribute to the pathogenesis of HCC.
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PMID:GSTP1 CpG island DNA hypermethylation in hepatocellular carcinomas. 1071 33

Induction of CYP2E1 (cytochrome P450 2E1) by ethanol appears to be one of the central pathways by which ethanol generates a state of oxidative stress. CYP2E1 is a loosely coupled enzyme; formation of reactive oxygen species occurs even in the absence of added substrate. GSH is critical for preserving the proper cellular redox balance and for its role as a cellular protectant. Since cells must maintain optimal GSH levels to cope with a variety of stresses, the goal of this study was to characterize the GSH homeostasis in human hepatocarcinoma cells (HepG2) that overexpress CYP2E1. This study was prompted by the finding that toxicity in CYP2E1-overexpressing cells was markedly enhanced after GSH depletion by buthionine sulfoximine treatment. CYP2E1-overexpressing cells showed a 40-50% increase in intracellular H(2)O(2); a 30% increase in total GSH levels; a 50% increase in the GSH synthesis rate; and a 2-fold increase in gamma-glutamylcysteine synthetase heavy subunit (GCS-HS) mRNA, the rate-limiting enzyme in GSH synthesis. This GCS-HS mRNA increase was due to increased synthesis since nuclear run-on assays showed increased transcription in CYP2E1-expressing cells, and the GCS-HS mRNA decay after actinomycin D treatment was similar in CYP2E1-expressing cells and empty vector-transfected cells. The facts that treatment with GSH ethyl ester almost completely prevented the increase in GCS-HS mRNA and decreased H(2)O(2) levels and that transient transfection with catalase (but not manganese-superoxide dismutase) produced a decrease in GCS-HS mRNA only in CYP2E1-expressing cells suggest a possible role for H(2)O(2) in the induction of GCS-HS gene transcription. In contrast to results with HepG2 cells expressing CYP2E1, no increase in GCS-HS mRNA was found with a HepG2 cell line engineered to express human cytochrome P450 3A4. In summary, CYP2E1 overexpression in HepG2 cells up-regulates the levels of reduced GSH by transcriptional activation of GCS-HS; this may reflect an adaptive mechanism to remove CYP2E1-derived oxidants such as H(2)O(2).
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PMID:CYP2E1 overexpression in HepG2 cells induces glutathione synthesis by transcriptional activation of gamma-glutamylcysteine synthetase. 1074 80

Tissue slices are a useful biological system for lipid peroxidation studies but their use for DNA damage studies is not well characterized. Hence, the present study investigates DNA damage in rat liver slices, in comparison with isolated rat liver nuclei and HepG2 human hepatoma cells, incubated with ferric nitrilotriacetate (Fe(III)-NTA), bromotrichloromethane (BrCCl(3)), bromobenzene (BrB) or 2-nitropropane (2-NP) at 37 degrees C for 2 hr. DNA damage was measured in slices, cells or nuclei after centrifugation as formation of as 8-hydroxy-2'-deoxyguanosine (8-OH-dGu) and loss of double-stranded (dsDNA) due to strand breakage using a fluorometric analysis of DNA unwinding (FADU). Lipid peroxidation was measured as thiobarbituric acid-reactive substances (TBARS) released into the medium. The results show that in liver slices and isolated nuclei, Fe/NTA (1 mM/4 mM) induced high levels of TBARS but low levels of 8-OH-dGu, whereas the oxidant induced low levels of TBARS and no formation of 8-OH-dGu in HepG2 cells. In all three systems, inclusion of ascorbate caused dose-dependent formation of 8-OH-dGu, and the levels were similar between liver slices and HepG2 cells but were far higher in isolated nuclei. In liver slices the FADU assay was not applicable due to limited solubilization of DNA from the slice, whereas the assay detected significant loss of dsDNA in HepG2 cells and slight loss in isolated nuclei induced by Fe/NTA with or without ascorbate. Liver slices incubated with 1 mm BrCCl(3), BrB or 2-NP had elevated TBARS but had little or no formation of 8-OH-dGu; none of these oxidants induced lipid peroxidation or DNA damage in HepG2 cells. When liver slices obtained from rats injected with diethylmaleate (to deplete GSH) were incubated with BrCCl(3), BrB or 2-NP, levels of TBARS and 8-OH-dGu increased markedly. Similarly, HepG2 cells with decreased GSH showed marked elevation of TBARS and loss of dsDNA induced by these oxidants, although no formation of 8-OH-dGu was detected. The present study demonstrates the usefulness and limitations of liver slices for DNA damage studies and the importance of cellular GSH in the protection of DNA against environmental toxicants.
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PMID:Use of rat liver slices for the study of oxidative DNA damage in comparison with isolated rat liver nuclei and HepG2 human hepatoma cells. 1076 31


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