白藜芦醇对人肝癌细胞系HepG2抑制作用的探讨

目的:观察白藜芦醇(Res)对体外培养的人肝癌细胞系HepG2生长增殖的影响.方法:采用MTT法、流式细胞仪分析Res对肝癌细胞系HepG2细胞生长的影响及其细胞周期的变化,并且检测端粒酶的活性.结果:Res对肝癌细胞系HepG2的增殖具有抑制作用,IC50为5.91mg/L,流式细胞仪显示,Res能引起肝癌细胞系HepG2细胞的S期阻滞,Res也能显著地抑制端粒酶的活性.结论:Res通过改变肝癌细胞系HepG2细胞的细胞周期分布来抑制人肝癌细胞系HepG2细胞的生长.     

Genotoxicity of acrylamide in human hepatoma G2 (HepG2) cells

The recent finding that acrylamide (AA), a carcinogen in animal experiments and a probable human carcinogen, is formed in foods during cooking raises human health concerns. The relevance of dietary exposure for humans is still under debate. The purpose of the study was to evaluate the possible genotoxicity of acrylamide in human hepatoma G2 (HepG2) cells, a cell line of great relevance to detect genotoxic/antigenotoxic substances, using single cell gel electrophoresis (SCGE) assay and micronucleus test (MNT). In order to clarify the underlying mechanism(s) we evaluated the intracellular generation of reactive oxygen species (ROS) and the level of oxidative DNA damage by immunocytochemical analysis of 8-hydroxydeoxyguanosine (8-OHdG). The involvement of glutathione (GSH) in the AA-induced oxidative stress was examined through treatment with buthionine sulfoximine (BSO) to deplete GSH. The results indicate that AA caused DNA strand breaks and increase in frequency of MN in HepG2 cells in a dose-dependent manner. The possible mechanism underlies the increased levels of ROS, depletion of GSH and increase of 8-OHdG formation in HepG2 cells treated with AA. We conclude that AA exerts genotoxic effects in HepG2 cells, probably through oxidative DNA damage induced by intracellular ROS and depletion of GSH.     

Drug toxicity mechanisms in human hepatoma HepG2 cells: cyclosporin A and tamoxifen

1. Mechanisms of drug toxicity operating in human HepG2 hepatoma cells have been assessed using cyclosporin A (CsA) and tamoxifen as examples.

2. Either 150 μM CsA or 50 μM tamoxifen caused approximately 50% loss of HepG2 cell viability. α-Tocopherol (32 μM) almost completely prevented cell death due to either CsA or tamoxifen. Tamoxifen stimulated malondialdehyde formation. The toxicity of CsA but not tamoxifen was increased by the glutathione synthesis inhibitor, buthionine-S.R-sulphoximine, and decreased by the glutathione precursor, L-cysteine. Thus, while both CsA and tamoxifen toxicities involved lipid peroxidation, reduced glutathione (or sulphydryl groups) protected against CsA but not tamoxifen.

3. CsA was metabolized to M1 and/or M17 in HepG2 cells. The effects of the cytochrome P450 inhibitors, ketoconazole and metyrapone, indicated that P450 played a role in the toxicity of CsA but not tamoxifen. The effects of superoxide dismutase and cytochrome c indicated that tamoxifen toxicity involved superoxide formation.

4. These results show that several oxidative mechanisms of drug toxicity operate in HepG2 cells.     

大蒜素联合替加氟对人HepG2肝癌细胞增殖的影响

目的观察大蒜素联合替加氟对人HepG2肝癌细胞增殖的影响。方法体外培养人HepG2肝癌细胞,细胞分为4组:对照组、大蒜素组、替加氟组和联合组,于培养24和48 h后,MTT法检测大蒜素、替加氟及两药联合对人HepG2肝癌细胞增殖的影响。结果大蒜素组和替加氟组的细胞增殖抑制率均明显高于对照组(P<0.05),联合组细胞增殖抑制率明显强于单独用药组(P<0.05)。结论大蒜素联合替加氟能够显著抑制人HepG2肝癌细胞的增殖。     

Mitochondrial aquaporin-8 knockdown in human hepatoma HepG2 cells causes ROS-induced mitochondrial depolarization and loss of viability

Human aquaporin-8 (AQP8) channels facilitate the diffusional transport of H₂O₂ across membranes. Since AQP8 is expressed in hepatic inner mitochondrial membranes, we studied whether mitochondrial AQP8 (mtAQP8) knockdown in human hepatoma HepG2 cells impairs mitochondrial H₂O₂ release, which may lead to organelle dysfunction and cell death. We confirmed AQP8 expression in HepG2 inner mitochondrial membranes and found that 72 h after cell transfection with siRNAs targeting two different regions of the human AQP8 molecule, mtAQP8 protein specifically decreased by around 60% (p < 0.05). Studies in isolated mtAQP8-knockdown mitochondria showed that H₂O₂ release, assessed by Amplex Red, was reduced by about 45% (p < 0.05), an effect not observed in digitonin-permeabilized mitochondria. mtAQP8-knockdown cells showed an increase in mitochondrial ROS, assessed by dichlorodihydrofluorescein diacetate (+ 120%, p < 0.05) and loss of mitochondrial membrane potential (− 80%, p < 0.05), assessed by tetramethylrhodamine-coupled quantitative fluorescence microscopy. The mitochondria-targeted antioxidant MitoTempol prevented ROS accumulation and dissipation of mitochondrial membrane potential. Cyclosporin A, a mitochondrial permeability transition pore blocker, also abolished the mtAQP8 knockdown-induced mitochondrial depolarization. Besides, the loss of viability in mtAQP8 knockdown cells verified by MTT assay, LDH leakage, and trypan blue exclusion test could be prevented by cyclosporin A. Our data on human hepatoma HepG2 cells suggest that mtAQP8 facilitates mitochondrial H₂O₂ release and that its defective expression causes ROS-induced mitochondrial depolarization via the mitochondrial permeability transition mechanism, and cell death.     

Rho激酶抑制剂Y-27632对人肝癌HepG2细胞增殖的抑制作用

目的 研究Rho激酶特异性抑制剂Y-27632对人肝癌HepG2细胞增殖的抑制作用.方法 体外培养人肝癌HepG2细胞,分为正常对照组(C组)以及不同浓度Y-27632 2.5、5、10、25、50μmol/L处理组(分别为A1组、A2组、A3组、A4组、A5组).镜下观察HepG2细胞的生长变化,MTT法检测各组HepG2细胞增殖情况.结果 在Y-27632作用下,HepG2细胞失去原有“铺路石”样排列,细胞间连接减少,细胞间隙增大,细胞胞体皱缩、变圆,细胞黏附性下降,有倾向凋亡趋势.与C组相比,不同浓度Y-27632作用后的HepG2细胞光密度值减少,细胞活力相对下降,且呈浓度依赖性(P＜0.05).结论 Rho激酶抑制剂Y-27632能有效抑制人肝癌HepG2细胞增殖.     

吴茱萸碱对人肝癌细胞HepG2的生长抑制及诱导凋亡作用

目的探讨吴茱萸碱对人肝癌细胞HepG2的生长抑制、诱导凋亡和对细胞周期的影响。方法体外试验MIT法测存活率,DAPI染色观察细胞凋亡形态,流式细胞术、彗星电泳技术分析药物对DNA作用。结果吴茱萸碱能抑制人肝癌细胞HepG2的生长。用64、16、4、1、0.25μmol.L-1浓度的吴茱萸碱处理HepG2细胞72 h的抑制率分别为74.0%、69.0%、60.5%、44.0%、16.4%。DAPI染色后吴茱萸碱组癌细胞均表现出较为典型的细胞凋亡特征。流式细胞仪检测1μmol.L-1吴茱萸碱作用24和36 h出现亚二倍体凋亡峰,细胞周期阻滞于G2/M期。凋亡率对照组为4%,1μmol.L-1吴茱萸碱作用12、24、36 h的凋亡率分别为4.4%、18.0%、30.3%。彗星电泳显示1μmol.L-1吴茱萸碱作用24和48 h后,细胞后面形成长的拖尾,平均光密度值较阴性对照组降低,彗星尾距较阴性对照组增加,且二者的改变与作用时间相关。结论吴茱萸碱能抑制人肝癌细胞HepG2的生长及诱导其凋亡。     

Apoptotic effects of dichloro stearic and dichloro myristic acid in human hepatoma cells (HepG2)

Chlorinated fatty acids represent the major fraction of extractable organically bound chlorine in fish. After dietary intake such fatty acids may accumulate in adipose tissue, and even be transferred from mother to child via breast milk. We have previously reported that 9,10-dichloro stearic acid and 5,6-dichloro myristic acid inhibited cell growth. The aim of the present work was to investigate whether the growth inhibitory effect of these modified fatty acids might involve apoptosis. Human hepatoma cells (HepG2) were cultured for 4 days before addition of chlorinated fatty acids, and then cultured for another day before harvested. Morphological analysis was mainly done by light microscopy. In addition, fluorescence microscopy and electrophoretic analysis of DNA were carried out. The effect of 0.3 and 0.6 mmol/l was studied. Both chlorinated fatty acids seemed to cause a concentration-dependent increase in the relative abundance of pycnotic and broken nuclei, as well as nuclear fragments, with the strongest effect of dichloro stearic acid. Apoptosis by the chlorinated fatty acids was however less than that of docosahexaenoic acid, a known apoptosis effector. In conclusion, chlorinated fatty acids seem to possess the ability to cause apoptosis.     

gamma-Glutamyl transpeptidase and l-cysteine regulate methylmercury uptake by HepG2 cells, a human hepatoma cell line

Mechanisms of methylmercury (MeHg) and inorganic mercury (Hg) uptake were examined in HepG2 cells, a human hepatoma-derived cell line. MeHg uptake was faster when it was present as the l-cysteine complex, as compared to the glutathione (GSH), CysGly, gamma-GluCys, d-cysteine, N-acetylcysteine, l-penicillamine, or albumin complexes. Uptake of MeHg-l-cysteine was independent of Na(+), stereoselective, and was inhibited by the amino acid transport system l substrates l-leucine, l-valine, and l-phenylalanine (5 mM). Moreover, [(3)H]l-leucine uptake was inhibited by MeHg-l-cysteine, suggesting that MeHg-l-cysteine is transported into HepG2 cells by an l-type amino acid carrier. Uptake of MeHg as the GSH complex (MeHg-SG) was dependent on the extracellular GSH concentration, and was diminished when cellular gamma-glutamyl transpeptidase activity was inhibited. Inorganic mercury uptake was slower than that of MeHg, but was also sensitive to the type of thiol ligand present. These findings demonstrate that mercury uptake by HepG2 cells is dependent on the chemical structure of the mercury compound, the thiol ligand, and the activity of gamma-glutamyl transpeptidase. gamma-Glutamyl transpeptidase appears to play a key role in the disposition of MeHg-SG by facilitating the formation of MeHg-l-cysteine, which is readily transported into the cells on an amino acid-type carrier.     

大黄素诱导人肝癌HepG2细胞线粒体凋亡作用研究

目的 研究大黄素对人肝癌HepG2细胞线粒体凋亡的影响。方法 培养人肝癌HepG2细胞,与5、10、20、40、60、80、100 μmol/L的大黄素作用24、48 h,MTS法检测细胞增殖;40、80、160 μmol/L大黄素作用HepG2细胞24 h,AO/EB双荧光染色法观察细胞凋亡的形态学改变;Annexin V/PI染色经流式细胞仪检测细胞凋亡;分光光度法检测caspase 3活性;ATP试剂盒检测细胞ATP含量,不同荧光探针加载后流式细胞仪测定大黄素对HepG2细胞内活性氧（ROS）含量、Ca²⁺浓度、线粒体膜电位（MMP）变化的影响。结果 大黄素抑制HepG2细胞生长,且呈时间、浓度相关性,半数抑制浓度（IC₅₀）为（77.42±1.25）μmol/L;随着大黄素浓度升高,AO/EB双染观察到细胞核浓缩、碎裂、凋亡小体等凋亡形态;与对照组比较,大黄素40、80、160 μmol/L作用于HepG2细胞24 h后细胞凋亡率显著增加,caspase 3活性显著增强,ROS水平、Ca²⁺浓度明显增加（P<0.05、0.01、0.001）,80、160 μmol/L组线粒体膜电位明显降低,ATP含量显著下降（P<0.05、0.01、0.001）。结论 大黄素造成HepG2细胞内ROS堆积,ATP合成功能障碍,线粒体膜电位明显下降,进而诱导线粒体通透转运孔开放,导致钙离子和细胞色素C外流,活化caspase蛋白家族,导致细胞凋亡。     

3-Nitrobenzanthrone (3-NBA) induced micronucleus formation and DNA damage in human hepatoma (HepG2) cells

3-Nitrobenzanthrone (3-NBA), identified in diesel exhaust and in airborne particulate matter, is a potent mutagen in Salmonella, induces micronuclei formation in mice and in human cells and DNA adducts in rats. In the present study, we investigated the genotoxic potency of 3-NBA in human HepG2 cells using the micronucleus (MN) assay and the single cell gel electrophoresis (SCGE). 3-NBA caused a genotoxic effect at concentrations > or =12 nM in both assays. In the micronucleus assay, we found 98.7+/-10.3 MN/1000 BNC at a concentration of 100 nM 3-NBA in comparison to 27.3+/-0.6 MN/1000 BNC with the negative control. At the same concentration, the DNA-migration (SCGE) showed an Olive tail moment (OTM) of 2.7+/-0.45 and %DNA in the tail of 8.28+/-0.76; OTM and %DNA in the tail of cells treated with the negative control were 0.73+/-0.08 and 2.81+/-0.30, respectively. The results are discussed under consideration of former studies.     

DNA damage and metallothionein synthesis in human hepatoma cells (HepG2) exposed to cadmium.

Cadmium is an important heavy metal environmental toxicant, which is classified as a human carcinogen. The comet assay was used to evaluate the levels of DNA damage in a metabolically competent HepG2 cell line after treatment with low, non-cytotoxic and physiologically relevant concentrations of cadmium, alone and in combination with the dietary mutagen 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) and with the environmental mutagen benzo[a]pyrene (B(a)P). After exposure of the cells to 10, 100 and 1000 nM CdCl(2), a dose- and time-dependent increase of DNA damage was detected. Maximal damage was found after 12 h of treatment, but declined with further incubation with CdCl(2). The increased synthesis of metallothioneins on exposure to CdCl(2) up to 12 h suggests that they are responsible for the adaptation of HepG2 cells to the DNA damaging effects of CdCl(2). Co-treatment of the cells with CdCl(2) (10-1000 nM) and IQ (300 microM) induced a dose-dependent increase of DNA damage compared to cells treated with IQ alone. Co-genotoxic activity was also observed by increased formation of micronuclei in cells exposed to IQ and 1000 nM CdCl(2); at this concentration, CdCl(2) alone also induced micronuclei in HepG2 cells. Our results support the hypothesis that direct and indirect mechanisms are involved in cadmium-induced DNA damage.     

Microcystin-LR induces oxidative DNA damage in human hepatoma cell line HepG2.

Microcystins are naturally occurring hepatotoxins produced by strains of Microcystis aeruginosa. They are involved in promoting primary liver tumours and a previous study showed that they might also be tumour initiators. In this study we demonstrate that microcystin-LR (MCLR) at doses that were not cytotoxic (0.01-1 microg/ml), induced dose and time dependent DNA strand breaks in human hepatoma cell line HepG2. These DNA strand breaks were transient, reaching a maximum level after 4h of exposure and declining with further exposure. In the presence of the DNA repair inhibitors cytosine arabinoside (AraC) and hydroxyurea (HU), together with MCLR, DNA strand breaks accumulated after prolonged exposure. These results suggest that DNA strand breaks are intermediates, produced during the cellular repair of MCLR induced DNA damage. Digestion of DNA with purified, oxidative DNA damage specific enyzmes, endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg) markedly increased DNA strand breaks in MCLR treated cells, providing evidence that a substantial portion of the MCLR induced DNA strand breaks originate from excision of oxidative DNA adducts. A hydroxyl radical scavenger (DMSO) significantly reduced MCLR induced DNA damage. From these results we conclude that MCLR induces formation of reactive oxygen species that cause DNA damage, and that MCLR may act as an initiator of liver cancer.     

Influence of Emblica officinalis aqueous extract on growth and antioxidant defense system of human hepatoma cell line (HepG2)

Context: Amla [Emblica officinalis Gaertn. (Euphorbiaceae)], a major constituent of several herbal formulations, is a well-known hepatoprotectant. Despite its extensive use, mechanistic understanding of its antioxidant action is rather limited.

Objective: In the current study, we investigated the effects of E. officinalis extracts (from dried fruits) on cellular oxidative state using a hepatocyte cell line (HepG2). We hypothesize that E. officinalis aqueous extracts have potency to modulate basal oxidative markers and enhance endogenous antioxidant defenses.

Materials and methods: Cells were incubated with aqueous extracts of E. officinalis (1–100 μg/ml) for varied time points (4–24?h) and biochemical markers of oxidative stress were determined in cell lysate.

Discussion: Aqueous extracts of E. officinalis at 100 μg/ml can significantly modulate the basal levels of oxidative markers and enhance antioxidant defenses of the cells.

Conclusions: Our findings clearly indicate the propensity of E. officinalis aqueous extracts to improve endogenous antioxidant defenses in HepG2 cells. Although further studies are required to assess their efficacy under experimentally induced oxidative, our data suggest that the hepatoprotective effects of E. officinalis reported earlier may be largely due to its potential to enhance the antioxidant defenses in vivo.

Results: Because E. officinalis up to 100 μg/ml concentrations had no effect on cell viability; it was considered noncytotoxic. Incubation with E. officinalis for 24?h resulted in significant diminution in the levels of lipid hydroperoxide (18–42%) and reactive oxygen species (11–29%). Furthermore; E. officinalis increased the levels of glutathione (GSH; 18–32%); antioxidant capacity (19–31%); and activities of antioxidant enzymes (superoxide dismutase; 25–41%; catalase; 39–50%; GSH peroxidase; 20–35%; GSH reductase; 26–35%; and GSH S-transferase; 12–30%).     

川楝素对人肝癌细胞株HepG2生物学行为的影响

目的 观察川楝素对人肝癌细胞株HepG2增殖和凋亡的影响,并研究其诱导凋亡的机制.方法 取人肝癌HepG2细胞株培养后,随机分为对照组(不添加任何药物)、观察组(加川楝素80 mmol/ml),培养细胞24、48、72 h后,酶标仪测定人肝癌HepG2细胞增殖抑制率;流式细胞仪检测人肝癌HepG2细胞周期和凋亡率.结果 两组对肝癌HepG2细胞增殖抑制率差异有统计学意义(x2=5.33,P＜0.05);两组S期、G0/G1期、M/G2期的细胞比率(t=6.31、6.26、6.56,均P＜0.05)、细胞凋亡率差异有统计学意义(x2=6.15,P＜0.05).结论 川楝素可明显抑制人肝癌细胞HepG2的恶性增殖,并诱导肿瘤细胞凋亡.     

褪黑素对肝癌细胞系HepG2的增殖抑制作用及其与G蛋白-cAMP信号途径的关系

目的研究褪黑素(melatonin,MT)对肝癌细胞系HepG2细胞的增殖抑制作用以及其对G蛋白-cAMP通路的影响。方法采用MTT法检测MT对HepG2细胞生长的影响,放免法检测细胞内cAMP水平,Westernblot法检测抑制型G蛋白α1(Gαi1)、抑制型G蛋白α2(Gαi2)、抑制型G蛋白α3(Gαi3)、刺激型G蛋白(Gαs)表达水平。结果MTT检测结果表明,MT在10-8～10-5mol.L-1的浓度范围内,72h共培养后,可有效抑制HepG2细胞增殖,且呈一定的时间浓度依赖关系。为进一步研究MT细胞增殖抑制作用与G蛋白-cAMP信号通路的关系,检测浓度为10-5mol.L-1的MT作用HepG2细胞后0、15、30、45、60、90、120min后Gαi1、Gαi2、Gαi3和Gαs和细胞内cAMP水平变化,结果发现MT作用HepG2细胞30min后可明显下调Gαi1、Gαi2、Gαi3的表达水平,但对Gαs表达无明显影响,同时发现MT处理后cAMP水平有下降的趋势,但是没有统计学意义。结论MT呈时间浓度依赖性的抑制体外培养的HepG2细胞生长,其机制可能与影响G蛋白-cAMP信号通路有关。