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Human HepG2 Cells (human + hepg2_cell)
Selected AbstractsAtorvastatin prevents carbohydrate response element binding protein activation in the fructose-fed rat by activating protein kinase A,HEPATOLOGY, Issue 1 2009Ricardo Rodríguez-Calvo High fructose intake contributes to the overall epidemic of obesity and metabolic disease. Here we examined whether atorvastatin treatment blocks the activation of the carbohydrate response element binding protein (ChREBP) in the fructose-fed rat. Fructose feeding increased blood pressure (21%, P < 0.05), plasma free fatty acids (59%, P < 0.01), and plasma triglyceride levels (129%, P < 0.001) compared with control rats fed standard chow. These increases were prevented by atorvastatin. Rats fed the fructose-rich diet showed enhanced hepatic messenger RNA (mRNA) levels of glycerol-3-phosphate acyltransferase (Gpat1) (1.45-fold induction, P < 0.05), which is the rate-limiting enzyme for the synthesis of triglycerides, and liver triglyceride content (2.35-fold induction, P < 0.001). Drug treatment inhibited the induction of Gpat1 and increased the expression of liver-type carnitine palmitoyltransferase 1 (L-Cpt-1) (128%, P < 0.01). These observations indicate that atorvastatin diverts fatty acids from triglyceride synthesis to fatty acid oxidation, which is consistent with the reduction in liver triglyceride levels (28%, P < 0.01) observed after atorvastatin treatment. The expression of Gpat1 is regulated by ChREBP and sterol regulatory element binding protein-1c (SREBP-1c). Atorvastatin treatment prevented fructose-induced ChREBP translocation and the increase in ChREBP DNA-binding activity while reducing SREBP-1c DNA-binding activity. Statin treatment increased phospho-protein kinase A (PKA), which promotes nuclear exclusion of ChREBP and reduces its DNA-binding activity. Human HepG2 cells exposed to fructose showed enhanced ChREBP DNA-binding activity, which was not observed in the presence of atorvastatin. Furthermore, atorvastatin treatment increased the CPT-I mRNA levels in these cells. Interestingly, both effects of this drug were abolished in the presence of the PKA inhibitor H89. Conclusion: These findings indicate that atorvastatin inhibits fructose-induced ChREBP activity and increases CPT-I expression by activating PKA. (HEPATOLOGY > 2009;49:106-115.) [source] Inhibition of microsomal triglyceride transfer protein expression and atherogenic risk factor apolipoprotein B100 secretion by tanshinone IIA in HepG2 cellsPHYTOTHERAPY RESEARCH, Issue 12 2008Yun-Jeong Kang Abstract Salvia miltiorrhiza Bunge is known to be effective for the treatment of cardiovascular diseases. Here, we have isolated tanshinone IIA (T-IIA) from S. miltiorrhiza Bunge. The aim of this study is to address the mechanisms where apolipoprotein B-100 (ApoB) regulation is associated with T-IIA, since T-IIA regulates the lipoprotein metabolism in liver cells. Human HepG2 cells treated with T-IIA for 24 h exerted a dose-dependent inhibitory effect on ApoB secretion together with triglyceride. However, another secretory protein, albumin, was unaffected by T-IIA treatment, indicating that the effect of T-IIA is specific for ApoB secretion. T-IIA decreased the transcription level of microsomal triglyceride transfer protein gene, suggesting that lipoprotein assembly is likely to be involved in the inhibited ApoB secretion. Interestingly, T-IIA inhibited ApoB secretion via a proteasome-dependent pathway. Our results suggest that T-IIA is an influential inhibitor of ApoB secretion and triglyceride secretion in liver cells. Copyright © 2008 John Wiley & Sons, Ltd. [source] Three structurally homologous isothiocyanates exert "Janus" characteristics in human HepG2 cellsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2009Evelyn Lamy Abstract In this study, we used the single cell gel electrophoresis (SCGE) assay and the micronucleus (MN) test to investigate the DNA damaging effects and the antigenotoxic potencies of three structurally related ITCs in human HepG2 cells. The results show that all three ITCs possess the characteristic of a "Janus" compound, i.e., they exert both significant genotoxicity and antigenotoxicity, depending on the concentrations used in the test systems applied. Regression line analysis of the results derived by SCGE analysis showed genotoxic potency of the ITCs in the following order: 3-methylthiopropyl ITC (MTPITC) > 4-methylthiobutyl ITC (MTBITC) > 5-methylthiopentyl ITC (MTPeITC); however, this order in genotoxic potency was not confirmed by MN analysis. Additionally, the MN test showed significant mutagenicity of the test substances at higher concentrations when compared with the SCGE assay. Twenty-four hour-treatment of the cells with the ITCs, followed by a 1-hr recovery period, showed significant DNA repair in the SCGE assay at a concentration ,10 ,M MTPITC, ,3 ,M MTBITC, and ,0.1 ,M MTPeITC, respectively. In antigenotoxicity studies, the most effective concentration of MTPITC and MTPeITC toward B(a)P-induced DNA damage was 0.1 ,M in both test systems. MTBITC suppressed MN formation in B(a)P-treated cells to the background level at a concentration of 1 ,M. The ambivalent character of the ITCs under studymust be further clarified, especially in the possiblecontext of high dose therapeutic applications. Environ. Mol. Mutagen. 2009. © 2009 Wiley-Liss, Inc. [source] Structural requirements for the apical sorting of human multidrug resistance protein 2 (ABCC2)FEBS JOURNAL, Issue 7 2002Anne T. Nies The human multidrug resistance protein 2 (MRP2, symbol ABCC2) is a polytopic membrane glycoprotein of 1545 amino acids which exports anionic conjugates across the apical membrane of polarized cells. A chimeric protein composed of C-proximal MRP2 and N-proximal MRP1 localized to the apical membrane of polarized Madin,Darby canine kidney cells (MDCKII) indicating involvement of the carboxy-proximal part of human MRP2 in apical sorting. When compared to other MRP family members, MRP2 has a seven-amino-acid extension at its C-terminus with the last three amino acids (TKF) comprising a PDZ-interacting motif. In order to analyze whether this extension is required for apical sorting of MRP2, we generated MRP2 constructs mutated and stepwise truncated at their C-termini. These constructs were fused via their N-termini to green fluorescent protein (GFP) and were transiently transfected into polarized, liver-derived human HepG2 cells. Quantitative analysis showed that full-length GFP,MRP2 was localized to the apical membrane in 73% of transfected, polarized cells, whereas it remained on intracellular membranes in 27% of cells. Removal of the C-terminal TKF peptide and stepwise deletion of up to 11 amino acids did not change this predominant apical distribution. However, apical localization was largely impaired when GFP,MRP2 was C-terminally truncated by 15 or more amino acids. Thus, neither the PDZ-interacting TKF motif nor the full seven-amino-acid extension were necessary for apical sorting of MRP2. Instead, our data indicate that a deletion of at least 15 C-terminal amino acids impairs the localization of MRP2 to the apical membrane of polarized cells. [source] Hepatocytes as cytotoxic effector cells can induce cell death by CD95 ligand-mediated pathway,HEPATOLOGY, Issue 6 2006Clifford S. Guy The liver plays an increasingly recognized role in the host's immune responses. The direct contribution of hepatocytes as effector cells to local immunity, pathogen containment, and liver disease is not determined. This in vitro study examined whether hepatocytes can eliminate other cells via a CD95 ligand (CD95L or FasL)/CD95 (Fas),mediated mechanism and whether this cytotoxic activity can be modulated by cytokines such as interferon gamma (IFN-,) or tumor necrosis factor alpha (TNF-,). We have found that normal woodchuck and human hepatocytes, both cultured and primary freshly isolated, as well as human HepG2 cells, intrinsically transcribe not only CD95 but also CD95L when examined by reverse transcription-polymerase chain reaction (RT-PCR) assays. The functional competence of CD95L, which was detectable in hepatocytes and HepG2 cells by Western blotting, was confirmed in bioassays by induction of apoptosis of CD95-bearing P815 and LS102.9 cell targets and validated by inhibition of the cell killing with CD95 antagonistic antibody or with a general caspase inhibitor. Furthermore, exposure of cultured hepatocytes to IFN-, or their stable transfection with IFN-, cDNA or TNF-, cDNA increased hepatocyte CD95L/CD95,mediated cell killing. In conclusion, hepatocytes express both CD95L and CD95 and they can induce death of other cells by a CD95L-dependent mechanism. IFN-, and, to a lesser extent, TNF-, can enhance hepatocyte CD95L-mediated cytotoxicity. This suggests that the local cytokine environment may modulate the hepatocyte contribution to liver immunity. (HEPATOLOGY 2006;43:1231,1240.) [source] Epigallocatechin gallate (EGCG) attenuates high glucose-induced insulin signaling blockade in human hepG2 hepatoma cellsMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 8 2008Chih-Li Lin Abstract Insulin resistance is the primary characteristic of type 2 diabetes which as a result of insulin signaling defects. It has been suggested that the tea polyphenol (,)-epigallocatechin-3-gallate (EGCG) displays some antidiabetic effects, but the mechanism for EGCG insulin-enhancing effects is incompletely understood. In the present study, the investigations of EGCG on insulin signaling are performed in insulin-responsive human HepG2 cells cotreated with high glucose. We found that the high glucose condition causes significant increasing Ser307 phosphorylation of insulin receptor substrate-1 (IRS-1), leading to reduce insulin-stimulated phosphorylation of Akt. As the results, the insulin metabolic effects of glycogen synthesis and glucose uptake are inhibited by high glucose. However, the treatment of EGCG improves insulin-stimulated downsignaling by reducing IRS-1 Ser307 phosphorylation. Furthermore, we also demonstrated these EGCG effects are essential depends on the 5,-AMP-activated protein kinase (AMPK) activation. Together, our data suggest a putative link between high glucose and insulin resistance in HepG2 cells, and the EGCG treatment attenuates insulin signaling blockade by reducing IRS-1 Ser307 phosphorylation through the AMPK activation pathway. [source] | |||||||||||||