scholarly journals Regulation of 3-hydroxy-3-methylglutaryl-CoA reductase mRNA contents in human hepatoma cell line Hep G2 by distinct classes of mevalonate-derived metabolites

1988 ◽  
Vol 255 (1) ◽  
pp. 61-67 ◽  
Author(s):  
L H Cohen ◽  
M Griffioen
Keyword(s):  
Reductase Activity ◽  
Hepatoma Cell ◽  
Enzyme Level ◽  
Mrna Level ◽  
Hepatoma Cell Line ◽  
Hep G2 ◽  
Hmg Coa Reductase ◽  
Mrna Content ◽  
Reductase Mrna ◽  
Coa Reductase

Hep G2 cells were incubated under conditions known to influence the HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase activity, e.g. in the presence of compactin (a competitive inhibitor of HMG-CoA reductase itself) and U18666A (a squalene-2,3-epoxide cyclase inhibitor). We studied the effects of these conditions both on the HMG-CoA reductase activity and on the reductase mRNA content. In the presence of compactin the mRNA content increased, but less than the enzyme activity, as determined after removal of the inhibitor. The increase in mRNA could be prevented by addition of mevalonate or by a combination of low-density lipoprotein (LDL) plus a low concentration of mevalonate. LDL alone prevented the compactin-induced increases in mRNA and activity only partially. The effect of U18666A on reductase mRNA content and activity was biphasic, i.e. a slight decrease at low (0.3-0.5 microM) concentrations, with a concomitant formation of polar sterols [Boogaard, Griffioen & Cohen (1987) Biochem. J. 241, 345-351], and an increase at high (20-30 microM) concentrations, with complete blockage of sterol formation. At these high concentrations of U18666A, additional compactin (2 microM) increased the reductase activity, but not the mRNA content. We conclude that non-sterol metabolites of mevalonate regulate exclusively at the enzyme level, whereas sterol metabolites regulate at the reductase mRNA level. In the latter group of regulators we distinguish mevalonate metabolites which can, and metabolites which cannot, be replaced by exogenous LDL.

Effect of geraniol on fatty-acid and mevalonate metabolism in the human hepatoma cell line Hep G2

2006 ◽  
Vol 84 (1) ◽  
pp. 102-111 ◽  
Author(s):  
Monica P Polo ◽  
Margarita G de Bravo
Keyword(s):  
Fatty Acid ◽  
Cell Line ◽  
Reductase Activity ◽  
Hepatoma Cell ◽  
Cellular Growth ◽  
Hepatoma Cell Line ◽  
Dependent Manner ◽  
Hep G2 ◽  
Hmg Coa Reductase ◽  
Coa Reductase

Monoterpenes have multiple pharmacological effects on the metabolism of mevalonate. Geraniol, a dietary monoterpene, has in vitro and in vivo anti-tumor activity against several cell lines. We have studied the effects of geraniol on growth, fatty-acid metabolism, and mevalonate metabolism in the human hepatocarcinoma cell line Hep G2. Up to 100 µmol geraniol/L inhibited the growth rate and 3-hydroxymethylglutaryl coenzyme A reductase (HMG-CoA) reductase activity of these cells. At the same concentrations, it increased the incorporation of cholesterol from the medium in a dose-dependent manner. Geraniol-treated cells incorporated less 14C-acetate into nonsaponifiable lipids, inhibiting its incorporation into cholesterol but not into squalene and lanosterol. This is indicative of an inhibition in cholesterol synthesis at a step between lanosterol and cholesterol, a fact confirmed when cells were incubated with 3H-mevalonate. The incorporation of 3H-mevalonate into protein was also inhibited, whereas its incorporation into fatty acid increased. An inhibition of Δ5 desaturase activity was demonstrated by the inhibition of the conversion of 14C-dihomo-γ-linolenic acid into arachidonic acid. Geraniol has multiple effects on mevalonate and lipid metabolism in Hep G2 cells, affecting cell proliferation. Although mevalonate depletion is not responsible for cellular growth, it affects cholesterogenesis, protein prenylation, and fatty-acid metabolism.Key words: geraniol, Hep G2, HMG-CoA reductase, mevalonate, fatty acids.

scholarly journals Effects of compactin, mevalonate and low-density lipoprotein on 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity and low-density-lipoprotein-receptor activity in the human hepatoma cell line Hep G2

1984 ◽  
Vol 222 (1) ◽  
pp. 35-39 ◽  
Author(s):  
L H Cohen ◽  
M Griffioen ◽  
L Havekes ◽  
D Schouten ◽  
V van Hinsbergh ◽  
...  
Keyword(s):  
Reductase Activity ◽  
Hepatoma Cell ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hepatoma Cell Line ◽  
Low Density ◽  
Hep G2 ◽  
Human Hepatoma Cell ◽  
Hmg Coa Reductase ◽  
Coa Reductase

Compactin, an inhibitor of HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase, decreased cholesterol synthesis in intact Hep G2 cells. However, after the inhibitor was washed away, the HMG-CoA-reductase activity determined in the cell homogenate was found to be increased. Also the high-affinity association of LDL (low-density lipoprotein) to Hep G2 cells was elevated after incubation with compactin. Lipoprotein-depleted serum, present in the incubation medium, potentiated the compactin effect compared with incubation in the presence of human serum albumin. Addition of either mevalonate or LDL prevented the compactin-induced rise in activities of both HMG-CoA reductase and LDL receptor in a comparable manner. It is concluded that in this human hepatoma cell line, as in non-transformed cells, both endogenous mevalonate or mevalonate-derived products and exogenous cholesterol are able to modulate the HMG-CoA reductase activity as well as the LDL-receptor activity.

scholarly journals Regulation of cholesterol biosynthesis and metabolismin Hep G2 cells by δ8(14)-15-ketoergostane derivatives

2010 ◽  
Vol 56 (5) ◽  
pp. 576-586
Author(s):  
A.R. Mehtiev ◽  
V.I. Fedchenko ◽  
Ya.V. Tkachev ◽  
V.P. Timofeev ◽  
A.Yu. Misharin
Keyword(s):  
Cholesterol Biosynthesis ◽  
Mrna Level ◽  
Hep G2 ◽  
Hep G2 Cells ◽  
Hmg Coa Reductase ◽  
Side Chain Conformation ◽  
Genes Expression ◽  
G2 Cells ◽  
Coa Reductase ◽  
The Comparative Study

The comparative study of effects of 5α-cholest-8(14)-en-15-on-3β-ol (I), (22E)-5α-ergosta-8(14),22-dien-15-on-3β-ol (II), (22S,23S)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (III) and (22R,23R)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (IV) on HMG-CoA reductase, CYP27A1 and CYP3A4 genes expression in Hep G2 cells was performed. In the contrast to 15-ketocholestane derivative (I), 15-ketoergostane derivatives (II - IV) decreased the HMG- CoA reductase mRNA level; (22R,23R)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (IV) significantly increased CYP3A4 mRNA level (320% from control). Ketosterol (II) was found to be a more potent inhibitor of cholesterol biosynthesis in Hep G2 cells at a prolong incubation, compared with ketosterol (I). The side chain conformation of compounds (I) - (IV) was evaluated by computational modeling; the correlation between biological activity of these compounds and conformational flexibility of their side chains was found. The results obtained indicated that Δ8(14)-15-ketoergostane derivatives may be used as a sterol biosynthesis and metabolism regulators in liver cells.

Effect of ethanol on cell growth and cholesterol metabolism in cultured Hep G2 cells

2003 ◽  
Vol 81 (6) ◽  
pp. 379-386 ◽  
Author(s):  
Mónica P Polo ◽  
Margarita G de Bravo ◽  
María JT de Alaniz
Keyword(s):  
Growth Rate ◽  
Cell Growth ◽  
Culture Medium ◽  
Cholesterol Metabolism ◽  
Reductase Activity ◽  
Hep G2 ◽  
Hep G2 Cells ◽  
Hmg Coa Reductase ◽  
G2 Cells ◽  
Coa Reductase

The Hep G2 human hepatoma cell line has been recognized as an excellent in vitro human model system. For this reason, this line was used to study the effect of ethanol on HMG-CoA reductase activity concerning cell growth and cholesterol metabolism. Cells were incubated in ethanol-containing medium (0–400 mmol/L) for up to 102 h. Ethanol caused an inhibition in the growth rate and in HMG-CoA reductase activity that could be reverted by the removal of ethanol from the culture medium, indicating no cellular damage. These changes cannot be ascribed to the regulatory effect of cholesterol levels, since its content was not modified either in the cells or in the medium. The addition of mevalonate to the culture medium could not revert the growth rate inhibition evoked by ethanol. Moreover, ethanol produced an increment in the cholesterol efflux in [3H]cholesterol-prelabeled cells. We conclude that the decrease in HMG-CoA reductase activity evoked by ethanol treatment on Hep G2 cells would not be the cause but the consequence of the impairment in cellular growth, since this impairment could not be reverted by the addition of mevalonate to the culture medium.Key words: ethanol, cholesterol, HMG-CoA reductase, hepatoma cells, lipid metabolism.

scholarly journals Co-ordinate regulation of low-density-lipoprotein receptor and 3-hydroxy-3-methylglutaryl-CoA reductase and synthase gene expression in HepG2 cells

1989 ◽  
Vol 260 (3) ◽  
pp. 731-736 ◽  
Author(s):  
D T Molowa ◽  
G M Cimis
Keyword(s):  
Hepg2 Cells ◽  
Cholesterol Biosynthesis ◽  
Hepatoma Cell ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Hepatoma Cell Line ◽  
Low Density ◽  
Hmg Coa Reductase ◽  
Coa Reductase

Cellular processes responsible for maintaining cholesterol homoeostasis are highly regulated. To determine whether two of these processes, cholesterol biosynthesis and receptor-mediated uptake of low-density lipoprotein (LDL), are co-ordinately regulated in human liver, we employed a human hepatoma cell line (HepG2) and measured the accumulation of mRNA for LDL receptor, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase and HMG-CoA synthase under a variety of conditions. Genomic Southern-blot analysis demonstrated that the integrity of these genes is maintained in the transformed cell. Treatment of HepG2 cells with mevalonate, 25-hydroxycholesterol, LDL, lovastatin or miconazole resulted in a similar effect on the accumulation of all three mRNAs at the concentrations tested. The onset of the response to drug, whether repression or induction of mRNA accumulation, occurred after approximately the same period of exposure for each mRNA. We conclude that the expression of the LDL receptor, HMG-CoA reductase and HMG-CoA synthase is co-ordinately regulated in HepG2 cells.

scholarly journals Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in human hepatoma cell line Hep G2. Effects of inhibitors of cholesterol synthesis on enzyme activity

1987 ◽  
Vol 241 (2) ◽  
pp. 345-351 ◽  
Author(s):  
A Boogaard ◽  
M Griffioen ◽  
L H Cohen
Keyword(s):  
Coenzyme A ◽  
Reductase Activity ◽  
Hepatoma Cell ◽  
Lipid Fraction ◽  
Hepatoma Cell Line ◽  
Dependent Manner ◽  
Hep G2 ◽  
Human Hepatoma Cell ◽  
Sites Of Action ◽  
Coenzyme A Reductase

Incubating Hep G2 cells for 18 h with triparanol, buthiobate and low concentrations (less than 0.5 microM) of U18666A, inhibitors of desmosterol delta 24-reductase, of lanosterol 14 alpha-demethylase and of squalene-2,3-epoxide cyclase (EC 5.4.99.7) respectively, resulted in a decrease of the HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase activity. However, U18666A at concentrations higher than 3 microM increased the HMG-CoA reductase activity in a concentration-dependent manner. None of these inhibitors influenced directly the reductase activity in Hep G2 cell homogenates. Analysis by t.l.c. of 14C-labelled non-saponifiable lipids formed from either [14C]acetate or [14C]mevalonate during the cell incubations confirmed the sites of action of the drugs used. Beside the 14C-labelled substrates of the blocked enzymes and 14C-labelled cholesterol, another non-saponifiable lipid fraction was observed, which behaves as polar sterols on t.l.c. This was the case with triparanol and at those concentrations of U18666A that decreased the reductase activity, suggesting that polar sterols may play a role in suppressing the reductase activity. In the presence of 30 microM-U18666A (sterol formation blocked) the increase produced by simultaneously added compactin could be prevented by addition of mevalonate. This indicates the existence of a non-sterol mevalonate-derived effector in addition to a sterol-dependent regulation. LDL (low-density lipoprotein), which was shown to be able to decrease the compactin-induced increase in reductase activity, could not prevent the U18666A-induced increase. On the contrary, LDL enhanced the U18666A effect, showing that the LDL regulation is not merely the result of introducing cholesterol to the cells.

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