• Environmental Mutagens and Carcinogens
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• v.23 no.3
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• pp.94-98
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• 2003

Quercetin and naringenin are representative flavonoids that not only exert anti estrogenic, cholesterol-lowering and antioxidant activities but also can modulate the metabolism of many xenobiotics. The activity of the specific form(s) of CYP450 is likely to be a major determinant of susceptibility to chemically induced carcinogenesis between which varies among between individuals due to different dietary habits as well as genetic characteristics. People consume cooked meat or fish together with various vegetables containing substantial amounts of quercetin and naringenin that can modify the enzyme activity of CYP1A2 to stimulate or to inhibit the mutagenic activities of HCAs. Heterocyclic amines (HCAs) produced by cooking meat products at high temperatures are promutagens that are activated by cytochrome P450 (CYP) lA2. Using a newly developed Salmonella typhimurium TA1538/1A2bc-b5 strain, we tested the effect of quercetin and naringenin on the mutagenicity of 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ). TA1538/1A2bc-b5 bears two plasmids, one expressing human CYP1A2 and NADPH-P450 reductase (NPR), and the other plasmid which expresses human cytochrome b5 (cyp b5). TA1538/1A2bc-b5 cells showed high activities of 7-ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD) associated with CYP1A2 and are very sensitive to mutagenesis induced by several HCAs. MeIQ was found to be the strongest mutagen among the HCAs tested in this system. Mutagenicity of MeIQ was enhanced 50 and 42% by quercetin at 0.1 and 1 mM, respectively, but suppressed 82% and 96% at 50 mM and 100 mM. Naringenin also increased the MeIQ-induced mutation about 37% and 22% at 0.1 and 1 mM, but suppressed it 32% and 63% at 50 mM and 100 mM concentrations, respectively, in TA 1538/1A2bc-b5 cells. Thus, they stimulated the MeIQ induced mutation at low concentrations, but strongly suppressed it at high concentrations. This biphasic effect of flavonoids was due to the stimulation or the inhibition of CYP1A2 activity in a dose-dependent manner judging by the activities of EROD or MROD in the Salmonella cells. Collectively, it is likely that the biphasic effects of quercetin and naringenin on the MeIQ-induced mutagenesis in S. typhimurium TA1538/CYP1A2bc-b5 were due to their differential modification of the CYP1A2 activity in these cells.

• Proceedings of the Korean Society of Toxicology Conference
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• 2001.05a
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• pp.143-143
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• 2001

Human cytochrome P450 (CYP or P450) 3A4 (CYP3A4) is the most abundant among P450s in human liver. We previously reported that the expression of CYP3A4 in membranes prepared from E. coli coexpressed the bicistronic construct of CYP3A4 and NADPH-P450 reductase with cytochrome b$_{*}$ (b5) was showed 20-60% higher than that in membranes from E. coli expressed only the bicistronic construct with culturing longer times (48-72h).(omitted)

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.05a
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• pp.77-77
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• 2003

We have previously shown that 2, 3' , 4, 5' -tetramethoxystilbene(TMS), a trans-stilbene analogue, is one of the most potently selective inhibitor of recombinant human cytochrome P450 1B1 in vitro. In the present studies, the effects of TMS on the expression of cytochrome P450 1B1 were investigated in human mammary cell lines such as MCF-7 and MCF-10A. (omitted)

• Korean Journal of Environmental Biology
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• v.26 no.2
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• pp.87-93
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• 2008

To assess effects of contaminants on fish in Nakdong river, feral yellowfin goby Acanthogobius flavimanus were caugt in two different sites and its hepatic monooxygenase enzyme, including cytochrome P450 (CYP), NADPH-cytochrome P450 reductase (P450R), NADH-cytochrome b5 reductase (b5R), ethoxyresorufin deethylase (EROD), glutathione S-transferase (GST) were quantitatively determined. Gonadosomatic index (GSI), hepatosomatic index (HSI) and three sex steroid hormone (17$\beta$-estradiol, E2; testosterone, T; 11-ketotestosterone, 11-KT) levels of the fish were also investigated. HSI of fish from polluted site (site 1) were significantly higher than that of unpolluted site (site 2), but GSI levels were significantly lower in polluted site. No significant differences in plasma 11-KT and T levels were observed in two sites surveyed. E2 level was, however, significantly (p<0.05) higher in female fish from site 1 than site 2. In addition, hepatic EROD activity and CYP level of site 1 fish were lower than those of site 2 fish, whereas relatively high levels of P450R, b5R and GST activities were found in site 1. The results imply that yellowfin goby, especially female fish in Nakdong river estuary are affected from contaminants disrupting sex steroid hormone system.

• Korean Journal of Pharmacognosy
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• v.21 no.1
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• pp.74-82
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• 1990

The effects of naturally occurring furanocoumarins on cytochrome P-450 have been investigated in rat liver microsomes. Incubation of microsomes with an NADPH-generating system and four furanocoumarins such as imperatorin, isoimperatorin, phellopterin and byakangelicin at $37^{\circ}$ in vitro resulted in a significant destruction of cytochrome P-450. A single treatment(50 mg/kg, i.p.) of rats with each furanocoumarin caused a rapid loss of cytochrome P-450 accompanied by the loss of heme from the microsomes but not by the loss of cytochrome $b_5$. It is suggested that cytochrome P-450 is specifically destroyed by furanocoumarins in a metabolic process involving destruction of its heme group and as a consequence, hepatic enzyme activities are depressed markedly.

• Korean Journal of Medicinal Crop Science
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• v.10 no.1
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• pp.29-36
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• 2002

Epimedium koreanum Nakai(EKN) has traditionally been well-known as a herbal medicine for the promotion of stamina and the improving sexual activity of human in oriental countries including Korea and China. The aim of this study was to investigate the effect of dietary supplementation of EKN water-extract(0.025%,w/v) on age-related change of xenobiotic metabolizing system in rat liver. Long-term supply of the EKN extract to rats did not induce any discernible signs. However, the mass of liver and kidney were slightly increased by the dietary supplementation. Level of cytochrome P450, NADPH cytochrome P450 reductase, P450 dependent ethoxycoumarin O-deethylase benzphetamine N-demethylase and glutathione-S-transferase in liver were decreased with age, but, these activities in 24 months of age were declined more in rats supplied with EKN extract. Level of cytochrome b5 and NADH-cytochrome b5 reductase were also decreased with age, however, there was no significant difference between with and without EKN extract. These results indicate that long-term supplementation of EKN extract to rats from weaning to 24 months may be a burden on the liver function in old age, and may aggregate the decline of xenobiotic metabolizing enzymes activities in old age.

• BMB Reports
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• v.30 no.1
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• pp.73-79
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• 1997

This study was designed to investigate the effects of dietary garlic powder on cytochrome P450 enzymes and membrane stability in murine hepatocarcinogenesis initiated by diethylnitrosamine (DEN). Male Sprague-Dawley rats received a single intraperitoneal injection of DEN (200 mg/kg body wt) dissolved in saline. After 2 weeks on a basal diet, animals were fed diets containing 0. 0.5. 2.0. or 5.0% garlic powder for 6 weeks, and were subjected to two-thirds partial hepatectomy. The areas of placental glutathione S-transferase (GST-P) positive foci were inhibited in rats fed with garlic diets. GST-P is the most effective marker for DEN-initiated lesions. Hepatic microsomal lipid peroxidation was significantly decreased in rats fed with 2.0 and 5.0% garlic powder diets compared with that observed in the control animals and hepatic microsomal glucose 6-phosphatase (G6Pase) activity was found to increase significantly in rats fed 0.5 and 2.0% garlic powder diets. Thus as little as 0.5% garlic powder has a positive effect on the stability of hepatic microsomal membranes. p-Nitrophenol hydroxylase (PNPH) activity and the level of cytochrome P450 2E1 protein in the hepatic microsomes from rats fed diets containing 2.0 and 5.0% garlic powder were much lower than those of control microsomes. Rats fed 5.0% garlic powder diets exhibited the lowest P450 2E1 activity and protein levels among groups. Pentoxyresorufin O-dealkylase activity and immunoblot (cytochrome P450 2B1) analyses were not different between groups. However, the levels of cytochrome P450 1A1/2 protein in rats fed 0.5 and 2.0% garlic powder were significantly induced compared to controls. These results suggest that 2.0% garlic powder is effective in inhibiting the areas of GST-P positive foci, modulating certain isoforms of cytochrome P450 enzymes and stabilizing the hepatic microsomal membrane. Thus, the selective modification of cytochrome P450 enzymes and membrane stability by dietary garlic powder may influence areas of GST-P positive foci and chemoprevention of post-initiation of rat hepatocarcinogenesis.

• BMB Reports
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• v.38 no.3
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• pp.366-369
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• 2005

NADPH-cytochrome P450 reductase (CPR) transfers electrons from NADPH to cytochrome P450 and also catalyzes the one-electron reduction of many drugs and foreign compounds. Various spectrophotometric assays have been performed to examine electron-accepting properties of CPR and its ability to reduce cytochrome $b_5$, cytochrome c, and ferricyanide. In this report, reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) by CPR has been assessed as a method for monitoring CPR activity. The principle advantage of this substance is that the reduction of MTT can be assayed directly in the reaction medium by a continuous spectrophotometric method. The electrons released from NADPH by CPR were transferred to MTT. MTT reduction activity was then assessed spectrophotometrically by measuring the increase of $A_{610}$. MTT reduction followed classical Michaelis-Menten kinetics ($K_m\;=\;20\;{\mu}M$, $k_{cat}\;=\;1,910\;min^{-1}$). This method offers the advantages of a commercially available substrate and short analysis time by a simple measurement of enzymatic activity of CPR.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.209.1-209.1
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• 2003

We have previously shown that 2, 3', 4, 5' -tetramethoxystilbene(TMS) from synthetic trans-stilbene analogues, is one of the most potently selective inhibitor of recombinant human cytochrome P450 1B1 in vitro. In the present studies. the effects of TMS on the expression of cytochrome P450 1B1 were investigated in human cancer cell lines such as MCF-7 and HL -60. TCDD-stimulated P450 1B1 protein and mRNA expression was significantly suppressed by TMS in a dose-dependent manner. (omitted)

• Toxicological Research
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• v.11 no.2
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• pp.215-221
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• 1995

This paper examines the effects of dietary polyunsaturated fatty acid/saturated fatty acid (p/s) ratios and butylated hydroxytoluene (BHT) on the hepatic microsomaI mixed-function oxidase sy. stem in 2~acetylaminofiuorene (2-AAF) treated rats. Sprague-Dawley male rats were fed the diet of beef tallow (p/s 0.08), beef tallow plus soybean oil (p/s 1.0), and soybean oil (p/s 4.0) at the level of 15%fat and with or without 0.3% BHT. After 2-AAF was injected twice at the ages of 23 and 27 weeks, cholesterol/phospholipid molar ratio, thiobarbituric acid reactive substances (TBARS) level, cytochrome P450, cytochrome $b_5$, NADPH-cytochrome $b_5$, and NADPH-cytochrome c reductase activity were measured from isolated hepatic microsomal fractions. In the beef tallow (p/s 0.08) and beef tallow plus soybean oil (p/s 1.0) groups, cholesterol/phospholipid molar ratio showed decreasing tendency by 2-AAF and BHT. Cytochrome P-450 content was decreased in the group of soybean oil (p/s 4.0) and NADPH-cytochrome c reductase activity was increased by 2-AAF and BHT in all the dietary groups. While TBARS levels were increased by 2-AAF in all the dietary groups, they were reduced by BHT in the soybean oil (p/s 4.0) group. These results suggest that long term intake of soybean oil (p/s 4.0) diet induced changes in the nature of microsomal membrane and induced less cytochrome P-450, low level feeding of BHT increased cytochrome c reductase activity and lowered microsomal lipid peroxidation levels, which were increased by 2-AAF treatment.