• Archives of Pharmacal Research
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• v.18 no.3
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• pp.179-182
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• 1995

Previous study showed that $CCl_4$ administration evoked a rapid decrease in cytochrome $P_{450}$ 2E1 protein soon after the exposure due to posttranslational inhibition(Biochem. Biophys. Res. Commun. 179:449-454, 1991). In this report, aniline hydroxylase and the amounts of immunoreactive $P_{450}$ 2E1 were rapidly decreased during day 1 to 2 and recovered during day 3 to 4 after a single dose of $CCl_4$. The activity of pentoxyresorufin-O-dealkylase was also suppressed at day 1 and began to repair from day 2. However, the decrease in immunoreactive $P_{450}$ 2C content was not observed. The decreases in $P_{450}$ 2E1 enzyme activity and immunoreactive protein by acute $CCl_4$ treatment were accompanied by a decline in $P_{450}$ 2E1 mRNA level. The data thus suggested a pretranslational reduction of $P_{450}$ 2E1 during day 1 to 2 after acute $CCl_4$ treatment.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.100-100
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• 1993

Antiestrogen은 에스트로젠 의존성 유방암 치료에 사용되는 약물로써 표적 세포 내에서 에스트로젠 수용체와 작용하여 세포 증식 억제 작용을 나타내고 동시에 에스트로젠 수용체와는 구분되는 소포체 분획의 antiestrogen specific binding site (AEBS) 와도 결합을 하는 것으로 알려져 있다. 그러나, 아직 이 AEBS의 생리적 또는 약리적 기능은 밝혀져 있지 않다. 따라서 본 실험에서는 AEBS의 기능을 조사하기 위하여 cytochrome P45O III 효소군과 AEBS와의 관계를 자옹 백서를 이용하여 면역 화학 반응 실험 및 경쟁적 결합 반응 실험을 하였고, 그 결과는 다음과 같다. 1) AEBS에 대해서 SKF-525A와 metyrapone은 결합 능력을 나타내었다. 2) 자성쥐에서는 주령이 증가함에 따라 cytochrome P450양이 감소하였다. 3) 자옹성쥐 모두에서 phenobarbital 처치에 의해 cytochrome P450 III 효소양이 증가하였고, AEBS도 증가하였다. 4) 웅성쥐에서는 testosterone에 의하여 AEBS가 증가하였다. 5) 자웅성쥐 모두에 tamoxifen 관류시 cytochrome P450 III 효소양이 증가하였고 estradiol과 병용 관류시에는 tamonifen 단독 관류시보다 감소하였다. 이상의 결과에서 tamoxifen이 cytochrome P450 III을 유도할 수 있는 것으로 사료되며 cytochrome P450 III 효소군과 안티에스트로젠 결합부위와 밀접한 관련이 있는 것으로 생각된다.

• Mass Spectrometry Letters
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• v.4 no.2
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• pp.34-37
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• 2013

Honokiol and magnolol, the major bioactive neolignans of magnolia officinalis, are the most important constituents of the crude drug prescriptions that are used in the therapy of neuroses and various nervous disorders. There have been limited reports on the effects of neolignoid compounds on human cytochrome P450 activity. Therefore, the inhibitory effects of honokiol and magnolol on seven human cytochrome P450 s were evaluated in human liver microsomes. Honokiol and magnolol showed the most potent inhibition of CYP1A2-mediated phenacetin O-deethylase activity ($IC_{50}$ values of 3.5 and 5.4 mM, respectively) among the seven P450s tested. These in vitro data indicate that neolignan compounds can inhibit the activity of CYP1A2 and suggest that these compounds should be examined for potential pharmacokinetic drug interactions in vivo.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.6
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• pp.1534-1542
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• 2007

In this study, the liver protective effect of the hot water extracts of Scutellaria radix (SR) was investigated. The SR exhibited a hepatoprotective activity against $CCl_4$-induced liver damage in Sprague-Dawley (SD) rats and Chang cell. And the SR also showed significant decrease of malodialdehyde (MDA) and increase of glutathion (GSH), catalase activity in rat liver homogenate. The expression of cytochrome P450 2E1 (CYP2E1), measured by RT-PCR and western blot, was significantly decreased in the SR treated SD rats and Chang cell. But $CCl_4$ and SR has no significant effect on 1A1 and 3A1 isoform of cytochrome P450. Based on these findings, it is suggested that hepatoprotective effects of SR possibly related to antioxidative effects and downregulation of CYP2E1 expression.

• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.16-16
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• 1998

The role of phospholipids in the membrane binding and subsequent insertion of the microsomal protein rabbit cytochrome P450 (P450) lA2 into phospholipid bilayers was investigated. The insertion of P450 lA2 into phospholipid bilayers was determined by the amount of quenching of Trp fluorescence of P450 lA2 by pyrene and brominated and doxyl-labeled phospholipids.(omitted)

• Toxicological Research
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• v.14 no.3
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• pp.293-300
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• 1998

Previous studies have shown that the heterocycles including thiazoles are efficacious in inducing phase phase II metabolizing enzyme as well as certain cytochrome P450s and that the inductin of these matabolizing enzymes by the heterocyclic agents is highly associated with their hepatotoxicity. In the present study, the effects of benzylisothiazole (BIT), which has a isothiazole moiety, on the expression of microsomal epoxide hydrolase (mEH), major glutathione S-transerases and cytochrome P450s were studied in the rat liver in association with its hepatotoxicity. Treatment of rats with BIT(1.17 mmol/kg, 1~3d) resulted in substantial increases in the mEH. rGSTA2, rGSTA2, rGSTM1 and rGSTM2 mRNA levels, whereas rGSTA3 and rGSTA5 mRNA levels were increased to much lesser extents. A time-course study showed that the mRNA levels of mEH and rGSTs were greater at 24hr after treatment than those after 3 days of consecutive treatment. Relative changes in mEH and rGST mRNA levels were consistent with those in the proteins, as assessed by Western immunoblot analysis. Hepatic cytochrom P450 levels were monitored after BIT treatment under the assumption that metabolic activation of BIT may affect expression of the enzymes in conjunction with hepatotoxicity. Immunoblot analysis revealed that cytochrome P450 2B1/2 were 3-to 4-fold induced in rats teatd with BIT(1.17 mmol/kg/day.3days), whereas P450 1A2, 2C11 and 3A1/2 levels were decreased to 20~30% of those in unteatd rats. P450 2E1 was only slightly decreased by BIT. Thus, the levels of several cytochrome P450s were suppressed by BIT treatment. Rats treated with BIT at the dose of 1.17mmol/kg for 3 days exhibited extensive multifocal nodular necrosis with moderate to extensive diffuse liver cell degeneration. No notable toxicity was observed in the kidney. These results showed that BIT induces mEH and rGSTs in the liver with increases in the mRNA levels, whereas the agent significantly decreased major cytochrome P450s. The changes in the detoxifying enzymes might be associated with the necrotic liver after consecutive treatment.

• Toxicological Research
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• v.23 no.3
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• pp.189-196
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• 2007

Cytochrome P450 (P450) enzymes are the major catalysts involved in the biotransformation of various drugs, pollutants, carcinogens, and many endogenous compounds. Most of chemical carcinogens are not active by themselves but they require metabolic activation. P450 isozymes playa pivotal role in the metabolic activation. The activation of arylamines and heterocyclic arylamines (HAAs) involves critical N-hydroxylation, usually by P450. CYP1A2 plays an important role in these reactions. Broad exposure to many of these compounds might cause carcinogenicity in animals and humans. On the other hand, P450s can be also involved in the bioactivation of other chemicals including alcohols, aflatoxin B1, acetaminophen, and trichloroethylene, both in humans and in experimental animals. Understanding the P450 metabolic activation of many chemicals is necessary to develop rational strategies for prevention of their toxicities in human health. An important part is the issues of extrapolation between species in predicting risks and variation of P450 enzyme activities in humans.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.1
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• pp.155-161
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• 2008

Carbon tetrachloride $(CCl_4)-induced$ liver injury depends on a toxic agent that has to be metabolized by the liver NAPDH-cytochrome P450 enzyme system to a highly reactive intermediate. Although several isoforms of cytochrome P450 may metabolize $CC1_4$, attention has been focused largely on the cytochrome P450 2E1 (CYP2E1), which is ethanol-inducible. Alternations in the activity of CYP2E1 affect the susceptibility to hepatic injury from $CC1_4$. In this study, the liver protective effect of the hot water extracts of Scutellaria radix (SR) was investigated. The SR exhibited a hepatoprotective activity against $CCl_4-induced$ liver damage in Chang liver cells. The expression of CYP2E1, measured by RT-PCR and Western blot analysis, was significantly decreased by SR treatment in Chang cells. Based on these findings, it is suggested that hepatoprotective effect of SR possibly related to downregulation of CYP2E1 expression.

• Toxicological Research
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• v.11 no.2
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• pp.329-335
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• 1995

Incubation of aflatoxin $B_1$ $(AFB_1)$ with microsomes isolated from human liver number 110 yielded two metabolite peaks which were aflatoxin $Q_1$ $(AFQ_1)$ and $(AFB_1)$-exo-8, 9-epoxide (exo-epoxide) in high performance liquid chromatography. Production ratio of $AFQ_1$ to exo-epoxide was 2.43$\pm $0.04. Metabolism of $(AFB_1)$ to $(AFQ_1)$ and exo-epoxide was inhibited by troleandomycin in a same degree although troleandomycin was not activated as a mechanism-based inhibitor. The inhibitory effect was dependent upon either the incubation time with $(AFB_1)$ or the preincubation time before the addition of $(AFB_1)$. Incubation of troleandomycin and NADPH by the microsomes resulted in the formation of a cytochrome P 450 (P450)-metabollc intermediate (MI) complex and the level was approximately 80% of total P450 3A4 in the microsomes. This figure was similar to that of the inhibitory effect of troleandomycin on $AFB_1$ metabolism. Glutathione which was reported that it prevented the formation of MI complex in rat liver microsomes did not inhibit the formation of MI complex in human liver microsomes. These results suggested that the inhibitory effect of troleandomycin on $AFB_1$ metabolism is due to the formation of MI complex with P450 3A4. And the reaction mechanism of troleandomycin by human liver microsomes might be dlfferent from that one by rat liver microsomes.

• Biomolecules & Therapeutics
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• v.17 no.4
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• pp.455-460
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• 2009

Foods of plant origin, especially fruits and vegetables, have attracted attention because of their potential benefits to human health. In this report, Rubi Fructus (RF), the dried unripe fruit of Rubus coreanus Miq (Rosaceae) and ellagic acid (EA) purified from RF were used to test their potential hepatoprotective effect against acetaminophen (AAP)-induced hepatotoxicity in rats. RF extract (RFext) and EA reduced the elevated levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) in serum and the content of lipid peroxide in liver by AAP administration, while the increment of the cellular glutathione (GSH) content and the induction of glutathione S-transferase (GST) and glutathione peroxidase (GSH-PX) which were decreased by AAP administration. RFext and EA from RFext did not affect the two major form of cytochrome P450s, cytochrome P450 2E1 (CYP2E1) and cytochrome P450 1A2 (CYP1A2), but downregulated the cytochrome P450 3A4 (CYP3A4) related to the conversion of AAP to N-acetyl-P-benzoquinone imine (NAPQI). These results suggest that RFext and EA from RF exhibit a hepatoprotective effect not only by increasing antioxidant activities but also by down-regulating CYP3A4 in the AAP-intoxicated rat.