The mycoestrogen zeranol at high dosage antagonizes transient receptor potential channel activities in 3T3 L1 cells.

Recent findings have revealed that exposure to environmental contaminants may result in obesity and pose a health threat to the general public. As the activity of transient receptor potential channels (TRPs) plays a permissive role in adipogenesis, the interactions between TRPs and some food pollutants, i.e. bisphenol A, di (2-ethylhexyl) phthalate, zearalenone, and zeranol at 10 µM were investigated in the present study. TRP-V1,-V3, -C4 and -C6 are reported to be differentially expressed in the adipocyte differentiation, and immunoblotting was performed to quantify changes in these TRPs affected by the pollutants. Our result indicated that the mycoestrogen zeranol or α-zearalanol suppressed the expression of the V1 and C6 isoforms. Subsequently, confocal microscopy was used to measure the calcium inflow repressed by zeranol from 0.1 µM to 10 µM. Oil Red O staining was used to determine the differentiation of 3T3 L1 preadipocytes. Zeranol could suppress the expression of TRP-V1 and -C6 protein and inhibit the associated flow of calcium into the cytosol of 3T3 L1 cells. Its IC50 value for inhibiting calcium inflow stimulated by 40 µM capsaicin or 10 µM GSK1702934A was estimated to be around 6 µM. Reduced TRP-V1 or -C6 activity might result in promoting adipogenesis. In conclusion, this study demonstrated that zeranol could potentiate fat cell differentiation through antagonizing TRP-V1 and -C6 activities.

The livestock growth-promoter zeranol facilitates GLUT4 translocation in 3T3 L1 adipocytes.

Zeranol is an approved but controversial growth-promoting agent for livestock in North America. It is a mycotoxin metabolite secreted by the Fusarium family fungi. The regulatory bodies in this region have established the acceptable daily intake and exposure below the level would not significantly increase the health risk for humans. However, their European counterparts have yet to establish an acceptable level and do not permit the use of this agent in farm animals. Given the growth-promoting ability of zeranol, its effect on energy metabolism was investigated in the current study. Our results indicated that zeranol could induce glucose transporter type 4 (GLUT4) expression in 3T3 L1 cells at 10 µM and initiate the translocation of the glucose transporter to the membrane as assayed by confocal microscopy. The translocation was likely triggered by the increase of GLUT4 and p-Akt. The insulin signal transduction pathway of glucose translocation was analyzed by Western blot analysis. Since no increase in the phosphorylated insulin receptor substrate in zeranol-treated cells was evidenced, the increased p-Akt and GLUT4 amount should be the mechanism dictating the GLUT4 translocation. In summary, this study showed that zeranol could perturb glucose metabolism in differentiated 3T3 L1 adipocytes. Determining the growth-promoting mechanism is crucial to uncover an accepted alternative to the general public.

The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

Previously, the V1-3 isoforms of the transient receptor potential channel (TRP) have been shown to promote or prevent adipocyte differentiation. In the current study, the C isoforms were screened for blocking adipogenesis. The hypothesis that the TRP classic or canonical (TRPC) deters adipocyte differentiation was investigated in 3T3-L1 cells employing the channel-specific activator and antagonist, silencing, and overexpression techniques. Fat accumulation in cells was visualized by Oil Red O staining. Intracellular calcium inflow was estimated by confocal microscopy. A high-fat (HF) feeding study was also performed on C57BL/6J mice to verify the findings in the cell model. Among the 6 C isoforms tested, only TRPC-6 inhibited the differentiation of fat cells. The phytochemical quercetin induced the channel protein expression. Calcium-imaging results also revealed that the flavonoid could trigger calcium inflow. Coadministration of quercetin (1 or 20 mg/kg body weight) in an HF diet prevented TRPC-6 from declining and attenuated phosphorylated (p)-PKB and PI3k, as well as the proliferation of visceral fat cells. The present study illustrated that TRPC-6 activation could perturb adipocyte differentiation. The food flavonoid quercetin was a TRPC-6 inducer and activator and it could prevent adipogenesis in mice.-Tan, Y. Q., Kwan, H. Y., Yao, X., Leung, L. K. The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

PCP4/PEP19 upregulates aromatase gene expression via CYP19A1 promoter I.1 in human breast cancer SK-BR-3 cells.

The Purkinje cell protein 4/peptide 19 (PCP4/PEP19) is a novel breast cancer cell expressing peptide, originally found in the neural cells as an anti-apoptotic factor, could inhibit cell apoptosis and enhance cell migration and invasion in human breast cancer cell lines. The expression of PCP4/PEP19 is induced by estrogens in estrogen receptor-positive (ER+) MCF-7 cells but also highly expressed in ER- SK-BR-3 cells. In this study, we investigated the effects of PCP4/PEP19 on aromatase gene expression in MCF-7 and SK-BR-3 human breast cancer cells. In SK-BR-3 cells but not in MCF-7 cells, PCP4/PEP19 knockdown by siRNA silencing decreased the aromatase expression in gene transcriptional level. When PCP4/PEP19 was overexpressed by CMV promoter-driven PCP4/PEP19 expressing plasmid transfection, aromatase gene transcription increased in SK-BR-3 cells. This aromatase gene transcription is mainly mediated through promoter region PI.1, which is usually active in the placental tissue but not in the breast cancer tissue. These results indicate a new function of PCP4/PEP19 that would enhance aromatase gene upregulation to supply estrogens in heterogeneous cancer microenvironment.

Co-administrating apigenin in a high-cholesterol diet prevents hypercholesterolaemia in golden hamsters.

OBJECTIVES: Hypercholesterolaemia is a major risk factor for developing atherosclerosis. Increased consumption of fruits and vegetables is recommended to hypercholesterolaemic patients. In this study, the hypocholesterolaemic effect of apigenin and luteolin was evaluated in a hamster model. METHODS: Hamsters were put on a high-cholesterol diet for 9 weeks, and apigenin or luteolin was administered in the diet at 60 and 300 ppm. KEY FINDINGS: Both apigenin and luteolin supplementations could attenuate the aorta plaque formation by 30% and 20%, respectively. Apigenin-fed hamsters at both dosages displayed a 1.5-fold increase in hepatic Ldlr expression and a 40% reduction in non-HDL cholesterol level as compared with those in the control fed a high-cholesterol (HC) diet. Besides, faecal elimination of cholesterol was facilitated by 20% in the hamsters with high apigenin consumption. Suppressing the expression of the cholesterol transporter ncp1l1 in the intestinal mucosa could block the cholesterol absorption and promote its elimination. The differential regulations of ncp1l1 and Ldlr appeared to be the underlying hypocholesterolaemic mechanism of apigenin in this model system. Luteolin supplementation, on the other hand, had no effect on the blood cholesterol. CONCLUSIONS: This study illustrated that dietary administration of apigenin attenuated HC feeding-induced hypercholesterolemia in hamsters.

The citrus flavonone hesperetin attenuates the nuclear translocation of aryl hydrocarbon receptor.

The environmental polycyclic aromatic hydrocarbons (PAH) and dioxins are carcinogens and their adverse effects have been largely attributed to the activation of AhR. Hesperetin is a flavonone found abundantly in citrus fruits and has been shown to be a biologically active agent. In the present study, the effect of hesperetin on the nuclear translocation of AhR and the downstream gene expression was investigated in MCF-7 cells. Confocal microscopy indicated that 7, 12-dimethylbenz[α]anthracene (DMBA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) -induced nuclear translocation of AhR was deterred by hesperetin treatment. The reduced nuclear translocation could also be observed in Western analysis. Reporter-gene assay further illustrated that the induced XRE transactivation was weakened by the treatment of hesperetin. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that the gene expressions of CYP1A1, 1A2, and 1B1 followed the same pattern of AhR translocation. These results suggested that hesperetin counteracted AhR transactivation and suppressed the downstream gene expression.

Apigenin and luteolin display differential hypocholesterolemic mechanisms in mice fed a high-fat diet.

Hypercholesterolemia is a major risk factor in the development of atherosclerosis. High blood cholesterol can be the result of increased biosynthesis or reduced elimination of cholesterol in the system. Increased consumption of fruits and vegetables is recommended for patients suffering from hypercholesterolemia. The plant food flavones apigenin and luteolin have previously been shown to suppress the synthesis of cholesterol in human hepatocytes. The effectiveness of these two flavones in controlling blood cholesterol was examined in a mouse model in the present study. Mice were fed a high-fat diet and apigenin or luteolin at 50 and 250 ppm was mixed in the diet. After 8 weeks of treatment, the administration of 250 ppm apigenin or 250 ppm luteolin could modulate the total and serum non-HDL cholesterol. The expressions of srebf-2 mRNA, Srebp-2 protein and Hmgcr protein were decreased in the livers of apigenin-treated mice; meanwhile, AMPK was activated in this group of mice. In contrast, suppressed ncp1l1 and induced abcg-5/8 mRNA expressions were seen in the intestinal mucosa of luteolin-fed animals. Increased fecal cholesterol content was also observed in the luteolin-treated mice. These results revealed that apigenin suppressed the biosynthesis of cholesterol, whereas luteolin promoted the elimination of cholesterol. In summary, this study illustrated that the two flavones could attenuate high-fat feeding-induced hypercholesterolemia in two different mechanisms.

Methylation dictates PI.f-specific CYP19 transcription in human glial cells.

CYP19 is the single copy gene encoding for the estrogen synthetic enzyme aromatase. Alternate splicing of the promoter is the regulatory mechanism of this gene. In the brain, estrogen is synthesized in neuronal and glial cells and the gene is mainly regulated by the alternate promoter PI.f. The hormone produced in this vicinity has been associated with maintaining normal brain functions. Previously, epigenetic regulation has been shown in the promoters PII and I.3 of CYP19 in adipocytes. In the present study, the methylation of PI.f in CYP19 was examined in glial cells. Treatment of the hypomethylating agent 5-aza-2'deoxycytidine increased CYP19 mRNA species in U87 MG cells while little changes were observed in the other glia cell lines. As PI.f is also chiefly used in T98G cells with high expression of CYP19, the methylation statuses of the promoter in these two cell models were compared. Our results showed that treating U87 MG cells with 10 µM 5-aza-2'deoxycytidine significantly induced a ∼10-fold increase in CYP19 transcription and ∼80% increase in aromatase activity. In contrast, the same treatment did not change either endpoint in T98G cells. Further investigation illustrated the CpGs in PI.f were differentially methylated in the two cell lines; 63% and 37% of the 14 CpG sites were methylated in U87 MG and T98G cells respectively. In conclusion, this study illustrated that the brain-specific PI.f derived CYP19 expression can be regulated by DNA methylation.

Exposure to 2,2',4,4'-tetrabromodiphenyl ether at late gestation modulates placental signaling molecules in the mouse model.

Polybrominated diphenyl ethers (PBDEs) are flame retardants generally employed in manufacturing household items. Surface water may remove and carry these chemicals to the drainage upon disposal of the items, and ultimately the chemicals enter our food chain. 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is a PBDE congener commonly found in contaminated seafood. The placenta is the site of nutrient exchange and is responsible for reproductive hormone secretion during pregnancy. In the present study, pregnant ICR mice were given p.o. daily doses of BDE-47 at 0, 0.36, 3.6, 36 mg/kg for 4 days (from E13.5 to E16.5). Compared to the control group, increased rates of stillborn and low birth weight were observed in mice treated with 36 mg BDE-47/kg. Plasma testosterone and progesterone levels were reduced in mice treated with 36 mg BDE-47/kg. In addition, the group treated with 3.6 mg/kg of BDE-47 displayed decreased growth hormone (Gh) peptide expression in the placental tissue extracted at E17.5. As this peptide stimulates growth, the expression pattern might suggest compromised fetal development. Further analysis indicated that mitogen-activated protein kinases (MAPK) were activated in the placental tissue of the BDE-47-treatment groups. The activation of these signaling molecules might affect the hormonal and other physiological functions in the tissue.

The flame retardant 2,2',4,4'-Tetrabromodiphenyl ether enhances the expression of corticotropin-releasing hormone in the placental cell model JEG-3.

Polybrominated diphenyl ethers (PBDEs) are chemicals used as flame retardants in household products. After disposing of these items, PBDEs leach from the products by surface water. BDE-47 is a PBDE congener commonly isolated from contaminated food and is the most studied isomer. The placenta is the major source of hormones during pregnancy, and an elevated level of corticotrophin-releasing hormone (CRH) is associated with premature delivery. In the present study, we examined changes in the placental CRH expression under BDE-47 exposure in the JEG-3 cell model system. These placental cells are derived from human choriocarcinoma. Our result showed that this pollutant induced the CRH mRNA expression at 0.5 nM or above in the cells. A similar trend was observed when CRH peptide was determined by Western analysis in the cell lysates. As previous studies have shown the importance of signal transduction pathways in the gene regulation, the status of some protein kinases in the present study was investigated. The phosphorylated PKCα, JNK, and P38 were increased by the toxicant treatment, and administering the specific inhibitors could counteract the induced CRH expression. It appeared that the signaling transduction pathway of PKC was a significant contributor in the transcriptional regulation. Further study by using Electrophoretic Mobility Shift Assay suggested that AP-2 was the ultimate DNA-binding element for the initiation of gene transcription. Because an untimely increased CRH may compromise fetal development and induce preterm birth, the present study suggested that endocrine changes in pregnancy should be taken into consideration in the next assessment.

Dietary flavones counteract phorbol 12-myristate 13-acetate-induced SREBP-2 processing in hepatic cells.

Consumption of fruits and vegetables is generally regarded as beneficial to plasma lipid profile. The mechanism by which the plant foods induce desirable lipid changes remains unclear. SREBP-2 is crucial in cholesterol metabolism, and it is a major regulator of the cholesterol biosynthesis enzyme HMGCR. Our lab has previously illustrated that apigenin and luteolin could attenuate the nuclear translocation of SREBP-2 through an AMPK-dependent pathway. In the present study, these two flavones were studied for their ability to deter the same in an AMPK-independent signaling route. The processing of SREBP-2 protein was promoted by phorbol 12-myristate 13-acetate (PMA) in the hepatic cells WRL and HepG2, and the increased processing was reversed by apigenin or luteolin co-administration. EMSA results demonstrated that the PMA-induced DNA-binding activity was weakened by the flavones. The increased amount of nuclear SREBP-2 in cells was attenuated by the flavonoid as shown by immunocytochemical imaging. Quantitative reverse transcriptase-polymerase chain reaction assay demonstrated that the transcription of HMGCR under both flavone treatments was reduced. However, apigenin appeared to be stronger than luteolin in restraining PMA-induced HMGCR mRNA expression. Since PMA is a diacylglycerol analog, these findings might have some physiological implications.

Aflatoxin B1 disrupts transient receptor potential channel activity and increases COX-2 expression in JEG-3 placental cells.

Aflatoxins are fungal metabolites which pose a major threat to food safety. Although these mycotoxins are established hepatocarcinogens, their effect on the reproductive organ is unknown. Transient Receptor Potential Channels (TRPs) are ubiquitously expressed in human tissues, including the placenta. These channels are associated with various functions in the placenta. The fetus and the placenta are especially sensitive to xenobiotic assault; therefore, exposure to the aflatoxins during gestation might lead to the undesirable outcome. Previously we have shown that aflatoxin B1 administered in late gestation may increase cox-2 expression in mouse placentae. In the present study, we examined the effect of aflatoxin B1 on COX-2 by using the placental cell model JEG-3 and the respective signaling pathway. In our result, COX-2 expression was induced by the mycotoxin administration. The intracellular calcium levels were also increased in cells by aflatoxin B1 treatment as little as 1 nM. Immunoblot result showed that some TRP expressions were elevated. As inflated intracellular calcium might activate MAPKs, the underlying signaling pathway was investigated. With the help of TRP-specific inhibitors, the mycotoxin appeared to increase the expression of TRPC-3 and activate PKCß and ERK. The significance of COX-2 in pregnancy has been well established. Exposure to this mycotoxin may perturb the physiological processes dictated by COX-2 in pregnancy.

Assessing placental corticotrophin-releasing hormone disruption by hexestrol in a cell model.

Studies have shown that corticotrophin-releasing hormone (CRH) and relaxin are associated with early delivery. Our lab previously has shown the mycotoxin zeranol increases placental CRH expression. The mycotoxin is used in the farming industry to promote cattle growth, and some synthetic hormones are also used for the same purposes. In order to complete the picture of these growth promoting agents, we attempted to examine the synthetic hormones on the placental gene expression in the current study. Among the tested compounds, hexestrol induced the CRH mRNA and protein expression at 100nM in JEG-3 cells. As signal transduction pathways have been described in the transcriptional control previously, the activations of several protein kinases were determined. P38, PKCß and JNK were activated upon hexestrol treatment. Since the P38-inhibitor SB203580 prevented hexestrol from inducing CRH in a subsequent experiment, P38 was likely involved in the transcriptional regulation. Electrophoretic mobility shift assay revealed an increase in the CRE binding activity in CRH promoter. This study showed that hexestrol exposure might be a concern for pregnant women.

Zeranol induces COX-2 expression through TRPC-3 activation in the placental cells JEG-3.

Transient Receptor Potential Channels (TRPs) are commonly expressed in the reproductive tissues in human. Many female reproductive processes have been associated with these TRPs. The mycotoxin zeranol or α-zearalanol is derived from fungi in the Fusarium family. Limited exposure to zeranol appears to be safe. In North America, farmers are using synthetic zeranol to promote growth in livestock. As the health risks of exposure to residual zeranol have not been determined, this practice is disallowed in the European Community. In the present study the cellular calcium levels were elevated in JEG-3 cells treated with zeranol at or above 10nM. Subsequent study indicated that expressions of TRP channels were induced. In response to the calcium flow, ERK, P38 and PKCß were activated and COX-2 expression was increased. Specific TRP inhibitors were employed to establish the connection between the ion channel activity and COX-2 expression, and TRPC-3 appeared to be the triggering mechanism. Since the involvement of COX-2 is implicated in placental development and parturition, exposure to this mycotoxin poses a potential threat to pregnant women.

Phorbol 12-myristate 13-acetate promotes nuclear translocation of hepatic steroid response element binding protein-2.

Sterol regulatory element-binding protein (SREBP)-2 is a pivotal transcriptional factor in cholesterol metabolism. Factors interfering with the proper functioning of SREBP-2 potentially alter plasma lipid profiles. Phorbol 12-myristate 13-acetate (PMA), which is a common protein kinase C (PKC) activator, was shown to promote the post-translational processing and nuclear translocation of SREBP-2 in hepatic cells in the current study. Following SREBP-2 translocation, the transcripts of its target genes HMGCR and LDLR were upregulated as demonstrated by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Electrophoretic mobility shift assays (EMSA) also demonstrated an induced DNA-binding activity on the sterol response element (SRE) domain under PMA treatment. The increase of activated Srebp-2 without the concurrent induced mRNA expression was also observed in an animal model. As the expression of SREBP-2 was not increased by PMA, the activation of PKC was the focus of investigation. Specific PKC isozyme inhibition and overexpression supported that PKCß was responsible for the promoting effect. Further studies showed that the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinases (JNK), but not 5' adenosine monophosphate-activated protein kinase (AMPK), were the possible downstream signaling proteins of PKCß. In conclusion, this study illustrated that PKCß increased SREBP-2 nuclear translocation in a pathway mediated by MEK/ERK and JNK, rather than the one dictated by AMPK. These results revealed a novel signaling target of PKCß in the liver cells.

Exposure to aflatoxin B1 in late gestation alters protein kinase C and apoptotic protein expression in murine placenta.

Mycotoxins are chemicals with diverse toxicities that are produced by fungi. Aflatoxin B1 is commonly found in plant food, and is generally regarded as one of the most toxic mycotoxins. In the present study, pregnant ICR mice were given p.o. daily doses of aflatoxin B1 at 0, 0.05, 0.5, 5mg/kg for 4days (from E13.5 to E16.5). Compared to the control group, time of delivery was shortened and low birth weight was induced in mice treated with 0.5 and 5mg aflatoxin B1/kg, respectively. Placental tissue isolated from pregnant mice at E17.5 showed that the mRNA expression of crh was increased in aflatoxin-treated groups. This upregulation might signify premature delivery. Further analysis indicated that Pkc proteins were activated and Bcl-2 was reduced in the placental tissue of the aflatoxin-treated groups. Reduction of the anti-apoptotic proteins, on the other hand, might affect the morphorgenesis and maintenance of the placenta.

The Flavone Luteolin Suppresses SREBP-2 Expression and Post-Translational Activation in Hepatic Cells.

High blood cholesterol has been associated with cardiovascular diseases. The enzyme HMG CoA reductase (HMGCR) is responsible for cholesterol synthesis, and inhibitors of this enzyme (statins) have been used clinically to control blood cholesterol. Sterol regulatory element binding protein (SREBP) -2 is a key transcription factor in cholesterol metabolism, and HMGCR is a target gene of SREBP-2. Attenuating SREBP-2 activity could potentially minimize the expression of HMGCR. Luteolin is a flavone that is commonly detected in plant foods. In the present study, Luteolin suppressed the expression of SREBP-2 at concentrations as low as 1 µM in the hepatic cell lines WRL and HepG2. This flavone also prevented the nuclear translocation of SREBP-2. Post-translational processing of SREBP-2 protein was required for nuclear translocation. Luteolin partially blocked this activation route through increased AMP kinase (AMPK) activation. At the transcriptional level, the mRNA and protein expression of SREBP-2 were reduced through luteolin. A reporter gene assay also verified that the transcription of SREBF2 was weakened in response to this flavone. The reduced expression and protein processing of SREBP-2 resulted in decreased nuclear translocation. Thus, the transcription of HMGCR was also decreased after luteolin treatment. In summary, the results of the present study showed that luteolin modulates HMGCR transcription by decreasing the expression and nuclear translocation of SREBP-2.

Aflatoxin B1 augments the synthesis of corticotropin releasing hormone in JEG-3 placental cells.

Aflatoxins pose a major threat to food safety. These toxins are classified as hepatocarcinogens; however, their effect on the other tissues is unclear. During pregnancy, the fetus and placental tissues are especially sensitive to toxin exposure. In the present study aflatoxin B1 was found to induce the mRNA expression of corticotrophin-releasing hormone (CRH) in placental cells. A corresponding increase in CRH peptide in the culture medium was also observed. Since signal transduction pathways have been described previously in the control of CRH transcription, the status of protein kinase Cs (PKCs) and mitogen-activated protein kinases (MAPKs) were determined by Western analysis. In the aflatoxin B1-treated cultures, PKC α/ßII/δ and ERK-1/2 were activated. As the PKC inhibitor bisindolylmaleimide I and the ERK inhibitor PD98059 could revert the induced CRH expression, the pathways dictated by PKC and ERK were likely involved in the transcriptional regulation. Electrophoretic mobility shift assay showed that C/EBP could be the ultimate activated transcription factor. Taken together, this study demonstrated that aflatoxin B1 could increase the parturition-related placental hormone in vitro. These findings might have significant implications for public health.

The flavone apigenin blocks nuclear translocation of sterol regulatory element-binding protein-2 in the hepatic cells WRL-68.

Sterol regulatory element-binding protein-2 (SREBP-2) is a pivotal transcriptional factor in cholesterol metabolism. Factors interfering with the proper functioning of SREBP-2 potentially alter plasma lipid concentrations. Consuming fruits and vegetables is associated with beneficial plasma lipid profile. The mechanism by which plant foods induce desirable lipid changes remains unclear. Apigenin, a common plant food flavonoid, was shown to modulate the nuclear translocation of SREBP-2 in the hepatic cells WRL-68 in the present study. The processing of SREBP-2 protein occurred after translation, and apigenin blocked this activation route. Further examination indicated that AMP-activated protein kinase (AMPK) was activated by the flavone, and co-administrating the AMPK-specific inhibitor compound C could release the blockage. Reporter gene assay revealed that the transactivation of sterol responsive element (SRE)-containing 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) promoter was suppressed by the flavone. Similarly, electromobility shift assay result also demonstrated a reduced DNA-binding activity on the SRE domain under the same treatment. The reduced transactivity and DNA-binding activity could be attributed to a decreased amount of SREBP-2 translocating from cytosol to nucleus as depicted by confocal microscopy. Quantitative RT-PCR assay demonstrated that the transcription of HMGCR followed the same pattern of SREBP-2 translocation. In summary, the present study showed that apigenin prevented SREBP-2 translocation and reduced the downstream gene HMGCR transcription. The minimum effective dosage should be achievable in the form of functional food consumption or dietary supplementation.

The licorice flavonoid isoliquiritigenin reduces DNA-binding activity of AhR in MCF-7 cells.

Licorice is derived from the rhizomes of Glycyrrhiza glabra. It has been used for confectioneries or culinary purposes. The rhizomes contain many flavonoidal compounds that have been shown to be biologically active. In the present study, effect of the licorice flavonoid isoliquiritigenin (ILN) on polycyclic aromatic hydrocarbon (PAH)-induced XRE transactivation and the downstream expression were investigated in MCF-7 cells. The environmental toxicant PAHs are pro-carcinogens and are biotransformed into their ultimate genotoxic structures by cytochrome P450 (CYP) 1 enzymes. Reporter gene assay revealed that ILN reduced XRE transactivation triggered by 7,12-dimethylbenz[α]anthracene (DMBA) or 2,3,7,8-Tetrachlorodibenzodioxin (TCDD). Our EMSA results also demonstrated that the flavonoid diminished DMBA-induced XRE binding. The reduced transactivation could be the result of a decreased amount of AhR translocating from cytosol to nucleus as shown in Western analysis. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that expressions of genes with XRE-containing promoters, including CYP1A1, 1A2, and 1B1, followed the same pattern of XRE transactivation. The present study illustrated that ILN might downregulate PAH-induced expressions through antagonizing AhR translocation.