Induction of cytochromes P450 1A1 and 1A2 by tanshinones in human HepG2 hepatoma cell line

Interaction between Traditional Chinese Medicine and Anticoagulant/Antiplatelet Drugs

Background:

Traditional Chinese medicine (TCM) has been used for medical purposes since the ancient time and has gradually gained recognition worldwide. Nowadays, patients with thrombus presiding to anticoagulant/ antiplatelet drugs prefer taking TCM. However, an increasing number of studies on herb–drug interactions have been shown. Nevertheless, findings are frequently conflicting and vague. In this review, we discuss the herb–drug interactions between TCM and anticoagulant/antiplatelet drugs to provide guidance on concomitant ingestion with anticoagulant/antiplatelet drugs.

Methods:

We undertook a structured search of medicine and drug databases for peer-reviewed literature using focused review questions.

Results:

Danshen, Ginkgo, Ginger, H. Perforatum, SMY and Puerarin injection had directional regulation effects on the efficacy of anticoagulant drugs by altering the CYPs, pharmacokinetic indexs and hemorheological parameters. H. Perforatum inhibited the efficacy of Clopidogrel by enhancing the CYP3A4 activity and Ginkgo increased the efficacy of Ticlopidine. Additionally, Renshen, the formulae except SMY and injections except Puerarin injection could increase or decrease the efficacy of anticoagulant/antiplatelet drugs via regulating the CYPs, platelet aggregation, hemorheological parameters and others.

Conclusion:

Some cases have reported that TCMs may increase the bleeding risk or has no effect on coagulation when anticoagulant/antiplatelet drugs are concurrently used. However, pharmacokinetic studies have presented either consistent or slightly varying results. So it is difficult to ascertain whether the concurrent use of TCM may increase or reduce the pharmacologic effects of anticoagulant/antiplatelet drugs with adverse reactions. Therefore, herb–drug interactions of TCM and anticoagulant/antiplatelet drugs should be further explored and defined.

The biosynthesis of phenolic acids is positively regulated by the JA-responsive transcription factor ERF115 in Salvia miltiorrhiza

Phenolic acids are important secondary metabolites produced in the Chinese medicinal plant Salvia miltiorrhiza, but little is known about the transcription factors involved in the regulation of tanshinone and phenolic acid biosynthesis. Here, a novel AP2/ERF transcription factor SmERF115 was isolated and functionally characterized. SmERF115 was most responsive to methyl jasmonate (MeJA) treatment and was localized in the nucleus. The phenolic acid production was increased in SmERF115-overexpressing hairy roots, but with a decrease in tanshinone content. In contrast, silencing of SmERF115 reduced the phenolic acid level, but increased tanshinone content. The expression of the key biosynthetic gene SmRAS1 was up-regulated in SmERF115 overexpression lines but was down-regulated in SmERF115-RNAi lines. Yeast one-hybrid (Y1H) assay and EMSA showed that SmERF115 directly binds to the promoter of SmRAS1, while dual-luciferase assays showed that SmERF115 could activate expression of SmRAS1 in vivo. Furthermore, global transcriptomic analysis by RNA sequencing revealed that expression of other genes such as PAL3, 4CL5, TAT3, and RAS4 was also increased in the overexpression line, implying that they were potentially involved in the SmERF115-mediated pathway. Our data show that SmERF115 is a positive regulator of phenolic acid biosynthesis, and may be a potential target for further metabolic engineering of phenolic acid biosynthesis in S. miltiorrhiza.

Charactering the metabolism of cryptotanshinone by human P450 enzymes and uridine diphosphate glucuronosyltransferases in vitro

Cryptotanshinone (CT) is the main active component in the root of Salvia miltiorrhiza Bunge (SMB) that displays antibacterial, anti-inflammatory and anticancer activities. In this study, we characterized phase I and phase II metabolism of CT in human liver microsomes in vitro and identified the metabolic enzymes (CYPs and UGTs) involved. The metabolites of CT generated by CYPs were detected using LC-MS/MS and the CYP subtypes involved in the metabolic reactions were identified using chemical inhibitors of CYP enzymes and recombinant human CYP enzymes (CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4). Glucuronidation of CT was also examined, and the UGT subtypes involved in the metabolic reactions were identified using recombinant human UGT enzymes (1A1, 1A3, 1A4, 1A5, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15 and 2B17). After adding NADPH to the human liver microsomes incubation system, CT was transformed into 6 main dehydrogenation and hydroxylation metabolites. CYP2A6, CYP3A4 and CYP2C19 were the major contributors to the transformation of its hydroxylation metabolites. CYP2C19, CYP1A2 and CYP3A4 were the major contributors to the transformation of its hydrogenation metabolites in human liver microsomes. This study showed that the metabolites at m/z of 473 were mediated by UGT1A9 and that the metabolites at m/z of 489 were mediated by UGT2B7 and UGT2B4. CT was extensively metabolized by UGTs following metabolism by CYPs in the liver.

Salvia miltiorrhiza Roots against Cardiovascular Disease: Consideration of Herb-Drug Interactions

Salvia miltiorrhiza root (Danshen) is widely used in Asia for its cardiovascular benefits and contains both hydrophilic phenolic acids and lipophilic tanshinones, which are believed to be responsible for its therapeutic efficacy. This review summarized the effects of these bioactive components from S. miltiorrhiza roots on pharmacokinetics of comedicated drugs with mechanic insights regarding alterations of protein binding, enzyme activity, and transporter activity based on the published data stemming from both in vitro and in vivo human studies. In vitro studies indicated that cytochrome P450 (CYP450), carboxylesterase enzyme, catechol-O-methyltransferase, organic anion transporter 1 (OAT1) and OAT3, and P-glycoprotein were the major targets involved in S. miltiorrhiza-drug interactions. Lipophilic tanshinones had much more potent inhibitory effects towards CYPs activities compared to hydrophilic phenolic acids, evidenced by much lower K_i values of the former. Clinical S. miltiorrhiza-drug interaction studies were mainly conducted using CYP1A2 and CYP3A4 probe substrates. In addition, the effects of coexisting components on the pharmacokinetic behaviors of those noted bioactive compounds were also included herein.

Omeprazole Alleviates Aristolochia manshuriensis Kom-Induced Acute Nephrotoxicity

Aristolochia manshuriensis Kom (AMK) is a member of the Aristolochiaceae family and is a well-known cause of aristolochic acid (AA) nephropathy. In this study, we investigated the potential of omeprazole (OM) to alleviate AMK-induced nephrotoxicity. We found that OM reduced mouse mortality caused by AMK and attenuated AMK-induced acute nephrotoxicity in rats. OM enhanced hepatic Cyp 1a1/2 and renal Cyp 1a1 expression in rats, as well as CYP 1A1 expression in human renal tubular epithelial cells (HKCs). HKCs with ectopic CYP 1A1 expression were more tolerant to AA than the control cells. Therefore, OM may alleviate AMK-mediated acute nephrotoxicity through induction of CYP 1A1. We suggest that the coadministration of OM might be beneficial for reducing of AA-induced nephrotoxicity.

Autologous NeoHep Derived from Chronic Hepatitis B Virus Patients' Blood Monocytes by Upregulation of c-MET Signaling

In view of the escalating need for autologous cell‐based therapy for treatment of liver diseases, a novel candidate has been explored in the present study. The monocytes isolated from hepatitis B surface antigen (HBsAg) nucleic acid test (NAT)‐positive (HNP) blood were differentiated to hepatocyte‐like cells (NeoHep) in vitro by a two‐step culture procedure. The excess neutrophils present in HNP blood were removed before setting up the culture. In the first step of culture, apoptotic cells were depleted and genes involved in hypoxia were induced, which was followed by the upregulation of genes involved in the c‐MET signaling pathway in the second step. The NeoHep were void of hepatitis B virus and showed expression of albumin, connexin 32, hepatocyte nuclear factor 4‐α, and functions such as albumin secretion and cytochrome P450 enzyme‐mediated detoxification of xenobiotics. The engraftment of NeoHep derived from HBsAg‐NAT‐positive blood monocytes in partially hepatectomized NOD.CB17‐Prkdc^scid/J mice liver and the subsequent secretion of human albumin and clotting factor VII activity in serum make NeoHep a promising candidate for cell‐based therapy. Stem Cells Translational Medicine2017;6:174–186

Radix Puerariae lobatae (Gegen) suppresses the anticoagulation effect of warfarin: a pharmacokinetic and pharmacodynamics study

Background

Radix Salvia miltiorrhiza (Danshen) and Radix Puerariae lobatae (Gegen) are used in Traditional Chinese Medicine to treat cardiovascular diseases. However, adverse herb-drug interactions were observed between warfarin and herbal remedies containing Danshen and Gegen. This study aims to investigate the pharmacokinetic and pharmacodynamic interactions between warfarin and the different components found in Danshen and Gegen.

Methods

Sixty Sprague–Dawley rats were used to investigate the effects of warfarin (0.2 mg/kg), Danshen (240 or 480 mg/kg) and Gegen (240 or 480 mg/kg) both in isolation and combination. The rats in the warfarin and Danshen/Gegen combination groups were given an oral dose of Danshen or Gegen 2 h after being given an oral dose of warfarin. After five consecutive days of treatment, the pharmacokinetic interactions between Danshen/Gegen and warfarin were investigated by simultaneously monitoring and comparing the cytochrome P450 (CYP) activities, mRNA and protein expression levels in the livers of the rats from the different treatment groups. The pharmacodynamic interactions were evaluated by monitoring and comparing the vitamin K epoxide reductase (VKOR) activities, mRNA and protein expression levels in the livers of rats from the different groups, as well as the thrombomodulin (TM) activities, mRNA and protein in the lungs of these animals. The rat plasma soluble thrombomodulin concentrations of the different treatment groups were also evaluated. Microsomes incubation, Real Time-Polymerase Chain Reaction and Western blot was applied respectively to study the activity, mRNA expression and protein expression of CYP, VKOR and TM.

Results

The activities and expression levels of the CYP and VKOR enzymes in the warfarin-Gegen combination groups increased by nearly 30 % (P = 0.02) compared with the warfarin-alone group, whereas those of TM decreased by almost 25 % (P = 0.02). The administration of Danshen did not lead to any changes in the activities or the expression levels of the CYP, VKOR or TM enzymes compared with those of the control group. Gegen induced several warfarin-metabolizing CYP enzymes and neutralized the effects of warfarin towards VKOR and TM.

Conclusion

Gegen, rather than Danshen at the same tested dosage, offsets the anticoagulant effects of warfarin by accelerating the phase I liver metabolism of warfarin, as well as increasing the activity, mRNA and protein expression of VKOR while decreasing those of TM.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-016-0078-9) contains supplementary material, which is available to authorized users.

Altered gene expression in HepG2 cells exposed to a methanolic coal dust extract

Exposure to coal dust has been associated with different chronic diseases and mortality risk. This airborne pollutant is produced during coal mining and transport activities, generating environmental and human toxicity. The aim of this study was to determine the effects of a coal dust methanolic extract on HepG2, a human liver hepatocellular carcinoma cell line. Cells were exposed to 5-100ppm methanolic coal extract for 12h, using DMSO as control. MTT and comet assays were used for the evaluation of cytotoxicity and genotoxicity, respectively. Real time PCR was utilized to quantify relative expression of genes related to oxidative stress, xenobiotic metabolism and DNA damage. Coal extract concentrations did not induce significant changes in HepG2 cell viability after 12h exposure; however, 50 and 100ppm of the coal extract produced a significant increase in genetic damage index with respect to negative control. Compared to vehicle control, mRNA CYP1A1 (up to 163-fold), NQO1 (up to 4.7-fold), and GADD45B (up to 4.7-fold) were up regulated, whereas PRDX1, SOD, CAT, GPX1, XPA, ERCC1 and APEX1 remained unaltered. This expression profile suggests that cells exposed to coal dust extract shows aryl hydrocarbon receptor-mediated alterations, changes in cellular oxidative status, and genotoxic effects. These findings share some similarities with those observed in liver of mice captured near coal mining areas, and add evidence that living around these industrial operations may be negatively impacting the biota and human health.

HepG2 cells as an in vitro model for evaluation of cytochrome P450 induction by xenobiotics

Although various in vitro assays have been developed to evaluate the cytochrome P450 (CYP)-inducing potential of drug candidates, there is a continuing need for the development of a reliable model in drug discovery. The objective of the present study was to compare CYP induction by chemicals in HepG2 cells with Huh7, NKNT-3, and reverted NKNT-3 cells. HepG2 cells showed more similarity to human liver than the other cell lines in comparisons of the expression of cellular proteins. In evaluation of basal CYP activity, Huh7 cells exhibited the highest CYP1A2 and CYP3A4 activity, and HepG2 cells showed the highest CYP2B6 activity. The inducibility of CYP1A2, CYP2B6, and CYP3A4 by prototypical inducers was determined using enzyme assay, immunoblot analysis, and real-time PCR. Among the cells tested, HepG2 cells were highly responsive to CYP inducers, such as 3-methylcholanthrene for CYP1A2 and phenobarbital for CYP2B6 and CYP3A4. Moreover, HepG2 cells were responsive to various CYP1A2, CYP2B6, and CYP3A4 inducers as determined using fluorogenic and LC-MS/MS substrates. Thus, HepG2 cells may be comparable to human hepatocytes for the evaluation of CYP induction or slightly less sensitive. These results suggest HepG2 cells as a cell-based model in screening for CYP inducers in drug discovery.

Induction of liver cytochrome P450s by Danshen-Gegen formula is the leading cause for its pharmacokinetic interactions with warfarin

ETHNOPHARMACOLOGICAL RELEVANCE

Although the increased usage of herbal medicine leading to herb-drug interactions is well reported, the mechanism of such interactions between herbal medicines with conventionally prescribed drugs such as warfarin is not yet fully understood. Our previous rat in vivo study demonstrated that co-administration of Danshen-Gegen Formula (DGF), a Radix Salvia miltiorrhiza (Danshen) and Radix Puerariae lobatae (Gegen) containing Chinese medicine formula recently developed for the treatment of cardiovascular disease, with warfarin could cause significant herb-drug interactions. The current study aims to explore the pharmacokinetics-based mechanism of the DGF-warfarin interactions during absorption, distribution and metabolism processes.

MATERIALS AND METHODS

Caco-2 cell monolayer model and rat in situ intestinal perfusion model were used to study the DGF-warfarin interactions during the intestinal absorption processes. Male Sprague-Dawley rats were orally administered warfarin in presence and absence of DGF for consecutive 5 days. The microsomal activity and expression of the liver CYP isozymes were determined and compared among different treatment groups. Blood from the rats administered DGF was employed to evaluate effects of DGF on the plasma protein binding of warfarin.

RESULTS

Absorption studies demonstrated that DGF could potentially increase the intestinal absorption of warfarin (32% and 75% increase of warfarin Papp in Caco-2 and intestinal perfusion models, respectively) via altering the regional pH environment in GI tract. DGF administration could lead to significant increase in liver microsomal activity and mRNA expression of CYP1A1 and CYP2B1, indicating the potential induction on the liver metabolism of warfarin by DGF. Moreover, it has been proven by ex vivo study that the single-dose administration of DGF could decrease the protein binding of warfarin in plasma by at least 11.6%.

CONCLUSION

Collectively, current study demonstrated that DGF could significantly induce the liver phase I metabolism of warfarin, and to a less extent, potentially increase the intestinal absorption and decrease the plasma protein binding of warfarin. The inductive effects of DGF on the liver phase I metabolism of warfarin may be dominantly responsible for the DGF-warfarin pharmacokinetics interactions.

Cytochrome P450 family 1 inhibitors and structure-activity relationships

With the widespread use of O-alkoxyresorufin dealkylation assays since the 1990s, thousands of inhibitors of cytochrome P450 family 1 enzymes (P450s 1A1, 1A2, and 1B1) have been identified and studied. Generally, planar polycyclic molecules such as polycyclic aromatic hydrocarbons, stilbenoids, and flavonoids are considered to potentially be effective inhibitors of these enzymes, however, the details of the structure-activity relationships and selectivity of these inhibitors are still ambiguous. In this review, we thoroughly discuss the selectivity of many representative P450 family 1 inhibitors reported in the past 20 years through a meta-analysis.

Antioxidant and anticancer activity of Artemisia princeps var. orientalis extract in HepG2 and Hep3B hepatocellular carcinoma cells

OBJECTIVE

The aim of the present study was to investigate antioxidant and the anticancerigen activity of a methanol extract from Artemisia princeps var. orientalis (APME), a well-known traditional herbal medicine in Asia, in hepatocellular cancer cells.

METHODS

To evaluate the antioxidant activity of APME, reactive oxygen species (ROS) and the antioxidant enzymes, superoxide dismutase (SOD) and catalase were investigated in HepG2 cells exposed to APME (5, 100, and 200 µg/mL) for 72 h. Then, to evaluate the anticancer activity of APME, we investigated the proliferation and apoptosis induction of HepG2 and Hep3B cells exposed to APME (1-200 µg/mL) for 24, 48, and 72 h.

RESULTS

APME dose-dependently reduced the generation of ROS in the presence of H2O2 compared with control cells. Furthermore, it increased catalase and SOD activity. Moreover, APME inhibited cell proliferation in a dose- and time-dependent manner, but at concentrations lower than 100 µg/mL, the inhibition was less dose-dependent than time-dependent. HepG2 and Hep3B cells exposed to 5, 100, and 200 µg/mL APME for 72 h underwent cell cycle arrest and apoptosis. Exposure to APME resulted in a significant increase in the number of cells in G1 phase and a decrease in the G2/M phase cell population. In addition, APME induced P53 expression of HepG2 cells in a dose-dependent manner, and played a role in the downregulation of Bcl-2 and upregulation of Bax in both HepG2 and Hep3B cells.

CONCLUSIONS

These results indicate the potential role of APME as an antioxidant and anticancerigen agent in hepatocarcinoma cell lines.

Tanshinone I protects mice from aristolochic acid I-induced kidney injury by induction of CYP1A

Hepatic CYP1A especially CYP1A2 plays an important role in the reduction of aristolochic acid I (AAI) nephrotoxicity. In this study, we investigated the effects of tanshinone I, a strong inducer of Cyp1a, on the nephrotoxicity induced by AAI. Histopathology and blood biochemistry assays showed that tanshinone I could reduce AAI-induced acute kidney injury. Pharmacokinetics analysis revealed that tanshinone I markedly decreased AUC of AAI in plasma and the content of AAI in both liver and kidney, indicating the enhancement of AAI metabolism. Real-time PCR and Western blot analysis confirmed that tanshinone I effectively increased the mRNA and protein levels of hepatic CYP1A1 and CYP1A2 in vivo. Luciferase assay showed that tanshinone I strongly increased the transcriptional activity of CYP1A1 and CYP1A2 in the similar extent. In summary, our data suggested that tanshinone I facilitated the metabolism of AAI and prevented AAI-induced kidney injury by induction of hepatic CYP1A 1/2 in vivo.

The antioxidant activity of daidzein metabolites, O‑desmethylangolensin and equol, in HepG2 cells

Daidzein and its glycoside form daidzin, are known to have potential health benefits and are metabolized to O‑desmethylangolensin (O‑DMA) and equol following consumption. In the current study, the antioxidant activity and cytotoxicity of O‑DMA, equol, daidzein and daidzin was investigated and their effects on HepG2 human hepatocelluar carcinoma cells were compared. For cytotoxicity assays, lactose dehydrogenase (LDH) release and 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide‑based cell viability, cells were exposed to various concentrations of each compound (5‑200 µM) for 24, 48 or 72 h. O‑DMA and equol did not affect LDH release, but higher concentrations (<75 µM) showed inhibition of cell growth. By contrast, daidzein and daidzin (200 µM) increased LDH release and cell growth. All compounds stimulated catalase and total superoxide dismutase (SOD) (CuZn‑ and Mn‑SOD) activity, and mRNA and protein expression. This phenomenon was most pronounced for O‑DMA and equol, as their effects were similar. These data suggested that O‑DMA and equol possess greater antioxidant properties compared with daidzein and may, thus, be beneficial for human health.

Modulation of carcinogen-metabolizing cytochromes P450 by phytochemicals in humans

INTRODUCTION

Cytochrome P450 (CYP) families 1 - 3, besides oxidizing environmental and dietary chemicals, leading to their elimination, catalyze the bioactivation of exogenous as well as endogenous carcinogens. Phytochemicals, particularly those which are active food components, were shown to be able to affect specific CYP expression and/or activity in animal models and in human in vitro systems. Human intervention studies involving healthy volunteers were also performed. This review describes human CYP modulation by naturally occurring phytochemicals which can not only affect carcinogen metabolism in humans, but also change the drug response.

AREAS COVERED

The authors present an overview of carcinogens metabolizing human CYP modulation in different model systems as well as studies on human dietary intervention. Furthermore, the authors provide examples of the phytochemicals that affect CYP expression and activity.

EXPERT OPINION

CYP, which are involved in carcinogen activation, can metabolize a range of substrates and inducing CYP by one substrate may also increase the metabolism of another. The ultimate proof of the efficacy of CYP modulation strategy for chemoprevention may be provided by clinical trials involving risk populations, which are difficult to perform. The new human-like models are highly desired for the study of modulation of carcinogen-metabolizing CYP.

Pathway-focused bioassays and transcriptome analysis contribute to a better activity monitoring of complex herbal remedies

Background

Transcriptome analysis in combination with pathway-focused bioassays is suggested to be a helpful approach for gaining deeper insights into the complex mechanisms of action of herbal multicomponent preparations in living cells. The polyherbalism based concept of Tibetan and Ayurvedic medicine considers therapeutic efficacy through multi-target effects. A polyherbal Indo-Tibetan preparation, Padma 28, approved by the Swiss drug authorities (Swissmedic Nr. 58436), was applied to a more detailed dissection of mechanism of action in human hepatoma HepG2 cells. Cell-free and cell-based assays were employed to evaluate the antioxidant capacity. Genome-wide expression profiling was done by applying Human Genome U133 Plus 2.0 Affymetrix arrays. Pathway- and network-oriented analysis elucidated the affected biological processes. The results were validated using reporter gene assays and quantitative real-time PCR.

Results

To reveal the direct radical scavenging effects of the ethanolic extract of the Indo-Tibetan polyherbal remedy Padma 28, an in vitro oxygen radical absorbance capacity assay (ORAC) was employed, which resulted in a peroxyl-radical scavenging activity of 2006 ± 235 μmol TE/g. Furthermore, the antioxidant capacity of Padma 28 was analysed in living HepG2 cells, by measuring its scavenging potential against radical induced ROS. This formulation showed a considerable antioxidant capacity by significantly reducing ROS levels in a dose-dependent manner.

Integrated transcriptome analysis revealed a major influence on phase I and phase II detoxification and the oxidative stress response. Selected target genes, such as heme oxygenase 1, were validated in qPCR experiments. Network analysis showed 18 interrelated networks involved in important biological functions such as drug and bio-molecule metabolism, molecular transport and cellular communication. Some molecules are part of signaling cascades that are active during development and morphogenesis or are involved in pathological conditions and inflammatory response.

Conclusions

The identified molecular targets and pathways suggest several mechanisms that underlie the biological activity of the preparation. Although extrapolation of these findings to the in vivo situation is not possible, the results obtained might be the basis for further investigations and new hypotheses to be tested. This study demonstrates the potential of the combination of focused and unbiased research strategies in the mode of action analysis of multicomponent herbal mixtures.

Tanshinone I increases CYP1A2 protein expression and enzyme activity in primary rat hepatocytes

This study investigated the effects of Danshen and its active ingredients on the protein expression and enzymatic activity of CYP1A2 in primary rat hepatocytes. The ethanolic extract of Danshen roots (containing mainly tanshinones) inhibited CYP1A2-catalyzed phenacetin O-deethylation (IC(50)=24.6 μg/ml) in primary rat hepatocytes while the water extract containing mainly salvianolic acid B and danshenshu had no effect. Individual tanshinones such as cryptotanshinone, dihydrotanshinone, tanshinone IIA inhibited the CYP1A2-mediated metabolism with IC(50) values at 12.9, 17.4 and 31.9 μM, respectively. After 4-day treatment of the rat hepatocytes, the ethanolic extract of Danshen and tanshinone I increased rat CYP1A2 activity by 6.8- and 5.2-fold, respectively, with a concomitant up-regulation of CYP1A2 protein level by 13.5- and 6.5-fold, respectively. CYP1A2 induction correlated with the up-regulation of mRNA level of aryl hydrocarbon receptor (AhR), which suggested a positive feedback mechanism of tanshinone I-mediated CYP1A2 induction. A formulated Danshen pill (containing mainly danshensu and salvianolic acid B and the tanshinones) up-regulated CYP1A2 protein expression and enzyme activity, but danshensu and salvianolic acid B, when used individually, did not affect CYP1A2 activity. This study was the first report on the Janus action of the tanshinones on rat CYP1A2 activity.

Genotoxicity of 7H-dibenzo[c,g]carbazole and its tissue-specific derivatives in human hepatoma HepG2 cells is related to CYP1A1/1A2 expression

The goal of this study was to investigate the genotoxicity of 7H-dibenzo[c,g]carbazole (DBC), a ubiquitous environmental pollutant, and its methyl derivatives, 5,9-dimethylDBC (DiMeDBC), a strict hepatocarcinogen, and N-methylDBC (N-MeDBC), a specific sarcomagen in human hepatoma HepG2 cells, and to infer potential mechanisms underlying the biological activity of particular carcinogen. All dibenzocarbazoles, regardless the tissue specificity, induced significant DNA strand break levels and micronuclei in HepG2 cells; though a mitotic spindle dysfunction rather than a chromosome breakage was implicated in N-MeDBC-mediated micronucleus formation. While DBC and N-MeDBC produced stable DNA adducts followed with p53 protein phosphorylation at Ser-15, DiMeDBC failed. A significant increase in DNA strand breaks following incubation of exposed cells with a repair-specific endonuclease (Fpg protein) suggested that either oxidative DNA damage or unstable DNA-adducts might underlie DiMeDBC genotoxicity in human hepatoma cells. DiMeDBC and N-MeDBC increased substantially also the amount of CYP1A1/2 expression in HepG2 cells. Pretreatment of cells with substances affecting AhR-mediated CYP1A family of enzymes expression; however, diminished DiMeDBC and N-MeDBC genotoxicity. Our data clearly demonstrated differences in the mechanisms involved in the biological activity of DiMeDBC and N-MeDBC in human hepatoma cells; the genotoxicity of these DBC derivatives is closely related to CYP1A1/2 expression.