Coffee and its chemopreventive components Kahweol and Cafestol increase the activity of O6-methylguanine-DNA methyltransferase in rat liver—comparison with phase II xenobiotic metabolism

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Abstract

A lower rate of colon cancer was observed in consumers of coffee with a high content of the diterpenes Kahweol and Cafestol (K/C). In animal models, K/C have been found to protect against the mutagenic/carcinogenic effects of compounds such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), aflatoxin B1, and 7,12-dimethylbenz[a]anthracene. Thus far, such chemoprotection by K/C has been attributed to modifications of xenobiotic metabolism, e.g. enhanced detoxification by UDP-glucuronosyltransferase (UDPGT) and/or glutathione transferase (GST). In the present study, we investigated the potential of several coffee-related treatments (K/C [1:1], Cafestol-alone, Turkish coffee) to modify the expression level of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) which is involved in the reversal of the precarcinogenic DNA damage O6-alkylguanine induced by alkylating agents. The results show that, in the male F344 rat, K/C and Cafestol increase hepatic MGMT in a dose-dependent manner up to a maximum of 2.6-fold at 0.122% K/C in the feed. Turkish coffee led to enhancements of up to 16%, the more moderate increase being associated with the lower estimated K/C intake through the beverage. In the livers of the rats receiving Turkish coffee, we also found 10–30% increases in several GST-related parameters (overall GST, GST-π, glutathione, γ-glutamylcysteine-synthetase) and a two-fold increase in UDPGT activity. Dose–response studies with K/C revealed that MGMT increased in parallel with three of the four GST-related parameters whereas the dose–response curves of UDPGT and of GST-π activity displayed a steeper slope. Increased expression level of MGMT may extend the antimutagenic/anticarcinogenic potential of coffee components to protection against DNA alkylating agents.

Introduction

Kahweol and Cafestol (K/C) are two diterpenes that are contained in coffee beans and rather high amounts may also be present in coffee as a beverage [1], [2]. Concentrations of up to 90 and 17 mg/l each have been found in unfiltered Turkish and espresso coffee, respectively [1]. Interestingly, a lower rate of colon cancer, one of the most frequent cancers in the western world, has been observed in consumers of coffees with a high K/C content [3], [4]. This finding may be partially explicable by the association of colon cancer with the relevant exposure of humans to the cooked food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP) and other heterocyclic aromatic amines [5]. Pretreatment of rats with a 1:1 mixture of K/C palmitates caused a considerable inhibition of PhIP-related genotoxicity, i.e. the formation of PhIP-DNA adducts, in the colon and other organs of these animals [6]. K/C was furthermore shown to exert protection against the mutagenicity and tumorigenicity of the mycotoxin aflatoxin B1 (AFB1) in rat liver preparations [7] and of the polyaromatic hydrocarbon 7,12-dimethylbenz[a]anthracene in the buccal pouch of the hamster [8]. Thus, the chemoprotective potential of K/C is suggested to concern a rather wide range of substances.

The antimutagenic and anticarcinogenic properties of K/C have thus far been primarily related to the beneficial modifications of xenobiotic metabolism that K/C has been observed to cause in the rodent. Such effects include reduced activation of mutagens/carcinogens, e.g. by inhibition of cytochrome P450 enzymes [7], [9] (Huber et al., in preparation) and N-acetyltransferase (Huber, Kadlubar et al., in preparation), as well as their enhanced detoxification. Important carcinogen-detoxifying enzyme systems known to be stimulated by K/C are glutathione transferase (GST) [6], [7], [9], [10], [11], [12] and UDP-glucuronosyl transferase (UDPGT) [12]. The coffee components were reported to enhance most of the various enzyme sub-families into which both GST and UDPGT are subdivided such as GST-α, GST-μ, GST-π, and GST-θ in case of GST and UGT1 and UGT2 in case of UDPGT. Also, K/C increased the levels of glutathione (GSH), the co-factor of GST-related detoxification, and γ-glutamylcysteine-synthetase (GCS), the limiting enzyme of GSH synthesis [13], [14].

In view of the significant effect of K/C on xenobiotic metabolism the question arises whether chemoprotection by K/C may also involve effects that are independent of the metabolism of the native mutagen/carcinogen. Likewise, it is unknown whether K/C treatment remains beneficial even after the occurrence of initial DNA damage. Therefore, in the present study, we investigated the influence of K/C on DNA repair as a possible contribution to the chemoprotective potential. We focused on O6-methylguanine-DNA methyltransferase (MGMT) which repairs O6-methylguanine, a DNA lesion that was found to be highly associated with mutagenicity upon exposure to alkylating xenobiotics such as N-nitrosamines, N-nitrosureas, and azoxymethane [15], [16]. MGMT also repairs larger O6-alkylguanine adducts as well as O4-methylthymine. In several studies, transgenic mice overexpressing MGMT were shown to be less susceptible to xenobiotic-induced tumorigenesis as compared to wild-type animals [17], [18], [19], [20], [21], [22], [23]. On the other hand, xenobiotic-induced tumorigenesis was increased in MGMT knock-out mice [24], [25], [26], and specific K-ras mutations in the human colon were more frequent under conditions of silenced or lowered MGMT [27], [28], [29]. Such findings emphasize the possibility that MGMT induction by a nutrional or life-style-related component might contribute to the chemoprevention of cancer.

The present study involved treatments of male F344 rats with several doses of K/C or Cafestol-alone in the feed and with Turkish coffee in the drinking water. In order to compare the degree and dose range of potential effects of K/C on MGMT with those on phase II xenobiotic metabolism, we also measured several GST-related parameters (overall GST-activity, GST-π-activity, GSH content, GCS activity) and UDPGT activity in the rats receiving Turkish coffee and K/C. The effects of any of these treatments on MGMT and of Turkish coffee on the investigated parameters of hepatic phase II metabolism have not been studied thus far.

Section snippets

Chemicals

K/C (1:1, i.e. 47% Cafestol [CAS 469-83-0], 47% Kahweol [CAS 6894-43-5], 5% isomeric derivatives) and Cafestol (purity > 95%) were a kind gift from Robert J. Turesky of Nestlé (Lausanne, Switzerland). Turkish coffee was prepared from a commercially available Arabica product named “Regio-Der Beste” distributed by SPAR Österreichische Warenhandelsgesellschaft (Salzburg, Austria). All other reagents used in the study were of the highest purity available (p.a. or HPLC grade if required) and were

Increase in MGMT level upon treatment with Kahweol and Cafestol and Turkish coffee

As displayed in Fig. 1A, treatment with a high-dose of K/C resulted in a statistically significant 2.6-fold increase in hepatic MGMT as compared to untreated controls. This prompted us to analyze the dose–response relationship of the effect which showed that hepatic MGMT was enhanced by both K/C and Cafestol-alone in a clearly dose-dependent manner (Fig. 1B). The increases were significant with all K/C-doses except the lowest one and with Cafestol doses≥0.05%. While enhancements in the lower

Discussion

Our study demonstrates the capability of the coffee compounds K/C to increase the hepatic activity of MGMT in a dose-dependent manner. The associated dose–response curve was quantitatively similar to those of the K/C effects on overall GST, GSH, and GCS, and the reaction of the same three parameters to Turkish coffee resembled that of MGMT as well. It remains presently unknown whether these similarities involve regulation by a common molecular mechanism. UDPGT displayed the strongest increases

Acknowledgements

This work was in part supported by the Hochschuljubiläumsstiftung der Stadt Wien (University Anniversary Foundation of the City of Vienna) in Austria and by DFG (SFB 519/B4).

References (77)

  • F Laval

    Induction of proteins involved in the repair of alkylated bases in mammalian cells by DNA-damaging agents

    Mutat. Res.

    (1990)
  • F Laval

    Increase of O6-methylguanine-DNA-methyltransferase and N3-methyladenine glycosylase RNA transcripts in rat hepatoma cells treated with DNA-damaging agents

    Biochem. Biophys. Res. Commun.

    (1991)
  • G Fritz et al.

    Stress factors affecting expression of O6-methylguanine-DNA methyltransferase mRNA in rat hepatoma cells

    Biochim. Biophys. Acta

    (1992)
  • J.M Pezzuto et al.

    Characterization of bacterial mutagenicity mediated by 13-hydroxy-ent-kaurenoic acid (steviol) and several structurally-related derivatives and evaluation of potential to induce glutathione S-transferase in mice

    Mutat. Res.

    (1986)
  • R Urgert et al.

    Levels of the cholesterol-elevating diterpenes Cafestol and Kahweol in various coffee brews

    J. Agric. Food Chem.

    (1995)
  • E Giovannucci

    Meta-analysis of coffee consumption and risk of colorectal cancer

    Am. J. Epidemiol.

    (1998)
  • IARC, Coffee, Tea, Mate, Methylxanthines and Methylglyoxal, IARC Monographs, WHO, Lyon, France,...
  • R.H Adamson et al.

    Extrapolation of heterocyclic amine carcinogenesis data from rodents and nonhuman primates to humans

    Arch. Toxicol.

    (1996)
  • C Cavin et al.

    The coffee-specific diterpenes Cafestol and Kahweol protect against aflatoxin B1-induced genotoxicity through a dual mechanism

    Carcinogenesis

    (1998)
  • E.G Miller et al.

    Kahweol and Cafestol: inhibitors of hamster buccal pouch carcinogenesis

    Nutr. Cancer

    (1991)
  • B Schilter et al.

    Placental glutathione S-transferase (GST-P) induction as a potential mechanism for the anti-carcinogenic effect of the coffee-specific components Cafestol and Kahweol

    Carcinogenesis

    (1996)
  • L.K Lam et al.

    Effects of derivatives of Kahweol and Cafestol on the activity of glutathione S-transferase in mice

    J. Med. Chem.

    (1987)
  • W.W Huber et al.

    Enhancement of the chemoprotective enzymes glucuronosyl transferase and glutathione transferase by the coffee components Kahweol and Cafestol in specific organs of the rat

    Arch. Toxicol.

    (2002)
  • W.W Huber et al.

    The coffee components Kahweol and Cafestol induce γ-glutamylcysteine synthetase, the rate limiting enzyme of chemoprotective glutathione synthesis, in several organs of the rat

    Arch. Toxicol.

    (2002)
  • M McMahon et al.

    The Cap’n’Collar basic leucine zipper transcription factor Nrf2 (NF-E2 p45-related factor 2) controls both constitutive and inducible expression of intestinal detoxification and glutathione biosynthetic enzymes

    Cancer Res.

    (2001)
  • A.E Pegg et al.

    Inactivation of human O6-alkylguanine-DNA alkyltransferase by modified oligodeoxyribonucleotides containing O6-benzylguanine

    J. Pharmacol. Exp. Ther.

    (2001)
  • L.L Dumenco et al.

    Enhanced repair of O6-methylguanine DNA adducts in the liver of transgenic mice expressing the ada gene

    Cancer Res.

    (1991)
  • L.L Dumenco et al.

    The prevention of thymic lymphomas in transgenic mice by human O6-alkylguanine-DNA alkyltransferase

    Science

    (1993)
  • K Becker et al.

    Targeted expression of human O6-methylguanine-DNA methyltransferase (MGMT) in transgenic mice protects against tumor initiation in two-stage skin carcinogenesis

    Cancer Res.

    (1996)
  • K Becker et al.

    The DNA repair protein O6-methylguanine-DNA methyltransferase protects against skin tumor formation induced by antineoplastic chloroethylnitrosourea

    Cancer Res.

    (1997)
  • L Liu et al.

    Reduced lung tumorigenesis in human methylguanine DNA methyltransferase transgenic mice achieved by expression of transgene within the target cell

    Carcinogenesis

    (1999)
  • N.H Zaidi et al.

    Transgenic expression of human MGMT protects against azoxymethane-induced aberrant crypt foci and G to A mutations in the K-ras oncogene of mouse colon

    Carcinogenesis

    (1995)
  • Y Nakatsuru et al.

    O6-Methylguanine-DNA methyltransferase protects against nitrosamine-induced hepatocarcinogenesis

    Proc. Natl. Acad. Sci. U.S.A.

    (1993)
  • K Sakumi et al.

    Methylnitrosourea-induced tumorigenesis in MGMT gene knockout mice

    Cancer Res.

    (1997)
  • T Iwakuma et al.

    High incidence of nitrosamine-induced tumorigenesis in mice lacking DNA repair methyltransferase

    Carcinogenesis

    (1997)
  • H Kawate et al.

    Separation of killing and tumorigenic effects of an alkylating agent in mice defective in two of the DNA repair genes

    Proc. Natl. Acad. Sci. U.S.A.

    (1998)
  • M Esteller et al.

    Inactivation of the DNA repair gene O6-methylguanine-DNA methyltransferase by promoter hypermethylation is associated with G to A mutations in K-ras in colorectal tumorigenesis

    Cancer Res.

    (2000)
  • P.E Jackson et al.

    Low O6-alkylguanine DNA-alkyltransferase activity in normal colorectal tissue is associated with colorectal tumours containing a GC → AT transition in the K-ras oncogene

    Carcinogenesis

    (1997)
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