CYP1A1 and CYP2D6 polymorphism and risk of lung cancer in a North Indian population

This case–control study was conducted to examine the association between the CYP1A1 and CYP2D6 genotypes and lung cancer risk among North Indians. The estimated relative risk for lung cancer associated with the CYP1A1 Val/Val allele was 2.68, and was four-fold when cases with small cell lung cancer (SCLC) were considered alone. With regard to the metabolism of debrisoquine, no poor metabolizers were found amongst the subjects. The odds ratio of risk with the heterozygous extensive metabolizer (HEM) genotype was 1.5. However, in the presence of at least a single copy of the variant CYP1A1 MspI allele and the CYP2D6 HEM genotype, the risk was two-fold for squamous cell carcinoma (SQCC). When the CYP1A1 Val/Val and CYP2D6 HEM genotypes were taken together, the risk for SCLC was four-fold. Stratified analysis indicated an interaction between bidi smoking and variant CYP1A1 genotypes on the risk for SQCC and SCLC. Heavy smokers (Brinkman index>400) with Val/Val genotypes were at a very high risk of developing lung cancer (odds ratio 29.30, 95% confidence interval 2.42–355, p=0.008). Heavy smokers with CYP1A1 MspI (CYP1A1*1/2A or CYP1A1*2A/*2A) genotype had a seven-fold risk for SCLC compared with non-smokers. This study is the first to be carried out on a North Indian population, and, although small, suggests that CYP1A1 and CYP2D6 polymorphisms might have a role in determining the risk for lung cancer and should be investigated further.     

Analysis of CYP21A1P and the duplicated CYP21A2 genes

The RCCX module on chromosome 6p21.3 has 3 possible forms: monomodular, bimodular, and trimodular. Chromosomes with 4 RCCX modules are very rare. In the monomodule, most of the CYP21A1P genes do not exist. However, haplotypes of the RCCX module with more than one CYP21A2 gene were observed. Obviously, the gene located downstream of the XA gene can possibly include the CYP21A2 as well as the CYP21A1P gene.     

Characterization of human CYP1A1/1A2 induction by DNA microarray and alpha-naphthoflavone

DNA microarrays and real time PCR were used to analyze the mechanism of gene induction by CYP1A1 inducers, beta-naphthoflavone, and omeprazole, in the human hepatocellular carcinoma HepG2 cells. Reproducible and significant inductions were observed in a limited number of genes including CYP1A1 and CYP1A2. Genes induced by omeprazole included several protein tyrosine kinase targets. This result confirmed that omeprazole could modulate gene expressions through protein tyrosine kinase-mediated pathway. Induction ratios were considerably different from CYP1A1 and CYP1A2 (>10-fold) to other induced genes (<5-fold). alpha-Naphthoflavone, which is known as an antagonist to 2,3,7,8-tetrachlorodibenzo-p-dioxin, inhibited the inductions of heme oxygenase 1, glutamate-cysteine ligase (modifier unit), and thioredoxin reductase by beta-naphthoflavone but not those of CYP1A1 and CYP1A2. It unexpectedly enhanced the beta-naphthoflavone-mediated CYP1A1 and CYP1A2 induction. These results suggest that the CYP1A1 and CYP1A2 genes, which share their 5(') enhancer regions, are regulated differently from the other genes.     

CYP2D6 and CYP1A1 mutations in the Turkish population

Drugs and carcinogens are substrates of a group of metabolic enzymes including cytochrome p450 enzymes and gluthatione S-transferases. Many of the genes encoding these enzymes exhibit functional polymorphisms that contribute individual cancer susceptibility and drug response. Molecular studies based on these polymorphic enzymes also explain the aetiology of cancer and therapeutic management in clinics. We analysed the cytochrome p4501A1 (CYP1A1) and 2D6 (CYP2D6) variant genotype and allele frequencies by PCR-RFLP in Turkish individuals (n=140). The frequency of the CYP1A1*2A mutant allele was found to be 15.4%, and the CYP2D6*3 and *4 mutant allele (poor metabolizer) frequencies were 2.5% and 13.9%, respectively. This study presents the first results of CYP1A1 and CYP2D6 mutant allele distributions in the Turkish population and these data provide an understanding of epidemiological studies that correlate therapeutic approaches and aetiology of several types of malignancy in Turkish patients.     

Comparison of the 1.85 A structure of CYP154A1 from Streptomyces coelicolor A3(2) with the closely related CYP154C1 and CYPs from antibiotic biosynthetic pathways

The genus Streptomyces produces two-thirds of microbially derived antibiotics. Polyketides form the largest and most diverse group of these natural products. Antibiotic diversity of polyketides is generated during their biosynthesis by several means, including postpolyketide modification performed by oxidoreductases, a broad group of enzymes including cytochrome P450 monooxygenases (CYPs). CYPs catalyze site-specific oxidation of macrolide antibiotic precursors significantly affecting antibiotic activity. Efficient manipulation of Streptomyces CYPs in generating new antibiotics will require identification and/or engineering of monooxygenases with activities toward a diverse array of chemical substrates. To begin to link structure to function of CYPs involved in secondary metabolic pathways of industrially important species, we determined the X-ray structure of Streptomyces coelicolor A3(2) CYP154A1 at 1.85 A and analyzed it in the context of the closely related CYP154C1 and more distant CYPs from polyketide synthase (EryF) and nonribosomal peptide synthetase (OxyB) biosynthetic pathways. In contrast to CYP154C1, CYP154A1 reveals an active site inaccessible from the molecular surface, and an absence of catalytic activities observed for CYP154C1. Systematic variations in the amino acid patterns and length of the surface HI loop correlate with degree of rotation of the F and G helices relative to the active site in CYP154A1-related CYPs, presumably regulating the degree of active site accessibility and its dimensions. Heme in CYP154A1 is in a 180 degrees flipped orientation compared with most other structurally determined CYPs.     

cDNA cloning and characterization of feline CYP1A1 and CYP1A2

Deficiency of drug glucuronidation in the cat is one of the major reasons why this animal is highly sensitive to the side effects of drugs. The characterization of cytochrome P450 isoforms belonging to the CYP1A subfamily, which exhibit important drug oxidation activities such as activation of pro-carcinogens, was investigated. Two cDNAs, designated CYP1A-a and CYP1A-b, corresponding to the CYP1A subfamily were obtained from feline liver. CYP1A-a and CYP1A-b cDNAs comprise coding regions of 1554 bp and 1539 bp, and encode predicted amino acid sequences of 517 and 512 residues, respectively. These amino acid sequences contain a heme-binding cysteine and a conserved threonine. The cDNA identities, as well as the predicted amino acid sequences containing six substrate recognition sites, suggest that CYP1A-a and CYP1A-b correspond to CYP1A1 and CYP1A2, respectively. This was confirmed by the kinetic parameters of the arylhydrocarbon hydroxylase and 7-ethoxyresorufin O-deethylase activities of expressed CYPs in yeast AH22 cells and by the tissue distribution of each mRNA. However, theophylline 3-demethylation is believed to be catalyzed by CYP1A1 in cats, based on the high V(max) and low K(m) seen, in contrast to other animals. Because feline CYP1A2 had a higher K(m) for phenacetin O-deethylase activity with acetaminophen, which cannot be conjugated with glucuronic acid due to UDP-glucuronosyltransferase deficiency, it is supposed that the side effects of phenacetin as a result of toxic intermediates are severe and prolonged in cats.     

A comparison of substrate dynamics in human CYP2E1 and CYP2A6

Considering the dynamic nature of CYPs, methods that reveal information about substrate and enzyme dynamics are necessary to generate predictive models. To compare substrate dynamics in CYP2E1 and CYP2A6, intramolecular isotope effect experiments were conducted, using deuterium labeled substrates: o-xylene, m-xylene, p-xylene, 2,6-dimethylnaphthalene, and 4,4'-dimethylbiphenyl. Competitive intermolecular experiments were also conducted using d(0)- and d(6)-labeled p-xylene. Both CYP2E1 and CYP2A6 displayed full isotope effect expression for o-xylene oxidation and almost complete suppression for dimethylbiphenyl. Interestingly, (k(H)/k(D))(obs) for d(3)-p-xylene oxidation ((k(H)/k(D))(obs)=6.04 and (k(H)/k(D))(obs)=5.53 for CYP2E1 and CYP2A6, respectively) was only slightly higher than (k(H)/k(D))(obs) for d(3)-dimethylnaphthalene ((k(H)/k(D))(obs)=5.50 and (k(H)/k(D))(obs)=4.96, respectively). One explanation is that in some instances (k(H)/k(D))(obs) values are generated by the presence of two substrates-bound simultaneously to the CYP. Speculatively, if this explanation is valid, then intramolecular isotope effect experiments should be useful in the mechanistic investigation of P450 cooperativity.     

褐菖鲉肝CYP 1A作为生物标志物监测厦门海域石油污染状况

以褐菖鲉为实验鱼类,以鱼肝微粒体CYP1A 生物标志物(EROD活性和CYP1A蛋白表达量)为指标,在厦门海域开展了两次野外监测实验,研究EROD活性和CYP1A蛋白表达量的变化,以及它们与海水和沉积物中石油类和重金属含量之间的相关性。结果表明,在现场属于一类海水的石油类浓度(0.0121-0.0242 mg/L)条件下,石油类就能够显著诱导褐菖鲉肝EROD活性和CYP1A蛋白表达量,鱼肝EROD活性和CYP1A蛋白表达量与海水中石油类含量均呈现极显著正相关,CYP1A蛋白表达量比EROD活性较为敏感和稳定。此外,在监测实验中,尚未发现这两种生物标志物受所监测海区的海水和沉积物重金属含量的影响。因此,利用褐菖鲉肝微粒体EROD活性和CYP1A蛋白表达量作为生物标志物监测海洋石油类及其PAHs污染是可行的,在海洋环境石油类污染监测及其生化效应评价中具有重要的应用价值。而且,把这两种生物标志物结合起来加以研究并推广应用将更有意义。     

Polymorphisms of cytochrome P450 1A1, glutathione s-transferases M1 and T1 genes in Ouangolodougou (Northern Ivory Coast)

In this study, the frequencies of CYP1A1, GSTM1, and GSTT1 gene polymorphisms were determined in 133 healthy individuals from Ouangolodougou, a small rural town situated in the north of the Ivory Coast. As appeared in several published studies, ethnic differences in these frequencies have been found to play an important role in the metabolism of a relevant number of human carcinogens. In the studied sample, the frequencies of Ile/Ile (wild type), Ile/Val (heterozygous variant), and Val/Val (homozygous variant) CYP1A1 genotypes were 0.271, 0.692, and 0.037, respectively. Frequencies of GSTM1 and GSTT1 null genotypes were 0.361 and 0.331, respectively. No significant differences were noted between men and women. In contrast to published data for Africans, CYP1A1 *Val Allele frequency (0.383) was significantly high (p < 0.001) in this specific population. For the GSTT1 null genotype, no differences were found between the studied and other African populations, the contrary to what occurred for the GSTM1 null genotype in relation to Gambia and Egypt.     

No contribution of GSTM1 and GSTT1 null genotypes to the risk of neutropenia due to benzene exposure in Southeastern Brazil

Exposure to benzene has been associated with haematological diseases such as neutropenia (NEB) and acute myeloid leukaemia (AML). We tested whether the null genotypes of the GSTM1 and GSTT1 genes, involved in benzene inactivation, altered the risk for NEB in southeastern Brazil. Genomic DNA from 55 NEB patients and 330 controls was analysed by multiplex-polymerase chain reaction. The frequency of the GSTM1, GSTT1 and combined null genotypes was similar in patients and controls (GSTM1, 27.3% vs. 38.8%, p = 0.16; GSTT1, 25.5% vs. 19.7%, p = 0.24; GSTM1/GSTT1, 12.7% vs. 6.7%, p = 0.26; respectively). The distribution of genotype classes in NEB patients was similar to normal controls, suggesting that GSTM1 and GSTT1 null genotypes make no specific contribution to the risk of NEB. As the GSTM1 and GSTT1 null genotypes were previously associated with increased risk for AML in Brazil and elsewhere, we hypothesise that different thresholds of chemical exposure relative to distinct GSTM1 and GSTT1 genotypes may determine whether AML or NEB manifests in benzene exposed individuals from southeastern Brazil. Although indicative, our results still require support by prospective and large scale epidemiological studies, with rigorous assessment of daily chemical exposures and control of the possible contribution of other polymorphic genes involved in benzene metabolism.     

Analysis of the CYP21A1P pseudogene: indication of mutational diversity and CYP21A2-like and duplicated CYP21A2 genes

The CYP21A1P gene downstream of the XA gene, carrying 15 deteriorated mutations, is a nonfunctional pseudogene that shares 98% nucleotide sequence homology with CYP21A2 located on chromosome 6p21.3. However, these mutations in the CYP21A1P gene are not totally involved in each individual. From our analysis of 100 healthy ethnic Chinese (i.e., Taiwanese) (n = 200 chromosomes) using the polymerase chain reaction (PCR) products combined with an amplification-created restriction site (ACRS) method and DNA sequencing, we found that approximately 10% of CYP21A1P alleles (n = 195 chromosomes) presented the CYP21A2 sequence; frequencies of P30, V281, Q318, and R356 in that locus were approximately 24%, 21%, 11%, and 34%, respectively, and approximately 90% of the CYP21A1P alleles had 15 mutated loci. In addition, approximately 2.5% (n = 5 chromosomes) showed four haplotypes of the 3.7-kb TaqI-produced fragment of the CYP21A2-like gene and one duplicated CYP21A2 gene. We conclude that the pseudogene of the CYP21A1P mutation presents diverse variants. Moreover, the existence of the CYP21A2-like gene is more abundant than that of the duplicated CYP21A2 gene downstream of the XA gene and could not be distinguished from the CYP21A2–TNXB gene; thus, it may be misdiagnosed by previously established methods for congenital adrenal hyperplasia caused by a 21-hydroxylase deficiency.     

Structural Analysis of the Streptomyces avermitilis CYP107W1-Oligomycin A Complex and Role of the Tryptophan 178 Residue

CYP107W1 from Streptomyces avermitilis is a cytochrome P450 enzyme involved in the biosynthesis of macrolide oligomycin A. A previous study reported that CYP107W1 regioselectively hydroxylated C12 of oligomycin C to produce oligomycin A, and the crystal structure of ligand free CYP107W1 was determined. Here, we analyzed the structural properties of the CYP107W1-oligomycin A complex and characterized the functional role of the Trp178 residue in CYP107W1. The crystal structure of the CYP107W1 complex with oligomycin A was determined at a resolution of 2.6 Å. Oligomycin A is bound in the substrate access channel on the upper side of the prosthetic heme mainly by hydrophobic interactions. In particular, the Trp178 residue in the active site intercalates into the large macrolide ring, thereby guiding the substrate into the correct binding orientation for a productive P450 reaction. A Trp178 to Gly mutation resulted in the distortion of binding titration spectra with oligomycin A, whereas binding spectra with azoles were not affected. The Gly178 mutant’s catalytic turnover number for the 12-hydroxylation reaction of oligomycin C was highly reduced. These results indicate that Trp178, located in the open pocket of the active site, may be a critical residue for the productive binding conformation of large macrolide substrates.     

CYP1A1, GSTM1 and GSTT1 polymorphisms and lung cancer: a pooled analysis of gene-gene interactions

Gene-environment interactions have been extensively studied in lung cancer. It is likely that several genetic polymorphisms cooperate in increasing the individual risk. Therefore, the study of gene-gene interactions might be important to identify high-susceptibility subgroups. GSEC is an initiative aimed at collecting available data sets on metabolic polymorphisms and the risks of cancer at several sites and performing pooled analyses of the original data. Authors of published papers have provided original data sets. The present paper refers to gene-gene interactions in lung cancer and considers three polymorphisms in three metabolic genes: CYP1A1, GSTM1 and GSTT1. The present analyses compare the gene-gene interactions of the CYP1A1*2A, GSTM1 and GSTT1 polymorphisms from studies on lung cancer conducted in Europe and the USA between 1991 and 2000. Only Caucasians have been included. The data set includes 1466 cases and 1488 controls. The only clear-cut association was found with CYP1A1*2A. This association remained unchanged after stratification by polymorphisms in other genes (with an odds ratio [OR] of approximately 2.5), except when interaction with GSTM1 was considered. When the OR for CYP1A1*2A was stratified according to the GSTM1 genotype, the OR was increased only among the subjects who had the null (homozygous deletion) GSTM1 genotype (OR=2.8, 95% CI=0.9-8.4). The odds ratio for the interactive term (CYP1A1*2A by GSTM1) in logistic regression was 2.7 (95% CI=0.5-15.3). An association between lung cancer and the homozygous CYP1A1*2A genotype is confirmed. An apparent and biologically plausible interaction is suggested between this genotype and GSTM1.     

应用寡核苷酸芯片并行检测CYP1A1和 GSTM1基因多态性

利用寡核苷酸芯片检测方法分析CYP1A1单核苷酸多态性 (SNP)和GSTM1缺失与否 ,实验结果证明了寡核苷酸芯片技术可并行、准确、高效地检测基因的单核苷酸多态性和其他类型的基因多态型 ,可为疾病遗传易感性及单体型的研究提供强有力的研究工具。采用该寡核苷酸芯片 ,检测了 84份正常人的血液DNA样本 ,其中GSTM1基因缺失率达到 4 7 6 % ,接近报道数值。统计分析发现 ,CYP1A1m1 m2的 3种基因型组合TT AG、TT GG和TC GG的发生频率都为 0 ,而根据实验得到的m1和m2各自基因型数据计算 ,它们的发生频率应是11 4 %、2 6 %和 3 1% ,所以推测在所检测的样本中没有T(m1位点 )和G(m2位点 )的连锁组合 ,即m1和m2位点的组合只有 3种单体型 :T A、C A和C G ,其发生频率分别是 6 9 6 %、7 7%和 2 2 6 %。     

Polymorphisms of the CYP1B1 gene have higher risk for prostate cancer

Various carcinogenic factors including estrogen metabolites play a role in malignant transformation. These metabolites are formed in part, as a result of the hydroxylation activity of cytochrome P450 (CYP) 1B1. Variant forms of this enzyme have been shown to enhance its activity, and thus, we hypothesize that single nucleotide polymorphisms of the CYP1B1 gene can be a risk factor for prostate cancer. To test this hypothesis, the genetic distribution of six different CYP1B1 polymorphisms at intron 1 (C-->T), codon 48 (C-->G), codon 119 (G-->T), codon 432 (C-->G), codon 449 (C-->T), and codon 453 (A-->G) was analyzed in 117 prostate cancer samples and 200 healthy normal subjects from a Japanese population. Results of these experiments demonstrate that the genotype at codon 119 is significantly different between prostate cancer patients and controls (P<0.001). The odds ratio of genotype T/T compared to G/G (reference) was calculated as 4.02 with a 95% confidence interval of 1.73-9.38. All other codons, except 453, showed polymorphisms but were not significantly different between cancer patients and controls. No association was found between stage and grade of cancer with any of the polymorphic sites. This is the first report that demonstrates the polymorphism at codon 119 of CYP1B1 to be associated with prostatic carcinogenesis. These results are important in understanding the role of CYP1B1 polymorphisms in the pathogenesis of prostate cancer.     

Mutational analysis of xenobiotic metabolizing genes (CYP1A1 and GSTP1) in sporadic head and neck cancer patients

CYP1A1 is the phase I enzyme that detoxifies the carcinogen or converts it into a more electrophilic form, metabolized by phase II enzymes like GSTP1. These detoxifying genes have been extensively studied in association with head and neck cancer (HNC) in different ethnic groups worldwide. The current study was aimed at screening genetic polymorphisms of genes CYP1A1 and GSTP1 in 388 Pakistani HNC patients and 150 cancer-free healthy controls, using PCR-SSCP. No already known variants of either gene were found, however a novel frameshift mutation due to insertion of T (g.2842_2843insT) was observed in the CYP1A1 gene. A statistically significant number (5.4%) of HNC cases, with the mean age of 51.75 (±15.7) years, presented this frameshift mutation in the conserved domain of CYP1A1. Another novel substitution mutation in was found in the GSTP1 gene, presenting TA instead of AG. The g.2848A > T polymorphism causes a leucine-to-leucine formation, whereas g.2849G > A causes alanine-to-threonine formation at amino acid positions 166 and 167, respectively. These exonic mutations were found in 9.5% of the HNC patients and in none of the controls. In addition, two intronic deletions of C (g.1074delC and g.1466delC) were also found in 11 patients with a mean age of 46.2 (±15.6) years. In conclusion, accumulation of mutations in genes CYP1A1 and GSTP1 appears to be associated with increased risk of developing HNC, suggesting that mutations in these genes may play a role in the etiology of head and neck cancer.     

Null genotypes of GSTM1 and GSTT1 contribute to increased risk of diabetes mellitus: A meta-analysis

Diabetes mellitus (DM) is a common disease which results from various causes including genetic and environmental factors. Glutathione S-Transferase M1 (GSTM1) and Glutathione S-Transferase T1 (GSTT1) genes are polymorphic in human and the null genotypes lead to the absence of enzyme function. Many studies assessed the associations between GSTM1/GSTT1 null genotypes and DM risk but reported conflicting results. In order to get a more precise estimate of the associations of GSTM1/GSTT1 null genotypes with DM risk, we performed this meta-analysis. Published literature from PubMed, Embase and China Biology Medicine (CBM) databases was searched for eligible studies. Pooled odds ratios (OR) and corresponding 95% confidence intervals (95%CI) were calculated using a fixed- or random-effects model. 11 publications (a total of 2577 cases and 4572 controls) were finally included into this meta-analysis. Meta-analyses indicated that null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 were all associated with increased risk of DM (GSTM1: OR _{random-effects} = 1.60, 95%CI 1.10–2.34, P_OR = 0.014; GSTT1: OR _{random-effects} = 1.47, 95%CI 1.12–1.92, P_OR = 0.005; GSTM1–GSTT1: OR _{fixed-effects} = 1.83, 95%CI 1.30–2.59, P_OR = 0.001). Subgroup by ethnicity suggested significant associations between null genotypes of GSTM1 and GSTT1 and DM risk among Asians (GSTM1: OR _{random-effects} = 1.77, 95%CI 1.24–2.53, P_OR = 0.002; GSTT1: OR _{random-effects} = 1.58, 95%CI 1.09–2.27, P_OR = 0.015). This meta-analysis suggests null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are all associated with increased risk of DM, and null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are potential biomarkers of DM.     

Benzo(alpha)pyrene-induced up-regulation of CYP1A2 gene expression: role of adrenoceptor-linked signaling pathways

CYP1A2, a principal catalyst for metabolism of various therapeutic drugs and carcinogens, among others, is in part regulated by the stress response. This study was designed to assess whether catecholamines and in particular adrenergic receptor-dependent pathways, modulate benzo(alpha)pyrene (B(alpha)P)-induced hepatic CYP1A2. To distinguish between the role of central and peripheral catecholamines in the regulation of CYP1A2 induction, the effect of central and peripheral catecholamine depletion using reserpine was compared to that of peripheral catecholamine depletion using guanethidine. The effects of peripheral adrenaline and L-DOPA administration were also assessed. The results suggest that alterations in central catecholamines modulate 7-methoxyresorufin O-demethylase activity (MROD), CYP1A2 mRNA and protein levels in the B(alpha)P-induced state. In particular, central catecholamine depletion, dexmedetomidine-induced inhibition of noradrenaline release and blockade of alpha(1)-adrenoceptors with prazosin, up-regulated CYP1A2 expression. Phenylephrine and dexmedetomidine-induced up-regulation may be mediated, in part, via peripheral alpha(1)- and alpha(2)-adrenoceptors, respectively. On the other hand, the L-DOPA-induced increase in central dopaminergic activity was not followed by any change in the up-regulation of CYP1A2 expression by B(alpha)P. Central noradrenergic systems appeared to counteract up-regulating factors, most likely via alpha(1)- and alpha(2)-adrenoceptors. In contrast, peripheral alpha- and beta-adrenoceptor-related signaling pathways are linked to up-regulating processes. The findings suggest that drugs that bind to adrenoceptors or affect central noradrenergic neurotransmission, as well as factors that challenge the adrenoceptor-linked signaling pathways may deregulate CYP1A2 induction. This, in turn, may result in drug-therapy and drug-toxicity complications.     

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 (IC₅₀ = 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 IC₅₀ 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.     

Sulforaphane and its analogues inhibit CYP1A1 and CYP1A2 activity induced by benzo[a]pyrene

CYP1A1 and CYP1A2 enzymes metabolize polycyclic aromatic hydrocarbons (PAHs) to the reactive oxyderivatives. PAHs can induce the activity of both enzymes, which increases its conversion and enhances risk of carcinogenesis. Thus, the inhibition of CYP enzymes is recognized as a cancer chemoprevention strategy. A well‐known group of chemopreventive agents is isothiocyanates, which occur naturally in Brassica vegetables. In this paper, a naturally occurring sulforaphane and its two synthetic analogues isothiocyanate‐2‐oxohexyl and alyssin were investigated. The aim of the study was to determine whether the differences in the isothiocyanate structure change its ability to inhibit CYP1A1 and CYP1A2 activity induced by benzo[a]pyrene in HepG2 and Mcf7 cells. Also a mechanistic study was performed including isothiocyanates' influence on CYP1A1 and CYP1A2 catalytic activity, enzymatic protein level, and AhR translocation. It was shown that both enzymes were significantly induced by benzo[a]pyrene, and isothiocyanates were capable of decreasing the induced activity. The inhibitory properties depend on the types of isothiocyanate and enzyme. In general, CYP1A2 was altered in the more meaningful way than CYP1A1 by isothiocyanates. Sulforaphane exhibited weak inhibitory properties, whereas both analogues were capable of inhibiting BaP‐induced activity with the similar efficacy. The mechanistic study revealed that analogues decreased the CYP1A2 activity via the protein‐level reduction and CYP1A1 directly. The results indicate that isothiocyanates can be considered as potent chemopreventive substances and the change in the sulforaphane structure increases its chemopreventive potency. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:18–28, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20259