Category Archives: CYP

C 040: USE OF GENETICALLY MODIFIED MOUSE MODELS TO STUDY MECHANISMS OF CHEMICALLY-INDUCED LIVER CANCER RISK

Cancer, CYP, Preclinical Research
J Pharm Pharmacogn Res 2(Suppl. 1): S110, 2014

Special supplement with the abstract book of LATINFARMA 2013

Conference

C 040: USE OF GENETICALLY MODIFIED MOUSE MODELS TO STUDY MECHANISMS OF CHEMICALLY-INDUCED LIVER CANCER RISK

Grant DM.

Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada.
Abstract

Liver cancer is the 5th most common malignancy and the 3rd most common cause of cancer-related death, reflecting a very poor 5-year survival rate of less than 20%. Major liver cancer risk factors include hepatitis B/C infection, liver cirrhosis and obesity, which produce a tumor growth promoting, pro-inflammatory pathological state. However, liver cancer risk has also been linked to exposure to certain genotoxic environmental chemicals, of which the most widely used liver-selective carcinogens in experimental rodent studies are the aromatic amine 4-aminobiphenyl (ABP) and the nitrosamine diethylnitrosamine (DEN). Studies in our laboratory are aimed at utilizing genetically modified mice to investigate the contributions of carcinogen bioactivation, DNA damage, oxidative stress, cellular damage and inflammatory responses to the carcinogenicity of ABP and DEN. We compared the tumorigenicity of ABP in postnatally exposed male and female wild-type and arylamine N-acetyltransferase (NAT)deficient mice, and we observed that male NAT-deficient mice were significantly protected against eventual tumor growth and female mice were tumor-resistant regardless of strain. However, these differences in tumor incidence did not correlate with differences in measures of acute ABP-induced DNA damage or mutations, suggesting that the sex and strain differences in tumor incidence are driven by events that are independent of the genotoxicity of ABP. ABP and DEN produced no acute hepatotoxicity at tumor-inducing doses in either sex or strain, and only DEN produced a modest acute elevation in the proinflammatory cytokine IL-6. We are currently conducting studies to compare the time course of chronic hepatotoxic, oxidative stress inducing, pro-inflammatory and proliferative effects of postnatal ABP and DEN exposure. Using CYP1A2-deficient mice, we have also recently discovered that at the tumorigenic doses of ABP that are commonly used in rodent studies, the cytochrome P450 isoform CYP2E1 is likely to be quantitatively more important than CYP1A2 in the bioactivation of ABP to its N-hydroxylated metabolite. Overall, we hope that our studies will shed light on the mechanisms that influence risk for liver tumor growth following chemical exposure, and lead to the identification of treatment or prevention measures for this disease in human at-risk populations.

C 031: INHIBITION OF CYTOCHROME P450 BY NATURAL PRODUCTS AS AN ANTIMUTAGENESIS MECHANISM

CYP, Natural Products
J Pharm Pharmacogn Res 2(Suppl. 1): S92, 2014

Special supplement with the abstract book of LATINFARMA 2013

Conference

C 031: INHIBITION OF CYTOCHROME P450 BY NATURAL PRODUCTS AS AN ANTIMUTAGENESIS MECHANISM

Espinosa-Aguirre JJ.

Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), D.F., Mexico.
Abstract

CYP enzymes are involved in the metabolism of xenobiotics as well as some endogenous compounds. Its activities lead to the production of mutagenic and carcinogenic entities that can react with important macromolecules like proteins and nucleic acids. In theory, Inhibition of CYP catalysis could lead to inhibition of the mutagenic and carcinogenic processes considering the inhibitory compounds as beneficial chemoprotective agents. Using in vitro biochemical methods we have tested the CYP inhibitory capacity of several plant derived compounds like bergamotin, dehydrobergamotin and naringin from grapefruit, quercetin and chiro-inositol from Heteroteca inuloides, mangiferin from Mangifera indica and thalassiolin b from Thalassia testidinum. Results obtained showed the CYP inhibitory activity of these compounds, being bergamotin and thalassiolin b of the molecules with high inhibitory potential. Results from the Ames Assay in which we tested the antimutagenic properties of these compounds against known mutagens, shows that the inhibition of CYP activity can be traduced in an antimutagenic effect in this Assay. These effects were also confirmed in rat hepatic cells in culture, where effects on activity/expression of CYP1A1 were tested. The possible use of these antimutagenic substances as chemoprotective agents is discussed in the light of the existence of endogenous CYP substrates.

C 026: PHARMACOGENETICS: CLINICAL IMPLICATIONS FOR EATING DISORDERS AND SUICIDE

CYP, Pharmacogenomics
J Pharm Pharmacogn Res 2(Suppl. 1): S70, 2014

Special supplement with the abstract book of LATINFARMA 2013

Conference

C 026: PHARMACOGENETICS: CLINICAL IMPLICATIONS FOR EATING DISORDERS AND SUICIDE

Llerena A, Naranjo ME; Peñas-Lledo E.

Clinical Research Centre, Extremadura University Hospital and Medical School, Badajoz, Spain. Ibero Latino American Network of Pharmacogenetics (www.ribef.com).
Abstract

Pharmacogenomics Clinical implications. A higher frequency of CYP2D6 UMs has been found among individuals who committed suicide (Zackrisson et al., 2010). One explanation for this relationship could be treatment failure with antidepressant drugs metabolized by CYP2D6 (Llerena et al., 2004) widely used to prevent suicide or to treat mood disorders. A complementary explanation could be via the implication of the polymorphic CYP2D6 in the endogenous metabolism. CYP2D6 has been associated with behavioral and clinical risk factors such as personality and vulnerability to psychopathology (Llerena et al., 1993; 2007; Gonzalez et al., 2008; Peñas-Lledó et al., 2009, 2010). Consistently, we found a relationship between UMs and severity of suicide and lifetime history of suicidal behavior among Eating Disordered patients (Peñas-LLedó et al., 2010, 2011, 2012a). Moreover it seems also been related to antidepressant discontinuation as recently shown (Peñas-LLedó et al., 2012b). Therefore Pharmacogenomics might be useful to prevent relevant side effects such is suicide.

C 025: GENETIC VARIATION IN SMOKING AND LUNG CANCER

Cancer, CYP
J Pharm Pharmacogn Res 2(Suppl. 1): S70, 2014

Special supplement with the abstract book of LATINFARMA 2013

Conference

C 025: GENETIC VARIATION IN SMOKING AND LUNG CANCER

Tyndale R.

Centre for Addiction and Mental Health, Departments of Psychiatry, Pharmacology and Toxicology, University of Toronto, Toronto, Canada.
Abstract

Nicotine is the main active component in cigarette which mediates tobacco dependence. About 80% of nicotine is metabolically inactivated to cotinine; the hepatic CYP2A6 enzyme is responsible for over 90% of this conversion. Both in vivo and in vitro studies demonstrate considerable interindividual variation in CYP2A6 activity that is attributed to variations in the CYP2A6 gene. Individuals with at least 1 copy of the genetically inactive or reduced activity CYP2A6 variant (allele) have decreased nicotine metabolism.

We have found that slow nicotine inactivators are ≈2 times less likely to be dependent smokers (OR 0.52 95% CI 0.29-0.95). Slow metabolizers that do become smokers consume 7-10 cigarettes less per day than normal metabolizers, and also inhale less deeply. There are large differences among ethnic populations in the frequency of slow metabolizers which may contribute to the ethnic differences observed in rates of smoking and tobacco-related diseases. In general the frequencies of variant alleles with large impacts on function are low in Caucasians, while some of the alleles are prevalent (up to 20%) for example in Asian and African populations. Variation in CYP2A6 genotype and/or the CYP2A6 metabolite ratio biomarker is associated with differences in the ability to quit smoking both in the absence of pharmacotherapy, and with nicotine replacement therapies. We found the odds of quitting with nicotine patch were reduced by 30% with each increasing quartile of the ratio; faster metabolizers were less successful in quitting than slow metabolizers.

CYP2A6 is also capable of activating tobacco-procarcinogens such as NNK. Thus individuals with slower CYP2A6 smoke less and activate less tobacco-smoke procarcinogens resulting in lowered risk for tobacco- and dietary-related cancers such as lung cancers, while those with high levels of CYP2A6 are at greater risk. We have also shown that having a variant in the α3-α5-β4 nicotinic receptor cluster, a target for both nicotine and nitrosamines, also alters smoking and lung cancer risk. When examining variation in CYP2A6 and the nicotinic receptor variant together we observe an increase in both smoking and lung cancer risk for those who are faster CYP2A6 metabolizers and have the at risk nicotinic receptor variant.

C 015: EFFECT OF DNA DEMETHYLATION ON CYP1A1 GENE EXPRESSION IN RAT CELLS

CYP
J Pharm Pharmacogn Res 2(Suppl. 1): S31, 2014

Special supplement with the abstract book of LATINFARMA 2013

Conference

C 015: EFFECT OF DNA DEMETHYLATION ON CYP1A1 GENE EXPRESSION IN RAT CELLS

Olguín-Reyes S, Camacho-Carranza R, Espinosa-Aguirre JJ.

Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, UNAM, México D.F.
Abstract

Gene regulation involves transcription factors, responsive elements, enhancers, insulators, DNA methylation, histone methylation, acetylation, and deacetylation, among others. In a whole organism, such components may depend on external factors such as environmental pollution. Polycyclic aromatic hydrocarbons (PAH) found in environmental pollution, are susceptible of biotransformation by CYP1A1, a phase I enzyme. In turn, CYP1A1 gene expression is induced by PAHs through the aromatic hydrocarbon receptor (AhR).

However, PAHs exposure affects not only CYP1A1 expression through AhR but also may affect other proteins involved in epigenetic regulation. In order to test this hypothesis, rat hepatocytes clone-9 cell line (C9) was exposed to benzo[a]pyrene (BaP) and to the DNMTs inhibitor 5’-Aza-2’-deoxycitidine (5AzadC), with their respective controls. CYP1A1 expression was determined by qPCR and western blot analysis. The concentration of DNMT3a was also determined. CYP1A1 gene expression was increased after BaP treatment and exacerbated when 5AzadC was co-administrated. DNMT3a protein level decrease in C9 culture after 5AzadC as expected. BaP treatment also produces decrease in DNMT3a protein, although not at the same level seen after 5AzadC treatment. We can conclude that the mechanism behind the positive modulation of CYP1A1 by BaP involves not only AhR but other proteins of the epigenetic machinery like DNMT.