Low concentrations of lead disturb phenotypical markers of the inflammatory and the anti-inflammatory profile of bone marrow-derived macrophages from BALB/c mice.

Lead (Pb) is a ubiquitous toxic metal that decreases resistance to infections, in which the macrophages have an essential role. Pb adverse effects on nitric oxide (NO-) production and variable effects on inflammatory cytokines in activated macrophages have been reported, but no effects have been reported in anti-inflammatory macrophages. We studied Pb (0.03-6 µg/dL equivalent to 0.014-2.89 µM) effects on the function of bone marrow-derived macrophages (BMDM) induced to either inflammatory or anti-inflammatory phenotypes, with LPS + IFNγ or IL-4+IL-13, respectively, and whether these effects are related. Pb did not induce cytotoxicity at any concentration in both macrophage phenotypes. In inflammatory BMDM, Pb (6 µg/dL) inhibited NO- production without affecting inducible nitric oxide synthase (iNOS) levels or basal arginase activity. At 3 and 6 µg/dL, Pb enhanced the major histocompatibility complex class II (MHC II) membrane expression but did not modify CD86 expression, TNFα, or IL-1ß production and secretion. In anti-inflammatory BMDM, Pb did not alter arginase activity, but at 3 and 6 µg/dL, increased TGF-ß1 and mannose receptor expression. Results showed that environmentally relevant concentrations of Pb alter functional outcomes or phenotypic markers of anti-inflammatory for the first time. The Pb effects on the inflammatory macrophages are not dependent on negative feedback resulting from the Pb effect on the anti-inflammatory phenotype. The Pb affected only some molecules or specific pathways related to both phenotypes. These effects could be related to Pb effects on immune defense against intracellular pathogens and allergy susceptibility.

Exploring the biotransformation of N-(2-hydroxyphenyl)-2-propylpentanamide (an aryl valproic acid derivative) by CYP2C11, using in silico predictions and in vitro studies.

OBJECTIVES: N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA), a derivative of valproic acid (VPA), has been proposed as a potential anticancer agent due to its improved antiproliferative effects in some cancer cell lines. Although there is evidence that VPA is metabolized by cytochrome P450 2C11 rat isoform, HO-AAVPA CYP-mediated metabolism has not yet been fully explored. Therefore, in this work, the biotransformation of HO-AAVPA by CYP2C11 was investigated. METHODS: Kinetic parameters and spectral interaction between HO-AAVPA and CYP were evaluated using rat liver microsomes. The participation of CYP2C11 in metabolism of HO-AAVPA was confirmed by cimetidine (CIM) inhibition assay. Docking and molecular dynamics simulations coupled to MMGBSA methods were used in theoretical study. KEY FINDINGS: HO-AAVPA is metabolized by CYP enzymes (KM  = 38.94 µm), yielding a hydroxylated metabolite according to its HPLC retention time (5.4 min) and MS analysis (252.2 m/z). In addition, CIM inhibition in rat liver microsomes (Ki  = 59.23 µm) confirmed that CYP2C11 is mainly involved in HO-AAVPA metabolism. Furthermore, HO-AAVPA interacts with CYP2C11 as a type I ligand. HO-AAVPA is stabilized at the CYP2C11 ligand recognition site through a map of interactions similar to other typical CYP2C11 substrates. CONCLUSION: Therefore, rat liver CYP2C11 isoform is able to metabolize HO-AAVPA.

Paraben concentrations found in human body fluids do not exert steroidogenic effects in human granulosa primary cell cultures.

In cosmetics and food products, parabens are widely used as antimicrobial agents. Reports have suggested that parabens may be linked to infertility, owing to their effects on basal steroidogenesis properties or their capacity to inflict mitochondrial damage. Despite growing concerns about parabens as endocrine disruptors, it is unclear whether they affect any of these actions in humans, particularly at environmentally relevant concentrations. In this work, an in vitro primary culture of human granulosa cells was used to evaluate steroidogenesis, based on the assessment of progesterone production and regulation of critical steroidogenic genes: CYP11A1, HSD3B1, CYP19A1, and HSD17B1. The effects of two commercially relevant parabens, methylparaben (MPB) and butylparaben (BPB), were screened. Cells were exposed to multiple concentrations ranging from relatively low (typical environmental exposure) to relatively high. The effect was assessed by the parabens' ability to modify steroidogenic genes, progesterone or estradiol production, and on mitochondrial health, by evaluating mitochondrial activity as well as mtDNA content. Neither MPB nor BPB showed any effect over progesterone production or the expression of genes controlling steroid production. Only BPB affected the mitochondria, decreasing mtDNA content at supraphysiological concentrations (1000 nM). Prolonged exposure to these compounds produced no effects in neither of these parameters. In conclusion, neither MPB nor BPB significantly affected basal steroidogenesis in granulosa cells. Although evidence supporting paraben toxicity is prevalent, here we put forth evidence that suggests that parabens do not affect basal steroidogenesis in human granulosa cells.

CYP1A1, GSTT1, IL-6 and IL-8 transcription and IL-6 secretion on umbilical endothelial cells from hypertensive pregnant women: Preliminary results.

The impact of pregnancy hypertension in the offspring endothelia remains unknown. We evaluated the transcriptional expression of four genes that participate in the process of endothelial dysfunction using umbilical vein endothelial cell cultures (HUVEC) from healthy pregnant women (PW) and those with hypertensive disorders (HD). The cytochrome P450 1A1 (CYP1A1), gluthathione S-transferase subtype T1 (GSTT1), interleukin 6 (IL-6) and 8 (IL-8) mRNA and IL-6 protein levels were assessed. IL-6 and IL-8 transcripts were significantly reduced in HUVEC obtained from HD women. Our results suggest that a hypertensive environment in utero modifies the transcriptional expression of key inflammatory molecules in the newborn.

Effects of gestational hypertension and pre-eclampsia in mRNA expression of fibrinolysis genes in primary cultured human umbilical vein endothelial cells.

Hypertension disorders (HD) and pre-eclampsia (PRE) are leading causes of maternal deaths worldwide. PRE is associated with vascular endothelial dysfunction and with deregulation of the fibrinolysis pathway genes. Fibrinolysis is the fibrin clot hydrolysis process catalyzed by plasmin, a proteolytic enzyme formed from plasminogen. Plasminogen is cleaved by tissue-type (tPA) and urokinase-type (uPA) activators and inhibited by the plasminogen activator inhibitors type-1 (PAI-1) and type-2 (PAI-2). The whole process maintains blood hemostasis. This study aims to assess PAI-1, PAI-2, tPA and uPA mRNA expression in primary cultured human umbilical vein endothelial cells (HUVEC) isolated and cultured from healthy, HD and PRE women. Results show that PAI-1 and PAI-2 mRNA decreased in HD-HUVEC, whereas PAI-1 and uPA decreased in PRE-HUVEC cultures compared to control ones. Notably, the expression ratio between pro- and anti-fibrinolytic actors remained unchanged among the studied groups. It seems that newborn's hemostasis is maintained balanced probably by a compensatory mechanism that involves changes in the fibrinolysis gene expression profile. The real impact of these changes in mRNA expression is unknown, however, it is suggested that these changes could be associated with an increased predisposition to vascular disease development in the progeny.

Molecular biomarkers to assess health risks due to environmental contaminants exposure.

Biomarkers, or bioindicators, are metric tools that, when compared with reference values, allow specialists to perform risk assessments and provide objective information to decision makers to design effective strategies to solve health or environmental problems by efficiently using the resources assigned. Health risk assessment is a multidisciplinary exercise, and molecular biology is a discipline that greatly contributes to these evaluations because the genome, transcriptome, proteome and metabolome could be affected by xenobiotics causing measurable changes that might be useful biomarkers. Such changes may greatly depend on individual genetic background; therefore, the polymorphic distribution of exposed populations becomes an essential feature for adequate data interpretation. The aim of this paper is to offer an up-to-date review of the role of different molecular biomarkers in health risk assessments.

Molecular biomarkers to assess health risks due to environmental contaminants exposure / Biomarcadores moleculares para evaluar el riesgo para la salud debido a la exposición a contaminantes ambientales

Biomarkers, or bioindicators, are metric tools that, when compared with reference values, allow specialists to perform risk assessments and provide objective information to decision makers to design effective strategies to solve health or environmental problems by efficiently using the resources assigned. Health risk assessment is a multidisciplinary exercise, and molecular biology is a discipline that greatly contributes to these evaluations because the genome, transcriptome, proteome and metabolome could be affected by xenobiotics causing measurable changes that might be useful biomarkers. Such changes may greatly depend on individual genetic background; therefore, the polymorphic distribution of exposed populations becomes an essential feature for adequate data interpretation. The aim of this paper is to offer an up-to-date review of the role of different molecular biomarkers in health risk assessments.

Los biomarcadores, o bioindicadores, son herramientas métricas que, al compararse con los valores de referencia, permiten evaluar los riesgos y generar información objetiva que ayude a las autoridades a planificar estrategias efectivas, solucionar problemas de salud o ambientales y utilizar los recursos asignados de manera eficiente. La evaluación de riesgos en salud es un ejercicio multidisciplinario y la biología molecular contribuye enormemente a estos estudios, dado que el genoma, el transcriptoma, el proteoma y el metaboloma pueden verse afectados por xenobióticos, lo que causa cambios cuya medición resulta útil en la adopción de decisiones. Dichos cambios pueden variar por la carga genética de cada individuo y su distribución polimorfa en las poblaciones expuestas se convierte en un factor esencial para una adecuada interpretación de resultados. Por lo tanto, el objetivo del presente artículo fue hacer una revisión de los diferentes biomarcadores moleculares aplicables a la evaluación de riesgos para la salud provenientes de los contaminantes ambientales.

CYP2E1 epigenetic regulation in chronic, low-level toluene exposure: Relationship with oxidative stress and smoking habit.

BACKGROUND: CYP2E1 is a versatile phase I drug-metabolizing enzyme responsible for the biotransformation of most volatile organic compounds, including toluene. Human toluene exposure increases CYP2E1 mRNA and modifies its activity in leucocytes; however, epigenetic implications of this interaction have not been investigated. GOAL: To determine promoter methylation of CYP2E1 and other genes known to be affected by toluene exposure. METHODS: We obtained venous blood from 24 tannery workers exposed to toluene (mean levels: 10.86+/-7mg/m(3)) and 24 administrative workers (reference group, mean levels 0.21+/-0.02mg/m(3)) all of them from the city of León, Guanajuato, México. After DNA extraction and bisulfite treatment, we performed PCR-pyrosequencing in order to measure methylation levels at promoter region of 13 genes. RESULTS: In exposed group we found significant correlations between toluene airborne levels and CYP2E1 promoter methylation (r=-.36, p<0.05), as well as for IL6 promoter methylation levels (r=.44, p<0.05). Moreover, CYP2E1 promoter methylation levels where higher in toluene-exposed smokers compared to nonsmokers (p=0.009). We also observed significant correlations for CYP2E1 promoter methylation with GSTP1 and SOD1 promoter methylation levels (r=-.37, p<0.05 and r=-.34, p<0.05 respectively). CONCLUSION: These results highlight the importance of considering CYP2E1 epigenetic modifications, as well as its interactions with other genes, as key factors for unraveling the sub cellular mechanisms of toxicity exerted by oxidative stress, which can initiate disease process in chronic, low-level toluene exposure. People co-exposed to toluene and tobacco smoke are in higher risk due to a possible CYP2E1 repression.

Commercial single-walled carbon nanotubes effects in fibrinolysis of human umbilical vein endothelial cells.

Recent studies have demonstrated that carbon nanotubes (CNTs) induce platelet aggregation, endothelial dysfunction and vascular thrombosis. However, there is little information on the effects of CNTs on fibrinolysis. We investigated the role of pristine-commercial single-walled carbon nanotubes (SWCNTs) with <3% Co content in fibrinolysis and their contribution to the induction of pro-thrombotic processes in human vein endothelial cells (HUVEC). SWCNTs alone produced concentration-dependent oxidation, as measured by a dithiothreitol oxidation assay. Internalized SWCNTs were located in HUVEC treated with 25 µg/ml using transmission electron microscopy, whereas treatment with 50 µg/ml compromised cell viability, and oxidative stress increased significantly at 5 µg/ml. The study showed that in HUVEC treated with 25 µg SWCNT/ml, fibrinolysis-related gene expression and protein levels had increased by 3-12 h after treatment (serpine-1: 13-fold; PLAT: 11-fold and PLAU: 2-fold), but only the PAI-1 protein was increased (1.5-fold), whereas tissue and urokinase plasminogen activator proteins (tPA and uPA, respectively) tended to decrease. In summary, pristine SWCNTs treatment resulted in evident HUVEC damage caused by cell fiber contact, internalization, and oxidative stress due to contaminant metals. The generation of endothelial dysfunction, as shown by the altered expression of genes and proteins involved in fibrinolysis, suggest that SWCNTs display pro-thrombotic effects.

A simple validated RP-HPLC bioanalytical method for the quantitative determination of a novel valproic acid arylamide derivative in rat hepatic microsomes.

A simple and specific bioanalytical method based on reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with ultraviolet detection was developed and validated for the determination of a novel valproic acid arylamide, N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) in rat hepatic microsomes (a subcellular fraction containing phase I enzymes, especially cytochrome P450). The chromatographic separation was achieved using a reversed-phase Zorbax SB-C18 column and a mobile phase of acetic acid in water (0.2% v/v) and acetonitrile (40:60 v/v) with a flow rate of 0.5 mL/min. The calibration curve was linear over the range of 882-7060 ng/mL (r(2) = 0.9987), and the lower limit of quantification and the lower limit of determination were found to be 882 and 127.99 ng/mL, respectively. The method was validated with excellent sensitivity, and intra-day accuracy and precision varied from 93.79 to 93.12%, and from 2.12 to 4.36%, respectively. The inter-day accuracy and precision ranged from 93.29 to 97.30% and from 0.68 to 3.60%, respectively. The recovery of HO-AAVPA was measured between 91.36 and 97.98%. The assay was successfully applied to the analysis of kinetic metabolism and pharmacokinetic parameters in vitro by a substrate depletion approach.

Mechanisms of toxicity by carbon nanotubes.

Carbon nanotubes (CNTs) consist of a family of carbon built nanoparticles, whose biological effects depend on their physical characteristics and other constitutive chemicals (impurities and functions attached). CNTs are considered the twenty first century material due to their unique physicochemical characteristics and applicability to industrial product. The use of these materials steadily increases worldwide and toxic outcomes need to be studied for each nanomaterial in depth to prevent adverse effects to humans and the environment. Entrance into the body is physical, and usually few nanoparticles enter the body; however, once there, they are persistent due to their limited metabolisms, so their removal is slow, and chronic cumulative health effects are studied. Oxidative stress is the main mechanism of toxicity but size, agglomeration, chirality as well as impurities and functionalization are some of the structural and chemical characteristic contributing to the CNTs toxicity outcomes. Among the many toxicity pathways, interference with cytoskeleton and fibrous mechanisms, cell signaling, membrane perturbations and the production of cytokines, chemokines and inflammation are some of the effects resulting from exposure to CNTs. The aim of this review is to offer an up-to-date scope of the effects of CNTs on biological systems with attention to mechanisms of toxicity.

Benzo(a)pyrene induces hepatic AKR1A1 mRNA expression in tilapia fish (Oreochromis niloticus).

AKR1A1 or aldehyde reductase is a member of the aldo-keto reductases superfamily that is evolutionarily conserved among species. AKR1A1 is one of the five AKRs (AKR1A1 and 1C1-1C4) implicated in the metabolic benzo(a)pyrene (BaP) activation to reactive BaP 7,8-dione. BaP is a polycyclic aromatic hydrocarbon (PAH) widely distributed in aquatic ecosystems and its metabolic activation is necessary to produce its toxic effects. Although the presence of AKR1A1 in fish has been reported, its tissue distribution in tilapia (Oreochromis niloticus) and AKR1A1 inducibility by BaP are not known yet. Moreover, cytochrome P4501A (CYP1A) mRNA expression in fish has been used as a PAH biomarker of effect. Therefore, BaP effects on AKR1A1 and CYP1A gene expressions in tilapia, a species of commercial interest, were investigated by real-time RT-PCR. A partial AKR1A1 cDNA was identified, sequenced and compared with AKR1A1 reported sequences in the GenBank DNA database. Constitutive AKR1A1 mRNA expression was detected mainly in liver, similarly to that of CYP1A. BaP exposure resulted in statistically significant AKR1A1 and CYP1A mRNA induction in liver (20- and 120-fold, respectively) at 24 h. On the other hand, ethoxyquin (EQ) was used as control inducer for AKR1A1 mRNA. Interestingly, EQ also induced CYP1A mRNA levels in tilapia liver. Our results suggest that teleost AKR1A1, in addition to CYP1A, are inducible by BaP. The mechanism of AKR1A1 induction by BaP and its role in fish susceptibility to BaP toxic effects remains to be elucidated.

CYP2E1 phenotype in Mexican workers occupationally exposed to low levels of toluene.

UNLABELLED: CYP2E1, an inducible enzyme present in different human tissues, metabolizes several potentially toxic substances including many volatile organic compounds (VOCs). One indirect way to monitor exposure to VOCs may be, therefore, the assessment of CYP2E1 activity in vivo using the chlorzoxazone (CHZ) test. GOAL: To compare CYP2E1 activity in two groups of workers: one with a known occupational exposure to VOCs (exposed group) and the other employed in administrative tasks at two universities (control group) from the city of León, Guanajuato, México. MATERIAL AND METHODS: (1) Passive diffusion monitors were used to evaluate individual levels of exposure to toluene, benzene and ethylbenzene in 48 persons (24 tannery workers and 24 administrative controls) during a 8h work shift; (2) after 12h fasting 500mg CHZ, a selective probe for assessing CYP2E1 activity, was orally administered and, after 2h, a venous blood sample was collected for HPLC plasmatic quantitative determination of CHZ and its mean metabolite 6-hydroxychlorzoxazone. RESULTS: Toluene mean exposure levels were higher in the exposed group (2.86±2ppm vs. 0.05±0.005ppm; p<0.001). Also, in this group CYP2E1 activity was lower (p<0.05) and it decreased as the accumulated months of labor exposure increased (negative correlation, p<0.05). These results are in line with previous findings obtained from shoemakers exposed to various solvents but, interestingly, they are partly in contrast with those of another study in printers. CONCLUSION: In spite of the relatively low levels of toluene exposure found for tannery workers, an effect on CYP2E1 activity was evident. Although the mechanism of this interaction is still unknown, the decrease in CYP2E1 activity per se might represent a health risk, considering that these workers may be less protected against other CYP2E1 substrates present in the labor setting or derived from an intentional exposure.

The relationship among IL-13, GSTP1, and CYP1A1 polymorphisms and environmental tobacco smoke in a population of children with asthma in Northern Mexico.

Exposure to environmental tobacco smoke (ETS) during early childhood increases the risk of developing asthma. The intention of this study was to genotype a population of children from Coahuila state in Northern Mexico and to determine whether polymorphisms of the CYP1A1, GSTP1, and IL13 genes are associated with exposure to ETS and subsequently a higher risk for asthma. IL13 plays an important role in the development of allergic response, particularly those related with airway inflammation. CYP1A1 and GSTP1 are xenobiotic-metabolizing enzymes induced by repeated exposure to toxicants. Polymorphisms of these genes have been related with ETS exposure and increased risk for asthma. To assess the effect of IL13 (-1112 C>T and Arg110Gln), GSTP1 (Ile105Val), and CYP1A1 (Ile462Val) on asthma risk and ETS exposure, we recruited 201 unrelated children and classified them into four groups: (1) control without ETS exposure; (2) control with ETS exposure; (3) with asthma and with ETS exposure and (4) with asthma and without ETS exposure. No association among ETS exposure, asthma, and the studied polymorphisms was denoted by multivariate analysis of this population.

Occupational toxicology in Mexico: current status and the potential use of molecular studies to evaluate chemical exposure.

Occupational toxicology is of considerable concern for several world organizations including the International Labour Organization, the World Health Organization and the International Commission for Occupational Health and, in Latin America, the Pan American Health Organization. The countries of this Region, including Mexico, own manufacturing, chemical, and petrochemical industries that employ thousands workers who are continually exposed to hazardous chemicals such as solvents, particles and exhaust fumes, many of which are very complex mixtures. Traditionally, physicians have used biochemical analyses to assess the damage caused by chronic chemical exposure. Presently, recent advances in molecular biology may offer tools to perform more thorough and precise evaluations on worker health damage, risk and current health status. In this review, we present a perspective of occupational toxicology in Mexico, as an example for Latin America and developing countries. Moreover, we summarize current reports about occupational disease associated with chemical exposure, and we present an array of molecular studies proposed for the analysis and diagnosis of workers related with industry and the relevance of including molecular biology testing to complement traditional occupational medical assays in order to improve occupational health. We conclude that developing countries, e.g., Mexico, should improve work environment standards by using new technical approaches that will result in more reliable and precise data to design better health policy strategies.

Dose-dependent urinary phenotype of inorganic arsenic methylation in mice with a focus on trivalent methylated metabolites.

Inorganic arsenic (iAs) exposure has been associated with the increased risk of various forms of cancer and of non-cancerous diseases. Metabolic conversions of iAs that yield highly toxic and genotoxic methylarsonite (MAsIII) and dimethylarsinite (DMAsIII) may play a significant role in determining the extent and character of toxic and cancer-promoting effects of iAs exposure. However, in vivo research involving the production of MAsIII and DMAsIII remains an area of ongoing investigation and debate. The results of metabolic and toxicity studies using mice have been entirely applicable to other species including humans. The goal of this study was to investigate the phenotype for the trivalent and pentavalent arsenic metabolites in relation to arsenite dose via immediate analysis of fresh urine samples, while preventing the oxidation of unstable methylated AsIII-containing metabolites. Female mice (C57BL/6) received sodium arsenite by gavage at doses of 0, 3, 6 or 10 mg As/kg/day for 9 days, after which trivalent methylated arsenicals were detected in 100% of urine samples; these arsenicals were not detected in the urine of control mice. The amount of DMAsIII detected in urine depended on the dose of arsenite administered and was determined to be 50.2%, 31.4% and 16.5% of the total urinary arsenic in mice exposed to 3, 6, or 10 mg/kg/day, respectively. This relationship is consistent with the hypothesis of inhibition or saturation of iAs methylation. Understanding the in vivo production of MAsIII and DMAsIII in mice exposed to iAs could aid in developing a biologically based dose-response model for iAs.

The role of molecular biology in the biomonitoring of human exposure to chemicals.

Exposure to different substances in an occupational environment is of utmost concern to global agencies such as the World Health Organization and the International Labour Organization. Interest in improving work health conditions, particularly of those employees exposed to noxious chemicals, has increased considerably and has stimulated the search for new, more specific and selective tests. Recently, the field of molecular biology has been indicated as an alternative technique for monitoring personnel while evaluating work-related pathologies. Originally, occupational exposure to environmental toxicants was assessed using biochemical techniques to determine the presence of higher concentrations of toxic compounds in blood, urine, or other fluids or tissues; results were used to evaluate potential health risk. However, this approach only estimates the presence of a noxious chemical and its effects, but does not prevent or diminish the risk. Molecular biology methods have become very useful in occupational medicine to provide more accurate and opportune diagnostics. In this review, we discuss the role of the following common techniques: (1) Use of cell cultures; (2) evaluation of gene expression; (3) the "omic" sciences (genomics, transcriptomics, proteomics and metabolomics) and (4) bioinformatics. We suggest that molecular biology has many applications in occupational health where the data can be applied to general environmental conditions.

Sodium arsenite alters cell cycle and MTHFR, MT1/2, and c-Myc protein levels in MCF-7 cells.

There is limited available information on the effects of arsenic on enzymes participating in the folate cycle. Therefore, our aim was to evaluate the effects of sodium arsenite on the protein levels of methylenetetrahydrofolate reductase (MTHFR) and dihydrofolate reductase (DHFR) and its further relationship with the expression MT1/2 and c-myc in MCF-7 cells. Arsenite treatment (0-10 microM) for 4 h decreased MTHFR levels in a concentration-dependent fashion without significant effects on DHFR. The effects on MTHFR were observed at arsenite concentrations not significantly affecting cell viability. We also observed an increase in S-phase recruitment at all concentrations probed. Lower concentrations (<5 microM) induced cell proliferation, showing a high proportion of BrdU-stained cells, indicating a higher DNA synthesis rate. However, higher concentrations (> or =5 microM) or longer treatment periods induced apoptosis. Arsenite also induced dose-dependent increases in MT1/2 and c-Myc protein levels. The levels of MTHFR were inversely correlated to MT1/2 and c-Myc overexpression and increased S-phase recruitment. Our findings indicate that breast epithelial cells are responsive to arsenite and suggest that exposure may pose a risk for breast cancer. The reductions in MTHFR protein levels contribute to understand the mechanisms underlying the induction of genes influencing growth regulation, such as c-myc and MT1/2. However, further research is needed to ascertain if the effects here reported following short-time and high-dose exposure are relevant for human populations chronically exposed to low arsenic concentrations.

Changes in gene expression induced by polycyclic aromatic hydrocarbons in the human cell lines HepG2 and A549.

Polycyclic aromatic hydrocarbons (PAH) are the main components of emissions generated by coke oven factories and many of these chemicals are carcinogenic. The goal of this study was to examine changes in gene expression in two human cell lines, HepG2 and A549, induced by exposure to a soil extract containing PAH using microarry technology. Soil samples were obtained from the vicinity of a coke oven factory in northeastern Mexico. For comparison, the gene expression pattern induced by Benz[a]pyrene (BaP) was also analyzed. The number of altered genes by both treatments was 2-fold higher in hepatic than in pulmonary cells. Differentially-modulated genes in the two cell lines were identified and grouped by biological function using genomic databases. A group of nine genes up- and down-regulated by either the PAH extract or BaP were selected for validation by real-time PCR. The cellular functions of these PAH-responsive genes included: xenobiotic metabolism (CYP1A1 and CYP1B1), DNA repair (ERCC5), oxidative stress response and cell proliferation (FTH1 and PRDX1), protein degradation (PSMD7), ion transport (FXYD3), steroid biosynthesis (FDFT1), and signaling pathways (PTGER3). The real-time PCR analysis confirmed most of the microarray data with significant correlation. Additional studies are required to determine the mechanisms involved in the PAH-mediated modulation of these genes and to associate these changes with human health.

A comparative study of CYP3A4 polymorphisms in Mexican Amerindian and Mestizo populations.

Cytochrome P-450 3A4 (CYP3A4) contributes to the metabolism of approximately half the drugs in clinical use today. The aim of the present study was to determine the frequency of the CYP3A4*1B, *2, *4, *5, and *18 alleles amongst both Tepehuan Amerindians, a native group that has inhabited northern Mexico for thousands of years, and Mestizo Mexicans, and to compare the data with those of other populations. Genotyping experiments revealed that 8.8 and 8.0% of the Mestizo and Tepehuano subjects, respectively, carried the CYP3A4*1B allele. Only one Mestizo subject was heterozygous for the CYP3A4*2 variant, while CYP3A4*4, *5 and *18 allelic variants were not detected in either group. On the other hand, the frequencies of the CYP3A4*1B variant in Mestizos and Tepehuanos were similar to those reported for Caucasians, but different from those observed for African and Asian populations.