Characterization of calcium oscillations in normal and benzo[a]pyrene-treated clone 9 cells.

Intracellular Ca2+ oscillations induced by oxytocin and vasopressin were analyzed in a rat liver cell line (Clone 9) in order to identify mechanisms by which benzo[a]pyrene (BaP) alters Ca2+ signaling patterns in these cells. Clone 9 cells exhibit an initial Ca2+ spike, followed by Ca2+ oscillations upon oxytocin or vasopressin treatment. The range of frequencies (maximum 110 mHz) was dependent on agonist concentration with a constant amplitude less than or equal to the amount of Ca2+ generated from the inositol trisphosphate (InsP(3))-sensitive pool. This study examined contributions of extracellular and intracellular pools to the frequency of Ca2+ oscillations and the role of membrane channels, second messengers, and different pharmacological reagents on the regulation of oscillation frequency in both control and BaP-treated cells. Results indicated that the Ca2+ oscillations are mainly due to inositol 1,4,5-triphosphate (InsP(3))-sensitive stores and that extracellular Ca2+ contributes to refilling of this intracellular Ca2+ pool. The frequency of Ca2+ oscillations is also sharply affected by protein kinase C activated by phospholipase C. In BaP-treated Clone 9 cells, basal Ca2+ levels were elevated and the frequency of Ca2+ oscillations was suppressed in a dose-dependent fashion. Suppression of Ca2+ oscillations is due, at least in part, to an effect of BaP on enhanced opening of K+ channels. This was confirmed by showing that inhibition of the K+ channel opening by tetraethylammonium chloride can reverse the effect of BaP on oxytocin-induced Ca2+ oscillations, and potentially decrease the toxicity of BaP.     

Gene expression changes associated with altered growth and differentiation in benzo[a]pyrene or arsenic exposed normal human epidermal keratinocytes

Both arsenic and benzo[a]pyrene (BaP) inhibit terminal differentiation and alter growth potential in normal human epidermal keratinocytes (NHEK) in vitro. To identify molecular alterations that may be involved in these cellular processes, microarray analysis was carried out on NHEK treated with BaP or arsenic. The gene expression microarray results measuring mRNA levels were as follows: (1) in total, the expression of 85 genes was induced and 17 genes was suppressed by 2.0 microm BaP. (2) Arsenic at an equitoxic dose (5.0 microm) induced the expression of 106 and suppressed 15 genes. Quantitative real-time RT-PCR was used subsequently to confirm microarray findings on selected genes involved in keratinocyte growth and differentiation pathways. These studies confirmed increased mRNA levels in NHEK by BaP of alpha-integrin binding protein 63 (AIBP63) (2.48-fold), retinoic acid- and interferon-inducible protein (IFIT5) (2.74-fold), interleukin-1 alpha (IL1A) (2.64-fold), interleukin-1 beta (IL1B) (2.84-fold) and Ras guanyl releasing protein 1 (RASGRP1) (3.14-fold). Real-time RT-PCR confirmed that arsenic increased mRNA levels of the following genes: retinoblastoma 1 (RB1) (5.4-fold), retinoblastoma-binding protein 1 (ARID4A) (6.8-fold), transforming growth factor beta-stimulated protein (TSC22D1) (6.84-fold), MAX binding protein (MNT) (2.44-fold), and RAD50 (4.24-fold). Collectively, these results indicate that these chemicals target different genes and molecular pathways involved in the regulatory processes controlling NHEK proliferation and differentiation. Mechanistic studies with a subset of genes may allow the correlation of alterations in these molecular markers with chemical-specific blocks to differentiation in NHEK.     

Selective thromboxane synthetase inhibitors. 3. 1H-imidazol-1-yl-substituted benzo[b]furan-, benzo[b]thiophene-, and indole-2- and -3-carboxylic acids

The preparation of a series of 1H-imidazol-1-yl-substituted benzo[b]furan-, benzo[b]thiophene-, and indolecarboxylic acids is described. Most of the compounds were potent inhibitors of TxA2 synthetase in vitro, and the distance between the imidazole and carboxylic acid groups was found to be important for optimal potency. The most potent compound in vivo was 6-(1H-imidazol-1-ylmethyl)-3-methylbenzo[b]thiophene-2-carboxylic acid (71), which, in conscious dogs, showed a similar profile of activity to that of dazoxiben (1).     

CYP1C1 messenger RNA expression is inducible by benzo[a]pyrene in Fundulus heteroclitus embryos and adults.

CYP1C is the newest member of the CYP1 family of P450s; however, its physiological significance, inducers, and metabolic functions are unknown. Two full-length alleles of Fundulus heteroclitus CYP1C1 complementary DNA were cloned. The 529 amino acid protein shared the highest amino acid identity with Stenotomus chrysops CYP1C1 (81%). To investigate whether the carcinogen benzo[a]pyrene (BaP) was a CYP1C1 inducer, we used real-time PCR to quantitatively measure tissue- and sex-specific expression of both CYP1C1 and CYP1A messenger RNAs (mRNAs) in BaP-exposed adult fish. CYP1C1 mRNA expression was constitutively higher than CYP1A in brain, spleen, eye, and gonad, while CYP1A was higher in gastrointestinal tract (GI), heart, gill, and liver. Kidney had equal but high expression of both CYP1s. There were sex differences in constitutive CYP1 expression in the GI, liver, gill, and eye. BaP exposure caused induction of CYP1C1 expression in female and male heart (31- and 17-fold), gill (seven- and four-fold), and liver (six- and five-fold), respectively. Embryo CYP1 expression was constitutively highest at 2 weeks posthatch, and whole embryos expressed 3- to 15-fold more CYP1C1 mRNA compared to CYP1A. BaP, 10 microg/l for 10 days, caused induction of both genes at 120 and 240 h postfertilization. Our results suggest that teleost CYP1C, in addition to CYP1A, is inducible by BaP, has a broad tissue distribution, and should be further investigated for its role in carcinogen bioactivation.     

Ras transgene expression in TG-AC mice treated with benzo[a]pyrene

Transgene expression and skin tumorigenicity were investigated in transgenic TG-AC mice carrying the v-Ha-ras after treatment with benzo[a]pyrene (BP). Animals treated with 40 microg BP (x2/week/mouse) showed 100% tumor response after 25 weeks, as did 40% of the mice treated with 20 microg BP but 10 microg BP did not produce a tumor response. In the case of animals treated with 40 microg BP for 25 weeks, most of the tumors were proven to be carcinomas (80%, 4 out of 5 mice), and all tumors were shown to be positive in terms of transgene expression detected by in situ hybridization. These data suggest that BP was tumorigenic in a dose-dependent manner in TG-AC mice and that TG-AC mice were dependent on transgene expression during BP carcinogenesis.     

Formation of hemoglobin-benzo[a]pyrene adducts in human erythrocytes incubated with benzo[a]pyrene and hamster embryo cells

Evidence is accumulating that the levels of covalent carcinogen-macromolecule adducts, including adducts with hemoglobin, reflect biologically effective levels of carcinogen exposure. The purposes of the present study were (a) to establish a cellular system for obtaining adducts between intracellular human hemoglobin and metabolites of polycyclic aromatic hydrocarbons (PAH), and (b) to evaluate techniques for chromatographic characterization of the adducts. We showed that hemoglobin-benzo[a]pyrene adducts were formed when human erythrocytes were treated with [3H]benzo[a]pyrene (BP) in the presence of hamster embryo fibroblasts, which are known to be effective for BP metabolism. After lysis of the erythrocytes, noncovalently bound BP and its metabolites were effectively removed from hemoglobin under mild conditions by using hydrophobic interaction and size-exclusion liquid chromatography. Three to five distinct adducts were resolved by reversed-phase and ion-exchange liquid chromatography. As determined by a two-step, reversed-phase liquid chromatographic procedure, trypsin treatment of globin from the cellular system yielded at least three of the four 7,8,9,10-tetrahydro-7,8,9,10-tetrahydroxy BP tetrols known to arise from mammalian metabolism of BP. This observation is consistent with both (a) the recently described formation of labile carboxyl esters via reaction of BP-7,8-dihydrodiol-9,10-epoxide (BPDE) with hemoglobin and (b) the known formation of both anti- and syn-BPDE in hamster embryo fibroblasts. In addition, high-performance liquid chromatographic analysis demonstrated the presence of other products presumed to be BP-peptide adducts because of their susceptibility to thermolysin treatment.     

Phytochemicals induce breast cancer resistance protein in Caco-2 cells and enhance the transport of benzo[a]pyrene-3-sulfate.

We have previously reported that breast cancer resistance protein (BCRP) is involved in the transport of phase II metabolites of the food carcinogen benzo[a]pyrene (BP) in the human intestinal cell line Caco-2. Furthermore, the expression of BCRP seemed most likely to be aryl hydrocarbon receptor (AhR) dependent. Since numerous plant-derived anticarcinogens with AhR-agonistic activity have been identified to date, in the present study we investigated the effects of naturally occurring dietary compounds and tert-butyl hydroquinone (TBHQ) for their effects on BCRP expression. In Caco-2 cells, the most pronounced induction of BCRP expression could be observed after treatment with TBHQ (100 microM), dibenzoylmethane (DBM, 50 microM), and quercetin (25 microM), while green tea component (-)-epicatechin (50 microM) decreased BCRP expression. On mRNA level, quercetin, chrysin, flavone, and indole-3-carbinol showed a strong inducing effect, while genistein had no effect on BCRP mRNA expression. Curcumin and resveratrol showed a strong effect on BCRP induction in MCF-7 wild-type cells but no response in AhR-deficient MCF-7AHR(200) cells, supporting our hypothesis that BCRP is regulated via AhR-dependent signaling pathways. Inhibition of proteasome-mediated degradation of ligand-activated AhR caused a "superinduction" of BCRP mRNA. Antioxidant responsive element activators sulforaphane and diethylmaleate (DEM) had no inducing effect on BCRP mRNA expression. Caco-2 cells pretreated with quercetin or DBM showed an enhancement of apically transported benzo[a]pyrene-3-sulfate, indicating that induced BCRP was functionally active. In conclusion, apart from the modulation of detoxifying enzymes in the intestine, induction of BCRP by dietary constituents may contribute to the detoxification of food-derived procarcinogens such as BP.     

Identification and quantitation of 7-(benzo[a]pyren-6-yl)guanine in the urine and feces of rats treated with benzo[a]pyrene

The major identified benzo[a]pyrene (BP)-DNA adduct formed by cytochrome P-450 contains BP bound at the C-6 position to the N-7 position of guanine (BP-N7Gua). This adduct is rapidly depurinated from DNA. When rats were treated with [14C]BP, about 0.02% of the administered dose of BP was excreted as BP-N7Gua in feces and urine within 5 days. Chloroform extracts of the urine and feces were analyzed by high-pressure liquid chromatography. The structure of the adduct was established by cochromatography with electrochemically prepared BP-N7Gua and by fluorescence line narrowing spectrometry. This study represents the first demonstration that BP-N7Gua is formed in vivo in animals treated with BP.     

New 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants

In this paper a series of new 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives is presented as a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. The 5-HT1A receptor and 5-HT transporter binding affinities of hydroxylic compounds 4 a-e have been determined. The new compounds present nanomolar affinity for both activities, and 1-(benzo[b]thiophen-3-yl)-3-[4-(3-methoxyphenyl)piperazin-1-yl]propan-1-ol (4d) shows values (nM) of Ki = 86 for 5-HT1A receptors and Ki = 76 for the serotonin transporter, respectively.     

Degradation of [3H]beta-endorphin in rat plasma is increased with chronic stress

With a number of acute stressors beta-endorphin is released into plasma. It is unclear if beta-endorphin is converted into any other biologically active products, nor is it clear if the rate or pathways of degradation are changed during chronic stress. To explore these issues, we incubated [3H]beta-endorphin h labeled in positions 1 and 27 with plasma from normal and chronically footshocked rats and measured the rate of conversion of the label from beta-endorphin size material to smaller size material. Initial separations were done using a G-50 molecular sieving column, with subsequent characterization and identification on HPLC. By G-50 sieving, there is a time dependent formation of only one radioactive peak. HPLC identification demonstrates gamma-endorphin and another unidentified peak. This enzymatic activity is increased in the plasma of chronically stressed rats.     

Altered benzo[a]pyrene metabolism in C3H/10T1/2 cells transformed by aflatoxin B1 or 3-methylcholanthrene

C3H/10T1/2 clone 8 (10T1/2) cells possess Phase I and Phase II xenobiotic metabolizing enzymes associated with the metabolism of polycyclic aromatic hydrocarbons to activated or detoxified species. We compared the metabolism of benzo[a]pyrene (BaP) by these cells to an aflatoxin B1 (AFB1)-transformed line (7SA) and a 3-methylcholanthrene (3-MC)-transformed line (MCA) isolated from carcinogen-treated 10T1/2 cells. Relative to 10T1/2 cells, basal levels of cytochrome P450-mediated aryl hydrocarbon hydroxylase (AHH) were significantly depressed in 7SA cells by about 30%. The inducibility of AHH by BaP treatment was depressed by 30-70% in MCA and 7SA cells over a 36-hr time course. 10T1/2 and MCA cells accumulated similar intracellular amounts of 3-OH-BaP by 12 and 24 hr, respectively; in contrast the accumulation of 3-OH-BaP in 7SA cells was 70% lower. During 36 hr of BaP treatment, total BaP-DNA adduct levels formed in 7SA and MCA cells, determined by 32P-postlabeling analysis, were 90 and 83% lower, respectively, than those found in 10T1/2 cells. These differences in response to BaP treatment were not related to cellular differences in the uptake or efflux of BaP. Relative to 10T1/2 or MCA cells, 7SA cells were found to have at least a twofold increase in UDP-glucuronyltransferase activity, which correlated with the lower intracellular accumulation of 3-OH-BaP and enhanced formation of extracellular polar metabolites. MCA cells had an almost twofold increase in glutathione S-transferase activity relative to parental 10T1/2 cells but produced lower levels of extracellular polar metabolites. These results demonstrate an association between chemical transformation of 10T1/2 cells and altered xenobiotic metabolism. This system may provide an in vitro model for examining the molecular events responsible for the biochemically altered phenotype of the malignantly transformed cell.     

A new lactoferrin- and iron-dependent lysosomal death pathway is induced by benzo[a]pyrene in hepatic epithelial cells

While lysosomal disruption seems to be a late step of necrosis, a moderate lysosomal destabilization has been suggested to participate early in the apoptotic cascade. The origin of lysosomal dysfunction and its precise role in apoptosis or apoptosis-like process still needs to be clarified, especially upon carcinogen exposure. In this study, we focused on the implication of lysosomes in cell death induced by the prototype carcinogen benzo[a]pyrene (B[a]P; 50 nM) in rat hepatic epithelial F258 cells. We first demonstrated that B[a]P affected lysosomal morphology (increase in size) and pH (alkalinization), and that these changes were involved in caspase-3 activation and cell death. Subsequently, we showed that lysosomal modifications were partly dependent on mitochondrial dysfunction, and that lysosomes together with mitochondria participate in B[a]P-induced oxidative stress. Using two iron chelators (desferrioxamine and deferiprone) and siRNA targeting the lysosomal iron-binding protease lactoferrin, we further demonstrated that both lysosomal iron content and lactoferrin were required for caspase-3 activation and apoptosis-like cell death.     

New 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-2-yl)propane derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants

Some benzo[b]thiophene derivatives with different substituents in positions 3 and 5 have been synthesized in order to obtain new dual antidepressant drugs. Compounds derived from 2-acetyl-3-methylbenzo[b]thiophene or 2-acetyl-3,5-dimethylbenzo[b]thiophene were prepared with two different phenylpiperazines (2-methoxy and 2-hydroxyphenylpiperazine) and evaluated for in vitro 5-HT1A receptor affinity and serotonin reuptake inhibition by radioligand assays. Compound 1-(3,5-dimethylbenzo[b]thiophen-2-yl)-3-[4-(2-methoxyphenyl)piperazin-1- yl]propan-1-ol (II.2.a) shows good values (nM) for both activities: Ki = 85 for 5-HT1A receptor and Ki = 120 for serotonin transporter.     

Rs710521[A] on chromosome 3q28 close to TP63 is associated with increased urinary bladder cancer risk

Single nucleotide polymorphism (SNP) rs710521[A], located near TP63 on chromosome 3q28, was identified to be significantly associated with increased bladder cancer risk. To investigate the association of rs710521[A] and bladder cancer by new data and by meta-analysis including all published data, rs710521 was studied in 1,425 bladder cancer cases and 1,740 controls that had not been included in previous studies. Blood samples were collected from 1995 to 2010 in Germany (n?=?948/1,258), Hungary (n?=?262/65), Venezuela (n?=?112/190) and Pakistan (n?=?103/227) supplemented by a meta-analysis of 5,695 cases and 40,187 controls. Detection of a A/G substitution (rs710521) on chromosome 3q28, position 191128627 was done via fast real-time polymerase chain reaction (rt-PCR). Rs710521[A] is associated with increased risk in the unadjusted analysis (OR?=?1.21; 95% Cl?=?1.04-1.40; P?=?0.011) and in the recessive model adjusted for age, gender, smoking habits and ethnicity (OR?=?1.23; 95% Cl?=?1.05-1.44; P?=?0.010). No difference between individuals occupationally exposed versus not occupationally exposed to urinary bladder carcinogens was observed concerning the relevance of rs710521[A]. Similarly, rs710521[A] did not confer different susceptibility in smokers and non-smokers. Performing a meta-analysis of 5,695 cases and 40,187 controls including all published studies on rs710521, a convincing association with bladder cancer risk was obtained (OR?=?1.18; 95% Cl?=?1.12-1.25; P?相似文献   

Omeprazole alleviates benzo[a]pyrene cytotoxicity by inhibition of CYP1A1 activity in human and mouse hepatoma cells

Omeprazole is a drug used for treating gastro-oesophageal reflux disease and duodenal ulcers. Omeprazole induces a xenobiotic-metabolizing enzyme, cytochrome P450 1A1 (CYP1A1), as its ligand by aryl hydrocarbon receptor (AhR) activation without binding. CYP1A1-inducible chemicals, such as benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin, are known to have adverse effects (i.e. carcinogenesis, mutagenesis and malformation). Unlike these typical AhR activators, omeprazole has shown no experimental evidence of carcinogenic activity. The possibility, however, remains that omeprazole may aggravate the effect of environmental carcinogens through CYP1A1 induction. We exposed benzo[a]pyrene and omeprazole simultaneously to human and mouse hepatoma cells to investigate the synergistic effect of these chemicals. Contrary to our prediction, cytotoxicity of benzo[a]pyrene was inhibited by the omeprazole exposure in a dose-dependent manner. Omeprazole did not alter CYP1A1 mRNA and protein levels induced by benzo[a]pyrene. The 7-ethoxy-resorufin-O-deethylase assay revealed that omeprazole inhibited CYP1A1 enzyme activity. Kinetic analysis also demonstrated that it is a competitive inhibitor for CYP1A1. The K(m) value of omeprazole against CYP1A1 activity was 50.1 microM. We conclude that the effects of omeprazole on CYP1A1 involve not only induction through AhR activation but also inhibition of its enzyme activity, and that the protective effect of omeprazole against benzo[a]pyrene cytotoxicity depends on the latter.