The combination of benzo[a]pyrene and ultraviolet A causes an in vivo time-related accumulation of DNA damage in mouse skin

Polycyclic aromatic hydrocarbons, including benzo[a]pyrene (BaP), are ubiquitous environmental carcinogens. BaP is metabolized in vivo to reactive intermediates that become covalently bound to DNA and form BaP-DNA adducts, an initial event in carcinogenesis. Ultraviolet A (UVA) synergizes with BaP to significantly enhance genetic damage and accelerate carcinogenic processes. This study was initiated to investigate in vivo cellular changes related to carcinogenesis induced by repeated exposures to BaP plus UVA. Simulated chronic exposure to an environmental carcinogen and sunlight was conducted through biweekly topical application of BaP followed 2 h later by UVA exposure over a 10 week period. BaP diol epoxide (BPDE)-DNA adducts were measured in vivo by immunohistochemistry using an anti-BPDE-DNA monoclonal antibody. Oxidative DNA damage was measured by the detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation using high-performance liquid chromatography. Alterations in the cell cycle that were relevant to carcinogenesis were revealed by changes in p53, as identified in vivo using a polyclonal anti-p53 antibody. We found that cells containing BPDE-DNA adducts and nuclear p53 expression significantly increased between 2 and 10 weeks of BaP-UVA treatment, whereas neither BPDE-DNA adducts nor significant changes in p53 were observed in untreated skin. Using regression analysis, oxidative 8-OHdG damage also showed a parallel increase over 2-10 weeks (r = 0.80). These results indicate that genetic damage caused by exposures to BaP plus UVA accumulates with time and increases the potential for inductive events leading to carcinogenesis and tumor formation.     

Mechanisms of reactive oxygen species photogeneration by benzo[a]pyrene: A DFT study

Benzo[a]pyrene (BaP) possesses photosensitive activity and can photogenerate reactive oxygen species (ROS), which have been postulated to be involved in the BaP induced oxidative DNA damage. Therefore, in the present work, a thermodynamic analysis on the ROS-photogenerating mechanisms of BaP was performed on the basis of quantum chemical calculations. It was revealed that: (i) the ¹O₂-generating pathway involves direct energy transfer from triplet excited state BaP to ³O₂ both in benzene and water; (ii) BaP gives birth to O₂^? through two pathways in water, i.e., electron transfer from triplet excited state BaP or anion radical of BaP to ³O₂.     

Photodynamic action of benzo[a]pyrene in K562 cells

Benzo[a]pyrene (BaP) is ubiquitously distributed in the environment, being considered the most phototoxic element among polycyclic aromatic hydrocarbon (PAHs). In presence of oxygen, PAHs can act as a photosensitizer by means of promoting photo-oxidation of biological molecules (photodynamic action, PDA). Thus, the present study analyzed the photodynamic action of BaP under UVA irradiation (BaP + UVA) and its oxidative effects on K562 cells. The evaluation of BaP kinetics showed that the highest intracellular concentration occurred after 18 h of incubation. Cell viability, reactive oxygen species (ROS) generation, lipid peroxidation, DNA damage (breaks and DNA-protein cross-link [DNAPC]) were assessed after exposure to BaP, UVA and BaP plus UVA irradiation (BaP + UVA). Cell viability was decreased just after exposure to BaP + UVA. Lipid peroxidation and DNA breaks increased after BaP + UVA exposure, while the DNAPC increased after BaP, UVA and BaP + UVA exposure, suggesting that BaP + UVA effects were a consequence of both type II (producing mainly singlet oxygen) and type I (producing others ROS) mechanisms of PDA.     

基于共价有机骨架修饰电极的苯并芘电化学发光传感器

苯并芘(BaP)是一种常见的多环芳烃类化合物,由于其对人体具有强烈的致癌性而引起广泛关注。该文将1,3,5-三醛基间苯三酚(CTp)与2,5-二甲基对苯二胺(Pa-2)经缩合反应形成的共价有机骨架材料CTpPa-2通过滴涂法修饰于电极表面,并与鲁米诺-过氧化氢体系相结合,构建了一种简单快速、稳定性好的BaP电化学发光传感器。通过扫描电子显微镜、差分脉冲伏安法、循环伏安法、恒电流充放电法及电化学发光法表征CTpPa-2修饰电极的形貌和电化学性能,并考察对BaP测定的可行性。在优化实验条件下,发光强度与苯并芘浓度在50～600 nmol/L范围内呈良好的线性关系,相关系数(r~2)为0.995 1,检出限(S/N=3)为5.60 nmol/L。将该方法应用于烤肉样品中BaP的检测,结果与高效液相色谱(HPLC)法相近,表明该方法具有良好的应用前景。     

Simultaneous detection of monohydroxybenzo[a]pyrene positional isomers by reversed-phase liquid chromatography coupled to electrospray ionization mass spectrometry

A liquid chromatographic (LC) method has been developed for the separation of 11 monohydroxybenzo[a]pyrenes (OH BaPs) positional isomers, and for their detection using electrospray ionization mass spectrometry (ESI-MS). All OH BaPs isomers were separated on an octadecylsilyl (C(18))-bonded amorphous organosilica column utilizing gradient elution with acetonitrile-water and triethylamine (TEA) at pH 11.0 and determined by MS, except 2- and 8-OH BaPs which were coeluted. The lower detection limits were in the range from 1.6 micro g/L for 12-OH BaP to 12 micro g/L for 5-OH BaP without any sample enrichment. The relative standard deviations of area response were in the range from 1.8% (9-OH BaP) to 4.9% (12-OH BaP) except for 9.4% (7-OH BaP). The developed method was successfully applied to incubation mixtures of BaP and CYP1A1/epoxide hydrolase. This method identified 1-, 3- and 9-OH BaPs as the major metabolites, and 2- (and/or 8-) and 12-OH BaPs as the minor metabolites in the incubation mixture.     

Studies of the Photochemical Degradation Kinetics of BaP on Different Substrates: Formation of Oxygenated Compounds

Abstract

The rate constant for BaP decomposition induced by exposure to UV rays and rate constants for BaP1,6; 3,6; 6,12 diones formation were determined. Experiments were conducted by depositing the BaP on clean glass fiber-filter and on airborne paniculate collected by filter. The BaP half-life appears to be positively correlated with filter loading and airborne particulates protect BaP from UV degradation. Our results suggest that BaP1,6dione, BaP3,6dione, BaP6,12dione are not the main by-products of BaP photodegradation induced by UV.     

BaP4Te2--a ternary telluride with P-Te bonds and a structural fragment of black phosphorus

The new telluride BaP(4)Te(2) was synthesized in form of gleaming black needles by heating stochiometric mixtures of the elements to 475 degrees C for 100 h. The crystal structure was determined by single-crystal Xray methods. BaP(4)Te(2) crystallizes orthorhombically, space group Pnma with a=16.486(8), b=6.484(2), c=7.076(4) A, and Z=4. A main feature of the so far unknown crystal structure type are P(4)Te(2) chains that consist of condensed six-membered rings of phosphorus. These strands are equivalent to a structural fragment of black phosphorus, in which each of the lateral atoms is connected to a tellurium atom. The chains running along [0 1 0] are separated from each other by barium atoms, that is, linked through Ba-Te and Ba-P bonds. BaP(4)Te(2) is an electron precise compound according to the Zintl concept, and the formula can be split ionically as follows: BaP(4)Te(2) identical with Ba(2+)(P(0))(4)(Te(-))(2). The remarkable Te-P bonds have been analyzed by electronic structure calculations using the electron localization function (ELF) and the crystal orbital Hamiltonian population (COHP) methods.     

Room temperature phosphorescence optosensing of benzo[a]pyrene in water using halogenated molecularly imprinted polymers

A selective optosensor for benzo[a]pyrene (BaP) determination in water samples, using a molecularly imprinted polymer (MIP) for the recognition of the analyte, has been developed. Detection was based on measurements of the native strong room temperature phosphorescence (RTP) emission from the BaP recognized by the MIP. The non-covalent MIP was synthesized using BaP as a molecular template. Different halogenated-bisphenol A compounds were compared as precursors in the polymerization (thus ensuring the presence of a heavy atom, required to induce RTP emission from the analyte). In the developed optosensor, samples are injected in a flow system and the analyte is on-line retained onto the polymeric material. In the absence of oxygen (using sodium sulfite as the oxygen scavenger) the heavy atom present in the MIP structure induced analytically useful RTP emission from the recognized BaP. After measurement of the luminescent emission, the sensing material can be easily regenerated by passing 2 mL of methanol over the MIP. The optosensor demonstrated a very high selectivity for BaP determination in water even in the presence of other luminophores that could be non-specifically adsorbed onto the MIP surface. Under optimal experimental conditions, a benzo[a]pyrene detection limit of 10 ng L(-1) (20 mL sample injection volume) was achieved with good reproducibility (a RSD of 3% was obtained for 1 microg L(-1) BaP). Finally, the proposed optosensor was successfully applied to the analysis of spiked natural water with BaP.     

Determination of some polycyclic aromatic hydrocarbons in filter tar of Turkish cigarettes

A simultaneous determination method for the analysis of benzo[a]pyrene (BaP) and dibenzo[a,h]anthracene (DahA) in the filter tar of Turkish cigarettes has been developed. The method involved (a) the extraction of BaP and DahA with n-hexane from ACN solution in which the cigarette filters were extracted, and then (b) purification of the n-hexane extracts by elution on an XAD-2 column using n-hexane/dichloromethane (9:1, v/v) mixture. Separation and quantitative determination of BaP and DahA in the extracts were carried out by HPLC and fluorescence detection on a C18 RP column. The calculated recoveries for BaP and DahA were found in the range of 90-100% for each extraction and clean-up steps. Analysis of various filter tar of Turkish cigarettes showed that an average of 74.28 ng/filter of BaP and 5.24 ng/filter of DahA were present in Turkish cigarettes.     

A simple method for the determination of benzo[a]pyrene and benzo[k]fluoranthene in a mixture

Atmospheric particulate matter is routinely analysed for the concentration of the carcinogen benzo[a]pyrene (BaP). Benzo[k]fluoranthene (BkF) has identical spectral characteristics and interferes in the fluorimetric estimation. A simple method for the determination of BaP in the presence of BkF is described. Based on quenching of the fluorescence of BaP by the addition of small amounts of nitromethane, the method can be used for accurate estimation for wide concentration ratios of BaP to BkF ranging from 0.1 to 10.0.     

Molecular Mechanisms of Action of Selected Substances Involved in the Reduction of Benzo[a]pyrene-Induced Oxidative Stress

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) primarily formed by burning of fossil fuels, wood and other organic materials. BaP as group I carcinogen shows mutagenic and carcinogenic effects. One of the important mechanisms of action of (BaP) is its free radical activity, the effect of which is the induction of oxidative stress in cells. BaP induces oxidative stress through the production of reactive oxygen species (ROS), disturbances of the activity of antioxidant enzymes, and the reduction of the level of non-enzymatic antioxidants as well as of cytokine production. Chemical compounds, such as vitamin E, curcumin, quercetin, catechin, cyanidin, kuromanin, berberine, resveratrol, baicalein, myricetin, catechin hydrate, hesperetin, rhaponticin, as well as taurine, atorvastatin, diallyl sulfide, and those contained in green and white tea, lower the oxidative stress induced by BaP. They regulate the expression of genes involved in oxidative stress and inflammation, and therefore can reduce the level of ROS. These substances remove ROS and reduce the level of lipid and protein peroxidation, reduce formation of adducts with DNA, increase the level of enzymatic and non-enzymatic antioxidants and reduce the level of pro-inflammatory cytokines. BaP can undergo chemical modification in the living cells, which results in more reactive metabolites formation. Some of protective substances have the ability to reduce BaP metabolism, and in particular reduce the induction of cytochrome (CYP P450), which reduces the formation of oxidative metabolites, and therefore decreases ROS production. The aim of this review is to discuss the oxidative properties of BaP, and describe protective activities of selected chemicals against BaP activity based on of the latest publications.     

Palladium-catalyzed synthesis of nucleoside adducts from bay- and fjord-region diol epoxides

Palladium-catalyzed C-N bond formation has been utilized to synthesize covalent 2'-deoxyadenosine (dA) and 2'-deoxyguanosine (dG) adducts of benzo[a]pyrene (BaP) series 1 (syn) and benzo[c]phenanthrene (BcPh) series 2 (anti) diol epoxides. For this, (+/-)-10 alpha-amino-7 beta,8 alpha,9 beta-trisbenzoyloxy-7,8,9,10-tetrahydro BaP and (+/-)-1 beta-amino-2 alpha,3 alpha,4 beta-trisbenzoyloxy-1,2,3,4-tetrahydro BcPh were coupled with 6-halo-9-[3,5-bis-O-(tert-butyldimethylsilyl)-beta-D-erythro-pentofuranosyl]purine and O6-benzyl-3',5'-bis-O-(tert-butyldimethylsilyl)-2-bromo-2'-deoxyinosine, using a (+/-)-BINAP-Pd complex and Cs2CO3. For the synthesis of the dA adducts, both the 6-chloro- as well as the 6-bromopurine nucleoside derivatives were analyzed for the C-N coupling reaction with the hydrocarbon amino tribenzoates. With the BaP amino tribenzoate, the 6-chloronucleoside provided satisfactory results, whereas the 6-bromo analogue proved to be superior with the BcPh amino tribenzoate. Overall, lower yields of the dA adducts were obtained with the more hindered fjord-region BcPh amino tribenzoate as compared to the bay-region BaP amino tribenzoate. In contrast to reactions leading to the dA adducts, the C-N reactions of both BaP and BcPh amino tribenzoates with the 2-bromo-2'-deoxyinosine derivative proceeded in comparable yields. This seems to indicate that such Pd-catalyzed adduct forming reactions at the C-6 position may be influenced by steric constraints of the amine component, whereas those at the C-2 position are less sensitive. Diastereomeric adduct pairs were separated and characterized by spectral methods and by comparisons to adducts produced by direct displacement reactions as well as those formed from DNA alkylation by diol epoxides.     

基于色相算法的表面等离子体共振成像传感器对苯并芘的敏感特性

报道了一种用于原位探测水中苯并芘的彩色表面等离子体共振成像(SPRI)传感器,该传感器既能提供直观的图像信息,又能借助色相算法定量分析待测物质的浓度及其吸附/脱附过程。首先利用自制的波长-图像同步检测型SPR传感器测试了裸金薄膜芯片在不同入射角下的共振波长和共振图像,然后利用色相算法建立了SPR共振波长与图像色相的依赖关系,基于该依赖关系获得了SPR传感器最佳色相灵敏度对应的起始共振波长约为650 nm;另一方面,制备了聚四氟乙烯涂覆的SPR传感芯片,基于聚四氟乙烯膜对水中苯并芘的可逆富集作用实现了苯并芘的原位快速探测。实验取得以下4个结果:(1)在20-100 nmol?L-1浓度范围内彩色SPR图像的平均色相值随着苯并芘浓度的升高线性减小;(2)对100 nmol?L-1的苯并芘的响应和恢复时间分别约为7和5 s;(3)由于聚四氟乙烯膜的厚度大于SPR消逝场穿透深度,检测结果不受溶液折射率影响;(4)在聚四氟乙烯敏感膜厚度较小且不均匀的情况下,传感器容许获取敏感膜的不同厚度区域对苯并芘的色相灵敏度。实验结果有力地证明了这种彩色SPR图像传感器在生化物质检测中具有良好的应用前景。     

介孔TiO_2薄膜光波导共振传感器对苯并(a)芘的探测灵敏度

采用溶胶-凝胶分子模板法在覆金的玻璃基底上制备了厚度约为295 nm的介孔TiO_2薄膜,再经表面化学修饰形成表面疏水的光波导共振(OWR)传感芯片,用于探测水中苯并(a)芘。利用Kretschmann棱镜耦合结构观测到OWR芯片在可见-近红外波段只有一个共振波谷,基于相位匹配条件确定了该共振波谷对应于二级横磁导模(TM2);进一步利用Fresnel理论并结合Bruggeman介电常数近似方程对实验测得的导模共振波长进行拟合,得出介孔TiO_2薄膜的多孔度约为0.4;利用疏水介孔TiO_2薄膜OWR传感芯片对水中苯并(a)芘小分子进行了原位和离位探测,结果表明离位探测灵敏度比原位探测高2倍多,其最低检测限约为100 nmol·L~(-1);对比实验指出OWR传感芯片的多孔结构和疏水化处理都有助于提高芯片对苯并(a)芘的探测灵敏度。研究表明这种介孔TiO_2薄膜OWR传感芯片具有良好的稳定性,可重复利用。     

Electrochemical DNA biosensor for the determination of benzo[a]pyrene–DNA adducts

The metabolites of the environmental pollutant, benzo[a]pyrene (BaP) are carcinogenic and mutagenic agents. Thus, the determination of additional products (adducts) of the interaction between DNA and BaP, attracts great interest in cancer research.

In this study, the determination of interaction between BaP and calf thymus double-stranded DNA (dsDNA) was performed by using differential pulse voltammetry (DPV) and constant current chronopotentiometric stripping analysis (PSA) in connection with carbon paste electrode (CPE) or glassy carbon electrode (GCE). As a result of interaction of BaP with dsDNA, the signal obtained from the oxidation of guanine decreased and a new adduct signal at a more positive potential appeared. This new peak is attributed to the formation of an adduct from the interaction of guanine with BaP. The chemically prepared anti-7,8,9,10-tetrahydrobenzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) adduct by using iodine oxidation was analyzed and the electrochemical signal of the adduct was observed. When the dsDNA modified GCE was immersed into various concentrations of BaP solution, the oxidation peak of guanine decreased and the adduct peak increased with the increasing BaP concentration. The partition coefficient was also obtained from the peak of BaP with dsDNA. The results revealed that the formation of adducts could be determined by using electrochemical DNA biosensors, which are fast, simple and cost-effective devices. Furthermore, this study promises that the analysis of other important adducts would benefit from the introduction of electrochemical methods.     

Contribution to the fluorometric method of analysis for atmospheric benzo(a)pyrene

Summary The potentiality of the method for the determination of benzo(a)pyrene (BaP) in airborne particulates, based on the fluorescence measurements in H₂SO₄, was investigated. Stability of the BaP fluorescence in H₂SO₄, isolation of the BaP fraction by thin-layer chromatography and the effect of quenchers on the fluorescence intensity of BaP were studied and the results are discussed. The relative standard deviation of the method was determined to be 2.9 and 5.9% for BaP levels of 265 and 68 ng, respectively.

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Beitrag zur fluorimetrischen Analyse von Benzo(a)pyren in der Atmosphäre

Zusammenfassung Die Möglichkeiten der Benzo(a)pyrenbestimmung durch Fluorescenzmessung in schwefelsaurer Lösung wurden untersucht. Die Stabilität der Fluorescenz, die Isolierung der Benzo(a)pyrenfraktion durch Dünnschicht-Chromatographie sowie der Einfluß fluorescenzlöschender Substanzen wurden geprüft und die Ergebnisse diskutiert. Die relative Standardabweichung des Verfahrens beträgt 2,9 und 5,9% für Benzo(a)pyrenmengen von 265 bzw. 68 ng.

     

Fast sequential injection determination of benzo[A]pyrene using variable angle fluorescence with on-line solid-phase extraction

A methodology for the analysis of drinking water for one of the most potent carcinogenic agents known; benzo[a]pyrene (BaP), in the presence of other interfering PAHs is presented. The methodology described is based on the sequential injection analysis of the sample on to a microcolumn (containing 5 mg of C18) where extraction and preconcentration of BaP takes place, followed by elution of BaP with 1 ml of 1,4-dioxane and subsequent detection by using variable angle fluorescence. The advantages of the method include the small amount of stationary phase employed together with the possibility of re-using the phase in order to carry out a large number of injections without the need for column re-packing. Also noteworthy is the small volume of 1,4-dioxane used to elute the BaP retained on the column and the small sample volumes required (9-10 ml) for achieving detection limits at the ng l-1 level. Thus, a methodology for BaP determination is obtained which complies with the requirements of the 98/83/EC Directive which fixes a maximum admissible concentration for this pollutant in waters for public consumption of 10 ng l-1. The variable angle spectra obtained are further processed by means of the multiple linear regression technique. The detection limit for BaP is 2.5 ng l-1, and the linear range is between 7.5 and 280 ng l-1.     

Isolation of Stable Mutagenic Photodecomposition Products of Benzo(a)pyrene by Thin-Layer Chromatography

Abstract

Polycyclic aromatic hydrocarbons (PAH) are widespread in the atmosphere, the soil, waterways and oceans, as well as in the food chain. Major sources of PAH include emissions from transportation systems, heat and power generating plants, refuse burning and industrial processes (1,2,3). A significant number of these PAH are known to be carcinogenic (2,4,5). Epidemiological studies indicate that the environment is a significant factor in the incidence of human cancer, although many of the specific causal agents remain to be identified. One widely studied PAH i s benzo(a)pyrene (BaP), which is a carcinogen, and one of the most common PAH contaminants of the environment (6). Occupational exposure t o BaP has been documented (4). Mailath and Morik (7) studied the effect of sunlight and dark-room storage on BaP and reported that six and eight compounds, respectively, were observed when BaP was exposed to sunlight or left in the dark. There have been several reports of the degradation of BaP adsorbed on soot or smoke particles (8,9,10).     

Thermodynamic stability and electron structure of polymeric sandwich complexes of porphyrins with different metals

The thermodynamic stability of different conformers of the polymeric sandwich structures of metalloporphyrins (MeP) is studied by means of quantum chemistry. The possibility of forming stable layered BaP, SrP, ScP, YP, and ZrP structures with shielded and retarded conformation is demonstrated. Shielded conformers are preferable in the case of SrP, BaP, and ScP complexes, while retarded conformers are most advantageous for YP and ZrP complexes. Based on the results from calculating the electron structure of the investigated compounds, we find that SrP and BaP are semiconductors and ScP, YP, and ZrP are electrical conductors     

Burial effects of organic coatings on the heterogeneous reactivity of particle-borne benzo[a]pyrene (BaP) toward ozone

With an aerosol flow tube coupled to an Aerodyne aerosol mass spectrometer (AMS), room temperature (296 ± 3 K) kinetics studies have been performed on the reaction of gas-phase ozone with benzo[a]pyrene (BaP) adsorbed in submonolayer amounts to dry ammonium sulfate (AS) particles. Three organic substances, i.e., bis(2-ethylhexyl)sebacate (BES, liquid), phenylsiloxane oil (PSO, liquid), and eicosane (EC, solid), were used to coat BaP-AS particles to investigate the effects of such organic coatings on the heterogeneous reactivity of PAHs toward ozone. All the reactions of particle-borne BaP with excess ozone exhibit pseudo-first-order kinetics in terms of BaP loss, and reactions with a liquid organic coating proceed by the Langmuir-Hinshelwood (L-H) mechanism. Liquid organic coatings did not significantly affect the kinetics, consistent with the ability of reactants to rapidly diffuse through the organic coating. In contrast, the heterogeneous reactivity of BaP was reduced substantially by a thin (4-8 nm), solid EC coating and entirely suppressed by thick (10-80 nm) coatings, presumably because of slow diffusion through the organic layer. Although the heterogeneous reactivity of surface-bound PAHs is extremely rapid in the atmosphere, this work is the first to experimentally demonstrate a mechanism by which the lifetime of PAHs may be significantly prolonged, permitting them to undergo long-range transport to remote locations.