From Arene Oxides to Diol Epoxides and DNA

Although the polycyclic aromatic hydrocarbons (PAH) are structurally less complex compared to many other compounds with high biological activity, their metabolism, the chemical reactivity of their metabolites, and the mutagenicity and tumorigenicity of these metabolites have stimulated intensive research into their mechanisms of action. The present report focuses on our contributions to the identification of bay-region and fjord-region diol epoxides as ultimate carcinogens of the PAH and describes some of the remarkable stereochemical control involved in their synthesis, metabolic formation, and expression of tumorigenic activity.     

Synthesis and Structure Determination of the Adducts of Dibenzo[a,l]pyrene Diol Epoxides and Deoxyadenosine or Deoxyguanosine

Abstract

(±)?Syn?dibenzo[a,l]pyrene diol epoxide (DB[a,l]PDE) and (±)?anti?DB[a,l]PDE were reacted with deoxyadenosine (dA) or deoxyguanosine (dG) in dimethylformamide at 100 °C for 30 min. The crude products were purified by reverse phase HPLC under gradient and isocratic conditions. The structure of each adduct was assigned by 1D and 2D NMR spectra and by fast atom bombardment mass spectrometry. Five adducts were isolated from the reaction of (±)?syn?DB[a,l]PDE and dA: syn?DB[a,l]PDE?N⁶dA?1, syn?DB[a,l]PDE?N⁶dA?2, syn?DB[a,l]PDE?N⁶dA?3, syn?DB[a,l]PDE?N⁶dA?4 and syn?DB[a,l]PDE?N7Ade. Four adducts were isolated from the reaction of (±)?anti?DB[a,l]PDE and dA: anti?DB[a,l]PDE?N⁶dA?1, anti?DB[a,l]PDE?N⁶dA?2, anti?DB[a,l]PDE?N⁶dA?3 and anti?DB[a,l]PDE?N⁶dA?4. Two adducts were isolated from the reaction of (±)?syn?DB[a,l]PDE and dG: (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N²dG and (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N7Gua. Two adducts were isolated from the reaction of (±)?anti?DB[a,l]PDE and dG: (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N²dG and (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N7Gua.     

Synthesis of Stereoisomeric N 6-Deoxyadenosine Adducts of syn- and anti- Dihydrodiol Epoxides of Benzo[a]pyrene and Their Incorporation into 18-mer DNA Sequences from Human Ha-ras Protooncogene

Oligonucleotide sequences synthesized with specifically positioned and structurally defined adducts of dihydrodiol epoxides (DE) of polycyclic aromatic hydrocarbons like benzo[a]pyrene (B[a]P) are useful tools to study in detail the solution structure of corresponding duplexes by NMR techniques as well as the interaction of a single adduct with DNA polymerases. Here we report the successful incorporation of trans-N ⁶-dA-B[a]PDE adducts derived from the syn- and anti-diastereomers of B[a]PDE into 18-mer oligonucleotides representing partial human Ha-ras sequences surrounding codon 61 (CAG). The key step in our approach is a nucleophilic displacement reaction of a deoxyinosine derivative activated at the 6-position by a sulfonate group with a racemic aminotriol providing a regio- and stereospecific synthesis of the N ⁶-dA adducts. The aminotriol precursors are prepared by direct aminolysis of the DE's or by a stereoselective opening of the oxirane ring with sodium azide followed by reduction. The fully protected diastereomeric trans-N ⁶-dA-B[a]PDE adducts were separated by preparative HPLC and subsequently transformed into the corresponding phosphoramidites. The synthesis of four 18-mers was performed on a DNA synthesizer incorporating in each sequence [d(5′-GGC·CA*G·GAG·GAG·TAC·AGC-3′)] a single dA adduct (A*) at Codon 61 using standard phosphoramidite chemistry. After extensive purification of the 18-mers by reverse phase HPLC and analysis by PAGE, the presence of the trans-N⁶ -dA-B[a]PDE adducts in the oligonucleotides was confirmed by fluorescence spectroscopy.     

Synthesis of 2-Hydroxybenzo[a]pyrene,a Tumorigenic Phenol Derivative of Benzo[a]pyrene

An efficient synthesis of 2-hydroxybenzo[a]pyrene (1a) from 4,5,9,10-tetrahydropyrene via 2-methoxy-4,5,9,10-tetrahydropyrene (2e) is described. Friedel–Crafts acetylation of tetrahydropyrene affords the 2-acetyl derivative which is transformed to the 2-methoxy derivative 2e via Baeyer–Villager oxidation, hydrolysis, and treatment with dimethyl sulfate. Friedel–Crafts succinoylation of 2e with succinic anhydride and AlCl₃ takes place regiospecifically in the 7-position. The product is transformed to 1a via Clemmensen reduction, HF cyclization, Wolff–Kishner reduction, catalytic dehydrogenation, and demethylation with HBr.     

Influence of Benzo(a)pyrene on Different Epigenetic Processes

Epigenetic changes constitute one of the processes that is involved in the mechanisms of carcinogenicity. They include dysregulation of DNA methylation processes, disruption of post-translational patterns of histone modifications, and changes in the composition and/or organization of chromatin. Benzo(a)pyrene (BaP) influences DNA methylation and, depending on its concentrations, as well as the type of cell, tissue and organism it causes hypomethylation or hypermethylation. Moreover, the exposure to polyaromatic hydrocarbons (PAHs), including BaP in tobacco smoke results in an altered methylation status of the offsprings. Researches have indicated a potential relationship between toxicity of BaP and deregulation of the biotin homeostasis pathway that plays an important role in the process of carcinogenesis. Animal studies have shown that parental-induced BaP toxicity can be passed on to the F1 generation as studied on marine medaka (Oryzias melastigma), and the underlying mechanism is likely related to a disturbance in the circadian rhythm. In addition, ancestral exposure of fish to BaP may cause intergenerational osteotoxicity in non-exposed F3 offsprings. Epidemiological studies of lung cancer have indicated that exposure to BaP is associated with changes in methylation levels at 15 CpG; therefore, changes in DNA methylation may be considered as potential mediators of BaP-induced lung cancer. The mechanism of epigenetic changes induced by BaP are mainly due to the formation of CpG-BPDE adducts, between metabolite of BaP—BPDE and CpG, which leads to changes in the level of 5-methylcytosine. BaP also acts through inhibition of DNA methyltransferases activity, as well as by increasing histone deacetylases HDACs, i.e., HDAC2 and HDAC3 activity. The aim of this review is to discuss the mechanism of the epigenetic action of BaP on the basis of the latest publications.     

Phytoaccumulation of Benzo[a]pyrene by the Barley in Artificially Contaminated Soil

ABSTRACT

The assessment of toxic effects of polycyclic aromatic hydrocarbons (PAHs) on Haplic chernozems soil was developed by using spring barley (Hordeum sativum distichum) bioaccumulation tendencies. Spring barley was used to estimate the negative effect of chernozemic soil contamination with benzo[a]pyrene (BaP), one the most carcinogenic and mutagenic PAHs compounds. The bioaccumulation tendencies were studied in soil spiking with BaP. Spiked doses were close to technogenic pressure level in studied area, 0–800 µg/kg of BaP. Condition and doses of BaP during 4 years of model experiment influenced morphometric characteristics of spring barley and rates of BaP uptake by plants. Exposure to the growth characteristics containing at least 20 µg/kg BaP promoted absorbing BaP by plants root system as well as increased roots length. Tendencies of phytotoxicity parameters inhibition were observed for all morphometric characteristics of spring barley as energy of germination, length of vegetation part, plant weight and ear height. Quantifiable levels of BaP uptake by spring barley roots exceeded vegetative part more than 2.5 times in all polluted variants. The constant of BaP semi-degradation in artificially polluted Haplic chernozems for 48 months of model experiment T₅₀ reached 1.2–3.4 years. Thus, the BaP uptake by spring barley from chernozem soil contributes to the bioindication responses during environmental monitoring to assess the impact of BaP pollution.     

A Tandem Photochemical Approach for the Synthesis of Biologically Important Metabolites of Benzo[b]fluoranthene

A new photochemical approach for the synthesis of various metabolites of benzo[b]fluoranthene has been investigated, involving an oxidative photocyclization reaction of substituted cis-stilbenes to form the phenanthrene moiety, and an intramolecular photoarylation to generate the five-membered ring system. This methodology allowed a highly convergent synthesis of various benzo[b]-fluoranthene metabolites including those with an additional phenol group in the peninsular ring.     

用聚合物试剂减少煤沥青中3,4-苯并芘的研究

研究了用聚合物同煤沥青反应降低其中3,4-苯并芘的方法。实验采用3种聚合物同煤沥青反应,得出不同的聚合物对减少3,4-苯并芘的作用效果,通过对聚苯乙烯-丁二烯-苯乙烯、古马隆-茚树脂和聚乙二醇的研究发现:添加4%的古马隆-茚树脂对煤沥青中3,4-苯并芘的脱除效果较好,脱除率达到46.78%,最佳反应温度为270℃,煤沥青中的3,4-苯并芘的质量分数由1.43%降低到0.76%。     

Benzo[a]pyrene—Environmental Occurrence,Human Exposure,and Mechanisms of Toxicity

Benzo[a]pyrene (B[a]P) is the main representative of polycyclic aromatic hydrocarbons (PAHs), and has been repeatedly found in the air, surface water, soil, and sediments. It is present in cigarette smoke as well as in food products, especially when smoked and grilled. Human exposure to B[a]P is therefore common. Research shows growing evidence concerning toxic effects induced by this substance. This xenobiotic is metabolized by cytochrome P450 (CYP P450) to carcinogenic metabolite: 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), which creates DNA adducts, causing mutations and malignant transformations. Moreover, B[a]P is epigenotoxic, neurotoxic, and teratogenic, and exhibits pro-oxidative potential and causes impairment of animals’ fertility. CYP P450 is strongly involved in B[a]P metabolism, and it is simultaneously expressed as a result of the association of B[a]P with aromatic hydrocarbon receptor (AhR), playing an essential role in the cancerogenic potential of various xenobiotics. In turn, polymorphism of CYP P450 genes determines the sensitivity of the organism to B[a]P. It was also observed that B[a]P facilitates the multiplication of viruses, which may be an additional problem with the widespread COVID-19 pandemic. Based on publications mainly from 2017 to 2022, this paper presents the occurrence of B[a]P in various environmental compartments and human surroundings, shows the exposure of humans to this substance, and describes the mechanisms of its toxicity.     

Metabolic Activation of Benzo[a]pyrene by Human Tissue Organoid Cultures

Organoids are 3D cultures that to some extent reproduce the structure, composition and function of the mammalian tissues from which they derive, thereby creating in vitro systems with more in vivo-like characteristics than 2D monocultures. Here, the ability of human organoids derived from normal gastric, pancreas, liver, colon and kidney tissues to metabolise the environmental carcinogen benzo[a]pyrene (BaP) was investigated. While organoids from the different tissues showed varied cytotoxic responses to BaP, with gastric and colon organoids being the most susceptible, the xenobiotic-metabolising enzyme (XME) genes, CYP1A1 and NQO1, were highly upregulated in all organoid types, with kidney organoids having the highest levels. Furthermore, the presence of two key metabolites, BaP-t-7,8-dihydrodiol and BaP-tetrol-l-1, was detected in all organoid types, confirming their ability to metabolise BaP. BaP bioactivation was confirmed both by the activation of the DNA damage response pathway (induction of p-p53, pCHK2, p21 and γ-H2AX) and by DNA adduct formation. Overall, pancreatic and undifferentiated liver organoids formed the highest levels of DNA adducts. Colon organoids had the lowest responses in DNA adduct and metabolite formation, as well as XME expression. Additionally, high-throughput RT-qPCR explored differences in gene expression between organoid types after BaP treatment. The results demonstrate the potential usefulness of organoids for studying environmental carcinogenesis and genetic toxicology.     

Effect of Absolute Configuration on the Optical and NMR Properties of Oligonucleotides Containing Benzo[a]Pyrene Adducts at N 6 of Deoxyadenosine

For oligonucleotide duplexes derived from trans opening of benzo[a]pyrene diol epoxides (BaP DEs) by the exocyclic N⁶-amino group of deoxyadenosine (dA), the hydrocarbon is intercalated toward the 5′-end of the modified strand when the configuration at the site of attachment of the base to the hydrocarbon (C-10) is R, and toward the 3′-end when this configuration is S. In oligonucleotide 11-mer duplexes modified by BaP DE-1 (benzylic 7-OH and epoxide oxygen cis) and DE-2 (7-OH and epoxide oxygen trans), as well as 7,8,9,10-tetrahydro BaP 9,10-epoxide, 10R adducts had consistently higher (5–9d°C) T_m values than the corresponding 10S adducts. Dodecamer duplexes from the HPRT gene with trans opened 10S (but not those with 10R) BaP DE-2 adducts at either of two adjacent dA residues exhibited blue shifts at ～350 nm at temperatures well below the T_m. We propose that these blue shifts result from a conformation in which the hydrocarbon is not stacked with the DNA bases.     

6,7-甲氧基香豆素冠醚双功能化杯【4】芳烃的合成与表征

以对叔丁基杯[4]芳烃为原料,经碱催化两步合成了26,28-二（6,7-二甲氧基香豆素-4-亚甲基）-5,11,17,23-四叔丁基杯[4]芳烃-25,27-冠-6,产物经IR、^1H NMR表征和元素分析表征,该衍生物为锥形结构并与设计思想一致。     

Orally Subchronic Exposure to Benzo[a]pyrene Alters Reproductive Hormone Profile

The objective of this article was to assess whether benzo(a)pyrene (B[a]P) alters reproductive hormones, which in turn leads to decreased spermatozoa quality and spermatogenic cell levels. Hsd: ICR (CD1) 10-week old males were orally exposed to B[a]P at 1, 10, 50, and 100 mg/kg/day of body weight for 30 and 60 days. At the end of the experiment, mice were anesthetized and reproductive tissues, i.e., testes, seminal vesicles, and epididymis, were collected. Spermatogenic cells and mature spermatozoa were recovered from the testes and cauda epididymis, respectively. Spermatozoa quality, including concentration, morphology, motility, and viability, was examined. Testosterone, estradiol, follicle stimulating hormone (FSH), and luteinizing hormone (LH) levels in serum were determined using the Enzyme Immunoassay/Enzyme Linked Immunosorbent Assay (EIA/ELISA). Mice exposed to B[a]P at 50 mg/kg/day and 100 mg/kg/day for 30 days and 60 days exhibited a significantly decrease in serum testosterone and estradiol levels as compared with the control, while FSH and LH remained stable. The levels of testosterone and estradiol were positively correlated with decreased spermatozoa motility (p = 0.025 and 0.014, respectively), viability (p = 0.002 and 0.018, respectively), and morphology (p = 0.007 and 0.018, respectively), but the hormone levels did not correlate with spermatozoa levels. The testosterone and estradiol levels did not correlate with the levels of spermatogonia, pachytene spermatocytes, round spermatids, and elongated spermatids. Subchronic exposure to B[a]P could modulate the production of testosterone and estradiol, which subsequently influence spermatozoa quality.     

Review on the Concentrations of Benzo[a]pyrene in the Indian Environment Since 1983

The concentrations of benzo[a]pyrene [B(a)P] in the Indian environment since 1983 are reviewed. For this purpose, nearly sixty research papers on the determination of B(a)P in the Indian environment published in International journals were evaluated. The literature survey showed that the most of the research on determining the B(a)P levels in the Indian environment had been published in recent years. This review tabulated all the analytical parameters, such as extraction method, analyzed equipment, sampling medium, and detection limit in determination of B(a)P in the environment. This study also compares the concentration of B(a)P reported in the Indian environment with other Asian and Western countries. This review predicts that the concentrations of B(a)P reported in the ambient air of India were much higher than the Western countries, such as Germany, Italy, Greece, USA, and UK. On the other hand in Asian countries, the concentrations of B(a)P were reported in India were higher than the countries, such as Japan, Korea, Hong Kong, and Taiwan but comparable with China.     

高效液相色谱法检测植物油中苯并[a]芘的含量

建立并验证高效液相色谱法检测植物油中苯并[a]芘的含量.将植物油样品溶于正己烷中混匀,用苯并[a]芘固相萃取柱净化,用正己烷洗脱苯并[a]芘,荧光检测器检测.苯并[a]芘在0.1～100μg/kg浓度范围内线性相关系数r2=0.9999,本方法平均回收率为96.95%～101.30%,相对标准偏差RsD为0.980%～...     

Dual-Targeted Supramolecular Vesicles Based on the Complex of Galactose Capped Pillar[5]Arene and Triphenylphosphonium Derivative for Drug Delivery

In this study, a dual targeted supramolecular glycol-vesicle based on the host-guest complexation of galactose capped pillar[5]arene ( GALWP5 ) and triphenylphosphonium derivative ( D-TPP ) have been constructed ( GALWP5⊃D-TPP ), which showed dual target potential (cell and mitochondria targeting) resulting from its galactose units and TPP units, respectively. The dual targeted glycol-vesicle displays ignorable cytotoxicity and good mitochondria targeting. Our work presents a good example of rational design for an effective cell and subcellular organelles dual targeted delivery system.     

Comparison of the Morphological Transforming Activities of Fjord-Region PAHs with Dibenzo[a,e]Pyrene and Benzo[a]Pyrene

The morphological transforming activities in mouse embryo C3H10T1/2CL8 (C3H10T1/2) cells were examined for six PAHs: benzo[c]chrysene (B[c]C); benzo[g]chrysene (B[g]C); benzo[c]phenanthrene (B[c]P); dibenzo[a, l]pyrene (DB[a, l]P); dibenzo[a,e]pyrene (DB[a,e]P) and benzo[a]pyrene (B[a]P). C3H10T1/2 cells treated with B[c]P or B[g]C at concentrations of 0–3 μg/ml did not produce any transformed Type II or III foci after 24 hr of exposure. Concurrent cytotoxicity was observed. Under the same conditions, B[a]P and B[c]C were active, with B[c]C approximately one-half the activity of B[a]P. However, after a 48-hr treatment, B[c]P and B[g]C gave significant activity measured as both foci/dish or the number of dishes exhibiting foci. After a 24-hr treatment, comparison of B[a]P with two dibenzopyrenes, DB[a, l]P and DB[a,e]P, gave activities in the order: DB[a, l]P > B[a]P > DB[a,e]P. After 48 hr of treatment, both B[a]P and DB[a,e]P had similar activities.     

羧基苯偶氮基杯[4]芳烃衍生物的合成、表征及光谱特性

以邻、间、对氨基苯甲酸和杯 [4]芳烃为原料 ,经重氮化 -偶联反应合成了发色邻、间、对羧基苯偶氮基杯 [4]芳烃 ,产物的结构经 IR,1H NMR和元素分析表征 ;研究了它们的生色原理和光谱性能。结果表明它们是一类新型指示剂和具有新型配位空腔的主体分子。     

芘冠醚双功能化杯[4]芳烃的合成与表征

以杯[4]芳烃为原料,经碱催化合成了26,28-双(1-乙酰基芘)-5,11,17,23-四叔丁基杯[4]-冠-6,产物结构经IR、1HNMR和元素分析表征。该衍生物为锥形结构。