Monitoring of DNA Adducts in Humans and 32P-Postlabelling Methods. A Review

Worldwide research trends on aristolochic acids (1957-2017): Suggestions for researchers

Aristolochic acids and their derivatives are components of many traditional medicines that have been used for thousands of years, particularly in Asian countries. To study the trends of research into aristolochic acids and provide suggestions for future study, we performed the following work. In this paper, we performed a bibliometric analysis using CiteSpace and HistCite software. We reviewed the three phases of the development of aristolochic acids by using bibliometrics. In addition, we performed a longitudinal review of published review articles over 60 years: 1,217 articles and 189 review articles on the history of aristolochic acid research published between 1957 and 2017 were analyzed. The performances of relevant countries, institutions, and authors are presented; the evolutionary trends of different categories are revealed; the history of research into aristolochic acids is divided into three phases, each of which has unique characteristics; and a roadmap of the historical overview of aristolochic acid research is finally established. Finally, five pertinent suggestions for future research into aristolochic acid are offered: (1) The study of the antitumor efficacy of aristolochic acids is of value; (2) The immune activity of aristolochic acids should be explored further; (3) Researchers should perform a thorough overview of the discovery of naturally occurring aristolochic acids; (4) More efforts should be directed toward exploring the correlation between aristolochic acid mutational signature and various cancers; (5) Further efforts should be devoted to the research and review work related to analytical chemistry. Our study is expected to benefit researchers in shaping future research directions.

A personalized life: biomarker monitoring from cradle to grave

Considering the holy grail of future medical treatment being personalized medicines, biomarker research will become more and more the focus for attention not only to develop new medical treatment regimes, based on changes in biomarker patterns, but also for nutritional advice to guarantee a lifelong optimized health condition. The current review gives an outline of how personalized medicine can become established for actual medical treatment using new biomarker concepts. Starting from the development of biomarker research using mainly immunological techniques, the review gives an overview about biomarkers of prediction evolved and focuses on new methodology for the identification of biomarkers using hyphenated analytical techniques like metabolomics and lipidomics. The actual use of multivariate statistical methods in combination with metabolomics and lipidomics is discussed not only for medical treatment but also for precautionary risk identification in human biomonitoring studies.

Chemopreventive compounds--view from the other side

Increasing attention is being paid to the possibility of applying chemopreventive agents for the protection of individuals from cancer risk. The beneficial potential of chemoprotective compounds is usually well documented by extensive experimental data. To assure the desired effect, these compounds are frequently concentrated to produce dietary supplements for human use. The additive and synergistic effects of other food constituents are, however, frequently ignored. Even natural chemopreventive compounds have to be considered as xenobiotics. Thus, as much attention has to be paid to their testing prior to their wide application as is usual in drug development for human treatment. Unfortunately, much of the research in this area is solely based on simplified in vitro systems that cannot take into account the complexity of biotransformation processes, e.g. chemopreventive compound-drug interaction, effect on metabolism of endogenic compounds. Hence, the predicted chemopreventive potential is not attained in respect of cancer prevention; moreover, the administration of high doses of chemopreventive compounds might be even detrimental for the human health.

Redox cycling in the metabolism of the environmental pollutant and suspected human carcinogen o-anisidine by rat and rabbit hepatic microsomes

We investigated the ability of hepatic microsomes from rat and rabbit to metabolize 2-methoxyaniline (o-anisidine), an industrial and environmental pollutant and a bladder carcinogen for rodents. Using HPLC combined with electrospray tandem mass spectrometry, we determined that o-anisidine is oxidized by microsomes of both species to N-(2-methoxyphenyl)hydroxylamine, o-aminophenol, and one additional metabolite, the exact structure of which has not been identified as yet. N-(2-Methoxyphenyl)hydroxylamine is either further oxidized to 2-methoxynitrosobenzene (o-nitrosoanisole) or reduced to parental o-anisidine, which can be oxidized again to produce o-aminophenol. To define the role of microsomal cytochromes P450 (P450) in o-anisidine metabolism, we investigated the modulation of this metabolism by specific inducers and selective inhibitors of these enzymes. The results of the studies suggest that o-anisidine is a promiscuous substrate of P450s of rat and rabbit liver; because P450s of 1A, 2B, 2E, and 3A subfamilies metabolize o-anisidine in hepatic microsomes of both studied species. Using purified enzymes of rat and rabbit (P450s 1A1, 1A2, 2B2, 2B4, 2E1, 2C3, 3A1, and 3A6), reconstituted with NADPH:P450 reductase, the ability of P450s 1A1, 1A2, 2B2, 2B4, 2E1, and 3A6 to metabolize o-anisidine was confirmed. In the reconstituted P450 system, rabbit P450 2E1 was the most efficient enzyme metabolizing o-anisidine. The data demonstrate the participation of different rat and rabbit P450s in o-anisidine metabolism and indicate that both experimental animal species might serve as suitable models to mimic the fate of o-anisidine in human.

Investigation of enzymatic behavior of benzonase/alkaline phosphatase in the digestion of oligonucleotides and DNA by ESI-LC/MS

We have developed an ion-pairing HPLC-MS method that has sufficient separation power, selectivity, and sensitivity to investigate the enzymatic behavior of benzonase/alkaline phosphatase upon digestion of oligonucleotides and DNA. Mass spectrometry revealed that this enzyme pair can nonspecifically digest oligonucleotides and DNA into fragments ranging from 2 to 10 nucleotides, i.e., sizes suitable for routine mass spectrometric measurements. Trimers, tetramers, and pentamers are the most prominent digested products. This makes benzonase/alkaline phosphatase a promising choice for DNA and DNA adduct related studies that require a nonspecific enzyme. A computer software program developed in-house was critical in automating the processing of mass spectral data. The methodology described here provides a systematic approach for evaluating the behavior of DNA-cleaving enzymes by mass spectrometry.

Molecular mechanisms of antineoplastic action of an anticancer drug ellipticine

Ellipticine is a potent antineoplastic agent exhibiting the multimodal mechanism of its action. This article reviews the mechanisms of predominant pharmacological and cytotoxic effects of ellipticine and shows the results of our laboratories indicating a novel mechanism of its action. The prevalent mechanisms of ellipticine antitumor, mutagenic and cytotoxic activities were suggested to be intercalation into DNA and inhibition of DNA topoisomerase II activity. We demonstrated a new mode of ellipticine action, formation of covalent DNA adducts mediated by its oxidation with cytochromes P450 (CYP) and peroxidases. The article reports the molecular mechanism of ellipticine oxidation by CYPs and identifies human and rat CYPs responsible for ellipticine metabolic activation and detoxication. It also presents a role of peroxidases (i.e. myeloperoxidase, cyclooxygenases, lactoperoxidase) in ellipticine oxidation leading to ellipticine-DNA adducts. The 9-hydroxy- and 7-hydroxyellipticine metabolites formed by CYPs and the major product of ellipticine oxidation by peroxidases, the dimer, in which the two ellipticine skeletons are connected via N(6) of the pyrrole ring of one ellipticine molecule and C9 in the second one, are the detoxication metabolites. On the contrary, 13-hydroxy- and 12-hydroxyellipticine, produced by ellipticine oxidation with CYPs, the latter one formed also spontaneously from another CYP- and peroxidase-mediated metabolite, ellipticine N(2)-oxide, are metabolites responsible for formation of two ellipticine-derived deoxyguanosine adducts in DNA. The results reviewed here allow us to propose species, two carbenium ions, ellipticine-13-ylium and ellipticine-12-ylium, as reactive species generating two major DNA adducts seen in vivo in rats treated with ellipticine. The study forms the basis to further predict the susceptibility of human cancers to ellipticine.

Use of DNA Repair Enzymes in Electrochemical Detection of Damage to DNA Bases in Vitro and in Cells

Electrochemical measurements at mercury or solid amalgam electrodes offer a highly sensitive detection of DNA strand breaks. On the other hand, electrochemical detection of damage to DNA bases at any electrode is usually much less sensitive. In this paper, we propose a new voltammetric method for the detection of the DNA base damage based on enzymatic conversion of the damaged DNA bases to single-strand breaks (ssb), single-stranded (ss) DNA regions, or both. Supercoiled DNA exposed to UV light was specifically cleaved by T4 endonuclease V, an enzyme recognizing pyrimidine dimers, the major products of photochemical DNA damage. Apurinic sites (formed in dimethyl sulfate-modified DNA) were determined after treating the DNA with E. coli exonuclease III, an enzyme introducing ssb at the abasic sites and degrading one of the DNA strands. The ssb or ssDNA regions, or both, were detected by adsorptive transfer stripping alternating current voltammetry at the mercury electrode. This technique offers much better sensitivity and selectivity of DNA base damage detection than any other electrochemical method. It is not limited to DNA damage in vitro, but it can detect also DNA base damage induced in living bacterial cells.

Effects of suberoylanilide hydroxamic acid and trichostatin A on induction of cytochrome P450 enzymes and benzo[a]pyrene DNA adduct formation in human cells

In this study, we investigated the effects of histone deacetylase (HDAC) inhibitors suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) on the metabolism of polycyclic aromatic hydrocarbons (PAH) in human mammary carcinoma derived MCF-7 cells in culture. Benzo[a]pyrene (B[a]P) induces cytochrome P450 (CYP) 1A1, CYP1B1 and other xenobiotic metabolizing enzymes. Results from our study indicated a significant increase in CYP activity in comparison to vehicle control in cells treated with SAHA or TSA as measured by ethoxyresorufin-O-deethylase assay. However, co-treatment with 1.0 microM SAHA and BP, reduced the mRNA levels of CYP1B1 relative to B[a]P alone. When co-treated with 1.0 microM TSA and BP, a reduction in the mRNA levels of both CYP1A1 and CYP1B1 was observed relative to BP alone. We further investigated to ascertain if the differential expression and activity of CYP1A1 and CYP1B1 influenced levels of B[a]P DNA adduct formation. MCF-7 cells co-treated with B[a]P and SAHA or TSA formed DNA adducts, although no significant differences in levels of DNA binding were revealed. These results suggest that while CYP enzyme activity and gene expression were affected by the HDAC inhibitors SAHA and TSA, they had no apparent influence on B[a]P DNA binding.