Evaluation of Pharmaceuticals for DNA Damage in the Chicken Egg Genotoxicity Assay (CEGA).

DNA damage is an established initiating event in the mutagenicity and carcinogenicity of genotoxic chemicals. Accordingly, assessment of this endpoint is critical for chemicals which are being developed for use in humans. To assess the ability of the Chicken Egg Genotoxicity Assay (CEGA) to detect genotoxic pharmaceuticals, a set of 23 compounds with different pharmacological and reported genotoxic effects was tested for the potential to produce nuclear DNA adducts and strand breaks in the embryo-fetal livers using the 32P-nucleotide postlabeling (NPL) and comet assays, respectively. Due to high toxicity, two aneugens, colchicine and vinblastine, and an autophagy inhibitor, hydroxychloroquine, could not be evaluated. Out of the 20 remaining pharmaceuticals, 10 including estrogen modulators, diethylstilbestrol and tamoxifen, antineoplastics cyclophosphamide, etoposide, and mitomycin C, antifungal griseofulvin, local anesthetics lidocaine and prilocaine, and antihistamines diphenhydramine and doxylamine, yielded clear positive outcomes in at least one of the assays. The antihypertensive vasodilator hydralazine and antineoplastics streptozotocin and teniposide, produced only DNA strand breaks, which were not dose-dependent, and thus, the results with these 3 pharmaceuticals were considered equivocal. No DNA damage was detected for 7 compounds, including the purine antagonist 6-thioguanine, antipyretic analgesics acetaminophen and phenacetin, antibiotic ciprofloxacin, antilipidemic clofibrate, anti-inflammatory ibuprofen, and sedative phenobarbital. However, low solubility of these compounds limited dosages tested in CEGA. Overall, results in CEGA were largely in concordance with the outcomes in other systems in vitro and in vivo, indicating that CEGA provides reliable detection of DNA damaging activity of genotoxic compounds. Further evaluations with a broader set of compounds would support this conclusion.

Origin of the TTC values for compounds that are genotoxic and/or carcinogenic and an approach for their re-evaluation.

The threshold of toxicological concern (TTC) approach is a resource-effective de minimis method for the safety assessment of chemicals, based on distributional analysis of the results of a large number of toxicological studies. It is being increasingly used to screen and prioritize substances with low exposure for which there is little or no toxicological information. The first step in the approach is the identification of substances that may be DNA-reactive mutagens, to which the lowest TTC value is applied. This TTC value was based on the analysis of the cancer potency database and involved a number of assumptions that no longer reflect the state-of-the-science and some of which were not as transparent as they could have been. Hence, review and updating of the database is proposed, using inclusion and exclusion criteria reflecting current knowledge. A strategy for the selection of appropriate substances for TTC determination, based on consideration of weight of evidence for genotoxicity and carcinogenicity is outlined. Identification of substances that are carcinogenic by a DNA-reactive mutagenic mode of action and those that clearly act by a non-genotoxic mode of action will enable the protectiveness to be determined of both the TTC for DNA-reactive mutagenicity and that applied by default to substances that may be carcinogenic but are unlikely to be DNA-reactive mutagens (i.e. for Cramer class I-III compounds). Critical to the application of the TTC approach to substances that are likely to be DNA-reactive mutagens is the reliability of the software tools used to identify such compounds. Current methods for this task are reviewed and recommendations made for their application.

Investigation of bisindole-linked pyrimidine moieties: synthesis using strantium-aluminum supported strontium aluminate nanophosphors catalyst, DNA reactivity, and in silico molecular docking studies.

In this communication, an innovative and straightforward protocol for the one-pot catalytic synthesis of bis(indolyl)pyrimidine derivatives and their DNA binding abilities is presented. The synthesis involves the condensation of indole with diverse substituted pyrimidine-5-carbaldehydes, employing cost-effective and reusable Sr-Al supported nanophosphors, specifically strontium aluminate (SrAl2O4), as a catalyst. In particular, this method does not require the use of toxic solvents. The Sr-Al supported nanophosphorus catalyst exhibited sustained activity over multiple cycles and showed no significant decline while maintaining its strictly heterogeneous properties. The bis(indolyl)pyrimidine derivatives were extensively characterized using spectroscopic and analytical techniques. Furthermore, the interaction between these derivatives and CT-DNA was investigated by absorption spectroscopy, viscosity measurement, and in silico molecular docking studies. Photoinduced cleavage studies demonstrated the photonuclease activity of the compound against pUC19 DNA upon exposure to UV-visible radiation.

Fabricate, advancement, molecular docking and DNA reactivity of preferred divalent metal(II) complexes attributing (E)-N'-((6-hydroxybenzo[d]oxazol-5-yl) methylene)isonicotinohydrazide.

A series of metal(II) complexes (M=Co (II), Ni(II) and Cu(II)) supported by Schiff base ligand (L=(E)-N'-((6-hydroxybenzo[d]oxazol-5-yl)methylene)isonicotinohydrazide) has been designed and developed from condensation of 6-hydroxybenzo[d]oxazole-5-carbaldehyde and isoniazid. The ligand (H2L) and its metal(II) complexes were structurally characterized utilizing a variety of physicochemical and spectroscopic approaches. The study shows that Schiff bases (H2L) act as monobasic tridentate ONO ligand and conform to octahedral geometry according to the general formula [M(HL)2]. Furthermore, the interaction of these complexes with CT-DNA was investigated at pH = 7.2, utilizing UV-visible absorption, and viscosity measurement. In order to determine the mechanism of binding of the metal(II) complexes to the B-DNA dodecamer, docking studies were conducted using an AutoDock Vina 1.2.0 tool. The photo induced cleavage reveals that the ligand (H2L) and its complexes have UV-visible photo nuclease properties against pUC19 DNA by agarose gel electrophoresis technique. Studies showed that the complexes evaluated firmly bind to CT-DNA via intercalative mode and provides a distinctive pattern of DNA binding.

Cashew nutshell liquid catalyzed green chemistry approach for synthesis of a Schiff base and its divalent metal complexes: molecular docking and DNA reactivity.

Cashew Nut Shell Liquid (CNSL) anacardic acid was used, for the first time, as a green and natural effective catalyst for the synthesis of a quinoline based amino acid Schiff base ligand from the condensation of 2-hydroxyquinoline-3-carbaldehyde with l-tryptophan via solvent-free simple physical grinding technique. The use of the nontoxic CNSL natural catalyst has many benefits over toxic reagents and the desired product was obtained in high yield in a short reaction time. The procedure employed is simple and does not involve column chromatography. Moreover, a series of metal(II) complexes (metal = iron(II), cobalt(II), nickel(II), and copper(II)) supported by the synthesized new quinoline based amino acid Schiff base ligand (L) has been designed and the compositions of the metal(II) complexes were examined by various analytical techniques. The findings imply that the 2-hydroxyquinoline-3-carbaldehyde amino acid Schiff base (L) serves as a dibasic tridentate ONO ligand and synchronizes with the metal(II) in octahedral geometry in accordance with the general formula [M(LH)2]. Molecular docking study of the metal(II) complexes with B-DNA dodecamer has revealed good binding energy. The conductivity parameters in DMSO suggest the existence of nonelectrolyte species. The interaction of these metal complexes with CT-DNA has shown strong binding via an intercalative mode with a different pattern of DNA binding, while UV-visible photo-induced molecular cleavage analysis against plasmid DNA using agarose gel electrophoresis has revealed that the metal complexes exhibit photo induced nuclease activity.

Zirconia-Cu(I) stabilized copper oxide mesoporous nano-catalyst: Synthesis and DNA reactivity of 1,2,4-oxadiazole-quinolinepeptidomimetics-based metal(II) complexes.

Contemporary research reveals an undemanding protocol for the catalytic synthesis of 1,2,4-oxadiazole-quinolinepeptide in the incidence of a cost-effective and reusable mesoporous ZrO2-supported Cu2O (Cu2ZrO3) catalyst. This paper depicts a unique system for peptide bond synthesis staying away from toxic solvents and reactants. The catalyst was reused for four cycles without noteworthy loss in the activity, and the catalyst was genuinely heterogeneous. The method followed a simple workup procedure, and no column chromatography was needed. Further, the synthesized 1,2,4-oxadiazole-quinolinepeptide ligand (L), and its complexes of type, [FeLCl2] and [CuL]Cl2 were synthesized and characterized by spectral and analytical techniques. An octahedral geometry has been projected for Fe(II) complexes, while the Cu(II) complex exhibits a square planar geometry. The binding properties of the complexes with CT-DNA were studied by absorption spectral analysis, followed by viscosity measurement and thermal denaturation studies. The photo-induced cleavage studies revealed that the complexes possess photonuclease activity against pUC19 DNA under UV-visible irradiation.

Assessment and characterization of DNA adducts produced by alkenylbenzenes in fetal turkey and chicken livers.

Formation of DNA adducts by five alkenylbenzenes, safrole, methyl eugenol, eugenol, and asarone with either α- or ß-conformation, was analyzed in fetal avian livers in two in ovo models. DNA reactivity of the carcinogens safrole and methyl eugenol was previously demonstrated in the turkey egg model, whereas non-genotoxic eugenol was negative. In the current study, alkenylbenzenes were also tested in the chicken egg model. Injections with alkenylbenzenes were administered to fertilized turkey or chicken eggs for three consecutive days. Three hours after the last injection, liver samples were evaluated for DNA adduct formation using the 32P-nucleotide postlabeling assay. DNA samples from turkey livers were also analyzed for adducts using mass spectrometry. In both species, genotoxic alkenylbenzenes safrole, methyl eugenol, α- and ß-asarone produced DNA adducts, the presence and nature of which, with exception of safrole, were confirmed by mass spectrometry, validating the sensitivity of the 32P-postlabeling assay. Overall, the results of testing were congruent between fetal turkey and chicken livers, confirming that these organisms can be used interchangeably. Moreover, data obtained in both models is comparable to genotoxicity findings in other species, supporting the usefulness of avian models for the assessment of genotoxicity as a potential alternative to animal models.

DNA-damaging activities of twenty-four structurally diverse unsubstituted and substituted cyclic compounds in embryo-fetal chicken livers.

DNA-damaging activities of twenty-four structurally diverse unsubstituted and substituted cyclic compounds were assessed in embryo-fetal chicken livers. Formation of DNA adducts and strand breaks were measured using the nucleotide 32P-postlabelling (NPL) and comet assays, respectively. Unsubstituted monocyclic benzene, polycyclic fused ring compound naphthalene, covalently connected polycyclic ring compound biphenyl, and heterocyclic ring compound fluorene did not produce DNA damage. Amino-substituted monocyclic compounds, aniline and p-phenylenediamine, as well as polycyclic 1-naphthylamine were also negative. In contrast, carcinogenic monocyclic methyl-substituted anilines: o-toluidine, 2,6-xylidine, 3,4-dimethylaniline, 4-chloro-o-toluidine; 2 methoxy-substituted methylaniline: p-cresidine; 2,4 and 2,6 diamino- or dinitro- substituted toluenes all produced DNA damage. Genotoxic polycyclic amino-substituted 2-naphthylamine, 4-aminobiphenyl, benzidine, methyl-substituted 3,2'-dimethyl-4-aminobiphenyl and 4-dimethylaminoazobenzene as well as amino- and nitro- fluorenes substituted at the 1 or 2 positions also were positive in at least one of the assays. Overall, the DNA damaging activity of cyclic compounds in embryo-fetal chicken livers reflected the type and position of the substitution on the aromatic ring. Additionally, substituted polycyclic compounds exhibited higher DNA-damaging potency compared to monocyclic chemicals. These results are congruent with in vivo findings in other species, establishing chicken eggs as a reliable system for structure-activity assessment of members of groups of related chemicals.