RESUMO
Aldehyde dehydrogenases (ALDHs) are a family of enzymes that aid in detoxification and are overexpressed in several different malignancies. There is a correlation between increased expression of ALDH and a poor prognosis, stemness, and resistance to several drugs. Several ALDH inhibitors have been generated due to the crucial role that ALDH plays in cancer stem cells. All of these inhibitors, however, are either ineffective, very toxic, or have yet to be subjected to rigorous testing on their effectiveness. Although various drug-like compounds targeting ALDH have been reported in the literature, none have made it to routine use in the oncology clinic. As a result, new potent, non-toxic, bioavailable, and therapeutically effective ALDH inhibitors are still needed. In this study, we designed and synthesized potent multi-ALDH isoform inhibitors based on the isatin and indazole pharmacophore. Molecular docking studies and enzymatic tests revealed that among all of the synthesized analogs, compound 3 is the most potent inhibitor of ALDH1A1, ALDH3A1, and ALDH1A3, exhibiting 51.32%, 51.87%, and 36.65% inhibition, respectively. The ALDEFLUOR assay further revealed that compound 3 acts as an ALDH broad spectrum inhibitor at 500 nM. Compound 3 was also the most cytotoxic to cancer cells, with an IC50 in the range of 2.1 to 3.8 µM for ovarian, colon, and pancreatic cancer cells, compared to normal and embryonic kidney cells (IC50 7.1 to 8.7 µM). Mechanistically, compound 3 increased ROS activity due to potent multi-ALDH isoform inhibition, which increased apoptosis. Taken together, this study identified a potent multi-isoform ALDH inhibitor that could be further developed as a cancer therapeutic.
Assuntos
Aldeído Desidrogenase , Inibidores Enzimáticos , Isatina , Simulação de Acoplamento Molecular , Humanos , Isatina/química , Isatina/farmacologia , Aldeído Desidrogenase/antagonistas & inibidores , Aldeído Desidrogenase/metabolismo , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/síntese química , Linhagem Celular Tumoral , Antineoplásicos/farmacologia , Antineoplásicos/química , Antineoplásicos/síntese química , Relação Estrutura-Atividade , Isoenzimas/antagonistas & inibidores , Isoenzimas/metabolismo , Estrutura MolecularRESUMO
The aldehyde dehydrogenases (ALDHs) are a family of detoxifying enzymes that are overexpressed in various cancers. Increased expression of ALDH is associated with poor prognosis, stemness, and drug resistance. Because of the critical role of ALDH in cancer stem cells, several ALDH inhibitors have been developed. Nonetheless, all these inhibitors either lack efficacy or are too toxic or have not been tested extensively. Thus, the continued development of ALDH inhibitors is warranted. In this study, we designed and synthesized potent multi-ALDH isoform inhibitors based on the isatin backbone. The early molecular docking studies and enzymatic tests revealed that 3(a-l) and 4(a-l) are the potent ALDH1A1, ALDHA2, and ALDH3A1 inhibitors. ALDH inhibitory IC50s of 3(a-l) and 4(a-l) were 230 nM to >10,000 nM for ALDH1A1, 939 nM to >10,000 nM for ALDH2 and 193 nM to >10,000 nM for ALDH3A1. The most potent compounds 3(h-l) had IC50s for killing melanoma cells ranged from 2.1 to 5.7 µM, while for colon cancer cells, it ranged from 2.5 to 5.8 µM and for multiple myeloma cells ranging from 0.3 to 4.7 µM. Toxicity studies of 3(h-l) revealed that 3h to be the least toxic multi-ALDH isoform inhibitor. Mechanistically, 3(h-l) caused increased ROS activity, lipid peroxidation, and toxic aldehyde accumulation, secondary to potent multi-ALDH isoform inhibition leading to increased apoptosis and G2/M cell cycle arrest. Together, the study details the design, synthesis, and evaluation of potent, multi-isoform ALDH inhibitors to treat cancers.
Assuntos
Aldeído Desidrogenase/antagonistas & inibidores , Antineoplásicos/farmacologia , Desenho de Fármacos , Inibidores de Proteínas Quinases/farmacologia , Aldeído Desidrogenase/metabolismo , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Isoenzimas/antagonistas & inibidores , Isoenzimas/metabolismo , Camundongos , Simulação de Acoplamento Molecular , Estrutura Molecular , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/química , Relação Estrutura-AtividadeRESUMO
Mcl-1, a pro-survival member of the Bcl-2 protein family, is an attractive target for cancer therapy. We have recently identified the natural product marinopyrrole A (maritoclax) as a novel small molecule Mcl-1 inhibitor. Here, we describe the structure-activity relationship study of pyoluteorin derivatives based on maritoclax. To date, we synthesized over 30 derivatives of maritoclax and evaluated their inhibitory actions and cytotoxicity toward Mcl-1-dependent cell lines. As a result, several functional groups were identified in the pyoluteorin motif that significantly potentiate biological activity. A number of such derivatives, KS04 and KS18, interacted with Mcl-1 in a conserved fashion according to NMR spectroscopy and molecular modeling. KS04 and KS18 induced apoptosis selectively in Mcl-1-dependent but not Bcl-2-dependent K562 cells through selective Mcl-1 down-regulation, and synergistically enhanced apoptosis in combination with ABT-737. Moreover, the intraperitoneal administration of KS18 (10 mg/kg/d) and ABT-737 (20 mg/kg/d) significantly suppressed the growth of ABT-737-resistant HL-60 xenografts in nude mice without apparent toxicity. Overall, we identified the pharmacophore of pyoluteorin derivatives that act as potent and promising Mcl-1 antagonists against Mcl-1-dependent hematological cancers.
Assuntos
Apoptose/efeitos dos fármacos , Neoplasias Hematológicas/metabolismo , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Fenóis/farmacologia , Pirróis/farmacologia , Animais , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Modelos Animais de Doenças , Resistencia a Medicamentos Antineoplásicos , Sinergismo Farmacológico , Feminino , Neoplasias Hematológicas/patologia , Humanos , Modelos Moleculares , Conformação Molecular , Proteína de Sequência 1 de Leucemia de Células Mieloides/antagonistas & inibidores , Proteína de Sequência 1 de Leucemia de Células Mieloides/química , Fenóis/química , Fenóis/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Proteólise/efeitos dos fármacos , Pirróis/química , Pirróis/metabolismo , Células Estromais/efeitos dos fármacos , Células Estromais/metabolismo , Fatores de Tempo , Carga Tumoral/efeitos dos fármacos , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína X Associada a bcl-2/metabolismoRESUMO
We were the first to demonstrate that direct application of the environmental pollutant and tobacco smoke constituent dibenzo[a,l]pyrene (DB[a,l]P) into the oral cavity of mice induced squamous cell carcinoma (SCC) in oral tissues but not in the tongue; however, the mechanisms that can account for the varied carcinogenicity remain to be determined. Furthermore, we also showed that not only dA adducts, but also dG adducts can account for the mutagenic activity of DB[a,l]P in the oral tissues in vivo. In this study, we initially focused on DB[a,l]P-induced genotoxic effects in both oral and tongue tissues. Therefore, to fully assess the contribution of these DNA adducts in the initiation stage of carcinogenesis induced by DB[a,l]P, an LC-MS/MS method to simultaneously detect and quantify DB[a,l]PDE-dG and -dA adducts was developed. Mice were orally administered with DB[a,l]P (24 nmole, 3 times per week for 5 weeks) or its fjord region diol epoxide, (±)-anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DB[a,l]PDE, 12 nmole, single application); animals were sacrificed at 2, 7, 14, and 28 days after the last dose of carcinogen administration. Oral and tongue tissues were obtained and DNA were isolated followed by enzymatic hydrolysis. Following the development of an isotope dilution LC-MS/MS method, we successfully detected (-)-anti-cis- and (-)-anti-trans-DB[a,l]PDE-N(2)-dG, as well as (-)-anti-cis- and (-)-anti-trans-DB[a,l]PDE-N(6)-dA in oral and tongue tissues of mice treated with DB[a,l]P. Levels of (-)-anti-trans-DB[a,l]PDE-N(6)-dA were ≥2 folds higher than (-)-anti-cis-DB[a,l]PDE-N(6)-dA adduct and those of dG adducts in the oral tissues and tongue at all time points selected after the cessation of DB[a,l]P treatment. Levels of dG adducts were comparable in both tissues. Collectively, our results support that DB[a,l]P is predominantly metabolized to (-)-anti-DB[a,l]PDE, and the levels and persistence of (-)-anti-trans-DB[a,l]PDE-N(6)-dA may, in part, explain the carcinogenicity of DB[a,l]P in the oral tissues but not in the tongue.
Assuntos
Benzopirenos/toxicidade , Carcinógenos/toxicidade , Adutos de DNA/metabolismo , Desoxiadenosinas/metabolismo , Desoxiguanosina/metabolismo , Boca/efeitos dos fármacos , Animais , Cromatografia Líquida de Alta Pressão , Dicroísmo Circular , Adutos de DNA/análise , Poluentes Ambientais/toxicidade , Feminino , Espectroscopia de Ressonância Magnética , Camundongos , Boca/metabolismo , Espectrometria de Massas em TandemRESUMO
Honokiol possesses many pharmacological activities including anti-cancer properties. Here in, we designed and synthesized honokiol analogs that block major honokiol metabolic pathway which may enhance their effectiveness. We studied their cytotoxicity in human cancer cells and evaluated possible mechanism of cell cycle arrest. Two analogs, namely 2 and 4, showed much higher growth inhibitory activity in A549 human lung cancer cells and significant increase of cell population in the G0-G1 phase. Further elucidation of the inhibition mechanism on cell cycle showed that analogs 2 and 4 inhibit both CDK1 and cyclin B1 protien levels in A549 cells.
Assuntos
Antineoplásicos Fitogênicos/farmacologia , Compostos de Bifenilo/química , Compostos de Bifenilo/farmacologia , Lignanas/química , Lignanas/farmacologia , Antineoplásicos Fitogênicos/síntese química , Antineoplásicos Fitogênicos/química , Western Blotting , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , Neoplasias Pulmonares/patologia , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
Tobacco smoking is one of the leading causes for oral cancer. Dibenzo[a,l]pyrene (DB[a,l]P), an environmental pollutant and a tobacco smoke constituent, is the most carcinogenic polycyclic aromatic hydrocarbon (PAH) tested to date in several animal models (target organs: skin, lung, ovary, and mammary tissues). We have recently demonstrated that DB[a,l]P is also capable of inducing oral cancer in mice; however, its metabolic activation to the ultimate genotoxic metabolite dibenzo[a,l]pyrene-11,12-dihydrodiol-13,14-epoxide (DB[a,l]PDE) in mouse oral cavity has not been examined. Here we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to detect and quantify (±)-anti-DB[a,l]PDE-dA adducts in oral tissues of mice treated with DB[a,l]P. [(15)N(5)]-(±)-anti-DB[a,l]PDE-N(6)-dA adducts were synthesized as internal standards. The stereoisomeric adducts were characterized by MS, NMR, and CD analysis. The detection limit of the method is 8 fmol with 100 µg of digested DNA as the matrix. Two adducts were detected and identified as (-)-anti-cis and (-)-anti-trans-DB[a,l]PDE-dA in the oral tissues of mice following the direct application of DB[a,l]P (240 nmol per day, for 2 days) into the oral cavity, indicating that DB[a,l]P is predominantly metabolized into (-)-anti-DB[a,l]PDE in this target organ. We also compared the formation and removal of adducts as a function of time, following the direct application of DB[a,l]P (24 nmol, 3 times per week for 5 weeks) into the oral cavity of mice. Adducts were quantified at 48 h, 1, 2, and 4 weeks after the last dose. Maximal levels of adducts occurred at 48 h, followed by a gradual decrease. The levels (fmol/µg DNA) of (-)-anti-trans adducts (4.03 ± 0.27 to 1.77 ± 0.25) are significantly higher than (-)-anti-cis-DB[a,l]PDE-dA adduct (1.63 ± 0.42 to 0.72 ± 0.04) at each time point (p < 0.005). The results presented here indicate that the formation and persistence of (-)-anti-DB[a,l]PDE-dA adducts may, in part, contribute to the initiation of DB[a,l]P-induced oral carcinogenesis.
Assuntos
Benzopirenos/toxicidade , Carcinógenos Ambientais/toxicidade , Cromatografia Líquida de Alta Pressão/métodos , Adutos de DNA/análise , DNA/química , Mucosa Bucal/efeitos dos fármacos , Espectrometria de Massas em Tandem/métodos , Animais , Benzopirenos/química , Benzopirenos/metabolismo , Carcinógenos Ambientais/química , Carcinógenos Ambientais/metabolismo , Dicroísmo Circular , DNA/metabolismo , Adutos de DNA/isolamento & purificação , Compostos de Epóxi/química , Compostos de Epóxi/toxicidade , Feminino , Camundongos , Mucosa Bucal/metabolismo , EstereoisomerismoRESUMO
O(2)-[4-(3-Pyridyl)-4-oxobut-1-yl]thymidine (O(2)-POB-dThd) is the most persistent adduct detected in the lung and liver of rats treated with tobacco specific nitrosamines: N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). It is an important biomarker to assess the human exposure to these carcinogens. The only synthetic method reported for O(2)-POB-dThd requires repeated HPLC purifications and could only be used to prepare an analytical standard due to very low yield (0.4%). We have developed for the first time a regioselective and efficient method for the total synthesis of O(2)-POB-dThd and its site-specifically adducted oligonucleotides. The main step in the synthesis of O(2)-POB-dThd was achieved by a novel method. The treatment of O(2)-5'-anhydrothymidine with the sodium salt of 4-(1,3-dithian-2-yl)-4-(3-pyridyl)butan-1-ol gave exclusively the O(2)-alkylated adduct, which was deprotected in one step to furnish the desired O(2)-POB-dThd in excellent yield. The product was characterized by NMR ((1)H and (13)C), high-resolution MS, and HPLC analysis. This work provided for the first time a reliable method for large scale total synthesis of O(2)-POB-dThd that allowed for solid state site-specifically adducted oligomer synthesis. The O(2)-POB-dThd was converted to its phosphoramidite and subsequently used for the synthesis of oligodeoxynucleotides by standard methods. The oligomers were characterized by MS and HPLC analysis. These oligomers will facilitate the elucidation of the mutagenic potential of the O(2)-POB-dThd adduct, which will provide further insight into the role of tobacco-specific nitrosamines in inducing cancers in smokers.
Assuntos
Carcinógenos/química , Adutos de DNA/síntese química , Nicotiana/química , Nitrosaminas/química , Oligodesoxirribonucleotídeos/química , Piridinas/química , Piridinas/síntese química , Timidina/análogos & derivados , Sequência de Bases , Adutos de DNA/química , Humanos , Oligodesoxirribonucleotídeos/síntese química , Estereoisomerismo , Timidina/síntese química , Timidina/química , Poluição por Fumaça de Tabaco/análiseRESUMO
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, the role of the AHR in normal physiology is still an area of intense investigation. For example, this receptor plays an important role in certain immune responses. We have previously determined that the AHR can mediate repression of acute-phase genes in the liver. For this observation to be therapeutically useful, selective activation of the AHR would likely be necessary. Recently, the selective estrogen receptor ligand WAY-169916 has also been shown to be a selective AHR ligand. WAY-169916 can efficiently repress cytokine-mediated acute-phase gene expression (e.g., SAA1) yet fail to mediate a dioxin response element-driven increase in transcriptional activity. The goals of this study were to structurally modify WAY-169916 to block binding to the estrogen receptor and increase its affinity for the AHR. A number of WAY-169916 derivatives were synthesized and subjected to characterization as AHR ligands. The substitution of a key hydroxy group for a methoxy group ablates binding to the estrogen receptor and increases its affinity for the AHR. The compound 1-allyl-7-trifluoromethyl-1H-indazol-3-yl]-4-methoxyphenol (SGA 360), in particular, exhibited essentially no AHR agonist activity yet was able to repress cytokine-mediated SAA1 gene expression in Huh7 cells. SGA 360 was tested in a 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated ear inflammatory edema model using C57BL6/J and Ahr(-/-) mice. Our findings indicate that SGA 360 significantly inhibits TPA-mediated ear swelling and induction of a number of inflammatory genes (e.g., Saa3, Cox2, and Il6) in C57BL6/J mice. In contrast, SGA 360 had no effect on TPA-mediated ear swelling or inflammatory gene expression in Ahr(-/-) mice. Collectively, these results indicate that SGA 360 is a selective Ah receptor modulator (SAhRM) that exhibits anti-inflammatory properties in vivo.
Assuntos
Compostos Alílicos/farmacologia , Anti-Inflamatórios/farmacologia , Indazóis/farmacologia , Pirazóis/química , Receptores de Hidrocarboneto Arílico/metabolismo , Compostos Alílicos/química , Animais , Anti-Inflamatórios/síntese química , Anti-Inflamatórios/química , Ciclo-Oxigenase 2/metabolismo , Regulação da Expressão Gênica , Células Hep G2 , Humanos , Indazóis/química , Interleucina-6/metabolismo , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Otite/induzido quimicamente , Otite/tratamento farmacológico , RNA Mensageiro/metabolismo , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/genética , Receptores de Estrogênio/antagonistas & inibidores , Receptores de Estrogênio/metabolismo , Proteína Amiloide A Sérica/metabolismo , Acetato de Tetradecanoilforbol/toxicidadeRESUMO
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor involved in the regulation of multiple cellular pathways, such as xenobiotic metabolism and Th17 cell differentiation. Identification of key physiologically relevant ligands that regulate AHR function remains to be accomplished. Screening of indole metabolites has identified indoxyl 3-sulfate (I3S) as a potent endogenous ligand that selectively activates the human AHR at nanomolar concentrations in primary human hepatocytes, regulating transcription of multiple genes, including CYP1A1, CYP1A2, CYP1B1, UGT1A1, UGT1A6, IL6, and SAA1. Furthermore, I3S exhibits an approximately 500-fold greater potency in terms of transcriptional activation of the human AHR relative to the mouse AHR in cell lines. Structure-function studies reveal that the sulfate group is an important determinant for efficient AHR activation. This is the first phase II enzymatic product identified that can significantly activate the AHR, and ligand competition binding assays indicate that I3S is a direct AHR ligand. I3S failed to activate either CAR or PXR. The physiological importance of I3S lies in the fact that it is a key uremic toxin that accumulates to high micromolar concentrations in kidney dialysis patients, but its mechanism of action is unknown. I3S represents the first identified relatively high potency endogenous AHR ligand that plays a key role in human disease progression. These studies provide evidence that the production of I3S can lead to AHR activation and altered drug metabolism. Our results also suggest that prolonged activation of the AHR by I3S may contribute to toxicity observed in kidney dialysis patients and thus represent a possible therapeutic target.
Assuntos
Hepatócitos/fisiologia , Indicã/toxicidade , Receptores de Hidrocarboneto Arílico/agonistas , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Linhagem Celular , Linhagem Celular Tumoral , DNA Complementar/genética , Regulação da Expressão Gênica , Inativação Gênica , Genes Reporter , Células Hep G2 , Humanos , Indicã/química , Indicã/farmacologia , Ligantes , Plasmídeos , Reação em Cadeia da Polimerase , RNA/genética , RNA/isolamento & purificação , RNA Neoplásico/genética , RNA Neoplásico/isolamento & purificação , Receptores de Hidrocarboneto Arílico/genética , Receptores de Hidrocarboneto Arílico/metabolismo , TransfecçãoRESUMO
Tobacco smoking is an important cause of human oral squamous cell carcinoma (SCC). Tobacco smoke contains multiple carcinogens include polycyclic aromatic hydrocarbons typified by benzo[a]pyrene (B[a]P). Surgery is the conventional treatment approach for SCC, but it remains imperfect. However, chemoprevention is a plausible strategy and we had previously demonstrated that 1,4-phenylenebis(methylene)selenocyanate (p-XSC) significantly inhibited tongue tumors-induced by the synthetic 4-nitroquinoline-N-oxide (not present in tobacco smoke). In this study, we demonstrated that p-XSC is capable of inhibiting B[a]P-DNA adduct formation, cell proliferation, cyclin D1 expression in human oral cells in vitro. In addition, we showed that dietary p-XSC inhibits B[a]P-DNA adduct formation, cell proliferation and cyclin D1 protein expression in the mouse tongue in vivo. The results of this study are encouraging to further evaluate the chemopreventive efficacy of p-XSC initially against B[a]P-induced tongue tumors in mice and ultimately in the clinic.
Assuntos
Anticarcinógenos/farmacologia , Benzo(a)pireno/antagonistas & inibidores , Carcinógenos/antagonistas & inibidores , Transformação Celular Neoplásica/efeitos dos fármacos , Boca/efeitos dos fármacos , Compostos Organosselênicos/farmacologia , Benzo(a)pireno/toxicidade , Carcinógenos/toxicidade , Linhagem Celular Tumoral , Sobrevivência Celular , Ciclina D1/metabolismo , Adutos de DNA/metabolismo , Humanos , Boca/metabolismo , Boca/patologia , Antígeno Nuclear de Célula em Proliferação/metabolismoRESUMO
Dibenzo[c,p]chrysene (DB[c,p]C) is the only hexacyclic polycyclic aromatic hydrocarbon having two fjord regions, both in different chemical environments. Its environmental presence and relative tumorigenic potency are not known due to the lack of synthetic standards. We report here the synthesis of dibenzo[c,p]chrysene (1), its proximate carcinogens, i.e., trans-1,2-dihydroxy-1,2-dihydro-DB[c,p]C (2) and trans-11,12-dihydroxy-11,12-dihydro-DB[c,p]C (3), and possible ultimate carcinogens, i.e., anti-trans-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-DB[c,p]C (4) and anti-trans-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydro-DB[c,p]C (5). The syntheses of 1 and the appropriately methoxy-substituted DB[c,p]C (12 and 27), key intermediates for the synthesis of its proximate and ultimate metabolites, were tried first using a Suzuki cross-coupling reaction. However, the cyclization of olefins (10 and 11) gave poor yields of the desired products. An alternate method was thus developed employing a photochemical approach. The in vitro metabolism of DB[c,p]C was established with the S9 fraction of liver homogenate from phenobarbital/beta-naphthoflavone-induced Sprague-Dawley rats. The major dihydrodiol formed was identified as the fjord region 11,12-dihydroxy-11,12-dihydro-DB[c,p]C, while the major and minor phenols were identified as 11-hydroxy-DB[c,p]C and 12-hydroxy-DB[c,p]C, respectively. Further, the DNA adduction studies with the calf thymus DNA led to a mixture of dA and dG adducts for both fjord region diol epoxides (4 and 5). Interestingly, the dA to dG ratio for 1,2-dihydroxy-3,4-epoxide was much higher (3.2) compared to that of 11,12-dihydroxy-13,14-epoxide (0.5).
Assuntos
Carcinógenos Ambientais/síntese química , Crisenos/síntese química , Neoplasias Experimentais/induzido quimicamente , Animais , Carcinógenos Ambientais/metabolismo , Carcinógenos Ambientais/toxicidade , Crisenos/metabolismo , Crisenos/toxicidade , Adutos de DNA/síntese química , Fígado/efeitos dos fármacos , Estrutura Molecular , Neoplasias Experimentais/metabolismo , Fenobarbital/farmacologia , Ratos , Ratos Sprague-Dawley , beta-Naftoflavona/farmacologiaRESUMO
The environmental pollutant 6-nitrochrysene (6-NC) is a potent carcinogen in several animal models including the rat mammary gland. 6-NC can be activated to intermediates that can damage DNA by simple nitroreduction, ring oxidation, or a combination of ring oxidation and nitroreduction. Only the first pathway (nitroreduction) has been clearly established, and DNA adducts derived from this pathway have been fully characterized in in vitro systems. We also showed previously that the second pathway, ring oxidation leading to the formation of the bay region diol epoxide of 6-NC, is not responsible for the formation of the major DNA adduct in the mammary gland of rats treated with 6-NC. Therefore, in the present study, we explored the validity of the third pathway that involves the combination of both ring oxidation and nitroreduction of 6-NC to form trans-1,2-dihydroxy-1,2-dihydro-6-hydroxylaminochrysene (1,2-DHD-6-NHOH-C). During the course of this study, we synthesized for the first time 1,2-DHD-6-NHOH-C, N-(deoxyguanosin-8-yl)-6-aminochrysene, and N-(deoxyguanosin-8-yl)-1,2-dihydroxy-1,2-dihydro-6-aminochrysene. Incubation of 1,2-DHD-6-NHOH-C with calf thymus DNA resulted in the formation of three adducts. Upon LC/MS combined with 1H NMR analyses, the first eluting adduct was identified as 5-(deoxyguanosin-N2-yl)-1,2-dihydroxy-1,2-dihydro-6-aminochrysene [5-(dG-N2-yl)-1,2-DHD-6-AC], the second eluting adduct was identified as N-(deoxyguanosin-8-yl)-1,2-dihydroxy-1,2-dihydro-6-aminochrysene, and the last was identified as N-(deoxyinosin-8-yl)-1,2-dihydroxy-1,2-dihydro-6-aminochrysene. We also report here for the first time that among those adducts identified in vitro, only 5-(dG-N2-yl)-1,2-DHD-6-AC is the major DNA lesion detected in the mammary glands of rats treated with 6-NC.
Assuntos
Crisenos/química , Crisenos/toxicidade , Adutos de DNA/química , Desoxiguanosina/análogos & derivados , Desoxiguanosina/química , Poluentes Ambientais/toxicidade , Glândulas Mamárias Animais/química , Glândulas Mamárias Animais/efeitos dos fármacos , Animais , Carcinógenos Ambientais/metabolismo , Carcinógenos Ambientais/toxicidade , Crisenos/metabolismo , Poluentes Ambientais/metabolismo , Feminino , RatosRESUMO
We determined the mutant fractions (MF) and mutational specificities in the cII gene in histologically confirmed normal, non-involved and tumor mammary tissues of female transgenic (Big Blue F344 x Sprague-Dawley)F1 rats treated with the environmental pollutant 6-nitrochrysene (6-NC). At 30 days of age, three groups were set up for oral treatment with 6-NC dissolved in trioctanoin, or trioctanoin alone once a week for 8 weeks. Two dose levels of 6-NC (100 and 200 micromol/rat) were selected on the basis of our previous carcinogenicity bioassays with CD rats. The rats were decapitated 32 weeks after the last carcinogen dose. Both incidence and multiplicity of mammary adenocarcinomas were significantly elevated in the high dose (36%, 0.57, P < 0.01) group but at the low dose these outcomes (16%, 0.23, P < 0.1) were not significantly different from those of control rats (3%, 0.03). The MF in normal, non-involved and tumor tissues from the mammary glands of 6-NC-treated rats were comparable. At the high and low doses, respectively (4.8 +/- 2.0, 3.2 +/- 2.1) the MF of 6-NC-treated rats, were significantly higher (P < 0.05) than that observed in control rats (1.2 +/- 0.6). Control mutants consisted primarily of GC --> AT transitions, whereas 6-NC-induced mutants were comprised of several major classes of mutations with GC --> TA, GC --> CG, AT --> GC and AT --> TA as the most prevalent. Further studies indicated that the structures of 6-NC-DNA adducts in the mammary tissue are consistent with the mutational specificities. This is the first report that defines the relationship between carcinogenesis and mutagenesis, as well as between structures of 6-NC-DNA adducts and mutation characteristics in the target organ in vivo.
Assuntos
Adenocarcinoma/induzido quimicamente , Adenocarcinoma/genética , Crisenos/toxicidade , Poluentes Ambientais/toxicidade , Neoplasias Mamárias Experimentais/induzido quimicamente , Neoplasias Mamárias Experimentais/genética , Fatores de Transcrição/genética , Adenoma/induzido quimicamente , Adenoma/genética , Administração Oral , Animais , Animais Geneticamente Modificados , Crisenos/administração & dosagem , Adutos de DNA/análise , Feminino , Fibroadenoma/induzido quimicamente , Fibroadenoma/genética , Mutação de Sentido Incorreto , Mutação Puntual , Ratos , Ratos Endogâmicos F344 , Valores de Referência , Proteínas ViraisRESUMO
Benzo[b]phenanthro[2,3-d]thiophene (BPT), and a number of its metabolites, including BPT-3,4-diol, BPT sulfoxide, BPT sulfone, and 3-hydroxyBPT were assessed for their mutagenic activity in Salmonella typhimurium strain TA100, and S. typhimurium base-specific strains TA7001, TA7002, TA7003, TA7004, TA7005, and TA7006. Among the compounds tested in strain TA100, BPT, BPT sulfone, and 3-hydroxyBPT did not show any significant mutagenic response in the presence of S9. In contrast BPT sulfoxide and BPT-3,4-diol (a precursor to the bay-region diol epoxide of BPT) showed significant mutagenic activity in the presence of S9. Surprisingly, BPT sulfoxide was nearly 3.3-fold more mutagenic than BPT-3,4-diol in the presence of S9. BPT sulfoxide also displayed intrinsic mutagenic activity, which was nearly 1.5-fold less than that displayed by BPT-3,4-diol in the presence of S9. In base specific tester strains, BPT sulfoxide was the most active metabolite in strains TA7002, TA7004, and TA7005 with S9 activation. In these strains, BPT-3,4-diol was 2- to 7-fold less mutagenic than BPT sulfoxide in the presence of S9. Only in strain TA7006, BPT-3,4-diol was four-fold more mutagenic than BPT sulfoxide. The fact that BPT sulfoxide is significantly more mutagenic than BPT-3,4-diol in S. typhimurium strain TA100 suggests that the formation of sulfoxide may be the principal pathway for the metabolic activation of BPT to mutagenic products. Based on the results from Tester Strain TA7005, it indicate that BPT and its most mutagenic metabolite BPT sulfoxide induce predominantly CG --> AT transversion, which is observed as the most frequent base substitution mutation of p53 tumor-suppressor gene in human lung cancer.
Assuntos
Mutagênicos/toxicidade , Pró-Fármacos/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Tiofenos/toxicidade , Animais , Relação Dose-Resposta a Droga , Fígado/metabolismo , Masculino , Mutagênicos/metabolismo , Pró-Fármacos/metabolismo , Ratos , Salmonella typhimurium/genética , Tiofenos/metabolismoRESUMO
Benzo[c]chrysene (BcC), an environmental pollutant, is a unique polycyclic aromatic hydrocarbon that possesses both a bay region and a fjord region in the same molecule. We previously demonstrated that both bay region and fjord region terminal rings are involved in the in vitro metabolism of BcC. In the present investigation, we prepared [14-(3)H]BcC and tested the hypothesis that BcC can be activated to both bay region and fjord region diol epoxides in female CD rats. At 6 weeks of age, rats were gavaged with a single dose of [14-(3)H]BcC (5 mg/rat; specific activity, 6.7 Ci/mmol) in 0.5 mL of trioctanoin. During the first 48 h, 20.3% of the dose was eliminated in the feces and 2.8% was eliminated in the urine. After 1 week, cumulatively, 23.2 and 3.5%, respectively, were eliminated. 3-Hydroxybenzo[c]chrysene, 10-hydroxybenzo[c]chrysene, and trans-7,8-dihydroxy-7,8-dihydrobenzo[c]chrysene were the major fecal metabolites. In urine, trans-1,2-dihydroxy-1,2-dihydrobenzo[c]chrysene, 2-hydroxybenzo[c]chrysene, (+/-)-1,t-2,t-3,c-4-tetrahydroxy-1,2,3,4-tetrahydrobenzo[c]chrysene, and (+/-)-9,t-10,t-11,c-12-tetrahydroxy-9,10,11,12-tetrahydrobenzo[c]chrysene were detected, primarily as glucuronic acid and sulfate conjugates. The identification of the two tetraols clearly indicates that both bay region and fjord region diol epoxides are formed as intermediates in the metabolism of BcC in vivo. The second goal of this study was to test the hypothesis that the location of the epoxide moiety (fjord vs bay region) determines the carcinogenic activity. Thus, we compared the carcinogenicity of the bay region (+/-)-anti-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydrobenzo[c]chrysene and the fjord region (+/-)-anti-9,10-dihydroxy-11,12-epoxy-9,10,11,12-tetrahydrobenzo[c]chrysene in the rat mammary gland. The results clearly showed that the fjord region diol epoxide is a potent mammary carcinogen, while the bay region diol epoxide lacks activity in this model assay. This is the first report on a comparison of mammary cancer induction by fjord and bay region diol epoxides derived from the same molecule. It further supports previous observations that fjord region diol epoxides are more carcinogenic than structurally related bay region diol epoxides.
Assuntos
Compostos de Epóxi/metabolismo , Compostos de Epóxi/toxicidade , Neoplasias Mamárias Experimentais/induzido quimicamente , Fenantrenos/metabolismo , Fenantrenos/toxicidade , Animais , Carcinógenos/química , Carcinógenos/metabolismo , Carcinógenos/toxicidade , Poluentes Ambientais/metabolismo , Poluentes Ambientais/toxicidade , Compostos de Epóxi/química , Fezes/química , Feminino , Neoplasias Mamárias Experimentais/metabolismo , Fenantrenos/química , Ratos , Urina/químicaRESUMO
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants. Due to its structural similarity with the potent carcinogen dibenzo[a,l]pyrene (DB[a,l]P) and because of its environmental presence, dibenzo[c,mno]chrysene (naphtho[1,2-a]pyrene, N[1,2-a]P) is of considerable research interest. We therefore developed an efficient synthesis of N[1,2-a]P, and examined its in vitro metabolism by male Sprague Dawley rat liver S9 fraction. Its mutagenic activity in S. typhimurium TA 100 and its morphological cell transforming ability in mouse embryo fibroblasts were evaluated. On the basis of spectral analyses, the in vitro major metabolites were identified as the fjord region dihydrodiol trans-9,10-dihydroxy-9,10-dihydro-N[1,2-a]P (N[1,2-a]P-9,10-dihydrodiol), the K-region diols N[1,2-a]P-4,5-dihydrodiol and N[1,2-a]P-7,8-dihydrodiol, and also the 1-, 3-, and 10-hydroxy-N[1,2-a]P; the structure of N[1,2-a]P-9,10-dihydrodiol was also confirmed by independent synthesis. In assays with S. typhimurium TA 100, N[1,2-a]P-9,10-dihydrodiol was half as mutagenic as (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (B[a]P-7,8-dihydrodiol) at > or =4 nmol/plate. N[1,2-a]P-9,10-dihydrodiol was much more mutagenic than N[1,2-a]P at all dose levels, suggesting that the N[1,2-a]P-9,10-dihydrodiol is the likely proximate mutagen of N[1,2-a]P. Evaluation of morphological cell transformation in C3H10T1/2C18 mouse embryo fibroblasts revealed that N[1,2-a]P was comparable to B[a]P. We further examined the pattern of in vitro adduct formation between calf thymus DNA and (+/-)-anti-9,10-dihydroxy-9,10-dihydro-11,12-epoxy-9,10,11,12-tetrahydro-N[1,2-a]P (N[1,2-a]PDE) and found that dG-adduct formation is 2.9-fold greater than dA-adduct formation. On the basis of our results and those reported in the literature, our working hypothesis is that N[1,2-a]P may be added to the list of potent carcinogens that includes DB[a,l]P. This hypothesis is currently being tested in our laboratory.