RESUMO
A rule-based expert system (ES) was developed to predict chemical binding to the estrogen receptor (ER) patterned on the research approaches championed by Gilman Veith to whom this article and journal issue are dedicated. The ERES was built to be mechanistically transparent and meet the needs of a specific application, i.e. predict for all chemicals within two well-defined inventories (industrial chemicals used as pesticide inerts and antimicrobial pesticides). These chemicals all lack structural features associated with high affinity binders and thus any binding should be low affinity. Similar to the high-quality fathead minnow database upon which Veith QSARs were built, the ERES was derived from what has been termed gold standard data, systematically collected in assays optimized to detect even low affinity binding and maximizing confidence in the negatives determinations. The resultant logic-based decision tree ERES, determined to be a robust model, contains seven major nodes with multiple effects-based chemicals categories within each. Predicted results are presented in the context of empirical data within local chemical structural groups facilitating informed decision-making. Even using optimized detection assays, the ERES applied to two inventories of >600 chemicals resulted in only ~5% of the chemicals predicted to bind ER.
Assuntos
Sistemas Inteligentes , Substâncias Perigosas/toxicidade , Relação Quantitativa Estrutura-Atividade , Anti-Infecciosos/classificação , Anti-Infecciosos/toxicidade , Substâncias Perigosas/classificação , Praguicidas/classificação , Praguicidas/toxicidade , Receptores de Estrogênio/metabolismo , Testes de Toxicidade/métodosRESUMO
Regulatory agencies are charged with addressing the endocrine disrupting potential of large numbers of chemicals for which there is often little or no data on which to make decisions. Prioritizing the chemicals of greatest concern for further screening for potential hazard to humans and wildlife is an initial step in the process. This paper presents the collection of in vitro data using assays optimized to detect low affinity estrogen receptor (ER) binding chemicals and the use of that data to build effects-based chemical categories following QSAR approaches and principles pioneered by Gilman Veith and colleagues for application to environmental regulatory challenges. Effects-based chemical categories were built using these QSAR principles focused on the types of chemicals in the specific regulatory domain of concern, i.e. non-steroidal industrial chemicals, and based upon a mechanistic hypothesis of how these non-steroidal chemicals of seemingly dissimilar structure to 17ß-estradiol (E2) could interact with the ER via two distinct binding types. Chemicals were also tested to solubility thereby minimizing false negatives and providing confidence in determination of chemicals as inactive. The high-quality data collected in this manner were used to build an ER expert system for chemical prioritization described in a companion article in this journal.
Assuntos
Estrogênios/classificação , Animais , Disruptores Endócrinos/química , Disruptores Endócrinos/classificação , Disruptores Endócrinos/toxicidade , Estrogênios/toxicidade , Parabenos/química , Parabenos/classificação , Parabenos/toxicidade , Fenóis/química , Fenóis/classificação , Fenóis/toxicidade , Relação Quantitativa Estrutura-Atividade , Receptores de Estrogênio/metabolismo , Salicilatos/química , Salicilatos/classificação , Salicilatos/toxicidade , TrutaRESUMO
The toxicity of four quinones, 2,3-dimethoxy-1,4-naphthoquinone (DMONQ), 2-methyl-1,4-naphthoquinone (MNQ), 1,4-naphthoquinone (NQ), and 1,4-benzoquinone (BQ), which redox cycle or arlyate in mammalian cells, was determined in isolated trout (Oncorhynchus mykiss) hepatocytes. More than 70% of cells died in 3 h when exposed to BQ or NQ; 50% died in 7 h when exposed to MNQ, with no mortality compared to controls after 7 h DMONQ exposure. A suite of biochemical parameters was assessed for ability to discriminate these reactivity pathways in fish. Rapid depletion of glutathione (GSH) with appearance of glutathione disulfide (GSSG) and increased dichlorofluoroscein fluorescence were used as indicators of redox cycling, noted with DMONQ, MNQ, and NQ. Depletion of GSH with no GSSG accumulation, and loss of free protein thiol (PrSH) groups (nonreducible) indicated direct arylation by BQ. All toxicants rapidly oxidized NADH, with changes in NADPH noted later (BQ, NQ, MNQ) or not at all (DMONQ). Biochemical measures including cellular energy status, cytotoxicity, and measures of reactive oxygen species, along with the key parameters of GSH and PrSH redox status, allowed differentiation of responses associated with lethality. Chemicals that arylate were more potent than redox cyclers. Toxic pathway discrimination is needed to group chemicals for potency predictions and identification of structural parameters associated with distinct types of reactive toxicity, a necessary step for development of mechanistically based quantitative structure-activity relationships (QSARs) to predict chemical toxic potential. The commonality of reactivity mechanisms between rodents and fish was also demonstrated, a step essential for species extrapolations.
Assuntos
Benzoquinonas/toxicidade , Hepatócitos/efeitos dos fármacos , Naftoquinonas/toxicidade , Oncorhynchus mykiss/metabolismo , Vitamina K 3/toxicidade , Adenina/metabolismo , Animais , Benzoquinonas/química , Morte Celular/efeitos dos fármacos , Feminino , Glutationa/metabolismo , Dissulfeto de Glutationa/metabolismo , Masculino , Estrutura Molecular , Naftoquinonas/química , Oxirredução , Oxigênio/metabolismo , Piridinas/metabolismo , Relação Quantitativa Estrutura-Atividade , Espécies Reativas de Oxigênio/metabolismo , Compostos de Sulfidrila/metabolismo , Vitamina K 3/químicaRESUMO
The novel folate analogue AG2034, which was designed as an inhibitor of GARFT (glycinamide ribonucleotide formyltransferase), was evaluated in this phase I study under the auspices of The Cancer Research Campaign, UK. AG2034 blocks de novo purine synthesis through inhibition of GARFT. A total of 28 patients with histologically proven intractable cancers were enrolled. AG2034 was administered as a short intravenous infusion once every 3 weeks. 8 dose levels ranging from 1-11 mg/m(2)were evaluated with patients receiving up to 6 cycles. Dose-limiting toxicities in the form of mucositis, diarrhoea and vomiting were observed at doses of 6 mg/m(2)and above. Significant levels of thrombocytopenia, neutropenia and anaemia were also recorded. Other sporadic toxicities included fatigue and myalgia. The MTD with this schedule of AG2034 was 5 mg/m(2). Most side effects occurred more frequently with cumulative dosing. In keeping with this, pharmacokinetic analysis revealed evidence of drug accumulation. The AG2034 AUC(0-24)increased by a median of 184% (range 20-389%) from cycle 1 to 3 in all 10 patients examined. No objective antitumour responses were observed in the study.
Assuntos
Antineoplásicos/farmacocinética , Glutamatos/farmacocinética , Neoplasias/tratamento farmacológico , Pirimidinas/farmacocinética , Adulto , Idoso , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Área Sob a Curva , Diarreia/induzido quimicamente , Relação Dose-Resposta a Droga , Feminino , Glutamatos/administração & dosagem , Glutamatos/efeitos adversos , Humanos , Masculino , Pessoa de Meia-Idade , Mucosa Bucal/efeitos dos fármacos , Mucosa Bucal/patologia , Náusea/induzido quimicamente , Neoplasias/metabolismo , Neutropenia/induzido quimicamente , Pirimidinas/administração & dosagem , Pirimidinas/efeitos adversos , Estomatite/induzido quimicamente , Trombocitopenia/induzido quimicamente , Resultado do TratamentoRESUMO
A method to measure protein thiols (PrSH), reduced and oxidized, was adapted to determine PrSH depletion in isolated rainbow trout hepatocytes exposed to arylating agent 1,4-benzoquinone (BQ). Toxicant analysis revealed rapid conversion of BQ to 1, 4-hydroquinone (HQ) upon addition to hepatocytes. Hepatocytes exposed to 200 microM BQ+HQ showed 80% decline in glutathione (GSH) (1 h), 30% loss of PrSH (6 h), and no loss of viability (24 h). Recoverable oxidized PrSH was detected only after 24 h (200 microM BQ+HQ). Exposure to 600 microM BQ+HQ caused rapid (10 min) loss of > 90% GSH and > 60% PrSH, with eventual cell death. Half of the PrSH depletion at 6 h observed in hepatocytes exposed to 600 microM BQ+HQ was recoverable by reduction with dithiothreitol. Following the loss of GSH in hepatocytes exposed to 600 microM BQ+HQ, cellular PrSH were susceptible to direct arylation and oxidation. Rainbow trout hepatocytes, which contained 10-fold less GSH than rat cells, had a GSH:PrSH ratio of 1:82 compared with rat ratios of 1:2 to 1:6. The methods reported are useful for further study and discrimination of reactive modes of action needed for prediction of aquatic organism susceptibility to these types of toxicants.
Assuntos
Benzoquinonas/toxicidade , Glutationa/metabolismo , Fígado/efeitos dos fármacos , Oncorhynchus mykiss/metabolismo , Compostos de Sulfidrila/metabolismo , Alquilação , Animais , Benzoquinonas/metabolismo , Separação Celular , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Ditiotreitol , Feminino , Dissulfeto de Glutationa/metabolismo , Hidroquinonas/metabolismo , Fígado/citologia , Fígado/metabolismo , Masculino , OxirreduçãoRESUMO
PURPOSE: To identify a recommended phase II dose for the second generation glycinamide ribonucleotide transformylase (GARFT) inhibitor, AG2034, administered by intravenous bolus every 3 weeks without folate supplementation and to describe AG2034 pharmacokinetics. METHODS: Adults with advanced malignancies were enrolled in cohorts of three per dose level with expansion to six upon observation of dose-limiting toxicity (DLT). The maximum tolerated dose (MTD) was defined as the dose at which two of up to six patients experienced DLT. Upon identification of an MTD and evidence of cumulative toxicity, a lower intermediate dose was explored as a candidate phase II dose. AG2034 plasma concentrations were measured using an ELISA assay. RESULTS AND CONCLUSIONS: The recommended phase II dose is 5.0 mg/m2. DLTs were anemia, thrombocytopenia, mucositis, diarrhea, hyperbilirubinemia, fatigue, and insomnia. Toxicities were modestly cumulative over three courses. Pharmacokinetic analysis showed a dose-AUC0-24 relationship and a progressive increase in AG2034 AUC0-24 over three courses. Both pharmacokinetic and pharmacodynamic factors may contribute to the modest cumulative toxicity observed with AG2034.
Assuntos
Antineoplásicos/uso terapêutico , Inibidores Enzimáticos/uso terapêutico , Glutamatos/uso terapêutico , Hidroximetil e Formil Transferases/antagonistas & inibidores , Neoplasias/tratamento farmacológico , Pirimidinas/uso terapêutico , Adulto , Idoso , Idoso de 80 Anos ou mais , Esquema de Medicação , Feminino , Glutamatos/efeitos adversos , Glutamatos/farmacocinética , Humanos , Masculino , Pessoa de Meia-Idade , Fosforribosilglicinamido Formiltransferase , Pirimidinas/efeitos adversos , Pirimidinas/farmacocinéticaRESUMO
A field study was performed which compared predicted and measured concentrations of chemicals in receiving water organisms from three sampling locations on Five Mile Creek, Birmingham, Al. Two point source discharges, both from coke manufacturing facilities, were included in the field site and five chemicals were studied, i.e., biphenyl, phenanthrene, anthracene, fluoranthene, and pyrene. Composite samples of effluent, receiving water organisms, crayfish (Decapoda) and sunfish (Lepomis sp.), and stream and discharge flow data were collected in March and April 1990. For the crayfish and sunfish, the measured residues were within a factor of 5 for 80% (12 of 15) and 53% (8 of 15) of the residues predicted using EPA's draft procedure (US-EPA 199 lb), respectively, and were within a factor of 5 for 60% (9 of 15) and 40% (6 of 15) of the residues predicted using EPA's procedure with a BCF set equal to the chemical's Kow (after adjustment for lipid content of the organism), respectively. The predicted residues tended to be larger than the measured residues and with increasing Kow, greater disagreement between the predicted and measured values was observed.
Assuntos
Astacoidea/metabolismo , Coque , Resíduos Industriais/análise , Perciformes/metabolismo , Poluentes da Água/análise , Alabama , Animais , Antracenos/análise , Compostos de Bifenilo/análise , Fluorenos/análise , Água Doce , Fungicidas Industriais/análise , Fenantrenos/análise , Pirenos/análise , Análise de Regressão , Estados Unidos , United States Environmental Protection AgencyAssuntos
Congelamento , Leucemia L1210 , Animais , Preservação de Sangue , Ciclofosfamida/farmacologia , Citarabina/farmacologia , DNA de Neoplasias/biossíntese , Resistência a Medicamentos , Leucemia L1210/metabolismo , Camundongos , Camundongos Endogâmicos , RNA Neoplásico/biossíntese , Fatores de TempoRESUMO
Recent studies in this laboratory have been directed at investigating the cellular and subcellular metabolism of RNA in leukemic cells which have been characterized with respect to their degree and type of sensitivity/resistance to specific chemotherapeutic agents. In the present report, electrophoretic patterns on several types of SDS-polyacrylamide gels are presented using total cellular RNA preparations from a subline of L1210 mouse leukemia found to be resistant to cytosine arabinoside (L1210/Ara-C). These studies have been facilitated by using a computerized-spectrophotometric system for quantitative and qualitative comparisons of these profiles. The results suggest that patterns of RNA metabolism may be a useful biochemical test in leukemia.