RESUMEN
The molecular initiating event (MIE) of skin sensitization is the binding of a hapten to dermal proteins. This can be assessed using the in chemico direct peptide reactivity assay (DPRA) or in silico tools such as the QSAR Toolbox and TIMES SS. In this study, the suitability of these methods was analyzed by comparing their results to in vivo sensitization data of LLNA and human studies. Compared to human data, 84% of non-sensitizers and sensitizers yielded consistent results in the DPRA. In silico tools resulted in 'no alert' for 83%-100% of the non-sensitizers, but alerted only 55%-61% of the sensitizers. The inclusion of biotic and abiotic transformation simulations yielded more alerts for sensitizers, but simultaneously dropped the number of non-alerted non-sensitizers. In contrast to the DPRA, in silico tools were more consistent with results of the LLNA than human data. Interestingly, the new "DPRA profilers" (QSAR Toolbox) provided unsatisfactory results. Additionally, the results were combined in the '2 out of 3' prediction model with in vitro data derived from LuSens and h-CLAT. Using DPRA results, the model identified 90% of human sensitizers and non-sensitizers; using in silico results (including abiotic and biotic activations) instead of DPRA results led to a comparable high predictivity.
Asunto(s)
Dermatitis Alérgica por Contacto/metabolismo , Haptenos/toxicidad , Modelos Teóricos , Péptidos/metabolismo , Animales , Butanonas/toxicidad , Chalconas/toxicidad , Simulación por Computador , Ciclohexanonas/toxicidad , Furanos/toxicidad , Humanos , Ensayo del Nódulo Linfático Local , Ratones , Unión Proteica , Piruvatos/toxicidad , Relación Estructura-Actividad CuantitativaRESUMEN
In the present study we show that repeated exposure of the rat intestinal epithelial cell line IEC-18 to 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP), from a toxicological point of view the most relevant phase-1 metabolite of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP, the main heterocyclic aromatic amine present in processed meat), led to the selection of N-OH-PhIP-resistant IEC-18 cells. This phenomenon was accompanied by a fivefold increase in total glutathione S-transferase (GST) activity, measured with the broad-spectrum substrate 1-chloro-2,4-dinitrobenzene, in the N-OH-PhIP-resistant IEC-18 cells. Furthermore, a Western blotting analysis revealed that the expression of GST subunits A1, A3, A4, M1 and P1 was enhanced in the N-OH-PhIP-resistant IEC-18 cells.
Asunto(s)
Glutatión Transferasa/metabolismo , Imidazoles/toxicidad , Mutágenos/toxicidad , Piridinas/toxicidad , Animales , Secuencia de Bases , Línea Celular , Resistencia a Medicamentos , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Expresión Génica , Glutatión Transferasa/química , Glutatión Transferasa/genética , Íleon/efectos de los fármacos , Íleon/metabolismo , Imidazoles/metabolismo , Carne/análisis , Carne/toxicidad , Mutágenos/metabolismo , Piridinas/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , RatasAsunto(s)
Colon/enzimología , Neoplasias del Colon/enzimología , Sistema Enzimático del Citocromo P-450/metabolismo , Biomarcadores de Tumor/análisis , Biomarcadores de Tumor/metabolismo , Sistema Enzimático del Citocromo P-450/análisis , Sistema Enzimático del Citocromo P-450/genética , Regulación Enzimológica de la Expresión Génica , Humanos , Inmunohistoquímica , Xenobióticos/metabolismoRESUMEN
Cytosolic sulphotransferases transfer the sulpho moiety from the cofactor 5'-phosphoadenosine-3'-phosphosulphate (PAPS) to nucleophilic groups of xenobiotics and small endogenous compounds (such as hormones and neurotransmitters). This reaction often leads to products that can be excreted readily. However, other sulpho conjugates are strong electrophiles and may covalently bind with DNA and proteins. All known cytosolic sulphotransferases are members of an enzyme/gene superfamily termed SULT. In humans, 10 SULT genes are known. One of these genes encodes two different enzyme forms due to the use of alternative first exons. Different SULT forms substantially differ in their substrate specificity and tissue distribution. Genetic polymorphisms have been described for three human SULTs. Several allelic variants differ in functional properties, including the activation of promutagens. Only initial results are available from the analysis of SULT allele frequencies in different population groups, e.g. subjects suffering from specific diseases and corresponding controls.
Asunto(s)
Arilsulfotransferasa , Citosol/enzimología , Genética de Población , Sulfotransferasas/genética , Sulfotransferasas/metabolismo , Xenobióticos , Humanos , Inactivación Metabólica , Especificidad por Sustrato , Terminología como Asunto , Xenobióticos/metabolismoRESUMEN
The mammalian xenobiotic-metabolizing sulfotransferases are cytosolic enzymes, which form a gene superfamily (SULT). Ten distinct human SULT forms are known. Two SULT forms represent splice variants, the other forms are encoded by separate genes. Common functional polymorphisms of the transcribed region are known for two of the forms. We have expressed 16 separate rat and human SULTs as well as some of their allelic variants, in Salmonella typhimurium TA1538 and/or V79 cells, which are target cells of commonly used mutagenicity assays. The expressed SULTs activated numerous compounds to mutagens in both assay systems. However, some promutagens were activated by only one or several of the human SULTs. Pronounced differences in promutagen activation were also detected between orthologous rat and human SULTs, and between allelic variants of human SULTs.
