RESUMEN
Industrial solvents pose a significant threat to the humankind. The mechanisms of their toxicity still remain in debate. Trichloroethylene (TCE) is a widespread industrial solvent responsible for severe liver dysfunction, cutaneous toxicity in occupationally exposed humans. We utilized an in vitro system of human epidermal keratinocyte (HaCaT) cells in this study to avoid complex cell and extracellular interactions. We report the cytotoxicity of organic solvent TCE in HaCaT and its reversal by a natural flavanone, naringenin (Nar). The cytotoxicity was attributed to the rapid intracellular free calcium (Ca(2+)) release, which might lead to the elevation of protein kinase C along with robust free radical generation, instability due to energy depletion, and sensitization of intracellular stress signal transducer nuclear factor κB. These effects were actually seen to induce significant amount of genomic DNA fragmentation. Furthermore, all these effects of TCE were effectively reversed by the treatment of Nar, a natural flavanone. Our studies identify intracellular Ca as a unique target used by organic solvents in the cytotoxicity and highlight the Ca(2+) ion stabilizer properties of Nar.
Asunto(s)
Calcio/metabolismo , Flavanonas/farmacología , Queratinocitos/efectos de los fármacos , Solventes/toxicidad , Tricloroetileno/toxicidad , Línea Celular , Supervivencia Celular/efectos de los fármacos , Fragmentación del ADN , Metabolismo Energético/efectos de los fármacos , Células Epidérmicas , Epidermis/efectos de los fármacos , Radicales Libres/metabolismo , Humanos , Potencial de la Membrana Mitocondrial/efectos de los fármacos , FN-kappa B/metabolismo , Proteína Quinasa C/metabolismo , Tricloroetileno/antagonistas & inhibidoresRESUMEN
BACKGROUND: Previous studies show gene expression alterations in rat embryo hearts and cell lines that correspond to the cardio-teratogenic effects of trichloroethylene (TCE) in animal models. One potential mechanism of TCE teratogenicity may be through altered regulation of calcium homeostatic genes with a corresponding inhibition of cardiac function. It has been suggested that TCE may interfere with the folic acid/methylation pathway in liver and kidney and alter gene regulation by epigenetic mechanisms. According to this hypothesis, folate supplementation in the maternal diet should counteract TCE effects on gene expression in the embryonic heart. APPROACH: To identify transcriptional targets altered in the embryonic heart after exposure to TCE, and possible protective effects of folate, we used DNA microarray technology to profile gene expression in embryonic mouse hearts with maternal TCE exposure and dietary changes in maternal folate. RESULTS: Exposure to low doses of TCE (10 ppb) caused extensive alterations in transcripts encoding proteins involved in transport, ion channel, transcription, differentiation, cytoskeleton, cell cycle, and apoptosis. Exogenous folate did not offset the effects of TCE exposure on normal gene expression, and both high and low levels of folate produced additional significant changes in gene expression. CONCLUSIONS: A mechanism by which TCE induces a folate deficiency does not explain altered gene expression patterns in the embryonic mouse heart. The data further suggest that use of folate supplementation, in the presence of this toxin, may be detrimental and not protective of the developing embryo.
Asunto(s)
Anomalías Inducidas por Medicamentos/genética , Perfilación de la Expresión Génica , Cardiopatías Congénitas/inducido químicamente , Corazón/efectos de los fármacos , Teratógenos/toxicidad , Tricloroetileno/toxicidad , Contaminantes Químicos del Agua/toxicidad , Anomalías Inducidas por Medicamentos/prevención & control , Animales , Apoptosis , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/genética , Suplementos Dietéticos/efectos adversos , Femenino , Ácido Fólico/administración & dosificación , Deficiencia de Ácido Fólico/inducido químicamente , Deficiencia de Ácido Fólico/complicaciones , Corazón/crecimiento & desarrollo , Cardiopatías Congénitas/genética , Cardiopatías Congénitas/prevención & control , Canales Iónicos/efectos de los fármacos , Canales Iónicos/genética , Transporte Iónico/efectos de los fármacos , Transporte Iónico/genética , Ratones , Organogénesis/efectos de los fármacos , Organogénesis/genética , Embarazo , Ratas , Tricloroetileno/antagonistas & inhibidores , Contaminantes Químicos del Agua/antagonistas & inhibidoresRESUMEN
The aim of the present study was to investigate the hypothesis that liver tissue repair induced by exposure to chloroform (CHCl(3))+trichloroethylene binary mixture (BM) is dose-dependent similar to that elicited by exposure to these compounds individually. Male Sprague-Dawley rats (250-300 g) received three dose combinations of binary mixture (74+250, 185+500 and 370+1250 mg CHCl(3)+trichloroethylene/kg, intraperitoneally) in corn oil (maximum of 0.5 ml/kg). Liver injury was assessed by plasma alanine amino transaminase (ALT) activity and histopathology by haematoxylin & eosin. Liver tissue repair was measured by (3)H-thymidine incorporation into hepatonuclear DNA. Blood and liver levels of both the parent compounds and two major metabolites of trichloroethylene (trichloroacetic acid and trichloroethanol) were quantified by gas chromatography. The blood and liver CHCl(3) levels after the administration of binary mixture were similar compared to the administration of CHCl(3) alone. The blood and liver trichloroethylene levels after the binary mixture were significantly lower compared to trichloroethylene alone due to higher elimination in presence of CHCl(3), resulting in decreased production of metabolites. The antagonistic toxicokinetics resulted in lower liver injury than the summation of injury caused by the individual components at all three dose levels. On the other hand, tissue repair elicited by the binary mixture was dose-dependent. The interactive toxicity of this binary mixture of CHCl(3) and trichloroethylene led to subadditive initial liver injury because of a combined effect of higher elimination of TCE and mitigated progression of liver injury was prevented by timely dose-dependent stimulation of compensatory tissue repair. Even though the doses of the toxicants employed in this study are much higher than found in the environment, the results suggest that a mixture of these two compounds at environmental levels is unlikely to cause any exaggerated interactive acute liver toxicity of any biological significance.