RESUMEN
The issue of adverse health effects of extremely low-frequency electromagnetic fields (ELF-EMFs) is highly controversial. Contradictory results regarding the genotoxic potential of ELF-EMF have been reported in the literature. To test whether this controversy might reflect differences between the cellular targets examined we exposed cultured cells derived from different tissues to an intermittent ELF-EMF (50 Hz sinusoidal, 1 mT) for 1-24h. The alkaline and neutral comet assays were used to assess ELF-EMF-induced DNA strand breaks. We could identify three responder (human fibroblasts, human melanocytes, rat granulosa cells) and three non-responder cell types (human lymphocytes, human monocytes, human skeletal muscle cells), which points to the significance of the cell system used when investigating genotoxic effects of ELF-EMF.
Asunto(s)
Daño del ADN , Campos Electromagnéticos/efectos adversos , Fibroblastos/efectos de la radiación , Células de la Granulosa/efectos de la radiación , Melanocitos/efectos de la radiación , Animales , Línea Celular Transformada , Ensayo Cometa , Relación Dosis-Respuesta en la Radiación , Femenino , Humanos , Linfocitos/efectos de la radiación , Masculino , Monocitos/efectos de la radiación , Fibras Musculares Esqueléticas/efectos de la radiación , Ratas , Factores de TiempoRESUMEN
Cultured human diploid fibroblasts and cultured rat granulosa cells were exposed to intermittent and continuous radiofrequency electromagnetic fields (RF-EMF) used in mobile phones, with different specific absorption rates (SAR) and different mobile-phone modulations. DNA strand breaks were determined by means of the alkaline and neutral comet assay. RF-EMF exposure (1800 MHz; SAR 1.2 or 2 W/kg; different modulations; during 4, 16 and 24h; intermittent 5 min on/10 min off or continuous wave) induced DNA single- and double-strand breaks. Effects occurred after 16 h exposure in both cell types and after different mobile-phone modulations. The intermittent exposure showed a stronger effect in the comet assay than continuous exposure. Therefore we conclude that the induced DNA damage cannot be based on thermal effects.
Asunto(s)
Teléfono Celular , Daño del ADN , Fibroblastos/efectos de la radiación , Células de la Granulosa/efectos de la radiación , Microondas/efectos adversos , Animales , Línea Celular Transformada , Ensayo Cometa , Relación Dosis-Respuesta en la Radiación , Femenino , Humanos , Masculino , Ratas , Factores de TiempoRESUMEN
The recently described increase in DNA strand breaks of cultured human diploid fibroblasts after intermittent exposure to extremely-low-frequency electromagnetic fields (ELF-EMF) of more than about 70 microT ELF-EMF is difficult to explain by a direct induction of covalent bond disruption. Therefore the hypothesis has been tested that ELF-EMF-induced DNA strand breaks might be mediated by cellular processes that cause alteration of the intracellular concentration of free calcium ([Ca2+]i) and/or the membrane potential (DeltaPsi(m)). [Ca2+]i was determined by the ratiometric fura-2 technique. Changes in DeltaPsi(m) were assessed by using the potential-dependent lipophilic cationic probe JC-1. Human fibroblasts were exposed to intermittent ELF-EMF (50 Hz, 1000 microT). Although exposure of fiboblasts to ELF-EMF resulted in a highly significant increase in DNA strand breaks as determined by the comet assay, no effect on JC-1 fluorescence emission or on [Ca2+]i has been observed when comparing exposed with sham-exposed cells. Therefore, it is suggested that ELF-EMF-induced DNA strand breaks are unlikely to be caused by intracellular changes that affect [Ca2+]i and/or DeltaPsi(m).
Asunto(s)
Calcio/metabolismo , Citoplasma/metabolismo , Campos Electromagnéticos , Fibroblastos/fisiología , Fibroblastos/efectos de la radiación , Potenciales de la Membrana/efectos de la radiación , Mitocondrias/efectos de la radiación , Diploidia , Relación Dosis-Respuesta en la Radiación , Electricidad , Humanos , Potenciales de la Membrana/fisiología , Mitocondrias/fisiología , Dosis de RadiaciónRESUMEN
Several studies indicating a decline of DNA repair efficiency with age raise the question, if senescence per se leads to a higher susceptibility to DNA damage upon environmental exposures. Cultured fibroblasts of six healthy donors of different age exposed to intermittent ELF-EMF (50 Hz sinus, 1 mT) for 1-24 h exhibited different basal DNA strand break levels correlating with age. The cells revealed a maximum response at 15-19 h of exposure. This response was clearly more pronounced in cells from older donors, which could point to an age-related decrease of DNA repair efficiency of ELF-EMF induced DNA strand breaks.
Asunto(s)
Envejecimiento/fisiología , Daño del ADN/fisiología , Campos Electromagnéticos/efectos adversos , Fibroblastos/fisiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Células Cultivadas , Niño , Reparación del ADN/fisiología , Femenino , Fibroblastos/efectos de la radiación , Humanos , Masculino , Persona de Mediana EdadRESUMEN
OBJECTIVES: Epidemiological studies have reported an association between exposure to extremely low frequency electromagnetic fields (ELF-EMFs) and increased risk of cancerous diseases, albeit without dose-effect relationships. The validity of such findings can be corroborated only by demonstration of dose-dependent DNA-damaging effects of ELF-EMFs in cells of human origin in vitro. METHODS: Cultured human diploid fibroblasts were exposed to intermittent ELF electromagnetic fields. DNA damage was determined by alkaline and neutral comet assay. RESULTS: ELF-EMF exposure (50 Hz, sinusoidal, 1-24 h, 20-1,000 mu T, 5 min on/10 min off) induced dose-dependent and time-dependent DNA single-strand and double-strand breaks. Effects occurred at a magnetic flux density as low as 35 mu T, being well below proposed International Commission of Non-Ionising Radiation Protection (ICNIRP) guidelines. After termination of exposure the induced comet tail factors returned to normal within 9 h. CONCLUSION: The induced DNA damage is not based on thermal effects and arouses concern about environmental threshold limit values for ELF exposure.
Asunto(s)
Daño del ADN , Campos Electromagnéticos/efectos adversos , Adulto , Células Cultivadas , Niño , Ensayo Cometa , Diploidia , Relación Dosis-Respuesta en la Radiación , Femenino , Fibroblastos/metabolismo , Fibroblastos/efectos de la radiación , Humanos , Técnicas In Vitro , MasculinoRESUMEN
Results of epidemiological research show low association of electromagnetic field (EMF) with increased risk of cancerous diseases and missing dose-effect relations. An important component in assessing potential cancer risk is knowledge concerning any genotoxic effects of extremely-low-frequency-EMF (ELF-EMF). Human diploid fibroblasts were exposed to continuous or intermittent ELF-EMF (50Hz, sinusoidal, 24h, 1000microT). For evaluation of genotoxic effects in form of DNA single- (SSB) and double-strand breaks (DSB), the alkaline and the neutral comet assay were used. In contrast to continuous ELF-EMF exposure, the application of intermittent fields reproducibly resulted in a significant increase of DNA strand break levels, mainly DSBs, as compared to non-exposed controls. The conditions of intermittence showed an impact on the induction of DNA strand breaks, producing the highest levels at 5min field-on/10min field-off. We also found individual differences in response to ELF-EMF as well as an evident exposure-response relationship between magnetic flux density and DNA migration in the comet assay. Our data strongly indicate a genotoxic potential of intermittent EMF. This points to the need of further studies in vivo and consideration about environmental threshold values for ELF exposure.
Asunto(s)
Daño del ADN/efectos de la radiación , ADN de Cadena Simple/efectos de la radiación , ADN/efectos de la radiación , Campos Electromagnéticos/efectos adversos , Fibroblastos/efectos de la radiación , Adulto , Células Cultivadas , Niño , Ensayo Cometa , Diploidia , Femenino , Fibroblastos/metabolismo , Humanos , MasculinoRESUMEN
To study possible genotoxic effects of occupational exposure to vanadium pentoxide, we determined DNA strand breaks (with alkaline comet assay), 8-hydroxy-2'deoxyguanosine (8-OHdG) and the frequency of sister chromatid exchange (SCE) in whole blood leukocytes or lymphocytes of 49 male workers employed in a vanadium factory in comparison to 12 non-exposed controls. In addition, vanadate has been tested in vitro to induce DNA strand breaks in whole blood cells, isolated lymphocytes and cultured human fibroblasts of healthy donors at concentrations comparable to the observed levels of vanadium in vivo. To investigate the impact of vanadate on the repair of damaged DNA, co-exposure to UV or bleomycin was used in fibroblasts, and DNA migration in the alkaline and neutral comet assay was determined. Although, exposed workers showed a significant vanadium uptake (serum: median 5.38microg/l, range 2.18-46.35microg/l) no increase in cytogenetic effects or oxidative DNA damage in leukocytes could be demonstrated. This was consistent with the observation that in vitro exposure of whole blood leukocytes and lymphocytes to vanadate caused no significant changes in DNA strand breaks below concentrations of 1microM (50microg/l). In contrast, vanadate clearly induced DNA fragmentation in cultured fibroblasts at relevant concentrations. Combined exposure of fibroblasts to vanadate/UV or vanadate/bleomycin resulted in non-repairable DNA double strand breaks (DSBs) as seen in the neutral comet assay. We conclude that exposure of human fibroblasts to vanadate effectively causes DNA strand breaks, and co-exposure of cells to other genotoxic agents may result in persistent DNA damage.
Asunto(s)
Daño del ADN/efectos de los fármacos , Fragmentación del ADN/efectos de los fármacos , ADN/efectos de los fármacos , Desoxiguanosina/análogos & derivados , Fibroblastos/efectos de los fármacos , Intercambio de Cromátides Hermanas/efectos de los fármacos , Compuestos de Vanadio/toxicidad , 8-Hidroxi-2'-Desoxicoguanosina , Adulto , Antibióticos Antineoplásicos/farmacología , Bleomicina/farmacología , Estudios de Casos y Controles , Células Cultivadas , Cromatografía Líquida de Alta Presión , Ensayo Cometa , Desoxiguanosina/metabolismo , Relación Dosis-Respuesta a Droga , Femenino , Fibroblastos/efectos de la radiación , Humanos , Linfocitos/efectos de los fármacos , Linfocitos/efectos de la radiación , Masculino , Persona de Mediana Edad , Exposición Profesional , Rayos Ultravioleta/efectos adversosRESUMEN
In order to determine background levels of DNA strand breaks, we examined 80 healthy individuals by comet assay considering age, sex, and smoking as confounding factors. Only age was found to have a significant effect on basal levels. One thousand cells of each donor were graded by eye into 5 categories according to the amount of DNA in the tail: classification group A (no damage) <5%, B (low damage) 5-20%, C (medium damage) 20-40%, D (high damage) 40-95%, and group E (total damage) >95%. The interpretation of the comet assay was modified to achieve a tail factor, which represents the DNA damage of 1000 scored cells as a single number, without the need of an image analysis software package. Hydrogen peroxide and bleomycin used for in vitro exposure of lymphocytes, produced clear dose-related responses in the comet assay. Our data encourage the application of the used classification model for a sensitive and fast quantification of DNA damage. Results in this study are in agreement with most of the earlier investigations.
Asunto(s)
Daño del ADN , Leucocitos/química , Adulto , Envejecimiento/patología , Algoritmos , Bleomicina/farmacología , Colorantes , Ensayo Cometa , Interpretación Estadística de Datos , Electroforesis en Gel de Poliacrilamida , Femenino , Humanos , Peróxido de Hidrógeno/farmacología , Leucocitos/patología , Masculino , Oxidantes/farmacología , Valores de Referencia , Caracteres Sexuales , Fumar/patologíaRESUMEN
In order to test the effects of cobalt on oxidative DNA damage, we measured the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the presence of cobalt in calf thymus DNA and in DNA of human diploid fibroblasts. Treatment of calf thymus DNA with Co(II) at 500 microM hydrogen peroxide resulted in a dose-dependent increase in 8-OHdG, which culminated at 25 microM Co(II) (62.6 modified/10(5) dG) and declined at higher Co(II) concentrations [9.6 modified/10(5) dG at 250 microM Co(II)]. Incubation of calf thymus DNA with Co(II) alone did not cause an increase in 8-OHdG. Treatment of calf thymus DNA with H2O2, (0.25-2 mM) caused only a slight generation of 8-OHdG (2.7/10(5) dG, at 2 mM H2O2). Exposure of human diploid fibroblasts to Co(II) at 5-250 microM did not result in an increase in 8-OHdG in a dose-dependent manner, although treated cells showed significantly higher 8-OHdG levels than untreated controls (2.026 +/- 0.695 vs. 1.395 +/- 0.433 8-OHdG/10(5) dG) at all concentrations. Our data indicate that in the presence of H2O2, Co(II) stimulates the in vitro formation of 8-OHdG.