Efectos citotóxicos del cadmio y del bisfenol-A en Chironomus riparius (Diptera)|bidentificación de biomarcadores moleculares de ecotoxicidad frente a disruptores endocrinos
Entity
UAM. Departamento de Biología MolecularDate
2009-07-16Subjects
Ecotoxicología - Tesis doctorales; Insectos acuáticos - Ecología - Tesis doctorales; Biología y Biomedicina / BiologíaNote
Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 16-07-2009Abstract
The aim of this study was to investigate the cytotoxic effects of the heavy metal
Cadmium and the organic molecule Bisphenol A, both with potential activity as
endocrine disrupting agents, in the midge Chironomus riparius (Diptera, Chironomidae),
a model organism in aquatic ecotoxicology. Analysis of the cytotoxic effects, shown by
the alterations in different cellular indicators, attempted to identify early molecular
biomarkers, which would also help to improve knowledge about the mechanisms of
toxicity of these contaminants.
The early cytotoxic effects were evaluated using immunocytochemistry with
specific fluorescent probes, in polytene chromosomes from salivary gland cells in
fourth instar larvae after treatments with 10 mM Cadmium and 3 mg/l Bisphenol A
(BPA). Under these conditions, no significant effect on larvae mortality was detected. A
decrease in the activity of intrachromosomic loci was accompanied by a significant
decondensation of centromeres and telomeres, especially remarkable after BPA
exposure. Specifically, Cadmium caused a significant reduction in size and a
modification in nucleolar architecture, as shown by FISH. These data were further
evaluated by Northern blot analysis, showing a decrease in the level of preribosomal
rRNA. These results provide the first evidence that Cadmium interacts with ribosomal
genes and results in a drastic impairment of the functional activity of the nucleolus, an
essential organelle for cellular survival.
We have analyzed the alterations in the pattern of gene expression after acute
and short‐term exposure (12‐24h) to Cadmium and Bisphenol A in a group of selected
genes, which included housekeeping (rpL11 and rpL13), stress‐induced (hsp70, hsc70,
hsp40 and hsp90) and hormone‐related genes (EcR and usp). The levels of different gene
transcripts were measured by semi‐quantitative reverse transcription polymerase chain
reaction (RT‐PCR). After exposure to both compounds, no significant differences to
controls were detected in rpL11, rpL13, hsc70, hsp40, hsp90 and usp transcripts. However,
BPA and Cadmium treatments induced the expression of the hsp70 gene, reinforcing
the idea of HSP70 as a molecular biomarker of environmental stress. Interestingly, it
was found that these substances significantly upregulate the mRNA level of the
ecdysone receptor (EcR). These results show, for the first time, that exposure to
endocrine disrupting chemicals can selectively affect the expression of the ecdysone
receptor gene, a key element in the hormone signaling pathway, suggesting a direct
interaction with the insect endocrine system. Our study adds a new element, the EcR,
which may be a useful biomarker for the screening of environmental endocrine
disrupting compounds in insects.
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Google Scholar:Planelló Carro, Mª del Rosario
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