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Abstract
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Fipronil (FPN) as an insecticide can
excessively enter aquatic ecosystems and may act
as endocrine-disrupting chemicals by binding to
estrogen receptor (ER) or aryl hydrocarbon receptor
(AhR). Currently, there is limited information on the
xenoestrogen role of FPN in the transcriptional modulation
of hepatic genes involved in cell apoptosis.
Three experiments were used in this study to determine
how the FPN interference between the ER, AhR,
and intermediate chaperons can induce apoptosis
and change the expression of erα, erβ, erβ2, hsp70,
hsp90, p53, bad1, bcl2, ahr, cyp1a, and caspase9
genes in common carp (Cyprinus carpio) hepatocytes.
The IC50
values of FPN and 17β estradiol (E2)
(positive control) in fish hepatocytes were determined
(5 μg/mL). In the first experiment, exposure
(6, 24, and 48 h) of hepatocytes to the low (0.1 μg/
mL) and high (1 μg/mL) doses of FPN up-regulated
apoptosis, pro-apoptotic genes (caspase9 and bad1),
and chaperone protein genes (hsp70 and hsp90),
while down-regulated anti-apoptotic genes (p53andbcl2). Additionally, there was a significant increase in
the expression of the genes erα, ahr, and cyp1a that
was dependent on both time and dose. ERα antagonist
and a high dose of FPN were administered to the
hepatocytes in the second experiment, which reduced
cell apoptosis. In the third experiment, anti-apoptotic
gene expression increased, and cell apoptosis and ahr
and cyp1a gene expression significantly decreased
when HSP90 and ERα antagonists were applied in
comparison to the control group (P < 0.05). Based on
this study, we demonstrate that FPN-induced apoptosis
in fish hepatocytes is mediated by erα and hsp90
through transcriptional regulation of pro-apoptotic
and anti-apoptotic genes.
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