2,3,7,8-Tetrachlorodibenzo-p-dioxin (
TCDD) is a widespread environmental contaminant for reproductive toxicity that was suggested to be linked to
growth factors.
Insulin-like growth factor 2 (Igf2) has great effects on the control of fetal growth. We hypothesize it might participate in the
TCDD-induced toxic events. The expression of Igf2 in
TCDD-induced fetal rat and rat
hepatoma BRL-3A cells was monitored by real-time quantitative RT-PCR and Western blotting. Electrophoresis mobility shift assay and
chromatin immunoprecipitation were performed to identify the
CCAAT/enhancer binding protein β (C/EBPβ) responsive
element in the Igf2 P3-promoter. The transcriptional activity of the Igf2 P3-promoter was detected by
luciferase assay. Pregnant rats exposed to
TCDD showed a modest incidence of
fetal death,
fetal growth restriction and
fetal malformation. The levels of Igf2
mRNA and IGF2
protein were elevated in
TCDD-exposed fetal liver. Temporal expression of Igf2 was also induced by
TCDD in BRL-3A cells. A C/EBPβ responsive
element was identified at position -743 to -732 of the Igf2 P3-promoter, and its binding was enhanced by
TCDD exposure through upregulation of the C/EBPβ
protein. The transcriptional activity of the Igf2 P3-promoter was also augmented by
TCDD. Our results showed that
TCDD may induce Igf2 gene expression through the transactivation of C/EBPβ, which may be linked to the developmental effects of
TCDD in rats.