11β-HSD2 downregulation leads to upregulation of ADAM17 expression
Increased sFlt1 release is associated with either increased sFlt-1
transcripts or increased shedding of sFlt1 from membrane Flt1. ADAM10
and ADAM17 are the sheddases for shedding of sFlt1form Flt1
(Zhao et al., 2010). Cortisol
(10-6M) treatment significantly increased ADAM17 but
not ADAM10 protein expression in placental explants in the presence of
CBX (supplemental Fig.S9). Further, we found that cortisol
(10-6M) treatment significantly enhanced ADAM17
expression in primary syncytiotrophoblasts transfected with 11β-HSD2
siRNA
(Fig.7D). We then confirmed that sFlt1 release was mediated by ADAM17 by
showing that sFlt1 secretion was significantly decreased in
syncytiotrophoblasts with ADAM17 knockdown compared with the cells
transfected with scramble siRNA (Fig.7E).
In the classic model of steroid hormone action, upon binding a ligand
steroid receptors interact with the DNA at specific hormone response
elements to modulate gene transcription. Bioinformatic analysis shows
that there are seven putative
glucocorticoid response elements (GREs) in the upstream (2kb) ofADAM17gene.
We therefore investigated whether GCs have an impact on ADAM17gene transcriptional activity and the role of these elements in GC
regulation of ADAM17 transcription in placental cells. As shown
in Fig.7F, DEX (10-6M) significantly increased
transcriptional activity of ADAM 17 reporter. When these elements were
mutated, DEX did not affect transcriptional activity of the mutant GRE
ADAM17 reporter in primary syncytiotrophoblasts.
In the animal models, we found that systemic administration of CBX (1.2
and 2.4 mg/kg) led to a significant increase in ADAM17 expression in the
placenta compared with vehicle treatment (Fig.8A). Specific inhibition
of placental 11β-HSD2 by administration of CBX-CSA could also
significantly promote ADAM17 expression in placentas compared with
vehicle control (Fig.8B). Administration of CBX-NPs and CBX-SCR had no
effect on ADAM17 expression in placenta.
We then examined ADAM17 expression in human placental samples recruited
from a Shanghai hospital. It was shown that ADAM17 levels were
significantly increased in PE placentas compared with normal ones
(Fig.8C). In addition, we also determined 11β-HSD2 protein expression in
placenta and confirmed that placental 11β-HSD2 level was significantly
decreased in PE patients.