Abstract
Changes in regional oxygen tension that occur during skeletal development and fracture stimulate local bone cell activity to regulate bone formation, maintenance, and repair. The adaptive responses of bone cells to hypoxia are only beginning to be understood. The transcription factor hypoxia-inducible factor-1α (HIF-1α) is activated under hypoxia and promotes expression of genes required for adaptation and cell survival, and also regulates both bone development and fracture repair. We have previously demonstrated that hypoxic osteoblasts increase PGE2 release and expression of the PGE2 receptor EP1. In the present studies, we investigated the impact of altered HIF-1α activity and expression on EP1 expression in osteoblasts. HIF-1α stabilization was induced in cells cultured in 21% oxygen by treatment with dimethyloxaloglycine (DMOG) or siRNA targeted against PHD2. To implicate HIF-1α in hypoxia-induced EP1 expression, osteoblastic cells were treated with siRNA targeted against HIF-1α prior to exposure to hypoxia. EP1 expression was significantly increased in cells cultured in 21% oxygen with DMOG or PHD2 siRNA treatment compared to controls. Hypoxia responsive element (HRE) activation in hypoxia was attenuated in cells treated with HIF-1α siRNA compared to controls, indicating HIF-1α as the functional HIF-α isoform in this system. Furthermore, hypoxic cells treated with HIF-1α siRNA demonstrated reduced EP1 expression in hypoxia compared to controls. Inhibition of SAPK/JNK activity significantly reduced hypoxia-induced EP1 expression but had no impact on HIF-1α expression or activity. These data strongly implicate a role for HIF-1α in hypoxia-induced EP1 expression and may provide important insight into the mechanisms by which HIF-1α regulates bone development and fracture repair.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 233-239 |
| Number of pages | 7 |
| Journal | Journal of Cellular Biochemistry |
| Volume | 107 |
| Issue number | 2 |
| DOIs | |
| State | Published - May 15 2009 |
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Keywords
- Ep1
- HIF-1α
- Hypoxia
- JNK
- Osteoblast
- SAPK
ASJC Scopus subject areas
- Biochemistry
- Cell Biology
- Molecular Biology
Cite this
HIF-1α regulates hypoxia-induced EP1 expression in osteoblastic cells. / Genetos, Damian C; Lee, Christina M.; Wong, Alice; Yellowley-genetos, Clare E.
In: Journal of Cellular Biochemistry, Vol. 107, No. 2, 15.05.2009, p. 233-239.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - HIF-1α regulates hypoxia-induced EP1 expression in osteoblastic cells
AU - Genetos, Damian C
AU - Lee, Christina M.
AU - Wong, Alice
AU - Yellowley-genetos, Clare E
PY - 2009/5/15
Y1 - 2009/5/15
N2 - Changes in regional oxygen tension that occur during skeletal development and fracture stimulate local bone cell activity to regulate bone formation, maintenance, and repair. The adaptive responses of bone cells to hypoxia are only beginning to be understood. The transcription factor hypoxia-inducible factor-1α (HIF-1α) is activated under hypoxia and promotes expression of genes required for adaptation and cell survival, and also regulates both bone development and fracture repair. We have previously demonstrated that hypoxic osteoblasts increase PGE2 release and expression of the PGE2 receptor EP1. In the present studies, we investigated the impact of altered HIF-1α activity and expression on EP1 expression in osteoblasts. HIF-1α stabilization was induced in cells cultured in 21% oxygen by treatment with dimethyloxaloglycine (DMOG) or siRNA targeted against PHD2. To implicate HIF-1α in hypoxia-induced EP1 expression, osteoblastic cells were treated with siRNA targeted against HIF-1α prior to exposure to hypoxia. EP1 expression was significantly increased in cells cultured in 21% oxygen with DMOG or PHD2 siRNA treatment compared to controls. Hypoxia responsive element (HRE) activation in hypoxia was attenuated in cells treated with HIF-1α siRNA compared to controls, indicating HIF-1α as the functional HIF-α isoform in this system. Furthermore, hypoxic cells treated with HIF-1α siRNA demonstrated reduced EP1 expression in hypoxia compared to controls. Inhibition of SAPK/JNK activity significantly reduced hypoxia-induced EP1 expression but had no impact on HIF-1α expression or activity. These data strongly implicate a role for HIF-1α in hypoxia-induced EP1 expression and may provide important insight into the mechanisms by which HIF-1α regulates bone development and fracture repair.
AB - Changes in regional oxygen tension that occur during skeletal development and fracture stimulate local bone cell activity to regulate bone formation, maintenance, and repair. The adaptive responses of bone cells to hypoxia are only beginning to be understood. The transcription factor hypoxia-inducible factor-1α (HIF-1α) is activated under hypoxia and promotes expression of genes required for adaptation and cell survival, and also regulates both bone development and fracture repair. We have previously demonstrated that hypoxic osteoblasts increase PGE2 release and expression of the PGE2 receptor EP1. In the present studies, we investigated the impact of altered HIF-1α activity and expression on EP1 expression in osteoblasts. HIF-1α stabilization was induced in cells cultured in 21% oxygen by treatment with dimethyloxaloglycine (DMOG) or siRNA targeted against PHD2. To implicate HIF-1α in hypoxia-induced EP1 expression, osteoblastic cells were treated with siRNA targeted against HIF-1α prior to exposure to hypoxia. EP1 expression was significantly increased in cells cultured in 21% oxygen with DMOG or PHD2 siRNA treatment compared to controls. Hypoxia responsive element (HRE) activation in hypoxia was attenuated in cells treated with HIF-1α siRNA compared to controls, indicating HIF-1α as the functional HIF-α isoform in this system. Furthermore, hypoxic cells treated with HIF-1α siRNA demonstrated reduced EP1 expression in hypoxia compared to controls. Inhibition of SAPK/JNK activity significantly reduced hypoxia-induced EP1 expression but had no impact on HIF-1α expression or activity. These data strongly implicate a role for HIF-1α in hypoxia-induced EP1 expression and may provide important insight into the mechanisms by which HIF-1α regulates bone development and fracture repair.
KW - Ep1
KW - HIF-1α
KW - Hypoxia
KW - JNK
KW - Osteoblast
KW - SAPK
UR - http://www.scopus.com/inward/record.url?scp=66149088342&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=66149088342&partnerID=8YFLogxK
U2 - 10.1002/jcb.22119
DO - 10.1002/jcb.22119
M3 - Article
C2 - 19277991
AN - SCOPUS:66149088342
VL - 107
SP - 233
EP - 239
JO - Journal of Cellular Biochemistry
JF - Journal of Cellular Biochemistry
SN - 0730-2312
IS - 2
ER -