Insulin receptor substrate 2 plays important roles in 17beta-estradiol-induced bone formation.
BACKGROUND
Discovering the mechanisms of the estrogen effects on the osteoblasts is very important for the development of new agents which have the clear-cut beneficial effects of estrogen while free of adverse effect.


OBJECTIVE
The aim of this study was to investigate the differential gene expression of 17beta-estradiol (E2)-treated osteoblast-like cells, and the effect of E2 on the insulin receptor substrate 2 (IRS- 2) expression in human cultured osteoblast-like cells and the osteoblasts of ovariectomized (OVX) rats.


METHODS
The differential gene expression of E2-treated osteoblast- like cells was analyzed by cytokine expression array and validated by RT-PCR and Western blot analysis. The protein expression and phosphorylation of one of the differentially expressed gene, IRS-2, treated at different times with E2 were analyzed. The Sprague-Dawley rats were ovariectomized and then treated with E2, the IRS-2 expression was analyzed by immunohistochemistry analysis.


RESULTS
E2 upregulated the mRNA expression of IRS-2, bone morphogenetic protein 9, and connective tissue growth factor expression, down-regulated the mRNA expression of matrix metalloproteinase 15 and some tumor suppressor genes. Peak expression of IRS-2 was observed at 12-24 h of treatment by 10-8M E2. E2 can also increase the phosphorylation of IRS-2. The IRS-2 expression was down-regulated in the osteoblasts and bone marrow cells of the OVX rats, which had lower bone mineral density (BMD) than the normal rats. However, both BMD and IRS-2 expression can be rescued by 10-8M E2 in the OVX rats.


CONCLUSIONS
IRS-2 in osteoblast is up-regulated by E2 and plays important roles in the estrogen- induced bone formation.
Bu
Y-H
YH
Department of Clinical Laboratory, The Second Xiang- Ya Hospital of Central South University, Changsha, Hunan 410011, China.
Peng
D
D
Zhou
H-D
HD
Huang
Q-X
QX
Liu
W
W
Luo
X-B
XB
Tang
L-L
LL
Tang
A-G
AG
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects* / Q000502:physiology; D010012:Osteogenesis / Q000187:drug effects*; D010052:Ovariectomy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation
D016207:Cytokines; C526297:IRS2 protein, human; D055504:Insulin Receptor Substrate Proteins; C526299:Irs2 protein, rat; D012333:RNA, Messenger; D004958:Estradiol; D048031:JNK Mitogen-Activated Protein Kinases