Ghrelin stimulates proliferation and differentiation and inhibits apoptosis in osteoblastic MC3T3-E1 cells.
Ghrelin is a 28-amino-acid peptide identified in the stomach as an endogenous ligand of the growth hormone secretagogue receptor (GHS-R) that strongly stimulates the release of growth hormone at the hypothalamus and pituitary level. Although GHS-Rs are expressed in a variety of peripheral tissues, little is known about its effect on bone independent of GH/IGF-1 axis. This study was undertaken to investigate whether ghrelin exerts a direct effect on osteoblasts. We identified mRNA and protein expression of GHS-R in primary osteoblasts as well as a number of osteoblastic cell lines, including MC3T3-E1, ROS 17/2.8, UMR-106, MG63, and SaOS2 cells. Treatment of ghrelin (10(-11) to 10(-7) M) to MC3T3-E1 cells showed dose-dependent stimulation of proliferation, which was abrogated by treatment with [d-Lys]-GHRP-6 (10(-3) M), a selective antagonist of the ghrelin receptor. Ghrelin activated ERK1/2 MAPK and pretreatment with MAPK kinase inhibitors, PD98059 attenuated the ghrelin-induced cell proliferation. Ghrelin also inhibited TNFalpha-induced apoptosis and suppressed caspase-3 activation that occurs in response to TNFalpha as well as during in vitro differentiation process. Moreover, ghrelin treatment enhanced in vitro osteoblast differentiation as evidenced by matrix mineralization, alkaline phosphatase activity, and osteoblast-specific gene expression. These results suggest that ghrelin promotes proliferation and differentiation and inhibits apoptosis of osteoblasts.
Kim
Sang Wan
SW
Department of Internal Medicine, Seoul National University College of Medicine, 28 Yungun-Dong, Chongno-Gu, Seoul 110-744, South Korea.
Her
Sun Ju
SJ
Park
Seong Jae
SJ
Kim
Dohee
D
Park
Kyong Soo
KS
Lee
Hong Kyu
HK
Han
Byung Hee
BH
Kim
Min Seon
MS
Shin
Chan Soo
CS
Kim
Seong Yeon
SY
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000235:genetics; D054439:Ghrelin; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects*; D036361:Peptide Hormones / Q000494:pharmacology*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D054440:Receptors, Ghrelin; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D054439:Ghrelin; D036361:Peptide Hormones; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases