title: Rho-kinase negatively regulates thyroid hormone-stimulated osteocalcin synthesis in osteoblasts.
abstract: Evidence is accumulating that Rho-associated kinase (Rho-kinase) plays important roles not only in vascular smooth muscle cell contraction, but also in a variety of cellular functions, including bone metabolism. In the present study, we investigated the involvement of Rho-kinase in the osteocalcin synthesis induced by triiodothyronine (T3) in osteoblast-like MC3T3-E1 cells. T3 time-dependently induced phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a substrate of Rho-kinase. Y27632, a specific inhibitor of Rho-kinase, attenuated the MYPT-1 phosphorylation induced by T3. T3-stimulated osteocalcin release was significantly enhanced by Y27632. Fasudil, another Rho-kinase inhibitor, amplified the osteocalcin release induced by T3. T3-stimulated osteocalcin release was significantly augmented in Rho-knockdown cells with Rho A-siRNA. Y27632 and fasudil also increased the mRNA expression level of osteocalcin induced by T3. These results strongly suggest that T3 stimulates the activation of Rho-kinase in osteoblasts, which functions as a negative regulator of T3-stimulated osteocalcin synthesis.
authors.affiliation: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kondo
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Tokuda
authors.forename: Kenji
authors.initials: K
authors.lastname: Kato
authors.forename: Rie
authors.initials: R
authors.lastname: Matsushima-Nishiwaki
authors.forename: Gen
authors.initials: G
authors.lastname: Kuroyanagi
authors.forename: Jun
authors.initials: J
authors.lastname: Mizutani
authors.forename: Osamu
authors.initials: O
authors.lastname: Kozawa
authors.forename: Takanobu
authors.initials: T
authors.lastname: Otsuka
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism*; D015675:Osteocalcin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*; D054460:rho-Associated Kinases / Q000378:metabolism*
chemical_list: D000577:Amides; D011725:Pyridines; D012333:RNA, Messenger; D014284:Triiodothyronine; D015675:Osteocalcin; C108830:Y 27632; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase; D043263:Myosin-Light-Chain Phosphatase; C510645:Ppp1r12a protein, mouse; C049347:fasudil