This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Koh, A. J. Articles by McCauley, L. K. Search for Related Content PubMed PubMed Citation Articles by Koh, A. J. Articles by McCauley, L. K.

3',5'-Cyclic Adenosine Monophosphate Activation in Osteoblastic Cells: Effects on Parathyroid Hormone-1 Receptors and Osteoblastic Differentiation in Vitro¹

The University of Michigan, Department of Periodontics/Prevention/Geriatrics (A.J.K., C.A.B., L.K.M.), Ann Arbor, Michigan 48109; and The Ohio State University (T.J.R.), Department of Veterinary Biosciences, Columbus, Ohio 43210

Address all correspondence and requests for reprints to: Laurie K. McCauley, Department of Periodontics/Prevention/Geriatrics, University of Michigan, 1011 North University Avenue, Ann Arbor, Michigan 48109-1078. E-mail: mccauley{at}umich.edu

PTH has anabolic and catabolic effects in bone through activation of the PTH-1 (PTH/PTHrP) receptor and the cAMP/protein kinase A pathway. The effects of agents that regulate cAMP in nontransformed osteoblasts in relation to cell differentiation have not been described. The purpose of this study was to determine the effects of PTH fragments with differing cAMP-stimulating activity, and nonPTH cAMP regulators on PTH-1 receptor expression and activity, and osteoblast differentiation in vitro using MC3T3-E1 and primary rat calvarial cells. PTH (1–34), but not PTH (53–84), (7–34), or PTHrP (107–139) treatment (24 h) resulted in down-regulation of steady-state messenger RNA for the PTH-1 receptor. Forskolin (a stimulator of cAMP accumulation) also down regulated the PTH-1 receptor, whereas 9-(tetrahydro-2-furyl) adenine (THFA) (an inhibitor of adenylyl cyclase) had no effect. Similarly, PTH (1–34) treatment for 48 h abolished PTHrP binding to cell surface receptors; however, neither the PTH analogs nor the cAMP regulating agents altered PTH binding or numbers of binding sites on osteoblastic cells. Basal levels of cAMP were reduced in cultured cells treated for 6 days with PTH (7–34) or THFA compared with controls. In contrast, PTH-stimulated cAMP levels were significantly increased in cultures treated with PTH (7–34) and THFA for 6 days during osteoblast differentiation and were decreased in cultures treated with PTH (1–34) and forskolin compared with controls. To evaluate effects of the cAMP pathway on osteoblast differentiation, cultures were treated continuously with PTH analogs and cAMP regulators during an 18-day differentiation regime, total RNA was isolated at multiple time points, and Northern blot analysis for osteocalcin (OCN) was performed. THFA and PTH (7–34)-treated cultures had increased OCN expression; whereas, PTH (1–34) and forskolin reduced OCN expression. Interestingly, PTH (7–34) and THFA-treated cultures had increased mineralized nodule formation, in contrast to PTH (1–34) and forskolin treatment, which reduced nodule formation. Similarly, calcium accumulation in cultures was significantly increased in the PTH (7–34) and THFA-treated cultures and reduced in the PTH (1–34) and forskolin-treated cultures. These data demonstrate that agents that increase cAMP down regulate PTH-1 receptor messenger RNA and inhibit osteoblast differentiation in vitro. Agents that reduce or block adenylyl cyclase or cAMP activity do not alter PTH-1 receptor expression or binding, but have striking effects on promoting osteoblast differentiation. We conclude that many effects of PTH on osteoblasts may be mimicked or antagonized by agents that alter cAMP activity and bypass the PTH-1 receptor.

This article has been cited by other articles:

				D. Merciris, C. Marty, C. Collet, M.-C. de Vernejoul, and V. Geoffroy Overexpression of the Transcriptional Factor Runx2 in Osteoblasts Abolishes the Anabolic Effect of Parathyroid Hormone in Vivo Am. J. Pathol., May 1, 2007; 170(5): 1676 - 1685. [Abstract] [Full Text] [PDF]

				A. J. Koh, B. Demiralp, K. G. Neiva, J. Hooten, R. M. Nohutcu, H. Shim, N. S. Datta, R. S. Taichman, and L. K. McCauley Cells of the Osteoclast Lineage as Mediators of the Anabolic Actions of Parathyroid Hormone in Bone Endocrinology, November 1, 2005; 146(11): 4584 - 4596. [Abstract] [Full Text] [PDF]

				S. L. Ferrari, D. D. Pierroz, V. Glatt, D. S. Goddard, E. N. Bianchi, F. T. Lin, D. Manen, and M. L. Bouxsein Bone Response to Intermittent Parathyroid Hormone Is Altered in Mice Null for {beta}-Arrestin2 Endocrinology, April 1, 2005; 146(4): 1854 - 1862. [Abstract] [Full Text] [PDF]

				C. Chen, A. J. Koh, N. S. Datta, J. Zhang, E. T. Keller, G. Xiao, R. T. Franceschi, N. J. D'Silva, and L. K. McCauley Impact of the Mitogen-activated Protein Kinase Pathway on Parathyroid Hormone-related Protein Actions in Osteoblasts J. Biol. Chem., July 9, 2004; 279(28): 29121 - 29129. [Abstract] [Full Text] [PDF]

				B. Demiralp, H.-L. Chen, A. J. Koh, E. T. Keller, and L. K. McCauley Anabolic Actions of Parathyroid Hormone during Bone Growth Are Dependent on c-fos Endocrinology, October 1, 2002; 143(10): 4038 - 4047. [Abstract] [Full Text] [PDF]

				R. Gopalakrishnan, H. Ouyang, M. J. Somerman, L. K. McCauley, and R. T. Franceschi Matrix {gamma}-Carboxyglutamic Acid Protein Is a Key Regulator of PTH-Mediated Inhibition of Mineralization in MC3T3-E1 Osteoblast-Like Cells Endocrinology, October 1, 2001; 142(10): 4379 - 4388. [Abstract] [Full Text] [PDF]

				A. ValIn, C. Guillen, and P. Esbrit C-Terminal Parathyroid Hormone-Related Protein (PTHrP) (107-139) Stimulates Intracellular Ca2+ through a Receptor Different from the Type 1 PTH/PTHrP Receptor in Osteoblastic Osteosarcoma UMR 106 Cells Endocrinology, July 1, 2001; 142(7): 2752 - 2759. [Abstract] [Full Text] [PDF]

				L. K. Mccauley, A. J. Koh-Paige, H. Chen, C. Chen, C. Ontiveros, R. Irwin, and L. R. Mccabe Parathyroid Hormone Stimulates fra-2 Expression in Osteoblastic Cells in Vitro and in Vivo Endocrinology, May 1, 2001; 142(5): 1975 - 1981. [Abstract] [Full Text]

				H. Ouyang, R. T. Franceschi, L. K. McCauley, D. Wang, and M. J. Somerman Parathyroid Hormone-Related Protein Down-Regulates Bone Sialoprotein Gene Expression in Cementoblasts: Role of the Protein Kinase A Pathway Endocrinology, December 1, 2000; 141(12): 4671 - 4680. [Abstract] [Full Text] [PDF]