Abstract
A high concentration of extracellular calcium (8 mM) induced an increase in free cytoplasmic calcium, a lower cyclic AMP level and increased DNA synthesis in primary cultures of human osteoblast-like cells. Inhibition of protein kinase C with bisindolylmaleimide I inhibited the stimulatory effect of extracellular calcium on DNA synthesis in human osteoblast-like cells, whereas inhibition of protein kinase A with Rp-cAMPs had no effect on DNA synthesis. This indicates that protein kinase C, possibly via increased free cytoplasmic calcium, mediates the effect of extracellular calcium on DNA synthesis in osteoblast-like cells rather than a relative decrease in cyclic AMP and protein kinase A activity. Furthermore, a low concentration (0.5 mM) of extracellular calcium decreased DNA synthesis. In conclusion, these data suggest that a high extracellular calcium level may be a coupling factor that recruits osteoblasts in the bone remodeling process, and that a low level of extracellular calcium may also regulate osteoblast function.
Key words
Cyclic AMP · Protein kinase C · Protein kinase A · Magnesium · Gadolinium
References
-
1
Sugimoto T, Kanatani M, Kano J, Kobayashi T, Yamaguchi T, Fukase M, Chihara K.
IGF-I mediates the stimulatory effect of high calcium concentration on osteoblastic cell proliferation.
Am J Physiol.
1994;
266
E709-716
-
2
Honda Y, Fitzsimmons R J, Baylink D J, Mohan S.
Effects of extracellular calcium on insulin-like growth factor II in human bone cells.
J Bone Miner Res.
1995;
10
660-1665
-
3
Eklou-Kalonji E, Denis I, Lieberherr M, Pointillart A.
Effects of extracellular calcium on the proliferation and differentiation of porcine osteoblasts in vitro.
Cell Tissue Res.
1998;
292
63-171
-
4
Quarles L D, Hartle J E 2nd, Siddhanti S R, Guo R, Hinson T K.
A distinct cation-sensing mechanism in MC3T3-E1 osteoblasts functionally related to the calcium receptor.
J Bone Miner Res.
1997;
12
393-402
-
5
Yamaguchi T, Chattopadhyay N, Kifor O, Butters R R Jr, Sugimoto T, Brown E M.
Mouse osteoblastic cell line (MC3T3-E1) expresses extracellular calcium ([Ca2+]o)-sensing receptor and its agonists stimulate chemotaxis and proliferation of MC3T3-E1 cells.
J Bone Miner Res.
1998;
13
1530-1538
-
6
Brown E M, Gamba G, Riccardi D, Lombardi M, Butters R, Kifor O, Sun A, Hediger M A, Lytton J, Hebert S C.
Cloning and characterization of an extracellular Ca2+-sensing receptor from bovine parathyroid.
Nature.
1993;
366
575-580
-
7
Pi M, Garner S C, Flannery P, Spurney R F, Quarles L D.
Sensing of extracellular cations in CasR-deficient osteoblasts.
J Biol Chem.
2000;
275
3256-3263
-
8
Nemeth E F, Scarpa A.
Rapid mobilization of cellular Ca2+ in bovine parathyroid cells evoked by extracellular divalent cations. Evidence for a cell surface calcium receptor.
J Biol Chem.
1987;
262
5188-5196
-
9
Brown E M, Fuleihan Gel-H, Chen C J, Kifor O.
A comparison of the effects of divalent and trivalent cations on parathyroid hormone release, 3’,5’-cyclic-adenosine monophosphate accumulation, and the levels of inositol phosphates in bovine parathyroid cells.
Endocrinology.
1990;
127
1064-1071
-
10
Peck W A, Kohler G, Barr S.
Calcium-mediated enhancement of the cyclic AMP response in cultured bone cells.
Calcif Tissue Int.
1981;
33
409-416
-
11
Hartle J E, Prpic V, Siddhanti S R, Spurney R F, Quarles L D.
Differential regulation of receptor-stimulated cyclic adenosine monophosphate production by polyvalent cations in MC3T3-E1 osteoblasts.
J Bone Miner Res.
1996;
11
789-799
-
12
Kamioka H, Sumitani K, Tagami K, Miki Y, Terai K, Hakeda Y, Kumegawa M, Kawata T.
Divalent cations elevate cytosolic calcium of chick osteocytes.
Biochem Biophys Res Commun.
1994;
204
519-524
-
13
Habel B, Glaser R.
Human osteoblast-like cells respond not only to changes to the extracellular calcium but also to its changing rate.
Eur Biophys J.
1998;
27
411-416
-
14
Tsai J A, Bucht E, Stark A, Sjostedt U, Torring O.
Parathyroid hormone-related protein (1 - 37) induces cAMP response in human osteoblast-like cells.
Calcif Tissue Int.
1998;
62
250-254
-
15
Tsai J A, Larsson O, Kindmark H.
Spontaneous and stimulated transients in cytoplasmic free Ca2+ in normal human osteoblast-like cells: Aspects of their regulation.
Biochem Biophys Res Commun.
1999;
263
206-212
-
16
Asaoka Y, Nakamura S, Yoshida K, Nishizuka Y.
Protein kinase C, calcium and phospholipid degradation.
Trends Biochem Sci.
1992;
17
414-417
-
17
Valin A, de Miguel F, Garcia-Ocana A, Esbrit P.
Parathyroid hormone-related protein (107 - 139) decreases alkaline phosphatase in osteoblastic osteosarcoma cells UMR 106 by a protein kinase C-dependent pathway.
Calcif Tissue Int.
1999;
65
148-151
-
18
Krebs E G.
The Albert Lasker Medical Awards. Role of the cyclic AMP-dependent protein kinase in signal transduction.
JAMA.
1989;
262
1815-1818
-
19
Kano J, Sugimoto T, Fukase M, Fujita T.
The activation of cAMP-dependent protein kinase is directly linked to the regulation of osteoblast proliferation (UMR-106) by parathyroid hormone.
Biochem Biophys Res Commun.
1991;
177
365-369
-
20
Thastrup O, Cullen P J, Drobak B K, Hanley M R, Dawson A P.
Thapsigargin, a tumor promoter, discharges intracellular Ca2+ stores by specific inhibition of the endoplasmic reticulum Ca2+-ATPase.
Proc Natl Acad Sci.
1990;
87
2466-2470
-
21
Silver I A, Murrills R J, Etherington D J.
Microelectrode studies on the acid microenvironment beneath adherent macrophages and osteoclasts.
Exp Cell Res.
1988;
175
266-276
E. Bucht,Ph. D.
Department of Molecular Medicine, Endocrine and Diabetes Unit ·
Karolinska Hospital · 171 76 Stockholm · Sweden
Phone: + 46 (8) 51 77 23 94
Fax: + 46 (8) 51 77 67 92 ·
Email: elisabet.bucht@molmed.ki.se