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Inorganic Polyphosphate in Human Osteoblast‐like Cells
Author(s) -
Leyhausen Gabriele,
Lorenz Bernd,
Zhu Hua,
Geurtsen Werner,
Bohnensack Ralf,
Müller Werner E. G.,
Schröder Heinz C.
Publication year - 1998
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.1998.13.5.803
Subject(s) - polyphosphate , osteoblast , alkaline phosphatase , ascorbic acid , endocrinology , medicine , biochemistry , chemistry , biology , enzyme , in vitro , food science , phosphate
Significant amounts of inorganic polyphosphates and of polyphosphate‐degrading exopolyphosphatase activity were detected in human mandibular‐derived osteoblast‐like cells. The amount of both soluble and insoluble long‐chain polyphosphate in unstimulated osteoblast‐like cells was higher than in human gingival cells, erythrocytes, peripheral blood mononuclear cells, and human blood plasma. The cellular content of polyphosphate in osteoblast‐like cells strongly decreased after a combined treatment of the cells with the stimulators of osteoblast proliferation and differentation, dexamethasone, β‐glycerophosphate, epidermal growth factor, and ascorbic acid. The amount of soluble long‐chain polyphosphate, but not the amount of insoluble long‐chain polyphosphate, further decreased after an additional treatment with 1α,25‐dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ). The decrease in polyphosphate content during treatment with dexamethasone, β‐glycerophosphate, epidermal growth factor, and ascorbic acid was accompanied by a decrease in exopolyphosphatase, pyrophosphatase, and alkaline phosphatase activity. However, additional treatment with 1,25(OH) 2 D 3 resulted in an increase in these enzyme activities. Osteoblast‐like cell exopolyphosphatase activity and exopolyphosphatase activity in yeast, rat tissues, and human leukemia cell line HL60 were inhibited by the bisphosphonates etidronate and, to a lesser extent, clodronate and pamidronate. From our results, we assume that inorganic polyphosphate may be involved in modulation of the mineralization process in bone tissue.