Ascorbic acid decreases neutral endopeptidase activity in cultured osteoblastic cells.
Neprilysin (NEP) is a plasma membrane-bound peptidase with wide expression in kidney, lung, brain and bone. Decreased NEP activity has been linked to increased growth of some cancer cells, but it is unknown whether its activity is related to growth of cells belonging to the osteoblast lineage. We assessed NEP activity in an osteoblastic cell line, PyMS, by cleavage of N-Dansyl-d-Ala-Gly-p-nitro-Phe-Gly to Dansyl-d-Ala-Gly. NEP activity was completely blocked by 1 muM thiorphan. Most agents affecting growth of these cells (e.g. calcium, insulin-like growth factor I and dexamethasone) did not regulate NEP activity. Ascorbic acid (ASA) increased thymidine incorporation into DNA and potentiated the stimulatory effect of IGF I on DNA synthesis, an effect which was attenuated by echistatin. ASA decreased NEP activity in a dose-dependent manner, and decreased Western-detectable NEP protein in plasma membranes. ASA affects both integrin receptor-mediated signalling and the processing of regulatory peptides.
Schmid
Christoph
C
Division of Endocrinology and Diabetes, Department of Internal Medicine, University Hospital of Zurich, 8091 Zurich, Switzerland. christoph.schmid@usz.ch
Ghirlanda-Keller
Claudia
C
Gosteli-Peter
Martina
M
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured / Q000166:cytology; D004247:DNA / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D015260:Neprilysin / Q000737:chemistry* / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D051381:Rats; D015398:Signal Transduction; D013347:Subcellular Fractions; D015244:Thiorphan / Q000494:pharmacology; D013936:Thymidine / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D015533:Transcriptional Activation
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C057986:echistatin; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone; D004247:DNA; D015244:Thiorphan; D000469:Alkaline Phosphatase; D015260:Neprilysin; D001205:Ascorbic Acid; D002118:Calcium; D013936:Thymidine