Calcitonin gene-related peptide (CGRP) inhibits apoptosis in human osteoblasts by β-catenin stabilization.
Transgenic mice over-expressing calcitonin gene-related peptide (CGRP) in osteoblasts have increased bone density due to increased bone formation, thus suggesting that CGRP plays a role in bone metabolism. In this study we determined the relationship between CGRP, the canonical Wnt signaling and apoptosis in human osteoblasts (hOBs) in consideration of the well-documented involvement of this pathway in bone cells. Primary cultures of hOBs were treated with CGRP 10(-8) M. Levels of β-catenin, which is the cytoplasmic protein mediator of canonical Wnt signaling, and mRNA were determined. CGRP increases both the expression and the levels of cytoplasmic β-catenin by binding to its receptor, as this effect is blocked by the antagonist CGRP(8-37). This facilitatory action on β-catenin appears to be mediated by the inhibition of the enzyme GSK-3β via protein kinase A (PKA) activation. GSK-3β is a glycogen synthase kinase that, by phosphorylating β-catenin, promotes its degradation by the proteosomal machinery. Moreover, the peptide is able to inhibit hOBs apoptosis stimulated by dexamethasone or by serum deprivation, possibly through the accumulation of β-catenin, since the inhibitor of PKA activity H89 partially prevents the antiapoptotic effect of the peptide. In conclusion CGRP, released by nerve fibers, exerts its anabolic action on bone cells by stimulating canonical Wnt signaling and by inhibiting hOBs apoptosis, thus favoring local bone regeneration.
Bone Metabolism Unit, Division of Metabolic and Cardiovascular Disease, San Raffaele Scientific Institute, Milan, Italy.
Emanuela
E
Mrak
Francesca
F
Guidobono
Gianluigi
G
Moro
Gianfranco
G
Fraschini
Alessandro
A
Rubinacci
Isabella
I
Villa
D021581:Active Transport, Cell Nucleus; D000368:Aged; D017209:Apoptosis / Q000187:drug effects; D001861:Bone Regeneration / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D020536:Enzyme Activators / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D008875:Middle Aged; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010446:Peptide Fragments / Q000378:metabolism*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D055550:Protein Stability; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
C495270:CTNNB1 protein, human; D020536:Enzyme Activators; D007546:Isoquinolines; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D013449:Sulfonamides; D051153:Wnt Proteins; D051176:beta Catenin; C058636:calcitonin gene-related peptide (8-37); D005576:Colforsin; D003907:Dexamethasone; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D015740:Calcitonin Gene-Related Peptide; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide