title: Adrenomedullin is anti-apoptotic in osteoblasts through CGRP1 receptors and MEK-ERK pathway.
abstract: Adrenomedullin (ADM) has been shown to mediate multifunctional responses in cell culture and animal system such as regulation of growth and apoptosis. ADM stimulates the proliferation of osteoblasts in vitro and promotes bone growth in vivo. The ability of ADM to influence osteoblastic cell number through inhibition of apoptosis has not yet been studied. To address this question we have investigated its effect on the apoptosis of serum-deprived osteoblastic cells using mouse MC3T3-E1 cells which express both ADM and ADM receptors. Treatment with ADM significantly blunted apoptosis, evaluated by caspase-3 activity, DNA fragmentation quantification and annexin V-FITC labeling. This effect was abolished by the subtype-1 CGRP receptor antagonist, CGRP(8-37). Both ADM and its specific receptor antagonist, the (22-52) ADM fragment exhibited a similar anti-apoptotic effect. Thus, our data suggest that ADM exerts anti-apoptotic effects through CGRP1 receptors. This was substantiated by a similar protective effect of CGRP on MC3T3-E1 cells apoptosis. Accordingly, neutralization of endogenous ADM by a specific antibody enhanced apoptosis. Finally, the selective inhibitor of MAPK kinase (MEK), PD98059, abolished the apoptosis protective effect of ADM and prevented ADM activation of ERK1/2. These data show that ADM acts as a survival factor in osteoblastic cells via a CGRP1 receptor-MEK-ERK pathway, which provides further understanding on the physiological function of ADM in osteoblasts.
authors.affiliation: U.606 INSERM Hôpital Lariboisière, Paris, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Uzan
authors.forename: Aude
authors.initials: A
authors.lastname: Villemin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Garel
authors.forename: Michèle
authors.initials: M
authors.lastname: Cressent
mesh_terms: D053607:Adrenomedullin / Q000494:pharmacology*; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D006801:Humans; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000378:metabolism*; D044967:Serum
chemical_list: D017304:Annexin A5; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D018015:Receptors, Calcitonin Gene-Related Peptide; D053607:Adrenomedullin; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D016650:Fluorescein-5-isothiocyanate