Inhibition of Ca²⁺/calmodulin-dependent protein kinase kinase 2 stimulates osteoblast formation and inhibits osteoclast differentiation. 2013

Rachel L Cary, and Seid Waddell, and Luigi Racioppi, and Fanxin Long, and Deborah V Novack, and Michael J Voor, and Uma Sankar
James Graham Brown Cancer Center and Owensboro Cancer Research Program, University of Louisville, Louisville, KY, USA.

Bone remodeling, a physiological process characterized by bone formation by osteoblasts (OBs) and resorption of preexisting bone matrix by osteoclasts (OCs), is vital for the maintenance of healthy bone tissue in adult humans. Imbalances in this vital process result in pathological conditions including osteoporosis. Owing to its initial asymptomatic nature, osteoporosis is often detected only after the patient has sustained significant bone loss or a fracture. Hence, anabolic therapeutics that stimulate bone accrual is in high clinical demand. Here we identify Ca²⁺/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) as a potential target for such therapeutics because its inhibition enhances OB differentiation and bone growth and suppresses OC differentiation. Mice null for CaMKK2 possess higher trabecular bone mass in their long bones, along with significantly more OBs and fewer multinuclear OCs. In vitro, although Camkk2⁻/⁻ mesenchymal stem cells (MSCs) yield significantly higher numbers of OBs, bone marrow cells from Camkk2⁻/⁻ mice produce fewer multinuclear OCs. Acute inhibition of CaMKK2 by its selective, cell-permeable pharmacological inhibitor STO-609 also results in increased OB and diminished OC formation. Further, we find phospho-protein kinase A (PKA) and Ser¹³³ phosphorylated form of cyclic adenosine monophosphate (cAMP) response element binding protein (pCREB) to be markedly elevated in OB progenitors deficient in CaMKK2. On the other hand, genetic ablation of CaMKK2 or its pharmacological inhibition in OC progenitors results in reduced pCREB as well as significantly reduced levels of its transcriptional target, nuclear factor of activated T cells, cytoplasmic (NFATc1). Moreover, in vivo administration of STO-609 results in increased OBs and diminished OCs, conferring significant protection from ovariectomy (OVX)-induced osteoporosis in adult mice. Overall, our findings reveal a novel function for CaMKK2 in bone remodeling and highlight the potential for its therapeutic inhibition as a valuable bone anabolic strategy that also inhibits OC differentiation in the treatment of osteoporosis.

UI MeSH Term Description Entries
D010006 Osteoblasts Bone-forming cells which secrete an EXTRACELLULAR MATRIX. HYDROXYAPATITE crystals are then deposited into the matrix to form bone. Osteoblast
D010010 Osteoclasts A large multinuclear cell associated with the BONE RESORPTION. An odontoclast, also called cementoclast, is cytomorphologically the same as an osteoclast and is involved in CEMENTUM resorption. Odontoclasts,Cementoclast,Cementoclasts,Odontoclast,Osteoclast
D010024 Osteoporosis Reduction of bone mass without alteration in the composition of bone, leading to fractures. Primary osteoporosis can be of two major types: postmenopausal osteoporosis (OSTEOPOROSIS, POSTMENOPAUSAL) and age-related or senile osteoporosis. Age-Related Osteoporosis,Bone Loss, Age-Related,Osteoporosis, Age-Related,Osteoporosis, Post-Traumatic,Osteoporosis, Senile,Senile Osteoporosis,Osteoporosis, Involutional,Age Related Osteoporosis,Age-Related Bone Loss,Age-Related Bone Losses,Age-Related Osteoporoses,Bone Loss, Age Related,Bone Losses, Age-Related,Osteoporoses,Osteoporoses, Age-Related,Osteoporoses, Senile,Osteoporosis, Age Related,Osteoporosis, Post Traumatic,Post-Traumatic Osteoporoses,Post-Traumatic Osteoporosis,Senile Osteoporoses
D010052 Ovariectomy The surgical removal of one or both ovaries. Castration, Female,Oophorectomy,Bilateral Ovariectomy,Bilateral Ovariectomies,Castrations, Female,Female Castration,Female Castrations,Oophorectomies,Ovariectomies,Ovariectomies, Bilateral,Ovariectomy, Bilateral
D001854 Bone Marrow Cells Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells. Bone Marrow Cell,Cell, Bone Marrow,Cells, Bone Marrow,Marrow Cell, Bone,Marrow Cells, Bone
D002454 Cell Differentiation Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs. Differentiation, Cell,Cell Differentiations,Differentiations, Cell
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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