title: Advanced glycation end products stimulate osteoblast apoptosis via the MAP kinase and cytosolic apoptotic pathways.
abstract: We have previously shown that diabetes significantly enhances apoptosis of osteoblastic cells in vivo and that the enhanced apoptosis contributes to diabetes impaired new bone formation. A potential mechanism is enhanced apoptosis stimulated by advanced glycation end products (AGEs). To investigate this further, an advanced glycation product, carboxymethyl lysine modified collagen (CML-collagen), was injected in vivo and stimulated a 5-fold increase in calvarial periosteal cell apoptosis compared to unmodified collagen. It also induced apoptosis in primary cultures of human or neonatal rat osteoblastic cells or MC3T3-E1 cells in vitro. Moreover, the apoptotic effect was largely mediated through RAGE receptor. CML-collagen increased p38 and JNK activity 3.2- and 4.4-fold, respectively. Inhibition of p38 and JNK reduced CML-collagen stimulated apoptosis by 45% and 59% and by 90% when used together (P<0.05). The predominant apoptotic pathway induced by CML-collagen involved caspase-8 activation of caspase-3 and was independent of NF-kappaB activation. When osteoblastic cells were exposed to a long-term low dose incubation with CML-collagen, there was a higher degree of apoptosis compared to short-term incubation. In more differentiated osteoblastic cultures, apoptosis was enhanced even further. These results indicate that advanced glycation end products, which accumulate in diabetic and aged individuals, may promote apoptosis of osteoblastic cells and contribute to deficient bone formation.
authors.affiliation: Department of Periodontology and Oral Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA.
authors.forename: Mani
authors.initials: M
authors.lastname: Alikhani
authors.forename: Zoubin
authors.initials: Z
authors.lastname: Alikhani
authors.forename: Coy
authors.initials: C
authors.lastname: Boyd
authors.forename: Christine M
authors.initials: CM
authors.lastname: MacLellan
authors.forename: Markos
authors.initials: M
authors.lastname: Raptis
authors.forename: Rongkun
authors.initials: R
authors.lastname: Liu
authors.forename: Nicole
authors.initials: N
authors.lastname: Pischon
authors.forename: Philip C
authors.initials: PC
authors.lastname: Trackman
authors.forename: Louis
authors.initials: L
authors.lastname: Gerstenfeld
authors.forename: Dana T
authors.initials: DT
authors.lastname: Graves
mesh_terms: D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D004789:Enzyme Activation; D017127:Glycation End Products, Advanced / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D017127:Glycation End Products, Advanced; D016328:NF-kappa B; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D003094:Collagen; D020169:Caspases