The presence and activity of the receptor for advanced glycation end products in osteoblasts
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The AGEs (Advanced Glycation End products) are a heterogeneous class of compounds and are the ultimate products of non-enzymatic glycation and oxidation of proteins and lipids. Studies have shown that AGEs result from hyperglycemia and diabetes and contribute to related complications, leading to connective tissue, neurological, and end-stage renal diseases. Possible mechanisms include the interaction of AGEs with AGE receptors, which can change cell behavior and phenotype. The best characterized AGE receptor is RAGE (Receptor for Advanced Glycation End products), which is a member of immunoglobulin superfamily and is expressed in a wide range of cell types, including endothelial cells, monocytes, smooth muscle cells and fibroblasts. The purpose of this study was to investigate whether RAGE is expressed in osteoblastic cells and whether it has functional activities. Western blot studies of cell extracts show that RAGE is present in both MC3T3E1 cells and primary rat osteoblasts. Binding studies with a known RAGE ligand [epsilon](carboxymethyl) lysine modified albumin (CML-BSA) demonstrate that the binding is saturable and specific. CML-BSA was found to cause NF-kB activation in osteoblastic cells, which was blocked by the anti-RAGE antibody. CML-BSA also decreased the mRNA levels of BMP-1, 4 and OPG, which are bone-formation related proteins. CML-collagen inhibited differentiation of osteoblastic cells, as shown by an inhibition of mineralization. Conclusion: RAGE is expressed in osteoblastic cells and specifically binds to a defined AGE structure. The AGE-RAGE interaction causes the activation of a transcription factor, which may lead to the changes in the expressions of bone growth factors and to inhibition of differentiation. This mechanism may contribute to osteopenia that occurs in type 1 diabetes.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (D.Sc.)--Boston University, Henry M. Goldman School of Dental Medicine, 2002 (Periodontology and Oral Biology).Includes bibliographical references (leaves 65-76).
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