Advanced glycation end products upregulate the endoplasmic reticulum stress in human periodontal ligament cells.

Background: The accumulation of advanced glycation end products (AGEs) appears to be the main factor responsible for modulating periodontal inflammation in diabetes. The aim of this study is to examine the effects of AGEs on inflammation in human periodontal ligament cells and to investigate the mechanism with a specific emphasis on the role of endoplasmic reticulum (ER) stress-induced nuclear factor-kappa B (NF-kappa B) pathway. Methods: Cytotoxicity was measured by 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The protein expressions of ER markers and NF-kappa B were examined by Western blot analysis. The translocation of NF-kappa B was observed by immunofluorescence assay. Proinflammatory chemokine production was determined by enzyme-linked immunosorbent assay. Results: Treatment with AGEs reduced cell viability in a concentration- and time-dependent manner. AGEs induced ER stress, as evidenced by survival molecules, such as glucose-regulated protein 78 (GRP78), double-stranded RNA-activated protein kinase-like ER kinase (PERK), and activating transcription factor 6 (ATF-6), and apoptotic molecules, such as CCAAT/enhancer binding protein homologous protein (CHOP) and caspase 12. AGEs upregulated the nucleoprotein expression of NF-kappa B, enhanced translocation of NF-kappa B from the cytoplasm to the nucleus, and increased the production of proinflammatory chemokines interleukin-6 and interleukin-8. Conclusion: AGEs mediate inflammation of human periodontal ligament cells via the ER stress-induced NF-kappa B pathway.