OPN N-glycosylation promoted bone destruction.

OBJECTIVES: Exploring the role of OPN N-glycosylation in osteoblasts and osteoclasts. METHODS: Immunohistochemistry was used to detect the expression of OPN in mice with apical periodontitis. The asparagine at position 79 of the OPN protein was mutated to glutamine, and the above plasmids were transfected into osteoblasts and osteoclasts. The effect of OPN N-glycosylation on proliferation of osteoblasts and osteoclasts was detected by CCK8 assays. Western blotting was used to detect the expression of OPN N-glycosylation on osteoclasts and osteoblasts. Detection of N-glycosylation of OPN activated the NF-κB signaling pathway to regulate osteoblasts and osteoclasts. RESULTS: OPN increased the expression in a mice model of apical periodontitis. The expression curve of OPN resembled a reverse V shape. The OPN N-glycosylation site was identified as 79 by MS. N-glycosylation of OPN promoted the proliferation of osteoclasts. But the N79 glycosylation site of mutant OPN could not increase the proliferation of osteoblasts. OPN N-glycosylation modulated the expression of osteoclast- and osteoblast-associated factors through the NF-κB signaling pathway. N-glycosylation of OPN promoted nuclear translocation of NF-κB in osteoclasts and osteoblasts. CONCLUSIONS: The N-glycosylation site of OPN is 79. N-glycosylation of OPN played an important role in the biological function of OPN protein.

Osteopontin Promotes Bone Destruction in Periapical Periodontitis by Activating the NF-κB Pathway.

BACKGROUND/AIMS: Periapical periodontitis is caused by bacterial infection and results in both one destruction and tooth loss. Osteopontin (OPN) is a secreted phosphorylated glycoprotein that participates in bone metabolism. METHODS: Thirty-three patients with chronic periapical periodontitis and 10 patients who had undergone the orthodontic removal of healthy tooth tissue (control) at the periodontal ligament were investigated, and an animal model of mouse periapical periodontitis was established for an in vivo analysis. The relationship between OPN and bone destruction during periapical periodontitis was analyzed. Osteoblasts and osteoclasts were cultured in vitro and treated with lipopolysaccharide. An inhibitor of NF-κB was used to pretreat the transfected cells. RESULTS: OPN increased osteoclast proliferation and differentiation, but reduced osteoblasts proliferation and differentiation. OPN activated the NF-κB pathway during periapical periodontitis and accelerated the transfer and phosphorylation of P65 from the cytoplasm to the nucleus. CONCLUSION: This study demonstrated that OPN played important roles in the progression of periapical periodontitis, and a dual role in bone metabolism during periapical periodontitis, linking osteoclasts and osteoblasts. The underlying mechanism may be related to the NF-κB pathway.