Lipopolysaccharide of Aggregatibacter actinomycetemcomitans up‐regulates inflammatory cytokines, prostaglandin E2 synthesis and osteoclast formation in interleukin‐1 receptor antagonist‐deficient mice. (16th April 2013)

• Record Type: Journal Article
• Authors: Mizutani, H.; Ishihara, Y.; Izawa, A.; Fujihara, Y.; Kobayashi, S.; Gotou, H.; Okabe, E.; Takeda, H.; Ozawa, Y.; Kamiya, Y.; Kamei, H.; Kikuchi, T.; Yamamoto, G.; Mitani, A.; Nishihara, T.; Noguchi, T.
• Is Part Of: Journal of periodontal research. Volume 48:Number 6(2013:Dec.)
• Page Start: 748
• Page End: 756
• Publication Date: 2013-04-16
• Subjects: cyclooxygenase‐2 -- periodontal disease -- prostaglandin E2 -- prostanoid receptor EP4; Periodontics -- Periodicals; 617.632
• DOI: 10.1111/jre.12065
• Languages: English
• ISSNs: 0022-3484

Abstract

Abstract : Background and Objective: The interleukin (IL)‐1 receptor antagonist (Ra) binds to IL‐1 receptors and inhibits IL‐1 activity. However, it is unclear whether the IL‐1Ra plays a protective role in periodontal disease. The purpose of this study was to compare IL‐1Ra knockout (KO) and wild‐type (WT) mice in regard to proinflammatory cytokine production, osteoclast formation and bone resorption in response to periodontal bacterial lipopolysaccharide (LPS). Material and Methods: Peritoneal macrophages (Mφs) were obtained from 13‐wk‐old IL‐1Ra KO and WT mice. Peritoneal Mφs were cultured with or without 10 μg/mL of Aggregatibacter actinomycetemcomitans LPS for 24 h. The levels of IL‐1alpha (IL‐1α), IL‐1beta (IL‐1β), tumor necrosis factor‐α (TNF‐α) and IL‐6 were measured in periotoneal Mφs supernatant fluid (PM‐SF) using an ELISA. Bone marrow cells were obtained from the mice and stimulated with PM‐SF for 9 d, then stained with TRAP. The frequency of TRAP‐positive multinucleated giant cell formation was calculated based on a fusion index. PM‐SF‐stimulated calvarial bone resorption was analyzed using micro‐computed tomography, and calvarial histological analysis was performed using hematoxylin and eosin and TRAP staining. The expression of cyclooxygenase‐2 ( Cox2 ), prostanoid receptor EP4 ( Ep4 ) and Rank mRNAs in bone marrow cells were measured using real‐time quantitative PCR, while prostaglandin E2 (PGE2 ) production was determined by ELISA. Results: The levels of IL‐1α, IL‐1β, TNF‐α and IL‐6 in IL‐1Ra KO mice PM‐SF stimulated with A. actinomycetemcomitans LPS were significantly increased by approximately 4‐ ( p < 0.05), 5‐ ( p < 0.05), 1.3‐ ( p < 0.05) and 6‐ ( p < 0.05) fold, respectively, compared with the levels in WT mice. Moreover, osteoclast formation, expression of Rank, Ep4 and Cox2 mRNAs and production of PGE2 were significantly increased by approximately 2‐ ( p < 0.05), 1.6‐ ( p < 0.05), 2.5‐ ( p < 0.05), 1.6‐ ( p < 0.05) and 1.9‐ ( p < 0.05) fold, respectively, in IL‐1Ra KO mice stimulated with A. actinomycetemcomitans LPS compared with WT mice. Conclusion: IL‐1Ra regulates IL‐1 activity and appears to reduce the levels of other inflammatory cytokines, including TNF‐α and IL‐6, while it also reduces expression of the EP4 receptor related to prostanoid sensitivity and osteoclast formation. These results suggest that IL‐1Ra is an important molecule for inhibition of inflammatory periodontal bone resorption.