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Lipopolysaccharide of A ggregatibacter actinomycetemcomitans up‐regulates inflammatory cytokines, prostaglandin E 2 synthesis and osteoclast formation in interleukin‐1 receptor antagonist‐deficient mice
Author(s) -
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.
Publication year - 2013
Publication title -
journal of periodontal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.31
H-Index - 83
eISSN - 1600-0765
pISSN - 0022-3484
DOI - 10.1111/jre.12065
Subject(s) - aggregatibacter actinomycetemcomitans , lipopolysaccharide , osteoclast , bone resorption , prostaglandin e2 , chemistry , proinflammatory cytokine , osteoprotegerin , interleukin , tumor necrosis factor alpha , endocrinology , medicine , cytokine , receptor antagonist , porphyromonas gingivalis , receptor , microbiology and biotechnology , periodontitis , inflammation , biology , antagonist , activator (genetics)
Background and Objective The interleukin ( IL )‐1 receptor antagonist ( R a) binds to IL ‐1 receptors and inhibits IL ‐1 activity. However, it is unclear whether the IL ‐1 R a plays a protective role in periodontal disease. The purpose of this study was to compare IL ‐1 R a 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 ( M φs) were obtained from 13‐wk‐old IL ‐1 R a KO and WT mice. Peritoneal M φs were cultured with or without 10 μg/mL of A ggregatibacter 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 M φs 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 ( Cox 2 ), prostanoid receptor EP 4 ( Ep4 ) and Rank m RNAs in bone marrow cells were measured using real‐time quantitative PCR , while prostaglandin E 2 ( PGE 2 ) production was determined by ELISA . Results The levels of IL ‐1α, IL ‐1β, TNF ‐α and IL ‐6 in IL ‐1 R a 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 , Ep 4 and Cox2 m RNAs and production of PGE 2 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 ‐1 R a KO mice stimulated with A . actinomycetemcomitans LPS compared with WT mice. Conclusion IL ‐1 R a 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 EP 4 receptor related to prostanoid sensitivity and osteoclast formation. These results suggest that IL ‐1 R a is an important molecule for inhibition of inflammatory periodontal bone resorption.