Nuclear Factor-kappaB Dependent Induction of TNF-alpha and IL-1beta by the Aggregatibacter actinomycetemcomitans Lipopolysaccharide in RAW 264.7 Cells

ABSTRACT

Aggregatibacter actinomycetemcomitans is an important pathogen in the development of localized aggressive periodontitis. Lipopolysaccharide (LPS) is a virulent factor of periodontal pathogens that contributes to alveolar bone loss and connective tissue degradation in periodontal disease. Our present study was designed to investigate the cytokine expression and signaling pathways regulated by A. actinomycetemcomitans LPS (Aa LPS). Cytokine gene expression profiling in RAW 264.7 cells was performed by microarray analyses. The cytokine mRNA and protein levels and related signaling pathways induced by Aa LPS were measured by RT-PCR, ELISA and western blotting. Microarray results showed that Aa LPS strongly induced the expression of NF-kappaB, NF-kappaB-related genes, inflammatory cytokines, TNF-alpha and IL-1beta in RAW 264.7 cells. NF-kappaB inhibitor pretreatment significantly reduced the levels of TNF-alpha and IL-1beta mRNA and protein. In addition, the Aa LPS-induced TNF-alpha and IL-1beta expression was inhibited by p38/JNK MAP kinase inhibitor pretreatment. These results show that Aa LPS stimulates TNF-alpha and IL-1beta expression through NF-kappaB and p38/JNK activation in RAW 264.7 cells, suggesting the essential role of this pathway in the pathogenesis of localized aggressive periodontitis.