Actinobacillus actinomycetemcomitans Y4 capsular-polysaccharide-like polysaccharide promotes osteoclast-like cell formation by interleukin-1α production in mouse marrow cultures

The mechanism of osteoclast-like cell formation induced by periodontopathic bacterium Actinobacillus actinomycetemcomitans Y4 (serotype b) capsular-polysaccharide-like polysaccharide (capsular-like polysaccharide) was examined in a mouse bone marrow culture system. When mouse bone marrow cells were cultured with A. actinomycetemcomitans Y4 capsular-like polysaccharide for 9 days, many multinucleated cells were formed. The multinucleated cells showed several characteristics of osteoclasts, including tartrate-resistant acid phosphatase (TRACP) and the ability to resorb the calcified dentine. In this study, we examined the effects of antisera to interleukins on the formation of osteoclast-like cells induced by A. actinomycetemcomitans Y4 capsular-like polysaccharide. Monospecific anti- mouse recombinant interleukin-1α (rIL-1α) serum completely inhibited the formation of osteoclast-like cells in the presence of A. actinomycetemcomitans Y4 capsular-like polysaccharide. However, anti-mouse rIL-1β and anti-mouse rIL-6 sera showed no effect on osteoclast-like cell formation. IL-1 receptor antagonist significantly inhibited the osteoclast- like cell formation mediated by A. actinomycetemcomitans Y4 capsular-like polysaccharide in mouse marrow cultures. The bioactive IL-1 was detected in the culture media of mouse bone marrow cells stimulated with A. actinomycetemcomitans Y4 capsular-like polysaccharide. These results indicate that IL-1α is involved in the mechanism of the formation of osteoclast-like cells induced by A. actinomycetemcomitans Y4 capsular-like polysaccharide. We sought to determine whether osteoclast-like cell formation induced by A. actinomycetemcomitans Y4 capsular-like polysaccharide could be modulated by the protein kinase inhibitors H8 and HA1004. The formation of osteoclast- like cells was suppressed by H8 and HA1004. These findings suggest that the signals by protein kinases may regulate osteoclast-like cell formation induced by A. actinomycetemcomitans Y4 capsular-like polysaccharide. Furthermore, a correlation between IL-1α and prostaglandin E₂ in the osteoclast recruitment induced by A. actinomycetemcomitans Y4 capsular-like polysaccharide is discussed.