Osteoclasts activation by bacterial endotoxins during periodontal diseases

During periodontal infections, bacterial lipopolysaccharides (LPS) from Gram negative bacteria, along with other bacterial products, drive alveolar bone destruction. Tissue destruction occurs through both direct and indirect pathways. In the indirect pathway, LPS induce the secretion of proinflammatory cytokines, which in turn provokes a cascade of reactions leading to osteoclasts activation. In the direct pathway, LPS stimulate osteoblasts, osteoclasts precursors and osteoclasts, with an inflammatory cytokines independent manner. In this paper, the mechanisms involved in these two pathways are reviewed.