INTERLEUKIN-1 AND BONE METABOLISM - A REVIEW

THIS REVIEW DISCUSSES the effects of interleukin-1 (IL-1) on bone metabolism and the evidence implicating IL-1 in periodontal disease. IL-1 is a potent cytokine with significant effects on the metabolism of many tissues, including bone. Several in vitro and in vivo studies have established the potent bone-resorbing effect of IL-1. Studies have indicated that IL-1 inhibits bone formation, although it can stimulate formation under certain conditions. Osteoblastic cells are the bone cells expressing IL-1 receptors and responding to IL-1. IL-1 effects on osteoblastic cells include stimulation of prostaglandin formation and modulation of gene expression of several proteins (cytokines, enzymes, enzyme inhibitors, matrix proteins, etc.) Osteoblastic cells also produce IL-1, suggesting an autocrine/paracrine function of IL-1 in bone. IL-1 has been shown to interact with other osteotropic factors, both systemic and local. These interactions modulate the effects of IL-1 on bone. The IL-1 effects on bone metabolism, along with other observations, suggest that IL-1 may be involved in the pathogenesis of bone diseases. Evidence from in vivo and in vitro studies suggests that IL-1 is an important factor in periodontal tissue breakdown. The ability of periodontopathic bacteria to stimulate IL-1 production, the detection of elevated IL-1 levels in periodontally-diseased tissues, and the effects of IL-1 on cells of the periodontium provide a plausible sequence of events in the pathogenesis of periodontal disease. Finally, therapeutic modalities aimed to control the actions of IL-1 are also discussed.