HUMAN OSTEOCLASTS AND OSTEOCLAST-LIKE CELLS SYNTHESIZE AND RELEASE HIGH BASAL AND INFLAMMATORY STIMULATED LEVELS OF THE POTENT CHEMOKINE INTERLEUKIN-8

Chemokines, including interleukin-8 (IL-8), function as key mediators in diverse inflammatory disorders via promoting the recruitment, proliferation, and activation of vascular and immune cells. IL-8 levels are elevated in inflammatory diseases, such as rheumatoid arthritis, osteoarthritis, osteomyelitis, and periodontal disease, that also exhibit progressive bone loss. Therefore, it is possible that IL-8 contributes to the osteopenia associated with these pathological conditions. Although macrophages, neutrophils, and endothelial cells are considered the primary sources of inflammation-induced IL-8 increases, we report here for the first time that human bone marrow-derived osteoclast-like cells (hOCL) as well as authentic bone-resorbing human osteoclasts (hOC) isolated from osteoporotic femoral heads express messenger RNA (mRNA) for IL-8 and secrete high levels of IL-8 during culture. Basal IL-8 release by cultured hOC or hOCL was orders of magnitude greater than the release of the proinflammatory cytoki...