EFFECT OF NICOTINE ON OSTEOCLASTOGENESIS

Abstract

Smoking has been identified as a risk factor for osteoporosis, but the basis for this relationship is unknown. Although previous studies have examined the effect of nicotine on osteoblasts, few studies have focused on its effect on osteoclasts. PURPOSE The purpose of this study was to determine if nicotine, a major constituent in tobacco, affected the formation of osteoclasts, the cells that resorb bone. METHODS Osteoclast formation from mononuclear precursor cells in primary cultures of murine bone marrow was stimulated by treatment with 25nM parathyroid hormone related peptide (PTHrP). Osteoclasts and their precursor cells were identified by their morphology and histochemical staining for tartrate-resistant acid phosphatase (TRAP). Cultures were exposed to nicotine at concentrations ranging from 0.05 uM to 500 uM. The effect of nicotine on osteoclastogenesis on days 1–6 was determined by counting the number of TRAP positive mononuclear cells, TRAP positive multinuclear cells, and the number of nuclei per osteoclast. RESULTS Treatment with nicotine significantly reduced the number of preosteoclasts on days 3–6, osteoclasts on days 4–6, and the number of nuclei per osteoclast on day 6. These results demonstrate that nicotine inhibited PTHrP-stimulated osteoclastogenesis in vitro. The time-course of the effects of nicotine on the measured endpoints suggests that the decrease in osteoclastogenesis was due to the decline in osteoclast precursors. CONCLUSION These results suggest that bone loss associated with tobacco use may be related to an altered balance between bone formation and resorption. Supported by a grant from the State of Nebraska Cancer and Smoking Disease Research Program.