The carotene p-hydroxycinnamic acid and the xanthophyll β-cryptoxanthin are members of the carotenoid family of plant-derived pigments, which are endowed with anti-osteoporotic properties in vivo. p-Hydroxycinnamic acid and β-cryptoxanthin have been demonstrated to stimulate osteoblastic bone formation while simultaneously repressing osteoclastic bone resorption in vitro. However, their mechanisms of action remain poorly elucidated. It is well established that the NF-;kgr;B signal transduction pathway plays a critical role in osteoclast differentiation. Moreover, we recently demonstrated that NF-κB activity potently antagonizes osteoblastic differentiation and mineralization in vitro. In this study, we used transient transfection assays of a NF-κB luciferase reporter to demonstrate that p-hydroxycinnamic acid and β-cryptoxanthin antagonize NF-κB activation in MC3T3 preosteoblastic cells. The data obtained suggest that NF-κB may be a common molecular target by which several bone active agents, including carotenoids, promote osteoblastic bone formation.

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