Retinoic Acid Increases Proliferation of Human Osteoclast Progenitors and Inhibits RANKL-Stimulated Osteoclast Differentiation by Suppressing RANK

It has been shown that high vitamin A intake is associated with bone fragility and fractures in both animals and humans. However, the mechanism by which vitamin A affects bones is unclear. In the present study, the direct effects of retinoic acid (RA) on human and murine osteoclastogenesis were evaluated using cultured peripheral blood CD14+ monocytes and RAW264.7 cells. Both the activity of the osteoclast marker tartrate resistant acid phosphatase (TRAP) in culture supernatant and the expression of the genes involved in osteoclast differentiation together with bone resorption were measured. To our knowledge, this is the first time that the effects of RA on human osteoclast progenitors and mature osteoclasts have been studied in vitro. RA stimulated proliferation of osteoclast progenitors both from humans and mice. In contrast, RA inhibited differentiation of the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis of human and murine osteoclast progenitors via retinoic acid receptors (RARs). We also show that the mRNA levels of receptor activator of nuclear factor κB (RANK), the key initiating factor and osteoclast associated receptor for RANKL, were potently suppressed by RA in osteoclast progenitors. More importantly, RA abolished the RANK protein in osteoclast progenitors. This inhibition could be partially reversed by a RAR pan-antagonist. Furthermore, RA treatment suppressed the expression of the transcription factor nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) and increased the expression of interferon regulatory factor-8 (IRF-8) in osteoclast progenitors via RARs. Also, RA demonstrated differential effects depending on the material supporting the cell culture. RA did not affect TRAP activity in the culture supernatant in the bone slice culture system, but inhibited the release of TRAP activity if cells were cultured on plastic. In conclusion, our results suggest that retinoic acid increases proliferation of human osteoclast progenitors and that it inhibits RANK-stimulated osteoclast differentiation by suppressing RANK

新抗真菌剤の血中濃度測定に関する基礎的研究

"1.BAY-b5097の血中濃度測定はC-pt.-4を試験菌とし,半合成培地Bを使用してBioassay比濁法により行なった. 2.標準発育阻止曲線より得られる測定可性欲は0.032～0.5μg/ml 3.正常ウナギにおけるBAY-b 5997血中濃度は投与1時間後に最高値に達し,5時間まで高濃度が続き,以後減少して24時間以降はほとんど検出されない. 4.C.-a.-5333感染ウサギにおけるBAY-b血中濃度は,正常ウサギのそれより低いが,推移は同じで1～2時間後に最高値となり,以下3～6時間維持される.24時間以後はほとんど検出されない. 5.ヒト血中濃度においては,164検体中0.032μg/ml以下が132検体,0.032～0.5μg/mlが24検体,0.5μg/ml以上7検体であった. 6.5-FCの血中濃度測定はMIC 0.016g/mlのC.pt-4を試験菌とし,BYMAを使用してカップ法により行なった. 7.標準発育阻止曲線より得られる5-FC測定可能域は2.5～100μg/ml. 8.正常ウサギにおける5-FC血中濃度は,経口投与後1時間で最高位に達し,3～5時間がピークで12時間では最高値の1/3以下,24時間以後はほとんど検出されない.最後にこの実験を行なうにあたり当研究施設の近藤譲,神戸俊夫両助手および森友世,末吉真知子両技官に御協力をいただきました.御高礼申上げます.