Direct effect of calcium channel antagonists on osteoclast function: alterations in bone resorption and intracellular calcium concentrations.
Direct effect of calcium channel antagonists on osteoclast function: alterations in bone resorption and intracellular calcium concentrations.
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DOI：
10.1210/endo.135.3.8070395
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发表时间：
1994-09
期刊：
影响因子：
4.8
通讯作者：
C. Ritchie;P. Maercklein;L. Fitzpatrick
中科院分区：
文献类型：
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作者：
C. Ritchie;P. Maercklein;L. Fitzpatrick
破骨细胞附着在矿化表面并吸收骨基质，将钙释放到破骨细胞周围的区域。高水平的细胞外钙的产生增加了细胞内钙浓度（[Ca2+]i），骨吸收减少。为了研究这一机制，我们采用破骨细胞坑法研究了二氢吡啶敏感的l型钙通道拮抗剂PN 200-110、（-）202-791和硝苯地平对骨吸收的影响。用氟探针fura2测定这些化合物处理后[Ca2+]i的变化。在富含破骨细胞的培养中，在PN 200-110和（-）202-791的存在下，骨吸收显著减少。骨吸收的减少与[Ca2+]i的增加相关。为了确定这些化合物对破骨细胞的作用是否通过成骨细胞介导，我们检测了添加这些药物后大鼠成骨样细胞（ROS 17/2.8）的增殖和分化情况。通过[3H]胸腺嘧啶掺入和碱性磷酸酶的特定活性来确定，在分解坑试验中，这些化合物以抑制骨吸收的浓度处理后，成骨细胞的增殖或分化没有变化。钙通道拮抗剂在抑制破骨细胞功能的浓度下对成骨细胞生长和分化缺乏影响，这表明PN 200-110和（-）202-791对破骨细胞的影响不是通过成骨细胞介导的。此外，与无细胞培养的条件培养基相比，经pn200 -110或（-）202-791处理的ROS 17/2.8培养物的条件培养基对坑的形成没有影响。钙通道条件介质对骨吸收影响的缺乏提供了额外的证据，证明PN 200-110和（-）202-791通过改变破骨细胞功能直接减少骨吸收，而不是通过成骨-破骨细胞相互作用。在破骨细胞中添加（-）202-791或PN 200-110导致[Ca2+]i的剂量依赖性升高。这些数据表明，钙通道拮抗剂可能与破骨细胞的钙通道结合并将其锁定在开放状态，导致[Ca2+]i增加和骨吸收减少。
Osteoclasts attach to mineralized surfaces and resorb bone matrix, releasing calcium into the area surrounding the osteoclast. The production of high levels of extracellular calcium increases intracellular calcium concentrations ([Ca2+]i), and bone resorption is decreased. To study this mechanism, the dihydropyridine-sensitive L-type calcium channel antagonists PN 200-110, (-)202-791, and nifedipine were studied for their effects on bone resorption using the disaggregated osteoclast pit assay. Changes in [Ca2+]i after treatment with these compounds were determined with the fluoroprobe fura2. In osteoclast-enriched cultures, significant decreases in bone resorption were noted in the presence of PN 200-110 and (-)202-791. The decrease in bone resorption correlated with an increase in [Ca2+]i. To determine whether the effects of these compounds on osteoclasts were mediated via osteoblasts, proliferation and differentiation of rat osteoblast-like cells (ROS 17/2.8) were examined after the addition of these agents. There were no changes in osteoblast proliferation or differentiation, as determined by [3H]thymidine incorporation and specific activity of alkaline phosphatase, after treatment with these compounds at concentrations that inhibited bone resorption in the disaggregated pit assay. This lack of effect of calcium channel antagonists on osteoblast growth and differentiation at concentrations used to inhibit osteoclast function suggests that the effects of PN 200-110 and (-)202-791 on the osteoclast are not mediated via the osteoblast. In addition, conditioned medium recovered from ROS 17/2.8 cultures treated with PN 200-110 or (-)202-791 had no effect on pit formation compared to the conditioned medium from cell-free cultures. This lack of effect of calcium channel conditioned medium on bone resorption provides additional evidence that PN 200-110 and (-)202-791 are decreasing bone resorption directly by altering osteoclast function, not through osteoblast-osteoclast interactions. The addition of (-)202-791 or PN 200-110 to osteoclasts resulted in a dose-dependent rise in [Ca2+]i. These data suggest that calcium channel antagonists may bind to the calcium channel of the osteoclast and lock it in an open state, leading to increased [Ca2+]i and decreased bone resorption.