骨質疏鬆症是發生在老年人，尤其是雌激素缺乏的停經後婦女的疾病。在骨質疏鬆症中骨質的流失是由於骨骼的重塑不平衡，蝕骨細胞增加蝕骨作用和造骨細胞抑制骨質生成作用。蝕骨前驅細胞遷移到骨頭是蝕骨細胞分化的起始過程。蝕骨細胞從蝕骨前驅細胞分化對蝕骨細胞提供其蝕骨作用是重要的。雌激素藉由抑制蝕骨細胞分化來提供對骨頭的抗蝕骨作用。然而，雌激素抑制蝕骨前驅細胞遷移的機制仍是未知的。脂多醣引起蝕骨前驅細胞遷移和分化。細胞遷移需要肌動蛋白和鈣離子流入。Transient receptor potential (TRP) 通道是讓鈣離子流入非興奮性細胞，例如蝕骨細胞。因此我們假設脂多醣誘發TRP通道增加鈣離子的流入，影響肌動蛋白的聚合作用並導致細胞遷移。雌激素抑制脂多醣誘發的細胞遷移。我們的結果顯示ionomycin觸動鈣離子流入倒轉雌激素對脂多醣誘發細胞遷移的阻斷作用。阻斷肌動蛋白聚合作用阻礙了ionomycin對抗雌激素抑制在蝕骨前驅細胞中脂多醣誘發的細胞遷移。辣椒素是TRP vanilloid 1離子通道的活化劑，其具有和ionomycin相同的倒轉雌激素對脂多醣誘發細胞遷移的阻斷作用。我們的發現推測雌激素對脂多醣誘發蝕骨前驅細胞遷移的抑制作用需要肌動蛋白和細胞外鈣離子，而鈣離子的流入來源可能是來自於TRP通道。總結來說，我們提議雌激素藉由干擾TRP通道抑制鈣離子流入，擾亂肌動蛋白聚合作用而因起抑制了脂多醣誘發的細胞遷移而這現象可能經由雌激素受體貝它。

Osteoporosis is a disease found in elderly and most in postmenopausal women whose estrogen is deficient. The bone loss in osteoporosis is due to imbalance in bone remodeling with elevated bone resorption by osteoclast and suppressed new bone formation by osteoblast. Migration of osteoclast precursors to bone is the initiation process of osteoclast differentiation. Differentiation of osteoclasts from osteoclast precursors is important for osteoclast to provide its function in bone resorption. 17β-estradiol (estrogen, E2) provides an anti-resorptive effect on bone through inhibiting osteoclast differentiation. However, it is still unknown the mechanism of E2 on osteoclast precursor migration. Lipopolysaccharides (LPS) induce osteoclast precursor cell migration and differentiation. Cell migration requires actin polymerization and Ca2+ influx. Transient receptor potential (TRP) channel is a possible pathway for Ca2+ to flow in nonexcitable cells, such as osteoclasts. Therefore, we hypothesized that E2 inhibits LPS-induced migration in osteoclast precursors. According to our data, we suggested that LPS induced TRP channel to increase Ca2+ influx and thus influence actin polymerization and result in cell migration. E2 significantly suppressed LPS-induced cell migration. Triggering Ca2+ influx by ionomycin reversed the inhibitory effect of E2 on LPS-induced migration. Blocking actin polymerization hindered the counteracting effect of ionomycin on LPS-induced migration which is inhibited by E2 in osteoclast precursors. Capsaicin, a TRP vanilloid 1 ion channel activator, had the same effect as ionomycin to reverse the inhibitory effect of E2 on LPS-induced migration in osteoclast. Our findings indicated that inhibitory effect of activated ERβ on LPS-induced osteoclast precursor cell migration required actin polymerization and extracellular Ca2+ and the influx source of Ca2+ may be from TRP channel. To conclude, we proposed that activated ERβ inhibited Ca2+ influx by interfering TRP, disturbed actin polymerization and thus blocked LPS-induced cell migration.

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