Fluid shear stress inhibits TNF-α-induced apoptosis in osteoblasts:: A role for fluid shear stress-induced activation of P13-kinase and inhibition of caspase-3
Fluid shear stress inhibits TNF-α-induced apoptosis in osteoblasts:: A role for fluid shear stress-induced activation of P13-kinase and inhibition of caspase-3
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DOI：
10.1002/jcp.10221
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发表时间：
2003-02-01
影响因子：
5.6
通讯作者：
Norvell, SM
中科院分区：
文献类型：
--
作者：
Pavalko, FM;Gerard, RL;Norvell, SM
在骨中，大部分成骨细胞（负责沉积新骨的细胞）通常经历程序性细胞死亡（凋亡）。由于骨的机械负荷增加了新骨形成的速率，我们假设成骨细胞的机械刺激可能会增加它们的存活率。为了验证这一假设，我们使用三种成骨细胞类型：原代大鼠颅骨成骨细胞（RCOB），MC 3 T3-E1成骨细胞和UMR 106骨肉瘤细胞，研究了流体剪切力（FSS）对成骨细胞凋亡的影响。在环己酰胺（CHX）存在下用TNF-α处理细胞以快速诱导细胞凋亡。成骨细胞在TNF-α和CHX暴露4-6小时内显示出明显的凋亡迹象，并且FSS（12 dyne/cm（2））的应用显著减弱了TNF-α诱导的凋亡。FSS激活PI 3-激酶信号诱导Akt磷酸化，并抑制TNF-α诱导的caspase-3活化。使用LY 294002抑制PI 3激酶，阻断了FSS从TNF α诱导的凋亡中拯救成骨细胞的能力，并阻断了FSS诱导的TNF-α处理的成骨细胞中caspase-3活化的抑制。然而，LY 94002并不能阻止FSS诱导的Akt磷酸化，这表明单独激活Akt不足以拯救细胞免于凋亡。这一结果也表明，FSS可以通过PI 3激酶非依赖性途径激活Akt。这些研究第一次证明，在体外将FSS应用于成骨细胞，通过涉及PI 3-激酶信号传导激活和半胱天冬酶抑制的机制抑制TNF-α诱导的细胞凋亡。FSS诱导的PI 3-激酶活化可能通过与Akt介导的存活途径不同的机制促进细胞存活。(C)2002 Wiley-Liss，Inc.
In bone, a large proportion of osteoblasts, the cells responsible for deposition of new bone, normally undergo programmed cell death (apoptosis). Because mechanical loading of bone increases the rate of new bone formation, we hypothesized that mechanical stimulation of osteoblasts might increase their survival. To test this hypothesis, we investigated the effects of fluid shear stress (FSS) on osteoblast apoptosis using three osteablast cell types: primary rat calvarial osteoblasts (RCOB), MC3T3-E1 osteoblastic cells, and UMR106 osteosarcoma cells. Cells were treated With TNF-alpha in the presence of cyclohexamide (CHX) to rapidly induce apoptosis. Osteoblasts showed significant signs of apoptosis within 4-6 h of exposure to TNF-alpha and CHX, and application of FSS (12 dyne/cm(2)) significantly attenuated this TNFalpha-induced apoptosis. FSS activated PI3-kinase signaling induced phosphorylation of Akt, and inhibited TNF-alpha-induced activation of caspase-3. Inhibition of PI3-kinase, using LY294002, blocked the ability of FSS to rescue osteoblasts from TNFalpha-induced apoptosis and blocked FSS-induced inhibition of caspase-3 activation in osteoblasts treated with TNF-alpha. LY94002 did not, however, prevent FSS-induced phosphorylation of Akt suggesting that activation of Akt alone is not sufficient to rescue cells from apoptosis. This result also suggests that FSS can activate Akt via a PI3-kinase-independent pathway. These studies demonstrate for the first time that application of FSS to osteoblasts, in vitro results in inhibition of TNF-alpha-induced apoptosis through a mechanism involving activation of PI3-kinase signaling and inhibition of caspases. FSS-induced activation of PI3-kinase may promote cell survival through a mechanism that is distinct from the Akt-mediated survival pathway. (C) 2002 Wiley-Liss, Inc.