You J, Reilly G C, Zhen X, Yellowley C E, Chen Q, Donahue H J, Jacobs C R
Musculoskeletal Research Laboratory, Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
J Biol Chem. 2001 Apr 20;276(16):13365-71. doi: 10.1074/jbc.M009846200. Epub 2001 Jan 26.
Recently fluid flow has been shown to be a potent physical stimulus in the regulation of bone cell metabolism. However, most investigators have applied steady or pulsing flow profiles rather than oscillatory fluid flow, which occurs in vivo because of mechanical loading. Here oscillatory fluid flow was demonstrated to be a potentially important physical signal for loading-induced changes in bone cell metabolism. We selected three well known biological response variables including intracellular calcium (Ca(2+)i), mitogen-activated protein kinase (MAPK) activity, and osteopontin (OPN) mRNA levels to examine the response of MC3T3-E1 osteoblastic cells to oscillatory fluid flow with shear stresses ranging from 2 to -2 Newtons/m(2) at 1 Hz, which is in the range expected to occur during routine physical activities. Our results showed that within 1 min, oscillatory flow induced cell Ca(2+)i mobilization, whereas two MAPKs (ERK and p38) were activated over a 2-h time frame. However, there was no activation of JNK. Furthermore 2 h of oscillatory fluid flow increased steady-state OPN mRNA expression levels by approximately 4-fold, 24 h after exposure to fluid flow. The presence of both ERK and p38 inhibitors and thapsigargin completely abolished the effect of oscillatory flow on steady-state OPN mRNA levels. In addition, experiments using a variety of pharmacological agents suggest that oscillatory flow induces Ca(2+)i mobilization via the L-type voltage-operated calcium channel and the inositol 1,4,5-trisphosphate pathway.
最近研究表明，流体流动是调节骨细胞代谢的一种强大物理刺激。然而，大多数研究人员采用的是稳定或脉冲流模式，而非体内因机械负荷产生的振荡流体流动。本文证明，振荡流体流动对于负荷诱导的骨细胞代谢变化可能是一个重要的物理信号。我们选择了三个著名的生物学反应变量，包括细胞内钙（Ca(2+)i）、丝裂原活化蛋白激酶（MAPK）活性和骨桥蛋白（OPN）mRNA水平，以研究MC3T3-E1成骨细胞在1Hz频率下，剪切应力范围为2至-2牛顿/平方米的振荡流体流动作用下的反应，该频率范围预计在日常体育活动中出现。我们的结果显示，在1分钟内，振荡流诱导细胞Ca(2+)i动员，而两种MAPK（ERK和p38）在2小时的时间范围内被激活。然而，JNK未被激活。此外，振荡流体流动2小时后，稳态OPN mRNA表达水平在暴露于流体流动24小时后增加了约4倍。ERK和p38抑制剂以及毒胡萝卜素的存在完全消除了振荡流对稳态OPN mRNA水平的影响。此外，使用各种药剂进行的实验表明，振荡流通过L型电压门控钙通道和肌醇1,4,5-三磷酸途径诱导Ca(2+)i动员。
