Malek A M, Izumo S
Department of Neurosurgery, Brigham & Women's Hospital, Boston, MA, USA.
J Cell Sci. 1996 Apr;109 ( Pt 4):713-26. doi: 10.1242/jcs.109.4.713.
Endothelium exposed to fluid shear stress (FSS) undergoes cell shape change, alignment and microfilament network remodeling in the direction of flow by an unknown mechanism. In this study we explore the role of tyrosine kinase (TK) activity, intracellular calcium ([Ca2+]i), mechanosensitive channels and cytoskeleton in the mechanism of cell shape change and actin stress fiber induction in bovine aortic endothelium (BAE). We report that FSS induces beta-actin mRNA in a time- and magnitude-dependent fashion. Treatment with quin2-AM to chelate intracellular calcium release and herbimycin A to inhibit TK activity abolished BAE shape change and actin stress fiber induction by FSS, while inhibition of protein kinase C with chelerythrine had no effect. Altering intermediate filament structure with acrylamide did not affect alignment or F-actin induction by FSS. Examining the role of the BAE cytoskeleton revealed a critical role for microtubules (MT). MT disruption with nocodazole blocked both FSS-induced morphological change and actin stress fiber induction. In contrast, MT hyperpolymerization with taxol attenuated the cell shape change but did not prevent actin stress fiber induction under flow. Mechanosensitive channels were found not to be involved in the FSS-induced shape change. Blocking the shear-activated current (IK.S) with barium and the stretch-activated cation channels (ISA) with gadolinium had no effect on the shear-induced changes in morphology and cytoskeleton. In summary, FSS has a profound effect on endothelial shape and F-actin network by a mechanism which depends on TK activity, intracellular calcium, and an intact microtubule network, but is independent of protein kinase C, intermediate filaments and shear- and stretch-activated mechanosensitive channels.
暴露于流体剪切力（FSS）的内皮细胞会通过未知机制发生细胞形状改变、排列以及微丝网络在流动方向上的重塑。在本研究中，我们探讨了酪氨酸激酶（TK）活性、细胞内钙（[Ca2+]i）、机械敏感通道和细胞骨架在牛主动脉内皮细胞（BAE）细胞形状改变和肌动蛋白应力纤维诱导机制中的作用。我们报告称，FSS以时间和强度依赖性方式诱导β-肌动蛋白mRNA。用喹2-AM螯合细胞内钙释放以及用赫曲霉素A抑制TK活性可消除FSS诱导的BAE细胞形状改变和肌动蛋白应力纤维诱导，而用白屈菜红碱抑制蛋白激酶C则没有效果。用丙烯酰胺改变中间丝结构并不影响FSS诱导的排列或F-肌动蛋白诱导。研究BAE细胞骨架的作用发现微管（MT）起关键作用。用诺考达唑破坏MT可阻断FSS诱导的形态变化和肌动蛋白应力纤维诱导。相反，用紫杉醇使MT过度聚合可减弱细胞形状改变，但不能阻止流动条件下肌动蛋白应力纤维的诱导。发现机械敏感通道不参与FSS诱导的形状改变。用钡阻断剪切激活电流（IK.S）以及用钆阻断牵张激活阳离子通道（ISA）对剪切诱导的形态和细胞骨架变化没有影响。总之，FSS通过一种依赖于TK活性、细胞内钙和完整微管网络，但独立于蛋白激酶C、中间丝以及剪切和牵张激活的机械敏感通道的机制，对内皮形状和F-肌动蛋白网络产生深远影响。
