Deng Linhong, Fairbank Nigel J, Fabry Ben, Smith Paul G, Maksym Geoffrey N
School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, Halifax, Nova Scotia, Canada B3H 3J5.
Am J Physiol Cell Physiol. 2004 Aug;287(2):C440-8. doi: 10.1152/ajpcell.00374.2003. Epub 2004 Apr 7.
Mechanical stress (MS) causes cytoskeletal (CSK) and phenotypic changes in cells. Such changes in airway smooth muscle (ASM) cells might contribute to the pathophysiology of asthma. We have shown that periodic mechanical strain applied to cultured ASM cells alters the structure and expression of CSK proteins and increases cell stiffness and contractility (Smith PG, Moreno R, and Ikebe M. Am J Physiol Lung Cell Mol Physiol 272: L20-L27, 1997; and Smith PG, Deng L, Fredberg JJ, and Maksym GN. Am J Physiol Lung Cell Mol Physiol 285: L456-L463, 2003). However, the mechanically induced CSK changes, altered cell function, and their time courses are not well understood. Here we applied MS to the CSK by magnetically oscillating ferrimagnetic beads bound to the CSK. We quantified CSK remodeling by measuring actin accumulation at the sites of applied MS using fluorescence microscopy. We also measured CSK stiffness using optical magnetic twisting cytometry. We found that, during MS of up to 120 min, the percentage of beads associated with actin structures increased with time. At 60 min, 68.1 +/- 1.6% of the beads were associated with actin structures compared with only 6.7 +/- 2.8% before MS and 38.4 +/- 5.5% in time-matched controls (P < 0.05). Similarly, CSK stiffness increased more than twofold in response to the MS compared with time-matched controls. These changes were more pronounced than observed with contractile stimulation by 80 mM KCl or 10(-4) M acetylcholine. Together, these findings imply that MS is a potent stimulus to enhance stiffness and contractility of ASM cells through CSK remodeling, which may have important implications in airway narrowing and dilation in asthma.
机械应力（MS）会导致细胞内细胞骨架（CSK）及表型发生变化。气道平滑肌（ASM）细胞的此类变化可能在哮喘的病理生理学中发挥作用。我们已经表明，施加于培养的ASM细胞的周期性机械应变会改变CSK蛋白的结构和表达，并增加细胞硬度和收缩性（Smith PG、Moreno R和Ikebe M。《美国生理学杂志：肺细胞与分子生理学》272：L20 - L27，1997；以及Smith PG、Deng L、Fredberg JJ和Maksym GN。《美国生理学杂志：肺细胞与分子生理学》285：L456 - L463，2003）。然而，机械诱导的CSK变化、细胞功能改变及其时间进程尚未得到充分了解。在此，我们通过磁振荡与CSK结合的亚铁磁性珠子对CSK施加MS。我们使用荧光显微镜通过测量施加MS部位的肌动蛋白积累来量化CSK重塑。我们还使用光磁扭转细胞术测量CSK硬度。我们发现，在长达120分钟的MS过程中，与肌动蛋白结构相关的珠子百分比随时间增加。在60分钟时，68.1±1.6%的珠子与肌动蛋白结构相关，而在MS之前仅为6.7±2.8%，在时间匹配的对照组中为38.4±5.5%（P < 0.05）。同样，与时间匹配的对照组相比，CSK硬度在MS作用下增加了两倍多。这些变化比用80 mM KCl或10⁻⁴ M乙酰胆碱进行收缩刺激时观察到的更为明显。总之，这些发现表明MS是一种通过CSK重塑增强ASM细胞硬度和收缩性的有效刺激，这可能对哮喘中气道狭窄和扩张具有重要意义。
