Ito Satoru, Kume Hiroaki, Naruse Keiji, Kondo Masashi, Takeda Naoya, Iwata Susumu, Hasegawa Yoshinori, Sokabe Masahiro
Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Am J Respir Cell Mol Biol. 2008 Apr;38(4):407-13. doi: 10.1165/rcmb.2007-0259OC. Epub 2007 Nov 1.
In response to mechanical stretch, airway smooth muscle exhibits various cellular functions such as contraction, proliferation, and cytoskeletal remodeling, all of which are implicated in the pathophysiology of asthma. We tested the hypothesis that mechanical stretch of airway smooth muscle cells increases intracellular Ca(2+) concentration (Ca(2+)) by activating stretch-activated (SA) nonselective cation channels. A single uniaxial stretch (3 s) was given to human bronchial smooth muscle cells cultured on an elastic silicone membrane. After the mechanical stretch, a transient increase in Ca(2+) was observed. The Ca(2+) increase was significantly dependent on stretch amplitude. The augmented Ca(2+) due to stretch was completely abolished by removal of extracellular Ca(2+) and was markedly attenuated by an application of Gd(3+), an inhibitor of SA channels, or ruthenium red, a transient receptor potential vanilloid (TRPV) inhibitor. In contrast, the stretch-induced rises of Ca(2+) were not altered by other Ca(2+) channel inhibitors such as nifedipine, BTP-2, and SKF-96365. Moreover, the Ca(2+) increases were not affected by indomethacin, a cyclooxygenase inhibitor, U-73122, a phospholipase C inhibitor, or xestospongin C, an inhibitor of the inositol-trisphosphate receptor. These findings demonstrate that a novel Ca(2+) influx pathway activated by mechanical stretch, possibly through the Ca(2+)-permeable SA channel activated directly by stretch rather than by indirect mechanisms via intracellular messenger production, is involved in human airway smooth muscle cells. A molecular candidate for the putative SA channel may be one of the members of the TRPV channel family. Thus, abnormal Ca(2+) homeostasis in response to excessive mechanical strain would contribute to the pathogenesis of asthma.
作为对机械牵张的反应,气道平滑肌会展现出多种细胞功能,如收缩、增殖和细胞骨架重塑,所有这些都与哮喘的病理生理学有关。我们检验了这样一个假设,即气道平滑肌细胞的机械牵张通过激活牵张激活(SA)非选择性阳离子通道来增加细胞内钙离子浓度(Ca(2+))。对培养在弹性硅酮膜上的人支气管平滑肌细胞施加单次单轴牵张(3秒)。机械牵张后,观察到Ca(2+)出现短暂升高。Ca(2+)的升高显著依赖于牵张幅度。去除细胞外钙离子可完全消除因牵张导致的Ca(2+)升高,而施加SA通道抑制剂钆(Gd(3+))或瞬时受体电位香草酸亚型(TRPV)抑制剂钌红可显著减弱这种升高。相比之下,其他钙离子通道抑制剂,如硝苯地平、BTP - 2和SKF - 96365,并不会改变牵张诱导的Ca(2+)升高。此外,Ca(2+)的升高不受环氧化酶抑制剂吲哚美辛、磷脂酶C抑制剂U - 73122或肌醇三磷酸受体抑制剂西司他汀C的影响。这些发现表明,一种由机械牵张激活的新型钙离子内流途径参与了人气道平滑肌细胞,该途径可能是通过由牵张直接激活的钙离子通透SA通道,而非经由细胞内信使产生的间接机制。推测的SA通道的分子候选者可能是TRPV通道家族的成员之一。因此,对过度机械应变的异常钙离子稳态反应可能会导致哮喘的发病机制。