Ammit A J, Armour C L, Black J L
Respiratory Research Group, Department of Pharmacy, University of Sydney, Sydney, Australia.
Am J Respir Crit Care Med. 2000 Jan;161(1):257-63. doi: 10.1164/ajrccm.161.1.9901005.
We have previously reported that contractile reactivity of human airway preparations in vitro depends on sensitization status. The aim of this study was to examine whether this could be associated with differences in the content and/or expression pattern of myosin light-chain kinase (MLCK) isoforms in airway smooth muscle (ASM). Macroscopically normal lung tissue was obtained from subjects undergoing lung transplantation, and smooth-muscle bundles were dissected from nonsensitized (n = 5) and sensitized (n = 5) bronchi. MLCK isoform expression was then assessed by immunoblotting. The major MLCK isoform in ASM was smooth-muscle MLCK (smMLCK; 136 kD). Nonmuscle MLCK isoforms (nmMLCK; 210 to 220 kD) were not present. The smMLCK content was significantly higher in ASM from sensitized bronchi (p = 0.049) than in ASM from nonsensitized tissue (11.9 +/- 3.3 versus 4.1 +/- 0.7 arbitrary units [a.u.] smMLCK/mg ASM, respectively). In contrast, there was no significant difference (p = 0.636) in the content of myosin heavy chain (MHC) in tissue collected from sensitized and nonsensitized bronchi (1.33 +/- 0.33 versus 1.09 +/- 0.37 microg MHC/mg ASM, respectively). This study is the first to examine MLCK isoforms in human ASM, and suggests that increased smMLCK content may be one of the mechanisms responsible for enhanced contractile reactivity in sensitized tissue.
我们之前曾报道，人呼吸道制剂的体外收缩反应性取决于致敏状态。本研究的目的是检验这是否与气道平滑肌（ASM）中肌球蛋白轻链激酶（MLCK）亚型的含量和/或表达模式差异有关。从接受肺移植的受试者获取宏观正常的肺组织，并从未致敏（n = 5）和致敏（n = 5）的支气管中解剖出平滑肌束。然后通过免疫印迹法评估MLCK亚型的表达。ASM中的主要MLCK亚型是平滑肌MLCK（smMLCK；136 kD）。不存在非肌肉MLCK亚型（nmMLCK；210至220 kD）。致敏支气管的ASM中smMLCK含量显著高于未致敏组织的ASM（p = 0.049）（分别为11.9±3.3与4.1±0.7任意单位[a.u.] smMLCK/mg ASM）。相比之下，从致敏和未致敏支气管收集的组织中肌球蛋白重链（MHC）含量无显著差异（p = 0.636）（分别为1.33±0.33与1.09±0.37 μg MHC/mg ASM）。本研究首次检测人ASM中的MLCK亚型，并表明smMLCK含量增加可能是致敏组织中收缩反应性增强的机制之一。
