Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
Am J Physiol Lung Cell Mol Physiol. 2012 Oct 15;303(8):L711-9. doi: 10.1152/ajplung.00037.2012. Epub 2012 Aug 24.
Maintenance of blood oxygen saturation dictates supplemental oxygen administration to premature infants, but hyperoxia predisposes survivors to respiratory diseases such as asthma. Although much research has focused on oxygen effects on alveoli in the setting of bronchopulmonary dysplasia, the mechanisms by which oxygen affects airway structure or function relevant to asthma are still under investigation. We used isolated human fetal airway smooth muscle (fASM) cells from 18-20 postconceptual age lungs (canalicular stage) to examine oxygen effects on intracellular Ca(2+) (Ca(2+)) and cellular proliferation. fASM cells expressed substantial smooth muscle actin and myosin and several Ca(2+) regulatory proteins but not fibroblast or epithelial markers, profiles qualitatively comparable to adult human ASM. Fluorescence Ca(2+) imaging showed robust Ca(2+) responses to 1 μM acetylcholine (ACh) and 10 μM histamine (albeit smaller and slower than adult ASM), partly sensitive to zero extracellular Ca(2+). Compared with adult, fASM showed greater baseline proliferation. Based on this validation, we assessed fASM responses to 10% hypoxia through 90% hyperoxia and found enhanced proliferation at <60% oxygen but increased apoptosis at >60%, effects accompanied by appropriate changes in proliferative vs. apoptotic markers and enhanced mitochondrial fission at >60% oxygen. Ca(2+) responses to ACh were enhanced for <60% but blunted at >60% oxygen. These results suggest that hyperoxia has dose-dependent effects on structure and function of developing ASM, which could have consequences for airway diseases of childhood. Thus detrimental effects on ASM should be an additional consideration in assessing risks of supplemental oxygen in prematurity.
维持血氧饱和度需要给早产儿补充氧气，但高氧会使幸存者易患哮喘等呼吸道疾病。虽然大量研究集中在支气管肺发育不良背景下氧气对肺泡的影响，但氧气影响与哮喘相关的气道结构或功能的机制仍在研究中。我们使用来自 18-20 孕周（小管期）肺的分离的人胎儿气道平滑肌（fASM）细胞，研究了氧气对细胞内 Ca(2+)(Ca(2+))和细胞增殖的影响。fASM 细胞表达大量的平滑肌肌动蛋白和肌球蛋白以及几种 Ca(2+)调节蛋白，但不表达成纤维细胞或上皮细胞标志物，其表型与成人气道平滑肌相当。荧光 Ca(2+)成像显示，1 μM 乙酰胆碱（ACh）和 10 μM 组胺引起强烈的 Ca(2+)反应（尽管比成人气道平滑肌小且慢），部分对零细胞外 Ca(2+)敏感。与成人相比，fASM 显示出更高的基础增殖率。基于这一验证，我们评估了 fASM 对 10%低氧通过 90%高氧的反应，发现 <60%氧气时增殖增加，但 >60%氧气时凋亡增加，这些效应伴随着增殖与凋亡标志物的适当变化，以及 >60%氧气时线粒体分裂增加。ACh 引起的 Ca(2+)反应在 <60%氧气时增强，但在 >60%氧气时减弱。这些结果表明，高氧对发育中的气道平滑肌的结构和功能具有剂量依赖性的影响，这可能对儿童期的气道疾病产生影响。因此，在评估早产儿补充氧气的风险时，应将对气道平滑肌的不利影响作为额外的考虑因素。
