Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
Am J Physiol Lung Cell Mol Physiol. 2011 Oct;301(4):L607-14. doi: 10.1152/ajplung.00019.2011. Epub 2011 Jul 29.
Diseases such as asthma are characterized by airway hyperresponsiveness. Enhanced airway smooth muscle (ASM) intracellular Ca(2+) (Ca(2+)) response to agonist stimulation leading to increased airway constriction has been suggested to contribute to airway hyperresponsiveness. Caveolae are flask-shaped plasma membrane invaginations that express the scaffolding protein caveolin and contain multiple proteins important in Ca(2+) signaling (e.g., agonist receptors, ion channels). We recently demonstrated that caveolae and caveolin-1 are important in Ca(2+) regulation in human ASM. Proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-13 modulate Ca(2+) in ASM. We hypothesized that cytokine upregulation of caveolar signaling in ASM contributes to enhanced agonist-induced Ca(2+) in inflammation. Enzymatically dissociated human ASM cells were exposed to medium (control), 20 ng/ml TNF-α, or 50 ng/ml IL-13 for 24 h. Caveolae-enriched membrane fractions displayed substantial increase in caveolin-1 and -2 expressions by TNF-α and IL-13. Transfection with caveolin-1-mRed DNA substantially accelerated and increased plasma membrane caveolin-1 expression by TNF-α and to a lesser extent by IL-13. Caveolin-1 enhancement was inhibited by nuclear factor-κB and mitogen-activated protein kinase inhibitors. In fura 2-loaded ASM cells, Ca(2+) responses to 1 μM ACh, 10 μM histamine, or 10 nM bradykinin were all exaggerated by TNF-α as well as IL-13 exposure. However, disruption of caveolae using caveolin-1 suppression via small-interfering RNA resulted in significant blunting of agonist-induced Ca(2+) responses of vehicle and TNF-α-exposed cells. These functional data were correlated to the presence of TNFR(1) receptor (but not the IL-4/IL-13 receptor) within caveolae. Overall, these results indicate that caveolin-1 plays an important role in airway inflammation by modulating the effect of specific cytokines on Ca(2+).
哮喘等疾病的特征是气道高反应性。已有人提出，气道平滑肌（ASM）细胞内钙（[Ca2+]）对激动剂刺激的反应增强，导致气道收缩增加，这可能导致气道高反应性。小窝是一种烧瓶状的质膜内陷，表达支架蛋白 caveolin，并且含有多种在 [Ca2+] 信号传导中重要的蛋白（例如激动剂受体、离子通道）。我们最近证明，小窝和 caveolin-1 在人类 ASM 的 [Ca2+] 调节中很重要。炎性细胞因子，如肿瘤坏死因子（TNF）-α和白细胞介素（IL）-13，调节 ASM 中的 [Ca2+]。我们假设，细胞因子上调 ASM 中的小窝信号，导致炎症中增强的激动剂诱导的 [Ca2+]。用酶消化分离的人 ASM 细胞，分别暴露于培养基（对照）、20 ng/ml TNF-α或 50 ng/ml IL-13 24 小时。TNF-α和 IL-13 使小窝富含膜部分的 caveolin-1 和 -2 表达明显增加。用 caveolin-1-mRed DNA 转染可显著加速 TNF-α和 IL-13 引起的质膜 caveolin-1 表达。核因子-κB 和丝裂原活化蛋白激酶抑制剂抑制 caveolin-1 的增强。在用 fura 2 负载的 ASM 细胞中，1 μM ACh、10 μM 组胺或 10 nM 缓激肽的 [Ca2+] 反应均被 TNF-α和 IL-13 暴露所夸大。然而，通过小干扰 RNA 抑制 caveolin-1 破坏小窝，可显著减弱载体和 TNF-α暴露细胞的激动剂诱导的 [Ca2+] 反应。这些功能数据与小窝内 TNFR（1）受体（而不是 IL-4/IL-13 受体）的存在相关。总体而言，这些结果表明 caveolin-1 通过调节特定细胞因子对 [Ca2+] 的影响，在气道炎症中发挥重要作用。
