Department of Physiology, University of Manitoba, Winnipeg, MB, Canada.
Br J Pharmacol. 2012 Oct;167(3):548-60. doi: 10.1111/j.1476-5381.2012.02014.x.
Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.
Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.
Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A₂ inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD₄ receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.
The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.
急性沉默小窝蛋白-1（Cav-1）可调节气道平滑肌的受体介导收缩。此外，环氧合酶-2（COX-2）和 5-脂氧合酶（5-LO）衍生的前列腺素和白三烯生物合成可以影响平滑肌反应性。COX-2 的半衰期可以通过与 Cav-1 的结合而延长。我们假设，当环氧合酶-2 抑制导致花生四烯酸信号传导紊乱时，由于缺乏 Cav-1 调节 COX-2 的水平，进而调节气管收缩。
使用 Cav-1 敲除（KO）和野生型（B6129SF2/J）小鼠的气管环，测量其对乙酰甲胆碱的等长收缩，并使用 PCR、免疫印迹和免疫组织化学监测相关蛋白的表达。
Cav-1 KO 和野生型小鼠的气管环表现出相似的反应，但 COX-2 抑制剂吲哚美辛增加了 Cav-1 KO 小鼠气管环对乙酰甲胆碱的反应。磷脂酶 A₂抑制剂花生四烯酸，可抑制 COX-2 和 5-LO 代谢物的形成，对野生型或 Cav-1 KO 组织没有影响。LTD₄ 受体拮抗剂（孟鲁司特）和 5-LO 抑制剂（齐留通）消除了吲哚美辛介导的超反应性。上皮细胞剥脱阻断了吲哚美辛对 Cav-1 KO 对乙酰甲胆碱反应的增强作用。免疫沉淀显示 COX-2 在野生型肺中与 Cav-1 结合。免疫印迹和 qPCR 显示 Cav-1 KO 气管中 COX-2 和 5-LO 蛋白水平升高，但 COX-1 蛋白水平不升高，上皮细胞去除可预防这种情况。
在 Cav-1 KO 气管中观察到的吲哚美辛诱导的超收缩性与 COX-2 和 5-LO 表达增加有关，当 COX-2 被抑制时，这可能增强了花生四烯酸的分流和产生促收缩性白三烯。
