Abstract Context: Curcumin, the active component of Curcuma longa L. (Zingiberaceae), exhibits a wide variety of biological activities including vasodilation and anti-inflammation. Objective: The relaxant effect of curcumin in tracheal smooth muscle (TSM) was not examined so far, thus, this study was designed to assess the relaxant effect of curcumin on rat TSM and examine the underlying mechanism(s) responsible for this effect. Materials and methods: TSM was contracted by KCl (60 mM) or methacholine (10 μM), and cumulative concentrations of curcumin (12.5, 25, 50, and 100 mg/mL) or theophylline (0.2, 0.4, 0.6, and 0.8 mM, as positive control) were added to organ bath. The relaxant effect of curcumin was examined in non-incubated or incubated tissues with atropine (1 μM), chlorpheniramine (1 μM), indomethacin (1 μM), and papaverine (100 μM). Results: In non-incubated TSM, curcumin showed significant relaxant effects on KCl-induced contraction in a concentration-dependent manner (p < 0.001 for all concentrations). The relaxant effects of curcumin 12.5, 25, and 50 mg/mL were significantly lower in atropine-incubated tissue compared to non-incubated TSM (p < 0.05 to p < 0.001). A significant difference was observed in EC50 between atropine-incubated (48.10 ± 2.55) and non-incubated (41.65 ± 1.81) tissues (p < 0.05). Theophylline showed a significant relaxant effect on both KCl and methacholine-induced contraction in a concentration-dependent manner (p < 0.001 for all cases). Conclusions: The results indicated a relatively potent relaxant effect of curcumin on TSM, which was less marked than the effect of theophylline. Calcium channel blocking and/or potassium channel opening properties of curcumin may be responsible for TSM relaxation.

中文翻译：

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钙和钾通道参与姜黄素对气管平滑肌的松弛作用

摘要背景：姜黄素是姜黄科（姜科）的活性成分，具有广泛的生物活性，包括血管舒张和抗炎。目的：姜黄素对气管平滑肌 (TSM) 的松弛作用目前尚未研究，因此，本研究旨在评估姜黄素对大鼠 TSM 的松弛作用，并研究导致这种作用的潜在机制。材料和方法：TSM 被 KCl (60 mM) 或乙酰甲胆碱 (10 μM) 以及累积浓度的姜黄素（12.5、25、50 和 100 mg/mL）或茶碱（0.2、0.4、0.6 和 0.8 mM）收缩，作为阳性对照）被添加到器官浴。在含有阿托品 (1 μM)、扑尔敏 (1 μM)、吲哚美辛 (1 μM) 和罂粟碱 (100 μM) 的非孵育或孵育组织中检查姜黄素的松弛作用。结果：在未孵育的 TSM 中，姜黄素以浓度依赖性方式对 KCl 诱导的收缩显示出显着的松弛作用（所有浓度的 p < 0.001）。与未孵育的 TSM 相比，姜黄素 12.5、25 和 50 毫克/毫升的松弛作用在阿托品孵育的组织中显着降低（p < 0.05 至 p < 0.001）。阿托品孵育 (48.10 ± 2.55) 和非孵育 (41.65 ± 1.81) 组织之间的 EC50 存在显着差异 (p < 0.05)。茶碱以浓度依赖性方式对 KCl 和乙酰甲胆碱诱导的收缩显示出显着的松弛作用（对于所有情况，p < 0.001）。结论：结果表明姜黄素对 TSM 具有相对强效的松弛作用，其作用不如茶碱显着。