Melatonin MT2 receptor is expressed and potentiates contraction in human airway smooth muscle.
Melatonin MT2 receptor is expressed and potentiates contraction in human airway smooth muscle.
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褪黑素MT2受体在人气道平滑肌中表达并增强收缩。
DOI：
10.1152/ajplung.00273.2021
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
Haruka Sasaki;Yi Zhang;C. Emala;K. Mizuta
中科院分区：
文献类型：
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作者：
Haruka Sasaki;Yi Zhang;C. Emala;K. Mizuta
夜间哮喘的特点是夜间支气管反应性升高，有夜间哮喘症状的患者血浆褪黑激素浓度较高。褪黑激素的许多生理作用是通过其特定的 G 蛋白偶联受体 (GPCR) 介导的，该受体称为 MT1 受体，可与 Gq 和 Gi 蛋白偶联，以及 MT2 受体，可与 Gi 偶联。我们研究了褪黑激素受体是否在气道平滑肌上表达，它们是否调节细胞内环磷酸腺苷（cAMP）和调节气道平滑肌张力的钙浓度（[Ca2+]i），以及它们是否促进气道平滑肌细胞增殖。我们通过 RT-PCR、免疫印迹和免疫组织化学检测了天然人和豚鼠气道平滑肌和培养的人气道平滑肌 (HASM) 细胞中褪黑激素 MT2 的 mRNA 和蛋白表达，但未检测到 MT1 受体的 mRNA 和蛋白表达。用药理学浓度的褪黑激素 (10 - 100 µM) 或非选择性 MT1/MT2 激动剂雷美替胺 (10 µM) 激活褪黑激素 MT2 受体，可显着抑制毛喉素刺激的 HASM 细胞中 cAMP 的积累，而 Gαi 蛋白抑制剂百日咳毒素或其特异性 siRNA 敲低 MT2 受体可逆转这一现象。虽然褪黑激素本身不会诱导初始 [Ca2+]i 增加和气道收缩，但褪黑激素显着增强乙酰胆碱刺激的 [Ca2+]i 增加，通过 HASM 细胞中的 MT2 受体应激纤维形成，并减弱异丙肾上腺素在豚鼠气管中的松弛作用。这些发现表明褪黑激素 MT2 受体在 ASM 中表达，并通过减少 cAMP 产生和增加 [Ca2+]i 来调节气道平滑肌张力。
Nocturnal asthma is characterized by heightened bronchial reactivity at night, and plasma melatonin concentrations are higher in patients with nocturnal asthma symptoms. Numerous physiological effects of melatonin are mediated via its specific G protein-coupled receptors (GPCRs) named the MT1 receptor which couples to both Gq and Gi proteins, and the MT2 receptor which couples to Gi. We investigated whether melatonin receptors are expressed on airway smooth muscle, whether they regulate intracellular cyclic AMP (cAMP) and calcium concentrations ([Ca2+]i) which modulate airway smooth muscle tone, and whether they promote airway smooth muscle cell proliferation. We detected the mRNA and protein expression of the melatonin MT2 but not the MT1 receptor in native human and guinea pig airway smooth muscle and cultured human airway smooth muscle (HASM) cells by RT-PCR, immunoblotting, and immunohistochemistry. Activation of melatonin MT2 receptors with either pharmacological concentrations of melatonin (10 - 100 µM) or the non-selective MT1/MT2 agonist ramelteon (10 µM) significantly inhibited forskolin-stimulated cAMP accumulation in HASM cells, which was reversed by the Gαi protein inhibitor pertussis toxin or knockdown of the MT2 receptor by its specific siRNA. Although melatonin by itself did not induce an initial [Ca2+]i increase and airway contraction, melatonin significantly potentiated acetylcholine-stimulated [Ca2+]i increases, stress fiber formation through the MT2 receptor in HASM cells, and attenuated the relaxant effect of isoproterenol in guinea pig trachea. These findings suggest that the melatonin MT2 receptor is expressed in ASM, and modulates airway smooth muscle tone via reduced cAMP production and increased [Ca2+]i.