Conaway Stanley, Richard Joshua, Deshpande Deepak A
Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States.
Am J Physiol Lung Cell Mol Physiol. 2025 Jul 1;329(1):L70-L83. doi: 10.1152/ajplung.00058.2025. Epub 2025 May 28.
Intracellular calcium (Ca) release via phospholipase C (PLC) following G-protein-coupled receptor (GPCR) activation is typically linked to membrane depolarization and airway smooth muscle (ASM) contraction. However, recent findings show that bitter taste receptor agonists, such as chloroquine (CQ), induce a paradoxical and potent relaxation response despite activating the Ca signaling pathway. This relaxation has been hypothesized to be driven by a distinct compartmentalization of calcium ions toward the cellular periphery, subsequently leading to membrane hyperpolarization, in contrast to the contractile effects of histamine. In this study, we further investigate the spatiotemporal dynamics of Ca signaling in ASM cells using single-cell microscopy and deep learning-based segmentation, integrating the results into a comprehensive model of ASM ion channel dynamics to compare the effects of histamine, CQ, and flufenamic acid (FFA). Our results show that histamine induces a strong, synchronized calcium release, nearly twice as high as that of CQ, which produces a sustained but lower-magnitude response. Per-cell analysis reveals more variable and asynchronous Ca signaling for CQ and FFA, with higher entropy compared with histamine. Integrating these findings into an ASM ion channel model, we observed that histamine-mediated Ca release activates voltage-gated Ca and Na channels (leading to depolarization). In contrast, CQ preferentially engages BKCa, SKCa, and chloride channels (promoting hyperpolarization). These findings provide insights into the unique mechanisms by which bitter taste receptor agonists can modulate ASM tone, offering potential therapeutic strategies for relaxing ASM and alleviating airway hyperresponsiveness in conditions such as asthma. Using machine-learning methods, these studies identify spatiotemporal differences in calcium responses between agonists of Gq-coupled receptors and bitter taste receptors in airway smooth muscle cells. The findings provide deeper insights into the mechanism of action of bitter tastant-induced airway smooth muscle relaxation.
G蛋白偶联受体（GPCR）激活后，通过磷脂酶C（PLC）介导的细胞内钙（Ca）释放通常与膜去极化和气道平滑肌（ASM）收缩相关。然而，最近的研究发现，苦味受体激动剂，如氯喹（CQ），尽管激活了Ca信号通路，但却能引发矛盾而强烈的舒张反应。据推测，这种舒张是由钙离子向细胞周边的独特区室化驱动的，随后导致膜超极化，这与组胺的收缩作用相反。在本研究中，我们使用单细胞显微镜和基于深度学习的分割技术，进一步研究ASM细胞中Ca信号的时空动态，并将结果整合到ASM离子通道动力学的综合模型中，以比较组胺、CQ和氟芬那酸（FFA）的作用效果。我们的结果表明，组胺诱导强烈的、同步的钙释放，其释放量几乎是CQ的两倍，CQ产生的是持续但幅度较小的反应。单细胞分析显示，CQ和FFA的钙信号更具变异性和异步性，与组胺相比具有更高的熵。将这些发现整合到ASM离子通道模型中，我们观察到组胺介导的钙释放激活电压门控Ca和Na通道（导致去极化）。相比之下，CQ优先作用于大电导钙激活钾通道（BKCa）、小电导钙激活钾通道（SKCa）和氯通道（促进超极化）。这些发现为苦味受体激动剂调节ASM张力的独特机制提供了见解，为舒张ASM和缓解哮喘等疾病中的气道高反应性提供了潜在的治疗策略。通过机器学习方法，这些研究确定了Gq偶联受体激动剂和苦味受体在气道平滑肌细胞中钙反应的时空差异。这些发现为苦味剂诱导气道平滑肌舒张的作用机制提供了更深入的见解。
