Reza Mohammad Irshad, Kumar Ashish, Pabelick Christina M, Britt Rodney D, Prakash Y S, Sathish Venkatachalem
Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States.
Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States.
Am J Physiol Lung Cell Mol Physiol. 2024 May 1;326(5):L651-L659. doi: 10.1152/ajplung.00050.2024. Epub 2024 Mar 26.
Airway smooth muscle cell (ASM) is renowned for its involvement in airway hyperresponsiveness through impaired ASM relaxation and bronchoconstriction in asthma, which poses a significant challenge in the field. Recent studies have explored different targets in ASM to alleviate airway hyperresponsiveness, however, a sizeable portion of patients with asthma still experience poor control. In our study, we explored protein phosphatase 2 A (PP2A) in ASM as it has been reported to regulate cellular contractility by controlling intracellular calcium ([Ca]), ion channels, and respective regulatory proteins. We obtained human ASM cells and lung tissues from healthy and patients with asthma and evaluated PP2A expression using RNA-Seq data, immunofluorescence, and immunoblotting. We further investigated the functional importance of PP2A by determining its role in bronchoconstriction using mouse bronchus and human ASM cell [Ca] regulation. We found robust expression of PP2A isoforms in human ASM cells with PP2Aα being highly expressed. Interestingly, PP2Aα was significantly downregulated in asthmatic tissue and human ASM cells exposed to proinflammatory cytokines. Functionally, FTY720 (PP2A agonist) inhibited acetylcholine- or methacholine-induced bronchial contraction in mouse bronchus and further potentiated isoproterenol-induced bronchial relaxation. Mechanistically, FTY720 inhibited histamine-evoked [Ca] response and myosin light chain (MLC) phosphorylation in the presence of interleukin-13 (IL-13) in human ASM cells. To conclude, we for the first time established PP2A signaling in ASM, which can be further explored to develop novel therapeutics to alleviate airway hyperresponsiveness in asthma. This novel study deciphered the expression and function of protein phosphatase 2Aα (PP2Aα) in airway smooth muscle (ASM) during asthma and/or inflammation. We showed robust expression of PP2Aα in human ASM while its downregulation in asthmatic ASM. Similarly, we demonstrated reduced PP2Aα expression in ASM exposed to proinflammatory cytokines. PP2Aα activation inhibited bronchoconstriction of isolated mouse bronchi. In addition, we unveiled that PP2Aα activation inhibits the intracellular calcium release and myosin light chain phosphorylation in human ASM.
气道平滑肌细胞（ASM）因在哮喘中通过受损的ASM舒张和支气管收缩参与气道高反应性而闻名，这在该领域构成了重大挑战。最近的研究探索了ASM中的不同靶点以减轻气道高反应性，然而，相当一部分哮喘患者的病情仍控制不佳。在我们的研究中，我们探索了ASM中的蛋白磷酸酶2A（PP2A），因为据报道它通过控制细胞内钙（[Ca]）、离子通道和各自的调节蛋白来调节细胞收缩性。我们从健康人和哮喘患者中获取了人ASM细胞和肺组织，并使用RNA测序数据、免疫荧光和免疫印迹评估了PP2A的表达。我们通过使用小鼠支气管和人ASM细胞[Ca]调节来确定其在支气管收缩中的作用，进一步研究了PP2A的功能重要性。我们发现PP2A亚型在人ASM细胞中大量表达，其中PP2Aα高度表达。有趣的是，在哮喘组织和暴露于促炎细胞因子的人ASM细胞中，PP2Aα显著下调。在功能上，FTY720（PP2A激动剂）抑制小鼠支气管中乙酰胆碱或乙酰甲胆碱诱导的支气管收缩，并进一步增强异丙肾上腺素诱导的支气管舒张。从机制上讲，FTY720在人ASM细胞中抑制白细胞介素-13（IL-13）存在时组胺诱发的[Ca]反应和肌球蛋白轻链（MLC）磷酸化。总之，我们首次在ASM中建立了PP2A信号通路，该通路可进一步探索以开发新的疗法来减轻哮喘中的气道高反应性。这项新研究解读了哮喘和/或炎症期间气道平滑肌（ASM）中蛋白磷酸酶2Aα（PP2Aα）的表达和功能。我们显示PP2Aα在人ASM中大量表达，而在哮喘ASM中其表达下调。同样，我们证明暴露于促炎细胞因子的ASM中PP2Aα表达降低。PP2Aα激活抑制离体小鼠支气管的支气管收缩。此外，我们揭示PP2Aα激活抑制人ASM中的细胞内钙释放和肌球蛋白轻链磷酸化。
