Abstract：
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 ([Ca2+]i), 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 [Ca2+]i 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 [Ca2+]i 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.NEW & NOTEWORTHY 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.
摘要：
气道平滑肌细胞（ASM）因其在哮喘中通过受损的ASM松弛和支气管收缩而参与气道高反应性而闻名，这在该领域构成了重大挑战。最近的研究已经探索了ASM中减轻气道高反应性的不同靶标，然而,相当一部分哮喘患者仍然控制不佳。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（[Ca2]i）来调节细胞收缩性，离子通道,和各自的调节蛋白。我们从健康和哮喘患者中获得了人ASM细胞和肺组织，并使用RNASeq数据评估了PP2A的表达，免疫荧光，和免疫印迹。我们通过使用小鼠支气管和人ASM[Ca2]i调节确定PP2A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中普遍存在，PP2Aα主要表达。有趣的是,PP2Aα在暴露于促炎细胞因子的哮喘组织和人ASM中显著下调。功能上,PP2Aα激活抑制乙酰胆碱或乙酰甲胆碱诱导的小鼠支气管支气管收缩，并进一步增强异丙肾上腺素诱导的支气管舒张。机械上,在人ASM细胞中存在白介素13（IL-13）的情况下，PP2Aα激活抑制了组胺引起的[Ca2]i反应和肌球蛋白轻链（MLC）磷酸化。最后，我们首次建立了ASM中的PP2A信号传导机制,可进一步探索该机制,以开发减轻哮喘气道高反应性的新疗法.
