Patel Brijeshkumar S, Rahman Md Mostafizur, Rumzhum Nowshin N, Oliver Brian G, Verrills Nicole M, Ammit Alaina J
1 Faculty of Pharmacy, University of Sydney, New South Wales, Australia.
2 Woolcock Institute of Medical Research, University of Sydney, New South Wales, Australia.
Am J Respir Cell Mol Biol. 2016 Jun;54(6):792-801. doi: 10.1165/rcmb.2015-0308OC.
Theophylline is an old drug experiencing a renaissance owing to its beneficial antiinflammatory effects in chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease. Multiple modes of antiinflammatory action have been reported, including inhibition of the enzymes that degrade cAMP-phosphodiesterase (PDE). Using primary cultures of airway smooth muscle (ASM) cells, we recently revealed that PDE4 inhibitors can potentiate the antiinflammatory action of β2-agonists by augmenting cAMP-dependent expression of the phosphatase that deactivates mitogen-activated protein kinase (MAPK)-MAPK phosphatase (MKP)-1. Therefore, the aim of this study was to address whether theophylline repressed cytokine production in a similar, PDE-dependent, MKP-1-mediated manner. Notably, theophylline did not potentiate cAMP release from ASM cells treated with the long-acting β2-agonist formoterol. Moreover, theophylline (0.1-10 μM) did not increase formoterol-induced MKP-1 messenger RNA expression nor protein up-regulation, consistent with the lack of cAMP generation. However, theophylline (at 10 μM) was antiinflammatory and repressed secretion of the neutrophil chemoattractant cytokine IL-8, which is produced in response to TNF-α. Because theophylline's effects were independent of PDE4 inhibition or antiinflammatory MKP-1, we then wished to elucidate the novel mechanisms responsible. We investigated the impact of theophylline on protein phosphatase (PP) 2A, a master controller of multiple inflammatory signaling pathways, and show that theophylline increases TNF-α-induced PP2A activity in ASM cells. Confirmatory results were obtained in A549 lung epithelial cells. PP2A activators have beneficial effects in ex vivo and in vivo models of respiratory disease. Thus, our study is the first to link theophylline with PP2A activation as a novel mechanism to control respiratory inflammation.
由于其在慢性呼吸道疾病（如哮喘和慢性阻塞性肺疾病）中具有有益的抗炎作用，茶碱这种老药正在经历复兴。已报道了多种抗炎作用模式，包括抑制降解环磷酸腺苷（cAMP）的磷酸二酯酶（PDE）的酶。我们最近利用气道平滑肌（ASM）细胞的原代培养物发现，PDE4抑制剂可通过增强使丝裂原活化蛋白激酶（MAPK）失活的磷酸酶——MAPK磷酸酶（MKP）-1的cAMP依赖性表达来增强β2-激动剂的抗炎作用。因此，本研究的目的是探讨茶碱是否以类似的、依赖PDE的、MKP-1介导的方式抑制细胞因子产生。值得注意的是，茶碱并不能增强用长效β2-激动剂福莫特罗处理的ASM细胞的cAMP释放。此外，茶碱（0.1 - 10 μM）既没有增加福莫特罗诱导的MKP-1信使核糖核酸表达，也没有增加蛋白质上调，这与cAMP生成的缺乏一致。然而，茶碱（10 μM）具有抗炎作用，并抑制了中性粒细胞趋化因子细胞因子白细胞介素8（IL-8）的分泌，IL-8是对肿瘤坏死因子-α（TNF-α）作出反应而产生的。由于茶碱的作用独立于PDE4抑制或抗炎性MKP-1，我们随后希望阐明其背后的新机制。我们研究了茶碱对蛋白磷酸酶（PP）2A的影响，PP2A是多种炎症信号通路的主要调控因子，并表明茶碱可增加ASM细胞中TNF-α诱导的PP2A活性。在A549肺上皮细胞中获得了证实性结果。PP2A激活剂在呼吸道疾病的体外和体内模型中具有有益作用。因此，我们的研究首次将茶碱与PP2A激活联系起来，作为控制呼吸道炎症的一种新机制。
