Rahman Md Mostafizur, Prabhala Pavan, Rumzhum Nowshin N, Patel Brijeshkumar S, Wickop Thomas, Hansbro Philip M, Verrills Nicole M, Ammit Alaina J
Faculty of Pharmacy, University of Sydney, NSW, Australia.
Priority Research Centre for Respiratory Diseases, Hunter Medical Research Institute and The University of Newcastle, Newcastle, Australia.
Int J Biochem Cell Biol. 2016 Sep;78:279-287. doi: 10.1016/j.biocel.2016.07.030. Epub 2016 Jul 28.
Corticosteroids are effective anti-inflammatory therapies widely utilized in chronic respiratory diseases. But these medicines can lose their efficacy during respiratory infection resulting in disease exacerbation. Further in vitro research is required to understand how infection worsens lung function control in order to advance therapeutic options to treat infectious exacerbation in the future. In this study, we utilize a cellular model of bacterial exacerbation where we pretreat A549 lung epithelial cells with the synthetic bacterial lipoprotein Pam3CSK4 (a TLR2 ligand) to mimic bacterial infection and tumor necrosis factor α (TNFα) to simulate inflammation. Under these conditions, Pam3CSK4 induces corticosteroid insensitivity; demonstrated by substantially reduced ability of the corticosteroid dexamethasone to repress TNFα-induced interleukin 6 secretion. We then explored the molecular mechanism responsible and found that corticosteroid insensitivity induced by bacterial mimics was not due to altered translocation of the glucocorticoid receptor into the nucleus, nor an impact on the NF-κB pathway. Moreover, Pam3CSK4 did not affect corticosteroid-induced upregulation of anti-inflammatory MAPK deactivating phosphatase-MKP-1. However, Pam3CSK4 can induce oxidative stress and we show that a proportion of the MKP-1 produced in response to corticosteroid in the context of TLR2 ligation was rendered inactive by oxidation. Thus to combat inflammation in the context of bacterial exacerbation we sought to discover effective strategies that bypassed this road-block. We show for the first time that known (FTY720) and novel (theophylline) activators of the phosphatase PP2A can serve as non-steroidal anti-inflammatory alternatives and/or corticosteroid-sparing approaches in respiratory inflammation where corticosteroid insensitivity exists.
皮质类固醇是广泛应用于慢性呼吸道疾病的有效抗炎疗法。但这些药物在呼吸道感染期间可能会失去疗效，导致疾病加重。需要进一步的体外研究来了解感染如何恶化肺功能控制，以便未来推进治疗感染性加重的治疗选择。在本研究中，我们利用细菌加重的细胞模型，用合成细菌脂蛋白Pam3CSK4（一种TLR2配体）预处理A549肺上皮细胞以模拟细菌感染，并用肿瘤坏死因子α（TNFα）模拟炎症。在这些条件下，Pam3CSK4诱导皮质类固醇不敏感；皮质类固醇地塞米松抑制TNFα诱导的白细胞介素6分泌的能力大幅降低即证明了这一点。然后我们探索了其分子机制，发现细菌模拟物诱导的皮质类固醇不敏感不是由于糖皮质激素受体向细胞核的易位改变，也不是对NF-κB途径的影响。此外，Pam3CSK4不影响皮质类固醇诱导的抗炎丝裂原活化蛋白激酶失活磷酸酶-MKP-1的上调。然而，Pam3CSK4可诱导氧化应激，并且我们表明在TLR2连接的情况下，响应皮质类固醇产生的一部分MKP-1因氧化而失活。因此，为了对抗细菌加重情况下的炎症，我们试图发现绕过这一障碍的有效策略。我们首次表明，已知的（FTY720）和新型的（茶碱）磷酸酶PP2A激活剂可作为存在皮质类固醇不敏感的呼吸道炎症中的非甾体抗炎替代物和/或皮质类固醇节省方法。
