title: TLR2 ligation induces corticosteroid insensitivity in A549 lung epithelial cells: Anti-inflammatory impact of PP2A activators.
abstract: 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.
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Md Mostafizur
authors.initials: MM
authors.lastname: Rahman
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Pavan
authors.initials: P
authors.lastname: Prabhala
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Nowshin N
authors.initials: NN
authors.lastname: Rumzhum
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Brijeshkumar S
authors.initials: BS
authors.lastname: Patel
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wickop
authors.affiliation: Priority Research Centre for Respiratory Diseases, Hunter Medical Research Institute and The University of Newcastle, Newcastle, Australia.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Hansbro
authors.affiliation: School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, NSW, Australia.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Verrills
authors.affiliation: Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, NSW, Australia; School of Life Sciences, Faculty of Science, University of Technology Sydney, NSW, Australia. Electronic address: Alaina.Ammit@uts.edu.au.
authors.forename: Alaina J
authors.initials: AJ
authors.lastname: Ammit
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002460:Cell Line; D004351:Drug Resistance / Q000187:drug effects*; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008024:Ligands; D055666:Lipopeptides / Q000378:metabolism / Q000494:pharmacology*; D008168:Lung / Q000166:cytology*; D010084:Oxidation-Reduction / Q000187:drug effects; D011485:Protein Binding; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000305:Adrenal Cortex Hormones; D000893:Anti-Inflammatory Agents; D008024:Ligands; D055666:Lipopeptides; C508075:Pam(3)CSK(4) peptide; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D054648:Protein Phosphatase 2; D054638:Dual Specificity Phosphatase 1
keywords: Corticosteroid insensitivity; MKP-1; PP2A; TLR2