Minocycline blocks asthma-associated inflammation in part by interfering with the t cell receptor-nuclear factorkB-GATA-3-IL-4 axis without a prominent effect on poly(ADP-ribose) polymerase

Abstract

Background: Minocycline protects against asthma independently of its antibiotic function. Results: Minocycline blocks asthma-associated traits, including IgE production, by modulating the TCR-NF-B-GATA-3-IL-4 axis but not the TCR/NFAT1/IL-2 pathway without a direct effect on PARP activity. Conclusion: These results provide new insight into the mechanism of action of minocycline. Significance: These results provide further support to the therapeutic potential of minocycline in reducing or preventing allergen-induced asthma symptoms. Minocycline protects against asthma independently of its antibiotic function and was recently reported as a potent poly-(ADP-ribose) polymerase (PARP) inhibitor. In an animal model of asthma, a single administration of minocycline conferred excellent protection against ovalbumin-induced airway eosinophilia, mucus hypersecretion, and Th2 cytokine production (IL-4/IL-5/IL-12(p70)/IL-13/ GM-CSF) and a partial protection against airway hyperresponsiveness. These effects correlated with pronounced reduction in lung and sera allergen-specific IgE. A reduction in poly(ADP-ribose) immunoreactivity in the lungs of minocycline-treated/ovalbumin-challenged mice correlated with decreased oxidative DNA damage. The effect of minocycline on PARP may be indirect, as the drug failed to efficiently block direct PARP activation in lungs of N-methyl-N-nitro-N-nitroso-guanidine-treated mice or H2O 2-treated cells. Minocycline blocked allergen-specific IgE production in B cells potentially by modulating T cell receptor (TCR)-linked IL-4 production at the mRNA level but not through a modulation of the IL-4-JAK-STAT-6 axis, IL-2 production, or NFAT1 activation. Restoration of IL-4, ex vivo, rescued IgE production by minocycline-treated/ovalbumin-stimulated B cells. IL-4 blockade correlated with a preferential inhibition of the NF-B activation arm of TCR but not GSK3, Src, p38 MAPK, or ERK1/2. Interestingly, the drug promoted a slightly higher Src and ERK1/2 phosphorylation. Inhibition of NF-B was linked to a complete blockade of TCR-stimulated GATA-3 expression, a pivotal transcription factor for IL-4 expression. Minocycline also reduced TNF-mediated NF-B activation and expression of dependent genes. These results show a potentially broad effect of minocycline but that it may block IgE production in part by modulating TCR function, particularly by inhibiting the signaling pathway, leading to NF-B activation, GATA-3 expression, and subsequent IL-4 production. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.