Abstract
We recently reported that phosphoinositide 3-kinase γ (PI3Kγ) directly regulates airway smooth muscle (ASM) contraction by modulating Ca2+ oscillations. Because ASM contraction plays a critical role in airway hyperresponsiveness (AHR) of asthma, the aim of the present study was to determine whether targeting PI3Kγ in ASM cells could suppress AHR in vitro and in vivo. Intranasal administration into mice of interleukin-13 (IL-13; 10 μg per mouse), a key pathophysiologic cytokine in asthma, induced AHR after 48 h, as assessed by invasive tracheostomy. Intranasal administration of a broad-spectrum PI3K inhibitor or a PI3Kγ-specific inhibitor 1 h before AHR assessment attenuated IL-13 effects. Airway responsiveness to bronchoconstrictor agonists was also examined in precision-cut mouse lung slices pretreated without or with IL-13 for 24 h. Acetylcholine and serotonin dose-response curves indicated that IL-13-treated lung slices had a 40 to 50% larger maximal airway constriction compared with controls. Furthermore, acetylcholine induced a larger initial Ca2+ transient and increased Ca2+ oscillations in IL-13-treated primary mouse ASM cells compared with control cells, correlating with increased cell contraction. As expected, PI3Kγ inhibitor treatment attenuated IL-13-augmented airway contractility of lung slices and ASM cell contraction. In both control and IL-13-treated ASM cells, small interfering RNA-mediated knockdown of PI3Kγ by 70% only reduced the initial Ca2+ transient by 20 to 30% but markedly attenuated Ca2+ oscillations and contractility of ASM cells by 50 to 60%. This report is the first to demonstrate that PI3Kγ in ASM cells is important for IL-13-induced AHR and that acute treatment with a PI3Kγ inhibitor can ameliorate AHR in a murine model of asthma.
Footnotes
This work was supported by the National Institutes of Health National Center for Research Resources [Grant G20-RR024001]; and in part by an American Asthma Foundation Early Excellence Award (to Y.T.) and the State of Nebraska Research Fund [Grant LB692] (to Y.T. and T.B.C.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
ABBREVIATIONS:
- AHR
- airway hyperresponsiveness
- ACh
- acetylcholine
- ASM
- airway smooth muscle
- GPCR
- G protein-coupled receptor
- IL-13
- interleukin-13
- PBS
- phosphate-buffered saline
- PI3Kγ
- phosphoinositide 3-kinase γ
- BSA
- bovine serum albumin
- DMSO
- dimethyl sulfoxide
- siRNA
- small interfering RNA
- RL
- airway resistance
- ANOVA
- analysis of variance
- LY294002
- 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
- LY303511
- 2-piperazinyl-8-phenyl-4H-1-benzopyran-4-one.
- Received November 4, 2011.
- Accepted April 26, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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