Innate cellular sources of interleukin-17A regulate macrophage accumulation in cigarette- smoke-induced lung inflammation in mice.

Cigarette smoke (CS) is the major cause of chronic obstructive pulmonary disease (COPD). Interleukin-17A (IL-17A) is a pivotal cytokine that regulates lung immunity and inflammation. The aim of the present study was to investigate how IL-17A regulates CS-induced lung inflammation in vivo. IL-17A knockout (KO) mice and neutralization of IL-17A in wild-type (WT) mice reduced macrophage and neutrophil recruitment and chemokine (C-C motif) ligand 2 (CCL2), CCL3 and matrix metalloproteinase (MMP)-12 mRNA expression in response to acute CS exposure. IL-17A expression was increased in non-obese diabetic (NOD) severe combined immunodeficiency SCID) mice with non-functional B- and T-cells over a 4-week CS exposure period, where macrophages accumulated to the same extent as in WT mice. Gene expression analysis by QPCR (quantitative real-time PCR) of isolated immune cell subsets detected increased levels of IL-17A transcript in macrophages, neutrophils and NK/NKT cells in the lungs of CS-exposed mice. In order to further explore the relative contribution of innate immune cellular sources, intracellular IL-17A staining was performed. In the present study, we demonstrate that CS exposure primes natural killer (NK), natural killer T (NKT) and γδ T-cells to produce more IL-17A protein and CS alone increased the frequency of IL17+ γδ T-cells in the lung, whereas IL-17A protein was not detected in macrophages and neutrophils. Our data suggest that activation of innate cellular sources of IL-17A is an essential mediator of macrophage accumulation in CS-exposed lungs. Targeting non-conventional T-cell sources of IL-17A may offer an alternative strategy to reduce pathogenic macrophages in COPD.

Neutralizing granulocyte/macrophage colony-stimulating factor inhibits cigarette smoke-induced lung inflammation.

RATIONALE: Cigarette smoke is the major cause of chronic obstructive pulmonary disease (COPD), and there is currently no satisfactory therapy to treat people with COPD. We have previously shown that granulocyte/macrophage colony-stimulating factor (GM-CSF) regulates lung innate immunity to LPS through Akt/Erk activation of nuclear factor-kappaB and activator protein (AP)-1. OBJECTIVES: The aim of this study was to determine whether neutralization of GM-CSF can inhibit cigarette smoke-induced lung inflammation in vivo. METHODS: Male BALB/c mice were exposed to cigarette smoke generated from 9 cigarettes per day for 4 days. Mice were treated intranasally with 100 microg 22E9 (anti-GM-CSF mAb) and isotype control antibody on Days 2 and 4, 1 hour before cigarette smoke or sham exposure. On the fifth day mice were killed, and the lungs were lavaged with PBS and then harvested for genomic and proteomic analysis. MEASUREMENTS AND MAIN RESULTS: Cigarette smoke-exposed mice treated with anti-GM-CSF mAb had significantly less BALF macrophages and neutrophils, whole lung TNF-alpha, macrophage inflammatory protein (MIP)-2, and matrix metalloproteinase (MMP)-12 mRNA expression and lost less weight compared with smoke-exposed mice treated with isotype control. In contrast, smoke-induced increases in MMP-9 and net gelatinase activity were unaffected by treatment with anti-GM-CSF. In addition, neutralization of GM-CSF did not affect the phagocytic function of alveolar macrophages. CONCLUSIONS: GM-CSF is a key mediator in smoke-induced airways inflammation, and its neutralization may have therapeutic implications in diseases such as COPD.