Identification of novel susceptibility genes in ozone-induced inflammation in mice

Dept of Pathobiology and Diagnostic Investigation Center for Integrative Toxicology B43 Food Safety and Toxicology Bldg, Michigan State University, East Lansing, MI 48824, USA.
European Respiratory Journal (Impact Factor: 7.64). 08/2010; 36(2):428-37. DOI: 10.1183/09031936.00145309
Source: PubMed


Ozone (O(3)) remains a prevalent air pollutant and public health concern. Inf2 is a significant quantitative trait locus on murine chromosome 17 that contributes to susceptibility to O(3)-induced infiltration of polymorphonuclear leukocytes (PMNs) into the lung, but the mechanisms of susceptibility remain unclear. The study objectives were to confirm and restrict Inf2, and to identify and test novel candidate susceptibility gene(s). Congenic strains of mice that contained overlapping regions of Inf2 and their controls, and mice deficient in either major histocompatibility complex (MHC) class II genes or the Tnf cluster, were exposed to air or O(3). Lung inflammation and gene expression were assessed. Inf2 was restricted from 16.42 Mbp to 0.96 Mbp, and bioinformatic analysis identified MHC class II, the Tnf cluster and other genes in this region that contain potentially informative single nucleotide polymorphisms between the susceptible and resistant mice. Furthermore, O(3)-induced inflammation was significantly reduced in mice deficient in MHC class II genes or the Tnf cluster genes, compared with wild-type controls. Gene expression differences were also observed in MHC class II and Tnf cluster genes. This integrative genetic analysis of Inf2 led to identification of novel O(3) susceptibility genes that may provide important, new therapeutic targets in susceptible individuals.

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Available from: Wesley Gladwell, Jan 09, 2014
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    • "TNFα is not directly chemotactic for neutrophils [24]. However, in lean WT mice, TNFR2 deficiency or the TNFα antagonist, etanercept, reduced the O3-induced increase in BAL neutrophils (Fig. 4A,D) consistent with previous reports [22], [23], [60] indicating a role for TNFα in neutrophil recruitment induced by subacute O3. TNFα also contributes to neutrophil recruitment in other conditions (reviewed in [61]), though the mechanism is not well understood. "
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    ABSTRACT: Ozone is an air pollutant that causes pulmonary symptoms. In mice, ozone exposure causes pulmonary injury and increases bronchoalveolar lavage macrophages and neutrophils. We have shown that IL-17A is important in the recruitment of neutrophils after subacute ozone exposure (0.3 ppm for 24-72 h). We hypothesized that γδ T cells are the main producers of IL-17A after subacute ozone. To explore this hypothesis we exposed wildtype mice and mice deficient in γδ T cells (TCRδ-/-) to ozone or room air. Ozone-induced increases in BAL macrophages and neutrophils were attenuated in TCRδ-/- mice. Ozone increased the number of γδ T cells in the lungs and increased pulmonary Il17a mRNA expression and the number of IL-17A+ CD45+ cells in the lungs and these effects were abolished in TCRδ-/- mice. Ozone-induced increases in factors downstream of IL-17A signaling, including G-CSF, IL-6, IP-10 and KC were also decreased in TCRδ-/- versus wildtype mice. Neutralization of IL-17A during ozone exposure in wildtype mice mimicked the effects of γδ T cell deficiency. TNFR2 deficiency and etanercept, a TNFα antagonist, also reduced ozone-induced increases in Il17a mRNA, IL-17A+ CD45+ cells and BAL G-CSF as well as BAL neutrophils. TNFR2 deficient mice also had decreased ozone-induced increases in Ccl20, a chemoattractant for IL-17A+ γδ T cells. Il17a mRNA and IL-17A+ γδ T cells were also lower in obese Cpefat versus lean WT mice exposed to subacute ozone, consistent with the reduced neutrophil recruitment observed in the obese mice. Taken together, our data indicate that pulmonary inflammation induced by subacute ozone requires γδ T cells and TNFα-dependent recruitment of IL-17A+ γδ T cells to the lung.
    Full-text · Article · May 2014 · PLoS ONE
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    • "In healthy volunteers, the inflammatory response in the airways can occur at O3 levels near (0.08 ppm) or below (0.06 ppm) the National Ambient Air Quality Standard (NAAQS) for ambient O3 with noted variability across individuals, such that some are very responsive while others have a very weak inflammatory response, suggesting the presence of a inflammatory response phenotype in humans [8,9]. Previous studies in healthy adults [10] as well as in animals [11] have suggested that certain genes, such as the GSTM1null genotype, can act as genetic modifiers of the inflammatory response to O3 and may explain some of the individual variation often observed. At present, the role inflammatory responsiveness plays in O3 susceptibility is unclear, and its association with ozone-induced changes in innate immune function and host defense genomic signatures remain largely unknown. "
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    ABSTRACT: BACKGROUND: Exposure to ozone activates innate immune function and causes neutrophilic (PMN) airway inflammation that in some individuals is robustly elevated. The interplay between immuno-inflammatory function and genomic signaling in those with heightened inflammatory responsiveness to ozone is not well understood.Objectives Determine baseline predictors and post exposure discriminators for the immuno-inflammatory response to ozone in inflammatory responsive adult volunteers. METHODS: Sputum induction was performed on 27 individuals before and after a two hour chamber exposure to 0.4 ppm ozone. Subjects were classified as inflammatory responders or non-responders to ozone based on their PMN response. Innate immune function, inflammatory cell and cytokine modulation and transcriptional signaling pathways were measured in sputum. RESULTS: Post exposure, responders showed activated innate immune function (CD16: 31,004 MFI vs 8988 MFI; CD11b: 44,986 MFI vs 24,770 MFI; CD80: 2236 MFI vs 1506 MFI; IL-8: 37,603 pg/ml vs 2828 pg/ml; and IL-1beta: 1380 pg/ml vs 318 pg/ml) with muted signaling of immune cell trafficking pathways. In contrast, non-responders displayed decreased innate immune activity (CD16, CD80; phagocytosis: 2 particles/PMN vs 4 particles/PMN) post exposure that was accompanied by a heightened signaling of immune cell trafficking pathways. CONCLUSIONS: Inflammatory responsive and non responsive individuals to ozone show an inverse relationship between immune cell trafficking and immuno-inflammatory functional responses to ozone. These distinct genomic signatures may further our understanding about ozone-induced morbidity in individuals with different levels of inflammatory responsiveness.
    Full-text · Article · Oct 2012 · Respiratory research
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    • "For example, both gene expression analyses identified Ctse as differentially expressed between genotypes after exposure to O3. Ctse is a an intracellular aspartic protease that is found in immune system cells such as dendritic cells and macrophages and has been implicated in major histocompatibility complex (MHC) class II pathway antigen processing (e.g., Zaidi and Kalbacher 2008). Although Ctse has not been associated with O3-induced inflammation, MHC class II molecules have been implicated recently in the PMN response to O3 exposure in the mouse (Bauer et al. 2009), and it is plausible that CTSE could also be involved in this pathway. SAA and S100A14 have been implicated in inflammatory processes (e.g., Han et al. 2007) or inflammation-related diseases (Chen et al. 2009) and thus provide a rationale for a role in O3-induced inflammation. "
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    ABSTRACT: The mechanisms underlying ozone (O₃)-induced pulmonary inflammation remain unclear. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that is known to inhibit inflammatory mediators. We investigated the molecular mechanisms underlying interleuken-10 (IL-10)-mediated attenuation of O₃-induced pulmonary inflammation in mice. Il10-deficient (Il10(-/-)) and wild-type (Il10(+/+)) mice were exposed to 0.3 ppm O₃ or filtered air for 24, 48, or 72 hr. Immediately after exposure, differential cell counts and total protein (a marker of lung permeability) were assessed from bronchoalveolar lavage fluid (BALF). mRNA and protein levels of cellular mediators were determined from lung homogenates. We also used global mRNA expression analyses of lung tissue with Ingenuity Pathway Analysis to identify patterns of gene expression through which IL-10 modifies O₃-induced inflammation. Mean numbers of BALF polymorphonuclear leukocytes (PMNs) were significantly greater in Il10(-/-) mice than in Il10(+/+) mice after exposure to O₃ at all time points tested. O₃-enhanced nuclear NF-κB translocation was elevated in the lungs of Il10(-/-) compared with Il10(+/+) mice. Gene expression analyses revealed several IL-10-dependent and O₃-dependent mediators, including macrophage inflammatory protein 2, cathepsin E, and serum amyloid A3. Results indicate that IL-10 protects against O₃-induced pulmonary neutrophilic inflammation and cell proliferation. Moreover, gene expression analyses identified three response pathways and several genetic targets through which IL-10 may modulate the innate and adaptive immune response. These novel mechanisms of protection against the pathogenesis of O₃-induced pulmonary inflammation may also provide potential therapeutic targets to protect susceptible individuals.
    Full-text · Article · Dec 2010 · Environmental Health Perspectives
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