Background:Ozone increases IL-33 in the lungs, and obesity augments the pulmonary effects of acute ozone exposure.Objectives:We assessed the role of IL-33 in the augmented effects of ozone observed in obese mice.Methods:Lean wildtype and obese db/db mice were pretreated with antibodies blocking the IL-33 receptor, ST2, and then exposed to ozone (2 ppm for 3 hr). Airway responsiveness was assessed, bronchoalveolar lavage (BAL) was performed, and lung cells harvested for flow cytometry 24 hr later. Effects of ozone were also assessed in obese and lean mice deficient in γδ T cells and their wildtype controls.Resultsand Discussion: Ozone caused greater increases in BAL IL-33, neutrophils, and airway responsiveness in obese than lean mice. Anti-ST2 reduced ozone-induced airway hyperresponsiveness and inflammation in obese mice but had no effect in lean mice. Obesity also augmented ozone-induced increases in BAL CXCL1 and IL-6, and in BAL type 2 cytokines, whereas anti-ST2 treatment reduced these cytokines. In obese mice, ozone increased lung IL-13+ innate lymphoid cells type 2 (ILC2) and IL-13+ γδ T cells. Ozone increased ST2+ γδ T cells, indicating that these cells can be targets of IL-33, and γδ T cell deficiency reduced obesity-related increases in the response to ozone, including increases in type 2 cytokines.Conclusions:Our data indicate that IL-33 contributes to augmented responses to ozone in obese mice. Obesity and ozone also interacted to promote type 2 cytokine production in γδ T cells and ILC2 in the lungs, which may contribute to the observed effects of IL-33.Citation:Mathews JA, Krishnamoorthy N, Kasahara DI, Cho Y, Wurmbrand AP, Ribeiro L, Smith D, Umetsu D, Levy BD, Shore SA. 2017. IL-33 drives augmented responses to ozone in obese mice. Environ Health Perspect 125:246–253; http://dx.doi.org/10.1289/EHP272

Obesity is a risk factor for the development of asthma. Obese mice exhibit innate airway hyperresponsiveness (AHR), a characteristic feature of asthma, and IL-17A is required for development of AHR in obese mice. The purpose of this study was to examine the temporal association between the onset of AHR and changes in IL-17A during the development of obesity by high-fat feeding in mice. At weaning, C57BL/6J mice were placed either on mouse chow or on a high-fat diet (HFD) and examined 9, 12, 15, 18, or 24 weeks later. Airway responsiveness to aerosolized methacholine (assessed via the forced oscillation technique) was greater in mice fed HFD versus chow for 24 weeks but not at earlier time points. Bronchoalveolar lavage and serum IL-17A were not affected by either the type or duration of diet, but increased pulmonary IL17a mRNA abundance was observed in HFD versus chow fed mice after both 18 and 24 weeks. Flow cytometry also confirmed an increase in IL-17A+ γδ T cells and IL-17A+ CD4+ T (Th17) cells in lungs of HFD versus chow fed mice. Pulmonary expression of Cfd (complement factor D, adipsin), a gene whose expression can be reduced by IL-17A, decreased after both 18 and 24 weeks in HFD versus chow fed mice. Furthermore, pulmonary Cfd mRNA abundance correlated with elevations in pulmonary Il17a mRNA expression and with AHR. Serum levels of TNFα, MIP-1α, and MIP-1β, and classical markers of systemic inflammation of obesity were significantly greater in HFD than chow fed mice after 24 weeks, but not earlier. In conclusion, our data indicate that pulmonary rather than systemic IL-17A is important for obesity-related AHR and suggest that changes in pulmonary Cfd expression contribute to these effects of IL-17A. Further, the observation that increases in Il17a preceded the development of AHR by several weeks suggests that IL-17A interacts with other factors to promote AHR. The observation that the onset of the systemic inflammation of obesity coincided temporally with the development of AHR suggest that systemic inflammation may be one of these factors.

Ozone and obesity both increase IL-17A in the lungs. In mice, obesity augments the airway hyperresponsiveness and neutrophil recruitment induced by acute ozone exposure. Therefore, we examined the role of IL-17A in obesity-related increases in the response to ozone observed in obese mice. Lean wild-type and obese db/db mice were pretreated with IL-17A-blocking or isotype antibodies, exposed to air or ozone (2 ppm for 3 h), and evaluated 24 hours later. Microarray analysis of lung tissue gene expression was used to examine the mechanistic basis for effects of anti-IL-17A. Compared with lean mice, ozone-exposed obese mice had greater concentrations of BAL IL-17A and greater numbers of pulmonary IL-17A cells. Ozone-induced increases in BAL IL-23 and CCL20, cytokines important for IL-17A cell recruitment and activation, were also greater in obese mice. Anti-IL-17A treatment reduced ozone-induced airway hyperresponsiveness toward levels observed in lean mice. Anti-IL-17A treatment also reduced BAL neutrophils in both lean and obese mice, possibly because of reductions in CXCL1. Microarray analysis identified gastrin-releasing peptide (GRP) receptor (Grpr) among those genes that were both elevated in the lungs of obese mice after ozone exposure and reduced after anti-IL-17A treatment. Furthermore, ozone exposure increased BAL GRP to a greater extent in obese than in lean mice, and GRP-neutralizing antibody treatment reduced obesity-related increases in ozone-induced airway hyperresponsiveness and neutrophil recruitment. Our data indicate that IL-17A contributes to augmented responses to ozone in db/db mice. Furthermore, IL-17A appears to act at least in part by inducing expression of Grpr.

We examined the role of γδ T cells in the induction of alternatively activated M2 macrophages and the resolution of inflammation after ozone exposure. Wildtype (WT) mice and mice deficient in γδ T cells (TCRδ-/- mice) were exposed to air or to ozone (0.3 ppm for up to 72h) and euthanized immediately or 1, 3, or 5 days after cessation of exposure. In WT mice, M2 macrophages accumulated in the lungs over the course of ozone exposure. Pulmonary mRNA abundance of the M2 genes, Arg1, Retnla, and Clec10a, also increased after ozone. In contrast, no evidence of M2 polarization was observed in TCRδ-/- mice. WT but not TCRδ-/- mice expressed the M2c polarizing cytokine, IL-17A, after ozone exposure and WT mice treated with an IL-17A neutralizing antibody exhibited attenuated ozone-induced M2 gene expression. In WT mice, ozone-induced increases in bronchoalveolar lavage neutrophils and macrophages resolved quickly after cessation of ozone exposure returning to air exposed levels within 3 days. However, lack of M2 macrophages in TCRδ-/- mice was associated with delayed clearance of inflammatory cells after cessation of ozone and increased accumulation of apoptotic macrophages in the lungs. Delayed restoration of normal lung architecture was also observed in TCRδ-/- mice. In summary, our data indicate that γδ T cells are required for the resolution of ozone-induced inflammation, likely because γδ T cells, through their secretion of IL-17A, contribute to changes in macrophage polarization that promote clearance of apoptotic cells.

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Use of acute-phase proteins (APPs) for assessment of health and disease in animals has increased greatly within the last decade. The objective was to determine the normal concentration of APPs in the serum and cerebrospinal fluid (CSF) of healthy cattle by polyacrylamide gel electrophoresis. Fifty crossbred animals (350±70kg of BW and 18±1.2 months of age), 25 heifers and 25 steers were used. CSF samples were collected from atlanto-occipital (AO) site and blood samples were obtained from the jugular vein. CSF and serum protein electrophoresis were performed by means of sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Thirty-seven proteins with molecular weights ranging from 7 and 37kDa were identified in CSF of all animals. These eight were nominally identified with immunoglobulin A and G, celuloplasmin, transferrin, albumin, α1-antitripsin, acidic glycoprotein, and haptoglobin. All protein fractions in CSF did not differ between heifers and steers. In sera, 34 proteins with molecular weights between 7 and 244kDa were identified in heifers and steers. Similar proteins were nominally identified in the sera, but only the CSF presented α1-antitripsin. The serum values of acidic glycoprotein and immunoglobulin G were significantly higher in steers compared with heifers. In conclusion, measurement of CSF acute phase protein concentrations can be useful in diagnosing and monitoring the progression of bovine neurological diseases, perhaps even to guide therapeutic procedures. The CSF electrophoretic profile of healthy cattle does not change depending on gender.

Pulmonary disorders are common in horses, and treatment efficiency depends on an adequate diagnosis. Amyloid A is the most sensitive indicator of pathology in horses. The objective of this study was to establish the concentration of amyloid A of bronchoalveolar lavage fluid (BALF) in healthy horses. Health condition of horses was considered normal based on physical examination, complete blood count, biochemical parameters, and BALF cytology. Blood and BALF were collected from thirty adult female horses. Amyloid A concentrations in serum and BALF were measured using commercial ELISA tests. Amyloid A was detected in serum (mean ± SD = 3.71±2.51) and BALF (mean ± SD = 0.000745±0.000785) of all horses. In conclusion, SAA can also be measured in bronchoalveolar fluid, affording early detection of respiratory infections or inflammatory conditions.