ABSTRACT
Adiponectin is an adipose-derived hormone with anti-inflammatory activity. Following subacute ozone exposure (0.3 ppm for 24-72 h), neutrophilic inflammation and IL-6 are augmented in adiponectin-deficient (Adipo(-/-)) mice. The IL-17/granulocyte colony-stimulating factor (G-CSF) axis is required for this increased neutrophilia. We hypothesized that elevated IL-6 in Adipo(-/-) mice contributes to their augmented responses to ozone via effects on IL-17A expression. Therefore, we generated mice deficient in both adiponectin and IL-6 (Adipo(-/-)/IL-6(-/-)) and exposed them to ozone or air. In ozone-exposed mice, bronchoalveolar lavage (BAL) neutrophils, IL-6, and G-CSF, and pulmonary Il17a mRNA expression were greater in Adipo(-/-) vs. wild-type mice, but reduced in Adipo(-/-)/IL-6(-/-) vs. Adipo(-/-) mice. IL-17A(+) F4/80(+) cells and IL-17A(+) γδ T cells were also reduced in Adipo(-/-)/IL-6(-/-) vs. Adipo(-/-) mice exposed to ozone. Only BAL neutrophils were reduced in IL-6(-/-) vs. wild-type mice. In wild-type mice, IL-6 was expressed in Gr-1(+)F4/80(-)CD11c(-) cells, whereas in Adipo(-/-) mice F4/80(+)CD11c(+) cells also expressed IL-6, suggesting that IL-6 is regulated by adiponectin in these alveolar macrophages. Transcriptomic analysis identified serum amyloid A3 (Saa3), which promotes IL-17A expression, as the gene most differentially augmented by ozone in Adipo(-/-) vs. wild-type mice. After ozone, Saa3 mRNA expression was markedly greater in Adipo(-/-) vs. wild-type mice but reduced in Adipo(-/-)/IL-6(-/-) vs. Adipo(-/-) mice. In conclusion, our data support a pivotal role of IL-6 in the hyperinflammatory condition observed in Adipo(-/-) mice after ozone exposure and suggest that this role of IL-6 involves its ability to induce Saa3, IL-17A, and G-CSF.
Subject(s)
Adiponectin/deficiency , Inflammation/immunology , Interleukin-6/metabolism , Macrophages, Alveolar/metabolism , Ozone/pharmacology , Animals , Bronchoalveolar Lavage Fluid/cytology , Granulocyte Colony-Stimulating Factor/genetics , Granulocyte Colony-Stimulating Factor/immunology , Interleukin-17/genetics , Interleukin-17/immunology , Interleukin-6/genetics , Lung/metabolism , Lymphocyte Count , Macrophages, Alveolar/cytology , Mice , Mice, Inbred C57BL , Mice, Knockout , Neutrophils/immunology , Oxidants, Photochemical/pharmacology , RNA, Messenger/biosynthesis , Receptors, Antigen, T-Cell, gamma-delta/metabolism , Serum Amyloid A Protein/genetics , T-Lymphocytes/cytologyABSTRACT
Adiponectin, an adipose derived hormone with pleiotropic functions, binds to several proteins, including T-cadherin. We have previously reported that adiponectin deficient (Adipo(-/-)) mice have increased IL-17A-dependent neutrophil accumulation in their lungs after subacute exposure to ozone (0.3 ppm for 72 hrs). The purpose of this study was to determine whether this anti-inflammatory effect of adiponectin required adiponectin binding to T-cadherin. Wildtype, Adipo(-/-) , T-cadherin deficient (T-cad(-/-) ), and bideficient (Adipo(-/-)/T-cad(-/-) ) mice were exposed to subacute ozone or air. Compared to wildtype mice, ozone-induced increases in pulmonary IL-17A mRNA expression were augmented in T-cad(-/-) and Adipo(-/-) mice. Compared to T-cad(-/-) mice, there was no further increase in IL-17A in Adipo(-/-)/T-cad(-/-) mice, indicating that adiponectin binding to T-cadherin is required for suppression of ozone-induced IL-17A expression. Similar results were obtained for pulmonary mRNA expression of saa3, an acute phase protein capable of inducing IL-17A expression. Comparison of lung histological sections across genotypes also indicated that adiponectin attenuation of ozone-induced inflammatory lesions at bronchiolar branch points required T-cadherin. BAL neutrophils and G-CSF were augmented in T-cad(-/-) mice and further augmented in Adipo(-/-)/T-cad(-/-) mice. Taken together with previous observations indicating that augmentation of these moieties in ozone exposed Adipo(-/-) mice is partially IL-17A dependent, the results indicate that effects of T-cadherin deficiency on BAL neutrophils and G-CSF are likely secondary to changes in IL-17A, but that adiponectin also acts via T-cadherin independent pathways. Our results indicate that T-cadherin is required for the ability of adiponectin to suppress some but not all aspects of ozone-induced pulmonary inflammation.
Subject(s)
Adiponectin/metabolism , Cadherins/metabolism , Lung/drug effects , Lung/metabolism , Ozone/adverse effects , Adiponectin/genetics , Animals , Cadherins/genetics , Chemokines/metabolism , Cytokines/metabolism , Female , Male , Mice , Mice, KnockoutABSTRACT
CONTEXT: Chamber studies in adult humans indicate reduced responses to acute ozone with increasing age. Age-related changes in TNFα have been observed. TNFα induced inflammation is predominantly mediated through TNFR1. OBJECTIVE: To examine the impact of aging on inflammatory responses to acute ozone exposure in mice and determine the role of TNFR1 in age-related differences. MATERIALS AND METHODS: Wildtype and TNFR1 deficient (TNFR1(-/-)) mice aged 7 or 39 weeks were exposed to ozone (2 ppm for 3 h). Four hours after exposure, bronchoalveolar lavage (BAL) was performed and BAL cells, cytokines, chemokines, and protein were examined. RESULTS: Ozone-induced increases in BAL neutrophils and in neutrophil chemotactic factors were lower in 39- versus 7-week-old wildtype, but not (TNFR1(-/-)) mice. There was no effect of TNFR1 genotype in 7-week-old mice, but in 39-week-old mice, BAL neutrophils and BAL concentrations of MCP-1, KC, MIP-2, IL-6 and IP-10 were significantly greater following ozone exposure in TNFR1(-/-) versus wildtype mice. BAL concentrations of the soluble form of the TNFR1 receptor (sTNFR1) were substantially increased in 39-week-old versus 7-week-old mice, regardless of exposure. DISCUSSION AND CONCLUSION: The data suggest that increased levels of sTNFR1 in the lungs of the 39-week-old mice may neutralize TNFα and protect these older mice against ozone-induced inflammation.
