Hikari Koga

IL-17A is essential to the development of elastase-induced pulmonary inflammation and emphysema in mice

BackgroundPulmonary emphysema is characterized by alveolar destruction and persistent inflammation of the airways. Although IL-17A contributes to many chronic inflammatory diseases, it’s role in the inflammatory response of elastase-induced emphysema remains unclear.MethodsIn a model of elastase-induced pulmonary emphysema we examined the response of IL-17A-deficient mice, monitoring airway inflammation, static compliance, lung histology and levels of neutrophil-related chemokine and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) fluid.ResultsWild-type mice developed emphysematous changes in the lung tissue on day 21 after elastase treatment, whereas emphysematous changes were decreased in IL-17A-deficient mice compared to wild-type mice. Neutrophilia in BAL fluid, seen in elastase-treated wild-type mice, was reduced in elastase-treated IL-17A-deficient mice on day 4, associated with decreased levels of KC, MIP-2 and IL-1 beta. Elastase-treated wild-type mice showed increased IL-17A levels as well as increased numbers of IL-17A+ CD4 T cells in the lung in the initial period following elastase treatment.ConclusionsThese data identify the important contribution of IL-17A in the development of elastase-induced pulmonary inflammation and emphysema. Targeting IL-17A in emphysema may be a potential therapeutic strategy for delaying disease progression.

Inhibition of neutrophil elastase attenuates airway hyperresponsiveness and inflammation in a mouse model of secondary allergen challenge: neutrophil elastase inhibition attenuates allergic airway responses

BackgroundChronic asthma is often associated with neutrophilic infiltration in the airways. Neutrophils contain elastase, a potent secretagogue in the airways, nonetheless the role for neutrophil elastase as well as neutrophilic inflammation in allergen-induced airway responses is not well defined. In this study, we have investigated the impact of neutrophil elastase inhibition on the development of allergic airway inflammation and airway hyperresponsiveness (AHR) in previously sensitized and challenged mice.MethodsBALB/c mice were sensitized and challenged (primary) with ovalbumin (OVA). Six weeks later, a single OVA aerosol (secondary challenge) was delivered and airway inflammation and airway responses were monitored 6 and 48 hrs later. An inhibitor of neutrophil elastase was administered prior to secondary challenge.ResultsMice developed a two-phase airway inflammatory response after secondary allergen challenge, one neutrophilic at 6 hr and the other eosinophilic, at 48 hr. PAR-2 expression in the lung tissues was enhanced following secondary challenge, and that PAR-2 intracellular expression on peribronchial lymph node (PBLN) T cells was also increased following allergen challenge of sensitized mice. Inhibition of neutrophil elastase significantly attenuated AHR, goblet cell metaplasia, and inflammatory cell accumulation in the airways following secondary OVA challenge. Levels of IL-4, IL-5 and IL-13, and eotaxin in BAL fluid 6 hr after secondary allergen challenge were significantly suppressed by the treatment. At 48 hr, treatment with the neutrophil elastase inhibitor significantly reduced the levels of IL-13 and TGF-β1 in the BAL fluid. In parallel, in vitro IL-13 production was significantly inhibited in spleen cells from sensitized mice.ConclusionThese data indicate that neutrophil elastase plays an important role in the development of allergic airway inflammation and hyperresponsiveness, and would suggest that the neutrophil elastase inhibitor reduced AHR to inhaled methacholine indicating the potential for its use as a modulator of the immune/inflammatory response in both the neutrophil- and eosinophil-dominant phases of the response to secondary allergen challenge.

Growth Factors Temporally Associate with Airway Responsiveness and Inflammation in Allergen-Exposed Mice

Background: To clarify whether growth factors play critical roles in the development of airway hyperresponsiveness (AHR) and airway inflammation in the early stages of asthma, the relationship between growth factors and AHR and airway inflammation were analyzed in a mouse model of asthma. Methods: Following ovalbumin (OVA) sensitization and challenge, airway function, inflammation, cytokine and growth factor levels were monitored. Results: AHR to inhaled methacholine increased at 6 h, peaked at 48 h, and remained elevated for 14 days. IL-4 and IL-5 levels in bronchoalveolar lavage (BAL) fluid were increased at 6 h, peaked at 24 h, but returned to baseline quickly. IL-13 levels increased up to 14 days, peaking at 48 h. Increases in BAL fluid transforming growth factor-β1 and platelet-derived growth factor were observed at 12 h, and remained elevated at 14 days. Nerve growth factor levels were increased at 24–28 days. BAL fluid hepatocyte growth factor (HGF) was detected at 12 h, peaked at 24 h, and returned to baseline by 72 h. c-Met/HGF receptor was detected in the airways at 6 h, before HGF in the BAL, and continued to be observed 96 h after the last OVA challenge. Conclusions: These data identify a temporal association between growth factor production and Th2 cytokine production and the kinetics of AHR. Growth factors may play important roles in the development of allergic airway inflammation and AHR even in the early stages of asthma, before remodeling is initiated.

Effect of a Cysteinyl Leukotriene Receptor Antagonist on Experimental Emphysema and Asthma Combined with Emphysema

The incidence of overlapping bronchial asthma and chronic obstructive pulmonary disease has increased in recent years. Cysteinyl leukotrienes (CysLTs) play an important role in asthma, and the type 1 CysLT receptor (CysLT1R) is expressed by many inflammatory cells. We evaluated the effect of montelukast, a CysLT1R antagonist, on mouse models of asthma, porcine pancreatic elastase (PPE)-induced emphysema, and asthma combined with emphysema. Mice were sensitized with ovalbumin (OVA) on Days 0 and 14 and subsequently challenged with OVA on Days 28, 29, and 30. Pulmonary emphysema was induced by intratracheal instillation of PPE on Day 25. Mice were treated subcutaneously with montelukast or vehicle from Day 25 to Day 31. Airway hyperresponsiveness (AHR), static compliance; the number of inflammatory cells, the levels of cytokines, chemokines, LTs, and perforin in the bronchoalveolar lavage fluid, and the quantitative morphometry of lung sections were analyzed on Day 32. Treatment with montelukast significantly attenuated the AHR and eosinophilic airway inflammation in OVA-sensitized and OVA-challenged mice. Administration of montelukast significantly reduced the AHR, static compliance, and neutrophilic airway inflammation, while attenuating emphysematous lung changes, in PPE-treated mice. In PPE-treated mice subjected to allergen sensitization and challenges, montelukast significantly suppressed the AHR, static compliance, and eosinophilic and neutrophilic airway inflammation in addition to the development of experimentally induced emphysema in the lungs. Our data suggest that CysLT1R antagonists may be effective in ameliorating the consequences of PPE-induced lung damage and the changes that follow allergen sensitization and challenges.

Blocking the Leukotriene B4 Receptor 1 Inhibits Late-Phase Airway Responses in Established Disease

Most of the studies investigating the effectiveness of blocking the leukotriene B4 (LTB4) receptor 1 (BLT1) have been performed in models of primary or acute allergen challenge. The role of the LTB4-BLT1 pathway in secondary challenge models, where airway hyperresponsiveness (AHR) and airway inflammation have been established, has not been defined. We investigated the effects of blocking BLT1 on early- and late-phase development of AHR and airway inflammation in previously sensitized and challenged mice. Female BALB/c mice were sensitized (Days 1 and 14) and challenged (primary, Days 28-30) with ovalbumin. On Day 72, mice were challenged (secondary) with a single OVA aerosol, and the early and late phases of AHR and inflammation were determined. Specific blockade of BLT1 was attained by oral administration of a BLT1 antagonist on Days 70 through 72. Administration of the antagonist inhibited the secondary ovalbumin challenge-induced alterations in airway responses during the late phase but not during the early phase, as demonstrated by decreases in AHR and in bronchoalveolar lavage neutrophilia and eosinophilia 6 and 48 hours after secondary challenge. The latter was associated with decreased levels of KC protein, macrophage inflammatory protein 2, and IL-17 in the airways. These data identify the importance of the LTB4-BLT1 pathway in the development of late-phase, allergen-induced airway responsiveness after secondary airway challenge in mice with established airway disease.

Requirement for chemokine receptor 5 in the development of allergen-induced airway hyperresponsiveness and inflammation.

Chemokine receptor (CCR) 5 is expressed on dendritic cells, macrophages, CD8 cells, memory CD4 T cells, and stromal cells, and is frequently used as a marker of T helper type 1 cells. Interventions that abrogate CCR5 or interfere with its ligand binding have been shown to alter T helper type 2-induced inflammatory responses. The role of CCR5 on allergic airway responses is not defined. CCR5-deficient (CCR5(-/-)) and wild-type (CCR5(+/+)) mice were sensitized and challenged with ovalbumin (OVA) and allergic airway responses were monitored 48 hours after the last OVA challenge. Cytokine levels in lung cell culture supernatants were also assessed. CCR5(-/-) mice showed significantly lower airway hyperresponsiveness (AHR) and lower numbers of total cells, eosinophils, and lymphocytes in bronchoalveolar lavage (BAL) fluid compared with CCR5(+/+) mice after sensitization and challenge. The levels of IL-4 and IL-13 in BAL fluid of CCR5(-/-) mice were lower than in CCR5(+/+) mice. Decreased numbers of lung T cells were also detected in CCR5(-/-) mice after sensitization and challenge. Transfer of OVA-sensitized T cells from CCR5(+/+), but not transfer of CCR5(-/-) cells, into CCR5(-/-) mice restored AHR and numbers of eosinophils in BAL fluid after OVA challenge. Accordingly, the numbers of airway-infiltrating donor T cells were significantly higher in the recipients of CCR5(+/+) T cells. Taken together, these data suggest that CCR5 plays a pivotal role in allergen-induced AHR and airway inflammation, and that CCR5 expression on T cells is essential to the accumulation of these cells in the airways.

Emphysema Requires the Receptor for Advanced Glycation End-Products Triggering on Structural Cells

Pulmonary emphysema is characterized by persistent inflammation and progressive alveolar destruction. The receptor for advanced glycation end-products (RAGE) is a multiligand cell surface receptor reported to be involved in the process of acute alveolar epithelial cell injury. However, studies that address the role of RAGE in pulmonary emphysema are inconclusive. We investigated the role of RAGE in the development of elastase-induced pulmonary inflammation and emphysema in mice. RAGE-sufficient (RAGE(+/+)) mice and RAGE-deficient (RAGE(-/-)) mice were treated with intratracheal elastase on Day 0. Airway inflammation, static lung compliance, lung histology, and the levels of neutrophil-related chemokine and proinflammatory cytokines in bronchoalveolar lavage fluid were determined on Days 4 and 21. Neutrophilia in bronchoalveolar lavage fluid, seen in elastase-treated RAGE(+/+) mice, was reduced in elastase-treated RAGE(-/-) mice on Day 4, and was associated with decreased levels of keratinocyte chemoattractant, macrophage inflammatory protein-2, and IL-1β. Static lung compliance values and emphysematous changes in the lung tissue were decreased in RAGE(-/-) mice compared with RAGE(+/+) mice on Day 21 after elastase treatment. Experiments using irradiated, bone marrow-chimeric mice showed that the mice expressing RAGE on radioresistant structural cells, but not hematopoietic cells, developed elastase-induced neutrophilia and emphysematous change in the lung. In contrast, mice expressing RAGE on hematopoietic cells, but not radioresistant structural cells, showed reduced neutrophilia and emphysematous change in the lung. These data identify the importance of RAGE expressed on lung structural cells in the development of elastase-induced pulmonary inflammation and emphysema. Thus, RAGE represents a novel therapeutic target for preventing pulmonary emphysema.