Protective effects of neuropeptide Y against elastase-induced pulmonary emphysema.

Neuropeptide Y (NPY) is a neuropeptide widely expressed in not only the central nervous system but also immune cells and the respiratory epithelium. Patients with chronic obstructive pulmonary disease (COPD) reportedly exhibit decreased NPY expression in the airway epithelium, but the involvement of NPY in the pathophysiology of COPD has not been defined. We investigated the role of NPY in elastase-induced emphysema. NPY-deficient (NPY-/-) mice and wild-type (NPY+/+) mice received intratracheal instillation of porcine pancreas elastase (PPE). The numbers of inflammatory cells and the levels of cytokines and chemokines in the bronchoalveolar lavage (BAL) fluid and lung homogenates were determined along with quantitative morphometry of lung sections. Intratracheal instillation of PPE induced emphysematous changes and increased NPY levels in the lungs. Compared with NPY+/+ mice, NPY-/- mice had significantly enhanced PPE-induced emphysematous changes and alveolar enlargement. Neutrophilia seen in BAL fluid of NPY+/+ mice on day 4 after PPE instillation was also enhanced in NPY-/- mice, and the enhancement was associated with increased levels of neutrophil-related and macrophage-related chemokines and IL-17A as well as increased numbers of type 3 innate lymphoid cells in the airways. Treatment with NPY significantly reduced PPE-induced emphysematous changes. Conversely, treatment with a NPY receptor antagonist exacerbated PPE-induced emphysematous changes. These observations indicate that NPY has protective effects against elastase-induced emphysema and suggest that targeting NPY in emphysema has potential as a therapeutic strategy for delaying disease progression.

Essential role of IL-23 in the development of acute exacerbation of pulmonary fibrosis.

Acute exacerbation of idiopathic pulmonary fibrosis has a poor prognosis associated with neutrophilic inflammation. Interleukin-23 is a proinflammatory cytokine involved in neutrophilic inflammation. However, little is known about its role in acute exacerbation of pulmonary fibrosis. This study was performed to determine the role of interleukin-23 in acute exacerbation of pulmonary fibrosis. For assessment of acute exacerbation of pulmonary fibrosis, mice were intratracheally administered bleomycin followed by lipopolysaccharide. Inflammatory cells, cytokine levels, and morphological morphometry of the lungs were analyzed. Cytokine levels were measured in the bronchoalveolar lavage fluid of idiopathic pulmonary fibrosis patients with or without acute exacerbation. Interleukin-23, -17A, and -22 levels were increased in the airway of mice with acute exacerbation of pulmonary fibrosis. Interleukin-23p19-deficient mice with acute exacerbation of pulmonary fibrosis had markedly reduced airway inflammation and fibrosis associated with decreased levels of interleukin-17A and -22 compared with wild-type mice. Treatment with an anti-interleukin-23 antibody attenuated airway inflammation and fibrosis and reduced interleukin-17A and -22 levels in mice with acute exacerbation of pulmonary fibrosis. T-helper type 17 cells were the predominant source of interleukin-17A in mice with acute exacerbation of pulmonary fibrosis. Interleukin-23 levels in bronchoalveolar lavage fluid tended to be higher in idiopathic pulmonary fibrosis patients with than without acute exacerbation. The data presented here suggest that interleukin-23 is essential for the development of acute exacerbation of pulmonary fibrosis and that blockade of interleukin-23 may be a new therapeutic strategy for acute exacerbation of pulmonary fibrosis.

Loss of IL-33 enhances elastase-induced and cigarette smoke extract-induced emphysema in mice.

BACKGROUND: IL-33, which is known to induce type 2 immune responses via group 2 innate lymphoid cells, has been reported to contribute to neutrophilic airway inflammation in chronic obstructive pulmonary disease. However, its role in the pathogenesis of emphysema remains unclear. METHODS: We determined the role of interleukin (IL)-33 in the development of emphysema using porcine pancreas elastase (PPE) and cigarette smoke extract (CSE) in mice. First, IL-33-/- mice and wild-type (WT) mice were given PPE intratracheally. The numbers of inflammatory cells, and the levels of cytokines and chemokines in the bronchoalveolar lavage (BAL) fluid and lung homogenates, were analyzed; quantitative morphometry of lung sections was also performed. Second, mice received CSE by intratracheal instillation. Quantitative morphometry of lung sections was then performed again. RESULTS: Intratracheal instillation of PPE induced emphysematous changes and increased IL-33 levels in the lungs. Compared to WT mice, IL-33-/- mice showed significantly greater PPE-induced emphysematous changes. No differences were observed between IL-33-/- and WT mice in the numbers of macrophages or neutrophils in BAL fluid. The levels of hepatocyte growth factor were lower in the BAL fluid of PPE-treated IL-33-/- mice than WT mice. IL-33-/- mice also showed significantly greater emphysematous changes in the lungs, compared to WT mice, following intratracheal instillation of CSE. CONCLUSION: These observations suggest that loss of IL-33 promotes the development of emphysema and may be potentially harmful to patients with COPD.

Tolerogenic signaling of alveolar macrophages induces lung adaptation to oxidative injury.

BACKGROUND: Inhaled oxidative toxicants present in ambient air cause airway epithelial injury, inflammation, and airway hyperresponsiveness. Effective adaptation to such environmental insults is essential for the preservation of pulmonary function, whereas failure or incomplete adaptation to oxidative injury can render the host susceptible to the development of airway disease. OBJECTIVE: We sought to explore the mechanisms of airway adaptation to oxidative injury. METHODS: For a model to study pulmonary adaptation to oxidative stress-induced lung injury, we exposed mice to repeated nose-only chlorine gas exposures. Outcome measures were evaluated 24 hours after the last chlorine exposure. Lung mechanics and airway responsiveness to methacholine were assessed by using the flexiVent. Inflammation and antioxidant responses were assessed in both bronchoalveolar lavage fluid and lung tissue. Using both loss or gain of function and genomic approaches, we further dissected the cellular and molecular mechanisms involved in pulmonary adaptation. RESULTS: Repeated exposures to oxidative stress resulted in pulmonary adaptation evidenced by abrogation of neutrophilic inflammation and airway hyperresponsiveness. This adaptation was independent of antioxidant mechanisms and regulatory T cells but dependent on residential alveolar macrophages (AMs). Interestingly, 5% of AMs expressed forkhead box P3, and depletion of these cells abolished adaptation. Results from transcriptomic profiling and loss and gain of function suggest that adaptation might be dependent on TGF-ß and prostaglandin E2. CONCLUSION: Pulmonary adaptation during oxidative stress-induced lung injury is mediated by a novel subset of forkhead box P3-positive AMs that limits inflammation, favoring airway adaptation and host fitness through TGF-ß and prostaglandin E2.

Requirement for neuropeptide Y in the development of type 2 responses and allergen-induced airway hyperresponsiveness and inflammation.

Neuropeptide Y (NPY) is a neurotransmitter that is widely expressed in the brain and peripheral nervous system. Various immune cells express the NPY Y1 receptor. NPY modulates these cells via its Y1 receptor; however, involvement of NPY in the pathophysiology of bronchial asthma, particularly airway hyperresponsiveness (AHR), has not been defined. NPY-deficient and wild-type mice were intranasally sensitized and challenged to house dust mite (HDM) extract, and airway responses were monitored. After sensitization and challenge, NPY-deficient mice showed significantly lower AHR than wild-type mice, and numbers of eosinophils and levels of type 2 cytokines [interleukin (IL)-4, IL-5, and IL-13] in bronchoalveolar lavage fluid were significantly lower. Type 2 cytokine production from splenic mononuclear cells of HDM-sensitized mice was also significantly lower in NPY-deficient mice. Flow cytometry analysis showed that the number of CD4 T cells and CD11c+ antigen-presenting cells (APCs) was significantly lower in the lungs of NPY-deficient mice than in wild-type mice following sensitization and challenge. Significantly fewer CD11c+ APCs phagocytosed HDM in the mediastinal lymph nodes of NPY-deficient mice than in those of wild-type mice. Treatment with BIBO-3304, a NPY receptor antagonist, significantly suppressed development of HDM-induced AHR and inflammation in wild-type mice. These data identify an important contribution of NPY to allergen-induced AHR and inflammation through accumulation of dendritic cells in the airway and promotion of the type 2 immune response. Thus, manipulating NPY represents a novel therapeutic target to control allergic airway responses.

A retinoid X receptor partial agonist attenuates pulmonary emphysema and airway inflammation.

BACKGROUND: Retinoid X receptors (RXRs) are members of the nuclear receptor (NR) superfamily that mediate signalling by 9-cis retinoic acid, a vitamin A derivative. RXRs play key roles not only as homodimers but also as heterodimeric partners, e.g., for retinoic acid receptors, vitamin D receptors, and peroxisome proliferator-activated receptors. The NR family may also play important roles in the development of emphysema. However, the role of RXRs in the pathogenesis of emphysema is not well defined. METHODS: We developed a novel RXR partial agonist (NEt-4IB) and investigated its effect and mechanism compared to a full agonist (bexarotene) in a murine model of emphysema. For emphysema induction, BALB/c mice received intraperitoneal cigarette smoke extract (CSE) or intratracheal porcine pancreas elastase (PPE). Treatment with RXR agonists was initiated before or after emphysema induction. RESULTS: Treatment with NEt-4IB significantly suppressed the increase in static lung compliance and emphysematous changes in CSE-induced emphysema and PPE-induced established and progressive emphysema. NEt-4IB significantly suppressed PPE-induced neutrophilic airway inflammation and the levels of keratinocyte chemoattractant (KC), C-X-C motif ligand5 (CXCL5), interferon (IFN)-γ and IL-17. NEt-4IB also improved the matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance and the reduced anti-oxidant activity in bronchoalveolar lavage (BAL) fluid. NEt-4IB suppressed PPE-induced vascular endothelial growth factor (VEGF) expression in the airway. Treatment with NEt-4IB and bexarotene significantly suppressed the increase in static lung compliance and emphysematous changes. However, adverse effects of RXR agonists, including hypertriglyceridemia and hepatomegaly, were observed in bexarotene-treated mice but not in NEt-4IB-treated mice. CONCLUSION: These data suggest that RXRs play crucial roles in emphysema and airway inflammation, and novel partial RXR agonists could be potential therapeutic strategies for the treatment of PPE- and CSE-induced emphysema.

Effect of a retinoid X receptor partial agonist on airway inflammation and hyperresponsiveness in a murine model of asthma.

BACKGROUND: Retinoid X receptors (RXRs) are members of the nuclear receptor (NR) superfamily that mediate signaling by 9-cis retinoic acid, a vitamin A (retinol) derivative. RXRs play key roles not only as homodimers but also as heterodimeric partners-e.g., retinoic acid receptors (RARs), vitamin D receptors (VDRs), liver X receptors (LXRs), and peroxisome proliferator-activated receptors (PPARs). The NR family was recently associated with allergic diseases, but the role of RXRs in allergen-induced airway responses is not well defined. The goal of this study is to elucidate the role of RXRs in asthma pathogenesis and the potency of RXR partial agonist in the treatment of allergic airway inflammation and airway hyperresponsiveness using a murine model of asthma. METHODS: We investigated the effect of a novel RXR partial agonist (NEt-4IB) on the development of allergic airway inflammation and airway hyperresponsiveness (AHR) in a murine model of asthma. Balb/c mice were sensitized (days 0 and 14) and challenged (days 28-30) with ovalbumin (OVA), and airway inflammation and airway responses were monitored 48 h after the last OVA challenge. NEt-4IB was administered orally on days 25 to 32. RESULTS: Oral administration of NEt-4IB significantly suppressed AHR and inflammatory cell accumulation in the airways and attenuated the levels of TNF-α in the lung and IL-5, IL-13 and NO levels in bronchoalveolar lavage (BAL) fluid and the number of periodic acid Schiff (PAS)-positive goblet cells in lung tissue. Treatment with NEt-4IB also significantly suppressed NF-κB expression. CONCLUSION: These data suggest that RXRs may be of crucial importance in the mechanism of allergic asthma and that the novel RXR partial agonist NEt-4IB may be a promising candidate for the treatment of allergic airway inflammation and airway hyperresponsiveness in a model of allergic asthma.

Protective Effects of Bisoprolol against Acute Exacerbation in Moderate-to-Severe Chronic Obstructive Pulmonary Disease.

Although recent retrospective studies suggested that the use of ß-blockers appears to help improve the mortality rate and decrease the rate of exacerbation in chronic obstructive pulmonary disease (COPD) patients with heart failure, the effects of ß-blockers on COPD patients without heart failure have not been established. Based on previous reports, we have launched a multicenter, prospective, single-arm phase II study to evaluate the preventive effect of the cardioselective ß-blocker bisoprolol in COPD exacerbation, in Japanese individuals with moderate-to-severe COPD who do not have heart failure but do have hypertension requiring the use of medication. The primary endpoint is the rate of mild-to-severe COPD exacerbation. The results of this study will clarify whether bisoprolol can prevent exacerbation in COPD patients without heart failure.

IL-23 Is Essential for the Development of Elastase-Induced Pulmonary Inflammation and Emphysema.

We recently reported that IL-17A plays a critical role in the development of porcine pancreatic elastase (PPE)-induced emphysema. The proliferation of T-helper type 17 (Th17) cells was induced by IL-23. To determine the contribution of IL-23 to the development of pulmonary emphysema, a mouse model of PPE-induced emphysema was used in which responses of IL-23p19-deficient (IL-23-/-) and wild-type (WT) mice were compared. Intratracheal instillation of PPE induced emphysematous changes in the lungs and was associated with increased levels of IL-23 in lung homogenates. Compared with WT mice, IL-23-/- mice developed significantly lower static compliance values and markedly reduced emphysematous changes on histological analyses after PPE instillation. These changes were associated with lower levels of IL-17A and fewer Th17 cells in the lung. The neutrophilia seen in bronchoalveolar lavage fluid of WT mice was attenuated in IL-23-/- mice, and the reduction was associated with decreased levels of keratinocyte-derived cytokine and macrophage inflammatory protein-2 in bronchoalveolar lavage fluid. Treatment with anti-IL-23p40 monoclonal antibody significantly attenuated PPE-induced emphysematous changes in the lungs of WT mice. These data identify the important contributions of IL-23 to the development of elastase-induced pulmonary inflammation and emphysema, mediated through an IL-23/IL-17 pathway. Targeting IL-23 in emphysema is a potential therapeutic strategy for delaying disease progression.

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-1ß. 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.

Contrasting roles for the receptor for advanced glycation end-products on structural cells in allergic airway inflammation vs. airway hyperresponsiveness.

The receptor for advanced glycation end-products (RAGE) is a multiligand receptor that belongs to the immunoglobulin superfamily. RAGE is reported to be involved in various inflammatory disorders; however, studies that address the role of RAGE in allergic airway disease are inconclusive. RAGE-sufficient (RAGE+/+) and RAGE-deficient (RAGE-/-) mice were sensitized to ovalbumin, and airway responses were monitored after ovalbumin challenge. RAGE-/- mice showed reduced eosinophilic inflammation and goblet cell metaplasia, lower T helper type 2 (Th2) cytokine production from spleen and peribronchial lymph node mononuclear cells, and lower numbers of group 2 innate lymphoid cells in the lung compared with RAGE+/+ mice following sensitization and challenge. Experiments using irradiated, chimeric mice showed that the mice expressing RAGE on radio-resistant structural cells but not hematopoietic cells developed allergic airway inflammation; however, the mice expressing RAGE on hematopoietic cells but not structural cells showed reduced airway inflammation. In contrast, absence of RAGE expression on structural cells enhanced innate airway hyperresponsiveness (AHR). In the absence of RAGE, increased interleukin (IL)-33 levels in the lung were detected, and blockade of IL-33 receptor ST2 suppressed innate AHR in RAGE-/- mice. These data identify the importance of RAGE expressed on lung structural cells in the development of allergic airway inflammation, T helper type 2 cell activation, and group 2 innate lymphoid cell accumulation in the airways. RAGE on lung structural cells also regulated innate AHR, likely through the IL-33-ST2 pathway. Thus manipulating RAGE represents a novel therapeutic target in controlling allergic airway responses.

Superiority of systemic bleomycin to intradermal HOCl for the study of interstitial lung disease.

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune dysregulation, and multi-organ fibrosis. Interstitial lung disease (ILD) is a complication of SSc and a leading cause of SSc-death. The administration of hypochlorous acid (HOCl) intradermally in the mouse (HOCl-SSc) purportedly shows several features typical of SSc. We studied the model by injecting BALB/c mice daily intradermally with HOCl for 6-weeks, an exposure reported to induce lung fibrosis. On day 42, the skinfold thickness and the dermal thickness were two and three times larger respectively in the HOCl group compared to controls. HOCl treatment did not result in histological features of pulmonary fibrosis nor significant changes in lung compliance. Automated image analysis of HOCl mice lungs stained with picrosirius red did not show increased collagen deposition. HOCl injections did not increase pulmonary mRNA expression of pro-fibrotic genes nor induced the production of serum advanced oxidation protein products and anti-topoisomerase 1 antibodies. Immune cells in bronchoalveolar lavage fluid (BALF) and whole lung digests were not increased in HOCl-treated animals. Since lung fibrosis is proposed to be triggered by oxidative stress, we injected HOCl to Nrf2-/- mice, a mouse deficient in many antioxidant proteins. Lung compliance, histology, and BALF leukocyte numbers were comparable between Nrf2-/- mice and wild-type controls. We conclude that the HOCl-SSc model does not manifest SSc-lung disease.

The Impact of Endoplasmic Reticulum-Associated Protein Modifications, Folding and Degradation on Lung Structure and Function.

The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and induces the unfolded protein response (UPR) and other mechanisms to restore ER homeostasis, including translational shutdown, increased targeting of mRNAs for degradation by the IRE1-dependent decay pathway, selective translation of proteins that contribute to the protein folding capacity of the ER, and activation of the ER-associated degradation machinery. When ER stress is excessive or prolonged and these mechanisms fail to restore proteostasis, the UPR triggers the cell to undergo apoptosis. This review also examines the overlooked role of post-translational modifications and their roles in protein processing and effects on ER stress and the UPR. Finally, these effects are examined in the context of lung structure, function, and disease.