Shizuko Kagawa

Cyclooxygenase-2/Prostaglandin D2/CRTH2 Pathway Mediates Double-Stranded RNA-Induced Enhancement of Allergic Airway Inflammation

Respiratory RNA viruses responsible for the common cold often worsen airway inflammation and bronchial responsiveness, two characteristic features of human asthma. We studied the effects of dsRNA, a nucleotide synthesized during viral replication, on airway inflammation and bronchial hyperresponsiveness in murine models of asthma. Intratracheal instillation of poly I:C, a synthetic dsRNA, increased the airway eosinophilia and enhanced bronchial hyperresponsiveness to methacholine in OVA-sensitized, exposed rats. These changes were associated with induction of cyclooxygenase-2 (COX-2) expression and COX-2-dependent PGD2 synthesis in the lungs, particularly in alveolar macrophages. The direct intratracheal instillation of PGD2 enhanced the eosinophilic inflammation in OVA-exposed animals, whereas pretreatment with a dual antagonist against the PGD2 receptor-(CRTH2) and the thromboxane A2 receptor, but not with a thromboxane A2 receptor-specific antagonist, nearly completely eliminated the dsRNA-induced worsening of airway inflammation and bronchial hyperresponsiveness. CRTH2-deficient mice had the same degree of allergen-induced airway eosinophilia as wild-type mice, but they did not exhibit a dsRNA-induced increase in eosinophil accumulation. Our data demonstrate that COX-2-dependent production of PGD2 followed by eosinophil recruitment into the airways via a CRTH2 receptor are the major pathogenetic factors responsible for the dsRNA-induced enhancement of airway inflammation and responsiveness.

CRTH2 Is A Critical Regulator of Neutrophil Migration and Resistance to Polymicrobial Sepsis

Although arachidonic acid cascade has been shown to be involved in sepsis, little is known about the role of PGD2 and its newly found receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), on the septic response. Severe sepsis is associated with the failure of neutrophil migration. To investigate whether CRTH2 influences neutrophil recruitment and the lethality during sepsis, sepsis was induced by cecal ligation and puncture (CLP) surgery in mice. CRTH2 knockout (CRTH2−/−) mice were highly resistant to CLP-induced sepsis, which was associated with lower bacterial load and lower production of TNF-α, IL-6, and CCL3. IL-10, an anti-inflammatory cytokine, was higher in CRTH2−/− mice, blunting CLP-induced lethality in CRTH2−/− mice. Neutrophil accumulation in the peritoneum was more pronounced after CLP in CRTH2−/− mice, which was associated with higher CXCR2 levels in circulating neutrophils. Furthermore, sepsis caused a decrease in the level of acetylation of histone H3, an activation mark, at the CXCR2 promoter in wild-type neutrophils, suggesting that CXCR2 expression levels are epigenetically regulated. Finally, both pharmacological depletion of neutrophils and inhibition of CXCR2 abrogated the survival benefit in CRTH2−/− mice. These results demonstrate that genetic ablation of CRTH2 improved impaired neutrophil migration and survival during severe sepsis, which was mechanistically associated with epigenetic-mediated CXCR2 expression. Thus, CRTH2 is a potential therapeutic target for polymicrobial sepsis.

Induction of Mucin and MUC5AC Expression by the Protease Activity of Aspergillus fumigatus in Airway Epithelial Cells

Allergic bronchopulmonary mycosis, characterized by excessive mucus secretion, airflow limitation, bronchiectasis, and peripheral blood eosinophilia, is predominantly caused by a fungal pathogen, Aspergillus fumigatus. Using DNA microarray analysis of NCI-H292 cells, a human bronchial epithelial cell line, stimulated with fungal extracts from A. fumigatus, Alternaria alternata, or Penicillium notatum, we identified a mucin-related MUC5AC as one of the genes, the expression of which was selectively induced by A. fumigatus. Quantitative RT-PCR, ELISA, and histochemical analyses confirmed an induction of mucin and MUC5AC expression by A. fumigatus extracts or the culture supernatant of live microorganisms in NCI-H292 cells and primary cultures of airway epithelial cells. The expression of MUC5AC induced by A. fumigatus extracts diminished in the presence of neutralizing Abs or of inhibitors of the epidermal growth factor receptor or its ligand, TGF-α. We also found that A. fumigatus extracts activated the TNF-α–converting enzyme (TACE), critical for the cleavage of membrane-bound pro–TGF-α, and its inhibition with low-molecular weight inhibitors or small interfering RNA suppressed the expression of MUC5AC. The protease activity of A. fumigatus extracts was greater than that of other fungal extracts, and treatment with a serine protease inhibitor, but not with a cysteine protease inhibitor, eliminated its ability to activate TACE or induce the expression of MUC5AC mRNA in NCI-H292. In conclusion, the prominent serine protease activity of A. fumigatus, which caused the overproduction of mucus by the bronchial epithelium via the activation of the TACE/TGF-α/epidermal growth factor receptor pathway, may be a pathogenetic mechanism of allergic bronchopulmonary mycosis.

Characterization of the cell of origin and propagation potential of the fibroblast growth factor 9-induced mouse model of lung adenocarcinoma

Fibroblast growth factor 9 (FGF9) is essential for lung development and is highly expressed in a subset of human lung adenocarcinomas. We recently described a mouse model in which FGF9 expression in the lung epithelium caused proliferation of the airway epithelium at the terminal bronchioles and led to rapid development of adenocarcinoma. Here, we used this model to characterize the effects of prolonged FGF9 induction on the proximal and distal lung epithelia, and examined the propagation potential of FGF9‐induced lung tumours. We showed that prolonged FGF9 over‐expression in the lung resulted in the development of adenocarcinomas arising from both alveolar type II and airway secretory cells in the lung parenchyma and airways, respectively. We found that tumour cells harboured tumour‐propagating cells that were able to form secondary tumours in recipient mice, regardless of FGF9 expression. However, the highest degree of tumour propagation was observed when unfractionated tumour cells were co‐administered with autologous, tumour‐associated mesenchymal cells. Although the initiation of lung adenocarcinomas was dependent on activation of the FGF9–FGF receptor 3 (FGFR3) signalling axis, maintenance and propagation of the tumour was independent of this signalling. Activation of an alternative FGF–FGFR axis and the interaction with tumour stromal cells is likely to be responsible for the development of this independence. This study demonstrates the complex role of FGF–FGFR signalling in the initiation, growth and propagation of lung cancer. Our findings suggest that analysing the expressions of FGF–FGFRs in human lung cancer will be a useful tool for guiding customized therapy. Copyright

Strain-Specific Phenotypes of Airway Inflammation and Bronchial Hyperresponsiveness Induced by Epicutaneous Allergen Sensitization in BALB/c and C57BL/6 Mice

Background: Allergen sensitization through a disrupted skin barrier appears to play a prominent role in the development of atopic diseases, including allergic asthma. The role of the genetic background in immunological and physiological phenotypes induced by epicutaneous sensitization is undetermined. Methods: BALB/c and C57BL/6 mice were sensitized either epicutaneously by patch application of ovalbumin (OVA) or systemically by intraperitoneal injection of OVA with alum before exposure to aerosolized OVA. The concentrations of OVA-specific immunoglobulin in serum and cytokines in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay. The severity of airway inflammation was evaluated by cell counts in BALF, and bronchial responsiveness to methacholine was measured by the flexiVent system. Results: The production of OVA-specific IgG1 and IgE was greater in the epicutaneously sensitized BALB/c than C57BL/6 mice. In contrast, both eosinophilic airway inflammation and bronchial responsiveness to methacholine were more prominent in the C57BL/6 than in the BALB/c mice. The concentrations of interleukin-4 increased significantly in the BALF from C57BL/6 mice only. No between-strain differences were observed after intraperitoneal sensitization. Conclusions: The C57BL/6 mouse is a more appropriate model than the BALB/c mouse to study the relationship between skin barrier dysfunction and the pathogenesis of allergic asthma.

Role of prostaglandin D2 receptor CRTH2 in sustained eosinophil accumulation in the airways of mice with chronic asthma.

The prostaglandin D2 (PGD2)/CRTH2 pathway is important for eosinophil trafficking in vitro; however, genetic deficiency of CRTH2 does not suppress in vivo eosinophilic airway inflammation in acute models of asthma, and the role of CRTH2 in the pathogenesis of asthma is still ambiguous. Therefore, in the present study we explored whether the PGD2/CRTH2 pathway could affect the phenotypes of chronic asthma. Either CRTH2-deficient (CRTH2–/–) or wild-type mice were sensitized and exposed to ovalbumin (OVA) for 3 days (acute model) or 6 weeks (chronic model). While the magnitude of the acute eosinophilic inflammation was equivalent between CRTH2–/– and wild-type mice, the number of inflammatory cells and eosinophils in bronchoalveolar lavage fluid after chronic OVA exposure was significantly reduced in CRTH2–/– mice (18.0 ± 2.6 × 104 cells and 2.0 ± 0.5 × 104 cells) compared to wild-type mice (27.9 ± 2.5 × 104 cells and 6.8 ± 1.1 × 104 cells, p < 0.001). On the contrary, no difference was observed between CRTH2–/– and wild-type mice in terms of airway hyperresponsiveness or remodeling (goblet cell hyperplasia) in the chronic model of asthma. In conclusion, CRTH2 that mediates PGD2 activity is essential for sustained eosinophilic inflammation in the airways, and its antagonists could exert an anti-inflammatory effect in chronic asthma.

Dual Role of Interleukin-23 in Epicutaneously-Sensitized Asthma in Mice

BACKGROUND Interleukin (IL)-23/Th17 axis plays an important role in the pathophysiology of asthma and eczema, however, there are some conflicting data about the effects of this system on allergic airway inflammation. In the present study, we aim to dissect the spatiotemporal differences in the roles of IL-23 in an epicutaneously-sensitized asthma model of mice. METHODS C57BL/6 mice were sensitized to ovalbumin (OVA) by patch application on the skin, followed by airway exposure to aerosolized OVA. During sensitization and/or challenge phase, either a specific neutralizing antibody (Ab) against IL-23 or control IgG was injected intraperitoneally. On days 1 and 8 after the final OVA exposure, airway inflammation and responsiveness to methacholine, immunoglobulin levels in serum, and cytokine release from splenocytes were evaluated. Skin Il23a mRNA levels were evaluated with quantitative RT-PCR. RESULTS Patch application time-dependently increased the expression of Il23a mRNA expression in the skin. Treatment with the anti-IL-23 Ab during sensitization phase alone significantly reduced the number of eosinophils in bronchoalveolar lavage fluids and peribronchial spaces after allergen challenge compared with treatment with control IgG. Anti-IL-23 Ab also reduced serum levels of OVA-specific IgG1. In contrast, treatment with the anti-IL-23 Ab during the challenge phase alone rather exacerbated airway hyperresponsiveness to methacholine with little effects on airway eosinophilia or serum IgG1 levels. CONCLUSIONS IL-23 expressed in the skin during the sensitization phase plays an essential role in the development of allergic phenotypes, whereas IL-23 in the airways during the challenge phase suppresses airway hyperresponsiveness.

Variant CD44 expression is enriching for a cell population with cancer stem cell-like characteristics in human lung adenocarcinoma

Background: Preliminary studies have identified cancer stem cells (CSCs) in various cancers and there are several ongoing clinical studies targeting these cells. CD44 (standard or variant isoforms) and/or aldehyde dehydrogenase (ALDH) expression is the most commonly used markers for the identification of CSCs. The goal of the current study was to examine the ability of CD44v, either alone or in combination with ALDH, to identify CSCs within human lung cancer cells lines. Methods: We examined several lung adenocarcinoma cell lines for the ability of CD44v and/or ALDH expression to enrich for cells with CSC characteristics such as in vitro differential proliferation rate, chemotherapeutic-resistance, tumorsphere formation, and in vivo tumorigenicity. We also compared their in vivo secondary tumor formation, and histological characteristics of their xenograft tumors, and examined their expression of PD-L1, EGFR, xCT, and reactive oxygen species (ROS). Results: Both CD44vhigh/ALDHhigh and CD44vhigh/ALDHlow cells were enriched in cells with CSC characteristics, with the CD44vhigh/ALDHlow cells being more proliferative and more resistant to chemotherapeutics, whereas CD44vhigh/ALDHhigh cells were more efficient in forming tumorspheres in vitro, in making primary xenograft tumors, and in propagating secondary tumors in vivo. Applying stricter sorting gates to select for cells with the highest CD44v/ALDH expression caused the CD44vhigh/ALDHlow cells to lose their high proliferation rates and chemotherapeutic resistance ability, but enriched for the tumorsphere-forming cells among the CD44vhigh/ALDHhigh and CD44vhigh/ALDHlow cells. CD44vhigh expression was associated with PD-L1 and xCT expression in both H1650 and HCC827 cells. This association was not modified by ALDH expression in the H1650 cell line. However, in the HCC827 cell line, ALDH expression was negatively associated with PD-L1 and positively associated with xCT expression. Conclusion: Lung adenocarcinoma cells with high CD44v expression are enriched for CSCs. Addition of ALDH as an enrichment marker bestowed some CSCs characteristics to CD44vhigh/ALDHlow cells and others to CD44vhigh/ALDHhigh cells. We propose that lung adenocarcinoma contains different CSCs, each of them endowed with different CSC characteristics.

Intermittent Exposure to Cigarette Smoke Increases Lung Tumors and the Severity of Emphysema More than Continuous Exposure

&NA; Lung cancer and chronic obstructive pulmonary disease are leading causes of morbidity and mortality worldwide, and cigarette smoking is a main risk factor for both. The presence of emphysema, an irreversible lung disease, further raises the risk of lung cancer in patients with chronic obstructive pulmonary disease. The mechanisms involved in smoke‐induced tumorigenesis and emphysema are not fully understood, attributable to a lack of appropriate animal models. Here, we optimized a model of cigarette smoke (CS)‐induced lung cancer and emphysema in A/J mice treated with 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone, a potent carcinogen. We investigated whether variations in CS exposure patterns with the same total amount and duration of exposure affect tumorigenesis and/or development of emphysema. Continuous CS exposure for 3 months significantly suppressed 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone‐induced development of adenomas and adenocarcinomas; however, emphysema independently developed during this period. Surprisingly, intermittent CS exposure increased the severity of emphysema and resulted in a higher incidence of adenocarcinomas. Furthermore, intermittent CS exposure elicited a marked increase in M2‐polarized macrophages within and near the developed tumors. By employing a CS exposure protocol with repeated cycles of cessation and relapse, we provide evidence that intermittent CS exposure enhances tumorigenesis and emphysema progression more than that of continuous CS exposure.

Using Micro-computed Tomography for the Assessment of Tumor Development and Follow-up of Response to Treatment in a Mouse Model of Lung Cancer.

Lung cancer is the most lethal cancer in the world. Intensive research is ongoing worldwide to identify new therapies for lung cancer. Several mouse models of lung cancer are being used to study the mechanism of cancer development and to experiment with various therapeutic strategies. However, the absence of a real-time technique to identify the development of tumor nodules in mice lungs and to monitor the changes in their size in response to various experimental and therapeutic interventions hampers the ability to obtain an accurate description of the course of the disease and its timely response to treatments. In this study, a method using a micro-computed tomography (CT) scanner for the detection of the development of lung tumors in a mouse model of lung adenocarcinoma is described. Next, we show that monthly follow-up with micro-CT can identify dynamic changes in the lung tumor, such as the appearance of additional nodules, increase in the size of previously detected nodules, and decrease in the size or complete resolution of nodules in response to treatment. Finally, the accuracy of this real-time assessment method was confirmed with end-point histological quantification. This technique paves the way for planning and conducting more complex experiments on lung cancer animal models, and it enables us to better understand the mechanisms of carcinogenesis and the effects of different treatment modalities while saving time and resources.