CXCR2 regulates respiratory syncytial virus-induced airway hyperreactivity and mucus overproduction

Murine cytomegalovirus influences Foxj1 expression, ciliogenesis, and mucus plugging in mice with allergic airway disease

We have followed throughout time the development of allergic airway disease (AAD) in both uninfected mice and mice infected intranasally with murine cytomegalovirus (MCMV). Histological evaluation of lung tissue from uninfected mice with AAD demonstrated mucus plugging after 14 and 21 days of ovalbumin-aerosol challenge, with resolution of mucus plugging occurring by 42 days. In MCMV/AAD mice, mucus plugging was observed after 7 days of ovalbumin-aerosol challenge and remained present at 42 days. The level of interleukin-13 in bronchoalveolar lavage fluid from MCMV/AAD mice was decreased compared with AAD mice and was accompanied by increased levels of interferon-gamma. Levels of Muc5A/C, Muc5B, or Muc2 mucin mRNA in the lungs of MCMV/AAD mice were not elevated compared with AAD mice. MCMV was able to infect the airway epithelium, resulting in decreased expression of Foxj1, a transcription factor critical for ciliogenesis, and a loss of ciliated epithelial cells. In addition, an increase in the number of epithelial cells staining positive for periodic acid-Schiff was observed in MCMV/AAD airways. Together, these findings suggest that MCMV infection of the airway epithelium enhances goblet cell metaplasia and diminishes efficient mucociliary clearance in mice with AAD, resulting in increased mucus plugging.

Notch ligand Delta-like 4 regulates disease pathogenesis during respiratory viral infections by modulating Th2 cytokines

Recent data have indicated that an important instructive class of signals regulating the immune response is Notch ligand–mediated activation. Using quantitative polymerase chain reaction, we observed that only Delta-like 4 (dll4) was up-regulated on bone marrow–derived dendritic cells after respiratory syncytial virus (RSV) infection, and that it was dependent on MyD88-mediated pathways. Using a polyclonal antibody specific for dll4, the development of RSV-induced disease was examined. Animals treated with anti-dll4 had substantially increased airway hyperresponsiveness compared with control antibody-treated animals. When the lymphocytic lung infiltrate was examined, a significant increase in total CD4⁺ T cells and activated (perforin⁺) CD8⁺ T cells was observed. Isolated lung CD4⁺ T cells demonstrated significant increases in Th2-type cytokines and a decrease in interferon γ, demonstrating an association with increased disease pathogenesis. Parellel in vitro studies examining the integrated role of dll4 with interleukin-12 demonstrated that, together, both of these instructive signals direct the immune response toward a more competent, less pathogenic antiviral response. These data demonstrate that dll4-mediated Notch activation is one regulator of antiviral immunity.

Decreased expression of human aquaporin-5 correlated with mucus overproduction in airways of chronic obstructive pulmonary disease

AIM

To investigate the relationship between aquaporin-5 (AQP5) expression and mucus overproduction in the airways of Chinese patients with chronic obstructive pulmonary disease (COPD) and the correlation with pulmonary function change.

METHODS

Bronchial tissues were obtained from fiberoptic bronchoscopy and bronchial biopsy in West China Hospital from April to July 2004. Twenty-five patients were diagnosed as COPD patients, and another 20 were diagnosed as the control patients. The expressions of AQP5, mucin 5AC (MUC5AC), and mucin in bronchial tissues were detected by semiquantitative RT-PCR, in situ hybridization, and immunohistochemical and alcian blue-periodic acid-Schiff (AB-PAS) staining, respectively.

RESULTS

Compared with the control group, an attenuated expression of AQP5 was detected throughout the bronchial tissues from patients with COPD (P<0.01), but no difference existed in the lung tissues (P>0.05). Simultaneously, increased staining of MUC5AC and mucus in submucosal glands were noted (P<0.01, respectively). Smoking attenuated the expressions of AQP5 and increased the staining of MUC5AC and mucus in submucosal glands in the COPD groups (P<0.01), while there were no significant differences observed in the control group (P>0.05). The decreased expression of AQP5 mRNA was correlated with forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) (r=0.60, P<0.01), FEV1% predicted value (r=0.60, P<0.01), maximal expiratory flow in 50% vital capacity (V50) % predicted value (r=0.55, P<0.01), and maximal expiratory flow in 25% vital capacity (V25) % predicted value (r=0.45, P<0.01). The decreased expression was negatively correlated with MUC5AC mRNA of the epithelium airways (r=-0.45, P<0.01) and the AB-PAS-stained area of submucosal glands (r=-0.61, P<0.01). The upregulation of MUC5AC mRNA correlated with the positively AB-PAS-stained area of submucosal glands and correlated negatively with FEV1/FVC (r=-0.53; P<0.01), FEV1% predicted value (r=-0.53; P<0.01), V50% predicted value (r=-0.48; P<0.01), and V25% predicted value (r=-0.43; P<0.01).

CONCLUSION

The attenuated gene expression of AQP5 existed in the airways of Chinese COPD patients, which was complicated by mucus hypersecretion. The decreased expression of AQP5 mRNA may be related to the severity of airflow obstruction.

Chemokines and their receptors in respiratory disease: a therapeutic target for respiratory syncytial virus infection

Cell recruitment is a multistep process orchestrated by chemokines and their receptors. The chemokine/receptor system is central to many inflammatory diseases, making it a key target for therapeutic intervention. Despite complexity and redundancy within the system, effective antagonists are in development and undergoing clinical trials, for example, maraviroc, for use in HIV treatment. Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in infants, with global annual infection estimated at 64 million people. Current treatment is purely supportive, with no effective vaccine available. RSV pathology is partly due to excessive airway inflammation. Evidence is growing for a key role for chemokine receptors. Receptor blockade may therefore provide a feasible therapeutic option to inhibit RSV-induced inflammation and thereby reduce disease severity.

Time-dependent airway epithelial and inflammatory cell responses induced by influenza virus A/PR/8/34 in C57BL/6 mice

The present study examines the kinetics of airway epithelial remodeling and inflammation in the airways of C57BL/6J mice infected with influenza virus A/PR/8/34 (PR8). Mice were intranasally instilled with 50 plaque forming units (pfu) of virus or its respective vehicle, saline, and then were sacrificed at 3, 7, 10, 15, or 21 days postinfection (dpi). PR8 treatment resulted in airway epithelial cell regeneration as suggested by proliferating cell nuclear antigen (PCNA) positive staining at 7 and 10 dpi and mucous cell metaplasia (MCM) evident at 10, 15, and 21 dpi. PR8 treatment resulted in a classic pattern of inflammation observed in bronchoalveolar lavage fluid (BALF), in which neutrophils peaked at 3 and 7 dpi and monocytes, lymphocytes, and eosinophils peaked at 10 dpi before returning to background levels of detection. Chemokine (MCP-1) and cytokine (IL-6, TNF-alpha, IFN-gamma, IL-5, IL-4, and IL-9) levels peaked at 7 dpi in BALF. IL-13 levels were unaffected by PR8 treatment. Concurrent with inflammation, MUC5AC gene expression was markedly increased by PR8 treatment at 7 dpi. Collectively, the results of this study indicate that the onset of MCM in airway epithelium occurs during the remodeling process and persists after the inflammatory response has diminished.

A Novel, Orally Active CXCR1/2 Receptor Antagonist, Sch527123, Inhibits Neutrophil Recruitment, Mucus Production, and Goblet Cell Hyperplasia in Animal Models of Pulmonary Inflammation

Sch527123 [2-hydroxy-N,N-dimethyl-3-[[2-[[1(R)-(5-methyl-2-furanyl)propyl]amino]-3,4-dioxo-1-cyclobuten-1-yl]amino]ben-zamide] is a potent, selective antagonist of the human CXCR1 and CXCR2 receptors (Gonsiorek et al., 2007). Here we describe its pharmacologic properties at rodent CXCR2 and at the CXCR1 and CXCR2 receptors in the cynomolgus monkey, as well as its in vivo activity in models demonstrating prominent pulmonary neutrophilia, goblet cell hyperplasia, and mucus production. Sch527123 bound with high affinity to the CXCR2 receptors of mouse (K(d) = 0.20 nM), rat (K(d) = 0.20 nM), and cynomolgus monkey (K(d) = 0.08 nM) and was a potent antagonist of CXCR2-mediated chemotaxis (IC(50) approximately 3-6 nM). In contrast, Sch527123 bound to cynomolgus CXCR1 with lesser affinity (K(d) = 41 nM) and weakly inhibited cynomolgus CXCR1-mediated chemotaxis (IC(50) approximately 1000 nM). Oral treatment with Sch527123 blocked pulmonary neutrophilia (ED(50) = 1.2 mg/kg) and goblet cell hyperplasia (32-38% inhibition at 1-3 mg/kg) in mice following the intranasal lipopolysaccharide (LPS) administration. In rats, Sch527123 suppressed the pulmonary neutrophilia (ED(50) = 1.8 mg/kg) and increase in bronchoalveolar lavage (BAL) mucin content (ED(50) =<0.1 mg/kg) induced by intratracheal (i.t.) LPS. Sch527123 also suppressed the pulmonary neutrophilia (ED(50) = 1.3 mg/kg), goblet cell hyperplasia (ED(50) = 0.7 mg/kg), and increase in BAL mucin content (ED(50) = <1 mg/kg) in rats after i.t. administration of vanadium pentoxide. In cynomolgus monkeys, Sch527123 reduced the pulmonary neutrophilia induced by repeat bronchoscopy and lavage (ED(50) = 0.3 mg/kg). Therefore, Sch527123 may offer benefit for the treatment of inflammatory lung disorders in which pulmonary neutrophilia and mucus hypersecretion are important components of the underlying disease pathology.

MyD88-Mediated Instructive Signals in Dendritic Cells Regulate Pulmonary Immune Responses during Respiratory Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of respiratory disease in infants worldwide. The induction of innate immunity and the establishment of adaptive immune responses are influenced by the recognition of pathogen-associated molecular patterns by TLRs. One of the primary pathways for TLR activation is by MyD88 adapter protein signaling. The present studies indicate that MyD88 deficiency profoundly impacts the pulmonary environment in RSV-infected mice characterized by the accumulation of eosinophils and augmented mucus production. Although there was little difference in CD4 T cell accumulation, there was also a significant decrease in conventional dendritic cells recruitment to the lungs of MyD88(-/-) mice. The exacerbation of RSV pathophysiology in MyD88(-/-) mice was associated with an enhanced Th2 cytokine profile that contributed to an inappropriate immune response. Furthermore, bone marrow-derived dendritic cells (BMDC) isolated from MyD88(-/-) mice were incapable of producing two important Th1 instructive signals, IL-12 and delta-like4, upon RSV infection. Although MyD88(-/-) BMDCs infected with RSV did up-regulate costimulatory molecules, they did not up-regulate class II as efficiently and stimulated less IFN-gamma from CD4(+) T cells in vitro compared with wild-type BMDCs. Finally, adoptive transfer of C57BL/6 BMDCs into MyD88(-/-) mice reconstituted Th1 immune responses in vivo, whereas transfer of MyD88(-/-) BMDCs into wild-type mice skewed the RSV responses toward a Th2 phenotype. Taken together, our data indicate that MyD88-mediated pathways are essential for the least pathogenic responses to this viral pathogen through the regulation of important Th1-associated instructive signals.

Mechanisms of mucin production by rhinovirus infection in cultured human airway epithelial cells

Mucus hypersecretion relates to exacerbations of bronchial asthma and chronic obstructive pulmonary disease (COPD) caused by rhinovirus (RV) infection. We examined the mechanisms of RV infection-induced mucin production in human tracheal surface epithelial cells and submucosal gland cells. RV14 up-regulated the mRNA expression of MUC2, MUC3, MUC5AC, MUC5B and MUC6, and increased MUC5AC and total mucin concentration in supernatants and lysates of the surface cells. An inhibitor of the nuclear factor kappaB caffeic acid phenylethyl ester, inhibitors of selective p44/42 mitogen-activated protein kinase-kinase PD98059 and U0126, and a selective Src inhibitor PP1 attenuated MUC5AC mRNA expression, and secretion and production of MUC5AC and total mucin glycoprotein in the surface cells. In the gland cells, RV14 also increased mRNA expression of MUC2, MUC5AC, MUC5B and MUC7, and the inhibitors attenuated the secretion of total mucin glycoprotein. Src-related p44/42 mitogen-activated protein kinase pathway may be associated with RV-induced mucin hypersecretion in human airways.

Differential immune responses and pulmonary pathophysiology are induced by two different strains of respiratory syncytial virus

In this study we performed comparisons of pulmonary responses between two different respiratory syncytial virus (RSV) antigenic subgroup A strains, A2 and Line 19. Line 19 strain induced significant dose-responsive airway hyperreactivity (AHR) in BALB/c mice at days 6 and 9 after infection, whereas the A2 strain induced no AHR at any dose. Histological examination indicated that A2 induced no goblet cell hyper/metaplasia, whereas the Line 19 induced goblet cell expansion and significant increases in gob5 and MUC5AC mRNA and protein levels in vivo. When examining cytokine responses, A2 strain induced significant interleukin (IL)-10 expression, whereas Line 19 strain induced significant IL-13 expression. When IL-13-/- mice were infected with Line 19 RSV, the AHR responses were abrogated along with gob5 gene expression. There was little difference in viral titer throughout the infection between the line 19- and A2-infected mice. However, the A2 strain grew to significantly higher titers than the Line 19 strain in HEp-2 cells in vitro. Thus, RSV Line 19-induced airway dysfunction does not correlate with viral load in vivo. These data demonstrate that different RSV strains of the same antigenic subgroup can elicit differential immune responses that impact the phenotypic expression of RSV-induced illness.

Pathogenesis of respiratory syncytial virus infection in the murine model

There is a wide spectrum of illness caused by respiratory syncytial virus (RSV) infection that is caused in large part by host-related factors, such as age of the patient and degree of host immunocompetency. Although the vast majority of persons infected with RSV experience symptoms of mild upper respiratory tract infection, in some people these infections cause significant morbidity and are sometimes fatal. Although a great deal of investigation in both humans and animals has explained the timing and tropism of RSV infection and the general principles by which the immune system responds to this infection, at present we only partially understand the disparity in illness severity that can occur. This article briefly reviews the clinical sequelae of RSV infection and then focuses on the mechanisms of viral pathogenesis.

Gob-5 contributes to goblet cell hyperplasia and modulates pulmonary tissue inflammation

Gob-5 is a member of the calcium-activated chloride channel family and has been associated with allergic response in mouse models of pulmonary inflammation. Gene expression of Gob-5 has been shown to be induced in allergic airways and has been strongly associated with mucin gene regulation and goblet cell hyperplasia. We investigated the physiologic role of Gob-5 in murine models of pulmonary inflammation using mice deficient in Gob-5. After sensitization and aerosol challenge with ovalbumin (OVA), Gob-5 knockout mice exhibit significantly increased bronchoalveolar lavage (BAL) inflammation as compared with wild-type controls. The augmented inflammation in BAL consisted predominantly of neutrophils. Examination of perivascular inflammation revealed that tissue inflammation was decreased in OVA-challenged Gob-5-/- mice. OVA-challenged Gob-5 knockout mice also had decreased goblet cell hyperplasia as well as decreased mucus production. These mice also had decreased airway hypersensitivity after cholinergic provocation with methacholine. Gob-5 knockout mice were also challenged via intranasal LPS, a TLR-4 agonist. Gob-5-/- mice responded with increased neutrophilic BAL inflammation and decreased perivascular tissue inflammation as compared with wild-type controls. There was little effect on goblet cell hyperplasia and mucus production after LPS challenge. These observations reinforce findings that associate Gob-5 with goblet cell hyperplasia and mucus production in the allergic immune response, but also implicate Gob-5 in the regulation of tissue inflammation in the innate immune response.

Deletion of TLR3 alters the pulmonary immune environment and mucus production during respiratory syncytial virus infection

The detection of a viral infection by pattern recognition receptors (PAMPs) is an integral part of antiviral immunity. In these studies we have investigated the role of TLR3, which recognizes dsRNA, in Respiratory Syncytial virus (RSV) infection using B6 background mice with a TLR3 deletion. Although we observed no changes in viral growth, we did find that TLR3-/- mice demonstrated significant increases in mucus production in the airways of RSV-infected mice. The qualitative assessment was observed by examining differentially stained lungs, followed by immunohistochemical staining for gob5, a mucus-associated protein. The histopathologic observations were verified using quantitative gene expression analyses examining gob5 gene expression. Changes in pulmonary mucus production were accompanied by an increase in pulmonary IL-13 as well as IL-5 expression and eosinophils in the airways of TLR3-/- mice. Examining leukocytes in the airway indicated an accumulation of eosinophils in TLR3-/- mice, but not wild-type mice, after RSV infection. Isolated lung draining lymph node cells from TLR3-/- mice produced significant increases in Th2-type cytokines, IL-5, and IL-13, compared with wild-type TLR3+/+ mice only after RSV infection. To demonstrate a causative link, we depleted TLR3-/- mice of IL-13 during RSV infection and found that mucus and gob5 expression in the lungs was attenuated. Together, these studies highlight that although TLR3 may not be required for viral clearance, it is necessary to maintain the proper immune environment in the lung to avoid developing pathologic symptoms of disease.

Deletion of CCR1 attenuates pathophysiologic responses during respiratory syncytial virus infection

The role of chemokines in chronic inflammatory responses are central to the recruitment of particular subsets of leukocytes. In the present studies, we have examined the role of CCR1 in the developing pathogenesis of respiratory syncytial virus (RSV) in the lungs of infected BALB/c mice. Although we did not observe significant differences in clearance of RSV, we were able to identify decreased pathophysiologic responses in CCR1(-/-) mice. CCR1(-/-) mice displayed a significant reduction in both airway hyperresponsiveness and mucus production that corresponded to significant increases in IFN-gamma and CXCL10. The goblet cell hyper/metaplasia and the expression of mucus-associated gene, gob5, were correspondingly reduced in the CCR1(-/-) mice. In addition, the Western blot analysis of gob5 protein indicated that CCR1(-/-) mice have virtually no up-regulation of the protein at day 6 of infection compared with wild-type-infected mice. Results from bone marrow chimeric mice indicated that partial reconstitution of the response could be achieved in the CCR1(-/-) mice with wild-type bone marrow cells, suggesting that these cells have a role in the response. However, transplanting of CCR1(-/-) bone marrow into wild-type mice did demonstrate an incomplete deficit in RSV-induced responses, indicating that CCR1(+) parenchymal cells may also play a significant role in the process. Thus, the presence of CCR1 appears to have a significant role in the development of detrimental airway physiologic responses during RSV infection. These data suggest that CCR1 may be a potential target during detrimental pulmonary responses during infection.

A closer look at chemokines and their role in asthmatic responses

Inflammatory cell recruitment is a hallmark phenomenon of all inflammatory diseases, including allergic asthma. In allergy and asthma, recruitment of inflammatory cells such as T cells, dendritic cells, mast cells, eosinophils and neutrophils, is mediated via a number of chemokines and their receptors. Not only are chemokines involved in recruitment of these cells, they also play a role in activation and differentiation of inflammatory cells, among others, by selectively activating Th1 or Th2 cells or by effects on epithelial or endothelial cells. Binding of chemokines with their receptors has been demonstrated to be highly promiscuous and the subsequent activation pattern on effector cells is very heterogeneous, which has lead to confusion and has complicated research in this field. Nonetheless, chemokines and their receptors are important potential therapeutical targets in allergy and asthma because of their central role in cell recruitment and activation during inflammation.

Agents against cytokine synthesis or receptors

Various cytokines play a critical role in pathophysiology of chronic inflammatory lung diseases including asthma and chronic obstructive pulmonary disease (COPD). The increasing evidence of the involvement of these cytokines in the development of airway inflammation raises the possibility that these cytokines may become the novel promising therapeutic targets. Studies concerning the inhibition of interleukin (IL)-4 have been discontinued despite promising early results in asthma. Although blocking antibody against IL-5 markedly reduces the infiltration of eosinophils in peripheral blood and airway, it does not seem to be effective in symptomatic asthma, while blocking IL-13 might be more effective. On the contrary, anti-inflammatory cytokines themselves such as IL-10, IL-12, IL-18, IL-23 and interferon-gamma may have a therapeutic potential. Inhibition of TNF-alpha may also be useful in severe asthma or COPD. Many chemokines are also involved in the inflammatory response of asthma and COPD through the recruitment of inflammatory cells. Several small molecule inhibitors of chemokine receptors are now in development for the treatment of asthma and COPD. Antibodies that block IL-8 reduce neutrophilic inflammation. Chemokine CC3 receptor antagonists, which block eosinophil chemotaxis, are now in clinical development for asthma therapy. As many cytokines are involved in the pathophysiology of inflammatory lung diseases, inhibitory agents of the synthesis of multiple cytokines may be more useful tools. Several such agents are now in clinical development.

Cigarette smoke suppresses Th1 cytokine production and increases RSV expression in a neonatal model

Respiratory syncytial virus (RSV) infects approximately 90% of young children by the age of 2 yr, with peak rates occurring during 2-6 mo of age. Exposure to side-stream cigarette smoke (SS) may increase the incidence or manifestation of an RSV infection. We hypothesized that exposure to SS would alter the subsequent immune response to RSV infection in neonatal mice. BALB/c mice were exposed to air or 1.5 mg/m3 of SS from day (d) 1 up to 35 d of age. A subset was intranasally infected with 4x10(4) PFU of RSV/g body wt on d 7 and rechallenged at 28 d of age. Immune responses were assessed on d 4 and 7 after RSV rechallenge. Both air- and SS-exposed mice responded to RSV rechallenge with neutrophilia and decreased Clara cell secretory protein levels within the lung. However, an increase in bronchoalveolar lavage fluid eosinophils, in addition to reduced levels of Th1 cytokines (IFN-gamma and IL-12), decreased lung tissue inflammation, and decreased mucus production was observed in SS-exposed mice compared with air-exposed mice after RSV rechallenge. Ultimately changes in cytokine and inflammatory responses due to SS exposure likely contributed to increased viral gene expression. These results suggest that SS exposure plays a significant role in shaping the neonatal response to RSV infection.

A novel flow cytometric assay of human whole blood neutrophil and monocyte CD11b levels: upregulation by chemokines is related to receptor expression, comparison with neutrophil shape change, and effects of a chemokine receptor (CXCR2) antagonist

RATIONALE

Smokers who develop chronic obstructive pulmonary disease (COPD) have amplified inflammation within their lungs, involving selective tissue accumulation of neutrophils, macrophages and CD8+ T cells. CD11b (Mac-1, alphaMbeta(2)-integrin) is both a complement receptor (CR3) and a cell adhesion molecule present on the surface of peripheral blood leukocytes, and undergoes rapid surface upregulation from preformed cytoplasmic stores on activation. Cellular activation can also trigger chemotaxis and shape change, the activation itself being caused by the binding of chemokines to cell surface receptors.

METHODS

We developed a method of whole blood flow cytometry to measure neutrophil and monocyte CD11b upregulation on CD16+ and CD14+ cells, employing staining with the nuclear dye LDS-751 immediately before flow cytometry. In addition we assessed neutrophil shape change by modified gated autofluorescence with forward scatter (GAFS), this being correlated with chemotactic responses.

RESULTS

In smokers with COPD there was a lower maximal shape change for neutrophils in response to CXCL8 (IL-8) in comparison to healthy smokers (p=0.025), and a trend for lower expression of CD11b and shape change in response to CXCL1 (GRO-alpha). Neutrophils were found to predominantly express chemokine receptors CXCR1 and CXCR2 and respond to CXCL8 with CD11b upregulation, while monocytes express more CCR2 and upregulate CD11b preferentially to CCL2 (MCP-1). A CXCR2 antagonist (SB-656933) was found to inhibit neutrophil CD11b upregulation (IC50=260.7nM) and shape change (IC50=310.5nM) in COPD patients.

CONCLUSIONS

Neutrophils and monocytes participate in inflammatory processes in a range of diseases. These whole blood assays can be employed to monitor activity in disease and perform in vitro and ex vivo assessment of chemokine receptor (CXCR) antagonists.

Mediators of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major and increasing global health problem that is now a leading cause of death. COPD is associated with a chronic inflammatory response, predominantly in small airways and lung parenchyma, which is characterized by increased numbers of macrophages, neutrophils, and T lymphocytes. The inflammatory mediators involved in COPD have not been clearly defined, in contrast to asthma, but it is now apparent that many lipid mediators, inflammatory peptides, reactive oxygen and nitrogen species, chemokines, cytokines, and growth factors are involved in orchestrating the complex inflammatory process that results in small airway fibrosis and alveolar destruction. Many proteases are also involved in the inflammatory process and are responsible for the destruction of elastin fibers in the lung parenchyma, which is the hallmark of emphysema. The identification of inflammatory mediators and understanding their interactions is important for the development of anti-inflammatory treatments for this important disease.

Differential role for TLR3 in respiratory syncytial virus-induced chemokine expression

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in young infants worldwide. Previous studies have reported that the induction of interleukin-8/CXCL8 and RANTES/CCL5 correlates with disease severity in humans. The production of these chemokines is elicited by viral replication and is NF-kappaB dependent. RSV, a negative-sense single-stranded RNA virus, requires full-length positive-sense RNA for synthesis of new viral RNA. The aim of our studies was to investigate whether active viral replication by RSV could evoke chemokine production through TLR3-mediated signaling pathways. In TLR3-transfected HEK 293 cells, live RSV preferentially activated chemokines in both a time- and dose-dependent manner compared to vector controls. RSV was also shown to upregulate TLR3 in human lung fibroblasts and epithelial cells (MRC-5 and A549). Targeting the expression of TLR3 with small interfering RNA decreased synthesis of IP-10/CXCL10 and CCL5 but did not significantly reduce levels of CXCL8. Blocking the expression of the adapter protein MyD88 established a role for MyD88 in CXCL8 production, whereas CCL5 synthesis was found to be MyD88 independent. Production of CCL5 by RSV was induced directly through TLR3 signaling pathways and did not require interferon (IFN) signaling through the IFN-alpha/beta receptor. TLR3 did not affect viral replication, since equivalent viral loads were recovered from RSV-infected cells despite altered TLR3 expression. Taken together, our studies indicate that TLR3 mediates inflammatory cytokine and chemokine production in RSV-infected epithelial cells.

Association of the hCLCA1 gene with childhood and adult asthma

Asthma is caused by bronchial inflammation. This inflammation involves mucus overproduction and hypersecretion. Recently, a mouse model of asthma showed that gob-5 is involved in the pathogenesis of asthma. The gob-5 gene is involved in mucus secretion and its expression is upregulated upon antigen attack in sensitized mice. The observation suggests that human homologue of gob-5, hCLCA1 (human calcium-dependent chloride channel-1), may be involved in human disease. We screened for single-nucleotide polymorphisms (SNPs) in hCLCA1 in the Japanese population. We identified eight SNPs, and performed association studies using 384 child patients with asthma, 480 adult patients with asthma, and 672 controls. In haplotype analysis, we found a different haplotype distribution pattern between controls and childhood asthma (P<0.0001) and between controls and adult asthma (P=0.0031). We identified a high-risk haplotype (CATCAAGT haplotype; P=0.0014) and a low-risk haplotype (TGCCAAGT haplotype; P=0.00010) in cases of childhood asthma. In diplotype analysis, patients who had the CATCAAGT haplotype showed a higher risk for childhood asthma than those who did not (P=0.0011). Individuals who had the TGCCAAGT haplotype showed a lower risk for childhood asthma than those who did not (P<0.0001). Our data suggested that variation of the hCLCA1 gene affects patients' susceptibility for asthma.

Characterization of cigarette smoke-induced inflammatory and mucus hypersecretory changes in rat lung and the role of CXCR2 ligands in mediating this effect

Repetitive, acute inflammatory insults elicited by cigarette smoke (CS) contribute to the development of chronic obstructive pulmonary disease (COPD), a disorder associated with lung inflammation and mucus hypersecretion. Presently, there is a poor understanding of the acute inflammatory mechanisms involved in this process. The aims of this study were to develop an acute model to investigate temporal inflammatory changes occurring after CS exposure. Rats were exposed to whole body CS (once daily) generated from filtered research cigarettes. Initial studies indicated the generation of a neutrophilic/mucus hypersecreting lung phenotype in <4 days. Subsequent studies demonstrated that just two exposures to CS (15 h apart) elicited a robust inflammatory/mucus hypersecretory phenotype that was used to investigate mechanisms driving this response. Cytokine-induced neutrophil chemoattractants (CINCs) 1-3, the rat growth-related oncogene-alpha family homologs, and IL-1beta demonstrated time-dependent increases in lung tissue or lavage fluid over the 24-h period following CS exposure. The temporal changes in the neutrophil chemokines, CINCs 1-3, mirrored increases in neutrophil infiltration, indicative of a role in neutrophil migration. In addition, a specific CXCR2 antagonist, SB-332235, effectively inhibited CS-induced neutrophilia in a dose-dependent manner, supporting this conclusion. This modeling of the response of the rat airways to acute CS exposure indicates 1) as few as two exposures to CS will induce a phenotype with similarities to COPD and 2) a novel role for CINCs in the generation of this response. These observations represent a paradigm for the study of acute, repetitive lung insults that contribute to the development of chronic disease.

Interleukin-1beta causes pulmonary inflammation, emphysema, and airway remodeling in the adult murine lung

The production of the inflammatory cytokine interleukin (IL)-1 is increased in lungs of patients with chronic obstructive pulmonary disease (COPD) or asthma. To characterize the in vivo actions of IL-1 in the lung, transgenic mice were generated in which human IL-1beta was expressed in the lung epithelium with a doxycycline-inducible system controlled by the rat Clara cell secretory protein (CCSP) promoter. Induction of IL-1beta expression in the lungs of adult mice caused pulmonary inflammation characterized by neutrophil and macrophage infiltrates. IL-1beta caused distal airspace enlargement, consistent with emphysema. IL-1beta caused disruption of elastin fibers in alveolar septa and fibrosis in airway walls and in the pleura. IL-1beta increased the thickness of conducting airways, enhanced mucin production, and caused lymphocytic aggregates in the airways. Decreased immunostaining for the winged helix transcription factor FOXA2 was associated with goblet cell hyperplasia in IL-1beta-expressing mice. The production of the neutrophil attractant CXC chemokines KC (CXCL1) and MIP-2 (CXCL2), and of matrix metalloproteases MMP-9 and MMP-12, was increased by IL-1beta. Chronic production of IL-1beta in respiratory epithelial cells of adult mice causes lung inflammation, enlargement of distal airspaces, mucus metaplasia, and airway fibrosis in the adult mouse.

Chemokine receptors: understanding their role in asthmatic disease

The incidence, prevalence, and severity of asthma have been increasing steadily in recent years. Prophylactic treatment of this disease and of episodic asthmatic flares is aimed at preventing excessive inflammation in lung tissue and airways. Because chemokines and chemokine receptors are critical mediators of leukocyte trafficking and recruitment, there is the potential to pharmaceutically target these proteins to regulate inflammation. Asthma-associated inflammation is characterized by the infiltration of eosinophils and T helper type 2 cells. Early studies investigated the role of chemokine receptors, which have been shown to predominate on these cell populations.

Respiratory syncytial virus in allergic lung inflammation increases Muc5ac and gob-5

Respiratory syncytial virus (RSV) is associated with wheezing and childhood asthma. We previously reported that RSV infection prolongs methacholine-induced airway hyperresponsiveness in ovalbumin (OVA)-sensitized mice. In addition, allergically sensitized RSV-infected (OVA/RSV) mice had more abundant airway epithelial mucus production compared with OVA mice 14 days after infection, whereas there was almost no mucus in mice that were only RSV infected. We hypothesized that this increased mucus was associated with mucosal expression of Muc5ac, a mucus gene expression in airways, and gob-5, a member of the Ca(2)(+)-activated chloride channel family. By histochemical analysis, we found that there was significantly increased staining for gob-5 and Muc5ac in the airways of OVA/RSV mice compared with either OVA mice or allergically sensitized mice that were challenged with inactivated RSV, and virtually no detectable staining in the RSV group. These findings were confirmed by Western blot analysis. The increased mucus expression in the OVA/RSV group was associated with increased lung levels of interleukin-17, a factor known to stimulate airway mucin gene expression. The impact of virus infection combined with allergic inflammation on mucus production may partially explain the more severe disease and airway hyperresponsiveness associated with RSV in the setting of atopy.

Bronchiolar disorders

Bronchiolar abnormalities are relatively common and occur in a variety of clinical settings. Various histopathologic patterns of bronchiolar injury have been described and have led to confusing nomenclature with redundant and overlapping terms. Some histopathologic patterns of bronchiolar disease may be relatively unique to a specific clinical context but others are nonspecific with respect to either etiology or pathogenesis. Herein, we present a scheme separating (1) those disorders in which the bronchiolar disease is the predominant abnormality (primary bronchiolar disorders) from (2) parenchymal disorders with prominent bronchiolar involvement and (3) bronchiolar involvement in large airway diseases. Primary bronchiolar disorders include constrictive bronchiolitis (obliterative bronchiolitis, bronchiolitis obliterans), acute bronchiolitis, diffuse panbronchiolitis, respiratory bronchiolitis, mineral dust airway disease, follicular bronchiolitis, and a few other rare variants. Prominent bronchiolar involvement may be seen in several interstitial lung diseases, including hypersensitivity pneumonitis, respiratory bronchiolitis-associated interstitial lung disease, cryptogenic organizing pneumonia (idiopathic bronchiolitis obliterans organizing pneumonia), and pulmonary Langerhans' cell histiocytosis. Large airway diseases that commonly involve bronchioles include bronchiectasis, asthma, and chronic obstructive pulmonary disease. The clinical relevance of a bronchiolar lesion is best determined by identifying the underlying histopathologic pattern and assessing the correlative clinico-physiologic-radiologic context.

Clara cell secretory protein modulates lung inflammatory and immune responses to respiratory syncytial virus infection

Clara cell secretory protein (CCSP) has been shown to have anti-inflammatory and immunomodulatory functions in the lung. Respiratory syncytial virus (RSV) is the most common cause of respiratory infection in infants and young children. RSV usually infects small airways and likely interacts with the Clara cells of bronchioles. To determine a possible role for CCSP during acute RSV infection, CCSP-deficient (CCSP(-/-)) and wild-type (WT) mice were intratracheally infected with RSV and the lung inflammatory and immune responses to RSV infection were assessed. RSV-F gene expression was increased in the lungs of CCSP(-/-) mice as compared with WT mice following RSV infection, consistent with increased viral persistence. Lung inflammation was significantly increased in CCSP(-/-) mice as compared with WT mice after infection. Moreover, although the levels of Th1 cytokines were similar, the levels of Th2 cytokines and neutrophil chemokines were increased in the lungs of CCSP(-/-) mice following infection. Physiologic endpoints of exacerbated lung disease, specifically airway reactivity and mucus production, were increased in CCSP(-/-) mice after RSV infection. Importantly, restoration of CCSP in the airways of CCSP(-/-) mice abrogated the increased viral persistence, lung inflammation, and airway reactivity. These findings suggest a role for CCSP and Clara cells in regulating lung inflammatory and immune responses to RSV infection.