Degranulation of cystic fibrosis nasal polyp mast cells

Immunomodulation in Cystic Fibrosis: Why and How?

Cystic fibrosis (CF) lung disease is characterized by unconventional mechanisms of inflammation, implicating a chronic immune response dominated by innate immune cells. Historically, therapeutic development has focused on the mutated cystic fibrosis transmembrane conductance regulator (CFTR), leading to the discovery of small molecules aiming at modulating and potentiating the presence and activity of CFTR at the plasma membrane. However, treatment burden sustained by CF patients, side effects of current medications, and recent advances in other therapeutic areas have highlighted the need to develop novel disease targeting of the inflammatory component driving CF lung damage. Furthermore, current issues with standard treatment emphasize the need for directed lung therapies that could minimize systemic side effects. Here, we summarize current treatment used to target immune cells in the lungs, and highlight potential benefits and caveats of novel therapeutic strategies.

The Effect of Topical Corticosteroid on Basic Fibroblast Growth Factor in Nasal Polyp Tissue

Background

The etiology of nasal polyposis and pathophysiological mechanisms of polyp formation is still poorly understood. Experimental models have suggested that nasal polyp growth requires extracellular matrix formation and is associated with fibroblast proliferation. Intranasal corticosteroids appear to be useful in reducing nasal polypoid lesions and the likelihood of polyp recurrence after surgery. Basic fibroblast growth factor (bFGF) is a potent angiogenesis factor and is mitogenic for a wide range of cell types. We investigated the alteration of bFGF levels in nasal polyp tissue after administration of topical corticosteroid.

Methods

Nasal polyp tissues were obtained from 36 patients with diffuse nasal polyposis before and after topical nasal steroid treatment. As a topical nasal steroid mometasone furoate was given for 4 weeks in a dosage of 200 μg/day. The bFGF levels were measured by competitive enzyme immunoassay method.

Results

The mean levels of tissue bFGF, before and after topical nasal steroid treatment, were 1485 ± 826 ng/mg protein (range, 416–3434 ng/mg) and 1340 ± 749 ng/mg protein (range, 330–3288 ng/mg), respectively. The levels of bFGF in nasal polyps were significantly lower than those before treatment after administration of topical nasal steroid (p = 0.011).

Conclusion

Administration of topical nasal steroid decreases bFGF levels of nasal polyp. It may be suggested that one of the effects in diminishing the size of nasal polyps is by decreasing the bFGF.

Intranasal corticosteroids for nasal polyposis : biological rationale, efficacy, and safety

Nasal polyposis, occurring in about 2% of the general population, is the ultimate form of inflammation of the upper airways. For unknown reasons, polyps develop preferentially in subtypes of inflammatory diseases and are associated with perennial non-allergic rhinitis, asthma, intolerance of aspirin (acetylsalicylic acid)/NSAIDs, allergic fungal rhinosinusitis, cystic fibrosis, and primary ciliary dyskinesia. In contrast to common beliefs, IgE-mediated allergy does not seem to play an etiological role in nasal polyposis.The polyps originate from the mucosa around the clefts of the lateral nasal wall, especially in the region of the ostiomeatal complex. The factors that determine the localization of the disease to a few square centimeters of the airways are not known.Polyps are edematous bags covered by respiratory epithelium and contain very few nerves, blood vessels, and glands that have undergone cystic degeneration. They contain degranulated mast cells, have a very high concentration of histamine, and are characteristically infiltrated by eosinophils. These cells accumulate due to the release of proinflammatory cytokines (in particular, interleukin-5).Nasal polyposis is preceded by a prolonged history of rhinitis accompanied by severe and persistent nasal blockage; typically, the sense of smell is seriously impaired when polyps develop. The diagnosis is based on anterior rhinoscopy or, preferably, endoscopy.Nasal polyposis is medically treatable. Surgical treatment is carried out when medication fails. Intranasal corticosteroids reduce rhinitis symptoms, improve nasal breathing, reduce the size of polyps, and prevent, in part, their recurrence, but this treatment has little effect on the sense of smell. Intranasal corticosteroids can, as basic long-term therapy, be used alone in mild cases or together with systemic corticosteroids and/or surgery in severe cases. Systemic corticosteroids administered for 2-3 weeks have a beneficial effect on all observed symptoms and pathology, including the sense of smell. When nasal blockage is a problem in spite of medical treatment, surgery is recommended. Simple polypectomy can be performed, but endoscopic surgery is recommended in more severe and persistent cases.

Lipid droplets in activated mast cells - a significant source of triglyceride-derived arachidonic acid for eicosanoid production

Mast cells are potent effectors of immune reactions and key players in various inflammatory diseases such as atherosclerosis, asthma, and rheumatoid arthritis. The cellular defense response of mast cells represents a unique and powerful system, where external signals can trigger cell activation resulting in a stimulus-specific and highly coordinated release of a plethora of bioactive mediators. The arsenal of mediators encompasses preformed molecules stored in cytoplasmic secretory granules, as well as newly synthesized proteinaceous and lipid mediators. The release of mediators occurs in strict chronological order and requires proper coordination between the endomembrane system and various enzymatic machineries. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoid biosynthesis. Recent studies have revealed that not only phospholipids in mast cell membranes, but also triglycerides in mast cell lipid droplets are a substrate source for eicosanoid formation. The present review summarizes current knowledge about mast cell lipid droplet biology, and discusses expansions and challenges of traditional mechanistic models for eicosanoid production.

Pathogenesis and management of nasal polyposis in cystic fibrosis

Beginning in preschool age, during their lives, up to 50% of cystic fibrosis (CF) patients experience obstructing nasal polyposis (NP), which is rare in non-CF children. Pathogenetic factors of NP in general and especially in CF are still obscure. However, defective epithelial ion transport from mucosal glands plays a central role in CF, and viscous secretions impair mucociliary clearance, promoting chronic pathogen colonization and neutrophil-dominated chronic inflammation. Presently, CF-NP is not curable but can be clinically stabilized, though the large variety of proposed treatment modalities indicates a lack of standardization and of evidence of treatment efficacy. When conservative measures are exhausted, surgical intervention combining individually adapted endoscopic sinus surgery and supportive conservative treatment is performed. Topical steroids, approved as the gold standard for non-CF NP, may be beneficial, but they are discussed to be less effective in neutrophilic inflammation, and CF-specific antimicrobial and mucolytic therapy, as is true of all treatment modalities, urgently requires evaluation by controlled clinical trials within interdisciplinary networks.

Etiology of nasal polyps in cystic fibrosis: not a unimodal disease

OBJECTIVES

The objective was to determine whether the polyp subtypes observed in cystic fibrosis (CF)-related sinusitis were similar to those observed in non-CF-related sinusitis.

METHODS

Polyp and mucus samples were collected from CF patients who presented for sinus surgery. The polyps underwent histologic and cytochemical evaluation for the presence of lymphocyte cell populations and their respective cytokine markers. The mucus samples were evaluated for DNA content.

RESULTS

Of the polyps, 42% had an eosinophilic infiltrate, of which 80% had an additional mixed neutrophilic infiltrate. Of the remaining polyp samples, 42% did not have a granulocytic infiltrate, consistent with non-eosinophilic polyps. All samples had CD138-positive plasma cells. The mucus samples from the patients with CF showed higher extracellular DNA concentrations than did the mucus samples from patients with non-CF sinus disease.

CONCLUSIONS

Cystic fibrosis-related polyps demonstrated an eosinophil-based dichotomy similar to that of idiopathic non-CF-related polyps. Many also demonstrated neutrophilic infiltrate, indicating that chronic mucus stasis and infection complicate the disease. Agents capable of reducing extracellular DNA may help manage sinusitis in CF patients.

Activated MCTC mast cells infiltrate diseased lung areas in cystic fibrosis and idiopathic pulmonary fibrosis

Background

Although mast cells are regarded as important regulators of inflammation and tissue remodelling, their role in cystic fibrosis (CF) and idiopathic pulmonary fibrosis (IPF) has remained less studied. This study investigates the densities and phenotypes of mast cell populations in multiple lung compartments from patients with CF, IPF and never smoking controls.

Methods

Small airways, pulmonary vessels, and lung parenchyma were subjected to detailed immunohistochemical analyses using lungs from patients with CF (20 lung regions; 5 patients), IPF (21 regions; 7 patients) and controls (16 regions; 8 subjects). In each compartment the densities and distribution of MC_T and MC_TC mast cell populations were studied as well as the mast cell expression of IL-6 and TGF-β.

Results

In the alveolar parenchyma in lungs from patients with CF, MC_TC numbers increased in areas showing cellular inflammation or fibrosis compared to controls. Apart from an altered balance between MC_TC and MC_T cells, mast cell in CF lungs showed elevated expression of IL-6. In CF, a decrease in total mast cell numbers was observed in small airways and pulmonary vessels. In patients with IPF, a significantly elevated MC_TC density was present in fibrotic areas of the alveolar parenchyma with increased mast cell expression of TGF-β. The total mast cell density was unchanged in small airways and decreased in pulmonary vessels in IPF. Both the density, as well as the percentage, of MC_TC correlated positively with the degree of fibrosis. The increased density of MC_TC, as well as MC_TC expression of TGF-β, correlated negatively with patient lung function.

Conclusions

The present study reveals that altered mast cell populations, with increased numbers of MC_TC in diseased alveolar parenchyma, represents a significant component of the histopathology in CF and IPF. The mast cell alterations correlated to the degree of tissue remodelling and to lung function parameters. Further investigations of mast cells in these diseases may open for new therapeutic strategies.

Prevalence and histopathology of chronic polypoid sinusitis in pediatric patients with cystic fibrosis

BACKGROUND

Chronic sinusitis is almost invariably a feature of cystic fibrosis. However, data on the endoscopically confirmed prevalence of chronic polypoid sinusitis (CPS) and its histological features are limited.

METHODS

Single centre prospective observational study. Unselected pediatric CF patients (n=81; ≤ 18 years) were endoscopically assessed for the prevalence of CPS. Sixteen of these underwent sinus surgery. The surgically obtained sinus specimens were compared to sinus specimen of non-CF-patients undergoing sinus surgery (n=61), using conventional histology and immunohistochemistry.

RESULTS

The prevalence of endoscopically confirmed CPS increased with age from 19% in infants younger than six years reaching 45% in adolescents. In CF patients, histology typically showed dilated glandular ducts and a predominance of mucous glands. The number of plasma cells and mast cells but not of eosinophils was significantly elevated compared to non-CF patients.

CONCLUSION

Prevalence of CPS in pediatric CF patients increases with age. Our findings indicate that chronic bacterial infection rather than allergic mechanisms may forward this pathology.

Influence of Pseudomonas aeruginosa quorum sensing signal molecule N-(3-oxododecanoyl) homoserine lactone on mast cells

Quorum sensing system is a cell-to-cell communication system that plays a pivotal role in virulence expression in bacteria. Recent advances have demonstrated that the Pseudomonas aeruginosa quorum sensing molecule, N-3-oxododecanoyl homoserine lactone (3OC(12)-HSL), exerts effects on mammalian cells and modulates host immune response. Mast cells (MCs) are strategically located in the tissues that are constantly exposed to external stimulus. Therefore, it is very much possible that 3OC(12)-HSL may interact with MCs. Little is known, however, about specific effects of 3OC(12)-HSL on MCs. To address this, we investigated the influence of 3OC(12)-HSL on cell viability, apoptosis, intracellular calcium and cytokine release in MCs. We found that at high concentrations (100 microM), 3OC(12)-HSL inhibited proliferation and induced apoptosis in P815. The 3OC(12)-HSL treatment significantly increased intracellular calcium release in both P815 and HMC-1. We also observed that 3OC(12)-HSL-induced histamine release and degranulation in HMC-1 cells. Furthermore, 3OC(12)-HSL-induced IL-6 production at lower concentrations (6.25-12.5 microM) but steadily reduced IL-6 production at high concentration (50-100 muM). These data demonstrate that P. aeruginosa 3OC(12)-HSL affects MCs function.

Cystic fibrosis: ultrastructural changes of nasal mucosa

Cystic fibrosis (CF) is an inherited multisystemic disorder that results in a generalized dysfunction of exocrine glands. Besides chronic obstructive pulmonary diseases, chronic sinusitis, nasal polyposis and hypertrophy of the inferior turbinates with nasal airway obstruction are typical signs. Tissue samples of the inferior turbinates and nasal polyps were taken during nasal surgery from 21 children, ranging from 3 to 16 years of age. Light- and electron microscopical examination were carried out. Furthermore, specimens of nasal mucosa of patients without chronic inflammation as controls and specimens of duodenal mucosa of patients with CF were investigated. Under a thick layer of respiratory epithelium with a high proportion of goblet cells, the seromucous glands display abnormal morphological structures with wide mucous cells and cystic dilatation. The glandular cells show inhomogeneous glandular droplets in the supranuclear cell portion. The nucleus contains dispersed chromatin as a sign of increased activity and the structures of the Golgi apparatus are clearly detectable. Apart from investigations concerning nasal polyps in CF, studies on the different morphological changes of nasal mucosa at the electron microscopic level are rare. This histological study focuses on various morphological changes of nasal glands at the ultrastructural level in correlation with typical symptoms in CF. In addition, a comparison with electron microscopic findings of CF-enteropathies is proposed. These findings could help to bring information concerning new morphological aspects in the pathophysiology of patients with CF.

Differential regulation of cystic fibrosis transmembrane conductance regulator by interferon gamma in mast cells and epithelial cells

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent chloride channel in epithelial cells; recently, we identified it in mast cells. Previous work that we confirmed showed that interferon gamma (IFNgamma) down-regulated CFTR expression in epithelial cells (T84), but by contrast, we found that IFNgamma up-regulated CFTR mRNA and protein expression in rat and human mast cells. IFNgamma up-regulation of CFTR in mast cells was inhibited by p38 and extracellular signal-regulated kinase (ERK) kinase inhibitors but not a Janus tyrosine kinase (JAK)2 inhibitor, whereas in T84 cells IFNgamma-mediated down-regulation of CFTR was JAK2-dependent and ERK- and p38-independent. Furthermore, IFNgamma down-regulation of CFTR in T84 epithelial cells was STAT1-dependent, but up-regulation of CFTR in mast cells was STAT1-independent. Thus, differential regulatory pathways of CFTR expression in mast cells and epithelial cells exist that depend upon either p38/ERK or JAK/STAT pathways, respectively. Surprisingly, IFNgamma treatment of mast cells inhibited Cl(-) efflux, in contrast to up-regulation of CFTR/mRNA and protein expression. However, down-regulation of Cl(-) flux correlated with IFNgamma-mediated inhibition of mediator secretion. This and other work suggests that the effect of IFNgamma on CFTR expression in mast cells is important for their function.

Key role of mast cells and their major secretory products in inflammatory bowel disease

Historically, mast cells were known as a key cell type involved in type I hypersensitivity. Until last two decades, this cell type was recognized to be widely involved in a number of non-allergic diseases including inflammatory bowel disease (IBD). Markedly increased numbers of mast cells were observed in the mucosa of the ileum and colon of patients with IBD, which was accompanied by great changes of the content in mast cells such as dramatically increased expression of TNF-α, IL-16 and substance P. The evidence of mast cell degranulation was found in the wall of intestine from patients with IBD with immunohistochemistry technique. The highly elevated histamine and tryptase levels were detected in mucosa of patients with IBD, strongly suggesting that mast cell degranulation is involved in the pathogenesis of IBD. However, little is known of the actions of histamine, tryptase, chymase and carboxypeptidase in IBD. Over the last decade, heparin has been used to treat IBD in clinical practice. The low molecular weight heparin (LMWH) was effective as adjuvant therapy, and the patients showed good clinical and laboratory response with no serious adverse effects. The roles of PGD2, LTC4, PAF and mast cell cytokines in IBD were also discussed. Recently, a series of experiments with dispersed colon mast cells suggested there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. The hypothesis is that mast cell secretogogues induce mast cell degranulation, release histamine, then stimulate the adjacent mast cells or positively feedback to further stimulate its host mast cells through H₁ receptor. Whereas released tryptase acts similarly to histamine, but activates mast cells through its receptor PAR-2. The connections between current anti-IBD therapies or potential therapies for IBD with mast cells were discussed, implicating further that mast cell is a key cell type that is involved in the pathogenesis of IBD. In conclusion, while pathogenesis of IBD remains unclear, the key role of mast cells in this group of diseases demonstrated in the current review implicates strongly that IBD is a mast cell associated disease. Therefore, close attentions should be paid to the role of mast cells in IBD.

Nasal mucosal gene expression in patients with allergic rhinitis with and without nasal polyps

BACKGROUND

Nasal polyps are a common problem that is difficult to diagnose and treat, in part because the cause of nasal polyposis is unknown. Although information on the pathogenesis of polyposis is lacking, there are reports suggesting that a genetic predisposition underlies this disorder.

OBJECTIVE

We sought to better understand the basis of nasal polyposis associated with allergic rhinitis. We hypothesize that the expression of unique genes is associated with the nasal polyposis phenotype.

METHODS

We examined 12000 human genes transcribed in the nasal mucosa of patients with allergic rhinitis with and without nasal polyps. Biopsy specimens of the mucosa of patients with and without polyps were obtained after the patients refrained from the use of topical or systemic steroid therapy for 2 weeks.

RESULTS

Thirty-four genes were differentially expressed between the patient groups, including those for inflammatory molecules and putative growth factors. The greatest differential expression identified by the array analysis was for a group of genes associated with neoplasia, including mammaglobin, a gene transcribed 12-fold higher in patients with polyps compared with control patients with rhinitis alone. Quantitative RT-PCR confirmed this differential expression and documented that the number of mammaglobin mRNA copies is actually 64-fold greater in tissues of patients with polyps versus control patients. The specificity of mammaglobin protein expression was evaluated by means of immunohistochemistry, which showed specific staining in nasal polyp mucosal goblet cells only in patients with polyps.

CONCLUSION

These data suggest that nasal polyposis involves deregulated cell growth, using gene activation in some ways similar to a neoplasm. In addition, mammaglobin, a gene of unknown function associated with breast neoplasia, might be related to polyp growth.

Selective early production of CCL20, or macrophage inflammatory protein 3alpha, by human mast cells in response to Pseudomonas aeruginosa

Mast cells are important as sentinel cells in host defense against bacterial infection. Much of their effectiveness depends upon recruiting other immune cells; however, little is known about the mechanisms of this response. CCL20, also known as macrophage inflammatory protein-3alpha (MIP-3alpha), Exodus, and LARC, is a chemokine known to be a potent chemoattractant for immature dendritic cells and T cells. In this study, we examined the human mast cell production of both CCL20 and granulocyte-macrophage colony-stimulating factor (GM-CSF), a critical cytokine for innate immune responses in the lung, in response to Pseudomonas aeruginosa. Reverse transcription-PCR and Western blot analysis demonstrated that the human mast cells (HMC-1) express CCL20 mRNA and are able to produce a significant amount (32.4 ng/ml) of CCL20 protein following stimulation by calcium ionophore and phorbol myristate acetate. Importantly, P. aeruginosa potently stimulated CCL20 production in human cord blood-derived mast cells (CBMC), with production peaking at 6 h after stimulation. This time course of expression was distinct from that of GM-CSF, which peaked after 24 to 48 h. Significant CCL20 production did not occur following immunoglobulin E-mediated activation of CBMC under conditions which induced a substantial GM-CSF response. Interestingly, the CCL20 response of mast cells to P. aeruginosa was relatively resistant to inhibition by the corticosteroid dexamethasone, interleukin-10, or cyclosporine, while GM-CSF production was potently inhibited. However, P. aeruginosa-induced CCL20 production was blocked by the protein kinase C (PKC) inhibitor Ro 31-8220 and a PKC pseudosubstrate. These results support a role for human mast cells in the initiation of immune responses to P. aeruginosa infection.

Distinct pattern of immune cell population in the lung of human fetuses with cystic fibrosis

BACKGROUND

Airway inflammation and infection are early events in cystic fibrosis (CF) pathogenesis. The existence of an imbalance in the immune cell population of the CF fetal airway before infection remains completely unknown.

OBJECTIVE

The aim of this study was to determine whether early signs of inflammation are observed in CF airways during human fetal development.

METHODS

Tracheas and lungs were collected from 21 CF and 16 non-CF fetuses. In tissue sections, the numbers of neutrophils, mast cells, macrophages, and B and T lymphocytes were quantitatively analyzed by means of image cytometry. The presence of IL-4, IL-6, IL-8, IL-10, RANTES, IFN-gamma, TNF-alpha, and NF kappa B and its inhibitor I kappa B-alpha was qualitatively evaluated by immunofluorescent staining.

RESULTS

During fetal airway development, epithelial and glandular differentiation, as well as the distribution of inflammatory markers, was similar in CF and non-CF tissues. Significant differences between CF and non-CF fetal airways were observed only in the numbers of mast cells and macrophages. In the CF trachea, the mast cell number increased slowly but continuously, whereas in the non-CF trachea this number rapidly reached a plateau. In the CF lung, the macrophage number increased with time, whereas in the non-CF lung it decreased.

CONCLUSION

Although no intrinsic inflammation was demonstrated, we observed a distinct appearance of mast cells and macrophages in CF airways in comparison with non-CF airways during fetal development. These 2 cell populations were greater in CF airways at a late stage of fetal development, suggesting their possible involvement in the early onset of inflammation in CF infants.

In situ amplification of 5-lipoxygenase and 5-lipoxygenase-activating protein in allergic airway inflammation and inhibition by leukotriene blockade

Leukotrienes are important mediators of the eosinophilic influx and mucus hypersecretion in the lungs in a murine model of asthma. We used in situ PCR in this model of human asthma to detect lung mRNA for 5-lipoxygenase (5-LO) and 5-LO-activating protein (FLAP), key proteins necessary for leukotriene synthesis. Lung tissue was obtained on day 28 from mice treated with i.p. (days 0 and 14) and intranasal (days 14, 25, 26, and 27) OVA or saline. After fixation, the tissue sections underwent protease- and RNase-free DNase digestion, before in situ RT-PCR using target-specific cDNA amplification. 5-LO and FLAP-specific mRNA was visualized by a digoxigenin detection system, and positive cells were analyzed by morphometry. 5-LO and FLAP-specific mRNA and protein were associated primarily with eosinophils and alveolar macrophages in the airways and pulmonary blood vessels in OVA-sensitized/challenged mice. 5-LO and FLAP protein expression increased on a per-cell basis in alveolar macrophages of OVA-treated mice compared with saline controls. Pulmonary blood vessel endothelial cells were also positive for 5-LO, FLAP mRNA, and protein. 5-LO inhibition significantly decreased 5-LO and FLAP-specific mRNA and protein expression in the lung inflammatory cells and endothelial cells. These studies demonstrate a marked increase in key 5-LO pathway proteins in the allergic lung inflammatory response and an important immunomodulatory effect of leukotriene blockade to decrease 5-LO and FLAP gene expression.

Expression of basic fibroblast growth factor in nasal polyps

Basic fibroblast growth factor (bFGF) is a polypeptide that is mitogenic for a wide variety of cell types. We used Northern blot analysis and immunohistochemistry to determine if bFGF is expressed in the nasal polyp tissue; bFGF messenger RNA was detectable in the polyps examined by Northern blot analysis. Strong immunostaining for bFGF was found in blood vessels and along the basement membrane of the epithelial cell layers. Basal epithelial cells and some infiltrating mononuclear cells also stained for bFGF. Proliferating cell nuclear antigen colocalized with bFGF to basal epithelial cells, endothelial cells, and areas of focal epithelial metaplasia. The polyp tissue was double-labeled with a mouse monoclonal antitryptase, a specific mast cell marker, and anti-bFGF. A significant number (65% +/- 19%) of the bFGF-positive mononuclear cells in the polyp tissues were positive for tryptase. These findings suggest that bFGF may contribute to the endothelial and epithelial proliferation in nasal polyp tissues and that mast cells are one source of this growth factor.

The importance of leukotrienes in airway inflammation in a mouse model of asthma

Inhalation of antigen in immunized mice induces an infiltration of eosinophils into the airways and increased bronchial hyperreactivity as are observed in human asthma. We employed a model of late-phase allergic pulmonary inflammation in mice to address the role of leukotrienes (LT) in mediating airway eosinophilia and hyperreactivity to methacholine. Allergen intranasal challenge in OVA-sensitized mice induced LTB4 and LTC4 release into the airspace, widespread mucus occlusion of the airways, leukocytic infiltration of the airway tissue and broncho-alveolar lavage fluid that was predominantly eosinophils, and bronchial hyperreactivity to methacholine. Specific inhibitors of 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP) blocked airway mucus release and infiltration by eosinophils indicating a key role for leukotrienes in these features of allergic pulmonary inflammation. The role of leukotrienes or eosinophils in mediating airway hyperresponsiveness to aeroallergen could not be established, however, in this murine model.

Expression of vascular permeability factor (VPF/VEGF) messenger RNA by plasma cells: possible involvement in the development of edema in chronic inflammation

Edema occurs in some types of chronic inflammation such as nasal polyps, uterine cervical polyps and gastric hyperplastic polyps. However, the factors or cellular components involved in the development of edema in chronic inflammation remain to be clarified. Recently, the gene encoding vascular permeability factor (VPF) or vascular endothelial growth factor (VEGF) and the genes encoding its receptors (kinase insert domain-containing receptor (KDR) and fms-like tyrosine kinase-1 [fit-1]) have been cloned. VPF/VEGF induces vascular hyperpermeability and vascular endothelial proliferation through KDR or fit-1 receptors. As there is a possibility that VPF/VEGF may play a role in the development of edema in chronic inflammation, we examined the messenger (m) RNA expression of VPF/VEGF and its receptors in nasal polyp tissues, which is an example of chronic inflammation with remarkable edema. Using northern blotting, all nasal polyp tissues examined expressed mRNA of VPF/VEGF and KDR. In situ hybridization revealed that VPF/VEGF mRNA-expressing cells were scattered in the edematous stroma of nasal polyps. In the adjacent sections, these cells showed the morphological features of plasma cells and expressed mRNA of immunoglobulin light chains. Human B cell leukemia and plasmacytoma cell lines expressed VPF/VEGF mRNA but human mast-cell leukemia and T cell leukemia cell lines did not. The alternatively spliced pattern of VPF/VEGF transcripts observed in nasal polyp tissues was consistent with that in plasmacytoma cell lines. Taken together, the VPF/VEGF mRNA-expressing cells in nasal polyps appeared to be plasma cells, suggesting that plasma cells may play an important role in the development of edema in chronic inflammation through the production of VPF/VEGF.

Lung mast cells increase in number and degranulate during pulmonary artery occlusion/reperfusion injury in dogs

The role of mast cells in pulmonary artery occlusion/reperfusion injury was examined. Lung tissue was obtained from dogs after left pulmonary artery occlusion for 48 h (n = 5) or after similar occlusion followed by 4 h of reperfusion (n = 11). By light microscopy and morphometry, the percentage of mast cells increased 2.4-fold (p < 0.05) in nonoccluded right lungs and 2.9-fold (p < 0.05) in occluded left lungs without reperfusion compared with that in control lungs. After reperfusion, the occluded left lung contained 1.8-fold (p < 0.05) as many mast cells as the nonoccluded right lung and 4.2-fold (p < 0.05) more than that in control lungs. Hydroxyurea did not significantly affect the number of mast cells observed in the right and left lungs after ischemia/reperfusion; 39.8% and 54.4% of the mast cells were degranulated in nonoccluded right lung and occluded left lung preparations, respectively, after left pulmonary artery ischemia/reperfusion (each, p < 0.05 compared with control lungs). The release of eicosanoids into the airways during ischemia/reperfusion injury was also examined. Thromboxane B2 and leukotriene B4 were markedly increased (each, p < 0.05 compared with that in control lungs) in bronchial lavage fluids from both nonoccluded and occluded lungs compared with sham-occluded lungs. Thus, mast cell recruitment and degranulation may play a role in lung ischemia/reperfusion injury.