Effect of human eosinophil major basic protein on ion transport in dog tracheal epithelium

Eosinophils in the Gastrointestinal Tract: Key Contributors to Neuro-Immune Crosstalk and Potential Implications in Disorders of Brain-Gut Interaction

Eosinophils are innate immune granulocytes actively involved in defensive responses and in local and systemic inflammatory processes. Beyond these effector roles, eosinophils are fundamental to maintaining homeostasis in the tissues they reside. Gastrointestinal eosinophils modulate barrier function and mucosal immunity and promote tissue development through their direct communication with almost every cellular component. This is possible thanks to the variety of receptors they express and the bioactive molecules they store and release, including cytotoxic proteins, cytokines, growth factors, and neuropeptides and neurotrophines. A growing body of evidence points to the eosinophil as a key neuro-immune player in the regulation of gastrointestinal function, with potential implications in pathophysiological processes. Eosinophil–neuron interactions are facilitated by chemotaxis and adhesion molecules, and the mediators released may have excitatory or inhibitory effects on each cell type, with physiological consequences dependent on the type of innervation involved. Of special interest are the disorders of the brain–gut interaction (DBGIs), mainly functional dyspepsia (FD) and irritable bowel syndrome (IBS), in which mucosal eosinophilia and eosinophil activation have been identified. In this review, we summarize the main roles of gastrointestinal eosinophils in supporting gut homeostasis and the evidence available on eosinophil–neuron interactions to bring new insights that support the fundamental role of this neuro-immune crosstalk in maintaining gut health and contributing to the pathophysiology of DBGIs.

Expression and Distribution of Aquaporin-1 in Nasal Polyps: Does it have any Significance in Edema Formation?

Background

The aim of this study was to investigate the expression of Aquaporin 1 (AQP1) and AQP4 in polyp tissue.

Methods

Nasal polyps were obtained from 34 patients with nasal polyposis during endoscopic sinus surgery. Bullous middle turbinates with normal-appearing mucosa of 10 patients were used as controls. Expression of AQP1 and AQP4 water channels were determined by immunohistochemical methods.

Results

AQP1 has been found to be expressed in fibroblasts located in polyp tissue, especially in the subepithelial area, periphery of seromucous glands, and endothelial cells of venules.

Conclusion

We have established a high expression of AQP1 water channels in nasal polyp tissue and have suggested two mechanisms to explain this finding. Increased AQP1 expression may be a cause or a consequence of edema formation. Thus, additional studies are needed to elucidate the true mechanism underlying this relationship.

Budesonide treatment of patients with collagenous colitis restores normal eosinophil and T-cell activity in the colon

BACKGROUND

The aim of this study was to assess the activity of eosinophils, neutrophils, and CD4+ as well as CD8+ T-cells in 11 patients with active collagenous colitis (CC) before and after 8 weeks of budesonide treatment (9 mg once daily) compared to 10 healthy individuals.

METHODS

Clinical symptoms were recorded and intestinal biopsy samples were taken and analyzed by flow cytometry. Eosinophils with a high surface expression of CD44 and low CD9 expression were classified as activated. Neutrophil activity was assessed by their expression of CD66b, and CD69 was used as an activation marker for T-cells.

RESULTS

All patients responded to the treatment. The eosinophils in active CC showed increased activity compared to controls. The activity was back to control levels after treatment. Neutrophils were not activated in CC patients before or after treatment. CD8+ T-cells from untreated CC patients had a lower activity than controls, and a tendency of lower activity was observed on CD4+ T-cells. After treatment, the activity was increased on both types of T-cells and was not different from controls.

CONCLUSIONS

In the present study we demonstrated that the inflammation in CC is characterized by activated eosinophils but there is no neutrophil activity. CD4+ and CD8+ T-cells are increased in numbers in active CC but, surprisingly, they had a lower grade of activity than in control subjects. The major finding of this study is that budesonide treatment restores the normal activation of eosinophils and T-cells, accompanied by clinical remission.

Changes in ion transport in inflammatory disease

Ion transport is essential for maintenance of transmembranous and transcellular electric potential, fluid transport and cellular volume. Disturbance of ion transport has been associated with cellular dysfunction, intra and extracellular edema and abnormalities of epithelial surface liquid volume. There is increasing evidence that conditions characterized by an intense local or systemic inflammatory response are associated with abnormal ion transport. This abnormal ion transport has been involved in the pathogenesis of conditions like hypovolemia due to fluid losses, hyponatremia and hypokalemia in diarrhoeal diseases, electrolyte abnormalities in pyelonephritis of early infancy, septicemia induced pulmonary edema, and in hypersecretion and edema induced by inflammatory reactions of the mucosa of the upper respiratory tract. Components of membranous ion transport systems, which have been shown to undergo a change in function during an inflammatory response include the sodium potassium ATPase, the epithelial sodium channel, the Cystic Fibrosis Transmembrane Conductance Regulator and calcium activated chloride channels and the sodium potassium chloride co-transporter. Inflammatory mediators, which influence ion transport are tumor necrosis factor, gamma interferon, interleukins, transforming growth factor, leukotrienes and bradykinin. They trigger the release of specific messengers like prostaglandins, nitric oxide and histamine which alter ion transport system function through specific receptors, intracellular second messengers and protein kinases. This review summarizes data on in vivo measurements of changes in ion transport in acute inflammatory conditions and in vitro studies, which have explored the underlying mechanisms. Potential interventions directed at a correction of the observed abnormalities are discussed.

The protease-activated receptor2 (PAR2)-prostaglandin E2-prostanoid EP receptor axis: a potential bronchoprotective unit in the respiratory tract?

Protease-activated receptor2 (PAR2) is a subtype of G protein-coupled receptor that is widely expressed within the respiratory tract. Stimulation of PAR2 by proteases such as trypsin and tryptase, or by small peptidic activators induces a complex array of effects within the airways. One such PAR2-mediated effect by basal airway epithelial cells is the generation of prostaglandin E2. Prostaglandin E2 produces a raft of anti-inflammatory effects within the airways, principally through the activation of the prostanoid EP2 and EP3 receptor subtypes. This article reviews the PAR2-prostaglandin E2-prostanoid EP receptor axis and discusses approaches through which its activation may provide beneficial effects in respiratory disease.

Update on the molecular biology of nasal polyposis

The definition of CRS with and without nasal polyposis continues to evolve. It may require an understanding of a broader range of etiologies and pathogenesis than bacterial or viral infection. One must know whether the inflammation is of infectious or noninfectious origin. Therapeutic options will include pharmacotherapies and surgery. The pharmacotherapeutic approach will include antibiotics, systemic and topical steroids, possibly antifungals, novel anti-inflammatory therapies such as the use of antibodies directed against inflammatory cytokines and antileukotrienes, and perhaps low-dose macrolide therapy. In the case of massive nasal polyposis, modern surgical techniques will have to be performed before these therapeutic options will be possible. Finally, the use of topical diuretics such as amiloride and furosemide has been studied and the initial responses seem to be encouraging.

Eosinophils alter colonic epithelial barrier function: role for major basic protein

Mucosal eosinophils increase in a number of gastrointestinal diseases that are often associated with altered epithelial barrier function, including food allergic enteropathies and inflammatory bowel diseases. Although eosinophils are known to secrete biologically active mediators including granule proteins, their role in gastrointestinal diseases is uncertain. The aim of this study was to determine the impact of eosinophils on intestinal barrier function. Epithelial barrier function was determined in a coculture of eosinophils and T84 epithelial cells and in a murine model of T helper (Th) type 2-mediated colitis. Coculture conditions resulted in decreased transepithelial resistance (TER) and increased transepithelial flux. Cell-free coculture supernatants contained a > or =5-kDa soluble factor that also diminished TER; these supernatants contained the eosinophil-granule proteins major basic protein (MBP) and eosinophil-derived neurotoxin (EDN). T84 barrier function decreased significantly when basolateral surfaces were exposed to native human MBP but not EDN. Additional studies identified downregulation of the tight junctional molecule occludin as at least one mechanism for MBP action. MBP-null mice were protected from inflammation associated with oxazolone colitis compared with wild-type mice. In conclusion, MBP decreases epithelial barrier function and in this manner contributes to the pathogenesis of inflammatory bowel diseases.

Superantigen hypothesis for the early development of chronic hyperplastic sinusitis with massive nasal polyposis

PURPOSE OF REVIEW

The pathogenesis, pathophysiology, and immunobiology of chronic hyperplastic sinusitis with massive nasal polyposis are starting to become unraveled. Allergy, viral infection, bacterial infection, fungal infection, and environmental pollution have all been suggested as possible initial triggers that may upregulate inflammation of the lateral wall of the nose to develop nasal polyposis. The purpose of this review is to present data from our laboratory that suggest that one of the possible early events in the development of inflammation of the lateral wall of the nose in chronic hyperplastic sinusitis with massive nasal polyposis is the production of exotoxins from Staphylococcus aureus. The exotoxins may act as superantigens and cause activation and clonal expansion of lymphocytes with specific Vbeta regions, resulting in massive cytokine production.

RECENT FINDINGS

Recent published studies suggest that S. aureus is the most common organism isolated from the mucus adjacent to massive nasal polyposis. Staphylococci produce exotoxins. These exotoxins, sometimes known as enterotoxins, include SEA, SEB, and TSST-1. These exotoxins are capable of acting as superantigens and therefore, reacting with T lymphocytes with specific Vbetas in the lateral wall of the nose. Thereafter, it is possible that these lymphocytes are stimulated to produce both TH1 and TH2 cytokines, which have also been demonstrated in the nasal polyp. The consequence of these findings may be the upregulation and increased survival of eosinophils in the nasal polyp.

SUMMARY

Staphylococcus aureus is present in the mucin adjacent to nasal polyps in about 60 to 70% of cases of massive nasal polyposis. These organism, as studied up to the present, always produce exotoxins, which may act as superantigens, causing activation and clonal expansion of lymphocytes with specific Vbeta region in the lateral wall of the nose. The present review suggests that activation of these lymphocytes produce both TH1 and TH2 cytokines. The potential damage to the nasal mucosa from eosinophils is briefly discussed. Theoretically, topical antibiotics to suppress the colonization of S. aureus may be a logical approach to downregulate the production of superantigen in the lateral wall of the nose after appropriate endoscopic sinus surgery.

Neutrophil elastase stimulates human airway epithelial cells to produce PGE2 through activation of p44/42 MAPK and upregulation of cyclooxygenase-2

The responses of airway epithelium following exposure to neutrophil elastase (NE) were investigated. Human bronchial epithelial cells were explanted on insert surfaces of a modified air-liquid interface culture system to which NE was added to stimulate epithelial cells. PGE2 release significantly increased within 10 min of incubation with NE and peaked 3 h after NE (20 microg/ml) stimulation. This action required proteolytic activity as alpha1-antitrypsin blocked NE-induced PGE2 release. The production of PGE2 was also inhibited by indomethacin; a selective cyclooxygenase (COX)-2 inhibitor, celecoxib; and dexamethasone. Moreover, the mRNA expression for COX-2 relative to that for a housekeeping gene was approximately eightfold that of the unstimulated cells. Dexamethasone inhibited COX-2 gene transcription. We further observed that NE-induced PGE2 release involved activation of p44/42, but not p38, MAP kinases. Such p44/42 MAP kinases were rapidly phosphorylated, with the concentration of phosphorylated p44/42 MAP kinases peaking at 10 min after stimulation and declining in culture at 90 min. The specific p44/42 MAP kinase inhibitor UO126 completely blocked p44/42 phosphorylation and, subsequently, PGE2 production. The airway epithelium may play important bronchoprotective and immunomodulatory roles in chronic neutrophilic inflammation.

Effects of the cationic protein poly-L-arginine on airway epithelial cells in vitro

BACKGROUND

Allergic asthma is associated with an increased number of eosinophils in the airway wall. Eosinophils secrete cationic proteins, particularly major basic protein (MBP).

AIM

To investigate the effect of synthetic cationic polypeptides such as poly-L-arginine, which can mimic the effect of MBP, on airway epithelial cells.

METHODS

Cultured airway epithelial cells were exposed to poly-L-arginine, and effects were determined by light and electron microscopy.

RESULTS

Poly-L-arginine induced apoptosis and necrosis. Transmission electron microscopy showed mitochondrial damage and changes in the nucleus. The tight junctions were damaged, as evidenced by penetration of lanthanum. Scanning electron microscopy showed a damaged cell membrane with many pores. Microanalysis showed a significant decrease in the cellular content of magnesium, phosphorus, sodium, potassium and chlorine, and an increase in calcium. Plakoglobin immunoreactivity in the cell membrane was decreased, indicating a decrease in the number of desmosomes

CONCLUSIONS

The results point to poly-L-arginine induced membrane damage, resulting in increased permeability, loss of cell-cell contacts and generalized cell damage.

Effect of inhaled indomethacin on distilled water-induced airway epithelial cell swelling

We evaluated the mechanism of the anti-asthmatic effect of inhaled indomethacin (Indo) by using an animal model (guinea pigs) of airway inflammation. After being exposed to either ozone or room air at identical flow rates (5 l/min) for 2 h, guinea pigs were anesthetized, tracheostomized, and lung resistance (RL) was subsequently measured. Guinea pigs inhaled either saline or Indo (1.5 mg/ml) for 1 min before undergoing an ultrasonically nebulized distilled water (UNDW) inhalation test. RL increased significantly after 10 min of UNDW inhalation in the room air and ozone groups but more so in the ozone group. This increase in RL was significantly suppressed by pretreatment with Indo. In the morphometric assessment of airway mucosa, a significant swelling of the epithelial cells after UNDW inhalation was observed in both the room air and ozone groups but especially so in the ozone group. This increase was also suppressed with Indo pretreatment. These results suggest that the increase in RL and the swelling of airway epithelial cells induced by inhaled UNDW in ozone-exposed guinea pigs was suppressed by pretreatment of inhaled Indo and that this suppression may be one of the reasons for the anti-asthmatic effect of inhaled Indo.

Peptide-based analysis of amino acid sequences important to the biological activity of eosinophil granule major basic protein

Synthetic peptides corresponding to amino acid sequences in eosinophil granule major basic protein (MBP) were evaluated for cytotoxic activity toward K562 cells and for ability to stimulate basophil mediator release. Results obtained using 14 peptides spanning the 117-amino acid sequence of MBP in overlapping fashion indicated that the activities mapped to peptide sequences near the amino and carboxy termini of MBP. The activity of these regions was confirmed using two peptides corresponding to MBP residues 18-45 and 89-117. A 20-h incubation with 5 microM peptide 18-45 or peptide 89-117 caused approximately the same levels (>60%) of cytotoxicity in K562 cells as 5 microM MBP. Similarly, a 30-min incubation with peptides 18-44 and 89-117 stimulated basophil histamine release in a concentration-dependent manner over the range of 5-20 microM. The level of release stimulated by 20 microM peptide 89-117 approached that stimulated by 2 microM MBP. A 20 microM concentration of peptide 89-117 also stimulated leukotriene C4 (LTC4) production by the basophils. Neither peptide 18-45 nor peptide 89-117 was cytotoxic for basophils under the experimental conditions for histamine and LTC4 release, as determined by 51Cr release. These results indicate that two MBP peptide sequences, including one (89-117) that contains a unique carbohydrate-binding region, share the biologic activities of MBP.

Crystal structure of the eosinophil major basic protein at 1.8 A. An atypical lectin with a paradigm shift in specificity

The eosinophil major basic protein (EMBP) is the predominant constituent of the crystalline core of the eosinophil primary granule. EMBP is directly implicated in epithelial cell damage, exfoliation, and bronchospasm in allergic diseases such as asthma. Here we report the crystal structure of EMBP at 1.8 A resolution, and show that it is similar to that of members of the C-type lectin superfamily with which it shares minimal amino acid sequence identity (approximately 15--28%). However, this protein lacks a Ca(2+)/carbohydrate-binding site. Our analysis suggests that EMBP specifically binds heparin. Based on our results, we propose a possible new function for this protein, which is likely to have implications for EMBP function.

The molecular biology of nasal polyposis

The molecular biologic events in the development of nasal polyps are now becoming unraveled. It appears that eosinophils are the dominant inflammatory cell present in this tissue. The events leading up to the extravasation of eosinophils into the lamina propria nasal polyps are regulated by the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1 beta. These cytokines upregulate very late antigen-4 on the surface of eosinophils and vascular cell adhesion molecule-1 on the surface of the endothelial blood vessel. Chemokines such as RANTES (regulated upon activation, normal T-cell expressed and secreted) and eotaxin are responsible for the movement of eosinophils into the lamina propria of the nasal polyp. The release of major basic protein has an effect on alteration of the epithelial architecture and on the sodium and chloride flux into and out of the apical epithelial cell of the tissue. Finally, the alteration of the surface epithelium results in a defect in the migration of the cystic fibrosis transmembrane regulator protein to the apical surface. These two events, the release of major basic protein from the eosinophil and the alteration of the architecture of the surface epithelium, lead to an increase in sodium absorption and resultant edema: the hallmark of the pathology of the nasal polyp.

Increased eosinophil infiltration and degranulation in colonic tissue from patients with collagenous colitis

OBJECTIVE

Eosinophils infiltrate the colonic mucosa of patients with collagenous colitis (CC), although the pathogenetic implications are unknown, including whether these eosinophils are activated and degranulate in situ. We examined eosinophil infiltration and degranulation in the intestines of patients with CC by immunofluorescence for eosinophil granule major basic protein (MBP).

METHODS

We used both conventional histology (hematoxylin and eosin) and indirect MBP immunofluorescence histochemistry on colon biopsy specimens from patients with CC (n = 21) and from healthy controls (n = 9). Scoring of histological features was performed on hematoxylin and eosin-stained sections on a 0 to 3 scale. Eosinophil infiltration and degranulation, as quantified by extracellular MBP staining, were scored in each specimen on a 0 to 4 scale.

RESULTS

The inflammatory infiltrate of the lamina propria, the thickness of the collagen band, the numbers of intraepithelial lymphocytes, and degree of epithelial cell damage were all significantly increased in patients with CC as compared to controls (p < 0.0001). Scores for both eosinophil infiltration and degranulation were also significantly higher in the CC group compared to controls (p < 0.0001). The degree of infiltrating eosinophils by hematoxylin and eosin was correlated with eosinophil infiltration and degranulation by MBP immunostaining; however, no other correlations were found between eosinophil infiltration or degranulation by immunofluorescence and any of the histological parameters measured in the CC group.

CONCLUSIONS

Eosinophil infiltration and degranulation are increased in the colonic mucosa of patients with CC compared to healthy controls. Eosinophils and their cytotoxic granule proteins could be involved in the pathogenesis of CC. Further studies will be necessary to elucidate the mechanisms of eosinophil activation in CC.

The relationship of eosinophil granule proteins to ions in the sputum of patients with cystic fibrosis

Increased sputum levels of eosinophil granule proteins have been reported despite normal eosinophil numbers in peripheral blood and in the lung in cystic fibrosis (CF). Mechanisms of eosinophil priming and activation are still unclear in CF. In the present study we investigated whether ion concentrations in the sputa of CF patients are related to eosinophil activity. We assessed concentrations of eosinophil cationic protein (ECP), eosinophil protein X (EPX), major basic protein (MBP) and ions (Na+, Cl-, Ca2+, Mg2+) in sputum samples of 29 children with CF as well as in 10 controls with bronchial asthma. Patients with CF demonstrated significantly higher levels of ECP, Na+, Cl- and Ca2+ levels than asthmatics (P < 0.04, P < 0.0001, P < 0.0001, P < 0.02). No differences were seen between concentrations of EPX and Mg2+ in the two groups. In CF, eosinophil granule proteins correlated significantly with Ca2+ and Mg2+ concentrations (ECP, P < 0.0001, r = 0.65, P < 0.0001, r = 0.66; MBP, P < 0.03, r = 0.41, P < 0.03, r = 0.42), furthermore inversely with Cl- concentrations (ECP, P < 0. 0003, r = - 0.63; EPX, P < 0.02, r = - 0.45; MBP, P < 0.03, r = - 0. 41) but not with Na+ levels. ECP, Na+ and Cl- were also correlated with lung function variables (FVC, P < 0.04, r = - 0.38, P < 0.02, r = 0.44, P < 0.03, r = 0.41; FEV1, P < 0.007, r = - 0.49, P < 0.006, r = 0.5, P < 0.008, r = 0.48; MEF50, P < 0.003, r = - 0.54, NS, P < 0.03, r = 0.42; MEF25, P < 0.039, r = - 0.4, P < 0.005, r = 0.51, P < 0.05, r = 0.37). Our results demonstrated a significant relationship of eosinophil degranulation and ions in CF, indicating that ion composition in CF sputa may be at least partly be responsible for high levels of eosinophil products despite low eosinophil numbers.

Transgenic overexpression of beta(2)-adrenergic receptors in airway epithelial cells decreases bronchoconstriction

Airway epithelial cells express beta(2)-adrenergic receptors (beta(2)-ARs), but their role in regulating airway responsiveness is unclear. With the Clara cell secretory protein (CCSP) promoter, we targeted expression of beta(2)-ARs to airway epithelium of transgenic (CCSP-beta(2)-AR) mice, thereby mimicking agonist activation of receptors only in these cells. In situ hybridization confirmed that transgene expression was confined to airway epithelium, and autoradiography showed that beta(2)-AR density in CCSP-beta(2)-AR mice was approximately twofold that of nontransgenic (NTG) mice. Airway responsiveness measured by whole body plethysmography showed that the methacholine dose required to increase enhanced pause to 200% of baseline (ED(200)) was greater for CCSP-beta(2)-AR than for NTG mice (345 +/- 34 vs. 157 +/- 14 mg/ml; P < 0.01). CCSP-beta(2)-AR mice were also less responsive to ozone (0.75 ppm for 4 h) because enhanced pause in NTG mice acutely increased to 77% over baseline (P < 0.05) but remained unchanged in the CCSP-beta(2)-AR mice. Although both groups were hyperreactive to methacholine 6 h after ozone exposure, the ED(200) for ozone-exposed CCSP-beta(2)-AR mice was equivalent to that for unexposed NTG mice. These findings show that epithelial cell beta(2)-ARs regulate airway responsiveness in vivo and that the bronchodilating effect of beta-agonists results from activation of receptors on both epithelial and smooth muscle cells.

The cystic fibrosis conductance regulator gene exon sequence is normal in a patient with edematous eosinophilic nasal polyps

Nasal polyps are the most common mass lesions found in the nose and their etiology is unknown. Nasal polyps from cystic fibrosis (CF) patients are histologically distinct from nasal polyps from patients without CF. It has been suggested that a mutation (G551D) of the cystic fibrosis transmembrane conductance regulator (CFTR) gene may play a role in nasal polyp formation in patients without CF. To investigate the possibility that this or other CFTR gene exon mutations are required for nasal polyp formation, the CFTR gene exons were sequenced from peripheral blood DNA derived from an adult patient with edematous eosinophilic nasal polyps and no personal or family history of CF. No mutations or deletions were identified in any of the CFTR exons. A single polymorphism (A or G) was found in exon 10, base pair 1540, amino acid 470. This polymorphism was detected in 11 of 16 subjects (69%) with edematous eosinophilic nasal polyps and 10 of 21 normal subjects (48%) without nasal polyps and was not statistically significant (p = 0.316). These results demonstrate that mutations of the CFTR coding region are not a prerequisite for the formation of edematous eosinophilic nasal polyps.

Effect of ultrasonically nebulized distilled water on airway epithelial cell swelling in guinea pigs

To investigate the pathogenesis of ultrasonically nebulized distilled water-induced airway narrowing, we studied the role of airway epithelial cells during a distilled water-inhalation challenge in an animal model of airway inflammation. Guinea pigs were divided into four groups: 1) a sham/saline (S/S) group: sham ozone followed by saline inhalation; 2) a sham/water (S/W) group: sham ozone followed by water inhalation; 3) an ozone/saline (O/S) group: ozone followed by saline inhalation; and 4) an ozone/water (O/W) group: ozone followed by water inhalation. After exposure to either 3.0 parts/million ozone or air at the same flow rate for 2 h, guinea pigs were anesthetized and tracheostomized, and then lung resistance (RL) was measured. For morphometric assessment, tissues were fixed with formaldehyde, stained with hematoxylin and eosin, and cut into transverse sections. Airway dimensions were either measured directly or calculated from the internal perimeter, the external perimeter, and airway wall area. There were no statistical differences in the values of RL before distilled water inhalation between the sham groups and the ozone groups. RL increased significantly after 10 min of distilled water inhalation in both the S/W group and the O/W group. In the S/W group, epithelial cells were swollen, and intercellular spaces were wider, resulting in significant increase in epithelial wall thickness, but there was no significant infiltration by inflammatory cells. In the O/S group, the epithelium showed infiltration by inflammatory cells without change in cell volume. In the O/W group, the epithelium showed both infiltration and a greater increase in epithelial wall thickness compared with the S/W group. These results suggest that airway epithelial cell swelling, induced by inhaled distilled water, increases with RL in guinea pigs and that this reaction may be accelerated by airway inflammation.

Human eosinophil granule major basic protein and its novel homolog

Human MBP is associated with an array of in vitro cytotoxic and cytostimulatory activities, mediated in part by its strong basicity. It is most prominently found in the eosinophil, but is also present in placental X cells and placental-site giant cells during pregnancy. Pathologically, its pattern of tissue deposition and its ability to induce characteristic pathophysiologic changes, such as bronchial hyperreactivity and vasopermeability, strongly suggest a role for MBP in allergic and eosinophilic diseases. The role of MBP in protection from helminthic disease is also evident. Here, we present information on a novel homolog of eosinophil granule MBP with biologic activities similar to that of MBP. However, results from experiments on eosinophil granules suggest that the quantity of the homolog present in the eosinophil granule is significantly less than that of MBP itself. Further, preliminary experiments indicate that the two proteins are not synergistic in terms of their cytotoxic and cytostimulatory biologic activities. Future experiments must determine whether the MBP homolog is deposited at sites of tissue damage and can be detected in biologic fluids at concentrations required for biologic activity.

Stem Cell Factor Influences Mast Cell Mediator Release in Response to Eosinophil-Derived Granule Major Basic Protein

Stem cell factor (SCF) is an important mast cell growth, differentiation, and survival factor. We investigated whether SCF influenced the response of mouse mast cells to an IgE-independent stimulus, eosinophil-derived granule major basic protein (MBP). Mouse bone marrow cultured mast cells (BMCMC) were derived in either concanavalin-stimulated mouse spleen conditioned medium (CM) or SCF. The cloned growth, factor-independent mast cell line Cl.MC/C57.1 was also studied. BMCMC in SCF exhibited cytochemical staining properties, protease and histamine content, and increased serotonin uptake consistent with more mature differentiated mast cells as compared with BMCMC in CM or Cl.MC/ C57.1 cells. BMCMC in SCF released serotonin,14C-labeled arachidonic acid metabolites and tumor necrosis factor-α (TNF-α) on stimulation with MBP, while no response was seen from either BMCMC in CM or Cl.MC/C57.1 cells. All three mast cell populations released mediators on stimulation with the cationic MBP analog, poly-L-arginine, indicating that the cationic charge did not explain the selective response of BMCMC in SCF to eosinophil-derived granule MBP. These findings show that SCF significantly influences mast cell differentiation and the responsiveness of mast cells to eosinophil-derived granule MBP.

© 1998 by The American Society of Hematology.

Stem Cell Factor Influences Mast Cell Mediator Release in Response to Eosinophil-Derived Granule Major Basic Protein

Stem cell factor (SCF) is an important mast cell growth, differentiation, and survival factor. We investigated whether SCF influenced the response of mouse mast cells to an IgE-independent stimulus, eosinophil-derived granule major basic protein (MBP). Mouse bone marrow cultured mast cells (BMCMC) were derived in either concanavalin-stimulated mouse spleen conditioned medium (CM) or SCF. The cloned growth, factor-independent mast cell line Cl.MC/C57.1 was also studied. BMCMC in SCF exhibited cytochemical staining properties, protease and histamine content, and increased serotonin uptake consistent with more mature differentiated mast cells as compared with BMCMC in CM or Cl.MC/ C57.1 cells. BMCMC in SCF released serotonin,14C-labeled arachidonic acid metabolites and tumor necrosis factor-α (TNF-α) on stimulation with MBP, while no response was seen from either BMCMC in CM or Cl.MC/C57.1 cells. All three mast cell populations released mediators on stimulation with the cationic MBP analog, poly-L-arginine, indicating that the cationic charge did not explain the selective response of BMCMC in SCF to eosinophil-derived granule MBP. These findings show that SCF significantly influences mast cell differentiation and the responsiveness of mast cells to eosinophil-derived granule MBP.

© 1998 by The American Society of Hematology.

Eosinophil major basic protein increases membrane permeability in mammalian urinary bladder epithelium

The eosinophil granule protein major basic protein (MBP) is toxic to a wide variety of cell types, by a poorly understood mechanism. To determine whether the action of MBP involves an alteration in membrane permeability, we tested purified MBP on rabbit urinary bladder epithelium using transepithelial voltage-clamp techniques. Addition of nanomolar concentrations of MBP to the mucosal solution caused an increase in apical membrane conductance only when the voltage across the apical membrane was cell interior negative. The magnitude of the MBP-induced conductance was a function of MBP concentration, and the rate of the initial increase in conductance was a function of the transepithelial voltage. The MBP-induced conductance was nonselective for K+ and Cl-. Mucosal Ca2+ reversed the induced conductance, whereas mucosal Mg2+ partially blocked the induced conductance and slowed the rate of the increase in conductance. The induced conductance was partially reversed by changing the voltage gradient across the apical membrane to cell interior positive. Prolonged exposure resulted in an irreversible loss of the barrier function of the urinary bladder epithelium. These results suggest that an increase in cell membrane ion permeability is an initial step in MBP-induced loss of barrier function.

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.

Signature current of SO2-induced bronchitis in rabbit

To investigate abnormalities of airway epithelial ion transport underlying chronic inflammatory airway diseases, we performed electrophysiological, histological, and molecular biological experiments using rabbits exposed to SO2 as a model of bronchitis. By comparison with control, the SO2-exposed trachea exhibited decreased short circuit current (Isc) and conductance associated with increased potential difference. In normal trachea, apical ATP induced a transient Isc activation followed by a suppression, whereas the bronchitis model exhibited a prolonged activation without suppression. This pathological ATP response was abolished by diphenylamine 2-carboxylate or Cl--free bath solution. A significant increase in net Cl- flux toward the lumen was observed after ATP in our bronchitis model. Isoproterenol or adenosine evoked a sustained Isc increase in SO2-exposed, but not in normal, tracheas. The Northern blot analysis showed a strong expression of cystic fibrosis transmembrane conductance regulator (CFTR) mRNA in SO2-exposed epithelium. The immunohistochemical study revealed a positive label of CFTR on cells located luminally only in SO2-exposed rabbits. We concluded that the prolonged ATP response in our bronchitis model was of a superimposed normal and adenosine-activated current. The latter current was also activated by isoproterenol and appeared as a signature current for the bronchitis model airway. This was likely mediated by CFTR expressed in the course of chronic inflammation.

Cationic proteins increase the permeability of cultured rabbit tracheal epithelial cells: modification by heparin and extracellular calcium

Airway inflammation is a consistent finding in asthma, and increased amounts of eosinophil-derived cationic proteins are present in bronchoalveolar lavage fluid from asthmatic subjects. Tracheal instillation of a variety of naturally occurring and synthetic cationic proteins has been shown to induce airway hyperresponsiveness in animal models. Cationic proteins may alter the barrier function of airway epithelium, allowing increased access of agonists to underlying nerves and airway smooth muscle. To examine the effect of cationic proteins on airway epithelial cell function, rabbit tracheal epithelial cells were isolated and cultured on collagen-coated filter membranes. Both apical and basolateral exposure of the cell cultures to poly-L-lysine and poly-L-arginine decreased transepithelial electrical resistance (Rt) over 60 min. There were no discernable light microscopic changes in the morphology of the cultures at 60 min after poly-L-lysine exposure, but permeability to mannitol was increased compared to controls. Evidence for the critical role of cationic charge included the following observations: (1) Poly-L-aspartate, an anionic polyamino acid, had no significant effect on Rt, and (2) the addition of heparin prior to the addition of poly-L-lysine blocked the reduction in Rt. Furthermore, when applied after poly-L-lysine addition, heparin reversed the decrease in Rt in a time-dependent fashion. Increasing the [Ca2+] in the medium from 1 to 10 mM resulted in significant attenuation of the response to polycation addition. These findings suggest that cationic proteins significantly alter the barrier properties of airway epithelium and that cationic charge is a crucial factor. This alteration is not an "all or none" phenomenon, since subsequent addition of heparin resulted in a reversal of the effect. While the precise mechanisms responsible for these observations remain to be elucidated, cationic proteins may be modifying the interaction of extracellular calcium with tight junctions thereby resulting in increased permeability. The barrier function of the epithelium may be perturbed in asthma and a variety of other airway diseases through the presence of cationic proteins derived from inflammatory cells within the airway lumen and/or the subepithelium.

Human eosinophils migrate across an intestinal epithelium in response to platelet-activating factor

BACKGROUND/AIMS

Transmigration of eosinophils across intestinal epithelia occurs in a variety of mucosal inflammatory disorders and results in the formation of crypt abscesses containing eosinophils. However, the conditions required to drive transepithelial migration of eosinophils are not understood.

METHODS

This study investigated eosinophil migration across intestinal epithelia using purified eosinophils and confluent monolayers of the human intestinal epithelial cell line T84.

RESULTS

Unactivated eosinophils (i.e., no granulocyte/macrophage colony-stimulating factor [GM-CSF] preexposure) did not migrate across T84 monolayers in the presence of transepithelial gradients of C5a, n-formyl-methionyl-leucyl-phenylalanine (fMLP), or platelet-activating factor (PAF). In contrast, activation of eosinophils by coincubation or pretreatment with GM-CSF enabled transepithelial migration in response to PAF but not to C5a or fMLP gradients in a time- and dose-dependent fashion. Specificity was confirmed by both the PAF receptor antagonist WEB-2086 and the PAF enantiomer 2-lyso-beta-acetyl-gamma-O-hexadecyl. Finally, addition of functionally inhibitory monoclonal antibodies to CD11b but not CD11a, very late activation antigen (VLA-4), or intracellular adhesion molecule 1 inhibited eosinophil migration.

CONCLUSIONS

These studies establish that physiologically directed migration of eosinophils across model epithelia occurs but that this process is governed by the state of eosinophil activation, the specific chemotactic gradient imposed, and the availability of specific surface integrins to participate in putative eosinophil-epithelial adhesion steps.

Role of cationic proteins in the airway. Hyperresponsiveness due to airway inflammation

Major basic protein (MBP) is a highly cationic protein found in the granules of eosinophils. It has been postulated that MBP may participate in the pathogenesis of airway hyperresponsiveness exhibited by asthmatic patients. Accordingly, we have employed a rat system to investigate the effect of human MBP instillation on airway responsiveness and the possible role of cationic charge in the determination of this effect. Major basic protein caused a significant increase in airway responsiveness to inhaled methacholine. Two polycations, poly-L-arginine and poly-L-lysine, also increased airway responsiveness to inhaled methacholine. Moreover, two other very different cationic proteins, platelet factor 4 (PF4) and cathepsin G were also capable of inducing airway hyperresponsiveness. These effects were dependent on their positive charge, since the charge--and, hence the effect--of these proteins was neutralized with low molecular weight heparin. In addition, other polyanions, such as low molecular weight heparin, albumin, or dextran sulfate, were also effective. We investigated whether two synthetic cationic proteins, poly-L-arginine and poly-L-lysine, could modify epithelial-dependent responses using a perfused guinea pig tracheal tube preparation. With an intact epithelium, methacholine was some 150 times less potent when applied intraluminally than when applied extraluminally. Perfusion of the luminal surface with cationic proteins increased the potency of intraluminally applied methacholine without modifying the responses to extraluminally applied methacholine. Cationic proteins also attenuated the relaxant effects of intraluminally applied KCl. These effects occurred in the absence of any overt epithelial cell damage. Our data demonstrates that cationic proteins can modify epithelial-dependent responses in the airways.(ABSTRACT TRUNCATED AT 250 WORDS)

Contractile properties of synthetic cationic polypeptides in guinea-pig isolated trachea

1. The synthetic polypeptides, poly-L-arginine, poly-L-lysine and poly-D-lysine contract guinea-pig isolated trachea in a concentration-dependent, epithelium-independent manner. Indomethacin augmented the contractile response to poly-L-arginine. 2. The contractile response to poly-L-arginine was not significantly inhibited by nicardipine, a selective L-type calcium channel blocker or by the histamine H1-receptor antagonist, mepyramine nor significantly augmented by the neutral endopeptidase inhibitor, phosphoramidon. 3. The contractile response to poly-L-arginine was inhibited in a concentration-dependent manner by prior incubation of guinea-pig tracheal rings with a number of anionic polypeptides including, low molecular weight heparin, poly-L-aspartic acid and bovine serum albumin. 4. In vitro capsaicin-induced desensitization failed to attenuate the contractile response to poly-L-arginine, suggesting little, if any role for sensory neuropeptides in the functional response in the guinea-pig. 5. Synthetic polypeptides induce an epithelium-independent, charge-dependent contraction of guinea-pig isolated trachea.

Epithelium-dependent responses of serotonin in a co-axial bioassay system

Serotonin (10(-6) - 10(-4) M) produced relaxations in a concentration-dependent (at 10(-6) and 10(-5) M concentrations) manner followed by a contraction (at 10(-4) M concentration) in a co-axial system, which consisted of guinea-pig trachea as a donor organ for epithelial derived-relaxing factor(s) and phenylephrine-precontracted rat anococcygeus muscle as assay tissue. Serotonin produced a concentration-dependent contraction only in precontracted rat anococcygeus muscle mounted alone or mounted co-axially within epithelium-denuded trachea. Indomethacin (10(-6) M) significantly inhibited the initial relaxations (from 25.1 +/- 7.8 to 7.8 +/- 5.0% and from 35.6 +/- 8.7 to 10.4 +/- 8.3% at 10(-6) and 10(-5) M concentrations of serotonin), but did not affect the contraction. Imipramine (10(-8) M) and hydrocortisone (3 x 10(-5) M) reduced the initial relaxations (from 20.5 +/- 1.6 to 3.8 +/- 1.5% and from 32.1 +/- 6.4 to 18.9 +/- 3.9% at 10(-6) M and 10(-5) M concentrations of serotonin, respectively) and also converted the serotonin (10(-4) M)-induced contraction to a relaxation. In the co-axial system with trachea from guinea-pigs previously sensitized with i.p. injected egg-ovalbumin, the serotonin-induced biphasic response was converted to a contractile response only after ovalbumin challenge. Histopathologic changes were observed in the epithelium of challenged tracheas taken from sensitized guinea-pigs and alterations of serotonin-induced epithelium-dependent responses were attributed to the morphological and/or functional damage of tracheal epithelium caused by ovalbumin challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies specific for guinea pig eosinophil major basic protein: their use in an ELISA, immunocytochemistry and flow cytometry

Eosinophil major basic protein (MBP), purified from guinea pig eosinophil granules was used to raise five monoclonal antibodies (MoAbs). Their reactivity with MBP was confirmed by immunoblotting and indirect ELISA. Two of the MoAbs were used to develop a sensitive and specific antigen capture (sandwich) ELISA for guinea pig eosinophil MBP which gives an accurate and reproducible standard curve over the range of 10-10,000 ng/ml. The specificity of the ELISA for MBP was confirmed and its suitability for testing biological samples ascertained by measurement of MBP in bronchoalveolar lavage fluid (BALF) and plasma from guinea pigs sensitized and challenged with ovalbumin. The ELISA was also capable of detecting MBP in culture supernatants from purified eosinophil preparations challenged with calcium ionophore in vitro. One of the monoclonals could be used to strongly and specifically stain guinea pig eosinophils in immunocytochemistry, whilst all five could be used to visualize eosinophils in suspension in BALF or peritoneal lavage fluid by flow cytometry. There was no staining of other guinea pig leucocyte types, nor crossreactivity with human eosinophils by immunocytochemistry or flow cytometry.

Submucosal tissues modulate the bioelectric properties of airway epithelium

Exposure of isolated canine tracheal epithelium to acetylcholine (Ach) increased transepithelial conductance (GT) and short-circuit current (ISC). Qualitatively different responses were obtained when the epithelium was studied as a part of an intact posterior tracheal membrane that contained smooth muscle. Ach decreased GT, did not affect ISC, and induced a 2-fold increase in measured tension. In these tissues, baseline GT was enhanced compared with that of isolated epithelium. Indomethacin inhibited the Ach-induced responses of isolated epithelium but did not alter the responses of intact airway tissue. The epithelial origin of these electrophysiologic responses was confirmed in experiments that showed that denudation of intact tracheal tissue greatly increased base-line GT, eliminated ISC, abolished the electrophysiologic response to Ach, and enhanced Ach-induced smooth muscle constriction. The qualitatively different responses to Ach of intact tracheal membrane and epithelium alone suggest that the behavior of airway epithelia in the whole animal may be significantly different from that observed in conventional in vitro studies of isolated epithelia.

The effect of human eosinophil granule major basic protein on airway responsiveness in the rat in vivo. A comparison with polycations

Major basic protein (MBP) is a highly cationic protein found in the granules of eosinophils. It has been postulated that MBP may participate in the pathogenesis of airway hyperresponsiveness exhibited by asthmatic patients. Accordingly, we used a rat model to investigate the effect of human MBP instillation on airway responsiveness and the possible role of cationic charge in the determination of this effect. Dose-response characteristics to inhaled methacholine (MDRC) were determined at baseline, and the animals were allowed to recover. Then animals in the experimental group received 100 micrograms of purified human MBP via direct instillation into the trachea. One hour after instillation, the MDRC were again assessed. Control animals received (in lieu of MBP) buffer from the void volume pool of the same chromatography column used to purify the MBP. One hour after instillation of MBP there was a significant increase in airway responsiveness to inhaled methacholine, whereas control animals exhibited no increase in airway responsiveness. Some animals from the MBP group were restudied 48 h after MBP instillation, by which time airway responsiveness had returned to baseline level. The effect of the polycations poly-L-arginine and poly-L-lysine on airway responsiveness was also examined. As with MBP, airway responsiveness to inhaled methacholine increased 1 h after the instillation of either polycation. In addition, acetylation of the charged groups on poly-L-lysine resulted in a loss of this effect. Histologic examination of the airways failed to reveal airway epithelial shedding 1 h after MBP or polycation instillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Eosinophils and major basic protein damage but do not detach human amniotic epithelial cells

Damage and detachment of epithelial cells is thought to contribute to the pathologenesis of asthma. Both eosinophils and neutrophils are found in asthmatic airways and several studies have suggested that eosinophils may be responsible for the epithelial cell detachment of asthma. To compare the capacity of purified human eosinophils and neutrophils to mediate epithelial cell detachment, we utilized a human amniotic epithelial cell-basement membrane model that we have recently described. Activated eosinophils induced little detachment at 4 h (less than 10% detachment), which contrasted with that seen with equivalent numbers of identically handled neutrophils (29 +/- 6% detachment, p less than .05). In contrast, eosinophils did induce damage to epithelial cells to an extent similar to neutrophils when assessed using a 51Cr release assay (17 +/- 6% and 18 +/- 9% release of 51Cr, respectively). When purified preparations of the major eosinophil-derived protein major basic protein (MBP) were studied, similar effects on epithelial cells were observed, i.e., damage (77 +/- 13% release of 51Cr) without detachment (less than 5% cell detachment). These data suggest that neutrophils are more effective in inducing detachment of human epithelial cells, whereas both eosinophils and neutrophils damage human epithelial cells.

Release of eosinophil granule proteins during IgE-mediated allergic skin reactions

To determine whether the eosinophil (EOS), a prominent component of human allergic skin reactions, releases its potentially pathogenic components in vivo, we appended collection chambers to the bases of unroofed skin blisters and challenged the sites for varying time periods with either pollen antigen (Ag) or buffer (B)-control solutions. In seven sensitive subjects, continuous challenge with pollen Ag consistently induced release of more major basic protein (MBP) and eosinophil-derived neutrophil (EDN) than did B solution. Low levels of both MBP and EDN were observed during the first hour with increased accumulation during the second to fifth hour. Comparison of Ag- versus B-challenged site responses in individual subjects demonstrated significantly higher levels of both MBP and EDN at Ag than at B sites during the second to fifth hour. Levels of both MBP and EDN in the second to fifth hour correlated significantly with histamine release in the same sites in the first hour (r = 0.66 and 0.83, respectively). Imprints of the skin bases of the chambers after 5 hours demonstrated variable numbers of EOS at the Ag-challenged sites and only occasional EOS at the B-challenged sites; most cells on the skin bases were neutrophils. However, immunofluorescence localization of MBP in biopsy specimens of the blister bases revealed striking extra cellular MBP deposition. These findings indicate that EOS components accumulate in vivo in IgE-mediated human skin reactions, even when prominent EOS accumulation is not visualized, possibly because the EOS are degranulated in the allergic-reaction site. Release of EOS components in these reactions may be linked to earlier mast cell activation.(ABSTRACT TRUNCATED AT 250 WORDS)

The release of a non-prostanoid inhibitory factor from rabbit bronchus detected by co-axial bioassay

1. Methacholine relaxed phenylephrine-contracted aorta of the rat with the endothelium intact. This effect was inhibited by haemoglobin, methylene blue, gossypol, phenidone and L-NG-nitroarginine methyl ester (L-NAME). Rat aorta denuded of endothelium failed to relax in response to methacholine, histamine and the peptidoleukotrienes C4, D4 and E4. 2. Methacholine and histamine but not leukotrienes C4, D4 and E4 relaxed phenylephrine-contracted rat aorta without endothelium when surrounded by rabbit epithelium-intact bronchus. The muscarinic antagonist atropine antagonized the methacholine-induced relaxation. 3. Removal of the epithelium either mechanically or chemically, abolished methacholine-induced relaxation of rat aorta in the co-axial bioassay. These data indicate that the epithelium is responsible for the observed relaxant effect to methacholine and histamine. 4. The cyclo-oxygenase inhibitor, indomethacin, the phospholipase A2 inhibitor, mepacrine and the lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), failed to inhibit methacholine-induced relaxation of rat aorta in the co-axial bioassay. This indicates that the epithelium-derived inhibitory factor (EpDIF) is not a product of the cyclo-oxygenase or lipoxygenase pathway or a product derived from activation of phospholipase A2. 5. Haemoglobin, methylene blue, phenidone, gossypol and L-NAME failed to inhibit the relaxation of rat aorta in the co-axial bioassay. These results demonstrate that EpDIF detected in the co-axial bioassay is not endothelium-derived relaxing factor (EDRF) or nitric oxide. Similarly, catalase was without effect. 6. EpDIF is unlikely to be a peptide since papain and alpha-chymotrypsin failed to alter the methacholine-induced relaxation of rat aorta in the co-axial bioassay. Furthermore, thiorphan, captopril and aprotinin were also without effect, suggesting that EpDIF is not a substrate for airway peptidases. 7. The results presented in this paper demonstrate the release of a vasoactive epithelium-derived inhibitory factor (EpDIF) from rabbit intrapulmonary bronchi by use of a co-axial bioassay preparation.

Effect of surfactant on bioelectric properties of canine tracheal epithelium

The functional significance of pulmonary surfactant in the airways is not well known and the effects of surfactant on bioelectrical properties of airway epithelium have not been investigated. In the present study, we examined the effect of synthetic surfactant (TR-14) or calf lung surfactant extract (surfactant TA) on transepithelial potential difference (PD) and short circuit current (SCC) in canine trachea. The conductance (G) was calculated as the ratio of SCC per open-circuited PD. The posterior membrane without muscular layer from canine trachea was mounted in an Ussing-type chamber, bathed with Krebs-Ringer buffer solution at 37 degrees C and gassed with 95% O2-5% CO2, pH 7.4. Treatment with mucosal surfactant produced an increase in both PD and SCC in a dose-dependent fashion. PD and SCC reached 132% and 124% of before control at 0.25 mg/ml after the addition of each surfactant respectively, whereas G remained unchanged. Both ouabain and furosemide abolished surfactant-evoked increases in PD and SCC, whereas amiloride did not alter the surfactant-evoked increases. No significant differences in the effect on bioelectric parameters were observed between TR-14 and surfactant TA. These findings suggest that lung surfactant affects bioelectrical properties and changes ion transport (Cl- secretion) across airway epithelium, probably through the activity of ion pumps in the cellular membrane.

Pharmacological evaluation of a guinea-pig tracheal epithelium-derived inhibitory factor (EpDIF)

1. An epithelium-derived inhibitory factor (EpDIF) released by guinea-pig tracheal epithelium was evaluated in a co-axial bioassay system consisting of an epithelium-intact guinea-pig tracheal tube surrounding endothelium-denuded rat aortic strip. 2. Histamine and several muscarinic agonists induced concentration-dependent relaxation of phenylephrine-contracted rat aorta via the release of EpDIF. However, several other agonists did not induce the release of EpDIF from guinea-pig trachea. These included the nicotinic cholinoceptor agonists nicotine (25 microM), 1,1-dimethyl-4-phenylpiperazinium (DMPP) (25 microM), calcium ionophore A23187 (0.5 microM), bradykinin (0.05-0.5 microM), substance P (5 microM), platelet activating factor (PAF, 1-100 nM), the leukotrienes (LT) LTC4, LTD4 and LTE4 (0.1-10 nM) as well as hyperosmotic stimuli. 3. Prostaglandin E2 (PGE2) induced concentration-dependent contraction of endothelium-denuded rat aortic preparations, indicating that this prostanoid could not be EpDIF. Furthermore, relaxation to histamine and methacholine, mediated via EpDIF, was not significantly altered in the presence of phenidone (50 microM) the cyclo-oxygenase/lipoxygenase inhibitor with radical scavenging properties or the cytochrome P-450 inhibitors metyrapone (1 mM) and SKF 525A (25 microM). This suggests that EpDIF is neither a prostanoid nor a cytochrome P-450 metabolite of arachidonic acid. 4. The soluble guanylate cyclase inhibitor, methylene blue (50 microM), caused small but significant increases in the potencies of both histamine and methacholine in co-axial assemblies, indicating that EpDIF did not activate this enzyme and therefore was not NO or a related substance. The beta-adrenoceptor antagonist, (-)-propranolol (1 microM), and the PAF-receptor antagonist, WEB 2086 (50 microM), also failed to alter significantly EpDIF-modulated relaxations. These data suggest that EpDIF is neither a stimulant of fiadrenoceptors nor of PAF receptors. 5. The present study provides some evidence that this vascular smooth muscle-sensitive EpDIF may not be related to the putative EpDIF previously hypothesized to modulate directly spasmogen-induced airway smooth muscle tone.

The role of platelet activating factor in allergic respiratory disease

1. Platelet activating factor (PAF) is an ether-linked phospholipid capable of eliciting many of the factors of the allergic response including bronchoconstriction, mucosal oedema, eosinophil infiltration and bronchial hyperresponsiveness. 2. A wide range of selective PAF receptor antagonists have now been described which have been reported to reduce many aspects of allergen-induced inflammatory responses in experimental animals. 3. Early clinical studies have indicated that some of these drugs are also effective PAF antagonists in man, but no controlled studies have been reported using these compounds in patients with allergic asthma. 4. The gingkolide mixture BN 52063 has recently been reported to inhibit allergen-induced cutaneous inflammation in man; a response which has certain pathological similarities to allergen-induced late-onset airways obstruction in the lung. 5. Therefore, drugs antagonizing the actions of PAF may well lead to a better understanding of and may be a novel therapeutic approach for allergic respiratory disorders.

Rat tracheal epithelial cells produce granulocyte/macrophage colony-stimulating factor

It is unknown whether local resident cells of the upper airway are able to regulate the number and function of phagocytic cells by the secretion of cytokines. We undertook to determine if tracheal epithelial cells (TEC) produce the potent cytokine granulocyte/macrophage colony-stimulating factor (GM-CSF) and how TEC-derived GM-CSF might be regulated. Conditioned media (TEC-CM) from 7- to 21-day-old primary cultures of rat TEC contained material with bioactivity similar to GM-CSF. This bioactivity was increased in conditioned medium from lipopolysaccharide (LPS)-treated (1 microgram/ml) TEC. Molecular characterization of bioactivity revealed a molecular weight of 27 to 44 kD by gel-filtration high performance liquid chromatography (HPLC), and elution at 44 to 50% acetonitrile by reverse-phase HPLC, similar to that of authentic GM-CSF. The biologic activity of TEC-CM was completely blocked by a goat polyclonal anti-GM-CSF antibody. With in situ hybridization using a murine GM-CSF cDNA probe, more than 95% of the adherent TEC population expressed GM-CSF transcripts, and the number of transcripts was significantly increased by LPS (1 microgram/ml, 48 h). TEC appear to produce a cytokine that is functionally, biochemically, and antigenically indistinguishable from GM-CSF. The ability of TEC to produce GM-CSF suggests that these cells may play a role in modulating the inflammatory response in the airway.