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

Controversy surrounding the increased expression of TGF beta 1 in asthma

Asthma is a waxing and waning disease that leads to structural changes in the airways, such as subepithelial fibrosis, increased mass of airway smooth muscle and epithelial metaplasia. Such a remodeling of the airways futher amplifies asthma symptoms, but its etiology is unknown. Transforming growth factor β1 is a pleiotropic cytokine involved in many fibrotic, oncologic and immunologic diseases and is believed to play an essential role in airway remodeling that occurs in asthmatic patients. Since it is secreted in an inactive form, the overall activity of this cytokine is not exclusively determined by its level of expression, but also by extensive and complex post-translational mechanisms, which are all importanin modulating the magnitude of the TGFβ1 response. Even if TGFβ1 upregulation in asthma is considered as a dogma by certain investigators in the field, the overall picture of the published litterature is not that clear and the cellular origin of this cytokine in the airways of asthmatics is still a contemporaneous debate. On the other hand, it is becoming clear that TGFβ1 signaling is increased in the lungs of asthmatics, which testifies the increased activity of this cytokine in asthma pathogenesis. The current work is an impartial and exhaustive compilation of the reported papers regarding the expression of TGFβ1 in human asthmatics. For the sake of comparison, several studies performed in animal models of the disease are also included. Inconsistencies observed in human studies are discussed and conclusions as well as trends from the current state of the litterature on the matter are proposed. Finally, the different points of regulation that can affect the amplitude of the TGFβ1 response are briefly revised and the possibility that TGFβ1 is disregulated at another level in asthma, rather than simply in its expression, is highlighted.

Ultrastructure of bronchial biopsies from patients with allergic and non-allergic asthma

Epithelial damage is commonly found in airways of asthma patients. The aim of this study was to investigate epithelial damage in allergic and non-allergic asthma at the ultrastructural level. Bronchial biopsies obtained from patients with allergic asthma (n=11), non-allergic asthma (n=7), and healthy controls (n=5) were studied by transmission electron microscopy. Epithelial damage was found to be extensive in both asthma groups. Both in basal and in columnar cells, relative desmosome length was reduced by 30-40%. In columnar cells, half-desmosomes (i.e., desmosomes of which only one side was present) were frequently noticed. Eosinophils showing piece-meal degranulation were commonly observed in allergic asthma. Degranulating mast cells were more often observed in allergic asthma. Goblet cell hyperplasia was only found in allergic asthma. Lymphocytes were increased in both groups. In both groups, the lamina densa of the basal lamina was thicker than the control by about 40-50%. In allergic asthma the lamina densa was irregular with focal thickening. While there was always a tendency for changes (epithelial damage, desmosomes, degranulating mast cells, basal lamina) to be more extensive in allergic asthma compared to non-allergic asthma, there was no significant difference between the two groups in this respect. Reduced desmosomal contact may be an important factor in the epithelial shedding observed in patients with asthma.

Relationship between inflammatory cells and structural changes in the lungs of asymptomatic and never smokers: a biopsy study

BACKGROUND

A study was undertaken to investigate the relationship between inflammatory cells and structural changes in the mucosa of the airways in an epidemiological sample of a group of asymptomatic smokers (smokers who had never sought medical attention for respiratory problems) and in non-smoking subjects.

METHODS

Bronchial biopsy specimens were taken from 29 smokers and 16 never smokers and stained with monoclonal antibodies HNL, EPO, AA1, CD68 in order to identify neutrophils, eosinophils, mast cells, and macrophages, respectively. The biopsy specimens were also stained with monoclonal antibodies to the cytokines interleukin (IL)-1beta and IL-8. Structural changes were identified by staining the biopsy specimens with antibodies to tenascin and laminin and by evaluating the condition of the epithelial layer.

RESULTS

The numbers of all inflammatory cells and of cytokine staining cells were significantly increased in smokers. The thickness of the tenascin and laminin layers was increased in the smoking group and the integrity of the epithelial layer was significantly reduced. In smokers the epithelial integrity was negatively correlated with the number of eosinophils and macrophages. The thickness of the tenascin and laminin layers was positively correlated with AA1 and EPO positive cells only.

CONCLUSION

High numbers of inflammatory cells are present in the bronchial mucosa of asymptomatic smokers which have a clear relationship with the impaired epithelial integrity. The increased thickness of the laminin and tenascin layers in these subjects was strongly related to the presence of eosinophils and mast cells, suggesting a role for these cells in tissue remodelling of the airways of smokers.

Inflammation and structural changes in the airways of patients with atopic and nonatopic asthma. BHR Group

The aim of the present study was to compare the cellular pattern and structural changes in the airway walls of atopic and nonatopic patients with asthma. Bronchial biopsy specimens were obtained from 13 atopic subjects with asthma, nine nonatopic patients with asthma, and seven healthy control subjects and investigated using immunohistochemical methods. The number of eosinophils increased in both asthma groups, but significantly more in the atopic group. The number of mast cells increased similarly in the two asthma groups, whereas the number of neutrophils increased only in the nonatopic asthma group. The number of T-lymphocytes (CD3-, CD4-, CD8-, CD-25-positive cells) was higher in patients with atopic asthma compared with nonatopic asthma. Interleukin-4 (IL-4) and IL-5-positive cells were more frequently found in the atopic asthma group, whereas cells staining for IL-8 were more frequent in the nonatopic group. The degree of epithelial damage was significantly higher in the atopic asthma group compared with the control subjects and the nonatopic asthmatics. The tenascin and laminin layer was significantly thicker in the atopic group compared with the group of nonatopic asthmatics. In the atopic group, there was a significant negative correlation between epithelial integrity (defined as the relative length of intact epithelium) and the eosinophil count and also between the number of CD25-positive cells and epithelial integrity. The number of mast cells correlated positively with the thickness of tenascin- and laminin-positive layers. In conclusion, we provide evidence of different patterns of involvement of inflammatory cells in atopic and nonatopic patients with asthma. There were also structural differences in the bronchial mucous membrane between atopic asthma and nonatopic asthma. This suggests that there are differences in the extent of the immunopathologic response of these clinically distinct forms of asthma.

The interaction of neutrophils with respiratory epithelial cells in viral infection

Viral respiratory infection is very common. Respiratory syncytial virus (RSV) infects almost all children during the first 2 years of life. Respiratory syncytial virus is the most frequent cause of bronchiolitis, which is strongly linked with asthma. However, the pathophysiology of RSV bronchiolitis is unclear. Neutrophils are the predominant airway leucocytes in RSV bronchiolitis and other viral infections. Neutrophils and their products are likely to play an important role in viral infection. Current evidence indicates that: (i) viral infection of epithelial cells increases the production of neutrophil chemoattractants or chemokines, which induce neutrophil migration into the inflammatory sites; (ii) the expression of adhesion molecules on neutrophils and epithelial cells is up-regulated in viral infection, and neutrophil-epithelial adhesion is increased; (iii) neutrophils augment epithelial damage and detachment induced by viral infection and contribute to the pathophysiology of viral disease; (iv) neutrophil apoptosis is up-regulated in RSV infection, which may be an in vivo mechanism to limit neutrophil-induced epithelial damage; (v) inhibitors of chemokines, adhesion molecules or neutrophil proteases may be useful in prevention of neutrophil-induced epithelial damage. In conclusion, neutrophils play an important role in viral infection, and intervention to prevent neutrophil-induced epithelial damage may be a potential clinical therapy.

Epithelial cell damage is induced by neutrophil-derived, not pseudomonas-derived, proteases in cystic fibrosis sputum

Airway histopathological changes in cystic fibrosis (CF) include damage to the epithelial tissue and accumulation of polymorphonuclear leukocytes (PMN). Airways of CF patients are usually colonized with bacteria such as mucoid Pseudomonas aeruginosa (PA). Bacteria and PMN can both release proteolytic enzymes capable of causing tissue damage. This study aims to clarify and compare the roles of these agents in epithelium damage. Epithelial cell (EC) damage and detachment induced by sputum samples from CF or non-CF patients, with and without lung infection, were assessed on amnionic EC in an in vitro model of airway epithelium. Protease activity was determined using inhibitor profiles, and compared to the proteolytic activity of isolated neutrophils and bacteria. Sputa from CF patients and infected non-CF patients induced high levels of detachment. PA also induced high levels of EC detachment but Staphylococcus aureus and Haemophilus influenzae, two other bacteria commonly isolated from CF sputa, induced no detachment. Antiprotease inhibition profiles were similar for PMN and sputa-induced EC detachment, but different for PA-induced detachment. These results suggest that PMN proteolytic enzymes, probably elastase and cathepsin G, are more likely to be the inducers of tissue damage in the airways of CF patients than PA proteolytic enzymes.

Role of neutrophils in mediating human epithelial cell detachment from native basement membrane

Epithelial cell detachment from underlying basement membrane is a feature of diseases of many organs. In the lungs it is seen in disorders as diverse as bronchiectasis, allograft rejection, and asthma. The potential for different leukocytes to induce this change is not clear. In asthma both eosinophils and neutrophils are found in affected tissues, but the capacity of each of these types of cells to induce detachment of native epithelial cells from basement membrane requires clarification. Although eosinophils damage rather than detach human epithelial cells, the effects of neutrophils on epithelial cells naturally attached to basement membrane have not previously been described. Using the human amnion in vitro model, we tested the hypothesis that neutrophils have the capacity to detach intact human epithelial cells from basement membrane. The data indicate that increasing concentrations of neutrophils are able to detach epithelial cells from their underlying basement membrane. Detachment was increased when the neutrophils were activated in situ with tetradecanoyl phorbol acetate and after longer incubation periods. Platelet activating factor and opsonized zymosan showed similar boosting effects, whereas activated complement and formyl-methyl-leucyl-phenylalanine did not. Physical contact of the neutrophils with the epithelial cells was required to induce detachment. Detachment could be inhibited by glutathione and by soybean trypsin inhibitor, an inhibition pattern similar to cathepsin G and trypsin, but not collagenase, in this system. We conclude that neutrophils are capable of detaching human epithelial cells from basement membrane, which in part involves the release of chymotrypsin-like serine proteases, probably in conjunction with oxidants, and that this detachment can be inhibited.