Bronchial Epithelial Permeability Research Articles

In vivo observations provide insight into roles of eosinophils and epithelial cells in asthma.

Observations in vivo in patients, supported by guinea-pig in vivo data, take centre stage in this perspective. Its objective is to highlight dichotomies between asthma features observed in vivo and accepted views involving cell/molecular biology research paradigms. For example, increased bronchial epithelial permeability is now considered a major paradigm and trait of asthma, yet, absorption of inhaled tracers has not been increased in vivo in asthma. Such maintained barrier function in exudative asthma reflects in vivo asymmetry of the epithelial lining as barrier between outside and inside world of molecules and cells. In desquamatory asthma, maintained epithelial tightness may be explained by in vivo demonstrations of exceedingly patchy epithelial loss, prompt creation of plasma-derived provisional barriers, and high-speed epithelial regeneration. Acknowledged protein/peptide secretion by epithelial cells in vitro is contrasted here with a dominant, unidirectional movement in vivo of plasma-derived proteins/peptides (including antimicrobial peptides) to the surface of an intact epithelial lining. Furthermore, longstanding claims that epithelium-produced adenosine is a mediator of asthma are eroded by observations in vivo in asthmatics. Notions concerning activation/fate of mucosal tissue eosinophils illustrate additional distinctions between accepted views and in vivo patient observations. Finally, in vitro-based paradigms preaching defect epithelial regeneration and increased permeability in pathogenesis of asthma are contrasted with experimental in vivo observations of exaggerated epithelial regeneration, which is multipathogenic in its own right. In conclusion, unexpected and challenging in vivo observations in recent decades underpin novel insights into mucosal mechanisms in asthma.

The endogenous cannabinoid anandamide increases human airway epithelial cell permeability through an arachidonic acid metabolite

Injury to the bronchial epithelium in respiratory diseases such as asthma and COPD results in the loss of barrier function and an elevated sensitivity to environmental insults. An increased release of the endogenous cannabinoid, anandamide in response to inhalation of allergen in asthmatic patients has been reported. The aim of this study was, therefore, to determine the effects of endocannabinoids on bronchial epithelial cell permeability and to investigate the mechanisms involved.Calu-3 human bronchial epithelial cells were cultured at air–liquid interface to allow development of tight junctions. Changes in Transepithelial Electrical Resistance (TEER), a reflection of epithelial permeability, were measured at various time points post-treatment, and expression of the tight junction proteins, occludin and ZO-1, were determined using Western immunoblotting.Anandamide produced a significant reduction in TEER, which was unaffected by cannabinoid receptor antagonists, but attenuated by URB597, an inhibitor of fatty acid amide hydrolase, and by a combination of cyclooxygenase (COX) and lipoxygenase (LOX) blockade. The anandamide metabolite, arachidonic acid, showed similar TEER decrease that was also prevented in the presence of COX and LOX inhibitor. Expression of occludin and ZO-1 were also reduced by anandamide.These findings indicate a pro-inflammatory-like effect of anandamide on bronchial epithelial permeability, mediated by cyclooxygenase and lipoxygenase metabolites, and suggest that inhibition of anandamide degradation might provide a novel approach to treat airway inflammation.

Hyaluronan and Layilin Mediate Loss of Airway Epithelial Barrier Function Induced by Cigarette Smoke by Decreasing E-cadherin

Cigarette smoke (CigS) exposure is associated with increased bronchial epithelial permeability and impaired barrier function. Primary cultures of normal human bronchial epithelial cells exposed to CigS exhibit decreased E-cadherin expression and reduced transepithelial electrical resistance. These effects were mediated by hyaluronan (HA) because inhibition of its synthesis with 4-methylumbelliferone prevented these effects, and exposure to HA fragments of <70 kDa mimicked these effects. We show that the HA receptor layilin is expressed apically in human airway epithelium and that cells infected with lentivirus expressing layilin siRNAs were protected against increased permeability triggered by both CigS and HA. We identified RhoA/Rho-associated protein kinase (ROCK) as the signaling effectors downstream layilin. We conclude that HA fragments generated by CigS bind to layilin and signal through Rho/ROCK to inhibit the E-cadherin gene and protein expression, leading to a loss of epithelial cell-cell contact. These studies suggest that HA functions as a master switch protecting or disrupting the epithelial barrier in its high versus low molecular weight form and that its depolymerization is a first and necessary step triggering the inflammatory response to CigS.

Systemic response induced by Scorpaena plumieri fish venom initiates acute lung injury in mice

Scorpaena plumieri venomous fish inflicted severe injuries in humans characterized by systemic effects and cardiovascular abnormalities. Although cardiotoxic and hypotensive effects induced in rats by this venom have been studied, little is known about their effect on bronchial epithelial permeability and airway inflammation in mice. The primary goal of this study was to determine whether the intraplantar or intraperitoneal injection of S. plumieri venom results in systemic response, and whether this event initiates acute lung injury. We found that BALB/c mice developed neutrophilic infiltrates, areas of lung hemorrhage and alveolar macrophage activation within 24 h after injection with S. plumieri venom. These histopathological changes were associated with an early increase in BAL fluid protein and early induction of cytokines, chemokines and matrix metaloproteinases, followed by a later increase in BAL fluid neutrophils. These findings provide clear evidence that the injection of S. plumieri venom in footpad or peritoneal cavity of mice results in venom deposition in the airway and initiates a sustained inflammatory response in the lungs.

Contact Activation via ICAM-1 Induces Changes in Airway Epithelial Permeability in vitro

The role of ICAM-1 in contact activation of the bronchial epithelial cells is elucidated. Direct contact between epithelial cells and leukocytes is required to change transepithelial electrical resistance (TER) of the epithelium. Migration of human neutrophils across the layers of cultured human airway epithelial cells (Calu-3) or primary cow tracheal epithelial cells was induced by an fMLP gradient. Migrating neutrophils decreased TER and increased permeability to albumin. Monoclonal antibodies to ICAM-1 reduced neutrophil migration, thus reducing the changes in TER and changes in the epithelial permeability to albumin. By confocal microscopy, ERK1/2 was found to be locally activated in the epithelial cells at the sites of migration and cross-linking of ICAM-1. Blockade of ERK1/2 by PD98059 decreased the changes in TER which were induced by ICAM-1 cross-linking. Contact activation of the bronchial epithelial cells, involving ICAM-1 via local activation of ERK1/2, is an important mechanism of alteration of the bronchial epithelial permeability.

Respiratory Syncytial Virus Causes Increased Bronchial Epithelial Permeability

Respiratory syncytial virus (RSV)-induced diseases are mediated through active cytokines released during infection. We hypothesized that RSV infection causes bronchial epithelial monolayer permeability in vitro via induction of vascular endothelial growth factor (VEGF). Human bronchial epithelial cells were infected with RSV. In some cultures, VEGF antibody was included to block VEGF response; in other cultures, palivizumab was added to block RSV infection. Permeability was assessed in real-time using electric cell-substrate impedance sensing. VEGF release was assessed using enzyme-linked immunosorbent assay. Gap formation was assessed using live cell imaging. RSV-infected cells demonstrated a decrease in the resistance of the monolayer indicating an increase in permeability; this increase was blocked with VEGF-specific antibody, and palivizumab. Intercellular gap formation developed in RSV-infected epithelial monolayers. RSV increases permeability of the bronchial airway epithelial monolayer via VEGF induction.

No effect of histamine on human bronchial epithelial cell permeability and tight junctional integrity in vitro

Both animal and human studies have suggested that histamine increases airway epithelial cell permeability in vivo. In order to study the effect of histamine on paracellular epithelial permeability and tight junctional integrity, we have cultured human bronchial epithelial cells to confluency and investigated the effect of topically applied 0.1-20.0 microM histamine. Cultures were established on microporous membranes of tissue culture cell inserts and used for the assessment of: 1) transepithelial movement of radiolabelled mannitol (14C-mannitol) and bovine serum albumin (14C-BSA), in the luminal to serosal direction and 2) changes in electrical resistance of the cultures. Epithelial cell cultures were also established on plastic coverslips, in order to determine tight junction morphology by freeze-fracture electron microscopy, and to assess junctional integrity by lanthanum penetration, using thin sections. Compared with untreated control cultures, 0.1-10 microM histamine did not significantly alter the movement of either 14C-mannitol or 14C-BSA across the epithelial cultures at any time during incubation, but caused an increase in the electrical resistance of the cultures, which was maximal by 6 h of incubation. The morphology of the tight junctions revealed by freeze-fracture and junctional integrity (the latter determined by the degree of lanthanum penetration) were similar in untreated control cultures and cultures incubated with histamine. These studies indicate that histamine does not have a direct effect on paracellular bronchial epithelial permeability in vitro.

Host susceptibility to indoor air pollution

Host susceptibility to indoor air pollution

Human Nasal and Bronchial Epithelial Cells in Culture: An Overview of Their Characteristics and Function

Our studies have demonstrated it is possible to culture both human nasal and bronchial epithelial cells to confluency under similar conditions in vitro. These cells are similar morphologically, histologically, and functionally and resemble the cells in vivo. Studies of ciliary activity demonstrate that these cells react toward various agonist and antagonist agents in a similar manner as the cells reported in vivo and consequently will prove to be a valuable model for the evaluation of various therapeutic agents used in the management of infective lung diseases. Similarly studies on the effect of histamine have demonstrated that histamine probably does lead to an increase in bronchial epithelial permeability in vivo and that this effect is likely to be mediated via stimulation of H-1 receptors. Again this could be of clinical relevance when formulating appropriate therapy. The finding that human tracheal and nasal epithelial cells in culture are capable of synthesizing PGE2 could have important clinical implications because this compound is thought to be a putative epithelium-derived relaxing factor. Although this finding awaits confirmation, similar studies with bronchial epithelial cells in vitro would provide a useful tool for study of the function of the bronchial epithelium and its role in the pathogenesis of diseases such as asthma and chronic bronchitis.

Binding and diffusion characteristics of 14C EDTA and 99mTc DTPA in respiratory tract mucus glycoprotein from patients with chronic bronchitis.

Measurement of pulmonary clearance of an inhaled aerosol of technetium-99m labelled diethylenetriaminepenta-acetate (DTPA) by external detection methods has been used widely as an index of permeability across alveolar epithelium and bronchial mucosa. To determine the applicability of the tracer to measurement of permeability in the airways the diffusion and binding characteristics of 99mTc DTPA and the chemically related ethylenediaminetetra-acetic acid labelled with carbon-14 (14C EDTA) was studied in purified respiratory tract mucus glycoprotein from patients with chronic bronchitis. The diffusion coefficients for 99mTc DTPA and 14C EDTA through mucus gels were significantly lower than those for tritiated water. Both molecules bound to the mucus gels with high affinity at two independent low capacity sites. Appreciable amounts of 99mTc DTPA or 14C EDTA are therefore unlikely to cross mucus layers of physiological thickness over periods of four or five hours. This suggests that when pulmonary clearance is determined by the 99mTc DTPA method the tracer retained in mucus lined airways will provide background activity. This study supports the assumption that pulmonary clearance measurements are mainly measuring alveolar epithelial permeability and should not be used to study bronchial epithelial permeability.