Interleukin-4 and interleukin-13 cause barrier dysfunction in human airway epithelial cells

Abstract

Emerging evidence indicates that airway epithelial barrier function is compromised in asthma, a disease characterized by Th2-skewed immune response against inhaled allergens, but the mechanisms involved are not well understood. The purpose of this study was to investigate the effects of Th2-type cytokines on airway epithelial barrier function. 16HBE14o- human bronchial epithelial cells monolayers were grown on collagen coated Transwell inserts. The basolateral or apical surfaces of airway epithelia were exposed to human interleukin-4 (IL-4), IL-13, IL-25, IL-33, thymic stromal lymphopoietin (TSLP) alone or in combination at various concentrations and time points. We analyzed epithelial apical junctional complex (AJC) function by measuring transepithelial electrical resistance (TEER) and permeability to FITC-conjugated dextran over time. We analyzed AJC structure using immunofluorescence with antibodies directed against key junctional components including occludin, ZO-1, β-catenin and E-cadherin. Transepithelial resistance was significantly decreased after both basolateral and apical exposure to IL-4. Permeability to 3 kDa dextran was also increased in IL-4-exposed cells. Similar results were obtained with IL-13, but none of the innate type 2 cytokines examined (TSLP, IL-25 or IL-33) significantly affected barrier function. IL-4 and IL-13-induced barrier dysfunction was accompanied by reduced expression of membrane AJC components but not by induction of claudin- 2. Enhanced permeability caused by IL-4 was not affected by wortmannin, an inhibitor of PI3 kinase signaling, but was attenuated by a broad spectrum inhibitor of janus associated kinases. Our study indicates that IL-4 and IL-13 have disruptive effect on airway epithelial barrier function. Th2-cytokine induced epithelial barrier dysfunction may contribute to airway inflammation in allergic asthma.

Epithelial barrier function: At the front line of asthma immunology and allergic airway inflammation

“…Rather, these investigators found that TNF-α causes marked AJC disassembly in a Src-dependent manner. We found that both IL-4 and IL-13 induced barrier disruption in 16HBElo- cells by inhibiting surface expression of ZO-1, occludin, E-cadherin and β-catenin 20 . In contrast to the Th2-depdendent induction of leaky claudin-2 observed in intestinal epithelia, neither IL-4 nor IL-13 induced claudin-2 expression in 16HBElo- cells.…”

“…Claudin-2, in contrast, is an example of a leaky claudin associated with increased permeability in the intestine, where it is induced by interleukin-13 (IL-13) in a Stat6-dependent manner 19 . Although IL-4 and IL-13 also enhance airway epithelial permeability and barrier dysfunction, they do so without inducing claudin-2 in 16HBE airway epithelial cells 20 . These studies indicate that Th2 cytokine-induced epithelial barrier dysfunction can occur in the intestine and airway by different mechanisms.…”

Apoptosis and Engulfment by Bronchial Epithelial Cells. Implications for Allergic Airway Inflammation

“…Our mouse model was generated by crossing Rac1 fl/fl mice to mice with a Cre recombinase that is expressed in a tetracycline-inducible manner under the control of the promoter for club cell (Clara cell) secretory protein (denoted CCSP-Cre/Rac1 fl/fl mice) (10,14). Disruption of the integrity of the epithelial barrier, such as disruption of apical junctional complexes, is associated with exacerbations of allergic airway inflammation (15,16). We confirmed that a loss of Rac1 expression had no apparent effects on the integrity of the epithelial barrier at baseline: lung morphology, epithelial cell number, tight junction formation, alveolar-capillary membrane integrity, and uptake of antigen in CCSPCre/Rac1 fl/fl mice were all comparable to control animals.…”

Key mediators in the immunopathogenesis of allergic asthma

“…Bronchial biopsies and sputum show increased levels of both mRNA expression and protein levels of IL-4, IL-5, IL-13 and their receptors (132). IL-4 and IL-13 has been found to disrupt the human airway epithelial barrier that may contribute to airway inflammation in allergic asthma (143). …”