Claudin-4 has been reported to function as a paracellular sodium barrier and is one of the 3 major claudins expressed in lung alveolar epithelial cells. However, the possible role of claudin-4 in bronchial asthma has not yet been fully studied. In this study, we aimed to elucidate the role of claudin-4 in the pathogenesis of bronchial asthma.
We determined claudin-4 levels in blood from asthmatic patients. Moreover, using mice sensitized and challenged with OVA, as well as sensitized and challenged with saline, we investigated whether claudin-4 is involved in the pathogenesis of bronchial asthma. Der p1 induced the inflammatory cytokines in NHBE cells.
We found that claudin-4 in blood from asthmatic patients was increased compared with that from healthy control subjects. Plasma claudin-4 levels were significantly higher in exacerbated patients than in control patients with bronchial asthma. The plasma claudin-4 level was correlated with eosinophils, total IgE, FEV1% pred, and FEV1/FVC. Moreover, lung tissues from the OVA-OVA mice showed significant increases in transcripts and proteins of claudin-4 as well as in TJ breaks and the densities of claudin-4 staining. When claudin-4 was knocked down by transfecting its siRNA, inflammatory cytokine expressions, which were induced by Der p1 treatment, were significantly increased.
These findings thus raise the possibility that regulation of lung epithelial barrier proteins may constitute a therapeutic approach for asthma