Objective: The present study was undertaken to test the hypothesis that if Cldn18 is associated with lung maturation and play a key role in the corticosteroid-induced expression of surfactant proteins.
Methods: Mouse embryonic lung tissue at different developmental stages (E14.5, E16.5 and E18.5) was collected to detect the temporal-spatial expression of Cldn18 by Western blot and immunofluorescence staining. Dexamethasone + cAMP + isobutylmethylxanthine (DCI), a commonly used agent for inducing maturation of alveolar epithelial cell in vitro, was used to mimic the roles of corticosteroid. Mouse alveolar epithelial cell line MLE12 treated with or without DCI were harvested, expression of Cldn18 and surfactant proteins were assessed by real-time RT-PCR. For Si-RNA experiments, MLE-12 was transfected with control siRNA or Cldn18 siRNA for 24 h before DCI treatment. Expression of Cldn18 and surfactant proteins was assessed by real-time RT-PCR.
Results: Expression of Cldn18 was detected in peripheral lung epithelial cells, and increased expression was detected from E14.5 to E18.5 during lung development. Expression of Cldn18 and surfactants (SPA, SPB and SPC) were significantly induced in MLE12 after DCI treatment. Silencing of Cldn18 effectively suppressed the DCI-induced expression of SPB and SPC but not SPA.
Conclusion: Our results demonstrated that expression of Cldn18 is associated with peripheral lung epithelial cell maturation and play a key role in the corticosteroid-induced expression of surfactant proteins.
Keywords: Claudin18; Corticosteroid; pulmonary epithelial cell; surfactant proteins.