Background: Alkaline serine proteases from six prevalent airborne Penicillium and Aspergillus species have been identified as a group of major allergens (group 13). After entering human airways, the allergens are in initial contacts with respiratory epithelial cells. The purpose of this study is to investigate interactions between the Pen ch 13 allergen from P. chrysogenum and human lung epithelial cells.
Methods: A549 cells, 16HBE14o- cells and primary cultures of human bronchial epithelial cells (HBEpC) were exposed to purified Pen ch 13 and mediators released into culture supernatants were assayed with enzyme-linked immunosorbent assay (ELISA) kits. Cleavage of occludin in 16HBE14o- cells was analysed by immunofluorescent staining of whole cells and immunoblot analysis of whole cell extracts. Fragments generated by incubating Pen ch 13 and a synthetic peptide carrying the occludin sequence were analysed by mass spectrometry.
Results: Pen ch 13 induced productions of prostaglandin-E2 (PGE2), interleukin (IL)-8 and transforming growth factor (TGF)-β1 by A549 cells, 16HBE14o- cells and primary cultures of HBEpC. The protease activity of Pen ch 13 is needed for the induction of PGE2, IL-8, TGF-β1 and cyclo-oxygenase (COX)-2 expression. A tight junction protein occludin of 16HBE14o- cells can be cleaved by Pen ch 13 at Gln202 and Gln211 which are within the second extracellular domain of the protein.
Conclusion: Pen ch 13 may contribute to asthma by damaging the barrier formed by the airway epithelium and stimulating the release of mediators that orchestrate local immune responses and inflammatory process from HBEpC.