Abstract
Our previous study demonstrated that proinflammatory cytokines increase protein permeability across human alveolar type II (AT II) cell monolayers (J Biol Chem 2007). However, the mechanisms are not fully understood. The family of claudin transmembrane proteins had been implicated in the regulation of epithelial paracellular permeability. In this study we determined the gene profile of cultured human AT II cells exposed to cytomix (TNF‐α, IL‐1β and IFN‐γ) to identify candidate genes that may contribute to the increase in protein permeability. Human AT II cells were isolated and cultured on collagen‐coated wells. After 48 hr, the cells were exposed to serum‐free medium (control) or cytomix for 72hr. cDNA was prepared and hybridized to Affymetrix U133A microarray chips. Western blot was used to test for protein expression of candidate genes. mRNA was detected at a significant level for 50% of the probes, representing approximately 7200 genes. Although mRNAs for claudin 1, 3, 4, 6, 7, 8, 9, 10, 15, 18 were detected, only claudin 18 mRNA was significantly decreased (95%) by cytomix exposure. Western blot confirmed that protein expression of claudin‐18 was significantly reduced by cytomix. The reduction of claudin 18 expression was restored by the NF‐kB inhibitor, BMS‐345541. We conclude that claudin 18 is regulated by cytokines and may play a role in protein permeability change across human ATII cell monolayers.
Published Version
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