Tight junction properties of the immortalized human bronchial epithelial cell lines Calu-3 and 16HBE14o-

Tight junctions (TJs) make a vital contribution to the barrier properties of the airway lining. Opening of TJs, or their frank cleavage, is suspected as a pathophysiological event in the lung, but research into the cellular and molecular mechanisms involved has been impeded by technical limitations of available experimental models. The authors have compared the properties of two epithelial cell lines derived from bronchial epithelium to explore whether these cell lines could constitute appropriate tools for the study of TJ regulation in bronchial epithelium. Investigations of TJs in 16HBE14o- cells and Calu-3 cells were made by fluorescent antibody labelling in conjunction with wide-field, confocal or 2-photon molecular excitation microscopy (2PMEM). The presence of TJ proteins was confirmed by immunoblotting and functional properties of the monolayers were studied by measurements of transepithelial electrical resistance and mannitol permeability. Cells of both lines formed confluent monolayers in which the cells expressed the TJ proteins occludin and ZO-1 in continuous circumferential patterns suggestive of functional TJs. This interpretation was supported by the development of transepithelial electrical resistances and of low paracellular permeability to solutes. Within the limits of resolution offered by 2PMEM, occludin and ZO-1 appeared to colocalize at TJs. These studies suggest that the 16HBE14o- cells and Calu-3 cell lines are potentially useful in vitro models to study how tight junction opening or cleavage changes the functional barrier properties of bronchial epithelium.