Inflammatory response and barrier properties of a new alveolar type 1-like cell line (TT1)

Abstract

Purpose: To evaluate the inflammatory response and barrier formation of a new alveolar type 1-like (transformed type I; TT1) cell line to establish its suitability for toxicity and drug transport studies.

Methods: TT1 and A549 cells were challenged with lipopolysaccharide (LPS). Secretion of inflammatory mediators was quantified by ELISA. The barrier properties of TT1 cells were evaluated by transepithelial electrical resistance (TEER), fluorescein sodium (flu-Na) apparent permeability (P(app)) and staining of zona occludens-1 (ZO-1).

Results: LPS stimulated similar levels of secretion of IL-6 and IL-8 in TT1 and A549 cells. TNF-alpha was not produced by either cell line. In contrast to A549 cells, TT1 cells did not secrete SLPI or elafin. TT1 cells produced maximal TEER of approximately 55 ohms cm(2) and flu-Na P(app) of approximately 6.0 x 10(-6) cm/s. ZO-1 staining was weak and discontinuous. Attempts to optimise culture conditions did not increase the barrier properties of the TT1 cell layers.

Conclusions: The TT1 cell line models the alveolar inflammatory response to LPS challenge and provides a valuable complement to cell lines currently used in toxicity assays. However, under the experimental conditions used the TT1 cell line did not form the highly restrictive tight junctions which exist in vivo.