Abstract
The aim of this work was to compare three existing mucus-secreting airway cell lines for use as models of the airways to study drug transport in the presence of mucus.Each cell line secreted mature, glycosylated mucins, evidenced by the enzyme-linked lectin assay. The secretagogue, adenylyl-imidodiphosphate, increased mucin secretion in SPOC1 (3.5-fold) and UNCN3T (1.5-fold) cells but not in Calu-3 cells. In a novel mucus-depleted (MD) model the amount of mucus in the non-depleted wells was 3-, 8- and 4-fold higher than in the mucus-depleted wells of the Calu-3, SPOC1 and UNCN3T cells respectively. The permeability of 'high mucus’ cells to testosterone was significantly less in SPOC1 and UNCN3T cells (P < 0.05) but not Calu-3 cells.Mucin secretion and cytokine release were investigated as indicators of drug irritancy in the SPOC1 and UNCN3T cell lines. A number of inhaled drugs significantly increased mucin secretion at high concentrations and the release of IL-6 and IL-8 from SPOC1 or UNCN3T cells (P < 0.05).SPOC1 and UNCN3T cell lines are better able to model the effect of mucus on drug absorption than the Calu-3 cell line and are proposed for use in assessing drug-mucus interactions in inhaled drug and formulation development.
Highlights
Mucus is a vital component of homeostasis in the upper airways, which extend from the nose to the terminal bronchioles, forming the first line of defence against pathogens and irritants in its function as a chemical, physical and immunological barrier [1]
UNCN3T cells cultured on collagen IV-coated Transwell-ClearTM inserts achieved a mean transepithelial electrical resistance (TEER) of 229 ± 20 Ω.cm2 at 21 days of air–liquid interface (ALI) culture (28 days postseeding) (Fig. 2C), with values above 100 Ω.cm2 being measured ≥ day 11 post seeding
The parameters chosen to determine the suitability of the three cell lines for use as models to study the effect of mucus on drug absorption in the nose and lung were: the ability of the cells to form a tight cell layer, as measured by TEER and the paracellular diffusion of the fluorescent marker FD4; mucin gene expression; secretion of mature, glycosylated mucin; the ability of the cells to secrete mucin in response to a physiological secretagogue; and their ability to show a difference in permeability to testosterone in the presence and absence of mucus
Summary
Mucus is a vital component of homeostasis in the upper airways, which extend from the nose to the terminal bronchioles, forming the first line of defence against pathogens and irritants in its function as a chemical, physical and immunological barrier [1]. The permeability of several human cell lines e.g. 16HBE14o- and Calu-3, which demonstrate a respiratory bronchial epithelial cell-like phenotype and the formation of adequate tight junctions, to drugs and particulates has been studied previously [7,10,11]. Such models simulate the nasal epithelium since the bronchial and nasal epithelium are similar [12]. Such studies rarely consider the effect of mucus as an additional permeability barrier
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