Figure 6.

SMAD signaling inhibition overrides the suppressive effect of γ-aminobutyric acid (GABA) receptor inhibitor in goblet cell production. (A) Human airway basal cells derived from a representative healthy donor were cultured on ALI for 16 days and treated with IL-13 (20 ng/ml) for 4 days to induce goblet cell hyperplasia. SMAD signaling inhibitors (1 μM A8301 + 1 μM DMH-1) and GABAergic system receptor (100 μM picrotoxin), or in combination, were included in ALI culture to examine their effects on goblet cell generation. ALI membranes were fixed and stained with MUC5AC antibody. Scale bars: 100 μm. (B) Quantification of MUC5AC production in the experiment shown in A. MUC5AC index was calculated based on the total area of MUC5AC positivity out of total imaging area. The score was relative to the control (without IL-13 stimulation; mean ± SD; n = 3 independent imaging fields; *P ≤ 0.01 and **P ≤ 0.001).