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. 2021 Nov 19;12:747834. doi: 10.3389/fmicb.2021.747834

FIGURE 4.

FIGURE 4

Ouabain helps restore host defense activities by reversing the acidic pH to neutral pH in differentiated human bronchial epithelial cell cultures. (A) Experimental timeline. pH values were measured on the apical side of air-liquid interface cultured cells before and after 2 h of treatment with/without 20 μM ouabain; PAO1 was then added to the apical side of cultured cells with ouabain or DMSO solvent control for additional 5 h. (B) Effect of ouabain treatment on pH values in non-CF (HBE) and CF epithelial cells. The change of pH in the epithelial apical wash was measured by narrow range pH test strips (pH 6–7.7, resolution 0.3 pH unit; n = 6). (C) Effect of ouabain treatment on P. aeruginosa CFU in non-CF (HBE) and CF epithelial cells. PAO1 was incubated on the apical side of cultured HBE and CF epithelial cells in the existence of 20 μM ouabain or DMSO (solvent control). Biofilm and planktonic CFU were obtained by plated on agar plates for total PAO1 CFU (n = 6). Data were collected from two independent experiments. Unpaired t-test was used for statistical analysis. Data are mean ± SEM. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001; NS, not significant.