Fig. 8.

Upregulation and activation of P2X₄ augment mucin secretion. MUC5AC secretion was assessed by ELISA. A: stimulation of mucin secretion with 100 μM ATP or 100 μM UTP in control (untreated) and IL-13-treated cultures. Agonist treatment resulted in significantly increased MUC5AC secretion in IL-13-treated cells. B: stimulation of mucin secretion with 100 μM ATP in control and IL-13-treated cultures where P2X₄ activity was modulated by overexpression of wild-type (wt) P2X₄-EGFP, the P2X₄ potentiator ivermectin (iverm, 3 μM), the P2X₄ inhibitor 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD, 30 μM), or overexpression of the dominant-negative (dn) mutant P2X₄(C353W)-EGFP. No effects were observed in control cultures, whereas P2X₄ activation resulted in a significant increase and P2X₄ inhibition in a significant decrease of mucin secretion in IL-13-treated cultures. C: stimulation of mucin secretion with 100 μM UTP in control and IL-13-treated cultures where P2X₄ activity was modulated. The effects of modulating P2X₄ activity on mucin secretion in IL-13 treated cultures were absent in cells stimulated with 100 μM UTP, which stimulates mucin secretion but does not activate P2X₄ receptors. Means are derived from 5–12 individual experiments. Statistical significance was assessed by Kruskal-Wallis test for multiple comparisons. *P < 0.05; **P < 0.01; ***P < 0.001.