PMA synergistically enhances NTHi-induced MUC5AC expression via MKK3/6-p38 MAPK pathway.

<p>(<b>A</b>) PMA synergistically enhanced NTHi-induced phosphorylation of p38 MAPK and MKK3/6, but not ERK and MEK1. (<b>B</b>) The synergistic induction of MUC5AC transcription by NTHi and PMA was inhibited by overexpressing DN mutant forms of p38α and p38β in human epithelial cells, as assessed by MUC5AC-dependent promoter Luciferase assay. Cells were transfected with 0.8 µg of DN p38α, DN p38β, or control vector, and treated with NTHi with or without PMA. Relative luciferase activity of MUC5AC was measured from the cell lysate. (<b>C</b>) SB203580, a specific inhibitor for p38 MAPK signaling, attenuated the synergistic induction of MUC5AC expression by NTHi and PMA at the mRNA level as assessed by Q-PCR. Cells were pre-treated with 10 µM of SB203580 or vehicle control, and treated with NTHi with or without PMA. mRNA expression level of MUC5AC was measured by Q-PCR. Values are the means ± S.D. (n = 3). <i>*p<0.05</i> vs. control; <i>**p<0.05</i> vs. NTHi alone; <i>***p<0.05</i> vs NTHi with PMA in control vector transfected (<b>B</b>) or vehicle treated (<b>C</b>) cells. The data shown are representative of three independent experiments. −, absence of; +, presence of; DN, dominant negative; NTHi, nontypeable <i>Haemophilus influenzae</i>.