(A) Bioinformatics analysis identified the existence of previously unreported PPREs in the human MUC5AC promoter. The schematic diagram shows the location of those PPREs relative to the transcription start site (TSS); numbers refer to the nucleotide position within the promoter region. (B) NHBE cells were transfected, in the presence or absence of PPARγ expression plasmid, with luciferase constructs containing the WT MUC5AC promoter (construct 1) or promoters with one (constructs 3 and 4) or both (construct 2) of the putative PPREs deleted (ΔPPRE). Empty pGL4 served as a negative control for the assay. The luciferase activities were determined after 24 h. The data are expressed as the mean ± SD with n = 3, and the results were reproduced at least two times independently; *P < 0.05, **P < 0.01, ***P < 0.001, n.s. = non-significant.