Figure 4: Effects of azithromycin (AZM) and ampicillin (ABPC) on TNF-α (20 ng/mL)-induced mucin secretion (a) and MUC5AC mRNA expression (b) from human nasal epithelial cells cultured at air-liquid interface ( ). (a) TNF-α stimulated MUC5AC secretion, and AZM significantly inhibited TNF-α-induced mucin secretion at 10−4 M, whereas ABPC showed no effect. (b) Total RNA was isolated and analyzed for MUC5AC and GAPDH mRNA expression by RT-PCR ( ). AZM significantly inhibited MUC5AC mRNA expression at 10−4 M as demonstrated by the MUC5AC/GAPDH ratio.