Obesity-related palmitic acid exacerbates IL-13-induced mucus phenotype in 16HBE airway epithelial cells via AMPK suppression.

BACKGROUND

Mucus hypersecretion and obesity are two prevalent comorbidities that independently worsen childhood asthma outcomes. However, the metabolic mechanisms by which obesity-related factors interact with type 2 (T2) inflammatory signals to exacerbate airway epithelial mucus phenotype remain poorly understood. This study aimed to investigate whether palmitic acid (PA), a representative obesity-related saturated fatty acid, amplifies interleukin-13 (IL-13)-induced mucus phenotype in human bronchial epithelial cells and to determine whether the AMP-activated protein kinase (AMPK) axis mediates this interaction.

METHODS

We stimulated 16HBE human bronchial epithelial cells with IL-13 (10 ng/mL, 72 h), PA (100 µM, 48 h), or combined IL-13 and PA exposure, in which PA was added during the final 48 h of IL-13 treatment. We activated AMPK pharmacologically with AICAR (1 mM) and suppressed AMPK genetically through small interfering RNA (siRNA)-mediated PRKAA1 knockdown. We quantified MUC5AC, MUC5B, CLCA1, and PRKAA1 messenger RNA (mRNA) transcripts by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), measured IL-8 secretion by enzyme-linked immunosorbent assay (ELISA), assessed AMPKα, phosphorylated acetyl-CoA carboxylase (p-ACC), and acetyl-CoA carboxylase (ACC) by Western blot, and evaluated MUC5AC and zonula occludens-1 (ZO-1) localization by immunofluorescence.

RESULTS

Combined IL-13 and PA stimulation markedly elevated MUC5AC and CLCA1 mRNA and protein expression beyond IL-13 alone (P<0.001). In addition, combined stimulation further increased IL-8 secretion (P<0.001), indicating a stronger pro-inflammatory epithelial response after combining inflammatory and metabolic stimuli. In parallel, the p-ACC/ACC ratio, an indicator of AMPK activity, was lowest after combined IL-13 and PA exposure (P<0.001). AMPK activation with AICAR partially reversed MUC5AC, CLCA1, and IL-8 upregulation and restored ZO-1 continuity (P<0.001), whereas PRKAA1 knockdown further aggravated MUC5AC expression (P<0.01) and reduced p-ACC levels (P<0.05).

CONCLUSIONS

PA amplifies IL-13-induced airway epithelial mucus phenotype through suppression of the AMPK axis. AMPK may represent a potential therapeutic target for mucus hypersecretion in obesity-related childhood asthma.