Effects of hyperglycemia on airway epithelial barrier function in WT and CF 16HBE cells.

Cystic fibrosis related diabetes (CFRD), the main co-morbidity in cystic fibrosis (CF), is associated with higher rates of lung function decline. We hypothesize that airway epithelial barrier function is impaired in CF and is further exacerbated under hyperglycemia, worsening pulmonary outcomes. Using 16HBE cells, we studied the effects of hyperglycemia in airway epithelial barrier function. Results show increased paracellular dye flux in CF cells in response to insulin under hyperglycemia. Gene expression experiments identified claudin-4 (CLDN4) as a key tight junction protein dysregulated in CF cells. CLDN4 protein localization by confocal microscopy showed that CLDN4 was tightly localized at tight junctions in WT cells, which did not change under hyperglycemia. ln contrast, CLDN4 was less well-localized in CF cells at normal glucose and localization was worsened under hyperglycemia. Treatment with highly effective modulator compounds (ETI) reversed this trend, and CFTR rescue was not affected by insulin or hyperglycemia. Bulk RNA sequencing showed differences in transcriptional responses in CF compared to WT cells under normal or high glucose, highlighting promising targets for future investigation. One of these targets is protein tyrosine phosphatase receptor type G (PTPRG), which has been previously found to play a role in defective Akt signaling and insulin resistance.