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 as a model cell line, we studied the effects of hyperglycemia in airway epithelial barrier function. Results show increased paracellular dye flux in CF cells in response to insulin treatment under hyperglycemia, suggesting impaired barrier integrity. Gene expression experiments identified Claudin-4 (CLDN4) as a key tight junction protein dysregulated in CF cells. Further investigation into CLDN4 protein localization by confocal microscopy showed that CLDN4 was tightly localized at tight junctions in WT cells and localization did not change under hyperglycemia. ln contrast, CLDN4 was less well-localized in CF cells at normal glucose and localization was worsened in CF cells conditioned to hyperglycemia. Treatment with highly effective modulator compounds (ETI) reversed this trend, and CFTR rescue by ETI in CF cells was not affected by insulin treatment or hyperglycemia. Bulk RNA sequencing showed differences in transcriptional responses in CF compared to WT cells under normal or high glucose, highlighting PTPRG as a promising target for further investigation.