Respiratory distress leads to local hypoxia of the lung. Hypoxia induces cytoskeletal disruption of alveolar epithelial cells and decreases ZO-1 protein levels dislocating occludin from the cell membrane [75] . Alveolar epithelial cells do not show changes in claudin 3 or 5 protein expression, however [75] . Claudin 5 is known to influence the permeability of endothelial cells. In experiments performed on mice bEND.3 (brain-derived endothelial) and retinal endothelial cells, suppression of claudin 5 mRNA leads to a decrease in transepithelial resistance of these cells [76] . On the other hand, in experimental murine renal ischemia-reperfusion injury there was a significant upregulation of claudin -1, -3, and -7 genes and a slight downregulation of claudin-2 [77] . Additionally, when both of these cells suffer from hypoxia a decrease in claudin 5 mRNA and a lowering of transepithelial resistance was detected [76] .