Epac1/Rap1 activation ameliorates alcohol‐induced barrier dysfunction

We tested the hypothesis that acute ethanol (EtOH) disrupts endothelial barrier function. Transendothelial electrical resistance (TER) served as an index of barrier function of human umbilical vein endothelial cells treated with EtOH (5–100 mM). The roles of PLD, superoxide generation, and cAMP dependent pathways in EtOH‐induced endothelial barrier changes were tested using 1‐butanol vs. 2‐butanol, the superoxide dismutase (SOD) mimetics MnTBAP and MnTBPyP, and 8‐Br‐cAMP or 8‐CPT‐2″‐O‐Me‐cAMP (8‐CPT; a selective Epac1/Rap1 activator). The results show that EtOH decreased TER in a dose‐related manner. 1‐ and 2‐butanol produced equivalent drops in TER. Pretreatment with SOD mimetics did not inhibit the EtOH‐induced decrease in TER. The cAMP analogs increased TER, but did not alter the magnitude of the EtOH‐induced drop in TER. However, when added 5–10 min. after EtOH, both cAMP analogs shortened the time course of EtOH‐induced barrier dysfunction (58 ± 8min for control vs. 16 ± 0.4 min for 8‐CPT 5 min‐post EtOH and 19 ± 0.6 min for 8‐CPT 10 min‐post EtOH, p<0.01). We conclude that EtOH‐induced endothelial barrier dysfunction is not mediated by PLD, superoxide generation, or inhibition of cAMP‐dependent pathways. However, elevating cytosolic cAMP can resolve EtOH‐induced barrier dysfunction via an Epac1/Rap1 pathway. Supported by NIH P20 RR018766 and a grant from the American Heart Association.