Abstract 975: Heat Shock Protein 90 Inhibitors Protect And Restore Pulmonary Endothelial Barrier Function.
Heat shock protein 90 (hsp 90) inhibitors inactivate and/or degrade various client proteins, including many involved in inflammation. Disruption of endothelial barrier and increased vascular permeability is a hallmark of many pathological conditions including inflammation, atherosclerosis, acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Recently we have demonstrated that the hsp90 inhibitor, radicicol (RA) effectively, protects from LPS-induced endothelial cell (EC) injury, in vivo and in vitro. Thus we tested hypothesis that hsp90 inhibitors may prevent and/or restore EC permeability after receptor- and non receptor-mediated injury. Exposure of confluent bovine pulmonary artery endothelial cell (BPAEC) monolayers to TGFβ1 (10ng/ml), thrombin (100nM), LPS (1000EU/ml) or VEGF (50ng/ml) increased BPAEC permeability, as revealed by decreased transendothelial electrical resistance (TER). Treatment of injured endothelium (2–3hrs after injury, at the nadir of the TER response) with an hsp90 inhibitor (RA, 17-AAG or 17-DMAG; 1μg/ml) completely restored TER of BPAEC to levels even higher than control. Similarly, pre-incubation of BPAEC with hsp90 inhibitors for 3–18 hrs prevented the decline in TER induced by exposure to thrombin, LPS, VEGF or TGFβ1. Additionally, hsp90 inhibitors restored EC barrier function after the non-receptor, PMA (100nM)- or nocodazole (5μg/ml)- induced hyperpermeability. These effects of the hsp90 inhibitors were associated with restoration of TGFβ1- or nocodazole-induced decrease in VE-cadherin and β-catenin expression at EC junctions and with maintenance of EC monolayer integrity, as revealed by silver nitrate staining. The protective effects of hsp90 inhibitors were also associated with inhibition of MLC and MYPT-1 phosphorylation, but were independent of p38MAPK activation. We conclude that hsp90 inhibitors exert barrier protective effect on BPAEC and therefore may have useful therapeutic value in ALI, ARDS and other pulmonary inflammatory disease.