Abstract 209: Inhibition of AMP-Activated Protein Kinase Accentuates Lipopolysaccharides-Induced Lung Endothelial Barrier Dysfunction and Lung Injury in Vivo

Abstract

AMP-activated protein kinase (AMPK) is reported to have vascular protective effects, but whether AMPK regulates endothelial barrier functions and protects lung function remains unknown. The aim of this study was to determine the roles of AMPK in lipopolysaccharide (LPS)-induced lung endothelial barrier dysfunction ( in vitro and in vivo ) and lung injury ( in vivo ). Cultured human pulmonary artery endothelial cells (HPAECs) and AMPKα subunit-deficient mice and wild-type (WT) control (C57BL/6J) mice were used to study the molecular mechanisms by which LPS induced lung endothelial barrier dysfunction and lung injury. In cultured HPAECs, LPS markedly increased endothelial hyperpermeabilty in parallel with a marked decrease in both AMPK phosphorylation at Thr172 and AMPK activity. Consistent with this latter observation, AMPK activation with AICAR treatment attenuated LPS-induced endothelial hyperpermeabilty in vitro . Intratracheal administration of LPS (1 mg/kg) in WT C57BL6 mice markedly reduced AMPK phosphorylation at Thr172 in lung tissue extracts, but markedly increased protein contents and cell numbers in bronchial aveolar lavage fluid and Evans blue dye infiltration in the lung in vivo . Pretreatment with AICAR, a potent AMPK activator, markedly reduced LPS-enhanced protein contents, cell counts, and inflammatory cell infiltration into alveolae. These lung injury indicators were significantly enhanced in AMPK-knockout mice compared to WT C57BL6 mice, supporting that AMPK inhibition by LPS accentuated lung injury. Mechanistically, we found that AMPK activation with AICAR attenuated LPS-induced endothelial hyperpermeabilty by activating the Rac/Cdc42/PAK pathway with concomitant inhibition of the Rho pathway, and decreased VE-cadherin phosphorylation at Tyr 658 . We conclude that (1) LPS inhibits AMPK; (2) AMPK inhibition accelerates LPS-induced endothelial barrier dysfunction and lung injury; and (3) AMPK activation attenuates LPS-induced pulmonary vascular hyperpermeability and lung injury.