title: Sustained adenosine exposure causes lung endothelial barrier dysfunction via nucleoside transporter-mediated signaling.
abstract: Previous studies by our group as well as others have shown that acute adenosine exposure enhances lung vascular endothelial barrier integrity and protects against increased permeability lung edema. In contrast, there is growing evidence that sustained adenosine exposure has detrimental effects on the lungs, including lung edema. It is well established that adenosine modulates lung inflammation. However, little is known concerning the effect of sustained adenosine exposure on lung endothelial cells (ECs), which are critical to the maintenance of the alveolar-capillary barrier. We show that exogenous adenosine plus adenosine deaminase inhibitor caused sustained elevation of adenosine in lung ECs. This sustained adenosine exposure decreased EC barrier function, elevated cellular reactive oxygen species levels, and activated p38, JNK, and RhoA. Inhibition of equilibrative nucleoside transporters (ENTs) prevented sustained adenosine-induced p38 and JNK activation and EC barrier dysfunction. Inhibition of p38, JNK, or RhoA also partially attenuated sustained adenosine-induced EC barrier dysfunction. These data indicate that sustained adenosine exposure causes lung EC barrier dysfunction via ENT-dependent intracellular adenosine uptake and subsequent activation of p38, JNK, and RhoA. The antioxidant N-acetylcysteine and the NADPH inhibitor partially blunted sustained adenosine-induced JNK activation but were ineffective in attenuation of p38 activation or barrier dysfunction. p38 was activated exclusively in mitochondria, whereas JNK was activated in mitochondria and cytoplasm by sustained adenosine exposure. Our data further suggest that sustained adenosine exposure may cause mitochondrial oxidative stress, leading to activation of p38, JNK, and RhoA in mitochondria and resulting in EC barrier dysfunction.
authors: Alpert Medical School of Brown University, Providence VA Medical Center, Research Services, 830 Chalkstone Avenue, Providence, RI 02908, USA. Qing_Lu@brown.edu
authors: Qing
authors: Q
authors: Lu
authors: Julie
authors: J
authors: Newton
authors: Vivian
authors: V
authors: Hsiao
authors: Paul
authors: P
authors: Shamirian
authors: Michael R
authors: MR
authors: Blackburn
authors: Mesias
authors: M
authors: Pedroza
mesh_terms: D000241:Adenosine / Q000494:pharmacology / Q000502:physiology*; D000243:Adenosine Deaminase / Q000378:metabolism; D058892:Adenosine Deaminase Inhibitors / Q000494:pharmacology; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002199:Capillary Permeability; D002417:Cattle; D002478:Cells, Cultured; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D004789:Enzyme Activation; D033705:Equilibrative Nucleoside Transport Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018384:Oxidative Stress; D015649:Pentostatin / Q000494:pharmacology; D011651:Pulmonary Artery / Q000473:pathology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D022502:Stress Fibers / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D058892:Adenosine Deaminase Inhibitors; D033705:Equilibrative Nucleoside Transport Proteins; D017382:Reactive Oxygen Species; D015649:Pentostatin; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000243:Adenosine Deaminase; D020742:rhoA GTP-Binding Protein; D000241:Adenosine