Adenosine protected against pulmonary edema through transporter- and receptor A2-mediated endothelial barrier enhancement.
We have previously demonstrated that adenosine plus homocysteine enhanced endothelial basal barrier function and protected against agonist-induced barrier dysfunction in vitro through attenuation of RhoA activation by inhibition of isoprenylcysteine-O-carboxyl methyltransferase. In the current study, we tested the effect of elevated adenosine on pulmonary endothelial barrier function in vitro and in vivo. We noted that adenosine alone dose dependently enhanced endothelial barrier function. While adenosine receptor A(1) or A(3) antagonists were ineffective, an adenosine transporter inhibitor, NBTI, or a combination of DPMX and MRS1754, antagonists for adenosine receptors A(2A) and A(2B), respectively, partially attenuated the barrier-enhancing effect of adenosine. Similarly, inhibition of both A(2A) and A(2B) receptors with siRNA also blunted the effect of adenosine on barrier function. Interestingly, inhibition of both transporters and A(2A)/A(2B) receptors completely abolished adenosine-induced endothelial barrier enhancement. The adenosine receptor A(2A) and A(2B) agonist, NECA, also significantly enhanced endothelial barrier function. These data suggest that both adenosine transporters and A(2A) and A(2B) receptors are necessary for exerting maximal effect of adenosine on barrier enhancement. We also found that adenosine enhanced Rac1 GTPase activity and overexpression of dominant negative Rac1 attenuated adenosine-induced increases in focal adhesion complexes. We further demonstrated that elevation of cellular adenosine by inhibition of adenosine deaminase with Pentostatin significantly enhanced endothelial basal barrier function, an effect that was also associated with enhanced Rac1 GTPase activity and with increased focal adhesion complexes and adherens junctions. Finally, using a non-inflammatory acute lung injury (ALI) model induced by alpha-naphthylthiourea, we found that administration of Pentostatin, which elevated lung adenosine level by 10-fold, not only attenuated the development of edema before ALI but also partially reversed edema after ALI. The data suggest that adenosine deaminase inhibition may be useful in treatment of pulmonary edema in settings of ALI.
Lu
Qing
Q
Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island 02908, USA.
Harrington
Elizabeth O
EO
Newton
Julie
J
Casserly
Brian
B
Radin
Gregory
G
Warburton
Rod
R
Zhou
Yang
Y
Blackburn
Michael R
MR
Rounds
Sharon
S
D055371:Acute Lung Injury / Q000139:chemically induced / Q000150:complications; D000241:Adenosine / Q000494:pharmacology; D058892:Adenosine Deaminase Inhibitors; D022005:Adherens Junctions / Q000187:drug effects; D000818:Animals; D002417:Cattle; D004727:Endothelium / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D022001:Focal Adhesions / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D033703:Nucleoside Transport Proteins / Q000502:physiology; D015649:Pentostatin / Q000494:pharmacology / Q000627:therapeutic use; D011654:Pulmonary Edema / Q000517:prevention & control; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A / Q000502:physiology; D043704:Receptor, Adenosine A2B / Q000502:physiology; D043683:Receptors, Adenosine A2 / Q000502:physiology*; D013890:Thiourea / Q000031:analogs & derivatives; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D058892:Adenosine Deaminase Inhibitors; D033703:Nucleoside Transport Proteins; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D043683:Receptors, Adenosine A2; C444719:adenosine transporter; D015649:Pentostatin; D020830:rac1 GTP-Binding Protein; D013890:Thiourea; D000241:Adenosine; C005277:alpha-naphthyl thiourea