Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island 02908, USA.
Am J Physiol Lung Cell Mol Physiol. 2010 Jun;298(6):L755-67. doi: 10.1152/ajplung.00330.2009. Epub 2010 Mar 12.
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.
我们之前已经证明，腺苷和同型半胱氨酸通过抑制异戊烯基半胱氨酸-O-羧甲基转移酶来减弱 RhoA 的激活，从而增强内皮细胞的基础屏障功能并防止激动剂诱导的屏障功能障碍。在本研究中，我们测试了升高的腺苷对体外和体内肺内皮屏障功能的影响。我们注意到，腺苷本身剂量依赖性地增强内皮细胞屏障功能。虽然腺苷受体 A(1)或 A(3)拮抗剂无效，但腺苷转运蛋白抑制剂 NBTI 或腺苷受体 A(2A)和 A(2B)拮抗剂 DPMX 和 MRS1754 的组合部分减弱了腺苷的屏障增强作用。同样，用 siRNA 抑制两种 A(2A)和 A(2B)受体也削弱了腺苷对屏障功能的影响。有趣的是，同时抑制转运体和 A(2A)/A(2B)受体完全消除了腺苷诱导的内皮屏障增强。腺苷受体 A(2A)和 A(2B)激动剂 NECA 也显著增强了内皮屏障功能。这些数据表明，腺苷转运体和 A(2A)和 A(2B)受体都是发挥腺苷对屏障增强的最大作用所必需的。我们还发现，腺苷增强 Rac1 GTPase 活性，过表达显性失活 Rac1 减弱了腺苷诱导的焦点黏附复合物的增加。我们进一步证明，通过用戊烯司他丁抑制腺苷脱氨酶来升高细胞内腺苷水平显著增强内皮基础屏障功能，该效应还与 Rac1 GTPase 活性的增强以及焦点黏附复合物和黏着连接的增加相关。最后，使用由α-萘基硫脲诱导的非炎症性急性肺损伤 (ALI) 模型，我们发现，戊烯司他丁给药可使肺腺苷水平升高 10 倍，不仅在 ALI 前减轻了水肿的发展，而且部分逆转了 ALI 后的水肿。这些数据表明，腺苷脱氨酶抑制可能在 ALI 情况下的肺水肿治疗中有用。
