Department of Anesthesiology, Columbia University, 630 W. 168th St., New York, NY 10032-3784, USA.
Am J Physiol Renal Physiol. 2012 Sep;303(5):F721-32. doi: 10.1152/ajprenal.00157.2012. Epub 2012 Jul 3.
Activation of A(1) adenosine receptors (ARs) protects against renal ischemia-reperfusion (I/R) injury by reducing necrosis, apoptosis, and inflammation. However, extrarenal side effects (bradycardia, hypotension, and sedation) may limit A(1)AR agonist therapy for ischemic acute kidney injury. Here, we hypothesized that an allosteric enhancer for A(1)AR (PD-81723) protects against renal I/R injury without the undesirable side effects of systemic A(1)AR activation by potentiating the cytoprotective effects of renal adenosine generated locally by ischemia. Pretreatment with PD-81723 produced dose-dependent protection against renal I/R injury in A(1)AR wild-type mice but not in A(1)AR-deficient mice. Significant reductions in renal tubular necrosis, neutrophil infiltration, and inflammation as well as tubular apoptosis were observed in A(1)AR wild-type mice treated with PD-81723. Furthermore, PD-81723 decreased apoptotic cell death in human proximal tubule (HK-2) cells in culture, which was attenuated by a specific A(1)AR antagonist (8-cyclopentyl-1,3-dipropylxanthine). Mechanistically, PD-81723 induced sphingosine kinase (SK)1 mRNA and protein expression in HK-2 cells and in the mouse kidney. Supporting a critical role of SK1 in A(1)AR allosteric enhancer-mediated renal protection against renal I/R injury, PD-81723 failed to protect SK1-deficient mice against renal I/R injury. Finally, proximal tubule sphingosine-1-phosphate type 1 receptors (S1P(1)Rs) are critical for PD-81723-induced renal protection, as mice selectively deficient in renal proximal tubule S1P(1)Rs (S1P(1)R(flox/flox) PEPCK(Cre/-) mice) were not protected against renal I/R injury with PD-81723 treatment. Taken together, our experiments demonstrate potent renal protection with PD-81723 against I/R injury by reducing necrosis, inflammation, and apoptosis through the induction of renal tubular SK1 and activation of proximal tubule S1P(1)Rs. Our findings imply that selectively enhancing A(1)AR activation by locally produced renal adenosine may be a clinically useful therapeutic option to attenuate ischemic acute kidney injury without systemic side effects.
A(1) 腺苷受体 (AR) 的激活通过减少坏死、凋亡和炎症来保护肾脏免受缺血再灌注 (I/R) 损伤。然而，肾外副作用（心动过缓、低血压和镇静）可能会限制 A(1)AR 激动剂治疗缺血性急性肾损伤的应用。在这里，我们假设 A(1)AR 的变构增强剂 (PD-81723) 通过增强局部缺血产生的肾腺苷的细胞保护作用，而不会产生全身 A(1)AR 激活的不良副作用，从而防止肾 I/R 损伤。PD-81723 在 A(1)AR 野生型小鼠中产生了剂量依赖性的肾 I/R 损伤保护作用，但在 A(1)AR 缺陷型小鼠中则没有。在接受 PD-81723 治疗的 A(1)AR 野生型小鼠中，观察到肾小管坏死、中性粒细胞浸润和炎症以及肾小管凋亡显著减少。此外，PD-81723 降低了培养的人近端肾小管 (HK-2) 细胞中的凋亡细胞死亡，而这种作用被特异性 A(1)AR 拮抗剂 (8-环戊基-1,3-二丙基黄嘌呤) 减弱。在机制上，PD-81723 诱导 HK-2 细胞和小鼠肾脏中的鞘氨醇激酶 (SK)1 mRNA 和蛋白表达。支持 SK1 在 A(1)AR 变构增强剂介导的肾 I/R 损伤保护中的关键作用，PD-81723 未能保护 SK1 缺陷型小鼠免受肾 I/R 损伤。最后，近端肾小管鞘氨醇-1-磷酸 1 型受体 (S1P(1)Rs) 对 PD-81723 诱导的肾保护至关重要，因为选择性缺乏肾近端小管 S1P(1)Rs 的小鼠 (S1P(1)R(flox/flox)PEPCK(Cre/-) 小鼠) 没有得到保护免受肾 I/R 损伤与 PD-81723 治疗。总之，我们的实验表明，PD-81723 通过诱导肾小管 SK1 和激活近端小管 S1P(1)Rs 减少坏死、炎症和凋亡，对 I/R 损伤具有强大的肾保护作用。我们的发现表明，通过局部产生的肾腺苷选择性增强 A(1)AR 激活可能是一种有临床应用价值的治疗选择，可减轻缺血性急性肾损伤而不会产生全身副作用。
