Equilibrative nucleoside transporter 1 (ENT1) regulates postischemic blood flow during acute kidney injury in mice
Almut Grenz, … , Michail Sitkovsky, Holger K. Eltzschig
Almut Grenz, … , Michail Sitkovsky, Holger K. Eltzschig
Published January 24, 2012
Citation Information: J Clin Invest. 2012;122(2):693-710. https://doi.org/10.1172/JCI60214.
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Research Article

Equilibrative nucleoside transporter 1 (ENT1) regulates postischemic blood flow during acute kidney injury in mice

Abstract

A complex biologic network regulates kidney perfusion under physiologic conditions. This system is profoundly perturbed following renal ischemia, a leading cause of acute kidney injury (AKI) — a life-threatening condition that frequently complicates the care of hospitalized patients. Therapeutic approaches to prevent and treat AKI are extremely limited. Better understanding of the molecular pathways promoting postischemic reflow could provide new candidate targets for AKI therapeutics. Due to its role in adapting tissues to hypoxia, we hypothesized that extracellular adenosine has a regulatory function in the postischemic control of renal perfusion. Consistent with the notion that equilibrative nucleoside transporters (ENTs) terminate adenosine signaling, we observed that pharmacologic ENT inhibition in mice elevated renal adenosine levels and dampened AKI. Deletion of the ENTs resulted in selective protection in Ent1–/– mice. Comprehensive examination of adenosine receptor–knockout mice exposed to AKI demonstrated that renal protection by ENT inhibitors involves the A2B adenosine receptor. Indeed, crosstalk between renal Ent1 and Adora2b expressed on vascular endothelia effectively prevented a postischemic no-reflow phenomenon. These studies identify ENT1 and adenosine receptors as key to the process of reestablishing renal perfusion following ischemic AKI. If translatable from mice to humans, these data have important therapeutic implications.

Authors

Almut Grenz, Jessica D. Bauerle, Julee H. Dalton, Douglas Ridyard, Alexander Badulak, Eunyoung Tak, Eóin N. McNamee, Eric Clambey, Radu Moldovan, German Reyes, Jost Klawitter, Kelly Ambler, Kristann Magee, Uwe Christians, Kelley S. Brodsky, Katya Ravid, Doo-Sup Choi, Jiaming Wen, Dmitriy Lukashev, Michael R. Blackburn, Hartmut Osswald, Imogen R. Coe, Bernd Nürnberg, Volker H. Haase, Yang Xia, Michail Sitkovsky, Holger K. Eltzschig

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Figure 1

Renal function and inflammation following inhibition of adenosine transporters during renal ischemia.

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Renal function and inflammation following inhibition of adenosine transp...
(A) Experimental setup to study renal ischemia and reperfusion; DIP, dipyridamole (0.25 mg/25 g mouse i.v., 1 hour before renal ischemia); –I, sham-operated controls; +I, 30 minutes of isolated renal artery occlusion and reperfusion time as indicated. (B) Renal adenosine content measured immediately following 30 minutes of renal ischemia in mice treated with the inhibitor of ENTs dipyridamole or vehicle (+DIP; –DIP; n = 4–6). KW, kidney weight. (C) Renal adenosine content in mice pretreated with PEG-ADA (5 U/mouse 24 hours before renal ischemia; n = 4). (D) GFR following 30 minutes of renal ischemia and 1 hour of reperfusion (n = 4–6). (E) Serum creatinine levels following 30 minutes of renal ischemia and 24 hours of reperfusion (n = 4–6). (F–H) TNFα, Il6, and Il10 transcript levels after 30 minutes of renal ischemia and 2 hours of reperfusion by real-time RT-PCR relative to the housekeeping gene β-actin (n = 4–6). (I) Histologic staining for apoptosis (as determined by TUNEL staining) in kidneys exposed to 30 minutes of ischemia and 24 hours of reperfusion (original magnification, ×400; fluorescent green [arrows]: staining for apoptosis; 1 representative image of 3 is shown). (J) Quantification of renal apoptosis by counting positive cells in 5–10 ×400 fields.