The Reno-Vascular A2B Adenosine Receptor Protects the Kidney from Ischemia

Abstract

BackgroundAcute renal failure from ischemia significantly contributes to morbidity and mortality in clinical settings, and strategies to improve renal resistance to ischemia are urgently needed. Here, we identified a novel pathway of renal protection from ischemia using ischemic preconditioning (IP).Methods and FindingsFor this purpose, we utilized a recently developed model of renal ischemia and IP via a hanging weight system that allows repeated and atraumatic occlusion of the renal artery in mice, followed by measurements of specific parameters or renal functions. Studies in gene-targeted mice for each individual adenosine receptor (AR) confirmed renal protection by IP in A1−/−, A2A−/−, or A3AR−/− mice. In contrast, protection from ischemia was abolished in A2BAR−/− mice. This protection was associated with corresponding changes in tissue inflammation and nitric oxide production. In accordance, the A2BAR-antagonist PSB1115 blocked renal protection by IP, while treatment with the selective A2BAR-agonist BAY 60–6583 dramatically improved renal function and histology following ischemia alone. Using an A2BAR-reporter model, we found exclusive expression of A2BARs within the reno-vasculature. Studies using A2BAR bone-marrow chimera conferred kidney protection selectively to renal A2BARs.ConclusionsThese results identify the A2BAR as a novel therapeutic target for providing potent protection from renal ischemia.

CD73-Dependent Generation of Adenosine and Endothelial Adora2b Signaling Attenuate Diabetic Nephropathy

“…According to these findings, we next examined Adora2b protein expression using a previously described Adora2b gene reporter mouse. 47 Consistent with previous studies, 23,24 we observed that Adora2b protein expression at baseline was predominantly associated with vascular structures ( Figure 4E). Moreover, Adora2b induction at 16 weeks after STZ treatment was dramatically increased at vascular sites ( Figure 4E).…”

“…We had shown in several previous studies that this compound has pharmacologic effects in wild-type or Adora2a 2/2 mice, but not in Adora2b 2/2 mice. 24,31,50,51 For the purpose of our studies, we administered BAY 60-6583 via osmotic pump (0.3 mg per mouse per hour). Indeed, we observed that continuous BAY 60-6583 treatment had no effect on systolic BP or blood glucose levels (Supplemental Figure 6, A and B) but was associated with an attenuated wasting syndrome after STZ treatment ( Figure 8, A-D).…”

“…24,25 Tissues were homogenized and lysed for 10 minutes in ice-cold lysis buffer (150 mM NaCl, 25 mM Tris [pH 8.0], 5 mM EDTA, 2% Triton X-100, and 10% mammalian tissue protease inhibitor cocktail; Sigma-Aldrich), and further processed as previously described. 23 To control for protein loading, blots were stripped in stripping buffer for 30 minutes and washed for 10 minutes with Tris-buffered saline and Tween 20, and membranes were blocked for 1 hour at room temperature in PBS-Tween and 4% BSA.…”

“…9,18,20 Once generated into the extracellular compartment, adenosine can signal through four distinct adenosine receptors (Adora1, Adora2a, Adora2b, or Adora3). Previous studies had implicated CD73-dependent generation of extracellular adenosine and concomitant adenosine signaling in tissue protection during conditions of acute tissue injury, such as AKI, [21][22][23][24][25][26] hepatic 10,20,27 or intestinal 17,18,28 ischemia, or myocardial infarction. 10,[29][30][31][32] In contrast, the functional role of extracellular adenosine generation and signaling during chronic disease states is less clear.…”

Preserving postischemic reperfusion in the kidney: a role for extracellular adenosine

“…Adora2a on both neutrophils and T cells has potent, protective, anti-inflammatory effects (14). Adora2b has been shown to be necessary for ischemic preconditioning in the kidney (15).…”