Abstract 5267: The Annexin A5 Homodimer Diannexin Protects Against Ischemia Reperfusion Injury Through Phosphatidylserine Binding
Renal ischemia/reperfusion injury (IRI) frequently complicates cardiac and aortic surgery and has prognostic significance. The translocation of phosphatidylserines (PS) to cell surfaces is an important pro-inflammatory signal for cell-stress after IRI. We hypothesized that shielding of exposed PS by the annexin A5 homodimer Diannexin protects against renal IRI. Mice (n =8 – 10) underwent 20 min bilateral clamping of the renal pedicle, followed by 3 or 8 days of reperfusion. Either 200 ug/kg Diannexin or vehicle was injected i.v. 20 min prior to ischemia. Renal injury peaked on day 3 post-op. When compared to vehicle, Diannexin treatment reduced the IRI-induced glucosuria, prevented the increase in urine flow, reduced the proximal tubule damage and reduced the expression and/or transcription of the renal injury markers Neutrophil Gelatinase Associated Lipocalin (NGAL) and Kidney Injury Molecule-1 (KIM-1; see table⇓). Reduced KIM-1 expression persisted on day 8 after Diannexin treatment [0.23±0.02 vs. 0.36±0.06; p<0.05]. To confirm PS as the target for Diannexin, mice (n=2– 6) underwent unilateral IRI of the hind limb. Upon reperfusion, 4.5 ug Tc-99m-Diannexin was injected i.v.. Diannexin targeted specifically to the ischemic limb when compared to the control limb [4.0±0.60 vs. 0.2±0.02 %ID/g; p<0.001]. Targeting could be reduced by a preceding injection of 500 ug unlabeled annexin A5 [1.5±0.3 vs. 0.7±0.2 %ID/g], suggesting that Diannexin targets to ischemic tissues via PS binding. This study indicates the importance of PS exposition in IRI. We conclude that Diannexin protects against renal IRI by binding to PS, making it a promising tool to prevent IRI in a clinical setting.