Journal
AMERICAN JOURNAL OF KIDNEY DISEASES
Volume 53, Issue 4, Pages 584-595Publisher
W B SAUNDERS CO-ELSEVIER INC
DOI: 10.1053/j.ajkd.2008.10.037
Keywords
Ischemia-reperfusion injury; hepcidin; IP-10; CXCR3 chemokine
Categories
Funding
- Bristol Myers Squibb Cardiovascular Research Fellowship
- Canadian Institutes of Health Research
- Coplan Extramural Satellite Health Research
- Department of Medicine, University of Manitoba
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Background: The early evolution of acute kidney injury (AKI) in humans is difficult to study noninvasively. We hypothesized that urine proteomics could provide insight into the early pathophysiology of human AKI. Study Design: A prospective nested case-control study (n = 250) compared serial urinary proteomes of 22 patients with AKI and 22 patients without AKI before, during, and after cardiopulmonary bypass surgery. Outcomes: AKI was defined as a greater than 50% increase in serum creatinine level, and non-AKI, as less than 10% increase from baseline. Measurements: Serum creatinine, urine protein-creatinine ratio, neutrophil gelatinase-associated lipocalin (NGAL), alpha(1)-microglobulin, interferon-inducible protein-10 (IP-10), monokine induced by interferon gamma (Mig), interferon-inducible T cell alpha chemoatractant (I-TAC), interleukin 6 (IL-6), IL-1 beta, and IL-10. Urine protein profiling by means of surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Results: SELDI-TOF-MS showed intraoperative tubular stress in both groups on arrival to the intensive care unit, evidenced by beta(2)-microglobulinuria. Non-AKI proteomes returned toward baseline postoperatively. In contrast, AKI proteomes showed a second phase of tubular injury/stress with the reappearance of beta(2)-microglobulin and multiple unidentified peaks (3 to 5 and 6 to 8 kDa) and the appearance of established tubular injury markers: urinary protein, alpha(1)-microglobulin, and NGAL. Furthermore, 2 novel peaks (2.43 and 2.78 kDa) were found to be dominant in postoperative non-AKI urine samples. The 2.78-kDa protein was identified as the active 25-amino acid form of hepcidin (hepcidin-25), a key regulator of iron homeostasis. Finally, an inflammatory component of reperfusion injury was evaluated by means of enzyme-linked immunosorbent assay analysis of candidate chemokines (IP-10, I-TAC, and Mig) and cytokines (IL-6, IL-1 beta, and IL-10). Of these, IP-10 was upregulated in patients with versus without AKI postoperatively. Limitations: This is an observational study. SELDI-TOF-MS is a semiquantitative technique. Conclusions: Evaluation of human AKI revealed early intraoperative tubular stress in all patents. A second phase of injury observed in patients with AKI may involve IP-10 recruitment of inflammatory cells. The enhancement of hepcidin-25 in patents without AKI may suggest a novel role for iron sequestration in modulating AKI. Am J Kidney Dis 53:584-595. (C) 2009 by the National Kidney Foundation, Inc.
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