Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury
Kiyoshi Mori, … , Prasad Devarajan, Jonathan Barasch
Kiyoshi Mori, … , Prasad Devarajan, Jonathan Barasch
Published March 1, 2005
Citation Information: J Clin Invest. 2005;115(3):610-621. https://doi.org/10.1172/JCI23056.
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Article Nephrology

Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury

Abstract

Neutrophil gelatinase–associated lipocalin (Ngal), also known as siderocalin, forms a complex with iron-binding siderophores (Ngal:siderophore:Fe). This complex converts renal progenitors into epithelial tubules. In this study, we tested the hypothesis that Ngal:siderophore:Fe protects adult kidney epithelial cells or accelerates their recovery from damage. Using a mouse model of severe renal failure, ischemia-reperfusion injury, we show that a single dose of Ngal (10 μg), introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia. Ngal activity depends on delivery of the protein and its siderophore to the proximal tubule. Iron must also be delivered, since blockade of the siderophore with gallium inhibits the rescue from ischemia. The Ngal:siderophore:Fe complex upregulates heme oxygenase-1, a protective enzyme, preserves proximal tubule N-cadherin, and inhibits cell death. Because mouse urine contains an Ngal-dependent siderophore-like activity, endogenous Ngal might also play a protective role. Indeed, Ngal is highly accumulated in the human kidney cortical tubules and in the blood and urine after nephrotoxic and ischemic injury. We reveal what we believe to be a novel pathway of iron traffic that is activated in human and mouse renal diseases, and it provides a unique method for their treatment.

Authors

Kiyoshi Mori, H. Thomas Lee, Dana Rapoport, Ian R. Drexler, Kirk Foster, Jun Yang, Kai M. Schmidt-Ott, Xia Chen, Jau Yi Li, Stacey Weiss, Jaya Mishra, Faisal H. Cheema, Glenn Markowitz, Takayoshi Suganami, Kazutomo Sawai, Masashi Mukoyama, Cheryl Kunis, Vivette D’Agati, Prasad Devarajan, Jonathan Barasch

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Figure 6

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Clearance of Ngal by the proximal tubule. (A) Fluorescent Ngal (100 μg, ...
Clearance of Ngal by the proximal tubule. (A) Fluorescent Ngal (100 μg, labeled with Alexa 568) was introduced into the peritoneum, and after 1 hour the kidney was harvested and sectioned. Fluorescent Ngal was localized to large vesicles in the proximal tubule (bottom panel) but not in the glomerulus (G) or medulla (small top panels). Uncoupled dye did not label the kidney (Alexa 568 only). (B) Alexa 568–Ngal colocalized with FITC-dextran in S1 and S2 segments of the proximal tubule. Dextran was introduced into the animal 1 day before the Ngal injection in order to label lysosomes. (C) 125I-Ngal was introduced into mice, and the samples were assayed by SDS-PAGE. Lanes were loaded with 1,000 cpm each. The lane marked “Ngal” shows the initial preparation of 125I-Ngal. Subsequent lanes of urine or blood show loss of signal, suggesting degradation to small fragments. However, full-length Ngal and a 14-kDa fragment of Ngal were found in the kidney 1 and 5 hours after injection. (D and E) Radioautograph of kidney 1 hour after i.p. injection of 55Fe-loaded Ngal:siderophore. Radioactivity was not found in the medulla (D). In contrast, radioactive decay was found in the cortex and was associated with the apical zones of proximal tubule cells (E). Original magnification, A and B, ×40; A, inset, ×10. Scale bar: D and E, 2 μm.