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Netrin-1 and kidney injury. I. Netrin-1 protects against ischemia-reperfusion injury of the kidney

Division of Nephrology, The Pennsylvania State University, College of Medicine, Hershey, Pennsylvania

Submitted 29 October 2007 ; accepted in final form 17 January 2008

Endogenous mechanisms exist to limit inflammation. One such molecule is netrin. This study examined the impact of ischemia-reperfusion (I/R) on netrin expression and the role of netrin in preventing renal inflammation and injury. All three isoforms of netrin (1, 3, and 4) are expressed in normal kidney. I/R significantly downregulated netrin-1 and -4 mRNA expression, whereas expression of netrin-3 was moderately upregulated at 24 h of reperfusion. The netrin receptor UNC5B mRNA increased at 3 h and but decreased at later time points. Expression of a second netrin receptor, DCC, was not altered significantly. I/R was associated with dramatic changes in netrin-1 protein abundance and localization. Netrin-1 protein levels increased between 3 and 24 h after reperfusion. Immunolocalization showed an interstitial distribution of netrin-1 in sham-operated kidneys which colocalized with Von Willebrand Factor suggesting the presence of netrin-1 in peritubular capillaries. After I/R, interstitial netrin-1 expression decreased and netrin-1 appeared in tubular epithelial cells. By 72 h after reperfusion, netrin-1 reappeared in the interstitium while tubular epithelial staining decreased significantly. Downregulation of netrin-1 in the interstitium corresponded with increased MCP-1 and IL-6 expression and infiltration of leukocytes into the reperfused kidney. Administration of recombinant netrin-1 significantly improved kidney function (blood urea nitrogen: 161 ± 7 vs. 104 ± 24 mg/dl, creatinine: 1.3 ± 0.07 vs. 0.75 ± 0.16 mg/dl, P < 0.05 at 24 h) and reduced tubular damage and leukocyte infiltration in the outer medulla. These results suggest that downregulation of netrin-1 in vascular endothelial cells may promote endothelial cell activation and infiltration of leukocytes into the kidney thereby enhancing tubular injury.

netrin-4; inflammation; endothelial cell; chemokine

This article has been cited by other articles:

				W. Brian Reeves, O. Kwon, and G. Ramesh Netrin-1 and kidney injury. II. Netrin-1 is an early biomarker of acute kidney injury Am J Physiol Renal Physiol, April 1, 2008; 294(4): F731 - F738. [Abstract] [Full Text] [PDF]