The Origin of Multiple Molecular Forms in Urine of HNL/NGAL

Abstract

Results: The major molecular form of HNL/NGAL secreted by neutrophils is dimeric, whereas the major form secreted by HK-2 cells is monomeric. This was reflected by a predominance of the monomeric form in urine from patients with AKI and the dimeric form in patients with UTIs. The epitope specificities of the antibody used in the ELISAs had a profound effect on assay performance and paralleled differences of the antibodies to identify the different forms of urine HNL/NGAL.Conclusions: The monomeric form is the predominant form secreted by tubular epithelial cells, and the dimeric form is the predominant form secreted by neutrophils. The development of molecular form-specific assays for HNL/NGAL may be a means to identify the origin of HNL/NGAL in urine and construct more specific tools for the diagnosis of AKI.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) is associated with mortality in a community-based cohort of older Swedish men

“…The lack of linear correlation between NGAL in serum and urine in this study further supports the kidney origin of u-NGAL. Further studies using an NGAL assay that discriminates between the monomeric tubular epithelium-derived and the dimeric neutrophilderived forms may clarify the origin of u-NGAL [39]. However, we find it unlikely that systemic inflammation would primarily explain the associations between u-NGAL and mortality since CRP as a covariate did not seem to confound the risk estimation models.…”

“…NGAL from circulating activated neutrophils are primarily reflected in plasma or serum but it can not be ruled out that NGAL from activated neutrophils also contributes to u-NGAL concentrations. During AKI both infiltration of neutrophils in the kidney [38] or glomerular filtration of circulating NGAL may contribute to urinary concentrations of NGAL [39]. The origin of u-NGAL in this setting of elderly but relatively healthy humans is not fully known, however we speculate that a major part of the measured u-NGAL derives from tubular endothelial cells rather than from circulating neutrophils.…”

Effects of Restoration of Blood Flow on the Development of Aortic Atherosclerosis in ApoE −/− Mice With Unilateral Renal Artery Stenosis

“…Because plasma NGAL is a powerful and independent predictor of acute kidney injury and renal repair,30, 31 the increased levels of NGAL observed after revascularization would suggest that restoration of renal blood flow leads to a prolonged renal repair process 27, 28. Additional studies are needed to define whether the changes in plasma NGAL levels were renal in origin given that NGAL exists in blood in 3 different molecular forms—as a monomer, homodimer, and heterodimer32—with activated neutrophils predominantly releasing homodimeric NGAL, whereas injured distal tubule renal epithelial cells largely secrete monomeric NGAL 33, 34…”

Neutrophil gelatinase-associated lipocalin: primary care diagnostic technology update

“…In contrast, neutrophils have been claimed to release NGAL primarily as a 45kDa homodimer, that is, two NGAL monomers linked by a disulfide bridge. 5 In good health, there are only low levels of NGAL detectable in urine. Immediately following acute kidney injury, NGAL is substantially upregulated in the distal part of the nephron leading to increased urinary and plasma NGAL levels.…”