Extensive pre-clinical studies have established the biological role, plausibility, and proof of concept of neutrophil
gelatinase-associated lipocalin (NGAL) as a biomarker for acute kidney injury (AKI). In AKI, there is a rapid and
massive upregulation of NGAL in the kidney. The biological role of NGAL induction is attenuation of apoptosis and an
enhanced proliferative response, as well as defense of the urinary system from bacteria. These actions are mediated by
chelation of siderophores, removal of iron from extracellular environments and redirection to intracellular sites. In AKI,
both urine and plasma NGAL are derived largely from the damaged nephron. NGAL expression in the kidney, urine, and
plasma is directly proportional to the duration and severity of kidney injury, temporally correlated with the inciting stimulus,
and specific to intrinsic AKI. These findings have now been successfully translated to multiple human studies, and
NGAL has emerged as an excellent biomarker in the urine and plasma for early diagnosis, risk stratification, severity prediction,
differential diagnosis, and outcomes prediction in several common clinical AKI scenarios. The deployment of
standardized clinical platforms has further facilitated the validation of urine and plasma NGAL as an AKI biomarker.
Some relevant patents are also summarized in this review.