Urinary neutrophil gelatinase-associated lipocalin predicts graft loss after acute kidney injury in kidney transplant

Molecular immune monitoring in kidney transplant rejection: a state-of-the-art review

Although current regimens of immunosuppressive drugs are effective in renal transplant recipients, long-term renal allograft outcomes remain suboptimal. For many years, the diagnosis of renal allograft rejection and of several causes of renal allograft dysfunction, such as chronic subclinical inflammation and infection, was mostly based on renal allograft biopsy, which is not only invasive but also possibly performed too late for proper management. In addition, certain allograft dysfunctions are difficult to differentiate from renal histology due to their similar pathogenesis and immune responses. As such, non-invasive assays and biomarkers may be more beneficial than conventional renal biopsy for enhancing graft survival and optimizing immunosuppressive drug regimens during long-term care. This paper discusses recent biomarker candidates, including donor-derived cell-free DNA, transcriptomics, microRNAs, exosomes (or other extracellular vesicles), urine chemokines, and nucleosomes, that show high potential for clinical use in determining the prognosis of long-term outcomes of kidney transplantation, along with their limitations.

Urinary NGAL Measured after the First Year Post Kidney Transplantation Predicts Changes in Glomerular Filtration over One-Year Follow-Up

Currently, serum creatinine and estimated glomerular filtration rate (eGFR) together with albuminuria or proteinuria are laboratory markers used in long-term monitoring of kidney transplant recipients. There is a need for more sensitive markers that could serve as early warning signs of graft dysfunction. Our aim was to assess the urinary concentrations of neutrophil gelatinase-associated lipocalin (NGAL) as a predictor of changes in kidney transplant function after the first year post-transplantation. We prospectively recruited 109 patients with functioning graft at least one year after the transplantation, with no acute conditions over the past three months, during their control visits in kidney transplant ambulatory. Urinary NGAL measured on recruitment was twice higher in patients with at least 10% decrease in eGFR over 1-year follow-up compared to those with stable or improving transplant function. Baseline NGAL significantly predicted the relative and absolute changes in eGFR and the mean eGFR during the follow-up independently of baseline eGFR and albuminuria. Moreover, baseline NGAL significantly predicted urinary tract infections during the follow-up, although the infections were not associated with decreasing eGFR. Additionally, we assessed urinary concentrations of matrix metalloproteinase 9-NGAL complex in a subgroup of 77 patients and found higher levels in patients who developed urinary tract infections during the follow-up but not in those with decreasing eGFR. High urinary NGAL in clinically stable kidney transplant recipients beyond the first year after transplantation may be interpreted as a warning and trigger the search for transient or chronic causes of graft dysfunction, or urinary tract infection.

N-acetylcysteine decreases urinary level of neutrophil gelatinase-associated lipocalin in deceased-donor renal transplant recipients: a randomized clinical trial

CONTEXT

Acute kidney injury (AKI) is a common complication after kidney transplantation (KT), especially in recipients from deceased donors. Urinary neutrophil gelatinase-associated lipocalin (u-NGAL) is an early and sensitive marker of AKI after transplantation.

OBJECTIVES

We assessed the renoprotective effect of N-acetylcysteine (NAC) on u-NGAL levels as an early prognostic marker of graft function immediately after transplantation.

MATERIALS AND METHODS

A double-blind, randomized, placebo-controlled trial was conducted on 70 deceased-donor KT recipients ( www.irct.ir , trial registration number: IRCT2014090214693N4). Patients received 600 mg oral NAC or placebo twice daily from day 0 to 5 and urine samples were taken before, and on the first and fifth days after transplantation. U-NGAL and early graft function were compared between the two groups.

RESULTS

NAC significantly reduced u-NGAL levels compared to placebo (p value = 0.02), while improvement in early graft function with NAC did not reach statistical significance.

CONCLUSIONS

This study showed that NAC administration in deceased-donor KT recipients can reduce tubular kidney injury, evidenced by u-NGAL measurements. Improvement in early graft function needs a larger sample size to reach a statistical conclusion.

The effects of environmental chemicals on renal function

The global incidence of chronic kidney disease (CKD) is increasing among individuals of all ages. Despite advances in proteomics, genomics and metabolomics, there remains a lack of safe and effective drugs to reverse or stabilize renal function in patients with glomerular or tubulointerstitial causes of CKD. Consequently, modifiable risk factors that are associated with a progressive decline in kidney function need to be identified. Numerous reports have documented the adverse effects that occur in response to graded exposure to a wide range of environmental chemicals. This Review summarizes the effects of such chemicals on four aspects of cardiorenal function: albuminuria, glomerular filtration rate, blood pressure and serum uric acid concentration. We focus on compounds that individuals are likely to be exposed to as a consequence of normal consumer activities or medical treatment, namely phthalates, bisphenol A, polyfluorinated alkyl acids, dioxins and furans, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Environmental exposure to these chemicals during everyday life could have adverse consequences on renal function and might contribute to progressive cumulative renal injury over a lifetime. Regulatory efforts should be made to limit individual exposure to environmental chemicals in an attempt to reduce the incidence of cardiorenal disease.

Neutrophil gelatinase-associated lipocalin in kidney transplantation: A review

Neutrophil gelatinase-associated lipocalin (NGAL) is a protein expressed by kidney tubular cells in response to ischemia, but may also be an early indicator of immunological rejection, calcineurin inhibitor toxicity, obstructive nephropathy, subclinical tubulitis or infection. Although there is currently no evidence to support the routine serial measurement of blood or urinary NGAL to detect subclinical acute tubular injury, NGAL has the potential to provide useful information to those that care for kidney transplant recipients (KTRs). First, high urinary or serum NGAL concentrations shortly after transplantation are a predictor of delayed graft function and are associated with reduced graft function at one year. Secondly, among KTRs with previously stable graft function who then suffer acute graft dysfunction, a high urinary NGAL predicts graft loss at one year. If further refined, diagnostic tests based on NGAL levels may provide future useful clinical tools.

Through a glass darkly: seeking clarity in preventing late kidney transplant failure

A common lament is that long-term kidney transplant outcomes remain the same despite improvements in early graft survival. To be fair, progress has been made-in both our understanding of chronic injury and modestly, graft survival. However, we are still a long way from actually solving this important and difficult problem. In this review, we outline recent data supporting the existence of several causes of renal allograft loss, the incidences of which peak at different time points after transplantation. On the basis of this broadened concept of chronic renal allograft injury, we examine the challenges of clinical trial design in long-term studies, including the use of surrogate end points and biomarkers. Finally, we suggest a path forward that, ultimately, may improve long-term renal allograft survival.