Giuseppe Coppolino

Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Progression of Chronic Kidney Disease

BACKGROUND AND OBJECTIVES Chronic kidney disease (CKD) has recently assumed epidemic proportion, becoming a troubling emerging cause of morbidity, especially if it progresses to terminal stage (ESRD). The authors aimed to evaluate whether neutrophil gelatinase-associated lipocalin (NGAL), a novel specific biomarker of acute kidney injury, could predict the progression of CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Serum and urinary NGAL levels, together with a series of putative progression factors, were evaluated in a cohort of 96 patients (mean age: 57 +/- 16 years) affected by nonterminal CKD (eGFR > or =15 ml/min/1.73 m(2)) of various etiology. Progression of CKD, assessed as doubling of baseline serum creatinine and/or onset of ESRD, was evaluated during follow-up. RESULTS At baseline, both serum and urinary NGAL were inversely, independently, and closely related to eGFR. After a median follow-up of 18.5 mo (range 1.01 to 20), 31 patients (32%) reached the composite endpoint. At baseline, these patients were significantly older and showed increased serum creatinine, calcium-phosphate product, C-reactive protein, fibrinogen, daily proteinuria, and NGAL levels, whereas eGFR values were significantly lower. Univariate followed by multivariate Cox proportional hazard regression analysis showed that urinary NGAL and sNGAL predicted CKD progression independently of other potential confounders, including eGFR and age. CONCLUSION In patients with CKD, NGAL closely reflects the entity of renal impairment and represents a strong and independent risk marker for progression of CKD.

Neutrophil Gelatinase–Associated Lipocalin (NGAL) as a Marker of Kidney Damage

Neutrophil gelatinase-associated lipocalin (NGAL) is a protein belonging to the lipocalin superfamily initially found in activated neutrophils, in accordance with its role as an innate antibacterial factor. However, it subsequently was shown that many other types of cells, including in the kidney tubule, may produce NGAL in response to various injuries. The increase in NGAL production and release from tubular cells after harmful stimuli of various kinds may have self-defensive intent based on the activation of specific iron-dependent pathways, which in all probability also represent the mechanism through which NGAL promotes kidney growth and differentiation. NGAL levels predict the future appearance of acute kidney injury after treatments potentially detrimental to the kidney and even the acute worsening of unstable nephropathies. Furthermore, recent evidence also suggests that NGAL somehow may be involved in the pathophysiological process of chronic renal diseases, such as polycystic kidney disease and glomerulonephritis. NGAL levels clearly correlate with severity of renal impairment, probably expressing the degree of active damage underlying the chronic condition. For all these reasons, NGAL may become one of the most promising next-generation biomarkers in clinical nephrology and beyond.

Neutrophil gelatinase-associated lipocalin (NGAL) in human neoplasias: A new protein enters the scene

The small 25 kDa peptide, neutrophil gelatinase-associated lipocalin (NGAL), first known as an antibacterial factor of natural immunity, and an acute phase protein, is currently one of the most interesting and enigmatic proteins involved in the process of tumor development. The aim of the present review is to point out the main contradictory, sometimes even paradoxical, effects attributed to NGAL in human neoplasias. For instance, acting as an intracellular iron carrier and protecting MMP9 from proteolytic degradation, NGAL has a clear pro-tumoral effect, as has already been observed in different tumors (e.g. breast, stomach, oesophagus, brain) in humans. Moreover, in thyroid carcinomas, NGAL is strongly induced by NF-kB, an important factor involved both in tumor growth and in the link between chronic inflammation and neoplastic development. However, on the contrary, some studies have demonstrated that NGAL can inhibit the pro-neoplastic factor HIF-1alpha, FA-Kinase phosphorylation and also VEGF synthesis, thus suggesting that, in alternative conditions, NGAL also, paradoxically, has an anti-tumoral and anti-metastatic effect in neoplasias of, for example, the colon, ovary and pancreas. Finally, in the field of clinical oncology, attention is currently focused on the potential use of NGAL levels in making an early diagnosis, establishing a prognosis and predicting response to different treatments.

Neutrophil Gelatinase-Associated Lipocalin as an Early Biomarker of Nephropathy in Diabetic Patients

Background/Aims: Renal tubulointerstitium plays an important role in the development and progression of diabetic nephropathy. Methods: With the present study, we aimed at evaluating the levels of neutrophil gelatinase-associated lipocalin (NGAL), a tubular stress protein, in serum (sNGAL) and urine (uNGAL) from a cohort of 56 patients with type 2 diabetes mellitus categorized into three groups (normoalbuminuria, microalbuminuria and diabetic nephropathy). Results: All groups showed increased NGAL values with respect to controls; interestingly, increased NGAL levels were already found in diabetic patients without early signs of glomerular damage (normoalbuminuric). Both sNGAL and uNGAL increased in parallel with the severity of renal disease, reaching higher levels in patients with manifest diabetic nephropathy. The assessment of Pearson coefficient evidenced significant relationships between sNGAL and, respectively, uNGAL, serum creatinine and GFR (inversely) and between uNGAL and, respectively, serum creatinine, proteinuria, albuminuria, serum albumin and GFR (both inversely). Conclusions: NGAL might play an important role in the pathophysiology of renal adaptation to diabetes, probably as a defensive mechanism aiming to mitigate tubular suffering. Furthermore, NGAL measurement might become a useful and noninvasive tool for the evaluation of renal involvement in diabetic patients as well as for the early diagnosis of incipient nephropathy.

Neutrophil Gelatinase-Associated Lipocalin in Patients with Autosomal-Dominant Polycystic Kidney Disease

It is known that many tubular proteins are involved in the pathogenesis of autosomal-dominant polycystic kidney disease (ADPKD), which causes 8–10% of the cases of end-stage renal disease (ESRD) worldwide. Neutrophil gelatinase-associated lipocalin (NGAL) is a protein expressed on tubular cells of which the production is markedly increased in response to harmful stimuli such as ischemia or toxicity. In the present study, serum and urinary NGAL levels were evaluated in 26 ADPKD subjects. Both levels were significantly higher in patients than in controls (sNGAL 174 ± 52 vs. 50 ± 27 ng/ml, p < 0.05; uNGAL 119 ± 42 vs. 7 ± 6 ng/ml, p < 0.005) and a close correlation was also found between these parameters and the residual renal function (sNGAL/GFR: r = –0.8, p = 0.006; sNGAL/Creatinine: r = 0.9, p = 0.007; uNGAL/GFR: r = –0.49, p < 0.05; uNGAL/Creatinine: r = 0.84, p < 0.001). Patients were further divided into two groups according to the cystic development assessed with echotomography; subjects with higher cystic growth (HCG) presented higher sNGAL and uNGAL levels with respect to others (sNGAL: 242 ± 89 vs. 88 ± 34 ng/ml, p < 0.05; uNGAL: 158 ± 45 vs. 73 ± 27 ng/ml, p < 0.05). The strict correlation between NGAL levels and residual renal function is perfectly in accord with recent studies on patients with other ESRD-associated diseases. We can hypothesize that tubular cells produce big quantities of NGAL as a consequence of increased apoptosis following chronic damage or as a compensatory response, similar to that observed in acute stress conditions (ischemia, toxicity ...). Finally, our last finding that patients with HCG showed higher levels of NGAL suggests that this protein could be also involved in the cyst growth process, as previously reported about epithelial and tumoral expansion.

Increased Plasma Neutrophil Gelatinase-Associated Lipocalin Levels Predict Mortality in Elderly Patients with Chronic Heart Failure

Chronic congestive heart failure (CHF) is associated with an increase in cytokines and inflammatory markers, particularly in elderly patients in whom chronic inflammation is generally present per se. In the present pilot study, neutrophil gelatinase-associated lipocalin (NGAL), a recently discovered cytokine, was analyzed together with different clinical and laboratory parameters in a small cohort of 46 elderly patients with CHF of various degrees. NGAL levels in the cohort were found to be significantly higher than in healthy age-balanced controls (458.5 [62.5-1212.4] vs. 37.8 [15.9-46.5] ng/mL; p = 0.0001). Furthermore, NGAL values increased in parallel with the clinical severity of CHF (New York Heart Association [NYHA] classification), the highest levels being reached in class IV patients (p = 0.0001). After a 2-year follow up, Kaplan-Meier curves indicated that patients with baseline NGAL > 783 ng/mL (best receiver operating characteristic [ROC]-derived cut-off value) had a significantly higher mortality (p = 0.001; log-rank test) and 4.08 hazards ratio (95% confidence interval [CI], 1.29-12.96) for death than the other subjects considered. Although preliminary, our findings suggest that NGAL plays a pivotal role in the systemic adaptation to chronic heart failure in elderly patients. Moreover, they indicate, for the first time, that measurement of NGAL may be of important prognostic value in the assessment of survival, thus extending the predictive properties of this cytokine beyond the clinical field of renal disease.

Neutrophil Gelatinase-Associated Lipocalin Reflects the Severity of Renal Impairment in Subjects Affected by Chronic Kidney Disease

Neutrophil gelatinase-associated lipocalin (NGAL) is a small 25-kDa protein released from kidney tubular cells after harmful stimuli. It represents one of the most promising future biomarkers in the diagnostic field of acute kidney injury (AKI), as the increase in NGAL levels is a good predictor of a brief-term onset of AKI, notably anticipating the resulting increase in serum creatinine. However, recent studies also suggest a possible role for NGAL in chronic kidney disease (CKD). For this reason we evaluated serum (sNGAL) and urinary NGAL (uNGAL) in a cohort of CKD patients in order to verify the relationship with the severity of renal impairment. In CKD patients sNGAL, uNGAL and the fractional excretion of this protein were notably increased as compared to controls. Furthermore both sNGAL and uNGAL were correlated with serum creatinine and, inversely, with residual glomerular filtration rate (GFR): this last relationship was found to be even closer than that found between GFR and serum creatinine. Multivariate models validate these correlations as independent, confirming that in these patients NGAL is a better predictor of GFR than serum creatinine. The results confirm NGAL as an important biomarker in clinical nephrology, extending to CKD the pathophysiological role of this protein in tubular adaptations to renal damage.

From kidney to cardiovascular diseases: NGAL as a biomarker beyond the confines of nephrology.

Eur J Clin Invest 2010; 40 (3): 273–276

Pathological and Prognostic Value of Urinary Neutrophil Gelatinase-Associated Lipocalin in Macroproteinuric Patients with Worsening Renal Function

Background/Aims: Persistent proteinuria is a sign of renal damage caused by several factors, but it is itself a cause of tubular injury leading to chronic renal failure. Neutrophil gelatinase-associated lipocalin (NGAL) is a stress protein released by tubular cells which urinary excretion (uNGAL) increases in response to various stimuli. Methods: In the present study we analyzed uNGAL levels in 23 macroproteinuric patients with membranous glomerulonephritis. Results: In these subjects, uNGAL concentrations were significantly higher than in controls, directly correlated with proteinuria and inversely related to residual renal function. Patients were further categorized into two groups, according to a cut-off baseline uNGAL value of 350 ng/ml and evaluated during a 1-year follow-up period. After 12 months, subjects with higher uNGAL levels showed a significant worsening in baseline renal function and a 3.36 risk ratio of developing a severe decrease in GFR (≧50% of baseline values) compared with others. Conclusions: These findings suggest that NGAL may play a key role in tubular adaptations to persistent macroproteinuria. Furthermore, a new, interesting application of NGAL measurement could be proposed in clinical nephrology as a predictor of worsening renal function in patients affected by chronic kidney disease.

Deletion of the Activated Protein-1 Transcription Factor JunD Induces Oxidative Stress and Accelerates Age-Related Endothelial Dysfunction

Background— Reactive oxygen species are major determinants of vascular aging. JunD, a member of the activated protein-1 family of transcription factors, is emerging as a major gatekeeper against oxidative stress. However, its contribution to reactive oxygen species homeostasis in the vasculature remains unknown. Methods and Results— Endothelium-dependent vasorelaxation was impaired in young and old JunD−/− mice (6 and 22 months old) compared with age-matched wild-type mice. JunD−/− mice displayed an age-independent decline in endothelial nitric oxide release and endothelial nitric oxide synthase activity and increased mitochondrial superoxide formation and peroxynitrite levels. Furthermore, vascular expression and activity of the free radical scavengers manganese and extracellular superoxide dismutase and aldehyde dehydrogenase 2 were reduced, whereas the NADPH oxidase subunits p47phox, Nox2, and Nox4 were upregulated. These redox changes were associated with premature vascular aging, as shown by reduced telomerase activity, increased &bgr;-galactosidase–positive cells, upregulation of the senescence markers p16INK4a and p53, and mitochondrial disruption. Interestingly, old wild-type mice showed a reduction in JunD expression and transcriptional activity resulting from promoter hypermethylation and binding with tumor suppressor menin, respectively. In contrast, JunD overexpression blunted age-induced endothelial dysfunction. In human endothelial cells, JunD knockdown exerted a similar impairment of the O2−/nitric oxide balance that was prevented by concomitant NADPH inhibition. In parallel, JunD expression was reduced in monocytes from old versus young healthy subjects and correlated with mRNA levels of scavenging and oxidant enzymes. Conclusions— JunD provides protection in aging-induced endothelial dysfunction and may represent a novel target to prevent reactive oxygen species–driven vascular aging.