Cellular uptake of proMMP-2:TIMP-2 complexes by the endocytic receptor megalin/LRP-2.

Matrix metalloproteinases (MMPs) are regulated at multiple transcriptional and post-transcriptional levels, among which receptor-mediated endocytic clearance. We previously showed that low-density lipoprotein receptor-related protein-1 (LRP-1) mediates the clearance of a complex between the zymogen form of MMP-2 (proMMP-2) and tissue inhibitor of metalloproteinases, TIMP-2, in HT1080 human fibrosarcoma cells. Here we show that, in BN16 rat yolk sac cells, proMMP-2:TIMP-2 complex is endocytosed through a distinct LRP member, megalin/LRP-2. Addition of receptor-associated protein (RAP), a natural LRP antagonist, caused accumulation of endogenous proMMP-2 and TIMP-2 in conditioned media. Incubation with RAP also inhibited membrane binding and cellular uptake of exogenous iodinated proMMP-2:TIMP-2. Moreover, antibodies against megalin/LRP-2, but not against LRP-1, inhibited binding of proMMP-2:TIMP-2 to BN16 cell surface. BIAcore analysis confirmed direct interaction between the complex and megalin/LRP-2. Conditional renal invalidation of megalin/LRP-2 in mice resulted in accumulation of proMMP-2 and TIMP-2 in their urine, highlighting the physiological relevance of the binding. We conclude that megalin/LRP-2 can efficiently mediate cell-surface binding and endocytosis of proMMP-2:TIMP-2 complex. Therefore megalin/LRP-2 can be considered as a new actor in regulation of MMP-2 activity, an enzyme crucially involved in many pathological processes.

Gelatin-modified gold nanoparticles for direct detection of urinary total gelatinase activity: Diagnostic value in bladder cancer.

Matrix metalloproteinases (MMPs), in particularly gelatinases (MMP-2 and MMP-9) were reported as urinary markers of bladder cancer. In this work, we developed a simple colorimetric gold nanoparticle (AuNP) assay for rapid and sensitive detection of urinary total gelatinase activity based on the surface plasmon resonance (SPR) property of AuNPs. Gelatin-modified AuNPs were stably suspended in solution even upon addition of an aggregation inducer as 6-mercaptohexan-1-ol (6-MCH). Gelatinases digest gelatin capping. Subsequently, addition of 6-MCH leads to AuNPs aggregation with red to blue color shift. In a pilot study, results of the developed AuNP assay were consistent with zymography for qualitative detection of urinary total gelatinase activity. The sensitivity and specificity of both assays were 80% and 90.9% respectively. The absorption ratios, A625/A530 of the reacted AuNP solutions were used to quantify the total gelatinase concentration. The best cut off value was 0.01895ng/µg protein, at which the sensitivity was 87.5% and the specificity was 86.4%. The developed AuNP assay is simple, low-cost and can aid non-invasive diagnosis of bladder cancer.

In Diabetic Kidney Disease Urinary Exosomes Better Represent Kidney Specific Protein Alterations Than Whole Urine.

BACKGROUND: Predicting or diagnosing underlying kidney disease by analyzing whole urine remains the mainstay of nephrology practice. However, whole urine is a poor compartment to assess many structural changes in the kidney because whole urine contains only a few proteins derived from the kidney itself. Urinary exosomes, on the other hand, which are derived from the kidney, contain proteins secreted by the kidney. We experimentally tested the hypothesis that 'urinary exosomes more faithfully represent changes in the kidney tissue than whole urine'. A direct comparison between whole urine and urine exosomal levels of two chosen kidney disease markers, gelatinase and ceruloplasmin, was carried out on diabetic kidney disease patients. METHODS: Urinary exosomes were separated from whole urine by sequential centrifugation including ultra-centrifugation. Gelatinase activity was measured using fluorosceinated gelatin as the substrate, and ceruloplasmin was measured by sandwich ELISA. A few kidney specimens from patients biopsied for atypical features were histochemically stained for validation of the biochemical results. RESULTS: We found that changes in both, gelatinase (decreased activity) and ceruloplasmin (increased levels), in the urinary exosomes of diabetic kidney patients were in agreement with the alterations of these two proteins in the kidney tissue. In contrast, the levels of these two proteins in whole urine were highly variable and did not correlate with levels in the diabetic kidney tissue. CONCLUSION: In conclusion, these results confirmed our hypothesis that protein markers in urinary exosomes better reflected the underlying protein changes in the kidney than in whole urine samples.

Urine neutrophil gelatinase-associated lipocalin: an independent predictor of adverse outcomes in acute kidney injury.

BACKGROUND: Several recent studies have shown that neutrophil gelatinase-associated lipocalin (NGAL) may be a promising biomarker for the early detection of acute kidney injury (AKI), but the role of NGAL in predicting adverse clinical outcomes has not been well addressed. The purpose of this study was to evaluate the usefulness of urine NGAL as outcome predictor in patients with AKI. METHODS: This was a prospective cohort study enrolling hospitalized AKI patients. Patients were divided into four groups according to initial urine NGAL excretion quartiles. The primary clinical outcome variables were in-hospital mortality and renal function at 4 weeks. RESULTS: Initial urine NGAL was identified as an independent predictor of in-hospital mortality and persistent loss of renal function. In the analysis of predictive performance of urine NGAL, the AUC was 0.882 and a cutoff value of 298.28 ng/ml predicted loss of renal function with 88.2% sensitivity and 81.0% specificity. CONCLUSION: This study could suggest that urine NGAL, a new early biomarker might also be served as a reliable clinical outcome predictor in AKI patients.

Urinary neutrophil-gelatinase associated lipocalin is a potential noninvasive marker for renal scarring in patients with vesicoureteral reflux.

PURPOSE: Renal scarring is a serious complication that often occurs with chronic pyelonephritis in the presence of vesicoureteral reflux. In a previous study we established a rat model of renal scarring in which we found the up-regulation of neutrophil-gelatinase associated lipocalin at the mRNA and protein levels. In this study we evaluated urinary neutrophil-gelatinase associated lipocalin as a potential biomarker for progression of renal scarring in patients with vesicoureteral reflux. MATERIALS AND METHODS: A total of 34 patients diagnosed with vesicoureteral reflux without evidence of current urinary tract infection and 28 normal healthy children were enrolled in this study. Renal scars were evaluated by (99m)technetium dimercapto-succinic acid renal scan in 24 of the reflux cases. Urinary neutrophil-gelatinase associated lipocalin levels were monitored by ELISA. RESULTS: In normal subjects urinary neutrophil-gelatinase associated lipocalin was high during infancy, decreased rapidly within the following year and reached a low stable level from age 3 years onward. Urinary neutrophil-gelatinase associated lipocalin levels, normalized to age matched standards, were significantly increased in patients with vesicoureteral reflux compared to controls. These levels did not correlate with reflux grade, but were significantly higher in patients with radiological evidence of renal scarring irrespective of reflux grade. CONCLUSIONS: Estimation of urinary neutrophil-gelatinase associated lipocalin may be useful as a noninvasive diagnostic or prognostic biomarker for renal scarring.

Neutrophil gelatinase-associated lipocalin and cystatin C could predict renal outcome in patients undergoing kidney allograft transplantation: a prospective study.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) may represent an early, predictive biomarker of delayed graft function due to ischemia-reperfusion injury. Unfortunately, creatinine is an unreliable indicator of acute changes in kidney function. NGAL was proposed as a novel early marker for detection of acute renal failure. Therefore, the aim of the study was to assess whether NGAL and cystatin C predicted outcomes among 41 consecutive patients undergoing kidney transplantation. Serum NGAL and cystatin C were evaluated before, as well as 1, 3, 6, and 10 days after kidney transplantation using commercially available kits. Serum creatinine was assessed at each time. We observed a significant fall in serum NGAL as early as 1 day following kidney transplantation. Serum cystatin C decreased significantly 3 days after transplantation. Before transplantation, serum NGAL was related to creatinine and cystatin C. At each time point, serum NGAL was related positively to serum creatinine, cystatin C, and negatively to urine volume. In patients with delayed graft function, there was no fall in serum NGAL or cystatin C. Our findings may have important implications for the clinical management of patients undergoing kidney transplantation. The "window of opportunity" to distinguish between acute rejection and calcineurin inhibitor nephrotoxicity is narrow in delayed graft function. Time is limited to introduce proper treatment after the initiating insult. Therefore, NGAL needs to be investigated as a potential early marker for delayed graft function, especially in the settings of early dialysis treatment or antirejection therapy.

Gelatinase isoforms in urine from bladder cancer patients.

Matrix metalloproteinases are involved in tumor invasion and metastasis in many types of human carcinomas, in leukocyte infiltration and inflammatory reactions. Three metalloproteinases with gelatinolytic activity were isolated from the urine of patients with untreated high grade bladder cancer or with functioning renal grafts (control). Urinary proteins were fractionated after concentration by continuous-elution SDS-polyacrylamide gel electrophoresis. Collected fractions were analyzed by gelatin zymography and Western blotting. The one-step purification process isolated the gelatinase species from crude urine samples: (1) a 72 kDa progelatinase A (MMP-2) and its actived 68 kDa form; (2) a 92 kDa progelatinase B (MMP-9); (3) a higher molecular weight (HMW) complex (115 kDa) which was identified as progelatinase B associated with lipocalin, NGAL. A similar marker profile was observed in bladder cancer tissues. The current study demonstrated the efficiency of continuous elution electrophoresis. It offered two main advantages: (1) the separation of latent from active gelatinase isoforms with no interference from the TIMPs and (2) the identification and isolation in a single step of large amounts of urine gelatinase species with both high recovery and significant specific activities. Continuous-elution electrophoresis can be used for correlation with clinical events of bladder cancer diagnosis and prognosis.

Characterization of matrix metalloproteinases in human urine: alterations during adolescence.

Matrix metalloproteinases (MMPs) are a family of at least 14 zinc-dependent proteinases that have been implicated in matrix turnover under both normal and pathological conditions. Previous studies have shown that several MMPs are produced in various cell types in the kidney, suggesting that MMPs may be involved in renal morphogenesis and remodelling. Using a variety of techniques, including gelatin and casein zymography, gelatin affinity chromatography, immunoblotting, and immunoprecipitation, we have identified the major gelatinases in human urine as MMP-2 and MMP-9. Latent forms of both enzymes were detected in urine, as well as lower molecular mass species of each, consistent with activated forms of MMP-2 and MMP-9. MMP-2 and MMP-9 were also measured in individual human urine samples (n=40). No significant gender differences in MMP concentrations were detected. However, renal MMP expression appeared to be age dependent; the highest average amounts of urine MMP-2 were detected during adolescence, while the converse was true of urine MMP-9. Together, these findings indicate that under normal conditions, human urine contains MMP-2 and/or MMP-9, suggesting that these two MMPs are normally produced within the kidney, where they may regulate normal renal remodelling and matrix homeostasis in an age-specific manner.

Matrix metalloproteinase-2 in a murine model of infantile-type polycystic kidney disease.

It was previously found that elevated levels of matrix metalloproteinase (MMP)-2 (gelatinase A) and -9 (gelatinase B) were synthesized and secreted into the medium by cultured kidney tubules derived from cystic C57BL/6J-cpk mice. To determine whether increased synthesis and secretion occur in vivo in this mouse model of polycystic kidney disease, kidney protein extracts, mRNA, and tissue sections were compared for expression and activity of MMP-2 and -9. Although both MMP were detected in tissue extracts, the differences in expression levels and activity in normal and cystic kidneys were far greater for MMP-2. High levels of MMP-2 seemed to result from increased expression by the cystic kidneys predominantly in the second and third postnatal weeks (a time when the kidneys are undergoing rapid cystic enlargement). Much of the increased MMP was present in the inactive zymogen form, although active enzyme was readily detected by sodium dodecyl sulfate-polyacrylamide gel zymography and in situ zymography. MMP-2 was abnormally localized to the interstitium and to foci between cysts, suggesting that MMP-2 may regulate collagen accumulation at those sites, thus allowing cyst enlargement and limiting the severity of interstitial fibrosis.

Role of matrix metalloproteinase-9 in the basement membrane destruction of superficial urothelial carcinomas.

PURPOSE: This study was conducted to clarify which matrix metalloproteinases (MMPs) play a key role in destruction of the underlying basement membrane (BM) of superficial urothelial carcinomas. Urine concentrations of MMP-9 and tissue inhibitors of matrix metalloproteinase-1 (TIMP-1) were also measured. MATERIALS AND METHODS: Overexpression of MMP-1, MMP-2 and MMP-9 was analyzed immunohistochemically in 60 patients with transitional cell carcinomas of the urothelium (41 were pTa or pis, 19 were pT1-4), and compared them with type IV collagen expression in tumor BM. In 33 of them, urine concentrations of MMP-9 and TIMP-1 were measured by one-step sandwich enzyme immunoassay. RESULTS: Positive expression of MMP-1, MMP-2 and MMP-9 was found in 53%, 17%, and 65% of tumors, respectively. Only MMP-9 expression rates were increased with grades and stages (p = 0.03). In pTa and pis tumors, type IV collagen expression was reduced in 17 of 26 (65.4%), and it was associated with positive MMP-9 expression (p = 0.0283). MMP-9 was detected in all urine samples of urothelial cancer patients, while urine TIMP-1 was detectable in 18 of 33 patients. In 16 healthy volunteers, both of them were below detectable levels. Balance between urinary MMP-9 and TIMP-1 were particularly kept in superficial urothelial carcinomas with intact tumor BM. Tumor BM status, however, was not associated with urinary MMP-9 or TIMP-1 levels. CONCLUSIONS: These results suggest that MMP-9 plays a key role in the invasion step of superficial urothelial carcinomas. Detection of urinary MMP-9 may become a new, non-invasive mean for the diagnosis of urothelial carcinomas.

Increased incidence of matrix metalloproteinases in urine of cancer patients.

Matrix metalloproteinases (MMPs) have been implicated in mechanisms of metastasis in experimental cancer models and in human malignancies. In this study, we used substrate gel electrophoresis (zymography) to determine the frequency of detection of MMPs in urine of patients with a variety of cancers. Three molecular weight classes of urinary MMPs, Mr 72,000, Mr 92,000, and high molecular weight (Mr > or = 150,000) species, were detected reproducibly and correlated with disease status. The Mr 72,000 and Mr 92,000 species were identified as MMP-2 and MMP-9, respectively, by Western blot analysis. The presence of biologically active MMP-2 (P < 0.001) or MMP-9 (P = 0.002) was an independent predictor of organ-confined cancer, and the high molecular weight species (P < 0.001) was an independent predictor of metastatic cancer. This is the first study to demonstrate that analysis of urinary MMPs may be useful in determining disease status in a variety of human cancers, both within and outside of the urinary tract.

Morphine modulates 72-kDa matrix metalloproteinase.

Mesangial expansion is considered to be a precursor of glomerulosclerosis, a predominant glomerular lesion in heroin nephropathy. In addition to matrix synthesis, matrix degradation may also contribute to expansion of mesangium. In this study, we evaluated the effect of morphine on metalloproteinases (gelatinases) that degrade type IV collagen and are secreted by mesangial cells (MC). Gelatinolytic activity was significantly decreased in media of MC exposed to morphine for 1 wk compared with control [control, 2,411.6 +/- 198.7; morphine (10(-6) M), 954.4 +/- 112.2 ng.mg protein-1.3 h-1; P < 0.001]. A similar effect was seen at 2 wk [control, 17,010.6 +/- 1,789.5; morphine (10(-6) M), 8,925.2 +/- 1,623.5 ng.mg protein-1.3 h-1; P < 0.02]. Percent change in gelatinolytic activity was 39.58% (1 wk) and 47.53% (2 wk) compared with control. Morphine at concentrations of 10(-10) to 10(-6) M decreased gelatinolytic activity in MC. In in vivo studies, 24-h urines of morphine-treated rats showed a lower (P < 0.01) gelatinolytic activity when compared with controls. Isolated glomeruli from morphine-treated rats also showed decreased (P < 0.05) gelatinolytic activity compared with control. Naloxone, an opioid antagonist, did not inhibit the effect of morphine on gelatinolytic activity of MC. These results suggest that morphine may cause a decrease in degradation of type IV collagen in patients with heroin addiction. Accumulation of collagen because of lack of gelatinolytic activity in the mesangium may contribute to the expansion of mesangium.