Quantitative distribution of lysosomal hydrolases in the rat nephron

Impact of Dapagliflozin on the Renal Function and Damage in Patients with Heart Failure with a Reduced Ejection Fraction

Objective Whether or not the initial dip in the glomerular filtration rate (GFR) after the initiation of sodium-glucose co-transporter 2 inhibitors (SGLT2is) is associated with renal tubular injury in patients with heart failure with a reduced ejection fraction (HFrEF) is unclear. We therefore investigated the relationship between changes in the estimated GFR (eGFR) and urine N-acetyl-β-D-glucosaminidase (uNAG) after the initiation of dapagliflozin in patients with HFrEF. Methods We prospectively investigated 89 patients with HFrEF who were newly started on dapagliflozin 10 mg/day. Changes in the eGFR and uNAG-to-creatinine ratio (uNAG/Cre) were evaluated at 2 weeks and 2 months after the initiation of dapagliflozin. Results The eGFR was decreased at 2 weeks but had not declined further by 2 months. The uNAG/Cre was increased at 2 weeks but had not increased further by 2 months. There was no correlation between the changes in the eGFR and uNAG/Cre (r=-0.022, p=0.853 at 2 weeks and r=0.078, p=0.538 at 2 months). The relative change in the systolic blood pressure, hematocrit, plasma volume, and N-terminal pro-brain natriuretic peptide (NT-proBNP) were correlated with the relative change in the eGFR. In a multiple linear regression analysis, the relative change in the eGFR at 2 weeks was significantly associated with NT-proBNP, and the relative change in the uNAG/Cre was significantly associated with the use of loop diuretics and the relative change in urine osmolality at 2 weeks. Conclusion A transient decrease in the eGFR after the initiation of dapagliflozin in patients with HFrEF was not generally associated with renal tubular injury and might have been the result of hemodynamic alteration.

The Protective Role of Ozone Therapy in Kidney Disease: A Review

Ozone (O3) is a reactive oxygen species (ROS) that can interact with cellular components and cause oxidative stress. Following said logic, if O3 induces such a stressful milieu, how does it exert antioxidant functions? This is mediated by controlled toxicity produced by low concentrations of O3, which enhance the cell’s suppliance of antioxidant properties without causing any further damage. Therapeutic concentrations vary extensively, although 50 µg/mL is commonly used in experimental and clinical procedures, given that augmented concentrations might work as germicides or cause endogenous damage. O3 therapy has been shown to be effective when applied before or after traumatic renal procedures, whether caused by ischemia, xenobiotics, chronic damage, or other models. In this review, we focus on discussing the role of O3 therapy in different models of kidney damage associated with fibrosis, apoptosis, oxidative stress, and inflammation. We integrate and report knowledge about O3 in renal therapy, debunking skepticism towards unconventional medicine, explaining its proven therapeutic properties, and thus providing background for its use in further research as well as in clinical settings.

Comprehensive analysis of gene expression and DNA methylation for preeclampsia progression

BACKGROUND

The purpose of our study is to identify novel preeclampsia (PE)-related methylation genes and uncover the molecular mechanism of PE.

METHODS

All the datasets of gene expression and DNA methylation datasets for PE and normal samples were obtained from the Gene Expression Omnibus database. We first identified the differentially expressed genes (DEGs) and differential methylation genes (DMGs) between PE and normal samples followed by the functional enrichment analysis. Comprehensive analysis of DEGs and DMGs was also conducted for the identification of valuable PE-related biomarkers. The methylation validation was also performed with MassARRAY.

RESULTS

Three DNA methylation and three gene expression datasets were incorporated. We obtained 1754 DEGs and 99 DMGs in PE samples with the thresholds of p value <0.05, |Δbeta| > 0.1, and p value <0.05, respectively. Functional analysis of DEGs obtained cell adhesion molecules and leukocyte transendothelial migration. Besides, several valuable biomarkers of PE, including OCA2, CDK2AP1, and ADAM12, were identified through the integrated analysis of gene expression and DNA methylation datasets. Four methylation sites (cg03449867, cg09084244, cg09247979, and cg24194674) were validated, among which cg03449867 and cg09084244 were found to be hypermethylated and the related genes of OCA2 and CDK2AP1 were downregulated in PE compared with normal samples simultaneously. cg24194674 was hypomethylated and its correlated gene ADAM12 was upregulated in PE compared with normal samples simultaneously.

CONCLUSION

Our study should be helpful for the development of potential biomarkers and therapeutic targets for PE.

Clinical prospects of biomarkers for the early detection and/or prediction of organ injury associated with pharmacotherapy

Several biomarkers are used to monitor organ damage caused by drug toxicity. Traditional markers of kidney function, such as serum creatinine and blood urea nitrogen are commonly used to estimate glomerular filtration rate. However, these markers have several limitations including poor specificity and sensitivity. A number of serum and urine biomarkers have recently been described to detect kidney damage caused by drugs such as cisplatin, gentamicin, vancomycin, and tacrolimus. Neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid-binding protein (L-FABP), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein-1 (MCP-1), and cystatin C have been identified as biomarkers for early kidney damage. Hy's Law is widely used as to predict a high risk of severe drug-induced liver injury caused by drugs such as acetaminophen. Recent reports have indicated that glutamate dehydrogenase (GLDH), high-mobility group box 1 (HMGB-1), Keratin-18 (k18), MicroRNA-122 and ornithine carbamoyltransferase (OCT) are more sensitive markers of hepatotoxicity compared to the traditional markers including the blood levels of amiotransferases and total bilirubin. Additionally, the rapid development of proteomic technologies in biofluids and tissue provides a new multi-marker panel, leading to the discovery of more sensitive biomarkers. In this review, an update topics of biomarkers for the detection of kidney or liver injury associated with pharmacotherapy.

Kidney Injury Biomarkers in an Academic Hospital Setting: Where Are We Now?

Acute kidney injury (AKI) is a frequent complication in hospitalised patients and is diagnosed by urinary output and serum creatinine. Serum creatinine is an indirect marker for renal glomerular filtration, but lacks specificity for damage to kidney tissue and the relatively late response to injury precludes early recognition of AKI. Timely diagnosis of kidney injury using biomarkers that provide information about the aetiology of kidney injury is an unmet clinical need. To overcome the suboptimal performance of serum creatinine, injury biomarkers have been proposed that predict AKI in diverse clinical settings. The clinical performance of these markers is considered moderate due to the lack of specificity for kidney tissue or the underlying injury mechanisms, poor test specificity and confounding by interventions or comorbidities. Hence, it is not unequivocally beneficial to implement current kidney injury biomarkers in the clinical laboratory for diagnostic purposes. In this article we review biomarkers that might fulfil AKI-related unmet clinical needs in the academic hospital setting.

Urinary protein biomarkers of kidney injury in patients receiving cisplatin chemotherapy

Despite recent progress in the development of novel approaches to treat cancer, traditional antineoplastic drugs, such as cisplatin, remain a mainstay of regimens targeting solid tumors. Use of cisplatin is limited by acute kidney injury, which occurs in approximately 30% of patients. Current clinical measures, such as serum creatinine and estimated glomerular filtration rate, are inadequate in their ability to detect acute kidney injury, particularly when there is only a moderate degree of injury. Thus, there is an urgent need for improved diagnostic biomarkers to predict nephrotoxicity. There is also interest by the U.S. Food and Drug Administration to validate and implement new biomarkers to identify clinical and subclinical acute kidney injury in patients during the drug approval process. This minireview provides an overview of the current literature regarding the utility of urinary proteins (albumin, beta-2-microglobulin, N-acetyl-D-glucosaminidase, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, and cystatin C) as biomarkers for cisplatin-induced AKI. Many of the well-studied urinary proteins (KIM-1, NGAL, B2M, albumin) as well as emerging biomarkers (calbindin, monocyte chemotactic protein-1, and trefoil factor 3) display distinct patterns of time-dependent excretion after cisplatin administration. Implementation of these biomarker proteins in the oncology clinic has been hampered by a lack of validation studies. To address these issues, large head-to-head studies are needed to fully characterize time-dependent responses and establish accurate cutoff values and ranges, particularly in cancer patients. Impact statement There is growing interest in using urinary protein biomarkers to detect acute kidney injury in oncology patients prescribed the nephrotoxic anticancer drug cisplatin. We aim to synthesize and organize the existing literature on biomarkers examined clinically in patients receiving cisplatin-containing chemotherapy regimens. This minireview highlights several proteins (kidney injury molecule-1, beta-2-microglobulin, neutrophil gelatinase-associated lipocalin, calbindin, monocyte chemotactic protein-1, trefoil factor 3) with the greatest promise for detecting cisplatin-induced acute kidney injury in humans. A comprehensive review of the existing literature may aid in the design of larger studies needed to implement the clinical use of these urinary proteins as biomarkers of kidney injury.

Association between pulse wave velocity and a marker of renal tubular damage (N-acetyl-β-D-glucosaminidase) in patients without diabetes

The authors assessed the association between the ratio of urinary activity of N-acetyl-β-D-glucosaminidase (NAG) to creatinine and the brachial-ankle pulse wave velocity (baPWV) in patients without overt diabetes mellitus (DM). This was a cross-sectional study of 233 patients who had an estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m(2) and no history of kidney disease. Patients were divided into two groups: high NAG group (>5.8 U/g creatinine) and low NAG group (≤5.8 U/g creatinine). Mean baPWVs of the high NAG group were significantly higher than those of the low NAG group in both the eGFR ≥30 and <60 tertiles and the eGFR ≥60 and <90 tertiles. The baPWV was positively correlated with NAG in all patients (r=0.341, P<.001). Stepwise multivariate regression analysis showed that the baPWV was significantly related with NAG, age, and systolic blood pressure. Elevated NAG is related to elevated arterial stiffness in patients without DM.

Uriniferous tubule: structural and functional organization

The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.

Kidney and liver biomarkers in female dry-cleaning workers exposed to perchloroethylene

Blood and urine perchloroethylene and urine trichloroacetic acid, as markers of exposure, and serum AST, ALT, GGT and creatinine, urine total solutes and proteins, angiotensin converting enzyme, N-acetyl-ß-D-glucosaminidase and glutamine synthetase, as markers of effect, were measured in 40 dry-cleaning and 45 ironing-shop female workers. Average perchloroethylene air level in the dry-cleaning shops was 59.7 mg m(-3), i.e. three-fold lower than the current A.C.G.I.H. TLV-TWA (170 mg (m-3)). No statistically significant difference in the mean values of any of the effect markers was observed between the two groups, except for AST which was significantly higher in drycleaners. In addition, a statistically significant correlation was observed in dry-cleaners between environmental perchloroethylene and total urinary solutes (r = 0.308, p &lt; 0.05) or urine glutamine synthetase (r= 0.469, p &lt; 0 .01), between glutamine synthetase and blood perchloroethylene in post-shift (r= 0.406, p &lt; 0.01) or urinary perchloroethylene in post(r= 0.571, p &lt; 0.001) or pre-shift (r= 0.586, p &lt; 0.001), and between urinary perchloroethylene in pre-shift and GGT (r= 0.407, p &lt; 0.05). Interestingly, some statistically significant correlations between exposure and effect indices were found in ironing-shop workers alone, as in all subjects. Finally, transaminases, GGT and total urinary proteins were influenced by age and alcohol consumption which were significantly higher in dry-cleaners, thus providing an explanation for some of the correlations observed. In conclusion, our results show a dose-related increase of glutamine synthetase activity,a marker of damage of the pars recta of the kidney proximal tubule, in the urine of female subjects exposed to perchloroethylene concentrations in the work environment lower than current A.C.G.I.H. TLV-TWA.

Urinary N-acetyl-β-D-glucosaminidase levels are positively correlated with 2-hr plasma glucose levels during oral glucose tolerance testing in prediabetes

BACKGROUND

Urinary N-acetyl-β-D-glucosaminidase (NAG) excretion is increased in patients with impaired glucose tolerance (IGT). This study investigated when during the oral glucose tolerance test (OGTT) the plasma glucose, urine glucose, and insulin levels correlate most strongly with urinary N-acetyl-β-d-glucosaminidase (NAG) levels in prediabetic subjects.

METHODS

The OGTT was administered to 80 subjects who had not yet received a diagnosis of diabetes mellitus (DM) and in whom HbA1c levels were ≤6.8% and fasting plasma glucose levels were <7.0 mmol/l. Forty-two subjects had normal glucose tolerance (NGT), 31 had impaired glucose tolerance (IGT), and 7 had DM according to World Health Organization criteria. Serum levels of cystatin C, the estimated glomerular filtration rate, the urinary albumin-to-creatinine (Cr) ratio, urinary and serum β2-microglobulin, and urinary NAG were measured as markers of renal function.

RESULTS

NAG levels were significantly higher in subjects with DM and in subjects with IGT than in subjects with NGT. No significant associations were observed between glycemic status and other markers of renal function. Multiple linear regression analysis showed that the NAG level was positively correlated with plasma glucose levels at 120 min of the OGTT and was associated with the glycemic status of prediabetic patients.

CONCLUSION

These results suggest that postprandial hyperglycemia is an independent factor that causes renal tubular damage in prediabetes patients.

Urinary N-acetyl-beta-D glucosaminidase (NAG) level in idiopathic nephrotic syndrome

Urinary N-acetyl-beta-D: glucosaminidase (NAG) is a sensitive biomarker of renal parenchymal disease. The aim of this study was to investigate variations in the levels of NAG excretion among different sub-groups of nephrotic syndrome (first episode, relapsers, and resistant) and its prediction based on proteinuria. Thirty-five patients with idiopathic nephrotic syndrome, aged 1-12 years, as well as 15 age- and gender-matched normal children (controls) were enrolled in the study. Among the 35 patients, ten were classified with first episode nephrotic syndrome (FENS), 17 with relapsing nephrotic syndrome (RNS), and eight with steroid-resistant nephrotic syndrome (SRNS). Urinary NAG/creatinine levels were significantly increased in SRNS patients as compared to FENS and RNS patients (p < 0.001); the FENS and RNS groups had comparable levels. A urinary NAG/creatinine value of ≤108.9 U/g was found to identify steroid-sensitive patients with a sensitivity, specificity, positive predictive value, and negative predictive value of 78.8, 100, 100 and 77.7%, respectively. Significant correlations were found between experimental and predicted values of urinary NAG/creatinine in steroid sensitive nephrotic syndrome (SSNS) (R (2) = 0.9643) and SRNS patients (R (2) = 0.9823). Urinary NAG/creatinine values were found to be higher in SRNS than SSNS patients and have moderate predictive value for steroid responsiveness. This level can be obtained based on urinary protein/creatinine ratio or 24 h urinary protein levels.

Biomarkers of Collecting Duct Injury in Han-Wistar and Sprague-Dawley Rats Treated with N-Phenylanthranilic Acid

N-phenylanthranilic acid is a chloride channel blocker that causes renal papillary necrosis in rats. Studies were conducted in two strains of male rats to evaluate novel biomarkers of nephrotoxicity. Han-Wistar rats were given daily oral doses of 50, 350, or up to 700 mg/kg/day of NPAA, and Sprague-Dawley rats were given 50 or 400 mg/kg/day of NPAA. Rats were euthanized on days 8 and 15. The candidate kidney injury biomarkers renal papillary antigen-1 (RPA-1, for collecting duct injury), clusterin (for general kidney injury), α-glutathione-S-transferase (a proximal tubular marker), and µ-glutathione-S-transferase (a distal tubular marker) were measured in urine by enzyme immunoassay. Characteristic degeneration and necrosis of the collecting duct and renal papilla were observed in Han-Wistar rats at the high dose on day 8 and at the mid and high doses on day 15, and in Sprague-Dawley rats given the high dose on days 8 and 15. Increases in urinary RPA-1, and to a lesser extent urine clusterin, were generally associated with the presence of collecting duct injury and were more sensitive than BUN and serum creatinine. On the other hand, decreases in α-glutathione-S-transferase without proximal tubule lesions in both strains and decreases in µ-glutathione-S-transferase in Sprague-Dawley rats only were not associated with morphological proximal or distal tubule abnormalities, so both were of less utility. It was concluded that RPA-1 is a new biomarker with utility in the detection of collecting duct injury in papillary necrosis in male rats.

Distribution, elimination, and renal effects of single oral doses of europium in rats

Single doses of europium (III) chloride hexahydrate were orally administered to several groups of rats. Cumulative urine samples were taken at 0-24 h, and blood samples were drawn after 24-h administration. The europium concentration was determined in these samples by inductively coupled plasma atomic emission spectroscopy. The volume, creatinine, ß-2-microglobulin, and N-acetyl-ß-D-glucosaminidase were measured in the urine samples to evaluate possible europium-induced renal effects. The blood samples showed low europium distribution, with an average of 77.5 μg/L for all groups. Although the urinary concentration and excretion showed dose-dependent increases, the percentage of europium excreted showed a dose-dependent decrease, with an average of 0.31% in all groups. The administration of europium resulted in a significant decrease of creatinine and a significant increase of urinary volume, N-acetyl-ß-D-glucosaminidase, and ß-2-microglobulin. Rare earth elements, including europium, are believed to form colloidal conjugates that deposit in the reticuloendothelial system and glomeruli. This specific reaction may contribute to low europium bioavailability and renal function disturbances. Despite low bioavailability, the high performance of the analytical method for determination of europium makes the blood and urine sampling suitable tools for monitoring of exposure to this element. The results presented in this study will be of great importance in future studies on the health impacts of rare earth elements.

Application of Dolichos biflorus in immunoassay detection of kidney collecting duct biomarkers

Currently there are no biomarkers for detecting collecting duct damage in man. Antibodies to several collecting duct-specific antigens exist but sandwich assays have been difficult to establish due to the need for two different antibodies to the same protein. We hypothesized that a collecting duct-specific lectin could be used in combination with a collecting duct-specific antibody to negate the need for two different antibodies. The collecting duct specificity of selected antibodies (NiCa II 13C2, Pap XI 3C7, HuPaP VII 2B11 and aquaporin 2), was verified by immunohistochemistry. Aquaporin 2 and Pap XI 3C7 were used successfully in setting up assays with the lectin Dolichos biflorus, using the Meso Scale Discovery (MSD) platform. Antigen expression was highest in the papillae of rat and human kidney (corresponding to the greatest density of collecting ducts) and was also present in normal urine. We propose that further qualification and validation would lead to an assay for detecting collecting duct damage in man.

Evaluation of aging influence on renal toxicity caused by segment-specific nephrotoxicants of the proximal tubule in rat

Little is known concerning the sensitivity of aged rats to xenobiotics inducing kidney damage. To increase this knowledge, the age-dependent response of the kidney to hexachloro-1 : 3-butadiene (HCBD) or potassium dichromate (chromate) was investigated. Rats were treated at different ages with a single dose of segment-specific nephrotoxicants of the proximal tubule, chosen on the basis of their specificity for S(3) and for S(1)-S(2) segments, respectively. The toxicological impact of these xenobiotics has been evaluated through biochemical and genomic markers, and histopathological investigation of kidney samples. HCBD treatment induced tubular necrosis of the S(3) segment of the proximal tubule associated with changes of toxicological markers unrelated to the age. In contrast, chromate treatment induced an increased kidney damage related to the rat age. In fact, histopathological investigation revealed that at 1 month of age tubular vacuolar degeneration was seen affecting S(1)-S(2) segments of the proximal tubule, whereas at 3 months of age tubular necrosis occurred in the same segments associated with tubular dilation of the distal portions. Consistently, biochemical analysis confirmed a direct correlation among genomic and biochemical marker variability and animal age. Altogether, the results show that during aging there is an increased sensitivity of kidney to chromate but not to HCBD-induced damage and evidence differential age-related selectivity of rats for nephrotoxic compounds. Significance for human risk assessment is discussed.

Coordinated induction of Nrf2 target genes protects against iron nitrilotriacetate (FeNTA)-induced nephrotoxicity

The iron chelate, ferric nitrilotriacetate (FeNTA), induces acute proximal tubular necrosis as a consequence of lipid peroxidation and oxidative tissue damage. Chronic exposure of FeNTA leads to a high incidence of renal adenocarcinomas in rodents. NF-E2-related factor 2 (Nrf2) is a transcription factor that is activated by oxidative stress and electrophiles, and regulates the basal and inducible expression of numerous detoxifying and antioxidant genes. To determine the roles of Nrf2 in regulating renal gene expression and protecting against oxidative stress-induced kidney damage, wild-type and Nrf2-null mice were administered FeNTA. Renal Nrf2 protein translocated to the nucleus at 6h after FeNTA treatment. FeNTA increased mRNA levels of Nrf2 target genes, including NQO1, GCLC, GSTpi1/2, Mrp1, 2, and 4 in kidneys from wild-type mice, but not Nrf2-null mice. Protein expression of NQO1, a prototypical Nrf2 target gene, was increased in wild-type mice, with no change in Nrf2-null mice. FeNTA produced more nephrotoxicity in Nrf2-null mice than wild-type mice as indicated by higher serum urea nitrogen and creatinine levels, as more urinary NAG, stronger 4-hydroxynonenal protein adduct staining, and more extensive proximal tubule damage. Furthermore, pretreatment with CDDO-Im, a potent small molecule Nrf2 activator, protected mice against FeNTA-induced renal toxicity. Collectively, these results suggest that activation of Nrf2 protects mouse kidneys from FeNTA-induced oxidative stress damage by coordinately up-regulating the expression of cytoprotective genes.

Angiotensin II receptor blocker inhibits tumour necrosis factor-alpha-induced cell damage in human renal proximal tubular epithelial cells

AIM

We investigated the effect of angiotensin II (AII) type 1 (AT1) and angiotensin II type 2 (AT2) receptor blockers on tumour necrosis factor alpha (TNF-alpha)-induced cell damage in human renal proximal tubular epithelial cells (RPTEC).

METHODS

The lactate dehydrogenase (LDH) and N-acetyl-beta-glucosaminidase (NAG) release into the medium after TNF-alpha treatment in RPTEC were determined using modified commercial procedures. In addition, the levels of caspase 3/7 activity in RPTEC were measured after TNF-alpha treatment with AlphaTau1 or AT2 receptor blockers. Finally we investigated the change of p22phox protein levels after TNF-alpha with AlphaTau1 or AT2 receptor blockers in RPTEC.

RESULTS

Tumour necrosis factor alpha (10(-8) mol/L) significantly increased LDH and NAG release into the medium from RPTEC. AlphaTau1 receptor blockers, olmesartan and valsartan (10(-9)-10(-6) mol/L) showed a significant reduction on TNF-alpha-induced LDH and NAG release in RPTEC. AT2 receptor blocker, PD123319 (10(-7)-10(-5) mol/L) also decreased TNF-alpha-induced LDH and NAG release in RPTEC. Blockade of both AlphaTau1 and AT2 receptor indicated additional reduction on TNF-alpha-induced LDH and NAG release. TNF-alpha (10(-8) mol/L) treatment showed small but significant increases of caspase 3/7 activity in RPTEC, and AT1 and AT2 receptor blockers (10(-8) mol/L) comparably decreased TNF-alpha-induced caspase 3/7 activity. Significant increases of p22phox protein levels were observed in TNF-alpha-treated group in RPTEC. However, only AlphaTau1 (10(-8) mol/L) but not AT2 (10(-5) mol/L) receptor blocker significantly decreased TNF-alpha-induced p22phox protein levels.

CONCLUSION

The present study demonstrates that TNF-alpha induces renal tubular cell damage in RPTEC and AT1/AT2 receptor blockers showed cytoprotective effects probably via at least partly different mechanism.

Intracrystalline urinary proteins facilitate degradation and dissolution of calcium oxalate crystals in cultured renal cells

We have previously proposed that intracrystalline proteins would increase intracellular proteolytic disruption and dissolution of calcium oxalate (CaOx) crystals. Chauvet MC, Ryall RL. J Struct Biol 151: 12-17, 2005; Fleming DE, van Riessen A, Chauvet MC, Grover PK, Hunter B, van Bronswijk W, Ryall RL. J Bone Miner Res 18: 1282-1291, 2003; Ryall RL, Fleming DE, Doyle IR, Evans NA, Dean CJ, Marshall VR. J Struct Biol 134: 5-14, 2001. The aim of this investigation was to determine the effect of increasing concentrations of intracrystalline protein on the rate of CaOx crystal dissolution in Madin-Darby canine kidney (MDCKII) cells. Crystal matrix extract (CME) was isolated from urinary CaOx monohydrate (COM) crystals. Cold and [14C]oxalate-labeled COM crystals were precipitated from ultrafiltered urine containing 0-5 mg/l CME. Crystal surface area was estimated from scanning electron micrographs, and synchrotron X-ray diffraction was used to determine nonuniform strain and crystallite size. Radiolabeled crystals were added to MDCKII cells and crystal dissolution, expressed as radioactive label released into the medium, was measured. Increasing CME content did not significantly alter crystal surface area. However, nonuniform strain increased and crystallite size decreased in a dose-response manner, both reaching saturation at a CME concentration of 3 mg/ and demonstrating unequivocally the inclusion of increasing quantities of proteins in the crystals. This was confirmed by Western blotting. Crystal dissolution also followed saturation kinetics, increasing proportionally with final CME concentration and reaching a plateau at a concentration of approximately 2 mg/l. These findings were complemented by field emission scanning electron microscopy, which showed that crystal degradation also increased relative to CME concentration. Intracrystalline proteins enhance degradation and dissolution of CaOx crystals and thus may constitute a natural defense against urolithiasis. The findings have significant ramifications in biomineral metabolism and pathogenesis of renal stones.

Association of serum levels of IGF-I and IGFBP-1 with renal function in patients with type 2 diabetes mellitus

OBJECTIVE

Our aim was to determine whether serum Insulin-like growth factor-I (IGF-I) and Insulin-like growth factor binding protein-1 (IGFBP-1) levels were different between type 2 diabetic patients and non-diabetic control group. We also aimed to establish any relationship that might exist between the serum IGF-I and IGFBP-1 levels with the urinary albumin excretion (UAE), creatinine clearance and urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion (as a marker of renal tubular dysfunction) and other parameters (such as age, duration of diabetes, treatment, etc.) in patients with type 2 diabetes mellitus (DM).

DESIGN

Fifty-nine type 2 diabetic patients and thirty-one non-diabetic controls were included in this study.

RESULTS

Mean serum IGF-I levels in diabetic patients were lower than the non-diabetic controls (158+/-12 vs. 287+/-26microg/l), (p<0.001). Serum IGFBP-1 levels were also higher in type 2 diabetic patients compared to the control group (67+/-5 vs. 35+/-4microg/l), (p<0.001). No relationship was obtained between IGF-I and IGFBP-1 levels with neither UAE nor urinary NAG excretion. A significant negative relationship was observed between creatinine clearance and serum IGFBP-1 level (r=-0.39, p=0.004). In multiple regression analysis IGF-I was independently and negatively associated with age and insulin treatment. On the other hand, IGFBP-1 was negatively related with creatinine clearance and positively related with the duration of diabetes.

CONCLUSION

These results suggest that type 2 DM leads to a decrease in the IGF-I while elevating the IGFBP-1 levels. Further studies are needed to clarify a potential role of increased levels of IGFBP-1 in decreased creatinine clearance in type 2 DM.

Acute, nonfatal intoxication with trichloroethylene

Nonfatal acute inhalation of trichloroethylene (TRI) at work was described. The subject, male, 54 years old, was drawn unconscious by a metal-degreasing machine and immediately sheltered in intensive care unit. Other than basic life support and common laboratory indices, blood and urine were collected to measure dose and kidney effect parameters such as TRI in blood and urine, trichloroethanol (TCE) and trichloroacetic acid (TCA) in urine, and total urinary proteins (TUP), urinary glutamine synthetase (GS) and urinary N-acetyl-beta-D-glucosaminidase (NAG). Two hours after accident, TRI in blood was 9 mg/l, but after 38 h it was below 1 mg/l. TCE and TCA have a peak 11 and 62 h after poisoning, respectively. Acute renal involvement was revealed by a peak of urinary proteins and enzymes 7 h after exposure with a second peak 74 h after. Seven day after hospitalisation the patient was dismissed with complete recovery. This nonfatal intoxication with TRI shows that the exposure was approximately 150 ppm, three times the ACGIH TLV (50 ppm) and that kidney was the only organ affected. Urinary enzymes, in particular GS, are good indices to monitor transient effects of TRI on the kidney.

Lysosomal enzymes in preeclamptic women in northern Nigeria

BACKGROUND

The incidence of preeclampsia is high in northern Nigeria, as it is in many other developing countries, and preeclampsia is associated with significant maternal and fetal morbidity and mortality. We inquired if proteinuria or hypertension alone could account for the altered concentrations of urinary lysosomal hydrolases that have been reported in preeclamptic women and pregnant women without preeclampsia.

METHODS

The activities of urinary beta-hexosaminidase and beta-galactosidase were determined fluorometrically in pregnant women assigned to one of four groups: Group I: 41 preeclamptic women; Group II: 31 hypertensive aproteinuric women; Group III: 44 normotensive proteinuric women; and Group IV: 52 healthy pregnant women (controls).

RESULTS

The urinary beta-hexosaminidase concentrations were decreased in the preeclamptic women (P<0.005) and proteinuric women (P<0.001) when compared to the healthy pregnant controls. There was no significant difference in beta-hexosaminidase concentrations between the hypertensive women and the healthy pregnant controls. The urinary beta-galactosidase concentrations for preeclamptic, hypertensive, and proteinuric women did not differ significantly versus healthy pregnant controls.

CONCLUSIONS

The reduced urinary excretion of beta-hexosaminidase in preeclamptic women is associated with proteinuria, but not hypertension. Measuring urinary concentrations of lysosomal hydrolases alone or in conjunction with urinary protein concentrations is not likely to be useful in predicting or monitoring the clinical course of preeclampsia; however, it might prove important in gaining a more complete understanding of the pathogenesis of renal tubular epithelial cell injury and proteinuria that occurs in preeclampsia.

Lipid peroxidation and its correlations with urinary levels of oxalate, citric acid, and osteopontin in patients with renal calcium oxalate stones

OBJECTIVES

To determine whether lipid peroxidation plays a role in patients with calcium oxalate kidney stones and to determine the correlation of lipid peroxidation with tubular damage and the major urinary risk factors. We also used the isoenzymes of glutathione S-transferase (GST) to examine which parts of the renal tubules were injured in patients with renal stones.

METHODS

This clinical study included two study groups. Group 1 included 32 normal volunteers, and group 2 included 32 patients with calcium oxalate kidney stones. A 24-hour urine sample was collected from each subject, and the levels of Ca, P, Mg, oxalate, citrate, N-acetyl-beta-glucosaminidase (NAG), beta-galactosidase (GAL), alphaGST, piGST, osteopontin (OPN), thiobarbituric acid-reactive substances (TBARS), and malondialdehyde (MDA) were examined.

RESULTS

Hyperoxaluria, hypocitraturia, and low urinary OPN were the major abnormalities found in the patients with stones. Elevated urinary alphaGST, NAG, and GAL were also noted in the patients with stones; however, urinary piGST showed no statistically significant difference compared with the controls. Urinary TBARS and MDA had statistically significant correlations with alphaGST, GAL, NAG, Ca, and oxalate, but had no correlation with piGST, citrate, OPN, Mg, and P. Urinary citrate had a negative, linear, and statistically significant correlation with alphaGST, GAL, and NAG.

CONCLUSIONS

Lipid peroxidation correlated with hyperoxaluria and renal tubular damage, indicating that hyperoxaluria can induce tubular cell injury and that this injury may be due to the production of free radicals in patients with calcium oxalate stones. Renal tubular damage in patients with stones may be limited to the proximal tubules.

Biological indices of kidney involvement in personnel exposed to sevoflurane in surgical areas

BACKGROUND

Fluoride, a main metabolite, and one degradation product of sevoflurane (SEV), called Compound A, are known to cause kidney effects in experimental animals. Other than in volunteers and patients, no research is available on exposed workers. The possible effects on the kidney in workers exposed in surgical areas were studied.

METHODS

Subjects exposed to SEV and nitrous oxide (N(2)O) in surgical areas (N = 61) using open (N = 25) or semi-closed (N = 36) circuits were submitted to biological monitoring. The same biological indices were determined in 43 controls also. Sevoflurane (SEVU), nitrous oxide (N(2)OU), total urinary proteins (TUP), N-acetyl-beta-D-glucosaminidase (NAGU), and glutamine synthetase (GSU) were measured in urine.

RESULTS

The mean values of environmental exposure were 31.3 ppm (range 0.9-111.6 ppm) for N(2)O and 0.28 ppm (range 0-1.88 ppm) for SEV. Exposed subjects had significantly higher excretion of TUP; a higher, not significant, excretion of GSU was also observed in subjects using open circuits. A significant correlation was found in all exposed subjects between NAGU and SEVU (r = 0.303, P < 0.05), GSU and N(2)OU (r = 0.382, P < 0.01) and, especially, GSU and SEVU (r = 0.650, P < 0.001). These correlations appeared to be influenced by the use of open circuits; infact, NAGU was well correlated to N(2)OU (r = 0.770, P < 0.001) and SEVU (r = 0.863, P < 0.001); GSU to N(2)OU (r = 0.468, P < 0.05) and SEVU (r = 0.735, P < 0.001).

CONCLUSIONS

Results show that no relevant effect on the kidney is present for the levels of exposure studied. Nevertheless, correlation between dose and response urinary indices supports that SEV, other than N(2)O, may influence kidney function, especially when open circuits are used.

Analysis of urinary N-acetyl-beta-D-glucosaminidase using 2,4-dinitrophenyl-1-thio N-acetyl-beta-D-glucosaminide as the substrate

2,4-Dinitrophenyl-1-thio N-acetyl-beta-D-glucosaminide was examined as a new substrate for analyzing the level of N-acetyl-beta-D-glucosaminidase in the urine of patients suffering from renal diseases. The analysis is based on the fact that the substrate, when hydrolyzed in the presence of N-acetyl-beta-D-glucosaminidase, liberates 2,4-dinitrothiophenol as the chromogen. The optimum pH for the enzyme reaction is 4.6, which is covered by the optimal range for the UV absorbance of the chromogen. The first-order rate of increase of the absorbance at this pH was linear to the enzyme concentration up to 600 U/L, with a high sensitivity. Analytical reagents with glucosaminides of 2,4-dinitrophenol and 2-chloro-4-nitrophenol are less stable than the reagent with glucosaminide of 2,4-dinitrothiophenol. The optimum pH for the absorbance of p-nitrophenol and 2-chloro-4-nitrophenol does not match that for the enzyme reaction.

Attenuation of oxalate-induced nephrotoxicity by eicosapentaenoate-lipoate (EPA-LA) derivative in experimental rat model

Hyperoxaluria is one of the major risk factors for the formation of urinary calcium oxalate stones. Calcium oxalate crystals and their deposition have been implicated in inducing renal tubular damage. Lipoic acid (LA) and eicosapentaenoic acid (EPA) have been shown to ameliorate the changes associated with hyperoxaluria. This prompted us to investigate the nephroprotectant role of EPA-LA, a new derivative, in vivo in hyperoxaluric rats. Elevation in the levels of calcium, oxalate and phosphorus, the stone-forming constituents, were observed in calculogenic rats as a manifestation of crystal deposition. Tubular damage to the renal tissue was assessed byassaying the excretion of marker enzymes in the urine. Damage to the tubules was indicated by increased excretion of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (gamma-GT), beta-Glucuronidase (beta-GLU) and N-Acetyl beta-D glucosaminidase (NAG). Fibrinolytic activity was found to be reduced. Administration of EPA, LA and EPA-LA reduced the tubular damage and decreased the markers of crystal deposition markedly, which was substantiated by the reduction in weight of bladder stone formed. Our results highlight that EPA-LA is the most effective drug in inhibiting stone formation and mitigating renal damage caused by oxalate toxicity, thus confirming it as a nephroprotectant. Further work in this direction is warranted to establish the therapeutic effectiveness of this new derivative.

Localization of annexin V in rat normal kidney and experimental glomerulonephritis

The localization of annexin V, a calcium binding protein, was immunochemically and immunohistologically studied in experimental rat glomerulonephritis using annexin V polyclonal antibody. Plasma and urinary annexin V levels were measured by a sandwich enzyme-linked immunosorbent assay (ELISA). Urinary annexin V level, which was correlated with urinary L-lactate dehydrogenase activity, N-acetyl-beta-D-glucosaminidase activity and protein level, increased time-dependently after the injection of nephritogenic antigen (bovine glomerular basement membrane), progressively increasing to attain a peak level at 4 weeks of 51.5 +/- 11.3 ng/h. However, plasma annexin V level showed no increase during the study period. Normal kidneys showed strong staining for annexin V in distal tubules, being particularly strong in tubules of the inner stripe of the outer medulla, but could not be detected in proximal tubules. Annexin V was seen in visceral epithelial cells. Bowman's capsule of the glomerulus, the vascular endothelium of arterioles and interlobular arteries, and vascular smooth muscle. In nephritis, the lumen of distal tubules and the luminal cell membrane were deeply stained, with leakage of annexin V being observed from tubular cells. In the present study, renal annexin V was markedly excreted into urine, and its urinary level reflected the severity of damage of renal tissue and the progression of nephritis. These changes of annexin V in the distal tubule and visceral epithelial cells may be of significance in cell injury of the kidney.

Measurement of urinary annexin V by ELISA and its significance as a new urinary-marker of kidney disease

To confirm the significance of excretion of annexin V into the urine and the change of urinary annexin V concentration in kidney disease, a sandwich enzyme-linked immunosorbent assay (ELISA) was developed using two monoclonal antibodies. Urinary annexin V concentration was measured in healthy individuals and patients with kidney and other diseases. Urinary annexin V did not change over a range of pH between 5.0 and 8.0, and was stable during the course of the study for 24 h at room temperature and for 8 days at 4 degrees C. The mean urinary annexin V concentration in 105 normal healthy individuals was 1.5+/-1.5 ng/ml, while that in patients with nephrotic syndrome and systemic lupus erythematosis (SLE) nephritis was 9.3+/-9.1 and 6.6+/-6.7 ng/ml, respectively, and that in IgA nephropathy and chronic renal failure was 2.6+/-2.1 and 1.3+/-0.7 ng/ml, respectively. Annexin level correlated with urinary protein concentration (r=0. 717), but not the serum creatinine concentration, blood urea nitrogen (BUN) and 24-h creatinine clearance. Mean urinary annexin V concentration in patients with ischemic heart disease, hypertension, and diabetes mellitus was 1.4+/-1.0, 1.4+/-1.1, and 1.7+/-1.3 ng/ml, respectively. In one case of relapsing nephrotic syndrome, the urinary annexin V concentration was markedly increased in the early phase after admission and then decreased. This patient later required hemodialysis. These results suggest that a high urinary annexin V concentration may be an indicator of acute renal injury related to the urinary protein level.

Circulating adhesion molecules and neutral endopeptidase enzymuria in patients with urolithiasis and hydronephrosis

OBJECTIVES

To measure the concentrations of adhesion molecules (intercellular adhesion molecule-1 ¿ICAM-1, E-selectin, and L-selectin) in the serum of patients with renal stones and patients with hydronephrosis caused by obstructive ureteral stones. Renal tubular enzymes were examined from their urine samples to evaluate whether neutral endopeptidase (NEP) behaved as traditional tubular enzyme markers (N-acetyl-beta-glucosaminidase ¿NAG and beta-galactosidase ¿beta-GAL) in their disease state.

METHODS

Three groups were studied. Group 1 included 15 normal volunteers, group 2 included 12 patients with ureteral stones and ipsilateral hydronephrosis, and group 3 included 17 patients with renal stones in one kidney without hydronephrosis or hydrocalycosis. A single, overnight fasting blood and urine sample was collected from each subject. Serum levels of ICAM-1, E-selectin, and L-selectin were measured by enzyme-linked immunosorbent assay. NEP, NAG, and beta-GAL were measured from urine samples, and the enzyme activities were expressed per gram of creatinine.

RESULTS

Serum levels of ICAM-1 were higher in groups 2 and 3 (522 +/- 95 and 329 +/- 42 ng/mL, respectively), but the differences were only significant between group 2 and group 1 (263 +/- 32 ng/mL) and group 2 and group 3 (P <0.05). Serum levels of L-selectin were lower in group 3 and were significantly different when compared with groups 1 and 2 (P <0. 05). The serum levels of E-selectin were not significantly different among these three groups. Urinary levels of NEP were lower in group 2, although the levels of NAG and beta-GAL were more elevated than in group 1.

CONCLUSIONS

Serum levels of ICAM-1 were elevated in patients with unilateral hydronephrosis caused by a ureteral stone, and E-selectin and L-selectin levels did not change significantly. These findings suggest that ICAM-1 may play a role in renal immune injury to ureteral obstruction. The urinary NEP values were lower in patients with hydronephrosis caused by ureteral stones, and the traditional lysosomal enzymes were increased. The lower urinary NEP values might suggest impairment of ipsilateral renal function. Renal stones per se resulted in no significant changes in serum adhesion molecule levels, although the levels of L-selectin were significantly decreased.

Calcitonin stimulates lysosomal enzyme release and uptake in LLC-PK1 cells

Renal tubular targeted hormones increase urinary excretion of a lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG). To elucidate the mechanism of this event, the calcitonin effect on NAG handling by LLC-PK1 cells was examined. Calcitonin (1 nM to 1 microM), phorbol myristate (10 nM to 1 microM), and ionomycin (1 to 10 microM) promoted NAG release without any increase in lactate dehydrogenase release or any reduction of mitochondrial dehydrogenase activity. Treatment with 100 nM calphostin C or 50 microM KN-93 partially reversed the calcitonin effect on NAG release. Calcitonin promoted secretion of fluorescence ceramide, a reporter of protein transport from Golgi apparatus to cell surface. Calcitonin-stimulated NAG release was partially inhibited by 10 microg/ml brefeldin A, a blocker of protein transport through the Golgi apparatus. Calcitonin accelerated cellular uptake of exogenous NAG, which was inhibited by low temperature, 0.1 mM monodansyl cadaverine (receptor-mediated endocytosis inhibitor), and 10 mM mannose-6-phosphate. Furthermore, calcitonin promoted progression of intracellular membranes stained by a fluorescence membrane marker, styryl pyridinium dye, from cell periphery to perinuclear regions (commonly referred to as recycling vesicles) and increased dye release from preloaded cells. Fluorescence release from the cells pre-loaded with FITC-labeled NAG or albumin was also stimulated by calcitonin. These calcitonin effects on endocytotic and re-exocytotic pathways were inhibited by 100 nM cytochalasin D, 100 nM nocodazole, 0.1 to 1 microM bafilomycin A1, or 0.1 mM monodansyl cadaverine. Increased urinary NAG excretion has been considered to reflect renal tubular damage. However, it was demonstrated here that stimulation of secretory and recycling pathways may be an alternative mechanism for calcitonin-induced enzymuria, which will become a new indicator of renal tubular response to this hormone.

Effect of age on urinary excretion of N-acetyl-beta-D-glucosaminidase

To examine the relationship between the concentrations of urinary NAG and age, we measured ratios of urinary N-acetyl-beta-D-glucosaminidase (NAG) to urinary creatinine (NAG index) in 137 healthy subjects, aged from 19 to 88 years. The study is also designed to evaluate the relationship between urinary NAG and blood pressure. The subjects were divided into 7 subgroups, according to their age (< 30, 30-39, 40-49, 50-59, 60-69, 70-79, 80 or more years). There was a positive correlation between NAG index and age (r = 0.36; P < 0.001). The regression equation relating NAG index (y) to age (x) was y = 0.065x + 0.97. The mean NAG indexes for the 7 subgroups divided by age were significantly different (P < 0.01). There was a positive correlation between NAG index and systolic blood pressure (r = 0.18; P < 0.05), but was not between diastolic blood pressure and NAG index. In multiple regression analysis, age and BUN significantly correlated with NAG index (r = 0.32; P < 0.01, r = 3.3; P = 0.07, respectively), although there was no correlation between systolic blood pressure and NAG index. This cross-sectional study showed a clear elevation in NAG index with age. The rate of elevation was 0.65 per decade. Urinary excretion of NAG may be unrelated to blood pressure.

Sodium pentosan polysulphate--a novel inhibitor of urinary risk factors and enzymes in experimental urolithiatic rats

Sodium pentosan polysulphate (SPP) has been shown to inhibit calcium oxalate crystallization in vitro. Here, the effect of SPP was studied on in vivo crystallization. Ammonium oxalate was used as the inducer of calcium oxalate crystallization in rats and the effect of SPP on in vivo crystallization factor is reported. The increased excretions of stone forming constituents associated with urinary marker enzymes are the salient features observed in experimental rats. Sodium pentosan polysulphate administration brought about a significant reduction in urinary stone forming constituents. It also decreased the extent of renal tubular damage as evidenced from the reduced level of marker enzymes in urine. These observations highlight the inhibitory capacity of SPP against in vivo calcium oxalate crystallization.

Renal injury mediated calcium oxalate nephrolithiasis: role of lipid peroxidation

The role of lipid peroxidation (LPO) in renal tubular damage mediated calcium oxalate retention was investigated in a rat model. Hyperoxaluria, without deposition of oxalate in kidney, was induced by administration of ethylene glycol (EG), a precursor of oxalate. Oxidative stress condition was produced by administration of buthionine sulfoximine (BSO), an inhibitor of glutathione biosynthesis. BSO-treated rats showed a significant (p < 0.001) increase in LPO over EG-treated rats and it was almost doubled in BSO + EG treated rats. LPO was accompanied by significant urinary excretion of renal damage marker enzymes such as gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase (ALP) and cathepsin D, mucoproteins, and glycosaminoglycans (GAGs) in the BSO and BSO + EG groups but not in the EG group. Urinary excretion of gamma-GT (r = +0.90) (p < 0.001) and deposition of oxalate (r = +0.78) (p < 0.001) in kidney positively correlated with LPO. These results suggest that LPO initiates renal damage, thereby leading to calcium oxalate retention and stone formation.

Lysosomal enzymuria in preeclampsia

We hypothesize that the preeclamptic patient has proximal tubule epithelial injury, which leads to the release of lysosomal enzymes, and that the excretion of these enzymes might serve as a diagnostic or predictive marker in preeclamptic women. The study group consisted of 14 women with preeclampsia (10 severe and 4 mild, as defined by The American College of Obstetricians and Gynecologists criteria) and 28 normotensive controls with singleton pregnancies at 27 to 41 weeks. There were no significant differences between the two groups for gestational age, maternal age, or race. Maternal serum and urine specimens were prospectively obtained and analyzed for beta-glucuronidase, beta-hexosaminidase, alpha-galactosidase, beta-galactosidase, and alpha-mannosidase using fluorometric assays. Median serum and urine activities and fractional excretions of each of the five hydrolases were compared between the two study groups using the Mann-Whitney two-sample rank test. The serum enzyme activities of beta-hexosaminidase (P = 0.002), alpha-galactosidase (P = 0.0001), and alpha-mannosidase (P = 0.02) were significantly lower in preeclamptic patients than in controls. The urine enzyme activities of beta-glucuronidase (P = 0.001), alpha-galactosidase (P = 0.002), beta-galactosidase (P 0.0003), and alpha-mannosidase (P = 0.003) were significantly higher in the preeclamptic patients. The fractional enzyme excretions of all five lysosomal hydrolases were higher in preeclamptic patients than in controls with P < or = 0.0003 for each enzyme. Preeclampsia is associated with a significant decrease in serum activities of three of the five hydrolases studied, a significant increase in urine enzyme activities in four of the five hydrolases studied, and a significant increase in the fractional excretion of all five lysosomal hydrolases.

Effect of lupeol, a pentacyclic triterpene, on urinary enzymes in hyperoxaluric rats

Investigations were undertaken to study the role of lupeol, a pentacyclic triterpene from Crataeva nurvala stem bark, in calcium oxalate experimental rat urolithiasis. A 2% solution of ammonium oxalate was administered by gastric intubation for inducing hyperoxaluric condition in adult male rats of Wistar strain. The duration of treatment was for 15 days. This resulted in increased urinary excretion of oxalate associated with reduction in citrate and glycosaminoglycans. The urinary marker enzymes which indicate renal tissue damage namely--lactate dehydrogenase, inorganic pyrophosphatase, alkaline phosphatase, gamma glutamyl transferase, beta-glucuronidase and N-acetyl beta-D glucosaminidase were found to be elevated. Lupeol administration (25 mg/kg body weight/day) reduced significantly the renal excretion of oxalate. It also reduced the extent of renal tubular damage as evidenced from the decreased levels of the above enzymes in urine. Such a reduction is likely to be beneficial in minimizing the deposition of stone-forming constituents in the kidney which provides antilithic effect.

Increased urinary N-acetyl-beta-glucosaminidase (NAG) excretion in young insulin-dependent diabetic patients

We evaluated urinary N-acetyl-beta-glucosaminidase (NAG) excretion in overnight and in second morning urine in 50 young diabetic patients, aged 7.4-25 years with a disease duration from 2-19.6 years. In all patients we evaluated urinary NAG and creatinine excretion, in both overnight and second morning urine, glycosuria, fasting blood glucose and HbA1c levels, insulin requirement, blood pressure, and the presence of microangiopathic complications. Urinary NAG excretion was also evaluated in 69 age- and sex-matched controls. NAG was determined using 3-cresolsulfonphtaleinyl-beta-N-acetylglucosaminide as substrate (Boehringer Mannheim, Germany). In the diabetic patients NAG/Cre ratios were significantly higher than in controls both in overnight and second morning urine (P < 0.0005, respectively). We observed significantly higher NAG/Cre ratio levels in the second morning than in overnight urine, both in controls and in diabetics (P < 0.0005, respectively). Elevated (above 2 S.D. of the mean) NAG/Cre ratios were found in 17/50 patients (34%) in overnight urine and in 29/50 (58%) in second morning urine. No correlation was observed between NAG/Cre ratio levels and age, duration of disease, pubertal stage, body mass index, fasting blood glucose, glycosuria, insulin requirement and blood pressure. The patients with one or more complications did show NAG/Cre ratio levels significantly higher than those without complications (P < 0.005) in second morning urine, but not in overnight urine. Our study has demonstrated an increased rate of urinary NAG excretion in young IDDM patients, in particular in those with microangiopathic complications.

Urinary N-acetyl-beta-glucosaminidase activity in type I diabetes mellitus

A commercial method for N-acetyl-beta-glucosaminidase (NAG) is described for use on a discrete analyser. Timed overnight urine was obtained from 20 healthy volunteers and 60 Type I diabetic patients for estimation of NAG (expressed in relation to creatinine) and albumin excretion rate (AER). The upper reference limit for NAG excretion in the control patients was found to be 0.25 U/mmol creatinine but was abnormally raised in 60% of Type I diabetic patients before any increase in AER (greater than 20 micrograms/min), and in 82% of patients with AER greater than 200 micrograms/min. A positive correlation was found between NAG excretion and AER in Type I diabetes (r = 0.61, p < 0.01), but not with glycaemic control as measured by serum fructosamine levels. We conclude that measurement of NAG excretion in diabetes indicates renal tubular dysfunction or damage before any significant change in albumin excretion rate.

The effect of endogenous parathyroid hormone, exogenous calcitonin, and dibutyryl cyclic AMP on urinary excretion of N-acetyl-beta-D-glucosaminidase

Urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) transiently increases after PTH(1-34) infusion in idiopathic hypoparathyroidism (IHP) but this response is impaired in pseudohypoparathyroidism (PHP) type I. We investigated the effects of endogenous PTH, exogenous calcitonin (CT), and dibutyryl cAMP (DBcAMP) on urinary excretion of NAG. Urinary NAG excretion in 14 patients with primary hyperparathyroidism (1 degree HPT) was more than in normal subjects (P < 0.001) and decreased after parathyroidectomy (P < 0.01). Urinary NAG excretion increased after the infusion of 1.5 MRC/kg of eel CT in eight normal subjects (P < 0.001), two patients with IHP, and a patient with PHP type Ib but not in a patient with PHP type Ia. The increases of urinary NAG excretion by CT and by PTH(1-34) were positively correlated with the increases of urinary cAMP excretion (r = 0.752; P < 0.001 and r = 0.534; P < 0.002, respectively). Urinary NAG excretion increased after DB-cAMP infusion in five normal subjects (P < 0.01), two patients with IHP, and two with PHP type I. The increase of urinary NAG by 6.0 mg/kg of DBcAMP was more than by 2.5 mg/kg of DBcAMP in normal subjects (P < 0.01). The increase of urinary NAG by 2.5 mg/kg of DBcAMP in PHP type I was comparable with that by 6.0 mg/kg in normal subjects, suggesting a hyperresponsiveness to DBcAMP in PHP type I. Urinary excretion of NAG is a useful indicator of renal tubular responsiveness to PTH and CT. Cyclic AMP-dependent mechanism is probably involved in PTH and CT-induced increase in urinary excretion of NAG.

Decreased renal excretion of beta-hexosaminidase in adults with insulin-dependent diabetes mellitus and normal renal function

The activities of three lysosomal hydrolases and creatinine levels were measured in the plasma and urine of 11 adults (mean age, 28.1 years) with insulin-dependent diabetes mellitus and 14 non-diabetic controls (mean age, 27.9 years). All of the patients were free of diabetic complications and non exhibited microalbuminuria. Fractional enzyme excretion (FEE) values between the two groups of subjects were calculated and compared for the following enzymes: beta-hexosaminidase (N-acetyl-glucosaminidase), beta-glucuronidase and alpha-galactosidase. The FEE value was calculated as the ratio of enzyme clearance to creatinine clearance. Relative to the non-diabetic control group, the FEE value for beta-hexosaminidase was approximately 2-fold lower (P = 0.02) in the diabetic subjects (means, 0.424 vs. 0.242, respectively). The FEE values for beta-glucuronidase and alpha-galactosidase were not significantly different (P > 0.4) between the diabetic and control groups. These easily measured biochemical parameters in blood and urine and the resultant FEE value for beta-hexosaminidase may provide a means of assessing subtle deteriorative changes in renal function which occur in the early stage of diabetes before the onset of clinically evident complications.

Prospective study of the enzymatic activities in urine of N-acetyl-beta-D-glucosaminidase, alpha-D-mannosidase, alpha- and beta-D-glucosidases, alpha-L- and beta-D-fucosidases, and beta-D-galactosidase in type I diabetes mellitus with early nephropathy

Different surveys have been carried out on the plasma activities of different glycosidases in patients with insulin-dependent diabetes mellitus, but research on urinary glycosidases in this disease is scanty and incomplete. To elucidate the behavior of these lysosomal enzymes in the metabolic alterations occurring in the glomerular basal membrane during the initial stages of diabetic nephropathy, we conducted a prospective study to examine the urinary activities of N-acetyl-beta-D-glucosaminidase (NAG), alpha-D-mannosidase, alpha- and beta-D-glucosidase, alpha-L- and beta-D-fucosidase, and beta-D-galactosidase in patients with type I insulin-dependent diabetes mellitus, surveyed over 18 months, whose early diabetic nephropathy was detected by the presence of microalbuminuria. The simultaneous determination of beta 2-microglobulin in urine confirmed the glomerular origin of the albuminuria. No statistically significant correlation was found between the levels of albuminuria and the activities of any of the glycosidases analyzed. In the diabetic patients, a significant decrease was observed in the activities of all the enzymes (p < 0.05), except NAG and alpha-D-mannosidase, although the decrease in the latter was very close to statistical significance (p = 0.028, unilateral; p = 0.057 bilateral). Similarly, in the patients, there was a significant negative correlation (p < 0.05) with the serum levels of fructosamine, except with beta-D-galactosidase, which showed a positive correlation (p < 0.05) with fructosamine and blood HbA1c.(ABSTRACT TRUNCATED AT 250 WORDS)

A thromboxane A2 synthetase inhibitor retards hypertensive rat diabetic nephropathy

Spontaneously hypertensive rats (SHR) were injected with streptozotocin (STZ-SHR) to induce diabetes. The effect of DP-1904, a thromboxane A2 synthetase inhibitor, on diabetic nephropathy was then studied by administering it for 5 months (1 or 10 mg/kg). DP-1904 did not affect renal 6-keto prostaglandin (PG)F1 alpha production in STZ-SHR, but markedly inhibited renal thromboxane (TX) B2 production, so that the 6-keto PGF1 alpha/TXB2 ratio was significantly increased (P less than 0.05). STZ-SHR showed significant uraemia and proteinuria, plus increases in urinary gamma-glutamyl-transpeptidase and urinary N-acetyl-beta-glucosaminidase. DP-1904 significantly decreased (P less than 0.01) the urinary changes. STZ-SHR also showed an increase in mesangial periodic acid-Schiff-positive substance and in relative renal weight, both of which were significantly inhibited by DP-1904 (P less than 0.05). Thus, DP-1904 inhibited both TXB2 production and the progression of renal damage in STZ-SHR.

Urinary N-acetyl-beta-D-glucosaminidase as a marker of renal injury in adjuvant arthritis

In the present study we have determined if renal damage occurs with adjuvant arthritis (AA). As a sensitive indicator of renal injury in tubular cells, urinary N-acetyl-beta-D-glucosaminidase (NAG) was measured at predetermined times after arthritis induction. Urinary protein, sodium and potassium excretion were also evaluated. NAG levels in arthritic animals were higher than those in healthy ones from day 12 after induction and the levels remained high during the study period. A significant positive correlation was noted between urinary NAG excretion and disease severity reflected by hind paw edema. Protein excretion also increased in arthritic animals but there was no correlation between urinary protein, NAG levels, and degree of inflammation. Changes in urine sodium and potassium levels did not reach statistical significance. Thus, we can conclude that some renal damage occurred in this experimental model of chronic inflammation.

Urinary N-acetyl-beta-D-glucosaminidase activity in lead-exposed workers

The adverse effects of long-term exposure to lead dust on renal tubular functions were studied in 39 male and 7 female workers in a secondary lead refinery. Laboratory examinations showed low or moderate lead absorption levels. The N-acetyl-beta-D-glucosaminidase (NAG) activity in urine showed significant correlation with each of the lead exposure indices. NAG activity increased remarkably in lead workers with blood lead (PbB) above 80 micrograms 100g-1. Blood urea nitrogen (BUN) showed significant correlation with PbB and logarithmic urine delta-amino-levulinic acid (log(ALAU)), but not with urine lead (PbU) and logarithmic urine coproporphyrin (log(CPU)). All the other indices of renal function were almost within the normal range and showed no correlation with lead indices. This study suggests that moderate lead absorption may cause renal tubular impairment, and NAG can be one of the most sensitive indices for estimating renal dysfunction due to lead poisoning.

Effects of parathyroid hormone on urinary excretion of N-acetyl-beta-D-glucosaminidase in idiopathic hypoparathyroidism and pseudohypoparathyroidism

N-acetyl-beta-D-glucosaminidase (NAG) is a lysosomal enzyme predominantly located in renal proximal tubules. In idiopathic hypoparathyroidism (IHP), 100 Units of human PTH (1-34) increased urinary excretion of NAG from 0.029 +/- 0.027 to 0.173 +/- 0.035 U/lGF (p less than 0.05) in two patients before treatment and from 0.025 +/- 0.004 to 0.189 +/- 0.092U/lGF (p less than 0.02) in four patients during treatment with active vitamin D3 (1,25(OH)2D3 or 1 alpha OHD3). In pseudohypoparathyroidism (PHP), PTH did not significantly increase the urinary excretion of NAG in one patient with before treatment (0.048 to 0.025 U/lGF) and four patients during treatment with active vitamin D3 (0.018 +/- 0.008 to 0.036 +/- 0.015 U/lGF). Increase in urinary excretion of NAG after injection of PTH may be a new indicator of renal effect of PTH.

Urinary enzymes and calcium oxalate urolithiasis

Male Sprague-Dawley rats were challenged with various hyperoxaluric agents including ammonium oxalate, hydroxy-L-proline, and ethylene glycol. All treatments resulted in increased urinary oxalate. Associated with hyperoxaluria was an increase in urinary levels of renal enzymes, gamma-glutamyl transpeptidase, N-acetyl-beta-glucosaminidase, and alkaline phosphatase. Most of the rats did not demonstrate any significant change in urinary levels of beta-galactosidase. There was a highly significant positive correlation between urinary oxalate and N-acetyl-beta-glucosaminidase.