Direct amifostine effect on renal tubule cells in rats.
(17/982)
Clinical trials indicate that amifostine offers protection against cisplatin-induced nephrotoxicity. It is unclear whether a direct pharmacological t on renal tubular cells is involved. We investigated the effect of amifostine pretreatment on the tubular apparatus and evaluated its nephroprotective potential. A total of 32 rats were treated by i.p. administration of 0.9% saline solution (group 1), 5 mg/kg cisplatin (group 2), 25 mg/kg amifostine (group 3), and 25 mg/kg amifostine followed by 5 mg/kg cisplatin (group 4) after 30 min. We recorded elevation of N-acetyl-beta-D-glucosaminidase (NAG) in 24 h pooled urine as a specific marker for tubular lesions, renal leakage of magnesium as an unspecific nephrotoxicity marker, and survival over a 10-day observation period. A significant (P < 0.002) increase in urinary NAG after treatment was documented only in cisplatin-treated group 2 [day 2 (mean+/-SE), 93+/-2.1 units/gram creatinine; day 4, 70.6+/-16 units/gram creatinine; normalization at day 8]. Treatment with amifostine before cisplatin administration resulted in a slight urinary NAG leakage (day 2, 2.8+/-1.8 units/gram creatinine; day 4, 13.8+/-13 units/gram creatinine; normalization at day 6). No increase in urinary enzyme levels was seen in the other groups, and there were no significant differences in urinary magnesium between all groups. Four of eight rats in the cisplatin-treated group and one of eight rats in the amifostine plus cisplatin-treated group died. (+info)
Coordinate augmentation in expression of genes encoding transcription factors and liver secretory proteins in hypo-oncotic states.
(18/982)
BACKGROUND: In the nephrotic syndrome (NS) proteins of intermediate size (40 to 200 kD) are lost into the urine resulting in a decrease in plasma albumin concentration and as a consequence a reduction in plasma colloid osmotic pressure (pi). Plasma pi has also been reported to be reduced in the condition of hereditary analbuminemia. The liver, in an apparent compensatory response, increases synthesis of a group of secreted proteins defending plasma pi. Regulation of several of these proteins, including both positive and negative acute phase proteins, is at the transcriptional level. This is the only known condition in which transcription of both positive and negative acute phase proteins (APPs) are increased simultaneously. The specific transcription factor(s) that might regulate this cascade is not defined. METHODS: RNA was extracted from livers of 5 rats with hereditary analbuminemia (the Nagase analbuminemic rat, NAR), 5 rats with NS induced by adriamycin (Adria), 5 rats with NS caused by passive Heymann nephritis (NS) and 5 control animals. The concentrations of mRNAs encoding four secreted proteins (albumin, transferrin, fibrinogen, and apo A-1), five transcription factors, early growth response factor 1 (EGRF-1), HNF-4, NGFI-C, EGR-3, and Krox20 relative to two housekeeping genes, beta actin and GAPDH were determined simultaneously using kinetic reverse transcriptase polymerase chain methodology (kRT-PCR). RESULTS: The levels of all mRNAs encoding secreted proteins except for albumin (which was reduced in NAR) were increased in NS and NAR and correlated significantly with one another. mRNA encoding EGRF 1 was increased fivefold in NS and NAR, and correlated significantly with mRNAs encoding Apo A-1, transferrin and albumin in the two NS groups. HNF-4 mRNA was increased approximately twofold in both NS groups and correlated with albumin (R = 0.881, P < 0.001), transferrin (R = 0.563, P = 0.012) and apo A-1 (R = 0.644, P = 0. 003). While fibrinogen mRNA correlated with that of each of the other secreted proteins, it did not correlate with either HNF-4 or EGRF-1 mRNA. Krox20, EGR3 and NGF1C were expressed at nearly undetectable levels. CONCLUSIONS: The hepatic response in conditions characterized by reduced plasma pi include increased levels of mRNAs encoding a group of secreted proteins, including the negative APPs albumin, transferrin and apo A-1, and the positive APP fibrinogen. Levels of mRNAs encoding negative APPs and fibrinogen correlate with one another, suggesting that they are coordinately controlled. Both EGRF-1 and HNF-4 may regulate the expression of the negative APPs, which have increased transcription in hypo-oncotic states. (+info)
Calcitonin stimulates lysosomal enzyme release and uptake in LLC-PK1 cells.
(19/982)
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. (+info)
Human parathyroid hormone (1-34) transiently increases the excretion of lysosomal enzymes into urine and the size of renal lysosomes.
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It has been reported that the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme, transiently increases in human after treatment with human parathyroid hormone (hPTH)(1-34). We report here that hPTH(1-34) caused transient changes in the size and density of rat renal lysosomes following urinary excretion of NAG and other lysosomal enzymes tested. Percoll density gradient centrifugation revealed that hPTH(1-34) slightly but significantly increased the fraction of high density lysosomes (around 1.12 g/ml) 5-10 min after the treatment with hPTH(1-34), with a concomitant decrease in the fraction of intermediate density lysosomes (1.07-1.08 g/ml). On electron micrographs, some lysosomes in proximal tubules but not in distal tubules showed a change in morphology from circular to oval, and became enlarged and electron-dense 5-10 min after the treatment with hPTH(1-34). These responses to hPTH(1-34) were also reversible and transient. NAG excreted in urine after treatment with hPTH(1-34) had the molecular mass of a mature form in lysosomes and/or endosomes and was not a prepro-and/or pro-form of the enzyme. Thus, the changes in the density and size of renal lysosomes appear to be associated with the exocytosis of lysosomal enzymes by hPTH(1-34). (+info)
Purification, characterization and gene analysis of N-acetylglucosaminidase from Enterobacter sp. G-1.
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Enterobacter sp. G-1 is a bacterium isolated previously as a chitinase-producing bacterium. We found this bacterium also produced N-acetylglucosaminidase and characterized that in this study. Extracellular N-acetylglucosaminidase of 92.0 kDa was purified near homogeneity by 8.57-fold from Enterobacter sp. G-1. The optimum temperature and the optimum pH of the purified N-acetylglucosaminidase was 45 degrees C and 6.0, respectively. The N-terminal amino acid sequence of 23 residues of N-acetylglucosaminidase was identified. Based on the N-terminal sequence, we amplified pieces of the DNA fragments by PCR. Using these PCR products as probes, we screened the genomic library and successfully isolated the entire N-acetylglucosaminidase gene (designated nag1) from Enterobacter sp. G-1. The nucleotide sequence of the nag1 gene was found to consist of 2,655 bp encoding a protein of 885 amino acid residues. Comparison of the deduced amino acid sequence from the nag1 gene found 97.3% identity with chitobiase from Serratia marcescens, 54.4% identity with N,N'-diacetylchitobiase from Vibrio harveyi, and 42.7% identity with N-acetylglucosaminidase (ExoI) from Vibrio furnissii. Enzymatic activity assay of N-acetylglucosaminidase indicated stronger activity toward PNP-GlcNAc than PNP-(GlcNAc)2 or PNP-(GlcNAc)3. (+info)
Metallothionein protects against the nephrotoxicity produced by chronic CdMT exposure.
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Metallothionein (MT) is a low-molecular-weight, cysteine-rich, metal-binding protein. Induction of MT has been proposed to be an important adaptive mechanism in decreasing Cd toxicity. MT has been shown to protect against CdCl2-induced lethality and hepatotoxicity; however, MT does not protect against acute CdMT-induced nephrotoxicity. This study was aimed at clarifying the role of metallothionein in chronic CdMT-induced renal injury. Wild type and MT-I/II knockout (MT-null) mice were therefore given sc injections of CdMT (25 and 100 microg Cd/kg) or saline daily, 6 times/week for 6 weeks, and renal injury was evaluated. Multiple injections of CdMT to wild-type mice resulted in renal Cd concentrations up to 120 microg/g kidney, along with a 100-fold increase in renal MT (450 microg/g kidney). In contrast, renal Cd concentration in MT-null mice administered multiple injections of CdMT reached a much lower level than in wild-type mice (<10 microg/g kidney). Although less Cd accumulated in their kidneys, MT-null mice were more susceptible than wild-type mice to CdMT-induced nephrotoxicity, as indicated by increased urinary excretion of protein and N-acetyl-beta-D-glucosaminidase, as well as by elevated blood urea nitrogen levels. At the higher daily dose of CdMT (100 microg Cd/kg), kidneys of MT-null mice were enlarged. Chronic CdMT administration eventually damaged the entire kidney, which included glomerular swelling, interstitial inflammation, edema, tubular cell degeneration, and atrophy. In contrast to a single injection of CdMT that produces proximal tubular necrosis, chronic injection of CdMT results in tubular cell apoptosis in both wild-type and MT-null mice. These data indicate that chronic CdMT administration produces similar renal injury to that observed after chronic CdCl2 administration, and that intracellular MT protects against nephrotoxicity produced by chronic CdMT administration. (+info)
Quantitation and isomeric structure analysis of free oligosaccharides present in the cytosol fraction of mouse liver: detection of a free disialobiantennary oligosaccharide and glucosylated oligomannosides.
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The amounts and isomeric structures of free oligosaccharides derived from N-linked sugar chains present in the cytosol fraction of perfused mouse liver were analyzed by tagging the reducing end with 2-aminopyridine followed by 2-dimensional HPLC mapping with standard sugar chains. Sixteen pyridylaminated (PA-) oligomannosides terminating with a PA-GlcNAc residue (GN1-type), three glucose-containing oligomannosides, and four oligomannosides terminating with a PA-di-N-acetylchitobiose (GN2-type) were detected. The total contents of the GN1- and GN2-type oligomannosides were 3. 4 and 0.5 nmol, respectively, per gram of wet tissue. Maltooligosaccharides (dimer to pentamer) were also detected, the total content of which was 13 nmol per gram of wet tissue. Besides these oligosaccharides, a PA-disialobiantennary sugar chain-the sole complex-type sugar chain-was also detected. All the oligomannosides identified had partial structures of Glc(3)Man(9)GlNAc(2)-p-p-dolichol, revealing that they were metabolic degradation products. Manalpha1-2Manalpha1-2Manalpha1-3(Manalpha1-6)++ +Manbeta1-4GlcNAc (M5B') was the major oligomannoside, suggesting that cytosolic endo-beta-N-acetylglucosaminidase and neutral alpha-mannosidase participate in the degradation, because these enzymes have suitable substrate specificities for the production of M5B'. Degradation by these enzymes seems to be the main pathway by which oligomannosides are degraded in mouse cytosol; however, small amounts of Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3) Manbeta1-4(GlcNAc)1-2 and related oligomannosides together with parts of their structures were also detected, suggesting that there is another minor route by which cytosolic free oligomannosides are produced. (+info)
Prospective evaluation of urinary N-acetyl-beta-D-glucosaminidase with respect to macrovascular disease in elderly type 2 diabetic patients.
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OBJECTIVE: To analyze prospectively the importance of urinary N-acetyl-beta-D-glucosaminidase (NAG), a marker for renal tubular function, in comparison with urinary albumin excretion (UAE), a marker for glomerular renal function, with respect to macrovascular disease in elderly patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We followed 124 patients over a mean period of 7.0 +/- 0.5 years. At baseline, urinary NAG, UAE, age, diabetes duration, sex, blood pressure, lipids, and serum creatinine were determined. Also, history of myocardial infarction (MI), stroke, severe peripheral vascular disease (PVD), antidiabetic and concomitant medication, and smoking habits were recorded. After 7 years, patients were reevaluated, and a multivariate logistic regression analysis was used to test risk factors for significance in order to predict macrovascular disease. Subgroups of patients were analyzed with respect to severe macrovascular disease, with a separate analysis for surviving patients. RESULTS: Compared with known cardiovascular risk factors such as microalbuminuria and total cholesterol, urinary NAG was similarly associated with cardiovascular disease for the total cohort (P < 0.05). Analyzing the subgroup of 65 patients still alive after follow-up care, urinary NAG and UAE were significantly elevated at baseline and at the time of follow-up care in patients with MI and PVD, but not in those with stroke (P < 0.01). There was a positive predictive trend of NAG excretion for the development of MI and PVD in our patients (P = 0.07). CONCLUSIONS: Urinary NAG proved comparable to UAE when analyzed with respect to preexistence and development of severe macrovascular disease. It needs to be determined by further studies if urinary NAG will be of value to serve as an adjunct marker to UAE in type 2 diabetic patients. (+info)