ACE genotype and progression of IgA nephropathy.
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Adult↗
Biomedical subjects
L Paczek
Publications and source records attributed to L Paczek.
Rejection-associated abnormalities of T-cell interactions with extracellular matrix.
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Antigens, CD↗
Intraglomerular cathepsin B and L activity in chronic kidney allograft rejection.
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Acute Disease↗
Lovastatin ameliorates depressed intraglomerular proteolytic activities in experimental nephrotic syndrome.
Lipid abnormalities have been implicated in the pathogenesis of glomerulosclerosis in experimental models of kidney disease. In previous studies it has been shown that Adriamycin-induced nephropathy is associated with reduced activities of glomerular proteinases. This observation led to the hypothesis that reduced proteolytic activities may be responsible for mesangial protein accumulation, which ultimately leads to global sclerosis of the glomerular tuft. The aim of the present study was to investigate whether lovastatin treatment, which prevents progressive glomerulosclerosis in experimental nephrotic syndrome, would also have an effect on glomerular proteinase activities. Adriamycin administration resulted in a persistent nephrotic syndrome with gross proteinuria (377 +/- 26 mg/24 h), hypoalbuminemia (2.1 +/- 0.12 vs. 2.8 +/- 0.02 g/dl), hypercholesterolemia (575 +/- 74 vs. 68 +/- 1.5 mg/dl) and elevated triglyceride levels (1,155 +/- 78 vs. 57 +/- 8 mg/dl). Glomerular azocaseinolytic activities both at pH 5.4 (-21%) and 7.4 (-37%) were significantly reduced. In contrast to human subjects, nephrotic rats that were treated with lovastatin displayed reduced triglyceride levels (767 +/- 134 mg/dl); their serum cholesterol, however, remained unchanged. In terms of glomerular proteolytic enzyme activities, the decline in azocaseinolysis at both pH values was, at least partly, prevented by lovastatin. On the basis of these data, it appears that the beneficial effect of lovastatin on the evolution of glomerulosclerosis in the nephrotic rat is associated with the conservation of glomerular proteolytic activities.
Albuminuria↗
Effect of beta 2-microglobulin on immunoglobulin production.
Chronic renal failure patients display high serum levels of beta 2-microglobulin (beta 2-M) and a pronounced defect in immunoglobulin production. In this light, the present study was conducted to investigate whether beta 2-M might influence the rate of antibody synthesis. Peripheral blood mononuclear cells (PBMC) from healthy subjects were cultured in the presence of beta 2-M (80 mg/l) for 7 days. Immunoglobulin concentrations were measured by ELISA-techniques in culture supernatants. Basal IgM levels were 390 +/- 10 ng/ml and increased to 940 +/- 216 ng/ml in the presence of beta 2-M. After PWM stimulation, IgM concentrations were 2654 +/- 614 ng/ml without and 3750 +/- 914 ng/ml with beta 2-M. IgG and IgA production by PBMCs was not influenced by beta 2-M in the culture medium. Likewise, the generation of beta 2-M by PBMCs was unchanged in the presence of exogenous beta 2-M in the medium. In terms of clinical relevance, serum beta 2-M levels of 28 uremic patients were correlated with capacity of their PBMCs for immunoglobulin production in vitro. However, there was no apparent correlation between beta 2-M serum levels and immunoglobulin synthesis in vitro. Taken together, beta 2-M seems to have a stimulatory effect on IgM synthesis in vitro. Whether this has some clinical meaning in patients with chronic renal failure remains to be investigated.
Adult↗
Intraglomerular proteinase activity in adriamycin-induced nephropathy.
Adriamycin (ADR)-induced nephropathy is characterized by focal and segmental glomerulosclerosis and is supposed to be an ideal model of chronic progressive renal disease. The aim of our study was to investigate whether there might be an altered activity of glomerular proteinases in ADR nephropathy, thereby aggravating glomerular protein accumulation as an important initiating hallmark of glomerulosclerosis. In fact, we could demonstrate significantly enhanced levels of intraglomerular protein and DNA content in the experimental animals at week 7, 12 and 22 after administration of ADR. When relating intraglomerular proteinase activity, which was measured in ultrasonically destroyed isolated glomeruli, obtained by differential sieving techniques, to the intraglomerular protein and DNA content, this enzyme activity was significantly reduced throughout the observation period. Based on these data, we suggest that this relatively decreased proteinase activity in glomeruli exposed to ADR might play a pathogenetic role in the development of glomerular hypertrophy, an important harbinger of glomerulosclerosis.
Animals↗
Effect of disease on glomerular proteinases.
Up to now, little is known about the self-perpetuating mechanism leading to terminal renal failure in chronic renal disease. The common pathological feature of progressive renal insufficiency is focal and segmental glomerulosclerosis. The experimental counterpart of this process is represented for instance by the models of streptozotocin diabetes, Adriamycin nephropathy and Goldblatt hypertension. In fact, the main initiating hallmark of glomerulosclerosis is an accumulation of glomerular proteins, whose balance is apparently influenced by the activity of glomerular proteinases. In isolated glomeruli of kidneys from the experimental animals, the total proteinase activity was assayed with the unspecific but sensitive azocasein assay. In fact, the activity was significantly reduced in all experimental models at acid and neutral pH when relating enzyme activity to the glomerular protein and DNA content. We believe, that our data of reduced glomerular proteinase activity in the animal models of glomerulosclerosis represent perhaps a new additional common pathogenetic mechanism. The glomerular protein accumulation could be a result of a synergistical interaction between hemodynamic factors and biochemical ones; the latter, we suggest to be a decrease of glomerular proteinase activity.
Animals↗
Fibronectin metabolism in isolated glomeruli from obese Zucker rats.
The obese Zucker rat develops non-immune-mediated spontaneous focal glomerulosclerosis. Mesangial matrix expansion is an important initiating hallmark of such glomerular damage and fibronectin is a normal constituent of mesangial extracellular matrix. Using a quantitative method based on enzyme immunoassay, we have assessed the intraglomerular fibronectin content and its degradation in obese Zucker rats and their lean littermates. In the obese Zucker rats the glomerular fibronectin content was significantly higher than in the control animals. Furthermore, proteinase activity against fibronectin was significantly reduced in the glomeruli of obese Zucker rats compared to the control animals. These data demonstrate that in obese Zucker rats there is a glomerular accumulation of fibronectin which we propose is at least partly due to diminished proteolytic digestion. We speculate that this result might indicate a possible mediator of progressive glomerulosclerosis in this animal model.
Animals↗
Effect of renal disease on glomerular proteinases.
Until now, little is known about the self-perpetuating mechanism leading to terminal renal failure in chronic renal disease. The common pathological feature of progressive renal insufficiency is focal and segmental glomerulosclerosis. The experimental counterpart of this process is represented by models of streptozotocin diabetes, Adriamycin nephropathy and Goldblatt hypertension. The main initiating hallmark of glomerulosclerosis is an accumulation of glomerular proteins, whose balance is apparently influenced by the activity of glomerular proteinases. In isolated glomeruli of kidneys from experimental animals, total proteinase activity was assayed with an unspecific but sensitive azocasein assay. The activity was significantly reduced in all experimental models at acid and neutral pH when relating enzyme activity to the glomerular protein and DNA content. The demonstration of reduced glomerular proteinase activity in the animal models of glomerulosclerosis could represent a new additional common pathogenetic mechanism. Glomerular protein accumulation could be a result of a synergistic interaction between hemodynamic and biochemical factors; we suggest the latter to be a decrease in glomerular proteinase activity.
Animals↗
Role of glomerular proteinases in the evolution of glomerulosclerosis.
Recent studies suggest that proteolytic enzymes located within the glomerulus are involved in the degradation of extracellular matrix components. In the present investigation glomerular proteinase activities were followed in a variety of non-immune-mediated renal diseases as well as during different dietary manipulations. Azocaseinolysis was significantly reduced in the obese Zucker rat compared with lean littermates (pH 5.4:8.9 +/- 0.4 vs 11.4 +/- 0.7; pH 7.4:5.8 +/- 0.7 vs 9.3 +/- 0.6 arb. U/mg protein). When the glomerular proteolytic capacity was measured in old rats, again a significant decline in proteolysis was observed (pH 5.4:9.8 +/- 0.8 vs 17.7 +/- 0.8; pH 7.4:6.4 +/- 0.7 vs 11.7 +/- 0.5 arb. U/mg protein). In Goldblatt hypertensive rats the unclipped kidney, which is exposed to high blood pressure, revealed lower glomerular azocaseinolytic activity compared with the contralateral clipped kidney (pH 5.4:8.1 +/- 0.4 vs 12.9 +/- 0.5 arb. U/mg protein). In parallel, the cathepsin B content was also diminished in glomeruli from kidneys exposed to hypertension. When proteinases were followed in glomeruli from intact kidneys of rats fed protein-modified diets (fraction of casein 0.05, 0.20 or 0.60) a significant fall in the activities of cysteine proteinases, e.g. cathepsin B (casein 0.05:1,498 +/- 110 vs casein 0.60:914 +/- 84 microU/micrograms DNA), as well as metalloproteinases, e.g. collagenase (casein 0.05:233 +/- 14 vs casein 0.60:137 +/- 11 microU/micrograms DNA), occurred. These data indicate that in both early and late stages of glomerulosclerosis, proteolytic activities within the glomerulus tend to be reduced, which could allow extracellular matrix accumulation. Moreover, changes in dietary protein intake resulted in profound alterations of glomerular proteinases.(ABSTRACT TRUNCATED AT 250 WORDS)
Aging↗
Improved immunoglobulin production in dialysis patients treated with recombinant erythropoietin.
Improvements in B lymphocyte function have been reported in hemodialysis patients receiving erythropoietin. The present investigation studied whether erythropoietin interferes with B cell function and the mechanisms of this effect. Antibody production by cultured peripheral blood mononuclear cells (PBMC) (7 days) from 15 dialysis patients before and during erythropoietin treatment and from 14 healthy controls was followed. IgG and IgA were formed less in the uremic group than in healthy subjects. After 8 weeks of erythropoietin (hematocrit rose from 19 to 31%) basal IgG formation by PBMC rose from 304 +/- 83 to 566 +/- 49 ng/ml (p less than 0.02), while IgA production rose from 380 +/- 121 to 563 +/- 362 ng/ml (p less than 0.01). IgM production, which appeared to be normal in uremia, remained unchanged during erythropoietin treatment. Production of IgG and IgA stimulated by pokeweed-mitogen was subnormal in uremia, but improved under erythropoietin therapy. To establish whether erythropoietin acted by itself or through correction of the renal anemia, healthy PBMC were directly incubated with 2 U/ml of erythropoietin. Under these conditions production of IgG (+19%), IgA (+28%), and IgM (+32%) was enhanced. Taken together these data indicate a direct stimulant effect of erythropoietin on B lymphocytes in end-stage renal failure.
Anemia↗
Intraglomerular fibronectin accumulation and degradation in obese Zucker rats.
The obese Zucker rat is a classic model of non-immune mediated spontaneous focal glomerulosclerosis. An important initiating hallmark of glomerulosclerosis in this model is mesangial matrix expansion. Fibronectin, a highly biologically active glycoprotein, is a normal constituent of mesangial extracellular matrix. Using a quantitative method based on enzyme immunoassay we assessed the intraglomerular fibronectin content and its degradation in obese Zucker rats and their lean littermates. In the obese Zucker rats the glomerular fibronectin content was significantly higher in comparison to the controls (88 +/- 6 vs 48 +/- 4 ng/10(3) glomeruli). Furthermore, proteinase activity against fibronectin was significantly reduced in the glomeruli of obese Zucker rats when compared to control animals (at pH 5.4: 186 +/- 6 U/mg protein vs 286 +/- 14 U/mg protein, at pH 7.4: 152 +/- 12 U/mg protein vs 193 +/- 12 U/mg protein). These data demonstrate that in obese Zucker rats there is a glomerular accumulation of fibronectin which we propose is at least partly due to diminished proteolytic digestion. Whether accumulation of intraglomerular fibronectin contributes to progressive glomerulosclerosis remains a matter of debate.
Animals↗
Obese Zucker rat: potential role of intraglomerular proteolytic enzymes in the development of glomerulosclerosis.
The obese Zucker rat is a classic model of non-immune-mediated spontaneous focal glomerulosclerosis. An early morphological hallmark of glomerular damage in the obese Zucker rat is a mesangial expansion, which precedes and mediates the development of glomerular damage in these animals. This study was designed to investigate whether there might be a reduced activity of glomerular proteinases in kidneys of obese Zucker rats, thereby being involved in the pathogenesis of mesangial expansion, which is mainly due to protein overloading. In fact, we found a decreased proteinase activity in ultrasonically destroyed isolated glomeruli obtained by a differential sieving technique in obese Zucker rats compared with their lean littermates. This held true at acid as well as at neutral pH and could be confirmed when proteinase activity was related to DNA instead of protein. When investigating the glomerular cathepsin B content--this is a lysosomal enzyme with acid pH optimum, which is involved in the degradation of glomerular structural as well as filtered plasma proteins--we found a significantly increased level in the kidneys of obese Zucker rats. Hence, the intraglomerular proteinase activity is reduced in the face of enhanced glomerular content of at least lysosomal proteinases. The underlying reason for this depressed activity remains to be established. We propose that reduced activities of intraglomerular proteinases may be important in the pathogenesis of mesangial matrix expansion in obese Zucker rats, an important initiating hallmark of glomerulosclerosis in this model.
Animals↗
Proteinase activity in isolated glomeruli of Goldblatt hypertensive rats.
In Goldblatt rats, the kidney exposed to high blood pressure reveals glomerulosclerosis. Moreover, in preexisting parenchymal renal disease, the development of glomerulosclerosis is accelerated in the unclipped kidney. Up to now, the pathogenetic mechanism underlying the development of glomerulosclerosis due to systemic hypertension has not completely been resolved. Traditionally, hemodynamic mechanisms have been discussed. This study was performed to investigate whether there might be a decreased activity of glomerular proteinases in the unclipped kidney of Goldblatt rats as a potential pathogenetic factor for glomerulosclerosis. 20 weeks after the surgical intervention, we found a reduced proteinase activity in ultrasonically destroyed isolated glomeruli obtained by differential sieving technique in comparison with the contralateral clipped kidney and the kidneys of sham-operated normotensive controls. This could be confirmed, when proteinase activity was related to DNA instead of protein. When investigating glomerular cathepsin B-content, a lysosomal enzyme, which is able to degrade glomerular structural as well as non-structural proteins, we found a decreased level in the kidney of Goldblatt rats exposed to systemic hypertension in comparison with normotensive control animals. Basing on these results we presume that glomerular protein accumulation and concomitant glomerulosclerosis due to systemic hypertension might be a result of a synergistical interaction between hemodynamic factors and biochemical ones; we suggest one of the latter to be a decreased glomerular proteinase activity.
Animals↗
Dialysis membranes decrease immunoglobulin and interleukin-6 production by peripheral blood mononuclear cells in vitro.
In order to determine the influence of dialysis membranes on immunoglobulin (Ig) and interleukin-6 (IL-6) production, peripheral blood mononuclear cells (PBMC) from 11 haemodialysis patients were cultured for 7 days on Cuprophan, Hemophan, and polyacrylonitrile flat-sheet dialysis membranes. IL-6, IgG, IgA, and IgM were assayed in the supernatants using ELISA. Pokeweed-mitogen-stimulated IgG production declined significantly from 319 +/- 40 ng/ml on polystyrole to 162 +/- 26 ng/ml on Cuprophan, 135 +/- 25 ng/ml on Hemophan, and 109 +/- 20 ng/ml on polyacrylonitrile. A similar pattern was observed for IgA production by PBMC. In comparison to polystyrole (724 +/- 34 pg/ml), IL-6 production by PBMC was significantly reduced in the presence of Cuprophan (151 +/- 45 pg/ml), Hemophan (167 +/- 6 pg/ml) and polyacrylonitrile (108 +/- 33 pg/ml). The fact that the level of monocyte-derived IL-6, a stimulator of B cells, was decreased suggests that reduced B cell activity may be due to diminished stimulation by monocytes.
B-Lymphocytes↗
Suppression of beta 2-microglobulin release from lymphocytes by dialysis membranes.
As lymphocytes are one of the main sources of circulating beta 2-microglobulin (beta 2M), the direct effect of different dialysis membranes on beta 2M release from those cells was studied in vitro. Lymphocytes were isolated from 11 long-term haemodialysis patients and nine healthy controls. Cells were cultured on flat sheet membranes made from either Cuprophan, Hemophan, or polyacrylonitrile. Polystyrole petri dishes were used as controls. Beta 2M concentrations in the supernatant were measured after 3 and 7 days of culture by ELISA techniques. Beta 2M release from lymphocytes obtained from uraemic patients was almost identical to the release from healthy subjects. In the presence of all three membranes the release of beta 2M was less than that produced on polystyrole. This held true for lymphocytes isolated from both healthy and uraemic subjects. As for the three membranes the release of beta 2M into the supernatants was statistically the same when the adsorptive capacity of polyacrylonitrile was taken into account. However, there was a tendency for Cuprophan to exert the strongest inhibition, while Hemophan and polyacrylonitrile reduced beta 2M release to a lesser degree. Based on these data it seems that prolonged interaction between dialysis membranes and lymphocytes does lead to a reduction in beta 2M release.
Adult↗
Cytokine production by monocytes during haemodialysis.
In order to follow the effect of haemodialysis on monocyte function, we measured the release of interleukin-1 beta (Il-1), interleukin-6 (Il-6), and tumour necrosis factor alpha (TNF alpha) from cultured monocytes isolated before and after dialysis. Monocytes obtained from patients before dialysis released smaller amounts of cytokines than cells from healthy controls. The choice of the dialysis membrane had no effect on predialytic monocyte activity. Basal cytokine release after dialysis remained virtually unchanged, irrespective of the membrane material used. When stimulated with LPS, cells significantly produced more cytokines than under basal conditions. Stimulated monocytes isolated before dialysis produced considerably more cytokines than cells obtained at the end of the dialysis. Taken together, uraemia by itself seemed to depress monocyte activity. Haemodialysis either with cuprophan or PMMA dialysers had no influence on basal cytokine release during a 24-h period following dialysis. Uraemic monocytes, however, appeared to be primed, since stimulation with LPS in vitro caused a more pronounced release of cytokines than in healthy volunteers.
Aged↗
Dialysis membranes inhibit in vitro release of beta-2-microglobulin from human lymphocytes.
In the present study the effect of different dialysis membrane materials on in vitro beta 2-microglobulin (beta 2M) release by human lymphocytes was investigated. Lymphocytes were isolated from 11 long-term haemodialysis patients and 9 healthy controls. Cells were cultured either on flat sheet membranes made from Cuprophan, Hemophan and polyacrylonitrile or on polystyrol. beta 2M concentrations in the supernatant were measured at 3 and 7 days of culture, respectively. The beta 2M release from lymphocytes obtained from uraemic patients was almost identical with the release from healthy subjects. In the presence of all three membranes the release of beta 2M was less of what was produced on polystyrol. This held true for lymphocytes isolated from both healthy and uraemic subjects. As for the three membrane materials, the release of beta 2M into the supernatants was statistically not different when the adsorptive capacity of polyacrylonitrile was taken into account. However, there was a tendency for Cuprophan to exert the strongest inhibition, while Hemophan and polyacrylonitrile reduced beta 2M release to a lesser degree. Based on these data it seems that the increase in serum beta 2M which has been observed during dialysis with Cuprophan membranes is not caused by direct interaction of lymphocytes with Cuprophan membranes.
Acrylic Resins↗