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P Vogeleere

Publications and source records attributed to P Vogeleere.

11 recordsLinked to original sources
PubMed1999

Study by means of high-performance liquid chromatography of solutes that decrease theophylline/protein binding in the serum of uremic patients.

Substantial changes in protein binding of drugs occur during the progression of renal insufficiency. Protein-bound uremic solutes play a role in the inhibition of drug protein binding. We previously demonstrated that hippuric acid in uremic ultrafiltrate was an inhibitor of the theophylline protein binding. The present study was undertaken to extend the yield of protein-bound uremic solutes by displacing ligands in uremic serum from their binding sites by five deproteinization methods. The inhibitory effect on theophylline protein binding of the deproteinized uremic serum was higher than with ultrafiltrate (p < 0.05). The influence of 30 semi-preparative HPLC fractions from deproteinized uremic serum on the theophylline protein binding was evaluated to identify the responsible compounds and to compare their relative individual impact. The theophylline protein binding was calculated as a percentage (bound versus total). The most important decrease of the protein binding was observed in HPLC fractions 6, 10 to 13, 15 and 28 with protein binding of: 61.5 +/- 10.8, 64.5 +/- 7.6, 60.9 +/- 10.1, 47.5 +/- 3.3, 60.0 +/- 6.7, 60.7 +/- 6.3 and 61.3 +/- 6.9%, respectively versus 69.1 +/- 2.4% for control serum (p < 0.05). The responsible compounds were characterized in the fractions by co-elution: 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), indole-3-acetic acid, indoxyl sulfate, hippuric acid, p-hydroxyhippuric acid and tryptophan. Their concentration was determined by analytical HPLC and a solution containing these compounds at the same concentration as in deproteinized uremic serum was composed. This solution was added to control serum and decreased the theophylline protein binding from 69.0 +/- 4.4% to 61.3 +/- 1.3%, which was less important than in genuine uremic serum (44.4 +/- 3.8%, p < 0.05). Dose-response curves with the characterized compounds revealed that the most important role in binding inhibition could be attributed to hippuric acid and CMPF. Our data suggests that the yield of protein binding inhibiting compounds is more important with deproteinized uremic serum than with uremic ultrafiltrate. The identified uremic compounds are not entirely representative for the decreased protein binding of theophylline, indicating that additional factors than those identified in this study affect the protein binding as well.

Blood Proteins↗
PubMed1998

Inhibition of calcitriol-induced monocyte CD14 expression by uremic toxins: role of purines.

End-stage renal disease is associated with a defect in immunologic functions. Previous studies have demonstrated that uremic ultrafiltrate (UUF) contains factors that suppress calcitriol synthesis and its biological actions. In the present study, the effect of UUF on basal and calcitriol-induced membrane bound CD14 expression of monocytes activated by phorbol 12-myristate 13-acetate was evaluated. CD14 acts as a receptor for the complexes of lipopolysaccharide and lipopolysaccharide-binding protein. Monocytes isolated from normal donors were used for the assay of monocyte CD14 expression. A calcitriol induced rise in monocyte CD14 expression (1966+/-423 to 2421+/-436 fluorescence intensity) was found. However, UUF not only suppressed basal CD14 expression of monocytes (from 1966+/-423 to 1240+/-203, P < 0.05) but also significantly blunted calcitriol-induced CD14 expression (from 2421+/-436 to 1744+/-229, P < 0.05). HPLC fractionated UUF collected from 8 to 16 min (fraction 1, F1) and from 25 to 40 min (fraction 3, F3) also significantly suppressed the expression of CD14. Because purine derivatives coeluted within F1, their effect on monocyte CD14 expression was also tested. Uric acid, xanthine, and hypoxanthine was found to suppress basal as well as calcitriol-induced CD14 expression of monocytes in a dose-dependent manner. In conclusion, UUF contains factors that impair calcitriol activated function of monocytes.

Calcitriol↗
PubMed1997

HPLC fractions of human uremic plasma inhibit the RBC membrane calcium pump.

We have reported that uremic plasma filtrates (UF) inhibit the red blood cell (RBC) membrane calcium pump. The inhibitor was dialyzable, smaller than 3,000 molecular weight, heat-stable, and protease-resistant. In the present study, we used reverse-phase preparative HPLC, analytical HPLC, and Sephadex G-25 elution to identify inhibitory fractions. Inhibition was confirmed in three different bioassays: (1) Sr2+ efflux in intact RBC, the primary bio-assay; (2) 45Ca efflux in intact RBC; and (3) calcium ATPase activity in isolated RBC membranes. Active fractions were analyzed by mass spectrometry, capillary electrophoresis, enzymatic analysis, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. These demonstrated a number of compounds, including: sugars, polyols, osmolytes like betaine and myoinositol, amino acids, and other metabolites, such as 3-D-hydroxybutyrate, dimethylglycine, trimethylamine-N-oxide, guanidinoacetic acid and glycine. Many individual compounds were then tested for an effect on the calcium pump. Thus, HPLC was able to separate a substantial number of compounds in inhibitory fractions. Efforts are under way for precise identification of the inhibitor, to advance our understanding of uremic toxicity and/or hypertension in CRF.

Adult↗
PubMed1997

P-Cresol, a uremic compound, enhances the uptake of aluminum in hepatocytes.

In the end-stage renal disease patient, certain uremic compounds could influence the cellular accumulation of aluminum (Al). In this study, we examined the effect of 15 uremic ultrafiltrate fractions obtained by HPLC on the uptake and toxicity of Al in mouse hepatocytes (MH) in culture, a model system in which Al is taken up bound to transferrin (Tf). Uremic fractions 4 to 8, 12, 14, and 15 increased cellular Al uptake and aspartate aminotransferase release and decreased cell growth when Tf-Al, not Al citrate, was added to culture media. Compounds that have been extracted previously from these ultrafiltrate fractions (p-cresol, xanthine, tryptophan, hippuric acid, and o-hydroxyhippuric acid) were then tested for their effect on Al uptake and toxicity in MH at concentrations found in uremic serum. Significant Al uptake by MH was observed only when p-cresol was added together with Tf-Al. Time-response curves showed increased Al uptake and toxicity at p-cresol concentrations of 3 mg/dl in culture media. Dose-response curves confirmed that Al uptake and cell toxicity were proportional to p-cresol from 1.5 mg/dl to 3 mg/dl in culture media. p-Cresol was not toxic to MH in the absence of Tf-Al in media. p-Cresol increased Tf-associated Al uptake only because there was no effect on Al uptake when Al citrate was substituted, and studies with Tf-I125-Al in the presence of this compound showed increased Tf-I125 taken up by MH. p-Cresol did not increase Tf saturation with Al. p-Cresol also increased Tf-Al uptake in Friend erythroleukemia and neuroblastoma cells in culture. Our studies suggest that p-cresol and uremic fractions 4 to 8, 12, 14, and 15 increase the uptake and toxicity of Al in cultured MH. These compounds may play a role in the accumulation and toxicity of Al in the liver of end-stage renal disease patients and possibly in all cells that express Tf receptors.

Aluminum↗
PubMed1996

Disturbed host defense in peritoneal cavity during CAPD: characterization of responsible factors in dwell fluid.

In this study, the factors in overnight dwell fluid (8 to 10 hr dwell) depressing granulocyte (GC) NAD(P)H-oxidase dependent radical species production are characterized. At present, most studies have essentially focused on fresh, unspent dialysate and on peritoneal macrophages. The response to Staphylococcus aureus (Staph A) was dose-dependently depressed for both GC CO2 production (from 91.3 +/- 8.4 to 9.0 +/- 1.5 dpm/10(3) GC, P < 0.01) and chemiluminescence (CL) (peak from 7.3 +/- 0.8 to 1.6 +/- 0.8 cps x 10(3)/GC, P < 0.01). Stimulation with formyl-methionine-leucine-phenylalanine (f-MLP), phorbol myristic acid (PMA), Staphylococcus epidermidis (Staph Epi), E. coli, latex and zymosan revealed a parallel depression, pointing to an intrinsic metabolic defect, rather than failure of particle ingestion. The addition of glucose to the normal cell medium to obtain the same concentration as in the CAPD effluent (2.9 +/- 0.3 mg/dl) depressed function but not to the same extent as the genuine PD effluent. Opsonization of Staph A and E. coli induced a partial correction. No effect of pH or osmolality was observed. HPLC fractionation of CAPD effluent on a polarity based gradient revealed an elution of depressive factors in hydrophobic fractions with a nadir in F7 and F12. Analysis of the elution pattern of various uremic solutes revealed elution in F12 of p-cresol, a solute with known inhibitory effect on GC function. These events may be related to recent peritonitis (CL in response to Staph A 0.3 +/- 0.1 in effluent of 6 patients with recent peritonitis versus 2.6 +/- 0.8 cps x 10(3)/GC in 12 patients without recent peritonitis (P < 0.01). We conclude that the GC response is depressed in the presence of CAPD effluent due to excess glucose, lack of opsonization, and uremic solutes of which p-cresol is one of the responsible compounds.

Ascitic Fluid↗
PubMed1995

Mechanisms of uremic inhibition of phagocyte reactive species production: characterization of the role of p-cresol.

It is generally recognized that the uremic syndrome results in a depression of immune function, but the uremic solutes responsible remain largely unidentified. In this study, the effect of 18 known uremic retention solutes, including urea and creatinine, on hexose monophosphate shunt (HMS)-dependent glucose-1-C14 utilization (G1C-U), chemiluminescence production (CL-P) and flow cytometric parameters (FCP) of respiratory burst and phagocytosis were evaluated in granulocytes and/or monocytes. Among the compounds studied, only p-cresol depressed whole blood respiratory burst reactivity (G1C-U, CL-P) dose dependently at concentrations currently encountered in end-stage renal disease (ESRD) (P < 0.05 from 5 micrograms/ml on). The effect of p-cresol was enhanced by increasing incubation times from 10 to 120 minutes. HMS activity of isolated packed erythrocytes remained unaffected. FCP of respiratory burst activity (Bursttest, expressed as log fluorescence units, LFU) revealed a marked depression in the presence of p-cresol (from 700 +/- 167 to 291 +/- 128 LFU for granulocytes, from 278 +/- 102 to 146 +/- 52 LFU for monocytes, P < 0.01), whereas particle ingestion (Phagotest) remained unaffected. Cell-free myeloperoxidase activity was also markedly depressed in the presence of p-cresol. Polarity based HPLC-elution of a standard solution containing all the solutes studied, using a gradient from 100% formic acid to 100% methanol during 60 minutes, revealed elution of p-cresol after 46.6 minutes, pointing to its relative hydrophobicity. Conjugation of p-cresol to p-cresylsulfate anihilated the depressive effect of p-cresol on granulocyte function, and at the same time caused a shift in HPLC-elution pattern to a less lipophilic range.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1995

Middle molecules: toxicity and removal by hemodialysis and related strategies.

Renal failure results in the retention of metabolites which may arbitrarily be grouped according to their molecular weight: low (< 300 daltons molecular weight), middle (300-15,000 daltons), and high (> 15,000 daltons). Opinion in respect to the relative importance of these groups varies. Initially it was thought that small molecules were important. In the mid-1970s, investigators identified the possible pathophysiological role of middle molecules. However, since positive identification of such molecules was difficult, opinion has shifted back in favor of small molecules, and little attention, with the exception of beta 2 microglobulin, has been paid to middle molecules and their removal by hemodialysis and related therapies. In this review current knowledge regarding middle molecules identified as uremic toxins and their removal by hemodialysis and associated therapies are discussed.

Ascorbic Acid↗
PubMed1994

Uraemic toxic retention solutes depress polymorphonuclear response to phagocytosis.

Previous studies from our laboratory have demonstrated that the activity of the hexose monophosphate shunt (HMS) pathway in phagocytosis-related respiratory burst is disturbed in end-stage renal disease. To determine whether uraemic solute retention is responsible for this defect the HMS-path was evaluated by measurements of glucose-1-C14 utilization and determination of 14CO2 production in polymorphonuclear cells (PMNLs), suspended in normal plasma or uraemic biological fluids. Normal PMNLs, while suspended in normal or uraemic plasma, were stimulated with either latex, zymosan or Staph. aureus; CO2 generation (measured as DPM/10(3) PMNL, normal versus uraemic plasma) was depressed in uraemic plasma in response to latex (from 43 +/- 5 to 20 +/- 3), zymosan (from 72 +/- 8 to 47 +/- 4) (P < 0.01), and Staph aureus (from 73 +/- 17 to 47 +/- 8 DPM/10(3) PMNL) (P < 0.05). The degree of inhibition was similar for each stimulus. To characterize the substances responsible for this defect we fractionated uraemic plasma ultrafiltrate by polarity-based semipreparative C18 reversed phase HPLC and found a decreased response to Staph. aureus in the presence of fraction 2 (from 102 +/- 13 to 23 +/- 10 DPM/10(3) PMNL, P < 0.05), and in fractions 8 and 11 (lowest value in fraction 8, 54 +/- 14 DPM/10(3) PMNL, P < 0.05 versus control). The pattern of HPLC elution on a gradient from 100% formiate (pH 4.0) to 100% methanol indicates that there are at least two chemically distinguishable groups of compounds, one hydrophilic (in fraction 2), and one lipophilic (in fractions 8 and 11). We conclude that uraemic biological fluids contain factors that inhibit HMS activity related to phagocytosis, and that at least two groups of components with different characteristics are involved.

Adult↗