Cold ischemia in the absence of alloreactivity induces chronic transplant nephropathy through a process mediated by the platelet-activating factor.

BACKGROUND: Ischemia-reperfusion injury is considered a risk factor for the development of chronic transplant nephropathy (CTN) although the mechanisms that mediate its effects have not been completely established. We have previously shown that treatment with a platelet-activating factor (PAF) receptor antagonist (UR12670) protected kidneys from the progression to chronic nephropathy induced by warm ischemia. Here we examine the contribution of cold ischemia to the development of late functional and structural kidney changes in rats subjected to syngeneic renal transplantation and the role of PAF in this chronic nephropathy. SUBJECTS AND METHODS: Lewis rats were used as kidney donors and recipients, which were transplanted either immediately or after a cold ischemia period of 5 hr. Contralateral nephrectomy was performed on the seventh day after transplantation. Cyclosporine was administered for 15 days after transplantation. Groups were as follows: Sy, immediate transplantation; SyI, transplantation after 5 hr of cold ischemia; SyIUr, transplantation after 5 hr of cold ischemia plus UR12670 from the transplantation day to the end of the study, at 24 weeks. Serum creatinine, creatinine clearance, and proteinuria were determined every 4 weeks. Urinary

Urinary platelet-activating factor excretion is elevated in non-insulin dependent diabetes mellitus.

Proteinuria is currently considered a very sensitive predictor of diabetic nephropathy, but 20-25% of all diabetic patients with negative Albustix reaction excrete higher than normal (< 20 mg/24 h) amounts of albumin in their urine. It is our hypothesis that platelet-activating factor (PAF), a potent glycerophospholipid that acts as a chemical mediator for a wide spectrum of biological activities, including increased vascular permeability, may be produced in significant amounts during periods preceding microalbuminuria. In this study, we compared urinary PAF excretion in Mexican-American subjects who were diagnosed with non-insulin dependent diabetes mellitus (NIDDM) with their healthy control counterparts. The age of the NIDDM subjects (45.9 +/- 2.1 years) was not significantly different from the healthy control group, which was 39.4 +/- 2.7 years (P < 0.0672). The NIDDM subjects (body mass index, 29.9 +/- 1.1 compared to 26.1 +/- 0.9 kg/m2 in healthy controls) were characterized by significantly increased (P < 0.05) fasting plasma glucose (192 +/- 11 vs. 97 +/- 4 mg/dl in healthy controls), fasting insulin (20.9 +/- 2.4 vs. 12.3 +/- 1.6 microU/ml), fasting C-peptide (2.93 +/- 1.26 vs. 1.48 +/- 0.51 ng/ml), and hemoglobin A1c (10.3 +/- 0.7 vs. 5.6 +/- 0.3%), respectively. The urine output for the NIDDM and control subjects were 1942 +/- 191 ml/24 h and 1032 +/- 94 ml/24 h, respectively, and urinary albumin excretion (UAE) rates were estimated to be 38 +/- 7 micrograms/min and 11 +/- 1 micrograms/min, respectively. The NIDDM subjects produced significantly increased levels of urinary PAF (2606.3 +/- 513.1 ng/24 h compared with 77.9 +/- 14.1 ng/24 h in controls (or 1706.3 +/- 420.8 ng/ml compared with 85.4 +/- 17.8 pg/ml of urine, in NIDDM and control subjects, respectively). We found that urinary PAF excretion was significantly correlated with microalbumin excretion (r = 0.7) especially at UAE rates greater than 30 mg/day and more importantly, some NIDDM patients with negative Albustix reaction (i.e. normal UAE) produced significantly more PAF, suggesting that PAF excretion may precede microalbuminuria and that subtle injury to the kidneys are present in NIDDM long before overt albuminuria ensues, urinary PAF measurements could potentially therefore serve as a sensitive indicator of renal injury in diabetes mellitus. These results lend further credence to our hypothesis that PAF may be the biochemical compound linking the various members of the insulin resistance syndrome.

Production of platelet-activating factor in patients with sepsis-associated acute renal failure.

BACKGROUND: Studies in experimental animals have suggested that platelet-activating factor (PAF) is a mediator of sepsis-associated acute renal failure (ARF). In the present study we have evaluated whether an increased concentration of PAF within circulation or urine of septic patients correlated with the worsening of renal function. METHODS: The concentration of PAF and selected cytokines (TNF, IL-1, IL-6, IL-8) was evaluated in blood and urine of 12 patients with septic shock and ARF for 4 consecutive days. RESULTS: The data obtained indicate that blood and urinary concentrations of PAF and of IL-1, IL-6 and IL-8 were significantly higher in septic patients than in controls subjects and in patients with chronic renal failure. The concentration of TNF was significantly increased only in urine. A significantly positive correlation was found among blood concentration of PAF and heart rate (r = 0.4193, P < 0.017), serum creatinine (r = 0.3671, P < 0.038), serum IL-6 (r = 0.5475, P < 0.005) and urine excretion of IL-8 (r = 0.3984, P < 0.044), whereas a negative correlation was present with the number of circulating platelets (r = -0.4285, P < 0.018). Moreover, a positive correlation among the concentration of PAF in urine and the serum concentration of IL-6 (r = 0.5654, P < 0.006) and urine excretion of IL-6 (r = 0.6589, P < 0.0008) and IL-8 (r = 0.6371, P < 0.0004) were found. CONCLUSIONS: These results demonstrate in humans during ARF associated with septic shock the production of PAF, a mediator that has been previously implicated in the pathogenesis of experimental endotoxin-induced shock and renal injury. The observation that blood and urinary concentrations of PAF correlated with some of the clinical and laboratory parameters related to the severity of ARF and sepsis suggests that PAF may contribute to the development of renal injury in septic patients.

Plasma and urinary platelet activating factor concentrations and leukotriene releasing activity of leukocytes in steroid sensitive nephrotic syndrome of childhood.

Platelet activating factor (PAF) is synthesized and secreted by glomerular mesangial and endothelial cells. It increases glomerular basement membrane permeability and induces proteinuria. Leukotrienes (LT) are mediators released by either leukocytes or glomerular cells under the PAF effect. The possible role of PAF in steroid sensitive nephrotic syndrome (SSNS) of childhood was studied in 8 children with SSNS in the acute stage, 5 children in remission and 8 healthy controls. The PAF concentrations in urine and plasma were determined. Leukocytes were stimulated in vitro and the LT release in response to stimulation was determined. The urinary and plasma concentrations of PAF were significantly higher in the acute phase than in remission and in control patients. Children with SSNS were found to have peripheral leukocytes with increased LT releasing activity in vitro. These results are in accordance with clinical and experimental observations indicating that PAF originates in the kidney and plays a role in normal kidney physiology. Urinary PAF concentrations may be related to proteinuria because they were strongly correlated in the present study. Elevated plasma PAF concentrations in the acute stage of SSNS could result from either its secretion from the circulating leukocytes or decreased acetyl hidrolase activity needed for its hydrolysis in plasma. The increased LT release in vitro suggests that these cells might have been activated by PAF secreted from glomeruli. It is proposed that PAF and different LT in systemic and glomerular circulation are important mediators in childhood SSNS.

Urinary excretion of platelet-activating factor in human and experimental nephrosis.

BACKGROUND: Platelet-activating factor (PAF) is a phospholipid that has been implicated in the pathogenesis of glomerulonephritis and can be synthesized by glomerular cells in response to different stimuli. PAF increases glomerular permeability to proteins and urinary PAF has been determined to be of renal origin. In order to assess whether urinary PAF can be found augmented in situations of glomerular damage without glomerular leukocyte infiltration, urinary PAF was quantified in human and experimental nephrosis. METHODS: Urinary PAF was quantified by platelet bioassay and glomerular PAF by incorporation of 3H-acetate into PAF. PAF was characterized by its behaviour on thin-layer chromatography and high performance liquid chromatography and the blockade of its bioactivity by receptor antagonists. RESULTS: Urinary PAF excretion was significantly higher in patients with active idiopathic nephrotic syndrome than in controls (5.8+/-1.5 versus 1.7+/-0.75 mg/24 h; P<0.05) and patients in remission (1.63+/-0.75 ng/24 h; P<0.02). In rats with nephrosis induced by puromycin aminonucleoside there was an early increase in urinary PAF excretion (138+/-19 versus 49+/-22 pg/24 h in controls; P<0.035) that coincided with the augmented glomerular PAF synthesis (67+/-3.4 versus 36+/-1.2 DPM/mg protein in controls; P<0.003). CONCLUSIONS: These results suggest that the synthesis of PAF in the kidney may be involved in the pathogenesis of the proteinuria in idiopathic nephrotic syndrome and that urinary PAF excretion may be a good marker of disease activity.

[Changes in urinary excretion of platelet activating factor and its significance in patients with primary nephrotic syndrome].

In order to explore the change of urinary excretion of platelet activating factor (PAF) and its significance in patients with primary nephrotic syndrome (PNS), we determined the urinary and plasma PAF in 12 cases of PNS, using platelet aggregation bioassay. The results showed that the level of urinary PAF was significantly higher in patients with PNS (n = 12) than in healthy controls (n = 10), but that of plasma PAF was comparable in patients with PNS and controls, suggesting that the excessive generation of PAF is confined to kidney. There was a significant positive correlation between urinary excretion of PAF and proteinuria (r = 0.73, P < 0.01). The results indicated that increased urinary excretion of PAF can serve as an indicator for augmentation of the permeability of glomerular basement membrane (GBM) in PNS.

A simple and precise method for the routine determination of platelet-activating factor in blood and urine.

A simple and precise method is described for the measurement of platelet-activating factor (PAF) in blood and urine. The method involves the isolation of PAF from blood samples by two successive steps. In the first step, blood proteins are precipitated with ethanol and the "free" PAF, i.e., the PAF which is extractable with ethanol, is recovered. In the second step, "bound" PAF, i.e., PAF not extractable with ethanol, is extracted from the protein precipitate with chloroform/methanol/water. The extraction of PAF from urine samples requires only the ethanol extraction step. "Free" and "bound" PAF are then each fractionated by silicic acid column chromatography, and the methanol/water eluent containing PAF is then further fractionated by high-performance liquid chromatography using an isocratic solvent system of acetonitrile/methanol/water. PAF is then quantitated by measuring its ability to induce platelet aggregation in an aggregometer. Application of the method to blood and urine samples from twenty-three healthy volunteers revealed PAF levels in blood of 140-480 pg/mL (630-254.4 pg "free" PAF/mL and 64-225.6 pg "bound" PAF/mL), and of 1.2-4.0 pg PAF/mL in urine. The method overcomes various technical problems and was shown to be very precise. It should prove useful for monitoring PAF levels in various disease conditions.

Urinary excretion of platelet activating factor in patients with immune-mediated glomerulonephritis.

We have investigated whether human immune-mediated glomerulonephritis is associated with changes in platelet activating factor (PAF) biosynthesis. Urinary PAF, taken as a marker of its renal synthesis, was significantly higher in patients with membranous nephropathy (N = 9) than in healthy controls (N = 8). This was not due to a lower degradation of PAF since urinary acetylhydrolase activity was comparable in patients and controls. A significant positive correlation between urinary excretion of PAF and proteinuria was observed. PAF generation was comparable in polymorphonuclear cells isolated from patients with membranous nephropathy and controls. PAF levels in blood from patients with membranous nephropathy were significantly lower than in controls, suggesting that the excessive generation of PAF is confined to the kidney. The results document that signs of renal disease activity in human membranous nephropathy are associated with an excessive renal synthesis of PAF.

Urinary excretion of platelet-activating factor in haemolytic uraemic syndrome.

Since some of the features of haemolytic uraemic syndrome (HUS), such as platelet activation and glomerular injury, could be brought about by platelet-activating factor (PAF), we have studied the urinary excretion of PAF in 10 children with HUS and in 10 healthy age-matched controls. Urinary PAF concentrations, measured by radioimmunoassay, were significantly higher in acute-phase HUS patients than in controls (mean 2.04 [SD 1.66] vs 0.72 [0.43] ng/mg creatinine, p less than 0.05) but were similar to those in controls in samples taken after recovery. High PAF concentrations during the acute phase of HUS may reflect platelet activation and glomerular injury; the lower values after recovery suggest that urinary PAF may be a marker of disease activity.

Presence of platelet-activating factor in pyuria in humans.

The relationship between the occurrence of platelet-activating factor (PAF) and neutrophils in urine from patients with urinary tract infection was examined. PAF was detected in human pyuria, when leukocyte levels reached at least 300 cells/microL (n = 45), but not in normal urine (n = 12). The amount of PAF found in pyuria, measured by platelet aggregation assay, was 0.01 to 13.3 pmol/mL. A close correlation was seen between the amount of PAF present and the number of urinary leukocytes (p less than 0.01, r = 0.70). The leukocytes in pyuria consisted almost entirely of neutrophils (96 +/- 4%, mean +/- S.D.). Our findings suggest that the occurrence of PAF is associated with the accumulation of neutrophils in urine.

Platelet-activating factor receptor blocking reduces proteinuria and improves survival in lupus autoimmune mice.

Platelet-activating factor (PAF) has been suggested recently to play an important role in immune glomerulonephritis, favoring the formation of immune deposits in glomeruli and contributing to the local inflammatory reaction. Here we sought to investigate whether urinary PAF excretion was modified in New Zealand Black x New Zealand White mice a model of genetically determined immune complex disease which mimics systemic lupus in humans and whether changes in PAF urinary excretion values correlated with the extent of proteinuria. To clarify the possible "in vivo" relevance of these findings we evaluated whether PAF receptor antagonist has any influence on the evolution of renal disease and survival of these mice. Our results showed that: 1) in lupus mice urinary PAF excretion increased progressively with age in New Zealand Black x White; 2) the increase in PAF excretion correlated with the severity of proteinuria; and 3) the chronic administration of a PAF receptor antagonist [L-659,989 [(+/- )-trans-2-(3-methoxy-5-methylsulfonyl-4-propoxyphenyl)-5- (3,4,5-trimethoxyphenyl)tetrahydrofuran]] starting from 26 weeks of age significantly delayed the onset of proteinuria and prolonged survival.

Increased urinary excretion of platelet activating factor in mice with lupus nephritis.

Platelet activating factor (PAF) is present in urine from humans and experimental animals in normal conditions. Very little is known about changes in PAF urinary excretion under pathologic conditions and no data are available about the origin of PAF in the urine. In the present study we explored the possibility that immunologic renal disease is associated with an increase in PAF urinary excretion using gas chromatography-mass spectrometry technique. To clarify the renal or extrarenal origin of urinary PAF we evaluated whether exogenously administered PAF (1-[1', 2'-3H]alkyl) is filtered through the glomerulus and excreted in the urine. The results show that: 1) urine from mice with lupus nephritis in the early phase of the disease contained amounts of PAF comparable to those excreted in normal mouse urine, 2) PAF levels increased when animals started to develop high grade proteinuria, 3) after intravenous injection of [3H] PAF in nephritic mice, a negligible amount of [3H] ether lipid, corresponding to [3H]1-alkyl -2-acyl-3-phosphocholine (alkyl-2-acyl-GPC), was recovered from the 24 h urine extract.

Renal metabolism and urinary excretion of platelet-activating factor in the rat.

The origin of platelet-activating factor (PAF) in the urine remains ill defined. The present study documents that [3H]PAF (3.5 mu Ci) injected into the renal artery of isolated control rat kidney preparations perfused at constant pressure with a cell-free medium containing 1% bovine serum albumin (BSA) was excreted in negligible amounts (0.034%) in the urine, whereas 6% was retained by the kidney. When kidneys were perfused with a BSA-free medium, 0.029 and 71% of the total radioactivity added to the perfusate was recovered in the urine and in the renal tissue, respectively. [3H]PAF urine excretion in proteinuric kidneys from adriamycin-treated rats was still negligible (0.015%). Analysis of the renal tissue-retained radioactivity in control and proteinuric kidneys perfused with 1% BSA indicated metabolism into long chain acyl-sn-glycero-3-phosphorylcholine species, lyso-PAF, glycerols, and intact PAF. Thin layer chromatography analysis of [3H]glycerol fraction in these renal extracts showed two major components comigrating with 1-O-alkylglycerol and 1-O-alkyl-2-fatty acylglycerol. Isolated proximal tubules, but not glomeruli from nephrotic rats exposed to increasing concentrations of BSA (0-4%), had a higher PAF uptake than control tubules for BSA concentrations ranging from 0 to 0.1%. Our findings in the isolated perfused kidneys indicate that, in normal conditions, circulating PAF is excreted in the urine in negligible amounts and that the altered glomerular permeability to proteins does not affect this excretion rate. Moreover, analysis of renal tissue radioactivity documented that the renal metabolism of PAF is comparable in control and nephrotic kidneys.

Development of a mass spectrometric method to quantitate platelet activating factor in mouse urine.

Platelet activating factor (PAF) is a lipid mediator of inflammation released by a variety of stimulated inflammatory cells. It may be involved in immune glomerulonephritis. Thus, its measurement in urine could give information on the mechanism of this disease. We present here a method to measure PAF in mouse urine, using gas-liquid chromatography-mass spectrometry (GLC-MS) in the selected ion recording (SIR) mode. Before instrumental analysis, the extracted and purified samples were hydrolyzed and derivatized with pentafluorobenzoyl chloride. Different experimental conditions are presented and discussed to corroborate the analytical findings. PAF levels in mouse urine were 2.08 +/- 0.46 ng/24 h. This procedure might represent a new experimental tool to establish the possible role of PAF as mediator of tissue damage in renal disease.

Identification of phospholipid platelet-activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in human amniotic fluid and urine.

Human amniotic fluid and fetal urine were examined for the presence of phospholipid platelet-activating factor (PAF). PAF was detected in lipid extracts of some samples of amniotic fluid obtained from women in labor but it was undetectable in samples of amniotic fluid obtained before the onset of labor. PAF was identified by chromatographic mobility, platelet aggregation and chemical modifications. LysoPAF was also present in amniotic fluid at higher concentrations than those of PAF. Both PAF and lysoPAF were identified also in newborn and adult urine.