Urine of patients with nephrotic syndrome contains the plasma type of PAF-acetylhydrolase associated with lipoproteins.

BACKGROUND Platelet-activating factor (PAF) is a proinflammatory phospholipid mediator involved in the pathogenesis of glomerulonephritis (GN). In plasma, PAF is hydrolyzed and inactivated by PAF-acetylhydrolase (PAF-AH), an enzyme associated with lipoproteins, mainly with the low-density lipoprotein. PAF-AH activity has been found in urine of patients with primary GN, however the source and type of urinary PAF-AH remain unknown. We characterized the type of PAF-AH excreted in the urine of patients with primary GN and studied the possible relationship of this enzyme with the lipiduria and proteinuria observed in these patients. METHODS Eighteen patients with primary GN (8 with nephrotic syndrome (NS) and 10 with non-nephrotic range proteinuria (NNRP)) and 20 normolipidemic age- and sex-matched controls participated in the study. PAF-AH activity in plasma, in urine and in individual lipoprotein particles was determined by the trichloroacetic acid precipitation procedure, whereas the PAF-AH protein was detected by Western blotting analysis. Plasma and urine lipoproteins were fractionated by gradient ultracentrifugation and characterized by Western blotting analysis. RESULTS Plasma PAF-AH activity was higher in NS patients compared with NNRP patients and controls, whereas the enzyme activity associated with high-density lipoprotein was significantly lower in both patient groups compared with controls. PAF-AH was detected only in the urine of NS patients. It was the plasma type of PAF-AH and was associated with lipoprotein particles. Enzyme activity was also positively correlated with urine cholesterol levels. CONCLUSION Urine of NS patients contains the plasma type of PAF-AH, which is related to the extent of lipiduria and is associated with urine lipoproteins.