title: Aberrant glomerular filtration of urokinase-type plasminogen activator in nephrotic syndrome leads to amiloride-sensitive plasminogen activation in urine.
abstract: In nephrotic syndrome, aberrant glomerular filtration of plasminogen and conversion to active plasmin in preurine are thought to activate proteolytically epithelial sodium channel (ENaC) and contribute to sodium retention and edema. The ENaC blocker amiloride is an off-target inhibitor of urokinase-type plasminogen activator (uPA) in vitro. It was hypothesized that uPA is abnormally filtered to preurine and is inhibited in urine by amiloride in nephrotic syndrome. This was tested by determination of Na(+) balance, uPA protein and activity, and amiloride concentration in urine from rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome. Urine samples from 6 adult and 18 pediatric patients with nephrotic syndrome were analyzed for uPA activity and protein. PAN treatment induced significant proteinuria in rats which coincided with increased urine uPA protein and activity, increased urine protease activity, and total plasminogen/plasmin concentration and Na(+) retention. Amiloride (2 mg·kg(-1)·24 h(-1)) concentration in urine was in the range 10-20 μmol/l and reduced significantly urine uPA activity, plasminogen activation, protease activity, and sodium retention in PAN rats, while proteinuria was not altered. In paired urine samples, uPA protein was significantly elevated in urine from children with active nephrotic syndrome compared with remission phase. In six adult nephrotic patients, urine uPA protein and activity correlated positively with 24 h urine protein excretion. In conclusion, nephrotic syndrome is associated with aberrant filtration of uPA across the injured glomerular barrier. Amiloride inhibits urine uPA activity which attenuates plasminogen activation and urine protease activity in vivo. Urine uPA is a relevant target for amiloride in vivo.
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark;
authors.forename: Mette
authors.initials: M
authors.lastname: Stæhr
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark;
authors.forename: Kristian B
authors.initials: KB
authors.lastname: Buhl
authors.affiliation: Department of Pediatrics, Aarhus University Hospital, Aarhus, Denmark;
authors.forename: René F
authors.initials: RF
authors.lastname: Andersen
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark;
authors.forename: Per
authors.initials: P
authors.lastname: Svenningsen
authors.affiliation: Clinical Pharmacology, Institute of Public Health, University of Southern Denmark, Odense, Denmark; and.
authors.forename: Flemming
authors.initials: F
authors.lastname: Nielsen
authors.affiliation: Department of Nephrology, Odense University Hospital, Odense, Denmark.
authors.forename: Gitte Rye
authors.initials: GR
authors.lastname: Hinrichs
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark; Department of Nephrology, Odense University Hospital, Odense, Denmark.
authors.forename: Claus
authors.initials: C
authors.lastname: Bistrup
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark; bljensen@health.sdu.dk.
authors.forename: Boye L
authors.initials: BL
authors.lastname: Jensen
mesh_terms: D000328:Adult; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002648:Child; D062686:Epithelial Sodium Channel Blockers / Q000494:pharmacology*; D053503:Epithelial Sodium Channels / Q000378:metabolism; D006801:Humans; D007678:Kidney Glomerulus / Q000378:metabolism*; D008297:Male; D009404:Nephrotic Syndrome / Q000139:chemically induced / Q000378:metabolism*; D010958:Plasminogen / Q000652:urine*; D011692:Puromycin Aminonucleoside; D051381:Rats; D017207:Rats, Sprague-Dawley; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D011692:Puromycin Aminonucleoside; D000584:Amiloride; D010958:Plasminogen; D014568:Urokinase-Type Plasminogen Activator
keywords: ENaC; edema; proteinuria; proteolysis; sodium