Urokinase-type plasminogen activator (uPA) is not essential for epithelial sodium channel (ENaC)-mediated sodium retention in experimental nephrotic syndrome.

Abstract

AIM:

In nephrotic syndrome, aberrantly filtered plasminogen (plg) is converted to active plasmin by tubular urokinase-type plasminogen activator (uPA) and thought to lead to sodium retention by proteolytic activation of the epithelial sodium channel (ENaC). This concept predicts that uPA is an important factor for sodium retention and that inhibition of uPA might be protective in nephrotic syndrome.

METHODS:

Activation of amiloride-sensitive currents by uPA and plg were studied in Xenopus laevis oocytes expressing murine ENaC. In doxorubicin-induced nephrotic mice, uPA was inhibited pharmacologically by amiloride and genetically by the use of uPA-deficient mice (uPA-/- ).

RESULTS:

Experiments in Xenopus laevis oocytes expressing murine ENaC confirmed proteolytic ENaC activation by a combination of plg and uPA which stimulated amiloride-sensitive currents with concomitant cleavage of the ENaC γ-subunit at the cell surface. Treatment of nephrotic wild-type mice with amiloride inhibited urinary uPA activity, prevented urinary plasmin formation and sodium retention. In nephrotic mice lacking uPA (uPA-/- ), urinary plasmin formation from plg was suppressed and urinary uPA activity absent. However, in nephrotic uPA-/- mice, sodium retention was not reduced compared to nephrotic uPA+/+ mice. Amiloride prevented sodium retention in nephrotic uPA-/- mice which confirmed the critical role of ENaC in sodium retention.

CONCLUSION:

uPA is responsible for the conversion of aberrantly filtered plasminogen to plasmin in the tubular lumen in vivo. However, uPA-dependent plasmin generation is not essential for ENaC-mediated sodium retention in experimental nephrotic syndrome.

• Authors: Bernhard N Bohnert, Sophie Daiminger, Matthias Wörn, Florian Sure, Tobias Staudner, Alexandr V Ilyaskin, Firas Batbouta, Andrea Janessa, Jonas C Schneider, Daniel Essigke, Sandip Kanse, Silke Haerteis, Christoph Korbmacher, Ferruh Artunc
• Journal: Acta physiologica (Oxford, England) (Acta Physiol (Oxf)) Vol. 227 Issue 4 Pg. e13286 (12 2019) ISSN: 1748-1716 [Electronic] England
• PMID: 31006168 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2019 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Chemical References

• Epithelial Sodium Channel Blockers
• Epithelial Sodium Channels
• Amiloride
• Sodium
• Urokinase-Type Plasminogen Activator

Topics

• Amiloride (administration & dosage, pharmacology)
• Animals
• Dose-Response Relationship, Drug
• Epithelial Sodium Channel Blockers (administration & dosage, pharmacology)
• Epithelial Sodium Channels (genetics, metabolism)
• Gene Expression Regulation (drug effects)
• Ion Channel Gating
• Mice
• Mice, Knockout
• Nephrotic Syndrome
• Oocytes
• Sodium (metabolism)
• Urokinase-Type Plasminogen Activator (genetics, metabolism)
• Xenopus laevis