title: Urine exosomes from healthy and hypertensive pregnancies display elevated level of α-subunit and cleaved α- and γ-subunits of the epithelial sodium channel-ENaC.
abstract: Preeclampsia is characterized by hypertension, proteinuria, suppression of plasma renin-angiotensin-aldosterone, and impaired urine sodium excretion. Aberrantly filtered plasmin in urine may activate proteolytically the γ-subunit of the epithelial sodium channel (ENaC) and promote Na+reabsorption and urine K+loss. Plasma and urine was sampled from patients with preeclampsia, healthy pregnant controls and non-pregnant women, and from patients with nephrostomy catheters. Aldosterone concentration, urine plasminogen, and protein were determined. Exosomes were isolated by ultracentrifugation. Immunoblotting was used to detect exosome markers; γ-ENaC (two different epitopes within the inhibitory peptide tract), α-ENaC, and renal outer medullary K-channel (ROMK) and compared with human kidney cortex homogenate. Urine total plasmin(ogen) was significantly increased in preeclampsia, plasma and urine aldosterone was higher in pregnancy compared to non-pregnancy, and the urine Na/K ratio was lower in preeclampsia compared to healthy pregnancy. Exosome markers ALIX and AQP-2 were stably associated with exosomes across groups. Exosomal α-ENaC-subunit migrated at 75 kDa and dominantly at 50 kDa and was significantly elevated in pregnancy. In human kidney cortex tissue and two of four pelvis catheter urine, ~90-100 kDa full-length γ-ENaC was detected while no full-length γ-ENaC but 75, 60, and 37 kDa variants dominated in voided urine exosomes. There was no difference in γ-ENaC protein abundances between healthy pregnancy and preeclampsia. ROMK was detected inconsistently in urine exosomes. Pregnancy and preeclampsia were associated with increased abundance of furin-cleaved α-ENaC subunit while γ-subunit appeared predominantly in cleaved form independently of conditions and with a significant contribution from post-renal cleavage.
authors.affiliation: The Research Unit, Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark.|Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Maria R
authors.initials: MR
authors.lastname: Nielsen
authors.affiliation: The Research Unit, Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark.|Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Britta
authors.initials: B
authors.lastname: Frederiksen-Møller
authors.affiliation: Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Rikke
authors.initials: R
authors.lastname: Zachar
authors.affiliation: The Research Unit, Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Jørgensen
authors.affiliation: Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Mie R
authors.initials: MR
authors.lastname: Hansen
authors.affiliation: Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Rikke
authors.initials: R
authors.lastname: Ydegaard
authors.affiliation: Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark.
authors.forename: Per
authors.initials: P
authors.lastname: Svenningsen
authors.affiliation: Department of Nephrology, Fredericia hospital, Fredericia, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Buhl
authors.affiliation: Department of Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, J. B. Winsloews Vej 21,3, 5000, Odense, Denmark. bljensen@health.sdu.dk.
authors.forename: Boye L
authors.initials: BL
authors.lastname: Jensen
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000652:urine; D053503:Epithelial Sodium Channels / Q000378:metabolism / Q000652:urine*; D055354:Exosomes / Q000378:metabolism*; D005260:Female; D005341:Fibrinolysin / Q000652:urine; D006801:Humans; D006973:Hypertension / Q000378:metabolism / Q000652:urine*; D007668:Kidney / Q000378:metabolism; D011188:Potassium / Q000652:urine; D011225:Pre-Eclampsia / Q000378:metabolism / Q000652:urine; D011247:Pregnancy; D021122:Protein Subunits / Q000378:metabolism / Q000652:urine*; D011507:Proteinuria / Q000378:metabolism / Q000652:urine; D012964:Sodium / Q000652:urine; D014556:Urine / Q000502:physiology*
chemical_list: D053503:Epithelial Sodium Channels; D021122:Protein Subunits; D000450:Aldosterone; D012964:Sodium; D005341:Fibrinolysin; D011188:Potassium
keywords: Aldosterone; Preeclampsia; Protease; Proteinuria