Circulating extracellular vesicles of patients with steroid-sensitive nephrotic syndrome have higher RAC1 and induce recapitulation of nephrotic syndrome phenotype in podocytes

Am J Physiol Renal Physiol. 2021 Nov 1;321(5):F659-F673. doi: 10.1152/ajprenal.00097.2021. Epub 2021 Sep 27.

Abstract

Since previous research suggests a role of a circulating factor in the pathogenesis of steroid-sensitive nephrotic syndrome (NS), we speculated that circulating plasma extracellular vesicles (EVs) are a candidate source of such a soluble mediator. Here, we aimed to characterize and try to delineate the effects of these EVs in vitro. Plasma EVs from 20 children with steroid-sensitive NS in relapse and remission, 10 healthy controls, and 6 disease controls were obtained by serial ultracentrifugation. Characterization of these EVs was performed by electron microscopy, flow cytometry, and Western blot analysis. Major proteins from plasma EVs were identified via mass spectrometry. Gene Ontology classification analysis and Ingenuity Pathway Analysis were performed on selectively expressed EV proteins during relapse. Immortalized human podocyte culture was used to detect the effects of EVs on podocytes. The protein content and particle number of plasma EVs were significantly increased during NS relapse. Relapse NS EVs selectively expressed proteins that involved actin cytoskeleton rearrangement. Among these, the level of RAC-GTP was significantly increased in relapse EVs compared with remission and disease control EVs. Relapse EVs were efficiently internalized by podocytes and induced significantly enhanced motility and albumin permeability. Moreover, relapse EVs induced significantly higher levels of RAC-GTP and phospho-p38 and decreased the levels of synaptopodin in podocytes. Circulating relapse EVs are biologically active molecules that carry active RAC1 as cargo and induce recapitulation of the NS phenotype in podocytes in vitro.NEW & NOTEWORTHY Up to now, the role of extracellular vesicles (EVs) in the pathogenesis of steroid-sensitive nephrotic syndrome (NS) has not been studied. Here, we found that relapse NS EVs contain significantly increased active RAC1, induce enhanced podocyte motility, and increase expression of RAC-GTP and phospho-p38 expression in vitro. These results suggest that plasma EVs are biologically active molecules in the pathogenesis of NS.

Keywords: RAC1; children; extracellular vesicles; nephrotic syndrome; phospho-p38.

MeSH terms

  • Adolescent
  • Case-Control Studies
  • Cell Line
  • Child
  • Child, Preschool
  • Extracellular Vesicles / enzymology*
  • Extracellular Vesicles / ultrastructure
  • Female
  • Humans
  • Male
  • Microfilament Proteins / metabolism
  • Nephrotic Syndrome / blood
  • Nephrotic Syndrome / drug therapy
  • Nephrotic Syndrome / enzymology*
  • Nephrotic Syndrome / pathology
  • Phenotype
  • Phosphorylation
  • Podocytes / enzymology*
  • Podocytes / pathology
  • Recurrence
  • Remission Induction
  • Steroids / therapeutic use
  • Treatment Outcome
  • p38 Mitogen-Activated Protein Kinases / metabolism
  • rac1 GTP-Binding Protein / blood*

Substances

  • Microfilament Proteins
  • RAC1 protein, human
  • SYNPO protein, human
  • Steroids
  • p38 Mitogen-Activated Protein Kinases
  • rac1 GTP-Binding Protein

Associated data

  • figshare/10.6084/m9.figshare. 15153141.v2