Loss of the podocyte glucocorticoid receptor exacerbates proteinuria after injury

Sci Rep. 2017 Aug 29;7(1):9833. doi: 10.1038/s41598-017-10490-z.

Abstract

Nephrotic syndrome is a common disorder in adults and children whose etiology is largely unknown. Glucocorticoids remain the mainstay of therapy in most cases, though their mechanism of action remains poorly understood. Emerging evidence suggests that immunomodulatory therapies used in nephrotic syndrome directly target the podocytes. To study how steroids directly affect the podocytes in the treatment of proteinuria, we created a mouse model with podocyte-specific deletion of the glucocorticoid receptor. The podocyte-specific glucocorticoid receptor (GR) knockout mice had similar renal function and protein excretion compared to wild type. However, after glomerular injury induced by either LPS or nephrotoxic serum, the podocyte GR knockout mice demonstrated worsened proteinuria compared to wild type. Ultrastructural examination of podocytes confirmed more robust foot process effacement in the knockout animals. Expression of several key slit diaphragm protein was down regulated in pGR KO mice. Primary podocytes isolated from wild type and podocyte GR knockout mice showed similar actin stress fiber staining patterns in unstimulated conditions. Yet, when exposed to LPS, GR knockout podocytes demonstrated fewer stress fibers and impaired migration compared to wild type podocytes. We conclude that the podocyte glucocorticoid receptor is important for limiting proteinuria in settings of podocyte injury.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Alleles
  • Animals
  • Cell Movement
  • Disease Models, Animal
  • Female
  • Fluorescent Antibody Technique
  • Focal Adhesion Kinase 1 / genetics
  • Focal Adhesion Kinase 1 / metabolism
  • Genotype
  • Lipopolysaccharides / adverse effects
  • Lipopolysaccharides / immunology
  • Male
  • Mice
  • Mice, Knockout
  • Nephrotic Syndrome / complications
  • Nephrotic Syndrome / etiology
  • Nephrotic Syndrome / metabolism
  • Nephrotic Syndrome / pathology
  • Podocytes / metabolism*
  • Podocytes / ultrastructure
  • Proteinuria / etiology*
  • Proteinuria / metabolism
  • Proteinuria / urine
  • Receptors, Glucocorticoid / deficiency*
  • Receptors, Glucocorticoid / metabolism

Substances

  • Actins
  • Lipopolysaccharides
  • Receptors, Glucocorticoid
  • Focal Adhesion Kinase 1
  • Ptk2 protein, mouse