Angiotensin II blockade limits tubular protein overreabsorption and the consequent upregulation of endothelin 1 gene in experimental membranous nephropathy

Caria Zoja, Xue Hui Liu, Mauro Abbate, Daniela Coma, Ernesto L. Schiffrin, Giuseppe Remuzzi, Ariela Benigni

Research output: Contribution to journalArticle

Abstract

Proteinuric renal diseases are associated with excessive renal synthesis of endothelin 1 (ET- 1) either in experimental animals or humans. This has been interpreted as an upregulation of ET- 1 gene in proximal tubular cells secondary to overreaabsorption of an unusual amount of filtered proteins. Here we used a model of chronic proteinuria, passive Heymann nephritis (PHN), to localize the structure of the kidney responsible for excessive ET-1 expression and synthesis and to clarify whether drugs that reduce glomerular protein trafficking modified the distribution of ET-1 mRNA and the corresponding peptide in the kidney. PHN was induced in Sprague-Dawley rats after injection of rabbit anti-Fx1A antibody. Group 1 (n = 5) was untreated, group 2 (n = 5) was given daily the angiotensin-converting enzyme inhibitor lisinopril (40 mg/l) plus the angiotensin II receptor antagonist L-158,809 (50 mg/l) from day 7 when rats were already proteinuric - to month 12. An additional group of normal rats (n = 5) was used as controls. Urinary excretion of ET-1 was significantly increased in PHN rats as compared with controls and normalized by the treatment. By in situ hybridization a weak signal for ET-1 mRNA was detectable in glomeruli, distal tubular segments, and proximal tubules of control kidneys. By contrast, a strong labeling was found in the kidneys of rats with PHN which was mainly localized to proximal tubules and renal interstitium. The pattern of renal ET-l-like immunoreactivity was remarkably consistent with ET-1 mRNA expression. In animals with PHN given the angiotensin II blocking therapy, the urinary excretion of proteins normalized, and the structural integrity of the kidney was well preserved. In the kidney tissue taken from these animals, both ET-1 mRNA and protein staining were quite comparable to controls. These data suggest a link between excessive protein tubular reabsorption and enhanced renal ET- 1 in chronic nephropathies and provide a novel explanation for the renoprotective effect in vivo of drugs that, by blocking the biological activity of angiotensin II, reduce glomerular protein traffic and possible deleterious effects of excessive tubular protein overloading.

Original languageEnglish
Pages (from-to)121-131
Number of pages11
JournalExperimental Nephrology
Volume6
Issue number2
Publication statusPublished - 1998

    Fingerprint

Keywords

  • Angiotensin II receptor antagonist
  • Angiotensin-converting enzyme inhibitor
  • Eudothelins
  • Immunohistochemistry
  • Nonisotopic in situ hybridization
  • Passive Heymann nephritis
  • Protein overload
  • Tubular reabsorption

ASJC Scopus subject areas

  • Nephrology

Cite this