Journal Article

Estrogen Receptor Alpha Expression in Podocytes Mediates Protection against Apoptosis In-Vitro and In-Vivo

Lehmann, Petra, Schmitt, Claus Peter, Koleganova, Nadezda, Wegerich, Lara Vanessa, Bettendorf, Markus, Gross-Weissmann, Marie-Luise, Halbenz, Elisabeth, Mueller, Friederike, Mayatepek, Ertan, Kummer, Sebastian, Oh, Jun, Jeruschke, Stefanie, Peters, Andrea, Seibt, Annette

2011

Overview

Epidemiological studies have demonstrated that women have a significantly better prognosis in chronic renal diseases compared to men. This suggests critical influences of gender hormones on glomerular structure and function. We examined potential direct protective effects of estradiol on podocytes. Expression of estrogen receptor alpha (ERα) was examined in podocytes in vitro and in vivo. Receptor localization was shown using Western blot of separated nuclear and cytoplasmatic protein fractions. Podocytes were treated with Puromycin aminonucleoside (PAN, apoptosis induction), estradiol, or both in combination. Apoptotic cells were detected with Hoechst nuclear staining and Annexin-FITC flow cytometry. To visualize mitochondrial membrane potential depolarization as an indicator for apoptosis, cells were stained with tetramethyl rhodamine methylester (TMRM). Estradiol-induced phosphorylation of ERK1/2 and p38 MAPK was examined by Western blot. Glomeruli of ERα knock-out mice and wild-type controls were analysed by histomorphometry and immunohistochemistry. ERα was consistently expressed in human and murine podocytes. Estradiol stimulated ERα protein expression, reduced PAN-induced apoptosis in vitro by 26.5±24.6% or 56.6±5.9% (flow cytometry or Hoechst-staining, respectively; both p<0.05), and restored PAN-induced mitochondrial membrane potential depolarization. Estradiol enhanced ERK1/2 phosphorylation. In ERα knockout mice, podocyte number was reduced compared to controls (female/male: 80/86 vs. 132/135 podocytes per glomerulus, p<0.05). Podocyte volume was enhanced in ERα knockout mice (female/male: 429/371 µm(3) vs. 264/223 µm(3) in controls, p<0.05). Tgfβ1 and collagen type IV expression were increased in knockout mice, indicating glomerular damage. Podocytes express ERα, whose activation leads to a significant protection against experimentally induced apoptosis. Possible underlying mechanisms include stabilization of mitochondrial membrane potential and activation of MAPK signalling. Characteristic morphological changes indicating glomerulopathy in ERα knock-out mice support the in vivo relevance of the ERα for podocyte viability and function. Thus, our findings provide a novel model for the protective influence of female gender on chronic glomerular diseases.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: 17β-Estradiol / Activation / Animals / Apoptosis / Apoptosis - drug effects / Apoptosis - genetics / Beta blockers / Biology / Blotting, Western / Cells, Cultured / Children & youth / Collagen (type IV) / Comparative analysis / Cytometry / Depolarization / Epidemiology / Estradiol / Estradiol - pharmacology / Estrogen / Estrogen Receptor alpha - genetics / Estrogen Receptor alpha - metabolism / Estrogens / Extracellular signal-regulated kinase / Females / Flow Cytometry / Gender / Glomerulus / Growth hormones / Histomorphometry / Hormones / Humans / Hypertension / Immunohistochemistry / Kidney diseases / Kidney Glomerulus - metabolism / Kidney transplantation / Kinases / Localization / Males / MAP kinase / Medical prognosis / Medical research / Medicine / Membrane potential / Membrane Potential, Mitochondrial / Membranes / Mice / Mice, Knockout / Mitochondria / Mitogen-Activated Protein Kinase 1 - genetics / Mitogen-Activated Protein Kinase 1 - metabolism / Mitogen-Activated Protein Kinase 3 - genetics / Mitogen-Activated Protein Kinase 3 - metabolism / Morphology / Nephrology / p38 Mitogen-Activated Protein Kinases - genetics / p38 Mitogen-Activated Protein Kinases - metabolism / Pathology / Pediatrics / Phenols (Class of compounds) / Phosphorylation / Physical characteristics / Podocytes - cytology / Podocytes - drug effects / Podocytes - metabolism / Prognosis / Proteins / Puromycin / Puromycin Aminonucleoside - pharmacology / Receptors / Rhodamine / Rodents / Sex hormones / Signal Transduction - genetics / Signal Transduction - physiology / Signaling / Staining / Structure-function relationships / Transforming growth factor-b1 / Transforming growth factors / Tumor necrosis factor-TNF / Viability