The cardiotonic steroid hormone marinobufagenin induces renal fibrosis: implication of epithelial-to-mesenchymal transition

• Published in: American journal of physiology. Renal physiology Vol. 296; no. 4; pp. F922 - F934
• Main Authors: Fedorova, Larisa V, Raju, Vanamala, El-Okdi, Nasser, Shidyak, Amjad, Kennedy, David J, Vetteth, Sandeep, Giovannucci, David R, Bagrov, Alexei Y, Fedorova, Olga V, Shapiro, Joseph I, Malhotra, Deepak
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.04.2009
• Subjects: Animals; Bufanolides - administration & dosage; Bufanolides - toxicity; Cardiotonic Agents - administration & dosage; Cardiotonic Agents - toxicity; Cell Movement - drug effects; Cell Shape - drug effects; Cell Transdifferentiation - drug effects; Cells; Collagen Type I - metabolism; Enzyme Inhibitors - toxicity; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Epithelial Cells - pathology; Fibronectins - metabolism; Fibrosis; Gene expression; Heart; Infusion Pumps, Implantable; Kidney - drug effects; Kidney - metabolism; Kidney - pathology; Kidney diseases; Kidney Diseases - chemically induced; Kidney Diseases - metabolism; Kidney Diseases - pathology; LLC-PK1 Cells; Male; Mesoderm - drug effects; Mesoderm - metabolism; Mesoderm - pathology; Ouabain - pharmacology; Proteins; Rats; Rats, Sprague-Dawley; Rodents; Signal Transduction - drug effects; Snail Family Transcription Factors; Sodium-Potassium-Exchanging ATPase - antagonists & inhibitors; Sodium-Potassium-Exchanging ATPase - metabolism; Studies; Swine; Time Factors; Transcription Factors - metabolism; Vimentin - metabolism
• ISSN: 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.90605.2008

We recently demonstrated that the cardiotonic steroid marinobufagenin (MBG) induced fibrosis in rat hearts through direct stimulation of collagen I secretion by cardiac fibroblasts. This stimulation was also responsible for the cardiac fibrosis seen in experimental renal failure. In this study, the effect of MBG on the development of renal fibrosis in rats was investigated. Four weeks of MBG infusion triggered mild periglomerular and peritubular fibrosis in the cortex and the appearance of fibrotic scars in the corticomedullary junction of the kidney. MBG also significantly increased the protein levels and nuclear localization of the transcription factor Snail in the tubular epithelia. It is known that activation of Snail is associated with epithelial-to-mesenchymal transition (EMT) during renal fibrosis. To examine whether MBG alone can trigger EMT, we used the porcine proximal tubular cell line LLC-PK1. MBG (100 nM) caused LLC-PK1 cells grown to confluence to acquire a fibroblast-like shape and have an invasive motility. The expressions of the mesenchymal proteins collagen I, fibronectin, and vimentin were increased twofold. However, the total level of E-cadherin remained unchanged. These alterations in LLC-PK1 cells in the presence of MBG were accompanied by elevated expression and nuclear translocation of Snail. During the time course of EMT, MBG did not have measurable inhibitory effects on the ion pumping activity of its natural ligand, Na(+)-K(+)-ATPase. Our data suggest that the MBG may be an important factor in inducing EMT and, through this mechanism, elevated levels of MBG in chronic renal failure may play a role in the progressive fibrosis.