Aldosterone induces epithelial-mesenchymal transition via ROS of mitochondrial origin

Abstract

It has been well appreciated that aldosterone (Aldo) plays a direct profibrotic role in the kidney but the underlying mechanism is unclear. We examined the role of Aldo in epithelial-mesenchymal transition (EMT) both in vitro and in vivo. Exposure of human renal proximal tubular cells to Aldo for 48 h dose dependently induced EMT as evidenced by conversion to the spindle-like morphology, loss of E-cadherin, and de novo expression of ␣-smooth muscle actin (SMA); the effect was noticeable at 50 nM and maximal at 100 nM. The EMT was completely blocked by the selective mineralocorticoid receptor (MR) antagonist eplerenone. Aldo time dependently increased intracellular reactive oxygen species (ROS) production that was detectable at 15 min and peaked (2.3-fold) at 60 min, as assessed by 2Ј,7Ј-dichlorofluorescin diacetate fluorescence. Aldo-induced oxidative stress and EMT were both abolished by the mitochondrial respiratory chain complex I inhibitor rotenone, but not the NADPH oxidase inhibitor apocynin. Aldo induced phosphorylation of ERK1/2 that was completely blocked by rotenone. Male 129-C57/BL6 mice were treated with deoxycorticosterone acetate (DOCA) salt (subcutaneous implantation of 50 mg of DOCA pellet plus 1% NaCl as drinking fluid) for 3 wk and animals were treated with vehicle or rotenone (600 ppm in diet) for the last week. DOCA salt induced a 2.5-fold increase in ␣-SMA and a 30% reduction of E-cadherin, as assessed by real-time RT-PCR, that were both restricted to renal epithelial cells, as determined by immunohistochemistry. In contrast, DOCA salt-induced changes in ␣-SMA and E-cadherin were completely blocked by treatment with rotenone. These observations suggest that Aldo induces EMT via MR-mediated, mitochondrial-originated, ROS-dependent ERK1/2 activation in renal tubular epithelial cells. reactive oxygen species; renal tubular epithelial cells THE MINERALOCORTICOIDS aldosterone (Aldo) and deoxycorticosterone acetate (DOCA), first identified as a circulating hormone for the regulation of salt homeostasis through mineralocorticoid receptor (MR)-dependent mechanisms, appear now as a major mediator of fibrosis in a number of organs such as the heart (20, 30) and kidney (2). In 1996, Greene et al. (7) provided the first evidence for the involvement of Aldo in the pathogenesis of renal injury in remnant kidney hypertensive rats. A growing body of evidence substantiates the pathologic role of Aldo in renal fibrosis. In this regard, plasma Aldo concentration was markedly elevated, and exogenous infusion of Aldo reversed the renoprotective effects of angiotensinconverting enzyme (ACE) inhibitors in remnant kidney hypertensive rats (7) and stroke-prone, spontaneously hypertensive rats (SHRsp) (23). Furthermore, renal expression of MR in SHRsp rats was significantly elevated compared with normotensive Wistar-Kyoto rats (8). In line with this finding, blockade of MR was renoprotective without altering blood pressure in the N -nitro-L-arginine methyl ester (L-NAME) rat model (24). These studies indicate that Al...

Mitochondrial Dysfunction Mediates Aldosterone-Induced Podocyte Damage

“…6 To validate this phenomenon, we tested the effect of rotenone on Aldo-induced ROS production in podocytes. Indeed, the induction of ROS production in response to Aldo treatment was inhibited by rotenone ( Figure 3, A-C).…”

“…Moreover, exogenous infusion of Aldo reverses the renoprotective effects of angiotensin-converting enzyme inhibitors in hypertensive remnant kidney rats, and in stroke-prone, spontaneously hypertensive rats. 2 In vitro studies show that Aldo exerts a direct deleterious influence on kidney cells, including podocytes, 3-5 mesangial cells, proximal tubular epithelial cells, 6 and fibroblasts. In particular, Aldo causes podocyte injury in vivo and in vitro, and Aldo blockade is therapeutic in renal injury.…”

“…17,18 Our previous study showed that Aldo-induced renal proximal tubular epithelial cell injury was mediated by mt reactive oxygen species (ROS). 6 We postulated that the same mediator (ie, mt ROS) may contribute to Aldo-induced podocyte injury and may serve as a therapeutic target of PPAR␥ agonists in renal diseases. Therefore, the present study was designed to test whether Aldo induced mt injury and ROS generation and PPAR␥ protects against the Aldo effects in in vivo and in vitro.…”

Hypoxia-induced alveolar epithelial-mesenchymal transition requires mitochondrial ROS and hypoxia-inducible factor 1

“…Active TGF-␤1 binds to the transmembrane serine-threonine kinase receptor II and receptor I and activates Smad-mediated transcription of target genes, including ␣-SMA and vimentin, which leads to EMT (33,53,54). TGF-␤1 is reported to induce EMT in renal proximal tubular epithelial cells, lens epithelial cells, and, most recently, alveolar epithelial cells (AEC) (19,23,40,48,55).AEC perform many tasks necessary for normal alveolus functioning, including surfactant protein production and fluid and ion transport (17, 57). Recent evidence suggests that AEC may undergo EMT, contributing to the pathogenesis of pulmonary fibrosis (26,49).…”

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

“…This transition to mesenchyme is accompanied by the loss of cell-cell contacts and the gain of cell motility (30,32,86). EMT in renal tubular cells can be triggered by different growth factors (78,91) and by stimuli such as aldosterone (93), oxidative stress (71), hypoxia (47), mechanical stretch (72), cyclosporine A (52), oncostatin M (61,67), and advanced glycation end products (40).…”