Characterization and Role of SCAI during Renal Fibrosis and Epithelial-Mesenchymal Transition.

2(nd) Department of Pathology, Semmelweis University, Budapest, Hungary.
American Journal Of Pathology (Impact Factor: 4.59). 11/2012; 182(2). DOI: 10.1016/j.ajpath.2012.10.009
Source: PubMed


During progressive tubulointerstitial fibrosis, renal tubular epithelial cells transform into α-smooth muscle actin (SMA)-expressing myofibroblasts via epithelial-mesenchymal transition (EMT). SMA expression is regulated by transforming growth factor (TGF)-β1 and cell contact disruption, through signaling events targeting the serum response factor-myocardin-related transcription factor (MRTF) complex. MRTFs are important regulators of fibrosis, tumor cell invasion, and metastasis. Consistent with the role of MRTFs in tumor progression, suppressor of cancer cell invasion (SCAI) was recently identified as a negative regulator of MRTF. Herein, we studied the role of SCAI in a fibrotic EMT model established on LLC-PK1 cells. SCAI overexpression prevented SMA promoter activation induced by TGF-β1. When co-expressed, it inhibited the stimulatory effects of MRTF-A or MRTF-B or the constitutive active forms of RhoA, Rac1, or Cdc42 on the SMA promoter. SCAI interfered with TGF-β1-induced SMA, connective tissue growth factor, and calponin protein expression; it rescued TGF-β1-induced E-cadherin down-regulation. IHC studies on human kidneys showed that SCAI expression is reduced during fibrosis. Kidneys of diabetic rats and mice with unilateral ureteral obstruction depicted significant loss of SCAI expression. In parallel with the decrease of SCAI protein expression, diabetic rat and mouse kidneys with unilateral ureteral obstruction showed SMA expression, as evidenced by using Western blot analysis. Finally, TGF-β1 treatment of LLC-PK1 cells attenuated SCAI protein expression. These data suggest that SCAI is a novel transcriptional cofactor that regulates EMT and renal fibrosis.

Download full-text


Available from: Peter Hamar,
1 Follower
48 Reads
  • Source
    • "For Western blotting analysis the excised specimens were immediately dropped into liquid nitrogen. Western blotting was performed as described previously [29]. Briefly, frozen tissue samples were homogenized in ice-cold lysis buffer in 15 ml centrifuge tubes by a mechanical homogenizer. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We and others demonstrated previously that preconditioning with endotoxin (LPS) protected from a subsequent lethal LPS challenge or from renal ischemia-reperfusion injury (IRI). LPS is effective in evoking the heat shock response, an ancient and essential cellular defense mechanism, which plays a role in resistance to, and recovery from diseases. Here, by using the pharmacological Hsp90 inhibitor novobiocin (NB), we investigated the role of Hsp90 and the heat shock response in LPS-induced delayed renal preconditioning. Male C57BL/6 mice were treated with preconditioning (P: 2 mg/kg, ip.) and subsequent lethal (L: 10 mg/kg, ip.) doses of LPS alone or in combination with NB (100 mg/kg, ip.). Controls received saline (C) or NB. Preconditioning LPS conferred protection from a subsequent lethal LPS treatment. Importantly, the protective effect of LPS preconditioning was completely abolished by a concomitant treatment with NB. LPS induced a marked heat shock protein increase as demonstrated by Western blots of Hsp70 and Hsp90. NB alone also stimulated Hsp70 and Hsp90 mRNA but not protein expression. However, Hsp70 and Hsp90 protein induction in LPS-treated mice was abolished by a concomitant NB treatment, demonstrating a NB-induced impairment of the heat shock response to LPS preconditioning. LPS-induced heat shock protein induction and tolerance to a subsequent lethal LPS treatment was prevented by the Hsp90 inhibitor, novobiocin. Our findings demonstrate a critical role of Hsp90 in LPS signaling, and a potential involvement of the heat shock response in LPS-induced preconditioning.
    PLoS ONE 03/2014; 9(3):e92004. DOI:10.1371/journal.pone.0092004 · 3.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background Bronchopulmonary dysplasia (BPD) is a major threat to the health of premature infants yet its pathogenesis is not fully understood. Epithelial-mesenchymal transition (EMT) of lung epithelial cells may lead to BPD.Objective To investigate the potential occurrence of EMT in a newborn rat model of BPD.Methods Newborn rats were exposed to a hyperoxic environment within 12 hr of birth. Lung tissue and isolated alveolar epithelial type II cells (AT2 cells) were collected on Days 1, 3, 7, 14, and 21 after hyperoxic exposure. Pathological changes in lung tissue, alveolar development, ultrastructural changes in AT2 cells, co-expression of surfactant associated surfactant protein C (SPC), and α-smooth muscle actin (α-SMA) were investigated. The relative expression of SPC, α-SMA, E-cadherin, and N-cadherin were investigated in lung tissue and isolated AT2 cells.ResultsIn lung tissue, alveolar development was attenuated from Day 7 onwards in the BPD model group; co-expression of SPC and α-SMA and ultrastructural changes typical of EMT were observed in AT2 cells from rats in the BPD group. SPC and α-SMA expression levels were higher in tissue samples from the BPD group than in control samples. Beginning on Day 7, evidence of a switch from E-cadherin to N-cadherin expression was observed in BPD lung tissue sample and in isolated AT2 cells.ConclusionEMT of AT2 cells occurred in the hyperoxia-induced newborn rat BPD model and resulted in attenuated alveolar development as a portion of the myofibroblasts accumulated in the lung originated from AT2 cells via EMT. Pediatr Pulmonol. © 2014 Wiley Periodicals, Inc.
    Pediatric Pulmonology 11/2014; 49(11). DOI:10.1002/ppul.22969 · 2.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cancer progression towards metastasis follows a defined sequence of events described as the metastatic cascade. For extravasation and transendothelial migration metastatic cells interact first with endothelial cells. Yet the role of endothelial cells during the process of metastasis formation and extravasation is still unclear, and the interaction between metastatic and endothelial cells during transendothelial migration is poorly understood. Since tumor cells are well known to express TGF-β, and the compact endothelial layer undergoes a series of changes during metastatic extravasation (cell contact disruption, cytoskeletal reorganization, enhanced contractility), we hypothesized that an EndMT may be necessary for metastatic extravasation. We demonstrate that primary cultured rat brain endothelial cells (BEC) undergo EndMT upon TGF-β1 treatment, characterized by the loss of tight and adherens junction proteins, expression of fibronectin, β1-integrin, calponin and α-smooth muscle actin (SMA). B16/F10 cell line conditioned and activated medium (ACM) had similar effects: claudin-5 down-regulation, fibronectin and SMA expression. Inhibition of TGF-β signaling during B16/F10 ACM stimulation using SB-431542 maintained claudin-5 levels and mitigated fibronectin and SMA expression. B16/F10 ACM stimulation of BECs led to phosphorylation of Smad2 and Smad3. SB-431542 prevented SMA up-regulation upon stimulation of BECs with A2058, MCF-7 and MDA-MB231 ACM as well. Moreover, B16/F10 ACM caused a reduction in transendothelial electrical resistance, enhanced the number of melanoma cells adhering to and transmigrating through the endothelial layer, in a TGF-β-dependent manner. These effects were not confined to BECs: HUVECs showed TGF-β-dependent SMA expression when stimulated with breast cancer cell line ACM. Our results indicate that an EndMT may be necessary for metastatic transendothelial migration, and this transition may be one of the potential mechanisms occurring during the complex phenomenon known as metastatic extravasation.
    PLoS ONE 03/2015; 10(3):e0119655. DOI:10.1371/journal.pone.0119655 · 3.23 Impact Factor
Show more