scholarly journals Smad2 and Smad3 Play Different Roles in Rat Hepatic Stellate Cell Function and α-Smooth Muscle Actin Organization

2005 ◽  
Vol 16 (9) ◽  
pp. 4214-4224 ◽  
Author(s):  
Masayuki Uemura ◽  
E. Scott Swenson ◽  
Marianna D.A. Gaça ◽  
Frank J. Giordano ◽  
Michael Reiss ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Transforming Growth Factor ◽  
Cell Function ◽  
Stellate Cell ◽  
Smooth Muscle Actin ◽  
Focal Adhesions ◽  
Transforming Growth Factor Β ◽  
Dominant Negative ◽  
Muscle Actin ◽  
Actin Organization

Hepatic stellate cells (HSC) play a central role in the pathogenesis of liver fibrosis, transdifferentiating in chronic liver disease from “quiescent” HSC to fibrogenic myofibroblasts. Transforming growth factor-β (TGF-β), acting both directly and indirectly, is a critical mediator of this process. To characterize the function of the TGF-β signaling intermediates Smad2 and Smad3 in HSC, we infected primary rat HSC in culture with adenoviruses expressing wild-type and dominant negative Smads 2 and 3. Smad3-overexpressing cells exhibited increased deposition of fibronectin and type 1 collagen, increased chemotaxis, and decreased proliferation compared with uninfected cells and those infected with Smad2 or either dominant negative, demonstrating different biological functions for the two Smads. Additionally, coinfection experiments suggested that Smad2 and Smad3 signal via independent pathways. Smad3-overexpressing cells as well as TGF-β-treated cells demonstrated more focal adhesions and increased α-smooth muscle actin (α-SMA) organization in stress fibers, although all cells reached the same level of α-SMA expression, indicating that Smad3 also regulates cytoskeletal organization in HSC. We suggest that TGF-β, signaling via Smad3, plays an important role in the morphological and functional maturation of hepatic myofibroblasts.

c-Myb modulates transcription of the α-smooth muscle actin gene in activated hepatic stellate cells

2000 ◽  
Vol 278 (2) ◽  
pp. G321-G328 ◽  
Author(s):  
Martina Buck ◽  
Dong Joon Kim ◽  
Karl Houglum ◽  
Tarek Hassanein ◽  
Mario Chojkier
Keyword(s):  
Smooth Muscle ◽  
Hepatic Stellate Cells ◽  
Cell Activation ◽  
Stellate Cell ◽  
Smooth Muscle Actin ◽  
Stellate Cells ◽  
Dominant Negative ◽  
Muscle Actin ◽  
Muscle Actin Gene ◽  
High Level

Expression of α-smooth muscle actin (α-SMA) defines the phenotype of activated (myofibroblastic) hepatic stellate cells. These cells, but not quiescent stellate cells, have a high level of α-SMA and c-Myb expression, as well as increased c-Myb-binding activities to the proximal α-SMA E box. Therefore, we analyzed the role of c-Myb in α-SMA transcription and stellate cell activation. Activated primary rat stellate cells displayed a high expression of the −724 and −271 α-SMA/luciferase (LUC) chimeric genes, which contain c-Myb binding sites (−223/−216 bp). α-SMA/LUC minigenes with mutation (−219/−217 bp), truncation (−224 bp), or deletion (−191 bp) of the c-Myb binding site were not efficiently transcribed. Transfection of wild-type c-Myb into quiescent stellate cells, which do not express endogenous c-Myb, induced a ∼10-fold stimulation of −724 α-SMA/LUC expression. Conversely, expression of either a dominant-negative c-Myb basic domain mutant (Cys43 → Asp) or a c-Myb antisense RNA blocked transcription from the −724 α-SMA/LUC or −271 α-SMA/LUC in activated cells. Moreover, transfection of c- myb antisense, but not sense, RNA inhibited both expression of the endogenous α-SMA gene and stellate cell activation, whereas transfection of c- myb stimulated α-SMA expression in quiescent stellate cells. These findings suggest that c-Myb modulates the activation of stellate cells and that integrity of the redox sensor Cys43in c-Myb is required for this effect.

TNF-α neutralization ameliorates obstruction-induced renal fibrosis and dysfunction

2007 ◽  
Vol 292 (4) ◽  
pp. R1456-R1464 ◽  
Author(s):  
K. K. Meldrum ◽  
R. Misseri ◽  
P. Metcalfe ◽  
C. A. Dinarello ◽  
K. L. Hile ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Western Blot ◽  
Renal Fibrosis ◽  
Transforming Growth Factor ◽  
Smooth Muscle Actin ◽  
Transforming Growth Factor Β ◽  
Unilateral Ureteral Obstruction ◽  
Muscle Actin ◽  
Renal Obstruction ◽  
Tnf Α

Upper urinary tract obstruction results in tubulointerstitial fibrosis and a progressive decline in renal function. Although several inflammatory mediators have been implicated in the pathophysiology of renal obstruction, the contribution of TNF-α to obstruction-induced fibrosis and renal dysfunction has not been thoroughly evaluated. To study this, male Sprague-Dawley rats were subjected to left unilateral ureteral obstruction vs. sham operation. Rats received either vehicle or a pegylated form of soluble TNF receptor type 1 (PEG-sTNFR1) every 84 h. The kidneys were harvested 1, 3, or 7 days postoperatively, and tissue samples were analyzed for TNF-α expression (ELISA), macrophage infiltration (ED-1 staining), transforming growth factor-β1 expression (ELISA, RT-PCR), collagen I and IV activity (Western Blot, immunohistochemistry), α-smooth muscle actin accumulation (immunohistochemistry, Western blot analysis), and angiotensinogen expression (Western blot). In a separate arm, the glomerular filtration rate (inulin clearance) of rats subjected to unilateral ureteral obstruction in the presence of either vehicle or PEG-sTNFR1 was determined. Renal obstruction induced increased tissue TNF-α and transforming growth factor-β1 levels, collagen I and IV activity, interstitial volume, α-smooth muscle actin accumulation, angiotensinogen expression, and renal dysfunction, whereas treatment with PEG-sTNFR1 significantly reduced each of these markers of renal fibrosis. These results demonstrate that TNF-α mediates obstruction-induced renal fibrosis and identify TNF-α neutralization as a potential therapeutic option for the amelioration of obstruction-induced renal injury.

scholarly journals miR-218 regulates focal adhesion kinase–dependent TGFβ signaling in fibroblasts

2014 ◽  
Vol 25 (7) ◽  
pp. 1151-1158 ◽  
Author(s):  
Fen Guo ◽  
David E. Carter ◽  
Andrew Leask
Keyword(s):  
Smooth Muscle ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Transforming Growth Factor ◽  
Smooth Muscle Actin ◽  
Transforming Growth Factor Β ◽  
Dermal Fibroblasts ◽  
Muscle Actin ◽  
Gingival Fibroblasts ◽  
Remodeling Of Extracellular Matrix

Scarring, which occurs in essentially all adult tissue, is characterized by the excessive production and remodeling of extracellular matrix by α-smooth muscle actin (SMA)–expressing myofibroblasts located within connective tissue. Excessive scarring can cause organ failure and death. Oral gingivae do not scar. Compared to dermal fibroblasts, gingival fibroblasts are less responsive to transforming growth factor β (TGFβ) due to the reduced expression, due to the reduced expression and activity of focal adhesion kinase (FAK) by this cell type. Here we show that, compared with dermal fibroblasts, gingival fibroblasts show reduced expression of miR-218. Introduction of pre–miR-218 into gingival fibroblasts elevates FAK expression and, via a FAK/src-dependent mechanism, results in the ability of TGFβ to induce α-SMA. The deubiquitinase cezanne is a direct target of miR-218 and has increased expression in gingival fibroblasts compared with dermal fibroblasts. Knockdown of cezanne in gingival fibroblasts increases FAK expression and causes TGFβ to induce α-smooth muscle actin (α-SMA). These results suggest that miR-218 regulates the ability of TGFβ to induce myofibroblast differentiation in fibroblasts via cezanne/FAK.

Sign in / Sign up

Export Citation Format

Share Document