Disruption of transforming growth factor-β signaling by curcumin induces gene expression of peroxisome proliferator-activated receptor-γ in rat hepatic stellate cells

2007 ◽  
Vol 292 (1) ◽  
pp. G113-G123 ◽  
Author(s):  
Shizhong Zheng ◽  
Anping Chen
Keyword(s):  
Gene Expression ◽  
Hepatic Stellate Cells ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Gene Promoter ◽  
Stellate Cells ◽  
Transforming Growth Factor Β ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Ppar Γ

Activation of hepatic stellate cells (HSC), the major effectors of hepatic fibrogenesis, is coupled with sequential alterations in gene expression, including an increase in receptors for transforming growth factor-β (TGF-β) and a dramatic reduction in the peroxisome proliferator-activated receptor-γ (PPAR-γ). The relationship between them remains obscure. We previously demonstrated that curcumin induced gene expression of PPAR-γ in activated HSC, leading to reducing cell proliferation, inducing apoptosis and suppressing expression of extracellular matrix genes. The underlying molecular mechanisms are largely unknown. We recently observed that stimulation of PPAR-γ activation suppressed gene expression of TGF-β receptors in activated HSC, leading to the interruption of TGF-β signaling. This observation supported our assumption of an antagonistic relationship between PPAR-γ activation and TGF-β signaling in HSC. In this study, we further hypothesize that TGF-β signaling might negatively regulate gene expression of PPAR-γ in activated HSC. The present report demonstrates that exogenous TGF-β1 inhibits gene expression of PPAR-γ in activated HSC, which is eliminated by the pretreatment with curcumin likely by interrupting TGF-β signaling. Transfection assays further indicate that blocking TGF-β signaling by dominant negative type II TGF-β receptor increases the promoter activity of PPAR-γ gene. Promoter deletion assays, site-directed mutageneses, and gel shift assays localize two Smad binding elements (SBEs) in the PPAR-γ gene promoter, acting as curcumin response elements and negatively regulating the promoter activity in passaged HSC. The Smad3/4 protein complex specifically binds to the SBEs. Overexpression of Smad4 dose dependently eliminates the inhibitory effects of curcumin on the PPAR-γ gene promoter and TGF-β signaling. Taken together, these results demonstrate that the interruption of TGF-β signaling by curcumin induces gene expression of PPAR-γ in activated HSC in vitro. Our studies provide novel insights into the molecular mechanisms of curcumin in the induction of PPAR-γ gene expression and in the inhibition of HSC activation.

Cellular crosstalk mediated by platelet-derived growth factor BB and transforming growth factor β during hepatic injury activates hepatic stellate cells

2018 ◽  
Vol 96 (8) ◽  
pp. 728-741 ◽  
Author(s):  
Sowmya Mekala ◽  
SubbaRao V. Tulimilli ◽  
Ramasatyaveni Geesala ◽  
Kanakaraju Manupati ◽  
Neha R. Dhoke ◽  
...  
Keyword(s):  
Growth Factor ◽  
Hepatic Stellate Cells ◽  
Hepg2 Cells ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Stellate Cells ◽  
Transforming Growth Factor Β ◽  
Platelet Derived Growth Factor ◽  
Hepatic Tissue

Apoptotic hepatocytes release factors that activate hepatic stellate cells (HSCs), thereby inducing hepatic fibrosis. In the present study, in vivo and in vitro injury models were established using acetaminophen, ethanol, carbon tetrachloride, or thioacetamide. Histology of hepatotoxicant-induced diseased hepatic tissue correlated with differential expression of fibrosis-related genes. A marked increase in co-staining of transforming growth factor β receptor type II (TGFRIIβ) – desmin or α-smooth muscle actin – platelet-derived growth factor receptor β (PDGFRβ), markers of activated HSCs, in liver sections of these hepatotoxicant-treated mice also depicted an increase in Annexin V – cytokeratin expressing hepatocytes. To understand the molecular mechanisms of disease pathology, in vitro experiments were designed using the conditioned medium (CM) of hepatotoxicant-treated HepG2 cells supplemented to HSCs. A significant increase in HSC proliferation, migration, and expression of fibrosis-related genes and protein was observed, thereby suggesting the characteristics of an activated phenotype. Treating HepG2 cells with hepatotoxicants resulted in a significant increase in mRNA expression of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β (TGFβ). CM supplemented to HSCs resulted in increased phosphorylation of PDGFRβ and TGFRIIβ along with its downstream effectors, extracellular signal-related kinase 1/2 and focal adhesion kinase. Neutralizing antibodies against PDGF-BB and TGFβ effectively perturbed the hepatotoxicant-treated HepG2 cell CM-induced activation of HSCs. This study suggests PDGF-BB and TGFβ as potential molecular targets for developing anti-fibrotic therapeutics.

Transforming growth factor-β1 downregulation of Smad1 gene expression in rat hepatic stellate cells

2003 ◽  
Vol 285 (3) ◽  
pp. G539-G546 ◽  
Author(s):  
Hong Shen ◽  
Guojiang Huang ◽  
Mohammed Hadi ◽  
Patrick Choy ◽  
Manna Zhang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Hepatic Stellate Cells ◽  
Intracellular Signaling ◽  
Transforming Growth Factor ◽  
Stellate Cells ◽  
Transforming Growth Factor Β ◽  
Transforming Growth Factor Β1 ◽  
Dependent Manner ◽  
Tgf Β1

Smads are intracellular signaling molecules of the transforming growth factor-β (TGF-β) superfamily that play an important role in the activation of hepatic stellate cells (HSCs) and hepatic fibrosis. Excepting the regulation of Smad7, receptor-regulated Smad gene expression is still unclear. We employed rat HSCs to investigate the expression and regulation of the Smad1 gene, which is a bone morphogenetic protein (BMP) receptor-regulated Smad. We found that the expression and phosphorylation of Smad1 are increased during the activation of HSCs. Moreover, TGF-β significantly inhibits Smad1 gene expression in HSCs in a time- and dose-dependent manner. Furthermore, although both TGF-β1 and BMP2 stimulate the activation of HSCs, they have different effects on HSC proliferation. In conclusion, Smad1 expression and phosphorylation are increased during the activation of HSCs and TGF-β1 significantly inhibits the expression of the Smad1 gene.

scholarly journals Platyconic Acid A, Platycodi Radix-Derived Saponin, Suppresses TGF-β1-Induced Activation of Hepatic Stellate Cells via Blocking SMAD and Activating the PPARγ Signaling Pathway

Cells ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1544 ◽  
Author(s):  
Jae Ho Choi ◽  
Seul Mi Kim ◽  
Gi Ho Lee ◽  
Sun Woo Jin ◽  
Hyun Sun Lee ◽  
...  
Keyword(s):  
Hepatic Stellate Cells ◽  
Stellate Cells ◽  
Inhibitory Effect ◽  
Peroxisome Proliferator ◽  
Health Food ◽  
Inhibitory Effects ◽  
Peroxisome Proliferator Activated Receptor ◽  
Ppar Γ ◽  
Platycodi Radix ◽  
Tgf Β1

Platycodi radix is a widely sold health food worldwide, which contains numerous phytochemicals that are beneficial to health. Previously, we reported that saponin from the roots of Platycodi radix-derived saponin inhibited toxicant-induced liver diseases. Nevertheless, the inhibitory effect of platyconic acid A (PA), the active component of Platycodi radix-derived saponin, on the anti-fibrotic activity involving the SMAD pathway remains unclear. We investigated the inhibitory effects of PA on TGF-β1-induced activation of hepatic stellate cells (HSCs). PA inhibited TGF-β1-enhanced cell proliferation, as well as expression of α-SMA and collagen Iα1 in HSC-T6 cells. PA suppressed TGF-β1-induced smad2/3 phosphorylation and smad binding elements 4 (SBE4) luciferase activity. Reversely, PA restored TGF-β1-reduced expression of smad7 and peroxisome proliferator-activated receptor (PPAR)γ. PA also repressed TGF-β1-induced phosphorylation of Akt and MAPKs. In summary, the results suggest that the inhibitory effect of PA on HSCs occurs through the blocking of SMAD-dependent and SMAD-independent pathways, leading to the suppression of α-SMA and collagen Iα1 expression.

scholarly journals Curcumin Inhibits srebp-2 Expression in Activated Hepatic Stellate Cells in Vitro by Reducing the Activity of Specificity Protein-1

Endocrinology ◽  
2009 ◽  
Vol 150 (12) ◽  
pp. 5384-5394 ◽  
Author(s):  
Qiaohua Kang ◽  
Anping Chen
Keyword(s):  
Gene Expression ◽  
Hepatic Stellate Cells ◽  
Molecular Mechanisms ◽  
Regulatory Element ◽  
Stellate Cells ◽  
Peroxisome Proliferator ◽  
Specificity Protein 1 ◽  
Gc Box ◽  
Specificity Protein

Abstract Elevated levels of cholesterol/low-density lipoprotein (LDL) are a risk factor for the development of nonalcoholic steatohepatitis and its associated hepatic fibrosis. However, underlying mechanisms remain elusive. We previously reported that curcumin induced gene expression of peroxisome proliferator-activated receptor (PPAR)-γ and stimulated its activity, leading to the inhibition of the activation of hepatic stellate cells (HSCs), the major effector cells during hepatic fibrogenesis. We recently showed that curcumin suppressed gene expression of LDL receptor in activated HSCs in vitro by repressing gene expression of the transcription factor sterol regulatory element binding protein-2 (SREBP-2), leading to the reduction in the level of intracellular cholesterol in HSCs and to the attenuation of the stimulatory effects of LDL on HSCs activation. The current study aimed at exploring molecular mechanisms by which curcumin inhibits srebp-2 expression in HSCs. Promoter deletion assays, mutagenesis assays, and EMSAs localize a specificity protein-1 (SP-1) binding GC-box in the srebp-2 promoter, which is responsible for enhancing the promoter activity and responding to curcumin in HSCs. Curcumin suppresses gene expression of SP-1 and reduces its trans-activation activity, which are mediated by the activation of PPARγ. The inhibitory effect of curcumin on SP-1 binding to the GC-box is confirmed by chromatin immuno-precipitation. In summary, our results demonstrate that curcumin inhibits srebp-2 expression in cultured HSCs by activating PPARγ and reducing the SP-1 activity, leading to the repression of ldlr expression. These results provide novel insights into molecular mechanisms by which curcumin inhibits LDL-induced HSC activation.

scholarly journals Sodium Acetate Inhibit TGF-β1-Induced Activation of Hepatic Stellate Cells by Restoring AMPK or c-Jun Signaling

2021 ◽  
Vol 8 ◽  
Author(s):  
Weiwei Li ◽  
Mingjuan Deng ◽  
Jiahui Gong ◽  
Xiaoying Zhang ◽  
Shaoyang Ge ◽  
...  
Keyword(s):  
Hepatic Stellate Cells ◽  
Sodium Acetate ◽  
Cell Activation ◽  
Stellate Cells ◽  
Short Chain Fatty Acids ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Protein Levels ◽  
Ppar Γ ◽  
Tgf Β1

Short-chain fatty acids (SCFAs) are crucial gut microbial metabolites that play a major role in the occurrence and development of hepatic fibrosis (HF). However, the effect of SCFAs on hepatic stellate cells (HSCs), the major pro-fibrogenic cells, is yet undefined. In this study, the effects of three major SCFAs (acetate, propionate, and butyrate) were assessed on the activation of HSCs. LX2 cells were activated with TGF-β1 and treated with sodium acetate (NaA), sodium propionate (NaP), or sodium butyrate (NaB). SCFA treatment significantly reduced the protein levels of α-SMA and the phosphorylation of Smad2 and decreased the mRNA expression of Acta2/Col1a1/Fn in cells compared to the TGF-β1 treatment. Among the three SCFAs, NaA revealed the best efficacy at alleviating TGF-β1-induced LX2 cell activation. Additionally, acetate accumulated in the cells, and G protein-coupled receptor (GPR) 43 silencing did not have any impact on the inhibition of LX2 cell activation by NaA. These findings indicated that NaA enters into the cells to inhibit LX2 cell activation independent of GPR43. The results of phosphokinase array kit and Western blot indicated that NaA increased the AMP-activated protein kinase (AMPK) activation and reduced the phosphorylation of c-Jun in cultured LX2 cells, and siRNA-peroxisome proliferator-activated receptor (PPAR) -γ abolished the inhibitory effects of NaA against TGF-β1-induced LX2 cell activation. In conclusion, this study showed that NaA inhibited LX2 cell activation by activating the AMPK/PPARγ and blocking the c-Jun signaling pathways. Thus, SCFAs might represent a novel and viable approach for alleviating HF.

scholarly journals Hypoxia-induced inhibition of lung development is attenuated by the peroxisome proliferator-activated receptor-γ agonist rosiglitazone

2011 ◽  
Vol 301 (1) ◽  
pp. L125-L134 ◽  
Author(s):  
Teodora Nicola ◽  
Namasivayam Ambalavanan ◽  
Wei Zhang ◽  
Masheika L. James ◽  
Virender Rehan ◽  
...  
Keyword(s):  
Lung Development ◽  
Transforming Growth Factor ◽  
Neutralizing Antibody ◽  
Transforming Growth Factor Β ◽  
Lung Compliance ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Ppar Γ ◽  
Alveolar Development ◽  
Lung Histology

Hypoxia enhances transforming growth factor-β (TGF-β) signaling, inhibiting alveolar development and causing abnormal pulmonary arterial remodeling in the newborn lung. We hypothesized that, during chronic hypoxia, reduced peroxisome proliferator-activated receptor-γ (PPAR-γ) signaling may contribute to, or be caused by, excessive TGF-β signaling. To determine whether PPAR-γ was reduced during hypoxia, C57BL/6 mice were exposed to hypoxia from birth to 2 wk and evaluated for PPAR-γ mRNA and protein. To determine whether rosiglitazone (RGZ, a PPAR-γ agonist) supplementation attenuated the effects of hypoxia, mice were exposed to air or hypoxia from birth to 2 wk in combination with either RGZ or vehicle, and measurements of lung histology, function, parameters related to TGF-β signaling, and collagen content were made. To determine whether excessive TGF-β signaling reduced PPAR-γ, mice were exposed to air or hypoxia from birth to 2 wk in combination with either TGF-β-neutralizing antibody or vehicle, and PPAR-γ signaling was evaluated. We observed that hypoxia reduced PPAR-γ mRNA and protein, in association with impaired alveolarization, increased TGF-β signaling, reduced lung compliance, and increased collagen. RGZ increased PPAR-γ signaling, with improved lung development and compliance in association with reduced collagen and TGF-β signaling. However, no reduction was noted in hypoxia-induced pulmonary vascular remodeling. Inhibition of hypoxia-enhanced TGF-β signaling increased PPAR-γ signaling. These results suggest that hypoxia-induced inhibition of lung development is associated with a mutually antagonistic relationship between reduced PPAR-γ and increased TGF-β signaling. PPAR-γ agonists may be of potential therapeutic significance in attenuating TGF-β signaling and improving alveolar development.

The effect of high glucose and PPAR-γ agonists on PPAR-γ expression and function in HK-2 cells

2004 ◽  
Vol 287 (3) ◽  
pp. F528-F534 ◽  
Author(s):  
U. Panchapakesan ◽  
C. A. Pollock ◽  
X. M. Chen
Keyword(s):  
Cell Growth ◽  
High Glucose ◽  
Transforming Growth Factor ◽  
Human Kidney ◽  
Transforming Growth Factor Β ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Monocyte Chemoattractant Protein 1 ◽  
Ppar Γ ◽  
Proximal Tubular

Peroxisome proliferator-activated receptor-γ (PPAR-γ) are ligand-activated transcription factors that regulate cell growth, inflammation, lipid metabolism, and insulin sensitivity. PPAR-γ in the human kidney has been described. However, the role of PPAR-γ in proximal tubular cells with respect to cell growth and inflammation in diabetic nephropathy is largely unknown. We evaluated the effect of high (30 mM) d-glucose, thiazolidinedione pioglitazone (10 μM), and the selective PPAR-γ agonist L-805645 (8 μM) on PPAR-γ expression, growth, and inflammatory parameters in the proximal tubular model of HK-2 cells. PPAR-γ was present in HK-2 cells and upregulated with 30 mM d-glucose to 177 ± 31.2% of control ( P < 0.05). PPAR-γ activation was induced by pioglitazone to a similar level to that observed by exposure to high glucose but maximally induced by the selective agonist L-805645. However, L-805645 reduced cell viability in both 5 and 30 mM d-glucose to 73.8 ± 3.1 and 77.6 ± 1.4% of control (both P < 0.0001). In parallel, thymidine incorporation was reduced with L-805645 in both 5 and 30 mM d-glucose to 33.3 ± 3.4 and 37.9 ± 2.2%, respectively (both P < 0.0001). Flow cytometry demonstrated increased apoptosis and G1 phase arrest in association with an increase in p21cip1/waf1 in cells exposed to L-805645. Exposure to 30 mM d-glucose did not significantly change AP-1 promoter activity (89.0 ± 5.5% of control); however, the addition of L-805645 significantly reduced it to 62.2 ± 2.7% of control ( P < 0.0001). Thirty nanomolar d-glucose induced transforming growth factor-β1 to 137.7 ± 16.9% of control ( P < 0.05), and L-805645 was able to suppress this to 68.7 ± 5.7% of control ( P < 0.01 vs. d-glucose). Exposure to 30 mM d-glucose reduced monocyte chemoattractant protein 1 levels to 78.6 ± 7.1% ( P < 0.05) of control, with the reduction more marked in the presence of either pioglitazone ( P < 0.01) or L-805645 ( P < 0.01). In summary, high glucose upregulates PPAR-γ and when significantly induced demonstrates anti-proliferative and anti-inflammatory effects.

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