scholarly journals Cytosolic phospholipase A2α and peroxisome proliferator-activated receptor γ signaling pathway counteracts transforming growth factor β-mediated inhibition of primary and transformed hepatocyte growth

Hepatology ◽  
2010 ◽  
Vol 52 (2) ◽  
pp. 644-655 ◽  
Author(s):  
Chang Han ◽  
William C. Bowen ◽  
Guiying Li ◽  
Anthony J. Demetris ◽  
George K. Michalopoulos ◽  
...  
Keyword(s):  
Growth Factor ◽  
Signaling Pathway ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Cytosolic Phospholipase ◽  
Cytosolic Phospholipase A2α ◽  
Hepatocyte Growth

scholarly journals Transforming growth factor β suppresses peroxisome proliferator-activated receptor γ expression via both SMAD binding and novel TGF-β inhibitory elements

2017 ◽  
Vol 474 (9) ◽  
pp. 1531-1546 ◽  
Author(s):  
Sowmya P. Lakshmi ◽  
Aravind T. Reddy ◽  
Raju C. Reddy
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Regulatory Elements ◽  
Nuclear Hormone Receptor ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Context Sensitive ◽  
Signaling Mechanisms ◽  
Target Promoter

Transforming growth factor β (TGF-β) contributes to wound healing and, when dysregulated, to pathological fibrosis. TGF-β and the anti-fibrotic nuclear hormone receptor peroxisome proliferator-activated receptor γ (PPARγ) repress each other's expression, and such PPARγ down-regulation is prominent in fibrosis and mediated, via previously unknown SMAD-signaling mechanisms. Here, we show that TGF-β induces the association of SMAD3 with both SMAD4, needed for translocation of the complex into the nucleus, and the essential context-sensitive co-repressors E2F4 and p107. The complex mediates TGF-β-induced repression by binding to regulatory elements in the target promoter. In the PPARG promoter, we found that the SMAD3–SMAD4 complex binds both to a previously unknown consensus TGF-β inhibitory element (TIE) and also to canonical SMAD-binding elements (SBEs). Furthermore, the TIE and SBEs independently mediated the partial repression of PPARG transcription, the first demonstration of a TIE and SBEs functioning within the same promoter. Also, TGF-β-treated fibroblasts contained SMAD complexes that activated a SMAD target gene in addition to those repressing PPARG transcription, the first finding of such dual activity within the same cell. These findings describe in detail novel mechanisms by which TGF-β represses PPARG transcription, thereby facilitating its own pro-fibrotic activity.

scholarly journals Transforming Growth Factor β Acts as a Regulatory Molecule for Lipogenic Pathways among Hepatitis C Virus Genotype-Specific Infections

2019 ◽  
Vol 93 (18) ◽  
Author(s):  
Tapas Patra ◽  
Reina Sasaki ◽  
Keith Meyer ◽  
Ratna B. Ray ◽  
Ranjit Ray
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Peroxisome Proliferator ◽  
Virus Genotype ◽  
Peroxisome Proliferator Activated Receptor ◽  
Hcv Genotype ◽  
Genotype 1A

ABSTRACT Hepatitis C virus (HCV) infection promotes metabolic disorders, and the severity of lipogenic disease depends upon the infecting virus genotype. Here, we have examined HCV genotype 1-, 2-, or 3-specific regulation of lipid metabolism, involving transforming growth factor β (TGF-β)-regulated phospho-Akt (p-Akt) and peroxisome proliferator-activated receptor alpha (PPARα) axes. Since HCV core protein is one of the key players in metabolic regulation, we also examined its contribution in lipid metabolic pathways. The expression of regulatory molecules, TGF-β1/2, phospho-Akt (Ser473), PPARα, sterol regulatory element-binding protein 1 (SREBP-1), fatty acid synthase (FASN), hormone-sensitive lipase (HSL), and acyl dehydrogenases was analyzed in virus-infected hepatocytes. Interestingly, HCV genotype 3a exhibited much higher activation of TGF-β and p-Akt, with a concurrent decrease in PPARα expression and fatty acid oxidation. A significant and similar decrease in HSL, unlike in HCV genotype 1a, was observed with both genotypes 2a and 3a. Similar observations were made from ectopic expression of the core genomic region from each genotype. The key role of TGF-β was further verified using specific small interfering RNA (siRNA). Together, our results highlight a significant difference in TGF-β-induced activity for the HCV genotype 2a- or 3a-induced lipogenic pathway, exhibiting higher triglyceride synthesis and a decreased lipolytic mechanism. These results may help in therapeutic modalities for early treatment of HCV genotype-associated lipid metabolic disorders. IMPORTANCE Hepatic steatosis is a frequent complication associated with chronic hepatitis C virus (HCV) infection and is a key prognostic indicator for progression to fibrosis and cirrhosis. Several mechanisms are proposed for the development of steatosis, especially with HCV genotype 3a. Our observations suggest that transforming growth factor β (TGF-β) and peroxisome proliferator-activated receptor alpha (PPARα)-associated mechanistic pathways in hepatocytes infected with HCV genotype 2a and 3a differ from those in cells infected with genotype 1a. The results suggest that a targeted therapeutic approach for enhanced PPARα and lipolysis may reduce HCV genotype-associated lipid metabolic disorder in liver disease.

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