Emodin suppresses activation of hepatic stellate cells through p38 mitogen‐activated protein kinase and Smad signaling pathways in vitro

• Published in: Phytotherapy research Vol. 32; no. 12; pp. 2436 - 2446
• Main Authors: Wang, Xiaoli, Niu, Chengu, Zhang, Xiaojie, Dong, Miaoxian
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.12.2018
• Subjects: Actin; Activation; Animals; Cell Proliferation - drug effects; Cells, Cultured; Collagen; Collagen (type I); Collagen Type I - metabolism; Deprivation; Emodin; Emodin - pharmacology; Extracellular matrix; Fibronectin; Fibronectins - metabolism; Fibrosis; Gene expression; Growth factors; HEK293 Cells; hepatic stellate cells; Hepatic Stellate Cells - drug effects; Hepatic Stellate Cells - metabolism; Humans; Inhibition; Intracellular signalling; JNK protein; Kinases; Liver; MAP Kinase Signaling System - drug effects; Muscles; p38 Mitogen-Activated Protein Kinases - metabolism; p38MAPK; Phosphorylation; Phosphorylation - drug effects; Protein kinase; Proteins; Rats; Ribonucleic acid; RNA; Signal transduction; Signal Transduction - drug effects; Smad; Smad protein; Smad Proteins - metabolism; Smad4 protein; Smooth muscle; Stellate cells; Transcription; Transforming growth factor; Transforming Growth Factor beta - pharmacology; transforming growth factor β1; Transforming growth factor-b1; hepatic stellate cells; Smad; transforming growth factor β1; p38MAPK; emodin
• ISSN: 0951-418X; 1099-1573
• DOI: 10.1002/ptr.6182

The aim of this study was to evaluate the hypothesis that emodin inhibits extracellular matrix (ECM)‐related gene expression in activated hepatic stellate cells (HSCs) by blocking canonical or/and noncanonical components of transforming growth factor β1 (TGFβ1) intracellular signaling. Here, we demonstrate that emodin suppressed the gene expression of HSCs activation markers type I collagen, fibronectin, and α‐smooth muscle actin, as well as HSCs proliferation. Mechanistically, emodin suppresses TGFβ1, TGFβ receptor II, TGFβ receptor I, and Smad4 gene expression, as well as Smad luciferase activity. Simultaneously, emodin reduced p38 mitogen‐activated protein kinase (p38MAPK) activity but not c‐Jun N‐terminal kinases and extracellular signal‐regulated kinases 1 and 2 phosphorylation in HSC‐T6 cells. Interestingly, deprivation of TGFβ using a neutralizing antibody abolished emodin‐mediated inhibitions of the both Smad transcriptional activity and p38MAPK phosphorylation. Furthermore, emodin‐mediated inhibition of HSCs activation could be partially blocked by PD98059 inhibition of p38MAPK or short hairpin RNA‐imposed knockdown of Smad4. Conversely, simultaneous inhibition of Smad4 and p38MAPK pathways completely reverses the effects of emodin, suggesting that Smad and p38MAPK locate downstream of TGFβ1 and regulate collagen genes expression in HSCs. Collectively, these data suggest that emodin is a promising candidate for the treatment of hepatic fibrosis.