Recent progression in the utilization of autophagy-regulating nature compound as anti-liver fibrosis agents

Resveratrol contributes to the inhibition of liver fibrosis by inducing autophagy via the microRNA‑20a‑mediated activation of the PTEN/PI3K/AKT signaling pathway

Liver fibrosis (LF) is a healing response to wounds resulting in liver injury that can cause liver failure or even cancer without functional prevention. Resveratrol (RSV) has been suggested to exert biological effects against various human diseases. MicroRNA-20a (miRNA/miR-20a) has been shown to promote disease progression. The present study aimed to assess the mechanisms through which RSV induces autophagy and activates the miR-20a-mediated phosphatase and tensin homolog (PTEN)/PI3K/AKT signaling pathway in LF. First, a rat model of carbon tetrachlo-ride (CCL₄)-induced LF and a cell model of platelet-derived growth factor (PDGF)-BB-stimulated HSC-T6 cells were established for use in subsequent experiments. Subsequently, RSV at a range of concentrations was injected into the model rats with LF. Indicators related to liver injury, oxidative stress and fibrosis were determined in the rats with LF. The RSV-treated HSC-T6 cells were subjected to transfection with miR-20a mimic and PTEN overexpression plasmid to assess the levels of liver injury and LF. A dual-luciferase reporter gene assay was performed to verify the binding sites between PTEN and miR-20a. RSV was found to alleviate LF in rats, and autophagy was enhanced in the rats with LF following RSV treatment. Furthermore, the activation of the PTEN/PI3K/AKT axis attenuated LF, which was reversed by transfection with miR-20a mimic. RSV reversed the inhibitory effects of miR-20a on PTEN expression, reducing miR-20a expression and promoting PTEN, PI3K and p-AKT protein expression, thus attenuating LF. On the whole, the present study demonstrates that RSV induces autophagy and activates the miR-20a-mediated PTEN/PI3K/AKT signaling pathway to attenuate LF. These findings may lead to the development of potential therapeutic strategies for LF.

[Role of PPAR-γ-regulated autophagy in genistein-induced inhibition of hepatic stellate cell activation]

OBJECTIVE

To investigate the inhibitory effect of genistein on activation of hepatic stellate cells (HSCs) in vitro and the role of the autophagy pathway regulated by PPAR-γ in mediating this effect.

METHODS

Cultured HSC-T6 cells were exposed to different concentrations of genistein for 48 h, and HSC activation was verified by detecting the expressions of -SMA and 1(I) collagen; autophagy activation in the cells was determined by detecting the expressions of LC3-II and p62 using Western blotting. The autophagy inhibitor 3-MA was used to confirm the role of autophagy in genistein-induced inhibition of HSC activation. A PPAR-γ inhibitor was used to explore the role of PPAR-γ in activating autophagy in the HSCs.

RESULTS

Genistein at concentrations of 5 and 50 μmol/L significantly inhibited the expressions of -SMA and 1(I) collagen (P < 0.05), markedly upregulated the expressions of PPAR-γ and the autophagy-related protein LC3-II (P < 0.05) and significantly down-regulated the expression of the ubiqutin-binding protein p62 (P < 0.05) in HSC-T6 cells. The cells pretreated with 3-MA prior to genistein treatment showed significantly increased protein expressions of -SMA and 1(I) collagen compared with the cells treated with genistein only (P < 0.05). Treatment with the PPAR-γ inhibitor obviously lowered the expression of LC3-II and enhanced the expression p62 in genistein-treated HSC-T6 cells, suggesting the activation of the autophagy pathway.

CONCLUSIONS

PPAR-γ- regulated autophagy plays an important role in mediating genistein-induced inhibition of HSC activation in vitro.

SVIP alleviates CCl4-induced liver fibrosis via activating autophagy and protecting hepatocytes

Prolonged parenchymal cell death leads to activation of fibrogenic cells and extracellular matrix accumulation and eventually liver fibrosis. Autophagy, a major catabolic process of intracellular degradation and recycling, participates in hepatic fibrosis. However, the precise role of autophagy in the pathogenesis of hepatic fibrosis is controversial. The present study aims to investigate the key role of small VCP/p97 interacting protein (SVIP) against CCl₄-induced hepatic fibrosis via activating autophagy. Autophagy could be activated by SVIP in HepG2 cells, but starvation cannot increase SVIP expression in vitro and in vivo. Moreover, SVIP expression, in agreement with autophagic activity and the volume of lipid droplets, first increases and then decreases during the progression of liver fibrosis with CCl₄ treatment in vivo and in vivo. Further, overexpression of SVIP can protect HepG2 cells from the toxicity of CCl₄, which could be enhanced by starvation. Finally, starvation keeps SVIP and autophagy at such high levels in the rat livers that markedly delays the progress of hepatic fibrosis. Probably, the protective effect of SVIP is associated with stabilizing nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) and transcription factor EB (TFEB). The current study provides insight into the biological role of SVIP and autophagy in regulating hepatic fibrosis, targeting SVIP might be a novel therapeutic strategy in the future.

Antifibrotic effects of Fraxetin on carbon tetrachloride-induced liver fibrosis by targeting NF-κB/IκBα, MAPKs and Bcl-2/Bax pathways

BACKGROUND

Liver fibrosis is a chronic lesion which ultimately results in cirrhosis and possible death. Although the high incidence and lethality, few therapies are effective for liver fibrosis. Fraxetin (7,8-dihydroxy-6-methoxy coumarin), a natural product extracted from cortex fraxini, has exhibited a significant hepatoprotective and anti-fibrotic properties. However, the underlying mechanism of the anti-hepatic fibrotic property remains unknown.

METHODS

48 Male Sprague Dawley rats were divided into four groups at random which were named as normal group, model group, fraxetin 25 mg/kg and 50 mg/kg group. The experimental model of liver fibrosis was founded by carbon tetrachloride (CCl₄) rats which were simultaneously treated with fraxetin (25 mg/kg or 50 mg/kg). Normal groups received equal volumes of saline and peanut oil.

RESULTS

Results showed that fraxetin ameliorated CCl₄ induced liver damage and fibrosis. Furthermore, histopathology examinations revealed that fraxetin improved the morphology and alleviated collagen deposition in fibrotic liver. Fraxetin inhibited inflammation and hepatocytes apoptosis by modulating the NF-κB/IκBα, MAPKs and Bcl-2/Bax signaling pathways.

CONCLUSION

Our findings indicate that fraxetin is effective in preventing liver fibrosis through inhibiting inflammation and hepatocytes apoptosis which is associated with regulating NF-κB/IκBα, MAPKs and Bcl-2/Bax signaling pathways in rats.

The inhibition of Hippo/Yap signaling pathway is required for magnesium isoglycyrrhizinate to ameliorate hepatic stellate cell inflammation and activation

Liver fibrosis is a reversible pathological process accompanied by abnormal inflammation, and its end-stage cirrhosis is responsible for high morbidity and mortality worldwide. This study was to investigate the effect of Magnesium isoglycyrrhizinate (MgIG) on liver fibrosis and inflammation, and to further clarify molecular mechanism. We found that MgIG treatment significantly alleviated carbon tetrachloride (CCl₄)-induced liver fibrosis and HSC activation by regulating TGF-β signaling and MMP/TIMP systems. In addition, MgIG treatment significantly inhibited the inflammatory response of liver fibrosis in mice characterized by reduced pro-inflammatory factors expression and increased anti-inflammatory factors expression. Interestingly, experiments in vitro also showed that MgIG treatment significantly reduced the expression of hepatic stellate cell (HSC) activation markers. Besides, MgIG treatment not only inhibited the expression of pro-inflammatory factors, but also promoted the production of anti-inflammatory factors in activated HSCs. Importantly, treatment with MgIG inhibited Hippo/Yap signaling pathway, which was a potential mechanism for MgIG-induced anti-inflammatory effects. The overexpression of Hippo/Yap signaling effector YAP completely impaired MgIG-induced anti-inflammatory and anti-fibrotic effects. Taken together, these results provide novel implications to reveal the molecular mechanism of the anti-inflammatory properties induced by MgIG, by which points to the possibility of using MgIG to treat liver fibrosis.

Activation of autophagy is required for Oroxylin A to alleviate carbon tetrachloride-induced liver fibrosis and hepatic stellate cell activation

Liver fibrosis is a reversible pathophysiological process correlated with intense repair and cicatrization mechanisms, and its end-stage cirrhosis is responsible for high morbidity and mortality worldwide. Interestingly, the use of natural products as a realistic option for the treatment of liver fibrosis has broadly been accepted. Oroxylin A, a safe and natural product, shows a wide range of pharmacological activities such as anti-inflammatory, anti-oxidant, and anti-tumor properties. However, the effects of Oroxylin A on liver fibrosis remain poorly understood. In the present study, we sought to determine the effect of Oroxylin A on carbon tetrachloride (CCl₄)-induced liver fibrosis, and to further examine the molecular mechanisms. We found that treatment with Oroxylin A markedly decreased the level of liver injury markers, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), in a dose dependent manner. Moreover, Oroxylin A treatment remarkably inhibited extracellular matrix (ECM) deposition, and significantly down-regulated the mRNA and protein expression of liver fibrosis markers including α1(I)collagen, fibronectin, alpha-smooth muscle actin (α-SMA), PDGF-βR, and TGF-βR1 in CCl₄-induced murine model of liver fibrosis. Furthermore, experimental results in vitro showed that Oroxylin A treatment reduced the mRNA and protein expression of HSC activation markers, α-SMA, desmin, α1 (I) collagen, fibronectin, TGF-β, and TNF-α, in a dose dependent manner. Attractively, Oroxylin A treatment also markedly up-regulated the expression of autophagy makers, LC3-B, Atg3, Atg4, Atg5, Beclin1/Atg6, Atg7, Atg9, ATG12, and Atg14, and apparently reduced the expression of autophagy substrate p62 in both CCl₄-induced murine model of liver fibrosis and PDGF-BB-treated HSCs. Importantly, inhibition of autophagy by specific inhibitor 3-methyladenine (3-MA) completely abolished Oroxylin A-induced anti-fibrosis effect, indicating that activation of autophagy was required for Oroxylin A to alleviate liver fibrosis. Overall, these results provide novel implications to reveal the molecular mechanism of Oroxylin A-induced anti-fibrosis properties, by which points to the possibility of using Oroxylin A for the treatment of liver fibrosis.