Hif-2α regulates lipid metabolism in alcoholic fatty liver disease through mitophagy.

BACKGROUND: Disordered lipid metabolism plays an essential role in both the initiation and progression of alcoholic fatty liver disease (AFLD), and fatty acid ß-oxidation is increasingly considered as a crucial factor for controlling lipid metabolism. Hif-2α is a member of the Hif family of nuclear receptors, which take part in regulating hepatic fatty acid ß-oxidation. However, its functional role in AFLD and the underlying mechanisms remain unclear. RESULTS: Hif-2α was upregulated in EtOH-fed mice and EtOH-treated AML-12 cells. Inhibition or silencing of Hif-2α led to increased fatty acid ß-oxidation and BNIP3-dependent mitophagy. Downregulation of Hif-2α activates the PPAR-α/PGC-1α signaling pathway, which is involved in hepatic fatty acid ß-oxidation, by mediating BNIP3-dependent mitophagy, ultimately delaying the progression of AFLD. CONCLUSIONS: Hif-2α induces liver steatosis, which promotes the progression of AFLD. Here, we have described a novel Hif-2α-BNIP3-dependent mitophagy regulatory pathway interconnected with EtOH-induced lipid accumulation, which could be a potential therapeutic target for the prevention and treatment of AFLD.

ß-catenin ISGylation promotes lipid deposition and apoptosis in ethanol-stimulated liver injury models.

BACKGROUND: The restoration of the Wnt/ß-catenin pathway to alleviate alcoholic fatty liver disease (AFLD) progression is under study as a new strategy for alcoholic liver disease (ALD) treatment. Recent studies have indicated that interferon-stimulated gene 15 (ISG15) can covalently bind to ß-catenin by HECT E3 ubiquitin ligase 5 (HERC5), leading to ISG degradation and downregulation of ß-catenin levels. However, the relationship between ß-catenin and the ISG15 system in AFLD remains unclear. METHODS: Here, we explored the roles of the ISG15 system in ß-catenin activation and in the pathogenesis of alcohol-induced liver injury and steatosis. RESULTS: In this study, HERC5 silencing upregulated ß-catenin protein expression and inhibited lipid metabolism disorders and cell apoptosis. Reduced ß-catenin protein expression, increased lipid metabolism disorders, and cell apoptosis were detected in cells induced with HERC5 overexpression, which was reversible with the reactive oxygen species (ROS) inhibitor. All the above results were statistically analyzed. Thus, these observations demonstrate that ß-catenin ISGylation is a prominent regulator of ALD pathology, which works by regulating ROS to induce lipid metabolism disorders and cell apoptosis. CONCLUSION: Our findings provided the mechanism involved in the ß-catenin ISGylation, allowing for future studies on the prevention or amelioration of liver injury in ALD.

Bmal1 inhibits phenotypic transformation of hepatic stellate cells in liver fibrosis via IDH1/α-KG-mediated glycolysis.

Hepatic stellate cells (HSCs) play an important role in the initiation and development of liver fibrogenesis, and abnormal glucose metabolism is increasingly being considered a crucial factor controlling phenotypic transformation in HSCs. However, the role of the factors affecting glycolysis in HSCs in the experimental models of liver fibrosis has not been completely elucidated. In this study, we showed that glycolysis was significantly enhanced, while the expression of brain and muscle arnt-like protein-1 (Bmal1) was downregulated in fibrotic liver tissues of mice, primary HSCs, and transforming growth factor-ß1 (TGF-ß1)-induced LX2 cells. Overexpression of Bmal1 in TGF-ß1-induced LX2 cells blocked glycolysis and inhibited the proliferation and phenotypic transformation of activated HSCs. We further confirmed the protective effect of Bmal1 in liver fibrosis by overexpressing Bmal1 from hepatic adeno-associated virus 8 in mice. In addition, we also showed that the regulation of glycolysis by Bmal1 is mediated by the isocitrate dehydrogenase 1/α-ketoglutarate (IDH1/α-KG) pathway. Collectively, our results indicated that a novel Bmal1-IDH1/α-KG axis may be involved in regulating glycolysis of activated HSCs and might hence be used as a therapeutic target for alleviating liver fibrosis.

Rev-erbα exacerbates hepatic steatosis in alcoholic liver diseases through regulating autophagy.

BACKGROUND AND AIMS: Alcoholic fatty liver (AFL) is a liver disease caused by long-term excessive drinking and is characterized by hepatic steatosis. Understanding the regulatory mechanism of steatosis is essential for the treatment of AFL. Rev-erbα is a member of the Rev-erbs family of nuclear receptors, playing an important role in regulating lipid metabolism. However, its functional role in AFL and its underlying mechanism remains unclear. RESULTS: Rev-erbα was upregulated in the liver of EtOH-fed mice and EtOH-treated L-02 cells. Further, Rev-erbα activation exacerbates steatosis in L-02 cells. Inhibition/downexpression of Rev-erbα improved steatosis. Mechanistically, autophagy activity was inhibited in vivo and vitro. Interestingly, inhibition/downexpression of Rev-erbα enhanced autophagy. Furthermore, silencing of Rev-erbα up-regulated the nuclear expression of Bmal1. Autophagy activity was inhibited and steatosis was deteriorated after EtOH-treated L-02 cells were cotransfected with Rev-erbα shRNA and Bmal1 siRNA. CONCLUSIONS: Rev-erbα induces liver steatosis, which promotes the progression of AFL. Our study reveals a novel steatosis regulatory mechanism in AFL and suggest that Rev-erbα might be a potential therapeutic target for AFL.

Bmal1 Regulates Macrophage Polarize Through Glycolytic Pathway in Alcoholic Liver Disease.

Hepatic macrophages play a critical role in inflammation caused by alcohol feeding. During this process, variation of macrophage phenotypes triggers inflammatory responses in a variety of ways. Moreover, there is increasing evidence that Brain and Muscle Arnt-Like Protein-1 (Bmal1) is regarded as a key regulator of macrophage transformation. In our study, Bmal1 was detected to be low expressed in EtOH-fed mice tissue samples and ethanol-induced RAW264.7 cells. After hepatic specific overexpression of Bmal1, M1 macrophage markers were evidently down-regulated, while M2 markers were on the contrary, showing an upward trend. Furthermore, alcoholic liver lesions were also improved in alcohol feeding mice with overexpressed Bmal1. On this basis, we also found that the glycolytic pathway can regulate macrophage polarization. In vitro, blocking of glycolytic pathway can significantly inhibit M1-type polarization. Importantly, glycolysis levels were also restrained after Bmal1 overexpression. What's more, Bmal1 exerts a negative regulatory effect on glycolysis by interacting with S100A9 protein. Further studies showed that the alleviation of alcoholic liver disease (ALD) by Bmal1 was associated with glycolytic pathway suppression and M1 macrophage polarization. In summary, we demonstrated that Bmal1 is a gene capable of relieving ALD, and this effect may provide new insights for altering macrophage phenotypes to regulate inflammatory responses in ALD.

Paeonol derivative-6 attenuates inflammation by activating ZEB2 in acute liver injury.

Paeonol is a natural phenolic compound and isolated as an active ingredient from Moutan Cortex. Paeonol derivative-6 (DPF-6) is a derivative of paeonol improved in water solubility and bioavailability. Previous studies have reported that paeonol possesses a variety of pharmacological activities, such as antioxidant and anti-inflammatory properties. Moreover, we have previously verified that DPF-6 has anti-inflammatory effects. However, the role and fundamental mechanism of DPF-6 in acute liver injury (ALI) was still unclear. In this study, we indicated that DPF-6 inhibited inflammation and the expression of TNF-α, IL-6 and IL-1ß in liver tissues and LPS-mediated L-02 cells, concomitant with the upregulated expression of ZEB2. More importantly, it was demonstrated that overexpression of ZEB2 inhibited the expression level of TNF-α, IL-6 and IL-1ß in LPS-mediated L-02 cells. In contrast, knockdown of ZEB2 increased the expression level of TNF-α, IL-6 and IL-1ß in LPS-mediated L-02 cells. Further studies showed that ZEB2 inhibited the inflammation cytokine secretion via JNK signaling pathway in L-02 cells. Taken together, all the above results indicate that DPF-6 increased the expression of ZEB2, consequently inhibited inflammation cytokine secretion through JNK signaling pathway, which may be utilized as a potential anti-inflammation monomeric compound in the treatment of ALI.