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Background and purpose Liver fibrosis is a serious cause of morbidity and mortality worldwide and has no adequate treatment. Accumulating evidence suggests that cannabinoid CB1 receptors regulate a variety of physiological and pathological processes in the liver, and blockage of CB1 receptor signalling shows promise as a new therapy for several liver diseases. The aim of this study was to investigate the potential therapeutic effects of CB1 receptors and a peripheral CB1 receptor antagonist JD5037 in liver fibrogenesis. Experimental approach Liver samples from both humans and mouse models were investigated. The peripheral CB1 receptor antagonist JD5037, β-arr1 wild type (β-arr1-WT) and β-arr1 knockout (β-arr1-KO) littermate models, and primary hepatic stellate cells (HSCs) were also used. The mechanisms underlying CB1 receptor-regulated HSCs activation in fibrosis and the therapeutic potential of JD5037 were further analysed. Key results CB1 receptors were induced in samples from patients with liver fibrosis and from mouse models. These receptors promoted activation of HSCs in liver fibrosis via recruiting β-arrestin1 and Akt signalling, while blockage of CB1 receptors with JD5037 attenuated CB1 receptor-regulated HSCs activation and liver fibrosis by suppressing β-arrestin1/Akt signalling. Conclusions and implications CB1 receptors promote the activation of HSCs and liver fibrosis via the β-arrestin1/Akt signalling pathway. The peripheral CB1 receptor antagonist JD5037 blocked this pathway, the activation of HSCs and liver fibrosis. This compound and the associated pathway may be a novel approach to the treatment of liver fibrosis.

Background: Mucosal epithelial apoptosis with non-specific inflammation is an essential pathological characteristic in portal hypertensive gastropathy (PHG). However, whether a coordinated crosstalk between myeloid cells and epithelial cells involved in PHG remains unclear. Methods: Gastric injury and mucosal apoptosis were examined in patients with PHG and the PHG model of p65ΔM/ΔM (myeloid cells specific NF-κBp65 deletion) and p65f/f (floxed p65) mice, PUMA-WT (PUMA wild-type) and PUMA-KO (PUMA knockout) mice. The interaction of IL-6, Fas, FasL, NF-κBp65 and PUMA expression was investigated, and the mechanisms underlying IL-6-regulated gastric epithelial apoptosis were analysed. Findings: IL-6, which is induced in the mucosa of PHG patients and mice, promotes FasL production via enhancing NF-κBp65 activation in myeloid cells, while blockage of IL-6 signaling by Tocilizumab or deletion of NF-κBp65 in myeloid cells attenuates the inflammatory response and Fas/FasL-mediated epithelial apoptosis in PHG. IL-6-driven FasL from myeloid cells combines with epithelial Fas receptor to encourage NF-κBp65/PUMA-mediated epithelial apoptosis in PHG, and inhibition of NF-κBp65 or knockout of PUMA dramatically alleviates Fas/FasL network-mediated epithelial apoptosis in PHG. Interpretation: These results indicate that IL-6 drives FasL generation via NF-κBp65 in myeloid cells to promote Fas/NF-κBp65/PUMA-mediated epithelial apoptosis in PHG. Funding: This work was supported by grants from the National Natural Science Foundation of China (U1501224, 81700536), the Natural Science Foundation Team Project of Guangdong Province (2018B03031200), the Science and Technology Developmental Special Foundation of Guangdong Province (2017B020226003), the Basic Research Programme of Young Teachers' Training Project of Sun Yat-sen University (17ykpy51), the Science and Technology Planning Projects of Guangzhou City (201604020118, 201604020002). Declaration of Interest: The authors declare that there are no conflicts of interest. Ethical Approval: The study protocol and the acquisition of the tissue samples were approved by the Institutional Review Board of The Third Affiliated Hospital of Sun Yat-Sen University.

BACKGROUND AND PURPOSE: Liver fibrosis is a serious cause of morbidity and mortality worldwide and has no adequate treatment. Accumulating evidence suggests that cannabinoid CB(1) receptors regulate a variety of physiological and pathological processes in the liver, and blockage of CB(1) receptor signalling shows promise as a new therapy for several liver diseases. The aim of this study was to investigate the potential therapeutic effects of CB(1) receptors and a peripheral CB(1) receptor antagonist JD5037 in liver fibrogenesis. EXPERIMENTAL APPROACH: Liver samples from both humans and mouse models were investigated. The peripheral CB(1) receptor antagonist JD5037, β‐arr1 wild type (β‐arr1‐WT) and β‐arr1 knockout (β‐arr1‐KO) littermate models, and primary hepatic stellate cells (HSCs) were also used. The mechanisms underlying CB(1) receptor‐regulated HSCs activation in fibrosis and the therapeutic potential of JD5037 were further analysed. KEY RESULTS: CB(1) receptors were induced in samples from patients with liver fibrosis and from mouse models. These receptors promoted activation of HSCs in liver fibrosis via recruiting β‐arrestin1 and Akt signalling, while blockage of CB(1) receptors with JD5037 attenuated CB(1) receptor‐regulated HSCs activation and liver fibrosis by suppressing β‐arrestin1/Akt signalling. CONCLUSIONS AND IMPLICATIONS: CB(1) receptors promote the activation of HSCs and liver fibrosis via the β‐arrestin1/Akt signalling pathway. The peripheral CB(1) receptor antagonist JD5037 blocked this pathway, the activation of HSCs and liver fibrosis. This compound and the associated pathway may be a novel approach to the treatment of liver fibrosis.

It is generally accepted that ATP regulates mitochondrial function through the AMPK signaling pathway. However, the AMPK-independent pathway remains largely unknown. In this study, we investigated ATP surplus in the negative regulation of mitochondrial function with a focus on pyruvate dehydrogenase (PDH) phosphorylation and protein acetylation. PDH phosphorylation was induced by a high fat diet in the liver of obese mice, which was associated with ATP elevation. In 1c1c7 hepatoma cells, the phosphorylation was induced by palmitate treatment through induction of ATP production. The phosphorylation was associated with a reduction in mitochondria oxygen consumption after 4 h treatment. The palmitate effect was blocked by etomoxir, which inhibited ATP production through suppression of fatty acid β-oxidation. The PDH phosphorylation was induced by incubation of mitochondrial lysate with ATP in vitro without altering the expression of PDH kinase 2 (PDK2) and 4 (PDK4). In addition, acetylation of multiple mitochondrial proteins was induced by ATP in the same conditions. Acetyl-CoA exhibited a similar activity to ATP in induction of the phosphorylation and acetylation. These data suggest that ATP elevation may inhibit mitochondrial function through induction of the phosphorylation and acetylation of mitochondrial proteins. The results suggest an AMPK-independent mechanism for ATP regulation of mitochondrial function.

G-protein-coupled receptors (GPCR) constitute the largest known superfamily for signal transduction and transmission, and they control a variety of physiological and pathological processes. GPCR adaptor β-arrestins (ARRBs) play a role in cancerous proliferation. However, the effect of ARRBs in inflammation-mediated hepatocellular carcinogenesis is unknown. Here we show that ARRB1, but not ARRB2, is upregulated in inflammation-associated hepatocellular carcinoma (HCC) and paracancerous tissues in humans. A genotoxic carcinogen, diethylnitrosamine (DEN), significantly induces hepatic inflammation, TNF-α production and ARRB1 expression. Although ARRB1 deficiency does not affect hepatic inflammation and TNF-α production, it markedly represses hepatocellular carcinogenesis by suppressing malignant proliferation in DEN-treated mice. Furthermore, TNF-α directly induces hepatic ARRB1 expression and enhances ARRB1 interaction with Akt by binding to boost Akt phosphorylation, resulting in malignant proliferation of liver cells. Our data suggest that ARRB1 enhances hepatocellular carcinogenesis by inflammation-mediated Akt signalling and that ARRB1 may be a potential therapeutic target for HCC.

Insulin degrading enzyme (IDE) is a potential drug target in the treatment of type 2 diabetes (T2D). IDE controls circulating insulin through a degradation-dependent clearance mechanism in multiple tissues. However, there is not sufficient information about IDE regulation in obesity. In this study, we test obesity-associated factors and pioglitazone in the regulation of IDE in diet-induced obese (DIO) C57BL/6 mice. The enzyme activity and protein level of IDE were increased in the liver of DIO mice. Pioglitazone (10 mg/kg/day) administration for 2 months significantly enhanced the enzyme activity (75%), protein (180%) and mRNA (100%) of IDE in DIO mice. The pioglitazone-induced changes were coupled with 50% reduction in fasting insulin and 20% reduction in fasting blood glucose. The mechanism of IDE regulation in liver was investigated in the mouse hepatoma cell line (Hepa 1c1c7 cells), in which pioglitazone (5 µM) increased IDE protein and mRNA in a time-dependent manner in an 8 h study. Free fatty acid (palmitate 300 µM) induced IDE protein, but reduced the mRNA. Glucagon induced, and TNF-α decreased IDE protein. Insulin did not exhibit any activity in the same condition. In summary, pioglitazone, FFA and glucagon directly increased, but TNF-α decreased the IDE activity in hepatocytes. The results suggest that IDE activity is regulated in liver by multiple factors in obesity and pioglitazone may induce IDE activity in the control of T2D.