Targeting GPR65 alleviates hepatic inflammation and fibrosis by suppressing the JNK and NF-κB pathways

Background:G-protein coupled receptors(GPCRs)are recognized as attractive targets for drug therapy.However,it remains poorly understood how GPCRs,except for a few chemokine receptors,regulate the progression of liver fibrosis.Here,we aimed to reveal the role of GPR65,a proton-sensing receptor,in liver fibrosis and to elucidate the underlying mechanism.Methods:The expression level of GPR65 was evaluated in both human and mouse fibrotic livers.Furthermore,Gpr65-deficient mice were treated with either bile duct ligation(BDL)for 21 d or carbon tetrachloride(CCl4)for 8 weeks to investigate the role of GPR65 in liver fibrosis.A combination of experimental approaches,including Western blotting,quantitative real-time reverse transcription-polymerase chain reaction(qRT-PCR),and enzyme-linked immunosorbent assay(ELISA),confocal microscopy and rescue studies,were used to explore the underlying mechanisms of GPR65’s action in liver fibrosis.Additionally,the therapeutic potential of GPR65 inhibitor in the development of liver fibrosis was investigated.Results:We found that hepatic macrophage(HM)-enriched GPR65 was upregulated in both human and mouse fibrotic livers.Moreover,knockout of Gpr65 significantly alleviated BDL-and CCl4-induced liver inflammation,injury and fibrosis in vivo,and mouse bone marrow transplantation(BMT)experiments further demonstrated that the protective effect of Gpr65knockout is primarily mediated by bone marrow-derived macrophages(BMMs).Additionally,in vitro data demonstrated that Gpr65 silencing and GPR65 antagonist inhibited,while GPR65 overexpression and application of GPR65 endogenous and exogenous agonists enhanced the expression and release of tumor necrosis factor-α(TNF-α),interleukin-6(IL-6)and transforming growth factor-β(TGF-β),all of which subsequently promoted the activation of hepatic stellate cells(HSCs)and the damage of hepatocytes(HCs).Mechanistically,GPR65 overexpression,the acidic pH and GPR65 exogenous agonist induced up-regulation of TNF-αand IL-6 via the Gαq-Ca^(2+)-JNK/NF-κB pathways,while promoted the expression of TGF-βthrough the Gαq-Ca^(2+)-MLK3-MKK7-JNK pathway.Notably,pharmacological GPR65 inhibition retarded the development of inflammation,HCs injury and fibrosis invivo.Conclusions:GPR65 is a major regulator that modulates the progression of liver fibrosis.Thus,targeting GPR65 could be an effective therapeutic strategy for the prevention of liver fibrosis.

Hepatic macrophages in drug-induced liver injury

Drug-induced liver injury(DILI)is a major public health concern.Intrinsic DILI,for example,acetaminophen overdose accounts for half of acute liver failure in the United States.However,the most problematic type of DILI affecting drug development and health care is idiosyncratic DILI,which occurs unpredictably in a small population of patients taking the drug and the latency could be several weeks to months.Recent knowledge on the pathogenesis of DILI suggest that hepatic macrophages play a central role in the initiation,progression and restoration stages of DILI,which make hepatic macrophages attractive as therapeutic targets.Hepatic macrophages consist of liver resident macrophages(also known as Kupffer cells,KCs)and infiltrating monocyte-derived macrophages(MoMF).There is a growing appreciation that hepatic macrophage is very plastic,and assumes diverse phenotypes and functions in response to micro-environmental cues.In this review,we will summarize studies on the role of hepatic macrophages in both intrinsic DILI and idiosyncratic DILI,followed by discussing the prognostic and therapeutic potentials of targeting hepatic macrophages and the obstacles in studying hepatic macrophages.

Pentoxifylline Inhibits Liver Fibrosis via Hedgehog Signaling Pathway

Infection of schistosomiasis japonica may eventually lead to liver fibrosis, and no effective antifibrotic therapies are available but liver transplantation. Hedgehog（HH） signaling pathway has been involved in the process and is a promising target for treating liver fibrosis. This study aimed to explore the effects of pentoxifylline（PTX） on liver fibrosis induced by schistosoma japonicum infection by inhibiting the HH signaling pathway. Phorbol12-myristate13-acetate（PMA） was used to induce human acute mononuclear leukemia cells THP-1 to differentiate into macrophages. The THP-1-derived macrophages were stimulated by soluble egg antigen（SEA）, and the culture supernatants were collected for detection of activation of macrophages. Cell Counting Kit-8（CCK-8） was used to detect the cytotoxicity of the culture supernatant and PTX on the LX-2 cells. The LX-2 cells were administered with activated culture supernatant from macrophages and（or） PTX to detect the transforming growth factor-β gene expression. The m RNA expression of shh and gli-1, key parts in HH signaling pathway, was detected. The m RNA expression of shh and gli-1 was increased in LX-2 cells treated with activated macrophages-derived culture supernatant, suggesting HH signaling pathway may play a key role in the activation process of hepatic stellate cells（HSCs）. The expression of these genes decreased in LX-2 cells co-cultured with both activated macrophages-derived culture supernatant and PTX, indicating PTX could suppress the activation process of HSCs. In conclusion, these data provide evidence that PTX prevents liver fibrogenesis in vitro by the suppression of HH signaling pathway.

A pilot study on the combined therapy of granulocyte-macrophage colony-stimulating factor and hepatitis B vaccine on chronic hepatitis B virus carrier children

Objective To observe the efficacy of treating intrauterine infected chronic hepatitis B virus (HBV) carrier children with a combination of granulocyte macrophage colony stimulating factor (GM CSF) or hepatitis B immunoglobulin (HBIG) plus recombinant hepatitis B vaccine (rHBvac) Methods A total of 27 chronic HBV infected children, who were born to HBV carrier mothers and received hepatitis B immunoprophylaxis at birth, were randomized into 2 groups: one receiving a combined therapy of 50 μg of GM CSF plus 10 μg of rHBvac injected intramuscularly at the same location (GM CSF group, 14 children) or 200 IU HBIG and 10 μg rHBvac in different muscles (HBIG group, 13 children) on a monthly four dose schedule HBV DNA quantification and other HBV serological markers were tested before and after the four dose therapy Results Twelve children in each group completed the study Of them, 3 children in the GM CSF group and 4 in the HBIG group had elevated serum alanine transaminase (ALT) before the trial, and then 2 in each group became ALT normal after the treatment Before the therapy, hepatitis B e antigen (HBeAg) positivity was found in nine children in the GM CSF group and 10 in the HBIG group One from each group had an HBeAg/anti HBe seroconversion after the treatment The quantity of HBV DNA was significantly lower after the treatment ( P =0 023) in GM CSF group, but was not significantly reduced in HBIG group No subjects were found to be negative for hepatitis B surface antigen (HBsAg) after the treatment, and no serious adverse events occurred in either group Conclusion Combined GM CSF and rHBvac therapy inhibit HBV replication in carrier children who were not protected after treatment with immunoprophylaxis