Activation of farnesoid X receptor induces RECK expression in mouse liver

FXR agonists INT-787 and OCA increase RECK and inhibit liver steatosis and inflammation in diet-induced ob/ob mouse model of NASH

BACKGROUND AND AIMS

We have previously shown in a model of hepatic ischaemia/reperfusion injury that the farnesoid X receptor (FXR) agonist obeticholic acid (OCA) restores reversion-inducing-cysteine-rich protein with Kazal motifs (RECK), an inverse modulator of metalloproteases (MMPs) and inhibitor of the sheddases ADAM10 and ADAM17 involved in inflammation and fibrogenesis. Here, the effects of FXR agonists OCA and INT-787 on hepatic levels of RECK, MMPs, ADAM10 and ADAM17 were compared in a diet-induced ob/ob mouse model of non-alcoholic steatohepatitis (NASH).

METHODS

Lep ob/ob NASH mice fed a high-fat diet (HFD) or control diet (CD) for 9 weeks (wks) were treated with OCA or INT-787 0.05% dosed via HFD admixture (30 mg/kg/day) or HFD for further 12 wks. Serum alanine transaminase (ALT) and inflammatory cytokines, liver RECK, MMP-2 and MMP-9 activity as well as ADAM10, ADAM17, collagen deposition (Sirius red), hepatic stellate cell activation (α-SMA) and pCK+ reactive biliary cells were quantified.

RESULTS

Only INT-787 significantly reduced serum ALT, IL-1β and TGF-β. A downregulation of RECK expression and protein levels observed in HFD groups (at 9 and 21 wks) was counteracted by both OCA and INT-787. HFD induced a significant increase in liver MMP-2 and MMP-9; OCA administration reduced both MMP-2 and MMP-9 while INT-787 markedly reduced MMP-2 expression. OCA and INT-787 reduced both ADAM10 and ADAM17 expression and number of pCK+ cells. INT-787 was superior to OCA in decreasing collagen deposition and α-SMA levels.

CONCLUSION

INT-787 is superior to OCA in controlling specific cell types and clinically relevant anti-inflammatory and antifibrotic molecular mechanisms in NASH.

Recent Updates on the Therapeutic Prospects of Reversion-Inducing Cysteine-Rich Protein with Kazal Motifs (RECK) in Liver Injuries

The reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a membrane-anchored glycoprotein, negatively regulates various membrane proteins involved in the tissue governing extracellular matrix (ECM) remodeling such as metalloproteases (MMPs) and the sheddases ADAM10 and ADAM17. The significance of the present review is to summarize the current understanding of the pathophysiological role of RECK, a newly discovered signaling pathway associated with different liver injuries. Specifically, this review analyzes published data on the downregulation of RECK expression in hepatic ischemia/reperfusion (I/R) injury, liver-related cancers, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), as well as in the progression of nonalcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH). In addition, this review discusses the regulation of RECK by inducers, such as FXR agonists. The RECK protein has also been suggested as a potential diagnostic and prognostic marker for liver injury or as a biomarker with predictive value for drug treatment efficacy.

FXR agonist GW4064 enhances anti-PD-L1 immunotherapy in colorectal cancer

Colorectal cancer (CRC) is one of the top three malignant tumors in terms of morbidity, and the limited efficacy of existing therapies urges the discovery of potential treatment strategies. Immunotherapy gradually becomes a promising cancer treatment method in recent decades; however, less than 10% of CRC patients could really benefit from immunotherapy. It is pressing to explore the potential combination therapy to improve the immunotherapy efficacy in CRC patients. It is reported that Farnesoid X receptor (FXR) is deficiency in CRC and associated with immunity. Herein, we found that GW4064, a FXR agonist, could induce apoptosis, block cell cycle, and mediate immunogenic cell death (ICD) of CRC cells in vitro. Disappointingly, GW4064 could not suppress the growth of CRC tumors in vivo. Further studies revealed that GW4064 upregulated PD-L1 expression in CRC cells via activating FXR and MAPK signaling pathways. Gratifyingly, the combination of PD-L1 antibody with GW4064 exhibited excellent anti-tumor effects in CT26 xenograft models and increased CD8+ T cells infiltration, with 33% tumor bearing mice cured. This paper illustrates the potential mechanisms of GW4064 to upregulate PD-L1 expression in CRC cells and provides important data to support the combination therapy of PD-L1 immune checkpoint blockade with FXR agonist for CRC patients.

Reversion inducing cysteine rich protein with Kazal motifs and cardiovascular diseases: The RECKlessness of adverse remodeling

The Reversion Inducing Cysteine Rich Protein With Kazal Motifs (RECK) is a glycosylphosphatidylinositol (GPI) anchored membrane-bound regulator of matrix metalloproteinases (MMPs). It is expressed throughout the body and plays a role in extracellular matrix (ECM) homeostasis and inflammation. In initial studies, RECK expression was found to be downregulated in various invasive cancers and associated with poor prognostic outcome. Restoring RECK, however, has been shown to reverse the metastatic phenotype. Downregulation of RECK expression is also reported in non-malignant diseases, such as periodontal disease, renal fibrosis, and myocardial fibrosis. As such, RECK induction has therapeutic potential in several chronic diseases. Mechanistically, RECK negatively regulates various matrixins involved in cell migration, proliferation, and adverse remodeling by targeting the expression and/or activation of multiple MMPs, A Disintegrin And Metalloproteinase Domain-Containing Proteins (ADAMs), and A Disintegrin And Metalloproteinase With Thrombospondin Motifs (ADAMTS). Outside of its role in remodeling, RECK has also been reported to exert anti-inflammatory effects. In cardiac diseases, for example, it has been shown to counteract several downstream effectors of Angiotensin II (Ang-II) that play a role in adverse cardiac and vascular remodeling, such as Interleukin-6 (IL-6)/IL-6 receptor (IL-6R)/glycoprotein 130 (IL-6 signal transducer) signaling and Epidermal Growth Factor Receptor (EGFR) transactivation. This review article focuses on the current understanding of the multifunctional effects of RECK and how its downregulation may contribute to adverse cardiovascular remodeling.

The Role of RECK in Hepatobiliary Neoplasia Reveals Its Therapeutic Potential in NASH

Non-alcoholic fatty liver disease (NAFLD) is a multimorbidity disorder ranging from excess accumulation of fat in the liver (steatosis) to steatohepatitis (NASH) and end-stage cirrhosis, and the development of hepatocellular carcinoma (HCC) in a subset of patients. The defining features of NASH are inflammation and progressive fibrosis. Currently, no pharmaceutical therapies are available for NAFLD, NASH and HCC; therefore, developing novel treatment strategies is desperately needed. Reversion Inducing Cysteine Rich Protein with Kazal motifs (RECK) is a well-known modifier of the extracellular matrix in hepatic remodeling and transition to HCC. More recently, its role in regulating inflammatory and fibrogenic processes has emerged. Here, we summarize the most relevant findings that extend our current understanding of RECK as a regulator of inflammation and fibrosis, and its induction as a potential strategy to blunt the development and progression of NASH and HCC.

Obeticholic acid reduces biliary and hepatic matrix metalloproteinases activity in rat hepatic ischemia/reperfusion injury

Background

We have previously shown that obeticholic acid (OCA) upregulates the biliary excretion of asymmetric dimethylarginine (ADMA), an inhibitor of iNOS regulating the activity of matrix metalloproteinases (MMPs). Here, the effects of OCA on MMP-2 and MMP-9 activity in liver, bile and serum were evaluated after hepatic ischemia/reperfusion (I/R) injury.

Material and methods

Male Wistar rats (n = 20) were orally administered 10 mg/kg/day of OCA (5 days) and subjected to a 60-min ischemia and 60-min reperfusion. Bile, serum and tissue were collected for MMP-2 and MMP-9 activity quantification. The MMP regulator tissue reversion-inducing cysteine rich protein with Kazal motifs (RECK), tissue inhibitor of metalloproteinases (TIMPs), iNOS and biliary levels of LDH, γGT, glucose and ADMA were quantified.

Results

In the I/R group, OCA administration reduced MMP-2 and MMP-9 in liver, bile and serum. A downregulation of tissue RECK and TIMPs, observed under I/R, were recovered by OCA. Immunohistochemical staining of hepatic tissue demonstrated that RECK expression is mainly localized in both cholangiocytes and hepatocytes. Hepatic iNOS positively correlated with tissue MMP-2 and MMP-9 activity. Biliary levels of LDH, γGT and glucose were lower in I/R rats treated with OCA; in bile, MMP levels positively correlated with LDH and γGT.

Conclusion

Thus, OCA administration confers protection to cholangiocytes via downregulation of biliary MMPs in livers submitted to I/R. This event is associated with hepatic RECK- and TIMP-mediated MMP decrease.

Farnesoid X receptor associates with β-catenin and inhibits its activity in hepatocellular carcinoma

The association between the temporal activation of Wnt/β-catenin pathway and the spontaneous hepatocellular carcinoma (HCC) development in Farnesoid X receptor (FXR) knockout mice is not well understood. We found that Huh7 cells depleted with FXR by RNAi showed enhanced cell growth, migration and invasion in vitro and accelerated tumor xenografts formation in nude mice. And these phenotypes were attenuated by simultaneous knockdown of β-catenin with RNAi. Furthermore, we identified that FXR could bind with β-Catenin through AF1 domain, and disrupt the assembly of the core β-Catenin/TCF4 complex. Activation of FXR attenuated the DNA-binding activity of β-Catenin/TCF4, and subsequently, its targeting gene-cyclin D1 expression. Importantly, FXR expression was markedly reduced in human HCC, an event which correlated with aberrant activation of β-Catenin. These data identified FXR as a negative regulator of HCC development through direct suppression of Wnt/β-catenin pathway.

Recent insights into farnesoid X receptor in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and is one of the most prevalent liver disorders worldwide. NAFLD can gradually progress to liver inflammation, fibrosis, cirrhosis and even hepatocellular carcinoma. However, the pathogenesis of NAFLD is complex, and no efficient pharmaceutic treatments have yet been established for NAFLD. Accumulating data have shown that the farnesoid X receptor (FXR) plays important roles not only in bile acid metabolism, but also in lipid and carbohydrate homeostasis, inflammatory responses, among others. In this review, we aim to highlight the role of FXR in the pathogenesis and treatment of NAFLD.

Adiponectin is expressed in the pancreas of high-fat-diet-fed mice and protects pancreatic endothelial function during the development of type 2 diabetes

AIM

Adiponectin levels in skeletal muscle and adipose tissue have been reported to be involved in insulin resistance in rats fed with a high-fat diet (HFD). Our objective was to explore whether adiponectin is also expressed in the pancreas and what its potential role is during the development of type 2 diabetes (T2D) in outbred CD-1 mice.

METHODS

Male 4-week-old outbred CD-1 mice were fed an HFD to induce a polygenic model of human T2D. Adiponectin expression was examined in mouse pancreas by quantitative real-time polymerase chain reaction (qPCR), western blots and immunofluorescence analyses. Human umbilical vein endothelium cells (HUVECs) were transfected with an adiponectin-expressing lentivirus to determine the effect of adiponectin on angiogenic function in vitro.

RESULTS

Feeding mice an HFD for 9weeks resulted in constant hyperglycaemia, obesity, impaired glucose tolerance and insulin resistance. Additional hyperinsulinaemia emerged in mice fed an HFD for 18weeks. Interestingly, aberrant expression of adiponectin was detectable in the pancreatic vascular endothelial cells (VECs) of mice fed with an HFD, but not in mice fed with regular chow (RC). Expression levels of pancreatic adiponectin varied during the development of T2D. This extraordinary expression of adiponectin in pancreatic VECs played a role in protecting endothelial function against potential damage by HFD. Our in vitro study has demonstrated that adiponectin promotes angiogenic function.

CONCLUSION

These results reveal for the first time that adiponectin is expressed in pancreatic VECs of HFD-fed mice during the development of T2D as a protective adaptation in response to the HFD.