Citations

Nonalcoholic steatohepatitis (NASH) is a lipotoxic disorder, wherein proinflammatory lipids, such as ceramide and its derivative sphingosine 1-phosphate (S1P), contribute to macrophage-associated liver inflammation. For example, we have previously demonstrated a role for S1P in steatotic hepatocyte-derived S1P-enriched extracellular vesicles in macrophage chemotaxis in vitro. Therefore, we hypothesized that FTY720, an S1P antagonist, would ameliorate NASH by inhibiting proinflammatory monocyte chemotaxis. To test our hypothesis, NASH was established in C57BL/6 male mice by feeding a diet high in fructose, saturated fat, and cholesterol for 22 wk. Then mice received daily intraperitoneal injections of FTY720 for 2 wk before analysis of liver injury, inflammation, and fibrosis. FTY720-treated mice with NASH demonstrated improved liver histology with a significant reduction in hepatocyte ballooning and inflammatory foci. Hepatomegaly was reversed, and liver triglycerides were reduced following FTY720 administration to mice with NASH. Correspondingly, serum ALT levels, hepatic inflammatory macrophage accumulation, and the expression of Ly6C in recruited myeloid cells was reduced in FTY720-treated mice. Hepatic collagen accumulation and expression of α-smooth muscle actin were significantly lowered as well. Body composition, energy consumption and utilization, and hepatic sphingolipid composition remained unchanged following FTY720 administration. FTY720 ameliorates murine nonalcoholic steatohepatitis. Reduction in liver injury and inflammation is associated with a reduction in hepatic macrophage accumulation, likely due to dampened recruitment of circulating myeloid cells into the liver. Nonalcoholic steatohepatitis may be a novel indication for the therapeutic use of FTY720. NEW & NOTEWORTHY There are no approved pharmacologic therapies for nonalcoholic steatohepatitis (NASH), the leading cause of chronic liver disease worldwide. This study describes the use of FTY720, a novel small molecule, for the amelioration of NASH in a mouse model. We demonstrate that 2-wk administration of FTY720 to mice with NASH led to a reduction in liver injury, inflammation, and fibrosis. These data provide a preclinical rationale for studying this drug in human NASH.

Extracellular vesicles (EVs) are nanometer‐sized, membrane‐bound vesicles released by cells into the extracellular milieu. EVs are now recognized to play a critical role in cell‐to‐cell communication. EVs contain important cargo in the form of proteins, lipids, and nucleic acids and serve as vectors for delivering this cargo from donor to acceptor or target cell. EVs are released under both physiologic and pathologic conditions, including liver diseases, and exert a wide range of effects on target cells. This review provides an overview on EV biogenesis, secretion, cargo, and target cell interactions in the context of select liver diseases. Specifically, the diverse roles of EVs in nonalcoholic steatohepatitis, alcoholic liver disease, viral hepatitis, cholangiopathies, and hepatobiliary malignancies are emphasized. Liver diseases often result in an increased release of EVs and/or in different cargo sorting into these EVs. Either of these alterations can drive disease pathogenesis. Given this fact, EVs represent a potential target for therapeutic intervention in liver disorders. Because altered EV composition may reflect the underlying disease condition, circulating EVs can be exploited for diagnostic and prognostic purposes as a liquid biopsy. Furthermore, ex vivo modified or synthesized EVs can be engineered as therapeutic nano‐shuttles. Finally, we highlight areas that merit further investigation relevant to understanding how EVs regulate liver disease pathogenesis. (H epatology 2016;64:2219‐2233).

3-Aminorhodanine reacts with aldehydes to form either 5-[(aryl)alkylidene]-substituted products or Schiff bases or derivatives substituted at both the 3-amino group and the 5-methylene group, depending on the reaction conditions. In this note, synthesis and characterization of 3-amino-5-(pyridin-2-ylmethylidene)-2-thioxo-1,3-thiazolidin-4-one is reported.

Mixed lineage kinase 3 (MLK3) deficiency reduces macrophage‐associated inflammation in a murine model of nonalcoholic steatohepatitis (NASH). However, the mechanistic links between MLK3 activation in hepatocytes and macrophage‐driven inflammation in NASH are uncharted. Herein, we report that MLK3 mediates the release of (C‐X‐C motif) ligand 10 (CXCL10)‐laden extracellular vesicles (EVs) from lipotoxic hepatocytes, which induce macrophage chemotaxis. Primary mouse hepatocytes (PMHs) and Huh7 cells were treated with palmitate or lysophosphatidylcholine (LPC). Released EVs were isolated by differential ultracentrifugation. LPC treatment of PMH or Huh7 cells induced release of EVs, which was prevented by either genetic or pharmacological inhibition of MLK3. Mass spectrometry identified the potent chemokine, CXCL10, in the EVs, which was markedly enriched in EVs isolated from LPC‐treated hepatocytes versus untreated cells. Green fluorescent protein (GFP)‐tagged CXCL10 was present in vesicular structures and colocalized with the red fluorescent protein (RFP)‐tagged EV marker, CD63, after LPC treatment of cotransfected Huh‐7 cells. Either genetic deletion or pharmacological inhibition of MLK3 prevented CXCL10 enrichment in EVs. Treatment of mouse bone‐marrow–derived macrophages with lipotoxic hepatocyte‐derived EVs induced macrophage chemotaxis, an effect blocked by incubation with CXCL10‐neutralizing antisera. MLK3‐deficient mice fed a NASH‐inducing diet had reduced concentrations of total plasma EVs and CXCL10 containing EVs compared to wild‐type mice. Conclusions: During hepatocyte lipotoxicity, activated MLK3 induces the release of CXCL10‐bearing vesicles from hepatocytes, which are chemotactic for macrophages. (Hepatology 2016;63:731–744)

IQ motif–containing GTPase-activating protein 1 (IQGAP1) is a cytoskeleton-interacting scaffold protein. CXCR4 is a chemokine receptor that binds stromal cell–derived factor-1 (SDF-1; also known as CXCL12). Both IQGAP1 and CXCR4 are overexpressed in cancer cell types, yet it was unclear whether these molecules functionally interact. Here, we show that depleting IQGAP1 in Jurkat T leukemic cells reduced CXCR4 expression, disrupted trafficking of endocytosed CXCR4 via EEA-1+ endosomes, and decreased efficiency of CXCR4 recycling. SDF-1–induced cell migration and activation of extracellular signal-regulated kinases 1 and 2 (ERK) MAPK were strongly inhibited, even when forced overexpression restored CXCR4 levels. Similar results were seen in KMBC and HEK293 cells. Exploring the mechanism, we found that SDF-1 treatment induced IQGAP1 binding to α-tubulin and localization to CXCR4-containing endosomes and that CXCR4-containing EEA-1+ endosomes were abnormally located distal from the microtubule (MT)-organizing center (MTOC) in IQGAP1-deficient cells. Thus, IQGAP1 critically mediates CXCR4 cell surface expression and signaling, evidently by regulating EEA-1+ endosome interactions with MTs during CXCR4 trafficking and recycling. IQGAP1 may similarly promote CXCR4 functions in other cancer cell types.

AbstractBackground & AimsC‐Jun N‐terminal kinase (JNK) activation is pivotal in the development of nonalcoholic steatohepatitis (NASH). Mixed lineage kinase 3 (MLK) 3 is one of the mitogen activated protein kinase kinase kinase (MAP3K) that mediates JNK activation in the liver. Despite this concept, the role of MLK3 in modulating liver injury during nutrient excess has not been explored. Our aim was to determine if MLK3 deficient mice were protected against high fat high carbohydrate (HFHC) diet‐induced NASH.MethodsWe employed eight‐week‐old Mlk3−/− male C57BL/6J mice, and wild type (WT) mice C57BL/6J as controls. Mice were fed a HFHC or a chow diet adlib for 16 weeks.ResultsHepatic JNK activating phosphorylation was readily absent in the Mlk3−/− mice fed the HFHC diet, but not in WT mice. This inhibition of JNK activation was hepatoprotective. Despite a comparable increase in weight gain, hepatic steatosis by histological examination and hepatic triglyceride quantification was reduced in HFHC diet‐fed Mlk3−/− mice compared with WT mice. In addition, compared with the WT mice, HFHC diet‐fed Mlk3−/− mice had significantly attenuated liver injury as manifested by reduced ALT levels, hepatocyte apoptosis, markers of hepatic inflammation and indices of hepatic fibrogenesis.ConclusionOur results suggest that loss of MLK3 in mice is protective against HFHC diet‐induced NASH, in a weight‐independent fashion, through attenuation of JNK activation. MLK3 is a potential therapeutic target for the treatment of human NASH.