The STAT3-IL-10-IL-6 Pathway Is a Novel Regulator of Macrophage Efferocytosis and Phenotypic Conversion in Sterile Liver Injury.

The disposal of apoptotic bodies by professional phagocytes is crucial to effective inflammation resolution. Our ability to improve the disposal of apoptotic bodies by professional phagocytes is impaired by a limited understanding of the molecular mechanisms that regulate the engulfment and digestion of the efferocytic cargo. Macrophages are professional phagocytes necessary for liver inflammation, fibrosis, and resolution, switching their phenotype from proinflammatory to restorative.

11Beta-hydroxysteroid dehydrogenase-1 deficiency or inhibition enhances hepatic myofibroblast activation in murine liver fibrosis.

Unlabelled: A hallmark of chronic liver injury is fibrosis, with accumulation of extracellular matrix orchestrated by activated hepatic stellate cells (HSCs). Glucocorticoids limit HSC activation in vitro, and tissue glucocorticoid levels are amplified by 11beta-hydroxysteroid dehydrogenase-1 (11βHSD1). Although 11βHSD1 inhibitors have been developed for type 2 diabetes mellitus and improve diet-induced fatty liver in various mouse models, effects on the progression and/or resolution of liver injury and consequent fibrosis have not been characterized.

In search of a small molecule agonist of the relaxin receptor RXFP1 for the treatment of liver fibrosis.

The peptide hormone human relaxin-2 (H2-RLX) has emerged as a potential therapy for cardiovascular and fibrotic diseases, but its short in vivo half-life is an obstacle to long-term administration. The discovery of ML290 demonstrated that it is possible to identify small molecule agonists of the cognate G-protein coupled receptor for H2-RLX (relaxin family peptide receptor-1 (RXFP1)). In our efforts to generate a new medicine for liver fibrosis, we sought to identify improved small molecule functional mimetics of H2-RLX with selective, full agonist or positive allosteric modulator activity against RXFP1.

Serelaxin as a potential treatment for renal dysfunction in cirrhosis: Preclinical evaluation and results of a randomized phase 2 trial.

Background: Chronic liver scarring from any cause leads to cirrhosis, portal hypertension, and a progressive decline in renal blood flow and renal function. Extreme renal vasoconstriction characterizes hepatorenal syndrome, a functional and potentially reversible form of acute kidney injury in patients with advanced cirrhosis, but current therapy with systemic vasoconstrictors is ineffective in a substantial proportion of patients and is limited by ischemic adverse events. Serelaxin (recombinant human relaxin-2) is a peptide molecule with anti-fibrotic and vasoprotective properties that binds to relaxin family peptide receptor-1 (RXFP1) and has been shown to increase renal perfusion in healthy human volunteers.

Relaxin modulates human and rat hepatic myofibroblast function and ameliorates portal hypertension in vivo.

Unlabelled: Active myofibroblast (MF) contraction contributes significantly to the increased intrahepatic vascular resistance that is the primary cause of portal hypertension (PHT) in cirrhosis. We sought proof of concept for direct therapeutic targeting of the dynamic component of PHT and markers of MF activation using short-term administration of the peptide hormone relaxin (RLN). We defined the portal hypotensive effect in rat models of sinusoidal PHT and the expression, activity, and function of the RLN-receptor signaling axis in human liver MFs.

Differential Ly-6C expression identifies the recruited macrophage phenotype, which orchestrates the regression of murine liver fibrosis.

Although macrophages are widely recognized to have a profibrotic role in inflammation, we have used a highly tractable CCl(4)-induced model of reversible hepatic fibrosis to identify and characterize the macrophage phenotype responsible for tissue remodeling: the hitherto elusive restorative macrophage. This CD11B(hi) F4/80(int) Ly-6C(lo) macrophage subset was most abundant in livers during maximal fibrosis resolution and represented the principle matrix metalloproteinase (MMP) -expressing subset. Depletion of this population in CD11B promoter-diphtheria toxin receptor (CD11B-DTR) transgenic mice caused a failure of scar remodeling.

Elastin accumulation is regulated at the level of degradation by macrophage metalloelastase (MMP-12) during experimental liver fibrosis.

Unlabelled: Elastin has been linked to maturity of liver fibrosis. To date, the regulation of elastin secretion and its degradation in liver fibrosis has not been characterized. The aim of this work was to define elastin accumulation and the role of the paradigm elastase macrophage metalloelastase (MMP-12) in its turnover during fibrosis.

Matrix stiffness modulates proliferation, chemotherapeutic response, and dormancy in hepatocellular carcinoma cells.

Unlabelled: There is increasing evidence that the physical environment is a critical mediator of tumor behavior. Hepatocellular carcinoma (HCC) develops within an altered biomechanical environment, and increasing matrix stiffness is a strong predictor of HCC development. The aim of this study was to establish whether changes in matrix stiffness, which are characteristic of inflammation and fibrosis, regulate HCC cell proliferation and chemotherapeutic response.

Metabolic pathways promoting intrahepatic fatty acid accumulation in methionine and choline deficiency: implications for the pathogenesis of steatohepatitis.

The pathological mechanisms that distinguish simple steatosis from steatohepatitis (or NASH, with consequent risk of cirrhosis and hepatocellular cancer) remain incompletely defined. Whereas both a methionine- and choline-deficient diet (MCDD) and a choline-deficient diet (CDD) lead to hepatic triglyceride accumulation, MCDD alone is associated with hepatic insulin resistance and inflammation (steatohepatitis). We used metabolic tracer techniques, including stable isotope ([¹³C₄]palmitate) dilution and mass isotopomer distribution analysis (MIDA) of [¹³C₂]acetate, to define differences in intrahepatic fatty acid metabolism that could explain the contrasting effect of MCDD and CDD on NASH in C57Bl6 mice.

Characterisation of a stereotypical cellular and extracellular adult liver progenitor cell niche in rodents and diseased human liver.

Background: Stem/progenitor cell niches in tissues regulate stem/progenitor cell differentiation and proliferation through local signalling.

Objective: To examine the composition and formation of stem progenitor cell niches.

Methods: The composition of the hepatic progenitor cell niche in independent models of liver injury and hepatic progenitor cell activation in rodents and humans was studied.

Active matrix metalloproteinase-2 promotes apoptosis of hepatic stellate cells via the cleavage of cellular N-cadherin.

Background And Aims: Hepatic stellate cells (HSC) are known to synthesise excess matrix that characterises liver fibrosis and cirrhosis. Activated HSC express the matrix-degrading matrix metalloproteinase enzymes (MMPs) and their tissue inhibitors (TIMPs). During spontaneous recovery from experimental liver fibrosis, the expression of TIMP-1 declines and hepatic collagenolytic activity increases.

p75 Neurotrophin receptor signaling regulates hepatic myofibroblast proliferation and apoptosis in recovery from rodent liver fibrosis.

Unlabelled: Hepatic myofibroblast apoptosis is critical to resolution of liver fibrosis. We show that human hepatic myofibroblasts co-express p75(NTR) (p75 neurotrophin receptor) and sortilin, thus facilitating differential responses to mature and pro nerve growth factor (proNGF). Although mature NGF is proapoptotic, proNGF protects human hepatic myofibroblasts from apoptosis.

HP1-beta is required for development of the cerebral neocortex and neuromuscular junctions.

HP1 proteins are thought to be modulators of chromatin organization in all mammals, yet their exact physiological function remains unknown. In a first attempt to elucidate the function of these proteins in vivo, we disrupted the murine Cbx1 gene, which encodes the HP1-beta isotype, and show that the Cbx1(-/-) -null mutation leads to perinatal lethality. The newborn mice succumbed to acute respiratory failure, whose likely cause is the defective development of neuromuscular junctions within the endplate of the diaphragm.

Plasticity of HP1 proteins in mammalian cells.

We have compared the distribution of endogenous heterochromatin protein 1 (HP1) proteins (alpha, beta and gamma) in different epithelial lines, pluripotent stem cells and embryonic fibroblasts. In parallel, we have interrogated assembly and dynamics of newly expressed HP1-GFP proteins in cells lacking both HP1alpha and HP1beta alleles, blocked at the G1-S boundary, or cultured in the presence of HDAC and HAT inhibitors. The results reveal a range of cell type and differentiation state-specific patterns that do not correlate with 'fast' or 'slow' subunit exchange in heterochromatin.

Heterochromatin, HP1 and methylation at lysine 9 of histone H3 in animals.

We show that methylated lysine 9 of histone H3 (Me9H3) is a marker of heterochromatin in divergent animal species. It localises to both constitutive and facultative heterochromatin and replicates late in S-phase of the cell cycle. Significantly, Me9H3 is enriched in the inactive mammalian X chromosome (Xi) in female cells, as well as in the XY body during meiosis in the male, and forms a G-band pattern along the arms of the autosomes.