L. Perea

Integrative miRNA and Gene Expression Profiling Analysis of Human Quiescent Hepatic Stellate Cells

Unveiling the regulatory pathways maintaining hepatic stellate cells (HSC) in a quiescent (q) phenotype is essential to develop new therapeutic strategies to treat fibrogenic diseases. To uncover the miRNA-mRNA regulatory interactions in qHSCs, HSCs were FACS-sorted from healthy livers and activated HSCs (aHSCs) were generated in vitro. MiRNA Taqman array analysis showed HSCs expressed a low number of miRNAs (n = 259), from which 47 were down-regulated and 212 up-regulated upon activation. Computational integration of miRNA and gene expression profiles revealed that 66% of qHSC-associated miRNAs correlated with more than 6 altered target mRNAs (17,28 ± 10,7 targets/miRNA) whereas aHSC-associated miRNAs had an average of 1,49 targeted genes. Interestingly, interaction networks generated by miRNA-targeted genes in qHSCs were associated with key HSC activation processes. Next, selected miRNAs were validated in healthy and cirrhotic human livers and miR-192 was chosen for functional analysis. Down-regulation of miR-192 in HSCs was found to be an early event during fibrosis progression in mouse models of liver injury. Moreover, mimic assays for miR-192 in HSCs revealed its role in HSC activation, proliferation and migration. Together, these results uncover the importance of miRNAs in the maintenance of the qHSC phenotype and form the basis for understanding the regulatory networks in HSCs.

Integrative microRNA profiling in alcoholic hepatitis reveals a role for microRNA-182 in liver injury and inflammation

Objective MicroRNAs (miRNAs) are well-known regulators of disease pathogenesis and have great potential as biomarkers and therapeutic targets. We aimed at profiling miRNAs in alcoholic hepatitis (AH) and identifying miRNAs potentially involved in liver injury. Design MiRNA profiling was performed in liver samples from patients with AH, alcohol liver disease, non-alcoholic steatohepatitis, HCV disease and normal liver tissue. Expression of miRNAs was assessed in liver and serum from patients with AH and animal models. Mimic and decoy miR-182 were used in vitro and in vivo to evaluate miR-182s biological functions. Results MiRNA expression profile in liver was highly altered in AH and distinctive from alcohol-induced cirrhotic livers. Moreover, we identified a set of 18 miRNAs predominantly expressed in AH as compared with other chronic liver conditions. Integrative miRNA-mRNA functional analysis revealed the association of AH-altered miRNAs with nuclear receptors, IGF-1 signalling and cholestasis. Interestingly, miR-182 was the most highly expressed miRNA in AH, which correlated with degree of ductular reaction, disease severity and short-term mortality. MiR-182 mimic induced an upregulation of inflammatory mediators in biliary cells. At experimental level, miR-182 was increased in biliary cells in mice fed with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet but not upregulated by alcohol intake or fibrosis. Inhibition of miR-182 in DDC-fed mice reduced liver damage, bile acid accumulation and inflammatory response. Conclusions AH is characterised by a deregulated miRNA profile, including miR-182, which is associated with disease severity and liver injury. These results highlight the potential of miRNAs as therapeutic targets and biomarkers in AH.

Pentraxin‐3 modulates lipopolysaccharide‐induced inflammatory response and attenuates liver injury

Acute‐on‐chronic liver injury is characterized by an important inflammatory response frequently associated with endotoxemia. In this context, acute‐phase proteins such as Pentraxin‐3 (PTX3) are released; however, little is known about their role in chronic liver disease. The aim of this study was to elucidate the role of PTX3 in liver injury. The role of PTX3 was evaluated in cultured human cells, liver tissue slices, and mice with acute‐on‐chronic liver injury. PTX3 expression was assessed in tissue and serum samples from 54 patients with alcoholic hepatitis. PTX3 expression was up‐regulated in animal models of liver injury and strongly induced by lipopolysaccharide (LPS). Liver cell fractionation showed that macrophages and activated hepatic stellate cells were the main cell types expressing PTX3 in liver injury. Ex vivo and in vivo studies showed that PTX3 treatment attenuated LPS‐induced liver injury, inflammation, and cell recruitment. Mechanistically, PTX3 mediated the hepatic stellate cell wound‐healing response. Moreover, PTX3 modulated LPS‐induced inflammation in human primary liver macrophages and peripheral monocytes by enhancing a TIR domain–containing adapter‐inducing interferon–dependent response and favoring a macrophage interleukin‐10‐like phenotype. Additionally, hepatic and plasma PTX3 levels were increased in patients with alcoholic hepatitis, a prototypic acute‐on‐chronic condition; and its expression correlated with disease severity scores, endotoxemia, infections, and short‐term mortality, thus suggesting that expression of PTX3 found in patients could be a counterregulatory response to injury. Conclusion: Experimental and human evidence suggests that, in addition to being a potential biomarker for alcoholic hepatitis, PTX3 participates in the wound‐healing response and attenuates LPS‐induced liver injury and inflammation; therefore, administration of PTX3 could be a promising therapeutic strategy in acute‐on‐chronic conditions, particularly those associated with endotoxemia. (Hepatology 2017;66:953–968).

Pentraxin‐3 Modulates LPS‐induced Inflammatory Response and Attenuates Liver Injury

Acute‐on‐chronic liver injury is characterized by an important inflammatory response frequently associated with endotoxemia. In this context, acute‐phase proteins such as Pentraxin‐3 (PTX3) are released; however, little is known about their role in chronic liver disease. The aim of this study was to elucidate the role of PTX3 in liver injury. The role of PTX3 was evaluated in cultured human cells, liver tissue slices, and mice with acute‐on‐chronic liver injury. PTX3 expression was assessed in tissue and serum samples from 54 patients with alcoholic hepatitis. PTX3 expression was up‐regulated in animal models of liver injury and strongly induced by lipopolysaccharide (LPS). Liver cell fractionation showed that macrophages and activated hepatic stellate cells were the main cell types expressing PTX3 in liver injury. Ex vivo and in vivo studies showed that PTX3 treatment attenuated LPS‐induced liver injury, inflammation, and cell recruitment. Mechanistically, PTX3 mediated the hepatic stellate cell wound‐healing response. Moreover, PTX3 modulated LPS‐induced inflammation in human primary liver macrophages and peripheral monocytes by enhancing a TIR domain–containing adapter‐inducing interferon–dependent response and favoring a macrophage interleukin‐10‐like phenotype. Additionally, hepatic and plasma PTX3 levels were increased in patients with alcoholic hepatitis, a prototypic acute‐on‐chronic condition; and its expression correlated with disease severity scores, endotoxemia, infections, and short‐term mortality, thus suggesting that expression of PTX3 found in patients could be a counterregulatory response to injury. Conclusion: Experimental and human evidence suggests that, in addition to being a potential biomarker for alcoholic hepatitis, PTX3 participates in the wound‐healing response and attenuates LPS‐induced liver injury and inflammation; therefore, administration of PTX3 could be a promising therapeutic strategy in acute‐on‐chronic conditions, particularly those associated with endotoxemia. (Hepatology 2017;66:953–968).

Expression of microRNA‐155 in inflammatory cells modulates liver injury

MicroRNA 155 (miR‐155) is involved in immune and inflammatory diseases and is associated with liver fibrosis and steatohepatitis. However, the mechanisms involved in miR‐155 regulation of liver injury are largely unknown. The role of miR‐155 in acute liver injury was assessed in wild‐type (WT), miR‐155−/−, and miR‐155−/− mice transplanted with WT bone marrow. Additionally, miR‐155 expression was evaluated in liver tissue and peripheral blood mononuclear cells of patients with autoimmune hepatitis. Concanavalin A, but not acetaminophen, treatment increased the expression of miR‐155 in liver tissue of WT mice. Concanavalin A induced increases in cell death, liver aminotransferases, and expression of proinflammatory cytokines (chemokine [C‐X‐C motif] ligands 1, 5, 9, 10, and 11; chemokine [C‐C motif] ligands 2 and 20; and intercellular cell adhesion molecule 1) in miR‐155−/− compared to WT mice. Importantly, these animals showed a significant decrease in cluster of differentiation 4–positive/chemokine (C‐X‐C motif) receptor 3–positive and forkhead box p3–positive cell recruitment but no changes in other inflammatory cell populations. Mechanistically, miR‐155‐deficient regulatory T cells showed increased SH2 domain–containing inositol 5‐phosphatase 1 expression, a known target of miR‐155. Inhibition of SH2 domain–containing inositol 5‐phosphatase 1 in miR‐155−/− mice restored forkhead box p3 recruitment and reduced liver cytokine expression. Transplantation of bone marrow from WT animals into miR‐155−/− mice partially reversed the effect of concanavalin A on miR‐155−/− mice as assessed by proinflammatory cytokines and cell death protein expression. Patients with autoimmune hepatitis showed a marked increase in miR‐155 expression in the liver but reduced expression of miR‐155 in peripheral blood mononuclear cells. Conclusion: miR‐155 expression is altered in both liver tissue and circulating inflammatory cells during liver injury, thus regulating inflammatory cell recruitment and liver damage; these results suggest that maintaining miR‐155 expression in inflammatory cells might be a potential strategy to modulate liver injury. (Hepatology 2018).

Kinase analysis in alcoholic hepatitis identifies p90RSK as a potential mediator of liver fibrogenesis

Objective Alcoholic hepatitis (AH) is often associated with advanced fibrosis, which negatively impacts survival. We aimed at identifying kinases deregulated in livers from patients with AH and advanced fibrosis in order to discover novel molecular targets. Design Extensive phosphoprotein analysis by reverse phase protein microarrays was performed in AH (n=12) and normal human livers (n=7). Ribosomal S6 kinase (p90RSK) hepatic expression was assessed by qPCR, Western blot and immunohistochemistry. Kaempferol was used as a selective pharmacological inhibitor of the p90RSK pathway to assess the regulation of experimentally-induced liver fibrosis and injury, using in vivo and in vitro approaches. Results Proteomic analysis identified p90RSK as one of the most deregulated kinases in AH. Hepatic p90RSK gene and protein expression was also upregulated in livers with chronic liver disease. Immunohistochemistry studies showed increased p90RSK staining in areas of active fibrogenesis in cirrhotic livers. Therapeutic administration of kaempferol to carbon tetrachloride-treated mice resulted in decreased hepatic collagen deposition, and expression of profibrogenic and proinflammatory genes, compared to vehicle administration. In addition, kaempferol reduced the extent of hepatocellular injury and degree of apoptosis. In primary hepatic stellate cells, kaempferol and small interfering RNA decreased activation of p90RSK, which in turn regulated key profibrogenic actions. In primary hepatocytes, kaempferol attenuated proapoptotic signalling. Conclusions p90RSK is upregulated in patients with chronic liver disease and mediates liver fibrogenesis in vivo and in vitro. These results suggest that the p90RSK pathway could be a new therapeutic approach for liver diseases characterised by advanced fibrosis.

Assessment of Liver Fibrotic Insults In Vitro.

In vitro systems are required to evaluate potential liver fibrogenic effects of drugs and compounds during drug development and toxicity screening, respectively. Upon liver injury or toxicity, hepatic stellate cells are activated, thereby acquiring a myofibroblastic phenotype and participating in extracellular matrix deposition and liver fibrosis. The most widely used in vitro models to investigate liver fibrogenesis are primary cultures of hepatic stellate cells, which can be isolated from healthy human livers. Currently, there are no effective methods to maintain hepatic stellate cells in vitro in a quiescent phenotype. Therefore, when cells are plated, they spontaneously become activated in few days. Most in vitro studies in this area have been performed with monocultures of hepatic stellate cells in order to assess the direct effects of a given factor on hepatic stellate cell activation or the induction of inflammatory and fibrogenic responses. In this chapter, focus is put on basic protocols to isolate hepatic stellate cells from human tissue and to maintain them in culture as well as on common in vitro assays to evaluate their response to profibrogenic factors.