RESUMEN
Macrophage-derived extracellular vesicles (EVs) play key roles in intercellular communication. Within the liver, they have been linked to several inflammatory diseases including nonalcoholic fatty liver disease (NAFLD). In this study, we found that inflammatory macrophages cause injury to hepatocytes, in part by a cell-cell crosstalk phenomenon involving the secretion of EVs containing pro-inflammatory cargo. Incorporation of these inflammatory signals into EV requires the cleavage of the trafficking adaptor protein RILP, which, as previously shown, results from inflammasome-mediated caspase-1 activation. RILP cleavage can be blocked by overexpressing a dominant negative, non-cleavable form of RILP (ncRILP). EV preparations from ncRILP-expressing cells are, by themselves, sufficient to suppress inflammatory effects in hepatocytes. These results suggest that both direct RILP manipulation and/or supplying ncRILP-modified EVs could be used as a novel therapy for the treatment of inflammatory liver diseases.
Asunto(s)
Vesículas Extracelulares , Enfermedad del Hígado Graso no Alcohólico , Humanos , Hepatocitos/metabolismo , Enfermedad del Hígado Graso no Alcohólico/etiología , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Macrófagos/metabolismo , Vesículas Extracelulares/metabolismoRESUMEN
BACKGROUND AND AIMS: Liver macrophages are heterogeneous and play an important role in alcohol-associated liver disease (ALD) but there is limited understanding of the functions of specific macrophage subsets in the disease. We used a Western diet alcohol (WDA) mouse model of ALD to examine the hepatic myeloid cell compartment by single cell RNAseq and targeted KC ablation to understand the diversity and function of liver macrophages in ALD. APPROACH AND RESULTS: In the WDA liver, KCs and infiltrating monocytes/macrophages each represented about 50% of the myeloid pool. Five major KC clusters all expressed genes associated with receptor-mediated endocytosis and lipid metabolism, but most were predicted to be noninflammatory and antifibrotic with 1 minor KC cluster having a proinflammatory and extracellular matrix degradation gene signature. Infiltrating monocyte/macrophage clusters, in contrast, were predicted to be proinflammatory and profibrotic. In vivo, diphtheria toxin-based selective KC ablation during alcohol exposure resulted in a liver failure phenotype with increases in PT/INR and bilirubin, loss of differentiated hepatocyte gene expression, and an increase in expression of hepatocyte progenitor markers such as EpCAM, CK7, and Igf2bp3. Gene set enrichment analysis of whole-liver RNAseq from the KC-ablated WDA mice showed a similar pattern as seen in human alcoholic hepatitis. CONCLUSIONS: In this ALD model, KCs are anti-inflammatory and are critical for the maintenance of hepatocyte differentiation. Infiltrating monocytes/macrophages are largely proinflammatory and contribute more to liver fibrosis. Future targeting of specific macrophage subsets may provide new approaches to the treatment of liver failure and fibrosis in ALD.
RESUMEN
This study aimed to better characterize the repertoire of serum hepatitis B virus (HBV) RNAs during chronic HBV infection in humans, which remains understudied. Using reverse transcription-PCR (RT-PCR), real-time quantitative PCR (RT-qPCR), RNA-sequencing, and immunoprecipitation, we found that (i) >50% of serum samples bore different amounts of HBV replication-derived RNAs (rd-RNAs); (ii) a few samples contained RNAs transcribed from integrated HBV DNA, including 5'-HBV-human-3' RNAs (integrant-derived RNAs [id-RNAs]) and 5'-human-HBV-3' transcripts, as a minority of serum HBV RNAs; (iii) spliced HBV RNAs were abundant in <50% of analyzed samples; (iv) most serum rd-RNAs were polyadenylated via conventional HBV polyadenylation signal; (v) pregenomic RNA (pgRNA) was the major component of the pool of serum RNAs; (vi) the area of HBV positions 1531 to 1739 had very high RNA read coverage and thus should be used as a target for detecting serum HBV RNAs; (vii) the vast majority of rd-RNAs and pgRNA were associated with HBV virions but not with unenveloped capsids, exosomes, classic microvesicles, or apoptotic vesicles and bodies; (viii) considerable rd-RNAs presence in the circulating immune complexes was found in a few samples; and (ix) serum relaxed circular DNA (rcDNA) and rd-RNAs should be quantified simultaneously to evaluate HBV replication status and efficacy of anti-HBV therapy with nucleos(t)ide analogs. In summary, sera contain various HBV RNA types of different origin, which are likely secreted via different mechanisms. In addition, since we previously showed that id-RNAs were abundant or predominant HBV RNAs in many of liver and hepatocellular carcinoma tissues as compared to rd-RNAs, there is likely a mechanism favoring the egress of replication-derived RNAs. IMPORTANCE The presence of integrant-derived RNAs (id-RNAs) and 5'-human-HBV-3' transcripts derived from integrated hepatitis B virus (HBV) DNA in sera was demonstrated for the first time. Thus, sera of individuals chronically infected with HBV contained both replication-derived and integrant-transcribed HBV RNAs. The majority of serum HBV RNAs were the transcripts produced by HBV genome replication, which were associated with HBV virions and not with other types of extracellular vesicles. These and other above-mentioned findings advanced our understanding of the HBV life cycle. In addition, the study suggested a promising target area on the HBV genome to increase sensitivity of the detection of serum HBV RNAs and supported the idea that simultaneous detection of replication-derived RNAs (rd-RNAs) and relaxed circular DNA (rcDNA) in serum provides more adequate evaluation of (i) the HBV genome replication status and (ii) the durability and efficiency of the therapy with anti-HBV nucleos(t)ide analogs, which could be useful for improvement of the diagnostics and treatment of HBV-infected individuals.
Asunto(s)
Hepatitis B Crónica , Neoplasias Hepáticas , Humanos , Virus de la Hepatitis B/genética , ARN , ADN Viral/genética , Replicación Viral/genética , ADN Circular/genética , ARN Viral/genéticaRESUMEN
BACKGROUND AND AIMS: Alcohol-associated liver disease is a major cause of alcohol-associated mortality. Recently, we identified hepatic demethylases lysine demethylase (KDM)5B and KDM5C as important epigenetic regulators of alcohol response in the liver. In this study, we aimed to investigate the role of KDM5 demethylases in alcohol-associated liver disease resolution. APPROACH AND RESULTS: We showed that alcohol-induced liver steatosis rapidly resolved after alcohol cessation. In contrast, fibrosis persisted in the liver for up to 8 weeks after the end of alcohol exposure. Defects in fibrosis resolution were in part due to alcohol-induced KDM5B and KDM5C-dependent epigenetic changes in hepatocytes. Using cell-type-specific knockout mice, we found that adeno-associated virus-mediated knockout of KDM5B and KDM5C demethylases in hepatocytes at the time of alcohol withdrawal promoted fibrosis resolution. Single-cell ATAC sequencing analysis showed that during alcohol-associated liver disease resolution epigenetic cell states largely reverted to control conditions. In addition, we found unique epigenetic cell states distinct from both control and alcohol states and identified associated transcriptional regulators, including liver X receptor (LXR) alpha (α). In vitro and in vivo analysis confirmed that knockout of KDM5B and KDM5C demethylases promoted LXRα activity, likely through regulation of oxysterol biosynthesis, and this activity was critical for the fibrosis resolution process. Reduced LXR activity by small molecule inhibitors prevented fibrosis resolution in KDM5-deficient mice. CONCLUSIONS: In summary, KDM5B and KDM5C demethylases prevent liver fibrosis resolution after alcohol cessation in part through suppression of LXR activity.
RESUMEN
BACKGROUND AND AIMS: Acute-on-chronic liver failure (ACLF) is an acute liver and multisystem failure in patients with previously stable cirrhosis. A common cause of ACLF is sepsis secondary to bacterial infection. Sepsis-associated ACLF involves a loss of differentiated liver function in the absence of direct liver injury, and its mechanism is unknown. We aimed to study the mechanism of sepsis-associated ACLF using a novel mouse model. APPROACH AND RESULTS: Sepsis-associated ACLF was induced by cecal ligation and puncture procedure (CLP) in mice treated with thioacetamide (TAA). The combination of TAA and CLP resulted in a significant decrease in liver synthetic function and high mortality. These changes were associated with reduced metabolic gene expression and increased CCAAT enhancer binding protein beta (C/EBPß) transcriptional activity. We found that C/EBPß binding to its target gene promoters was increased. In humans, C/EBPß chromatin binding was similarly increased in the ACLF group compared with control cirrhosis. Hepatocyte-specific Cebpb knockout mice had reduced mortality and increased gene expression of hepatocyte differentiation markers in TAA/CLP mice, suggesting that C/EBPß promotes liver failure in these mice. C/EBPß activation was associated with endothelial dysfunction, characterized by reduced Angiopoietin-1/Angiopoietin-2 ratio and increased endothelial production of HGF. Angiopoietin-1 supplementation or Hgf knockdown reduced hepatocyte C/EBPß accumulation, restored liver function, and reduced mortality, suggesting that endothelial dysfunction induced by sepsis drives ACLF through HGF-C/EBPß pathway. CONCLUSIONS: The transcription factor C/EBPß is activated in both mouse and human ACLF and is a potential therapeutic target to prevent liver failure in patients with sepsis and cirrhosis.
Asunto(s)
Insuficiencia Hepática Crónica Agudizada , Sepsis , Humanos , Ratones , Animales , Angiopoyetina 1 , Angiopoyetina 2 , Sepsis/complicaciones , Cirrosis Hepática/complicaciones , Factor de Crecimiento de HepatocitoRESUMEN
BACKGROUND AND AIMS: Resolution of pathways that converge to induce deleterious effects in hepatic diseases, such as in the later stages, have potential antifibrotic effects that may improve outcomes. We aimed to explore whether humans and rodents display similar fibrotic signaling networks. APPROACH AND RESULTS: We assiduously mapped kinase pathways using 340 substrate targets, upstream bioinformatic analysis of kinase pathways, and over 2000 random sampling iterations using the PamGene PamStation kinome microarray chip technology. Using this technology, we characterized a large number of kinases with altered activity in liver fibrosis of both species. Gene expression and immunostaining analyses validated many of these kinases as bona fide signaling events. Surprisingly, the insulin receptor emerged as a considerable protein tyrosine kinase that is hyperactive in fibrotic liver disease in humans and rodents. Discoidin domain receptor tyrosine kinase, activated by collagen that increases during fibrosis, was another hyperactive protein tyrosine kinase in humans and rodents with fibrosis. The serine/threonine kinases found to be the most active in fibrosis were dystrophy type 1 protein kinase and members of the protein kinase family of kinases. We compared the fibrotic events over four models: humans with cirrhosis and three murine models with differing levels of fibrosis, including two models of fatty liver disease with emerging fibrosis. The data demonstrate a high concordance between human and rodent hepatic kinome signaling that focalizes, as shown by our network analysis of detrimental pathways. CONCLUSIONS: Our findings establish a comprehensive kinase atlas for liver fibrosis, which identifies analogous signaling events conserved among humans and rodents.
Asunto(s)
Hepatopatías , Receptor de Insulina , Humanos , Ratones , Animales , Receptor de Insulina/metabolismo , Roedores , Cirrosis Hepática/patología , Hígado/patología , Hepatopatías/patología , Fibrosis , Proteínas Quinasas/metabolismo , Colágeno/metabolismo , Serina/metabolismo , Receptores con Dominio Discoidina/metabolismo , Treonina/metabolismoRESUMEN
BACKGROUND AND AIM: The American Association for the Study of Liver Diseases recommends a high index of suspicion for nonalcoholic steatohepatitis and advanced fibrosis in patients with type 2 diabetes (T2D) and an elevated fibrosis-4 index (FIB-4). We investigated the referral pattern of patients with T2D and FIB4 > 3.25 to the hepatology clinic and evaluated the clinical benefits to the patient. METHODS: We included patients aged 18-80 years with T2D and a FIB4 score >3.25 who had visited the internal medicine, family medicine, endocrinology clinic from 01/01/2014-5/31/2019. The first time point of high-risk FIB-4 was identified as the baseline for time-to-event analysis. The patients were classified based on whether they had visited the hepatology clinic (referred vs not referred). RESULTS: Of the 2174 patients, 290 (13.3%) were referred to the hepatology clinic, and 1884 (86.7%) were not referred. In multivariate analyses, the referred patients had a lower overall mortality risk (Hazard Ratio: 0.57; 95% CI: 0.38-87). Notably, the referred patients had the same rate of biochemical decompensation, as measured by progression to MELD ≥ 14, but a substantially higher rate of diagnosis in cirrhosis (27, 19-38) and cirrhosis complications, including ascites (2.9, 2.0-4.1), hepatic encephalopathy (99, 13-742), and liver cancer (14, 5-38). CONCLUSIONS: We found that patients with T2D and high-risk FIB4 are associated with better overall survival after referral to a hepatology clinic. We speculate that the survival difference is due to the increased recognition of cirrhosis and cirrhosis complications in the referred populations.
Asunto(s)
Diabetes Mellitus Tipo 2 , Gastroenterología , Enfermedad del Hígado Graso no Alcohólico , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/diagnóstico , Fibrosis , Humanos , Cirrosis Hepática/complicaciones , Cirrosis Hepática/diagnóstico , Enfermedad del Hígado Graso no Alcohólico/complicaciones , Enfermedad del Hígado Graso no Alcohólico/diagnóstico , Derivación y ConsultaRESUMEN
Protein arginine methyltransferase 1 (PRMT1) is a key regulator of hepatic immune responses. Recently, we reported that PRMT1 regulates the tumor immune response in hepatocellular carcinoma (HCC). Here we found that PRMT1 expression in human HCC correlates with that of programmed cell death 1 ligand 1 (PD-L1), PD-L2, and other checkpoint genes. PRMT1 deletion in mice reduced PD-L1 and PD-L2 expression in tumors and reduced the efficiency of PD-1 antibody treatment in a diethylnitrosamine-induced HCC mouse model, suggesting that PRMT1 regulates the hepatic immune checkpoint. Mice had reduced PD-L1 and PD-L2 expression when PRMT1 was specifically deleted in tumor cells or macrophages, but PRMT1 deletion in dendritic cells did not alter PD-L1 and PD-L2 expression. rs975484 is a common polymorphism in the human PRMT1 gene promoter, and we found that it alters PRMT1 expression in blood monocytes and tumor-associated macrophages in human HCC. PRMT1 expression was higher in individuals with a GG genotype than in individuals with a CC genotype, and heterozygous carriers had intermediate expression. Luciferase reporter assays indicated that this differential expression is due to an extra C/EBPß-binding site in the PRMT1 promoter of individuals carrying the minor G allele. The rs975484 genotype also correlated with PRMT1 target expression in HCC. Individuals with the GG genotype had significantly higher levels of the PRMT1 targets PD-L1, PD-L2, and VISTA than those with the CC genotype. We conclude that PRMT1 critically controls immune checkpoints in mice and humans and that the PRMT1 polymorphism rs975484 affects checkpoint gene expression in HCC.
Asunto(s)
Antígenos B7/inmunología , Antígeno B7-H1/inmunología , Carcinoma Hepatocelular/inmunología , Regulación Neoplásica de la Expresión Génica/inmunología , Neoplasias Hepáticas/inmunología , Proteínas de la Membrana/inmunología , Proteínas de Neoplasias/inmunología , Proteína 2 Ligando de Muerte Celular Programada 1/inmunología , Proteína-Arginina N-Metiltransferasas/inmunología , Proteínas Represoras/inmunología , Animales , Antígenos B7/genética , Antígeno B7-H1/genética , Carcinoma Hepatocelular/inducido químicamente , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patología , Células Dendríticas/inmunología , Células Dendríticas/patología , Dietilnitrosamina/toxicidad , Humanos , Neoplasias Hepáticas/inducido químicamente , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , Proteínas de la Membrana/genética , Ratones , Ratones Noqueados , Proteínas de Neoplasias/genética , Proteína 2 Ligando de Muerte Celular Programada 1/genética , Proteína-Arginina N-Metiltransferasas/genética , Proteínas Represoras/genética , Células THP-1RESUMEN
Appropriate control of hepatic gluconeogenesis is essential for the organismal survival upon prolonged fasting and maintaining systemic homeostasis under metabolic stress. Here, we show protein arginine methyltransferase 1 (PRMT1), a key enzyme that catalyzes the protein arginine methylation process, particularly the isoform encoded by Prmt1 variant 2 (PRMT1V2), is critical in regulating gluconeogenesis in the liver. Liver-specific deletion of Prmt1 reduced gluconeogenic capacity in cultured hepatocytes and in the liver. Prmt1v2 was expressed at a higher level compared to Prmt1v1 in hepatic tissue and cells. Gain-of-function of PRMT1V2 clearly activated the gluconeogenic program in hepatocytes via interactions with PGC1α, a key transcriptional coactivator regulating gluconeogenesis, enhancing its activity via arginine methylation, while no effects of PRMT1V1 were observed. Similar stimulatory effects of PRMT1V2 in controlling gluconeogenesis were observed in human HepG2 cells. PRMT1, specifically PRMT1V2, was stabilized in fasted liver and hepatocytes treated with glucagon, in a PGC1α-dependent manner. PRMT1, particularly Prmt1v2, was significantly induced in the liver of streptozocin-induced type 1 diabetes and high fat diet-induced type 2 diabetes mouse models and liver-specific Prmt1 deficiency drastically ameliorated diabetic hyperglycemia. These findings reveal that PRMT1 modulates gluconeogenesis and mediates glucose homeostasis under physiological and pathological conditions, suggesting that deeper understanding how PRMT1 contributes to the coordinated efforts in glycemic control may ultimately present novel therapeutic strategies that counteracts hyperglycemia in disease settings.
Asunto(s)
Gluconeogénesis , Hepatocitos/metabolismo , Hiperglucemia/genética , Proteína-Arginina N-Metiltransferasas/metabolismo , Animales , Células Cultivadas , Mutación con Ganancia de Función , Glucagón/metabolismo , Glucosa/metabolismo , Células Hep G2 , Humanos , Hiperglucemia/metabolismo , Ratones , Ratones Endogámicos C57BL , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteína-Arginina N-Metiltransferasas/genéticaRESUMEN
BACKGROUND: Mouse models of alcohol-associated liver disease vary greatly in their ease of implementation and the pathology they produce. Effects range from steatosis and mild inflammation with the Lieber-DeCarli liquid diet to severe inflammation, fibrosis, and pyroptosis seen with the Tsukamoto-French intragastric feeding model. Implementation of all of these models is limited by the labor-intensive nature of the protocols and the specialized skills necessary for successful intragastric feeding. We thus sought to develop a new model to reproduce features of alcohol-induced inflammation and fibrosis with minimal operational requirements. METHODS: Over a 16-week period, mice were fed ad libitum with a pelleted high-fat Western diet (WD; 40% calories from fat) and alcohol added to the drinking water. We found the optimal alcohol consumption to be that at which the alcohol concentration was 20% for 4 days and 10% for 3 days per week. Control mice received WD pellets with water alone. RESULTS: Alcohol consumption was 18 to 20 g/kg/day in males and 20 to 22 g/kg/day in females. Mice in the alcohol groups developed elevated serum transaminase levels after 12 weeks in males and 10 weeks in females. At 16 weeks, both males and females developed liver inflammation, steatosis, and pericellular fibrosis. Control mice on WD without alcohol had mild steatosis only. Alcohol-fed mice showed reduced HNF4α mRNA and protein expression. HNF4α is a master regulator of hepatocyte differentiation, down-regulation of which is a known driver of hepatocellular failure in alcoholic hepatitis. CONCLUSION: A simple-to-administer, 16-week WD alcohol model recapitulates the inflammatory, fibrotic, and gene expression aspects of human alcohol-associated steatohepatitis.
Asunto(s)
Dieta Occidental , Modelos Animales de Enfermedad , Etanol/administración & dosificación , Hígado Graso Alcohólico/patología , Hígado/patología , Animales , Femenino , Fibrosis , Factor Nuclear 4 del Hepatocito/metabolismo , Hígado/inmunología , Hígado/metabolismo , Masculino , Ratones Endogámicos C57BLRESUMEN
Autophagy is a conserved cellular process involving intracellular membrane trafficking and degradation. Pathogens, including hepatitis C virus (HCV), often exploit this process to promote their own survival. The aim of this study was to determine the mechanism by which HCV increases steady-state autophagosome numbers while simultaneously inhibiting flux through the autophagic pathway. Using the lysosomal inhibitor bafilomycin A1, we showed that HCV-induced alterations in autophagy result from a blockage of autophagosome degradation rather than an increase in autophagosome generation. In HCV-infected cells, lysosome function was normal, but a tandem RFP-GFP-LC3 failed to reach the lysosome even under conditions that activate autophagy. Autophagosomes and lysosomes isolated from HCV-infected cells were able to fuse with each other normally in vitro, suggesting that the cellular fusion defect resulted from trafficking rather than an inability of vesicles to fuse. Arl8b is an Arf-like GTPase that specifically localizes to lysosomes and plays a role in autophagic flux through its effect on lysosomal positioning. At basal levels, Arl8b was primarily found in a perinuclear localization and co-localized with LC3-positive autophagosomes. HCV infection increased the level of Arl8b 3-fold and redistributed Arl8b to a more diffuse, peripheral pattern that failed to co-localize with LC3. Knockdown of Arl8b in HCV-infected cells restored autophagosome-lysosome fusion and autophagic flux to levels seen in control cells. Thus, HCV suppresses autophagic flux and increases the steady-state levels of autophagosomes by increasing the expression of Arl8b, which repositions lysosomes and prevents their fusion with autophagosomes.
Asunto(s)
Factores de Ribosilacion-ADP/metabolismo , Autofagosomas/metabolismo , Hepatitis C/metabolismo , Lisosomas/metabolismo , Factores de Ribosilacion-ADP/genética , Línea Celular Tumoral , Humanos , Transporte de ProteínasRESUMEN
Alcohol is a well-established risk factor for hepatocellular carcinoma (HCC), but the mechanisms by which it promotes liver cancer are not well understood. Several studies have shown that cellular protein arginine methylation is inhibited by alcohol. Arginine methylation is controlled by the reciprocal activity of protein arginine methyltransferases, primarily protein arginine methyl transferase 1 (PRMT1), and a demethylase Jumonji C domain-containing protein 6 (JMJD6). The aim of this study was to explore the role of arginine methylation changes in alcohol pathogenesis. We found that PRMT1 activity is inhibited in livers of mice fed with alcohol compared to pair-fed mice. Using hepatocyte-specific PRMT1 knockout mice, we identified that loss of PRMT1 results in enhanced hepatocyte proliferation and a 33% increase in liver size. This increased hepatocyte proliferation was associated with reduced expression of hepatocyte nuclear factor 4 alpha (Hnf4α), an important regulator of liver tumorigenesis. We found that PRMT1 regulates Hnf4α expression directly through arginine methylation at the (Hnf4α) promoter. In the absence of PRMT1, JMJD6 can demethylate the Hnf4α promoter and suppress its expression. We were able to restore Hnf4α expression and abolish the increase in hepatocyte proliferation by knockdown of JMJD6 in PRMT1 knockout mice. Knockdown of JMJD6 in alcohol-fed mice similarly increased Hnf4α expression. We then examined whether loss of arginine methylation might play a role in alcohol-associated liver cancers. We examined 25 human HCC specimens and found a strong correlation (R = 0.8; P < 0.01) between arginine methylation levels and Hnf4α expression in these specimens, suggesting that the above mechanism is relevant in patients. CONCLUSION: Taken together, these data suggest that PRMT1 inhibition, such as induced by alcohol, may result in epigenetic changes leading to loss of Hnf4α. This effect may contribute to alcohol's ability to promote liver tumors. (Hepatology 2018;67:1109-1126).
Asunto(s)
Carcinoma Hepatocelular/metabolismo , Factor Nuclear 4 del Hepatocito/metabolismo , Hepatocitos/metabolismo , Neoplasias Hepáticas/metabolismo , Proteína-Arginina N-Metiltransferasas/metabolismo , Receptores de Superficie Celular/metabolismo , Animales , Arginina/metabolismo , Western Blotting , Carcinogénesis/metabolismo , Carcinoma Hepatocelular/patología , Técnicas de Cultivo de Célula , Proliferación Celular/genética , Inmunoprecipitación de Cromatina , Etanol/efectos adversos , Etanol/farmacología , Regulación Neoplásica de la Expresión Génica , Hepatocitos/patología , Humanos , Inmunohistoquímica , Hígado/patología , Neoplasias Hepáticas/patología , Metilación , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Hepatitis C virus (HCV) is an enveloped RNA virus that modifies intracellular trafficking processes. The mechanisms that HCV and other viruses use to modify these events are poorly understood. In this study, we observed that two different RNA viruses, HCV and Sendai, cause inhibition of ras-related protein Rab-7 (Rab7)-dependent endosome-lysosome fusion. In both cases, viral infection causes cleavage of the Rab7 adaptor protein RILP (Rab interacting lysosomal protein), which is responsible for linking Rab7 vesicles to dynein motor complexes. RILP cleavage results in the generation of a cleaved RILP fragment (cRILP) missing the N terminus of the molecule. Although RILP localizes in a perinuclear fashion, cRILP moves to the cell periphery. Both knockdown of RILP and expression of cRILP reproduced the HCV-induced trafficking defect, and restoring full-length RILP reversed the trafficking effects of virus. For the first 3 d after electroporation of HCV RNA, intracellular virus predominates over secreted virus, but the quantity of intracellular virus then rapidly declines as secreted virus dominates. The transition from the intracellular-predominant to the secretion-predominant phenotype corresponds to the time course of cRILP generation. Expressing cRILP directly prevents intracellular virus accumulation at early times without affecting net virus production. The ability of cRILP to promote virus secretion could be prevented by a kinesin inhibitor. HCV thus modifies cellular trafficking by cleaving RILP, which serves to redirect Rab7-containing vesicles to a kinesin-dependent trafficking mode promoting virion secretion. Cleavage of a Rab adaptor protein is thus a mechanism by which viruses modify trafficking patterns of infected cells.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Hepacivirus/metabolismo , Virión/metabolismo , Proteínas de Unión al GTP rab/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/virología , Línea Celular Tumoral , Endosomas/metabolismo , Endosomas/virología , Células HeLa , Hepacivirus/fisiología , Interacciones Huésped-Patógeno , Humanos , Cinesinas/metabolismo , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/virología , Lisosomas/metabolismo , Lisosomas/virología , Transporte de Proteínas , Virus Sendai/fisiología , Virión/fisiología , Proteínas de Unión al GTP rab/genética , Proteínas de Unión a GTP rab7RESUMEN
Macrophages are innate immune cells with diverse functions including clearing infectious agents, inducing inflammation and fibrosis, resolving fibrosis, and restoring tissue integrity. Liver macrophages consist of both resident Kupffer cells and infiltrating macrophages. They have heterogeneous highly plastic phenotypes, and they change their phenotypes rapidly in response to a diverse array of signals present in the injured or recovering liver. Cell death by apoptosis, necroptosis, or pyroptosis is a common response of liver macrophages to infectious and toxic insults. At the same time, the uptake of apoptotic and other dead cells, efferocytosis, is mediated by a series of dead cell receptors including MerTK, TIM4, and Stablin-1. These generate a critical signal that determines macrophage phenotype evolution. This review discusses the processes that lead to macrophage apoptosis and efferocytosis, and how these alter the course of liver diseases.
Asunto(s)
Muerte Celular , Macrófagos del Hígado/fisiología , Cirrosis Hepática/etiología , Animales , Apoptosis/fisiología , Enfermedad Hepática Inducida por Sustancias y Drogas/metabolismo , Enfermedad Hepática Inducida por Sustancias y Drogas/patología , Humanos , Inmunidad Celular , Hepatopatías Alcohólicas/metabolismo , Hepatopatías Alcohólicas/patología , Ratones , Fagocitosis/fisiología , Transducción de Señal/fisiologíaRESUMEN
Protein arginine methyltransferase 1 (PRMT1) is an essential enzyme controlling about 85% of the total cellular arginine methylation in proteins. We have shown previously that PRMT1 is an important regulator of innate immune responses and that it is required for M2 macrophage differentiation. c-Myc is a transcription factor that is critical in regulating cell proliferation and also regulates the M2 transcriptional program in macrophages. Here, we sought to determine whether c-Myc in myeloid cells is regulated by PRMT1-dependent arginine methylation. We found that PRMT1 activity was necessary for c-Myc binding to the acetyltransferase p300. PRMT1 inhibition decreased p300 recruitment to c-Myc target promoters and increased histone deacetylase 1 (HDAC1) recruitment, thereby decreasing transcription at these sites. Moreover, PRMT1 inhibition blocked c-Myc-mediated induction of several of its target genes, including peroxisome proliferator-activated receptor γ (PPARG) and mannose receptor C-type 1 (MRC1), suggesting that PRMT1 is necessary for c-Myc function in M2 macrophage differentiation. Of note, in primary human blood monocytes, p300-c-Myc binding was strongly correlated with PRMT1 expression, and in liver sections, PRMT1, c-Myc, and M2 macrophage levels were strongly correlated with each other. Both PRMT1 levels and M2 macrophage numbers were significantly lower in livers from individuals with a history of spontaneous bacterial peritonitis, known to have defective cellular immunity. In conclusion, our findings demonstrate that PRMT1 is an important regulator of c-Myc function in myeloid cells. PRMT1 loss in individuals with cirrhosis may contribute to their immune defects.
Asunto(s)
Células Mieloides/metabolismo , Regiones Promotoras Genéticas , Procesamiento Proteico-Postraduccional , Proteína-Arginina N-Metiltransferasas/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Transcripción Genética , Factores de Transcripción p300-CBP/metabolismo , Transporte Activo de Núcleo Celular/efectos de los fármacos , Animales , Arginina/metabolismo , Línea Celular Tumoral , Células Cultivadas , Inmunoprecipitación de Cromatina , Inhibidores Enzimáticos/farmacología , Histona Desacetilasa 1/metabolismo , Humanos , Hígado/inmunología , Hígado/metabolismo , Hígado/patología , Cirrosis Hepática/inmunología , Cirrosis Hepática/metabolismo , Cirrosis Hepática/patología , Metilación/efectos de los fármacos , Ratones Noqueados , Células Mieloides/efectos de los fármacos , Células Mieloides/inmunología , Células Mieloides/patología , Regiones Promotoras Genéticas/efectos de los fármacos , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Proteína-Arginina N-Metiltransferasas/antagonistas & inhibidores , Proteína-Arginina N-Metiltransferasas/genética , Transcripción Genética/efectos de los fármacosRESUMEN
Arginine methylation is a common posttranslational modification that has been shown to regulate both gene expression and extranuclear signaling events. We recently reported defects in protein arginine methyltransferase 1 (PRMT1) activity and arginine methylation in the livers of cirrhosis patients with a history of recurrent infections. To examine the role of PRMT1 in innate immune responses in vivo, we created a cell type-specific knock-out mouse model. We showed that myeloid-specific PRMT1 knock-out mice demonstrate higher proinflammatory cytokine production and a lower survival rate after cecal ligation and puncture. We found that this defect is because of defective peroxisome proliferator-activated receptor γ (PPARγ)-dependent M2 macrophage differentiation. PPARγ is one of the key transcription factors regulating macrophage polarization toward a more anti-inflammatory and pro-resolving phenotype. We found that PRMT1 knock-out macrophages failed to up-regulate PPARγ expression in response to IL4 treatment resulting in 4-fold lower PPARγ expression in knock-out cells than in wild-type cells. Detailed study of the mechanism revealed that PRMT1 regulates PPARγ gene expression through histone H4R3me2a methylation at the PPARγ promoter. Supplementing with PPARγ agonists rosiglitazone and GW1929 was sufficient to restore M2 differentiation in vivo and in vitro and abrogated the difference in survival between wild-type and PRMT1 knock-out mice. Taken together these data suggest that PRMT1-dependent regulation of macrophage PPARγ expression contributes to the infection susceptibility in PRMT1 knock-out mice.
Asunto(s)
Inmunidad Innata , Macrófagos/metabolismo , PPAR gamma/metabolismo , Proteína-Arginina N-Metiltransferasas/metabolismo , Proteínas Represoras/metabolismo , Animales , Anticuerpos/química , Arginina/química , Diferenciación Celular , Citocinas/metabolismo , Femenino , Histonas/metabolismo , Humanos , Interleucina-4/farmacología , Lipopolisacáridos , Cirrosis Hepática/metabolismo , Macrófagos/citología , Macrófagos Peritoneales/citología , Masculino , Metilación , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Monocitos/citología , Procesamiento Proteico-Postraduccional , Sepsis/metabolismoRESUMEN
Intracellular trafficking is a tightly regulated cellular process, mediated in part by Rab GTPases and their corresponding effector proteins. Viruses have evolved mechanisms to hijack these processes to promote their lifecycles. Here we describe a mechanism by which cleavage of the Rab7 adaptor protein, RILP (Rab interacting lysosomal protein) is induced by viral infection. We report that RILP is directly cleaved by caspase-1 and we have identified a novel caspase-1 recognition site at aspartic acid 75 within the RILP sequence. Alanine substitution at D75 blocks caspase-1-mediated RILP cleavage. Full-length RILP localizes in a tight vesicular structure near the perinuclear region while the cleaved form of RILP re-distributes throughout the cytoplasm. However, cleavage alone was insufficient to re-localize RILP to the cellular periphery and re-localization required specific phosphorylation events near the caspase-1 recognition site. The combination of cleavage and phosphorylation were both needed for release from the dynein component p150Glued and redistribution of CD63+ve intracellular vesicles.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Caspasa 1/genética , Complejo Dinactina/genética , Tetraspanina 30/genética , Proteínas de Unión al GTP rab/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Alanina/genética , Alanina/metabolismo , Sustitución de Aminoácidos , Ácido Aspártico/genética , Ácido Aspártico/metabolismo , Transporte Biológico , Caspasa 1/metabolismo , Vesículas Citoplasmáticas/química , Complejo Dinactina/metabolismo , Dineínas/genética , Dineínas/metabolismo , Regulación de la Expresión Génica , Células HeLa , Humanos , Mutación , Fosforilación , Proteolisis , Transducción de Señal , Tetraspanina 30/metabolismo , Proteínas de Unión al GTP rab/metabolismo , Proteínas de Unión a GTP rab7RESUMEN
Alcoholic liver disease encompasses the progressive stages of liver dysfunction that culminates in alcoholic cirrhosis (AC) and in severe cases alcoholic hepatitis (AH). Currently, prognostic scores have limited specificity and sensitivity. Plasma keratin-18 (K18) levels are elevated during liver disease and may be biomarkers of outcome. The objective of this study was to determine if total K18 (M65) or caspase-cleaved K18 (M30) levels were different between AC and AH patients. M65 and M30 levels were measured in the plasma of consented healthy controls and patients with AC and AH. Cell death was assessed by TUNEL staining and caspase activity. M65 and M30 values were significantly higher in AC patients compared to healthy controls and further increased in AH patients. The M65 values and the M30/M65 ratios of nonsurviving AH patients were significantly elevated above their surviving counterparts and healthy controls. Statistical analysis indicated that M30/M65 ratios outperformed current indices for accurately distinguishing the prognosis of AH patients. These scores occurred with minimal increase in plasma cell death markers such as ALT and AST. Serum caspase activity, TUNEL staining, and M30 immunohistochemistry in biopsies indicated that serum and tissue values may not correlate well with overall cell death. In conclusion, both M65 and M30 differentiate AH from AC patients, and M65 values and the M30/M65 ratio are capable of predicting early stage mortality; however, they may not accurately reflect pure hepatocyte cell death in these populations, as they do not strongly correlate with traditional cell death markers.
Asunto(s)
Biomarcadores/sangre , Hepatitis Alcohólica/sangre , Hepatitis Alcohólica/mortalidad , Queratina-18/sangre , Corticoesteroides/uso terapéutico , Adulto , Animales , Muerte Celular , Femenino , Hepatitis Alcohólica/tratamiento farmacológico , Humanos , Masculino , Ratones Endogámicos C57BL , Persona de Mediana Edad , Pentoxifilina/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Pronóstico , Curva ROC , Tasa de Supervivencia , Resultado del TratamientoRESUMEN
Arginine methylation is a common post-translational modification, but its role in regulating protein function is poorly understood. This study demonstrates that, TNF receptor-associated factor 6 (TRAF6), an E3 ubiquitin ligase involved in innate immune signaling, is regulated by reversible arginine methylation in a range of primary and cultured cells. Under basal conditions, TRAF6 is methylated by the methyltransferase PRMT1, and this inhibits its ubiquitin ligase activity, reducing activation of toll-like receptor signaling. In response to toll-like receptor ligands, TRAF6 is demethylated by the Jumonji domain protein JMJD6. Demethylation is required for maximal activation of NF-κB. Loss of JMJD6 leads to reduced response, and loss of PRMT1 leads to basal pathway activation with subsequent desensitization to ligands. In human primary cells, variations in the PRMT1/JMJD6 ratio significantly correlate with TRAF6 methylation, basal activation of NF-κB, and magnitude of response to LPS. Reversible arginine methylation of TRAF6 by the opposing effects of PRMT1 and JMJD6 is, therefore, a novel mechanism for regulation of innate immune pathways.
Asunto(s)
Arginina/metabolismo , Transducción de Señal , Factor 6 Asociado a Receptor de TNF/metabolismo , Receptores Toll-Like/metabolismo , Animales , Western Blotting , Línea Celular , Línea Celular Tumoral , Células Cultivadas , Humanos , Quinasas Asociadas a Receptores de Interleucina-1/genética , Quinasas Asociadas a Receptores de Interleucina-1/metabolismo , Histona Demetilasas con Dominio de Jumonji/genética , Histona Demetilasas con Dominio de Jumonji/metabolismo , Cinética , Ligandos , Masculino , Metilación , Ratones Endogámicos C57BL , FN-kappa B/genética , FN-kappa B/metabolismo , Proteína-Arginina N-Metiltransferasas/genética , Proteína-Arginina N-Metiltransferasas/metabolismo , Interferencia de ARN , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Factor 6 Asociado a Receptor de TNF/genética , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
UNLABELLED: Hepatitis C virus (HCV) infection produces chronic liver injury that is significantly exacerbated by alcohol consumption. While multiple mechanisms contribute to this synergy, a viral-induced loss of antioxidant responses has been shown to play an important role. This study examined the effects of HCV infection and alcohol on the regulation of the transcription factor FOXO3, an important regulator of Mn-superoxide dismutase (SOD2) expression, a tumor suppressor, and a component of the hepatic antioxidant response system. FOXO3 was activated by either HCV or alcohol alone but suppressed by the combination. To understand this paradoxical result, we applied a capillary isoelectric focusing (IEF) method to determine the pattern of FOXO3 posttranslational modifications (PTMs) induced by HCV and alcohol. We observed the presence of multiple different nuclear and cytosolic species of FOXO3 and used antiphosphoserine, acetyl-lysine, methylarginine, and ubiquitin antibodies to identify the PTM patterns present in each species. HCV caused multiple changes including phosphorylation of FOXO3 at S-574, a novel c-Jun N-terminal kinase (JNK) site, which promoted nuclear translocation and transcription. Ethanol suppressed arginine-methylation of FOXO3 promoting nuclear export and degradation of the JNK phosphorylated form. Human liver biopsy samples showed the presence of the HCV-specific form of FOXO3 in HCV-infected livers but not in normal liver or nonalcoholic steatohepatitis. CONCLUSION: The development of this novel IEF method for the simultaneous quantification of differently modified FOXO3 species allowed us to demonstrate how HCV and alcohol combine to modify a complex pattern of FOXO3 PTMs that contribute to pathogenesis. This approach will allow further dissection of the role of protein PTMs in viral liver disease.