sphingosine-1-phosphate and Liver-Cirrhosis

Liver dysfunction is always accompanied by lipid metabolism dysfunction. Apolipoprotein M (apoM), a member of the apolipoprotein family, is primarily expressed and secreted from the liver. apoM is the main chaperone of sphingosine-1-phosphate (S1P), a small signalling molecule associated with numerous physiologic and pathophysiologic processes. In addition to transport, apoM also influences the biologic effects of S1P. Most recently, numerous studies have investigated the potential role of the apoM-S1P axis in a variety of hepatic diseases. These include liver fibrosis, viral hepatitis B and C infection, hepatobiliary disease, non-alcoholic and alcoholic steatohepatitis, acute liver injury and hepatocellular carcinoma. In this review, the roles of apoM and S1P in the development of hepatic diseases are summarized, and novel insights into the diagnosis and treatment of hepatic diseases are discussed.

Topics: Apolipoproteins M; Humans; Liver Cirrhosis; Lysophospholipids; Sphingosine

The cell membrane, which is lipid-rich, is not only a simple mechanical barrier but also an important and complex component of the cell. It also communicates with the external environment. Sphingomyelin is an important class of phospholipids in the membrane that performs many functions. Interest in sphingomyelin-based liposomes, which are a critical component of cell membranes, have become the focus of intense study in recent years. Through additional research, the function of sphingomyelin and its derivatives in diseases can be gradually elucidated. Sphingomyelin consists of ceramide and its derivatives including ceramide-1-phosphate glucosylceramide and sphingosine-1-phosphate. The metabolism of glucosylceramide is regulated by glucosylceramide synthase (EC: 2.4.1.80) which is the key enzyme in the glycosylation of ceramide. The activity of glucosylceramide synthase directly affects the level of glucosylceramide in cells which in turn affects the function of cells and may eventually lead to diseases. Recently, the relationship between glucosylceramide and its metabolic enzymes, with diseases has become a relatively new area of study. The purpose of this paper is to address the relationship between glucosylceramide, glucosylceramide synthase, and their possible association with liver diseases at the theoretical level.

Topics: Apoptosis; Carcinoma, Hepatocellular; Cell Membrane; Ceramides; Glucosylceramides; Glucosyltransferases; Hepatocytes; Humans; Liver Cirrhosis; Liver Neoplasms; Lung Injury; Lysophospholipids; Sphingomyelins; Sphingosine

Hepatocytes, renal proximal tubule cells as well as the highly specialized endothelium of the blood brain barrier (BBB) express and secrete apolipoprotein M (apoM). ApoM is a typical lipocalin containing a hydrophobic binding pocket predominantly carrying Sphingosine-1-Phosphate (S1P). The small signaling molecule S1P is associated with several physiological as well as pathological pathways whereas the role of apoM is less explored. Hepatic apoM acts as a chaperone to transport S1P through the circulation and kidney derived apoM seems to play a role in S1P recovery to prevent urinal loss. Finally, polarized endothelial cells constituting the lining of the BBB express apoM and secrete the protein to the brain as well as to the blood compartment. The review will provide novel insights on apoM and S1P, and its role in hepatic fibrosis, neuroinflammation and BBB integrity.

Topics: Animals; Apolipoproteins M; Humans; Inflammation; Liver Cirrhosis; Lysophospholipids; Nervous System; Signal Transduction; Sphingosine

Hepatopulmonary syndrome (HPS) is characterised by a defect in arterial oxygenation induced by pulmonary vascular dilatation in patients with liver disease. Fingolimod, a sphingosine-1-phosphate (S1P) receptor modulator, suppresses vasodilation by reducing nitric oxide (NO) production. We investigated the role of S1P in patients with HPS and the role of fingolimod as a therapeutic option in an experimental model of HPS.. Patients with cirrhosis with HPS (n = 44) and without HPS (n = 89) and 25 healthy controls were studied. Plasma levels of S1P, NO, and markers of systemic inflammation were studied. In a murine model of common bile duct ligation (CBDL), variations in pulmonary vasculature, arterial oxygenation, liver fibrosis, and inflammation were estimated before and after administration of S1P and fingolimod.. Log of plasma S1P levels was significantly lower in patients with HPS than in those without HPS (3.1 ± 1.4 vs. 4.6 ± 0.2; p <0.001) and more so in severe intrapulmonary shunting than in mild and moderate intrapulmonary shunting (p <0.001). Plasma tumour necrosis factor-α (76.5 [30.3-91.6] vs. 52.9 [25.2-82.8]; p = 0.02) and NO (152.9 ± 41.2 vs. 79.2 ± 29.2; p = 0.001) levels were higher in patients with HPS than in those without HPS. An increase in Th17 (p <0.001) and T regulatory cells (p <0.001) was observed; the latter inversely correlated with plasma S1P levels. In the CBDL HPS model, fingolimod restored pulmonary vascular injury by increasing the arterial blood gas exchange and reducing systemic and pulmonary inflammation, resulting in improved survival (p = 0.02). Compared with vehicle treatment, fingolimod reduced portal pressure (p <0.05) and hepatic fibrosis and improved hepatocyte proliferation. It also induced apoptotic death in hepatic stellate cells and reduced collagen formation.. Plasma S1P levels are low in patients with HPS and even more so in severe cases. Fingolimod, by improving pulmonary vascular tone and oxygenation, improves survival in a murine CBDL HPS model.. A low level of plasma sphingosine-1-phosphate (S1P) is associated with severe pulmonary vascular shunting, and hence, it can serve as a marker of disease severity in patients with hepatopulmonary syndrome (HPS). Fingolimod, a functional agonist of S1P, reduces hepatic inflammation, improves vascular tone, and thus retards the progression of fibrosis in a preclinical animal model of HPS. Fingolimod is being proposed as a potential novel therapy for management of patients with HPS.

Topics: Animals; Fingolimod Hydrochloride; Hepatopulmonary Syndrome; Inflammation; Liver Cirrhosis; Mice; Niacinamide; Rats; Rats, Sprague-Dawley

Chronic liver congestion reflecting right-sided heart failure (RHF), Budd-Chiari syndrome, or Fontan-associated liver disease (FALD) is involved in liver fibrosis and HCC. However, molecular mechanisms of fibrosis and HCC in chronic liver congestion remain poorly understood.. Here, we first demonstrated that chronic liver congestion promoted HCC and metastatic liver tumor growth using murine model of chronic liver congestion by partial inferior vena cava ligation (pIVCL). As the initial step triggering HCC promotion and fibrosis, gut-derived lipopolysaccharide (LPS) appeared to induce LSECs capillarization in mice and in vitro. LSEC capillarization was also confirmed in patients with FALD. Mitogenic factor, sphingosine-1-phosphate (S1P), was increased in congestive liver and expression of sphingosine kinase 1, a major synthetase of S1P, was increased in capillarized LSECs after pIVCL. Inhibition of S1P receptor (S1PR) 1 (Ex26) and S1PR2 (JTE013) mitigated HCC development and liver fibrosis, respectively. Antimicrobial treatment lowered portal blood LPS concentration, LSEC capillarization, and liver S1P concentration accompanied by reduction of HCC development and fibrosis in the congestive liver.. In conclusion, chronic liver congestion promotes HCC development and liver fibrosis by S1P production from LPS-induced capillarized LSECs. Careful treatment of both RHF and liver cancer might be necessary for patients with RHF with primary or metastatic liver cancer.

Topics: Animals; Carcinoma, Hepatocellular; Disease Models, Animal; Fibrosis; Heart Failure; Humans; Lipopolysaccharides; Liver Cirrhosis; Liver Neoplasms; Lysophospholipids; Mice; Receptors, Lysosphingolipid; Sphingosine; Vascular Diseases

Sphingomyelin synthase 2 (SMS2) regulates sphingomyelin synthesis and contributes to obesity and hepatic steatosis. Here, we investigated the effect of SMS2 deficiency on liver fibrosis in mice fed with choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) or injected with carbon tetrachloride (CCl

Topics: Amino Acids; Animals; Chemical and Drug Induced Liver Injury; Choline; Diet, High-Fat; Fatty Liver; Liver; Liver Cirrhosis; Lysophospholipids; Mice, Knockout; Signal Transduction; Sphingosine; Transferases (Other Substituted Phosphate Groups)

To detect the leucine-rich repeats and immunoglobulin 1 (LRIG1) ameliorated liver fibrosis and hepatic stellate cell (HSC) activation via inhibiting sphingosine kinase 1 (SphK1)/Sphingosine-1-Phosphate (S1P) pathway. C57BL/6 male mice (eight weeks old) were intraperitoneal injection with 10% carbon tetrachloride (CCl4) as an in vivo model. The LX-2 cells were induced as amodel for in vitro study by TGF-β (10 ng/mL). The Hematoxylin-eosin (HE) staining, Masson staining, and Sirius red staining results showed that CCl4 caused serious fibrosis and injury in liver tissue, high expression of type I collagen α1 chain (Col1α1) and α-smooth muscle actin (α-SMA) in liver tissue, while the LRIG1 expression level was significantly decreased in LX-2 cell lines. The LRIG1 ameliorated CCl4-induced liver fibrosis, indicated by the fibronectin, α-SMA, LRIG1, SphK1, Col1α1, fibrin Connexin 1 (Fn1), tissue inhibitor of metalloproteinase-1 (TIMP1), sphingosine-1-phosphate (S1P), transforming growth factor-beta 1 (TGF-β1) expression level changes. Similar results were observed in TGF-β1 treated of LX-2 cells. However, the effects were attenuated by treatment with LRIG1. Moreover, SphK1 inhibitors abrogated the effect of LRIG1 on fibrosis. These results demonstrated that LRIG1 improved liver fibrosis in vitro and in vivo via suppressing the SphK1/S1P pathway, indicating its potential use in the treatment of liver fibrosis.

Topics: Animals; Biomarkers; Disease Models, Animal; Disease Susceptibility; Hepatic Stellate Cells; Immunohistochemistry; Liver Cirrhosis; Lysophospholipids; Male; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Nerve Tissue Proteins; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction; Sphingosine

The association of circulating sphingosine-1-phosphate (S1P), a bioactive lipid involved in various cellular processes, and related metabolites such as sphinganine-1-phosphate (SA1P) and sphingosine (SPH) with mortality in patients with end-stage liver disease is investigated in the presented study. S1P as a bioactive lipid mediator, is involved in several cellular processes, however, in end-stage liver disease its role is not understood.. The study cohort consisted of 95 patients with end-stage liver disease and available information on one-year outcome. The median MELD (Model for end-stage liver disease) score was 12.41 (Range 6.43-39.63). The quantification of sphingolipids in citrated plasma specimen was performed after methanolic protein precipitation followed by hydrophilic interaction liquid chromatography and tandem mass spectrometric detection.. S1P and SA1P displayed significant correlations with the MELD score. Patients with circulating S1P levels below the lowest tertile (110.68 ng/ml) showed the poorest one-year survival rate of only 57.1%, whereas one-year survival rate in patients with S1P plasma levels above 165.67 ng/ml was 93.8%. In a multivariate cox regression analysis including platelet counts, concentrations of hemoglobin and MELD score, S1P remained a significant predictor for three-month and one-year mortality.. Low plasma S1P concentrations are highly significantly associated with prognosis in end-stage liver disease. This association is independent of the stage of liver disease. Further studies should be performed to investigate S1P, its role in the pathophysiology of liver diseases and its potential for therapeutic interventions.

Topics: Adult; Aged; Chromatography, Liquid; Female; Humans; Liver Cirrhosis; Liver Failure; Lysophospholipids; Male; Middle Aged; Predictive Value of Tests; Prognosis; Sphingosine; Survival Rate; Tandem Mass Spectrometry; Young Adult

There is growing interest in the use of bone marrow cells to treat liver fibrosis, however, little is known about their antifibrotic efficacy or the identity of their effector cell(s). Sphingosine-1-phosphate (S1P) mediates egress of immune cells from the lymphoid organs into the lymphatic vessels; we investigated its role in the response of hematopoietic stem cells (HSCs) to liver fibrosis in mice.. Purified (c-kit+/sca1+/lin-) HSCs were infused repeatedly into mice undergoing fibrotic liver injury. Chronic liver injury was induced in BoyJ mice by injection of carbon tetrachloride (CCl. Infusions of HSCs into mice with liver injury reduced liver scarring based on picrosirius red staining (49.7% reduction in mice given HSCs vs control mice; P < .001), and hepatic hydroxyproline content (328 mg/g in mice given HSCs vs 428 mg/g in control mice; P < .01). HSC infusion also reduced hepatic expression of α-smooth muscle actin (0.19 ± 0.007-fold compared with controls; P < .0001) and collagen type I α 1 chain (0.29 ± 0.17-fold compared with controls; P < .0001). These antifibrotic effects were maintained with infusion of lymphoid progenitors that lack myeloid potential and were associated with increased numbers of recipient neutrophils and macrophages in liver. In studies of HSC cell lines, we found HSCs to recruit monocytes, and this process to require C-C motif chemokine receptor 2. In fibrotic liver tissue from mice and patients, hepatic S1P levels increased owing to increased hepatic sphingosine kinase-1 expression, which contributed to a reduced liver:lymph S1P gradient and limited HSC egress from the liver. Mice given the S1P antagonist (FTY720) with HSCs had increased hepatic retention of HSCs (1697 ± 247 cells in mice given FTY720 vs 982 ± 110 cells in controls; P < .05), and further reductions in fibrosis.. In studies of mice with chronic liver injury, we showed the antifibrotic effects of repeated infusions of purified HSCs. We found that HSCs promote recruitment of endogenous macrophages and neutrophils. Strategies to reduce SIP signaling and increase retention of HSCs in the liver could increase their antifibrotic activities and be developed for treatment of patients with liver fibrosis.

Topics: Actins; Aldehyde-Lyases; Animals; Cell Line; Cell Movement; Chemical and Drug Induced Liver Injury, Chronic; Collagen Type I; Collagen Type I, alpha 1 Chain; Female; Fingolimod Hydrochloride; Gene Expression; Hematopoietic Stem Cell Transplantation; Hematopoietic Stem Cells; Humans; Immunosuppressive Agents; Liver; Liver Cirrhosis; Lymph; Lysophospholipids; Macrophages; Male; Membrane Proteins; Mice; Monocytes; Neutrophils; Phosphoric Monoester Hydrolases; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Sphingosine 1-phosphate (S1P) participates in migration of bone marrow (BM)-derived mesenchymal stem cells (BMSCs) toward damaged liver via upregulation of S1P receptor 3 (S1PR3) during mouse liver fibrogenesis. But, the molecular mechanism is still unclear. HuR, as an RNA-binding protein, regulates tumor cell motility. Here, we examined the role of HuR in migration of human BMSCs (hBMSCs) in liver fibrosis. Results showed that HuR messenger RNA (mRNA) level was increased in human or mouse fibrotic livers, and correlated with S1PR3 mRNA expression. Using immunofluorescence, we found that HuR mainly localized in the nuclei of hepatocytes and non-parenchymal cells in normal livers. However, in fibrotic livers, we detected an increased HuR cytoplasmic localization in non-parenchymal cells. In chimeric mice of BM cell-labeled by EGFP, significant numbers of EGFP-positive cells (BM origin) were positive for HuR in fibrotic areas. Meanwhile, HuR-positive cells were also positive for α-SMA (myofibroblasts). In vitro, S1P induced hBMSCs migration via S1PR3 upregulation. HuR involved in S1P-induced hBMSCs migration and increased stabilization of S1PR3 mRNA via competing with miR-30e. RNA immunoprecipitation showed that HuR interacted with S1PR3 mRNA 3'UTR. Moreover, S1P resulted in phosphorylation and cytoplasmic translocation of HuR via S1PR3 and p38MAPK. Furthermore, we transplanted EGFP. HuR expression and cytoplasmic localization were increased in fibrotic livers. S1P induced migration of human bone marrow Mesenchymal Stem Cells via S1PR3 and HuR. HuR regulated S1PR3 mRNA expression by binding with S1PR3 mRNA 3'UTR. S1P induced HuR phosphorylation and cytoplasmic translocation via S1PR3. HuR regulated S1PR3 expression by competing with miR-30e.

Topics: Adult; Aged; Animals; Cell Movement; Disease Models, Animal; ELAV-Like Protein 1; Female; Gene Expression Regulation; Humans; Liver Cirrhosis; Lysophospholipids; Male; Mesenchymal Stem Cells; Mice; MicroRNAs; Middle Aged; Models, Biological; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Receptors, Lysosphingolipid; RNA Stability; RNA, Messenger; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors

Topics: Animals; Carbon Tetrachloride; Cell Line; Gene Expression Regulation; Hepatic Stellate Cells; Humans; Indoles; Lipid Metabolism; Liver Cirrhosis; Lysophospholipids; Male; Melatonin; Mice; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors

Bile duct obstruction is a potent stimulus for cholangiocyte proliferation, especially for large cholangiocytes. Our previous studies reported that conjugated bile acids (CBAs) activate the protein kinase B (AKT) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling pathways through sphingosine 1-phosphate receptor (S1PR) 2 in hepatocytes and cholangiocarcinoma cells. It also has been reported that taurocholate (TCA) promotes large cholangiocyte proliferation and protects cholangiocytes from bile duct ligation (BDL)-induced apoptosis. However, the role of S1PR2 in bile-acid-mediated cholangiocyte proliferation and cholestatic liver injury has not been elucidated. Here, we report that S1PR2 is the predominant S1PR expressed in cholangiocytes. Both TCA- and sphingosine-1-phosphate (S1P)-induced activation of ERK1/2 and AKT were inhibited by JTE-013, a specific antagonist of S1PR2, in cholangiocytes. In addition, TCA- and S1P-induced cell proliferation and migration were inhibited by JTE-013 and a specific short hairpin RNA of S1PR2, as well as chemical inhibitors of ERK1/2 and AKT in mouse cholangiocytes. In BDL mice, expression of S1PR2 was up-regulated in whole liver and cholangiocytes. S1PR2 deficiency significantly reduced BDL-induced cholangiocyte proliferation and cholestatic injury, as indicated by significant reductions in inflammation and liver fibrosis in S1PR2 knockout mice. Treatment of BDL mice with JTE-013 significantly reduced total bile acid levels in serum and cholestatic liver injury.. This study suggests that CBA-induced activation of S1PR2-mediated signaling pathways plays a critical role in obstructive cholestasis and may represent a novel therapeutic target for cholestatic liver diseases. (Hepatology 2017;65:2005-2018).

Topics: Analysis of Variance; Animals; Bile Acids and Salts; Bile Duct Neoplasms; Bile Ducts; Cell Proliferation; Cholangiocarcinoma; Cholangitis, Sclerosing; Cholestasis; Disease Models, Animal; Ligation; Liver; Liver Cirrhosis; Lysophospholipids; Male; Mice; Mice, Inbred CBA; Mice, Knockout; Mitogen-Activated Protein Kinase 1; Random Allocation; Receptors, Lysosphingolipid; Role; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors; Up-Regulation

We have recently shown that major alterations of serum sphingolipid metabolites in chronic liver disease associate significantly with the stage of liver fibrosis in corresponding patients. In the current study we assessed via mass spectrometry serum concentrations of sphingolipid metabolites in a series of 122 patients with hepatocellular carcinoma (HCC) compared to an age- and sex-matched series of 127 patients with cirrhosis. We observed a highly significant upregulation of long and very long chain ceramides (C16-C24) in the serum of patients with HCC as compared to patients with cirrhosis (P < 0.001). Accordingly, dihydro-ceramides, synthetic precursors of ceramides and notably sphingosine, sphingosine-1-phosphate (S1P) and sphinganine-1-phosphate (SA1P) were upregulated in patients with HCC (P < 0.001). Especially the diagnostic accuracy of C16-ceramide and S1P, assessed by receiver operating curve (ROC) analysis, showed a higher area under the curve (AUC) value as compared to alpha fetoprotein (AFP) (0.999 and 0.985 versus 0.823, P < 0.001 respectively). In conclusion, serum levels of sphingolipid metabolites show a significant upregulation in patients with HCC as compared to patients with cirrhosis. Particularly C16-ceramide and S1P may serve as novel diagnostic markers for the identification of HCC in patients with liver diseases. Our data justify further investigations on the role of sphingolipids in HCC.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Carcinoma, Hepatocellular; Ceramides; Female; Humans; Liver Cirrhosis; Liver Neoplasms; Lysophospholipids; Male; Middle Aged; Sphingosine; Up-Regulation

Ectopic lipid accumulation in hepatocytes has been identified as a risk factor for the progression of liver fibrosis and is strongly associated with obesity. In particular, the saturated fatty acid palmitate is involved in initiation of liver fibrosis via formation of secondary metabolites by hepatocytes that in turn activate hepatic stellate cells (HSCs) in a paracrine manner.. α-smooth muscle actin-expression (α-SMA) as a marker of liver fibrosis was investigated via western blot analysis and immunofluorescence microscopy in HSCs (LX-2). Sphingolipid metabolism and the generation of the bioactive secondary metabolite sphingosine 1-phosphate (S1P) in response to palmitate were analyzed by LC-MS/MS in hepatocytes (HepG2). To identify the molecular mechanism involved in the progression of liver fibrosis real-time PCR analysis and pharmacological modulation of S1P receptors were performed.. Palmitate oversupply increased intra- and extracellular S1P-concentrations in hepatocytes. Conditioned medium from HepG2 cells initiated fibrosis by enhancing α-SMA-expression in LX-2 in a S1P-dependent manner. In accordance, fibrotic response in the presence of S1P was also observed in HSCs. Pharmacological inhibition of S1P receptors demonstrated that S1P3 is the crucial receptor subtype involved in this process.. S1P is synthesized in hepatocytes in response to palmitate and released into the extracellular environment leading to an activation of HSCs via the S1P3 receptor.

Topics: Actins; Culture Media, Conditioned; Hep G2 Cells; Hepatic Stellate Cells; Hepatocytes; Humans; Liver Cirrhosis; Lysophospholipids; Non-alcoholic Fatty Liver Disease; Palmitates; Receptors, Lysosphingolipid; Sphingosine

Sphingosine 1-phosphate (S1P) is involved in multiple pathological processes, including fibrogenesis. S1P participates in mouse liver fibrogenesis via a paracrine manner. Herein, we investigated the involvement of S1P in human liver fibrosis. Human fibrotic samples were obtained from livers of patients undergoing liver transplantation. Expression of sphingosine kinase (SphK1), collagen (Col) α1(I), Col α1(III), α-smooth muscle actin, and p-Smad2/3 was characterized by immunofluorescence, real-time RT-PCR, high-content analysis, or Western blot analysis in the fibrotic liver, human bone marrow-derived mesenchymal stem cells, and human hepatogenic profibrotic cells. The effect of SphK1 was assessed using siSphK1 or SphK-specific inhibitor. SphK1, which was expressed in human fibrotic liver myofibroblasts, could be detected in human bone marrow-derived mesenchymal stem cells or human hepatogenic profibrotic cells activated by transforming growth factor β1 (TGF-β1). TGF-β1 evoked the activation of SphK1, increased intracellular S1P, and up-regulated expression of SphK1, Col α1(I), and Col α1(III) in a TGF-β receptor-dependent manner. TGF-β1 induced expression of Col α1(I) and Col α1(III) via SphK1, which was mediated by intracellular S1P, independent of S1P receptors. TGF-β1 evoked nuclear translocation of p-Smad2 and p-Smad3 in TGF-β receptor-dependent, but SphK1-independent, manner. In conclusion, intracellular S1P plays a crucial role in the TGF-β1-induced expression of Col α1(I) and Col α1(III), which is required for human fibrosis development. S1P exerts its effects in S1P receptor-independent manner.

Topics: Adult; Aged; Animals; Collagen Type I; Collagen Type I, alpha 1 Chain; Collagen Type III; Female; Gene Expression Regulation; Humans; Liver Cirrhosis; Lysophospholipids; Male; Mice; Middle Aged; Myofibroblasts; Phosphotransferases (Alcohol Group Acceptor); Smad2 Protein; Smad3 Protein; Sphingosine; Transforming Growth Factor beta1

Exosomes are cell-derived extracellular vesicles thought to promote intercellular communication by delivering specific content to target cells. The aim of this study was to determine whether endothelial cell (EC)-derived exosomes could regulate the phenotype of hepatic stellate cells (HSCs). Initial microarray studies showed that fibroblast growth factor 2 induced a 2.4-fold increase in mRNA levels of sphingosine kinase 1 (SK1). Exosomes derived from an SK1-overexpressing EC line increased HSC migration 3.2-fold. Migration was not conferred by the dominant negative SK1 exosome. Incubation of HSCs with exosomes was also associated with an 8.3-fold increase in phosphorylation of AKT and 2.5-fold increase in migration. Exosomes were found to express the matrix protein and integrin ligand fibronectin (FN) by Western blot analysis and transmission electron microscopy. Blockade of the FN-integrin interaction with a CD29 neutralizing antibody or the RGD peptide attenuated exosome-induced HSC AKT phosphorylation and migration. Inhibition of endocytosis with transfection of dynamin siRNA, the dominant negative dynamin GTPase construct Dyn2K44A, or the pharmacological inhibitor Dynasore significantly attenuated exosome-induced AKT phosphorylation. SK1 levels were increased in serum exosomes derived from mice with experimental liver fibrosis, and SK1 mRNA levels were up-regulated 2.5-fold in human liver cirrhosis patient samples. Finally, S1PR2 inhibition protected mice from CCl4-induced liver fibrosis. Therefore, EC-derived SK1-containing exosomes regulate HSC signaling and migration through FN-integrin-dependent exosome adherence and dynamin-dependent exosome internalization. These findings advance our understanding of EC/HSC cross-talk and identify exosomes as a potential target to attenuate pathobiology signals.

Topics: Animals; Cell Movement; Exosomes; Hepatic Stellate Cells; Humans; Integrins; Liver Cirrhosis; Lysophospholipids; Mice; Mice, Inbred C57BL; Receptors, Lysosphingolipid; Sphingosine; Sphingosine-1-Phosphate Receptors

Sphingosine kinase (SphK)/sphingosine 1-phosphate (S1P)/S1P receptor (S1PR) axis is involved in multiple biological processes, including liver fibrosis. Angiogenesis is an important pathophysiological process closely associated with liver fibrosis; however, the functional role of SphK/S1P/S1PR in this process remains incompletely defined.. Bile duct ligation or carbon tetrachloride was used to induce liver fibrosis in mice. Human fibrotic samples were obtained from livers of patients undergoing liver transplantation. S1P levels in the liver were examined by HPLC. Expression of angiogenic markers, including angiopoietin 1, CD31, vascular cell adhesion molecule-1, and von Willebrand factor, was characterized by immunofluorescence, real-time RT-PCR, and Western blot in the fibrotic liver and primary mouse hepatic stellate cells (HSCs). SphK inhibitor (SKI) or S1PR antagonists were administered intraperitoneally in mice.. S1P levels in the liver were closely correlated with mRNA expression of angiogenic markers. Ang1 is expressed in activated HSCs of the fibrotic liver and in primary HSCs. In HSCs, by using specific antagonists or siRNAs, we demonstrated S1P stimulation induced Ang1 expression via S1PR1 and S1PR3. In vivo, S1P reduction by SKI inhibited angiogenesis in fibrotic mice. Furthermore, S1PR1/3 antagonist significantly blocked upregulation of angiogenic markers in the injured liver, and attenuated the extent of liver fibrosis, while S1PR2 antagonist had no effect on angiogenesis, supporting the key role of S1PR1 and S1PR3 in angiogenesis underlying liver fibrosis process.. SphK1/S1P/S1PR1/3 axis plays a crucial role in the angiogenic process required for fibrosis development, which may represent an effective therapeutic strategy for liver fibrosis.

Topics: Adult; Aged; Angiopoietin-1; Animals; Female; Hepatic Stellate Cells; Humans; Liver; Liver Cirrhosis; Liver Cirrhosis, Experimental; Lysophospholipids; Male; Mice; Mice, Inbred ICR; Middle Aged; Neovascularization, Pathologic; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; Signal Transduction; Sphingosine

Directed migration of hepatic myofibroblasts (hMFs) contributes to the development of liver fibrosis. However, the signals regulating the motility of these cells are incompletely understood. We have recently shown that sphingosine 1-phosphate (S1P) and S1P receptors (S1PRs) are involved in mouse liver fibrogenesis. Here, we investigated the role of S1P/S1PRs signals in human liver fibrosis involving motility of human hMFs.. S1P level in the liver was examined by high-performance liquid chromatography. Expression of S1PRs was characterized, in biopsy specimens of human liver and cultured hMFs, by immunofluorescence and real-time RT-PCR or Western blot analysis. Cell migration was determined in Boyden chambers, by using the selective S1P receptor agonist or antagonist and silencing of S1PRs expression with small interfering RNA.. S1P level in the human fibrotic liver was increased through up-regulation of sphingosine kinase (SphK), irrespective of the etiology of fibrosis. S1P receptors type 1, 2, and 3 (S1P(1,2,3)) were expressed in human hMFs in vivo and in vitro. Interestingly, S1P(1,3) were strongly induced in human fibrotic samples, whereas expression of S1P(2) was massively decreased. S1P exerted a powerful migratory action on human hMFs. Furthermore, the effect of S1P was mimicked by SEW2871 (an S1P(1) agonist), and blocked by suramin (an S1P(3) antagonist) and by silencing S1P(1,3) expression. In contrast, JTE-013 (an S1P(2) antagonist) and silencing of S1P(2) expression enhanced S1P-induced migration.. SphK/S1P/S1PRs signaling axis plays an important role in human liver fibrosis and is involved in the directed migration of human hMFs into the damaged areas.

Topics: Base Sequence; Cell Movement; Cells, Cultured; Humans; Liver Cirrhosis; Lysophospholipids; Myofibroblasts; Oxadiazoles; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors; Suramin; Thiophenes

Bioactive lipid mediator S1P has been suggested to play pathophysiological roles in various fields of clinical science as a circulating paracrine mediator. We previously established a reliable method of measuring plasma S1P concentration, and reported that the one in healthy subjects has a gender difference and a correlation with red blood cell (RBC)-parameters, however, the reports of S1P measurements in the blood in patients with a specific disease have been scarce. Because our previous evidence suggests that S1P is involved in liver pathophysiology, we examined plasma S1P concentration in chronic hepatitis C patients.. S1P assay was performed using a high-performance liquid chromatography system.. Plasma S1P concentrations were reduced in chronic hepatitis C patients compared with in healthy subjects with the same hemoglobin concentration, irrespective of gender. Among the blood parameters, serum hyaluronic acid concentration, a surrogate marker for liver fibrosis, was most closely and inversely correlated with plasma S1P concentration. Furthermore, plasma S1P concentration decreased throughout the progression of carbon tetrachloride-induced liver fibrosis in rats.. Plasma S1P concentration was reduced in chronic hepatitis C patients, and liver fibrosis might be involved, at least in part, in the mechanism responsible for this reduction.

Topics: Aged; Aged, 80 and over; Animals; Blood Proteins; Carbon Tetrachloride; Female; Hemoglobins; Hepatitis C, Chronic; Humans; Hyaluronic Acid; Liver; Liver Cirrhosis; Lysophospholipids; Male; Middle Aged; Platelet Count; Rats; Rats, Sprague-Dawley; Serum Albumin; Sex Characteristics; Sphingosine

Sphingosine 1-phosphate (S1P), a bioactive lipid mediator, stimulates proliferation and contractility in hepatic stellate cells, the principal matrix-producing cells in the liver, and inhibits proliferation via S1P receptor 2 (S1P(2)) in hepatocytes in rats in vitro. A potential role of S1P and S1P(2) in liver regeneration and fibrosis was examined in S1P(2)-deficient mice. Nuclear 5-bromo-2'-deoxy-uridine labeling, proliferating cell nuclear antigen (PCNA) staining in hepatocytes, and the ratio of liver weight to body weight were enhanced at 48 h in S1P(2)-deficient mice after a single carbon tetrachloride (CCl(4)) injection. After dimethylnitrosamine (DMN) administration with a lethal dose, PCNA staining in hepatocytes was enhanced at 48 h and survival rate was higher in S1P(2)-deficient mice. Serum aminotransferase level was unaltered in those mice compared with wild-type mice in both CCl(4)- and DMN-induced liver injury, suggesting that S1P(2) inactivation accelerated regeneration not as a response to enhanced liver damage. After chronic CCl(4) administration, fibrosis was less apparent, with reduced expression of smooth-muscle alpha-actin-positive cells in the livers of S1P(2)-deficient mice, suggesting that S1P(2) inactivation ameliorated CCl(4)-induced fibrosis due to the decreased accumulation of hepatic stellate cells. Thus, S1P plays a significant role in regeneration and fibrosis after liver injury via S1P(2).

Topics: Animals; Carbon Tetrachloride; Dimethylnitrosamine; Female; Hepatocytes; Liver; Liver Cirrhosis; Liver Regeneration; Lysophospholipids; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Proliferating Cell Nuclear Antigen; Receptors, Lysosphingolipid; Sphingosine; Sphingosine-1-Phosphate Receptors

Myofibroblasts play a central role in the pathogenesis of liver fibrosis. Myofibroblasts of bone marrow (BM) origin have recently been identified in fibrotic liver. However, little is known about the mechanism that controls their mobilization in vivo. Here we confirmed that BM mesenchymal stem cells (BMSCs) can migrate to the damaged liver and differentiate into myofibroblasts. We also investigated the mechanism underlying the homing of BMSCs after liver injury.. ICR mice were lethally irradiated and received BM transplants from enhanced green fluorescent protein transgenic mice. Carbon tetrachloride or bile duct ligation was used to induce liver fibrosis. The fibrotic liver tissue was examined by immunofluorescent staining to identify BM-derived myofibroblasts.. BMSCs contributed significantly to myofibroblast population in fibrotic liver. Moreover, analysis in vivo and in vitro suggested that homing of BMSCs to the damaged liver was in response to sphingosine 1-phosphate (S1P) gradient between liver and BM. Furthermore, S1P receptor type 3 (S1P3) was required for migration of BMSCs triggered by S1P.. S1P mediates liver fibrogenesis through homing of BMSCs via S1P3 receptor, which may represent a novel therapeutic target in liver fibrosis through inhibiting S1P formation and/or receptor activation.

Topics: Animals; Base Sequence; Bone Marrow Cells; Bone Marrow Transplantation; Cell Differentiation; Cell Movement; DNA Primers; Green Fluorescent Proteins; In Vitro Techniques; Liver Cirrhosis; Lysophospholipids; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Mice; Mice, Inbred ICR; Mice, Transgenic; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; Recombinant Proteins; Sphingosine; Suramin; Transforming Growth Factor beta1

Bioactive sphingosine 1-phosphate (S1P) and S1P receptors (S1PRs) have been implicated in many critical cellular events, including inflammation, cancer, and angiogenesis. However, the role of S1P/S1PR signaling in the pathogenesis of liver fibrosis has not been well documented. In this study, we found that S1P levels and S1P(3) receptor expression in liver tissue were markedly up-regulated in a mouse model of cholestasis-induced liver fibrosis. In addition, the S1P(3) receptor was also expressed in green fluorescent protein transgenic bone marrow (BM)-derived cells found in the damaged liver of transplanted chimeric mice that underwent bile duct ligation. Silencing of S1P(3) expression significantly inhibited S1P-induced BM cell migration in vitro. Furthermore, a selective S1P(3) receptor antagonist, suramin, markedly reduced the number of BM-derived cells during cholestasis. Interestingly, suramin administration clearly ameliorated bile duct ligation-induced hepatic fibrosis, as demonstrated by attenuated deposition of collagen type I and III, reduced smooth muscle alpha-actin expression, and decreased total hydroxyproline content. In conclusion, our data suggest that S1P/S1P(3) signaling plays an important role in cholestasis-induced liver fibrosis through mediating the homing of BM cells. Modulation of S1PR activity may therefore represent a new antifibrotic strategy.

Topics: Animals; Bone Marrow Cells; Cell Movement; Cholestasis; Liver Cirrhosis; Lysophospholipids; Mice; Receptors, Lysosphingolipid; Signal Transduction; Sphingosine; Suramin

Platelet-derived growth factor (PDGF) has been shown to be essential in the activation of hepatic stellate cells (HSCs), contributing to the onset and development of hepatic fibrosis. Recently, sphingosine-1-phosphate (S1P) has been shown to be a mitogen and stimulator of chemotaxis also for HSCs. Since it has been demonstrated in several cell types that cross-talk between PDGF and S1P signalling pathways occurs, our aim was to investigate the potential antifibrotic effect of FTY720, whose phosphorylated form acts as a potent S1P receptor (S1PR) modulator, on HSCs. FTY720 inhibits cell proliferation and migration after PDGF stimulation on HSCs in a concentration range between 0.1 and 1 muM. By using compounds that block S1P signalling (PTX and VPC23019), we assessed that FTY720 also acts in an S1P receptor-independent way by decreasing the level of tyrosine phosphorylation of PDGF receptor, with subsequent inhibition of the PDGF signalling pathway. In addition, inhibition of sphingosine kinase2 (SphK2), which is responsible for FTY720 phosphorylation, by DMS/siRNA unveils a mechanism of action irrespective of its phosphorylation, in particular decreasing the level of S1P(1) on the plasma membrane. These findings led us to hypothesize a potential use of FTY720 as a potential antifibrotic drug for further clinical application.

Topics: Animals; Cell Movement; Cell Proliferation; Cells, Cultured; Fingolimod Hydrochloride; Immunologic Factors; Liver; Liver Cirrhosis; Lysophospholipids; Male; Platelet-Derived Growth Factor; Propylene Glycols; Protein Transport; Rats; Rats, Wistar; Receptor Cross-Talk; Signal Transduction; Sphingosine