Group 1 innate lymphoid cells (ILCs) comprise a heterogeneous family of cytotoxic natural killer (NK) cells and ILC1s. We identify a population of āliver-typeā ILC1s ... More
Group 1 innate lymphoid cells (ILCs) comprise a heterogeneous family of cytotoxic natural killer (NK) cells and ILC1s. We identify a population of āliver-typeā ILC1s with transcriptional, phenotypic, and functional features distinct from those of conventional and liver-resident NK cells as well as from other previously described human ILC1 subsets. LT-ILC1s are CD49a+CD94+CD200R1+, express the transcription factor T-BET, and do not express the activating receptor NKp80 or the transcription factor EOMES. Similar to NK cells, liver-type ILC1s produce IFN-Ī³, TNF-Ī±, and GM-CSF; however, liver-type ILC1s also produce IL-2 and lack perforin and granzyme-B. Liver-type ILC1s are expanded in cirrhotic liver tissues, and they can be produced from blood-derived ILC precursors in vitro in the presence of TGF-Ī²1 and liver sinusoidal endothelial cells. Cells with similar signature and function can also be found in tonsil and intestinal tissues. Collectively, our study identifies and classifies a population of human cross-tissue ILC1s. Less
Background
The activation of HIF-1Ī±/CXCR4 pathway in liver sinusoidal endothelial cells (LSECs) could downregulate CXCR7, leading to the capillarization of LSECs to prom... More
Background
The activation of HIF-1Ī±/CXCR4 pathway in liver sinusoidal endothelial cells (LSECs) could downregulate CXCR7, leading to the capillarization of LSECs to promote hepatic fibrosis. However, the mechanism between CXCR4 and CXCR7 is still undefined. The aim is to investigate the role of PDGF-BB in the dedifferentiation of LSECs and hepatic stellate cells (HSCs) activation.
Methods
The activation of HIF-1Ī±/CXCR4 pathway in two kinds of liver fibrosis models were observed. The effects of HIF-1Ī±, CXCR4, PDGF-BB on the dedifferentiation of LSECs were investigated by using the inhibitors of HIF-1Ī±, CXCR4 or PDGFR-Ī² separately or transfecting with a CXCR4 knockdown lentiviral vector. In addition, the relationship between LSECs and HSCs was demonstrated by co-culture of LSECs and HSCs using the transwell chamber.
Results
CXCR4 upregulation and CXCR7 downregulation were accompanied by LSECs capillarization and HSCs activation both in CCl4-induced and BDL-induced fibrotic liver. In vitro, downregulation of HIF-1Ī± significantly descreased CXCR4 and CD31 expression, and enhanced the expressions of CXCR7, CD44 and LYVE1. Downregulation of CXCR4 in LSECs significantly downregulated PDGF-BB, PDGFR-Ī² and CD31, and enhanced CXCR7, CD44 and LYVE1 expression, while the expression of HIF-1Ī± did not change significantly. STI571, a PDGF receptor inhibitor, could significantly downregulate PDGFR-Ī² and increase the expression of CXCR7 to inhibit the dedifferentiation of LSECs. In addition, alleviateion the dedifferentiation of LSECs could decrease the expression of PDGFR-Ī² of HSCs, then inhibiting the activation of HSCs.
Conclusions
This study revealed that HIF-1Ī±/CXCR4/PDGF-BB/CXCR7 axis promoted the dedifferentiation of LSECs, consequently triggering HSCs activation and liver fibrosis. Less
Objective To assess the feasibility of ultrasound molecular imaging in the early diagnosis of liver ischemia-reperfusion injury (IRI) using a nanoscale contrast agent tar... More
Objective To assess the feasibility of ultrasound molecular imaging in the early diagnosis of liver ischemia-reperfusion injury (IRI) using a nanoscale contrast agent targeting anti-intracellular adhesion molecule-1 (anti-ICAM-1). Methods The targeted nanobubbles containing anti-ICAM-1 antibody were prepared using the avidin-biotin binding method. Human hepatic sinusoidal endothelial cells (HHSECs) were cultured at the circumstances of hypoxia/reoxygenation (H/R) and low temperature. The rabbit liver IRI model (I/R group) was established using the Pringleās maneuver. The time-intensity curve of the liver contrast ultrasonographic images was plotted and the peak intensity, time to peak, and time of duration were calculated. Results The size of the targeted nanobubbles were 148.15 Ā± 39.75 nm and the concentration was 3.6ā7.4 Ć 109/ml, and bound well with the H/R HHSECs. Animal contrast enhanced ultrasound images showed that the peak intensity and time of duration of the targeted nanobubbles were significantly higher than that of common nanobubbles in the I/R group, and the peak intensity and time of duration of the targeted nanobubbles in the I/R group were also significantly higher than that in the SO group. Conclusion The targeted nanobubbles have small particle size, stable characteristic, and good targeting ability, which can assess hepatic ischemia-reperfusion injury specifically, noninvasively, and quantitatively at the molecular level. Less
MicroRNAs (miRNAs) control gene expression by reducing mRNA stability and translation. We aimed to identify alterations in human liver miRNA expression/function in nonalc... More
MicroRNAs (miRNAs) control gene expression by reducing mRNA stability and translation. We aimed to identify alterations in human liver miRNA expression/function in nonalcoholic fatty liver disease (NAFLD). Subjects with the highest (median liver fat 30%, n = 15) and lowest (0%, n = 15) liver fat content were selected from >100 obese patients for miRNA profiling of liver biopsies on microarrays carrying probes for 1438 human miRNAs (a cross-sectional study). Target mRNAs and pathways were predicted for the miRNAs most significantly upregulated in NAFLD, their cell-type-specific expression was investigated by quantitative PCR (qPCR), and the transcriptome of immortalized human hepatocytes (IHH) transfected with the miRNA with the highest number of predicted targets, miR-576-5p, was studied. The screen revealed 42 miRNAs up- and two downregulated in the NAFLD as compared to non-NAFLD liver. The miRNAs differing most significantly between the groups, miR-103a-2*, miR-106b, miR-576-5p, miRPlus-I137*, miR-892a, miR-1282, miR-3663-5p, and miR-3924, were all upregulated in NAFLD liver. Target pathways predicted for these miRNAs included ones involved in cancer, metabolic regulation, insulin signaling, and inflammation. Consistent transcriptome changes were observed in IHH transfected with miR-576-5p, and western analysis revealed a marked reduction of the RAC1 protein belonging to several miR-576-5p target pathways. To conclude, we identified 44 miRNAs differentially expressed in NAFLD versus non-NAFLD liver, 42 of these being novel in the context of NAFLD. The study demonstrates that by applying a novel study set-up and a broad-coverage array platform one can reveal a wealth of previously undiscovered miRNA dysregulation in metabolic disease. Keywords: Hepatocyte; immortalized human hepatocytes; liver biopsy; microRNA; microarray; nonalcoholic fatty liver disease. Less
Autophagy, a type II programmed cell death, is essential for cell survival under stress, e.g. lung injury, and bone marrow-derived mesenchymal stem cells (BM-MSCs) have g... More
Autophagy, a type II programmed cell death, is essential for cell survival under stress, e.g. lung injury, and bone marrow-derived mesenchymal stem cells (BM-MSCs) have great potential for cell therapy. However, the mechanisms underlying the BM-MSC activation of autophagy to provide a therapeutic effect in ischaemia/reperfusion-induced lung injury (IRI) remain unclear. Thus, we investigate the activation of autophagy in IRI following transplantation with BM-MSCs. Seventy mice were pre-treated with BM-MSCs before they underwent lung IRI surgery in vivo. Human pulmonary micro-vascular endothelial cells (HPMVECs) were pre-conditioned with BM-MSCs by oxygen-glucose deprivation/reoxygenation (OGD) in vitro. Expression markers for autophagy and the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signalling pathway were analysed. In IRI-treated mice, administration of BM-MSCs significantly attenuated lung injury and inflammation, and increased the level of autophagy. In OGD-treated HPMVECs, co-culture with BM-MSCs attenuated endothelial permeability by decreasing the level of cell death and enhanced autophagic activation. Moreover, administration of BM-MSCs decreased the level of PI3K class I and p-Akt while the expression of PI3K class III was increased. Finally, BM-MSCs-induced autophagic activity was prevented using the inhibitor LY294002. Administration of BM-MSCs attenuated lung injury by improving the autophagy level via the PI3K/Akt signalling pathway. These findings provide further understanding of the mechanisms related to BM-MSCs and will help to develop new cell-based therapeutic strategies in lung injury. Less
Liver sinusoidal endothelial cells (LSECs) represent a highly differentiated cell type that lines hepatic sinusoids. LSECs form a discontinuous endothelium due to fenestr... More
Liver sinusoidal endothelial cells (LSECs) represent a highly differentiated cell type that lines hepatic sinusoids. LSECs form a discontinuous endothelium due to fenestrations under physiological conditions, which are reduced upon chronic liver injury. Cultivation of rodent LSECs associates with a rapid onset of stress-induced senescence a few days post isolation, which limits genetic and biochemical studies ex vivo. Here we show the establishment of LSECs isolated from p19ARF-/- mice which undergo more than 50 cell doublings in the absence of senescence. Isolated p19ARF-/- LSECs display a cobblestone-like morphology and show the ability of tube formation. Analysis of DNA content revealed a stable diploid phenotype after long-term passaging without a gain of aneuploidy. Notably, p19ARF-/- LSECs express the endothelial markers CD31, vascular endothelial growth factor receptor (VEGFR)-2, VE-cadherin, von Willebrand factor, stabilin-2 and CD146 suggesting that these cells harbor and maintain an endothelial phenotype. In line, treatment with small molecule inhibitors against VEGFR-2 caused cell death, demonstrating the sustained ability of p19ARF-/- LSECs to respond to anti-angiogenic therapeutics. From these data we conclude that loss of p19ARF overcomes senescence of LSECs, allowing immortalization of cells without losing endothelial characteristics. Thus, p19ARF-/- LSECs provide a novel cellular model to study endothelial cell biology. Less
Growth and invasion of metastatic colorectal cancer (CRC) cells in the liver depend on microenvironment. Here, we showed that human hepatic sinusoidal endothelial cells (... More
Growth and invasion of metastatic colorectal cancer (CRC) cells in the liver depend on microenvironment. Here, we showed that human hepatic sinusoidal endothelial cells (HHSECs) induce chemotaxis and outgrowth of CRC cells. Macrophage migration inhibitory factor (MIF), released by HHSECs, stimulated chemotaxis of CRC cells. MIF secreted by HHSECs, but not by CRC cells themselves, promoted migration and epithelial-mesenchymal transition (EMT) and facilitated proliferation and apoptotic resistance of CRC cells. In orthotopic implantation models in nude mice, exogenous MIF stimulated growth of CRC cells and metastasis. Furthermore, MIF accelerated mobility of CRC cells by suppressing F-actin depolymerization and phosphorylating cofilin. Noteworthy, MIF levels were correlated with the size of hepatic metastases. We suggest that HHSECs and paracrine MIF promote initial migration and proliferation of CRC cells in the hepatic sinusoids to generate liver metastases. Keywords: chemotaxis; colorectal cancer; hepatic sinusoidal endothelial cell; macrophage migration inhibitory factor; metastasis. Less
BACKGROUND & AIMS: Liver sinusoidal endothelial cells (LSECs) make up a large proportion of the nonparenchymal cells in the liver. LSECs are involved in induction of immu... More
BACKGROUND & AIMS: Liver sinusoidal endothelial cells (LSECs) make up a large proportion of the nonparenchymal cells in the liver. LSECs are involved in induction of immune tolerance, but little is known about their functions during hepatitis C virus (HCV) infection. METHODS: Primary human LSECs (HLSECs) and immortalized liver endothelial cells (TMNK-1) were exposed to various forms of HCV, including fulllength transmitted/founder virus, sucrose-purified Japanese fulminant hepatitis-1 (JFH-1), a virus encoding a luciferase reporter, and the HCV-specific pathogen-associated molecular pattern molecules. Cells were analyzed by confocal immunofluorescence, immunohistochemical, and polymerase chain reaction assays. RESULTS: HLSECs internalized HCV, independent of cellācell contacts; HCV RNA was translated but not replicated. Through pattern recognition receptors (Toll-like receptor 7 and retinoic acidāinducible gene 1), HCV RNA induced consistent and broad transcription of multiple interferons (IFNs); supernatants from primary HLSECs transfected with HCV-specific pathogenassociated molecular pattern molecules increased induction of IFNs and IFN-stimulated genes in HLSECs. Recombinant type I and type III IFNs strongly up-regulated HLSEC transcription of IFN l3 (IFNL3) and viperin (RSAD2), which inhibit replication of HCV. Compared with CD8Ć¾ T cells, HLSECs suppressed HCV replication within Huh7.5.1 cells, also inducing IFN-stimulated genes in co-culture. Conditioned media from IFN-stimulated HLSECs induced expression of antiviral genes by uninfected primary human hepatocytes. Exosomes, derived from HLSECs after stimulation with either type I or type III IFNs, controlled HCV replication in a dose-dependent manner. CONCLUSIONS: Cultured HLSECs produce factors that mediate immunity against HCV. HLSECs induce self-amplifying IFN-mediated responses and release of exosomes with antiviral activity. Less
Chemotaxis signals between hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC) maintain hepatic vascular homeostasis and integrity and also regulate chang... More
Chemotaxis signals between hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC) maintain hepatic vascular homeostasis and integrity and also regulate changes in sinusoidal structure in response to liver injury. Our prior studies have demonstrated that the bidirectional chemotactic signaling molecules EphrinB2 and EphB4 are expressed in HSC. The aim of our present study was to explore whether and how the EphrinB2/EphB4 system in HSC could promote SEC recruitment, which is essential for sinusoidal structure and remodeling. Stimulation of human HSC (hHSC) with chimeric agonists (2 microg/ml) of either EphrinB2 or EphB4 (EphrinB2 Fc or EphB4 Fc, respectively) significantly increased VEGF mRNA levels in hHSC as assessed by quantitative PCR, with respective small interfering RNAs for EphrinB2 and EphB4 inhibiting this increase (P < 0.05, n = 3). EphrinB2 agonist-induced increase in VEGF mRNA levels in hHSC was associated with increased phosphorylation of Erk and was significantly blocked by U0126 (20 microM), an inhibitor of MEK, which is a kinase upstream from Erk (P < 0.05, n = 3). The EphB4 agonist also significantly increased human VEGF promoter activity (P < 0.05, n = 3) as assessed by promoter reporter luciferase assay in transfected LX2-HSC. This was associated with upregulation of the vasculoprotective transcription factor, Kruppel-like factor 2 (KLF2). In Boyden chamber assays, conditioned media from hHSC stimulated with agonists of EphrinB2 or EphB4 increased SEC chemotaxis in a VEGF-dependent manner, compared with control groups that included basal media with agonists of EphrinB2, EphB4, or HSC-conditioned media from HSC in absence of agonist stimulation (P < 0.05, n = 3). EphB4 expression was detected in situ within liver sinusoidal vessels of rats after carbon tetrachloride-induced liver injury. In summary, activation of the EphrinB2/EphB4 signaling pathway in HSC promotes chemotaxis of SEC through a pathway that involves Erk, KLF2, and VEGF. These studies identify EphrinB2 or EphB4 as a key intermediary that links HSC signal transduction pathways with angiogenesis and sinusoidal remodeling. Less
Aged or damaged RBCs are effectively removed from the blood circulation by Kupffer cells in the liver, but little is known regarding the mechanism of the clearance proces... More
Aged or damaged RBCs are effectively removed from the blood circulation by Kupffer cells in the liver, but little is known regarding the mechanism of the clearance process. Here we show that stabilin-1 and stabilin-2 in hepatic sinusoidal endothelial cells (HSECs) are critical in effectively clearing damaged RBCs in mouse liver. Damaged RBCs and phosphatidylserine (PS)-coated beads were effectively sequestered in the hepatic sinusoid regardless of the presence of Kupffer cells, suggesting a role for HSECs in PS-dependent sequestration of PS-exposed RBCs in the liver. HSECs mediate tethering of damaged RBCs in a PS-dependent manner via stabilin-1 and stabilin-2. In a sinusoid-mimicked coculture system consisting of macrophages layered over HSECs, there was significant enhancement of the phagocytic capacity of macrophages, and this was mediated by stabilin-1 and stabilin-2 in HSECs. Liver-specific knockdown of stabilin-1 and stabilin-2 inhibited the sequestration of damaged RBCs in the hepatic sinusoid and delayed the elimination of damaged cells in an in vivo animal model. Thus, the roles of stabilin-1 and stabilin-2 in hepatic sequestration of PS-exposed RBCs may represent a potential mechanism for the clearance of damaged RBCs by Kupffer cells and for the control of some pathologic conditions such as hemolytic anemia. Less
Chemotaxis signals between hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC) maintain hepatic vascular homeostasis and integrity and also regulate chang... More
Chemotaxis signals between hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC) maintain hepatic vascular homeostasis and integrity and also regulate changes in sinusoidal structure in response to liver injury. Our prior studies have demonstrated that the bidirectional chemotactic signaling molecules EphrinB2 and EphB4 are expressed in HSC. The aim of our present study was to explore whether and how the EphrinB2/EphB4 system in HSC could promote SEC recruitment, which is essential for sinusoidal structure and remodeling. Stimulation of human HSC (hHSC) with chimeric agonists (2 microg/ml) of either EphrinB2 or EphB4 (EphrinB2 Fc or EphB4 Fc, respectively) significantly increased VEGF mRNA levels in hHSC as assessed by quantitative PCR, with respective small interfering RNAs for EphrinB2 and EphB4 inhibiting this increase (P < 0.05, n = 3). EphrinB2 agonist-induced increase in VEGF mRNA levels in hHSC was associated with increased phosphorylation of Erk and was significantly blocked by U0126 (20 microM), an inhibitor of MEK, which is a kinase upstream from Erk (P < 0.05, n = 3). The EphB4 agonist also significantly increased human VEGF promoter activity (P < 0.05, n = 3) as assessed by promoter reporter luciferase assay in transfected LX2-HSC. This was associated with upregulation of the vasculoprotective transcription factor, Kruppel-like factor 2 (KLF2). In Boyden chamber assays, conditioned media from hHSC stimulated with agonists of EphrinB2 or EphB4 increased SEC chemotaxis in a VEGF-dependent manner, compared with control groups that included basal media with agonists of EphrinB2, EphB4, or HSC-conditioned media from HSC in absence of agonist stimulation (P < 0.05, n = 3). EphB4 expression was detected in situ within liver sinusoidal vessels of rats after carbon tetrachloride-induced liver injury. In summary, activation of the EphrinB2/EphB4 signaling pathway in HSC promotes chemotaxis of SEC through a pathway that involves Erk, KLF2, and VEGF. These studies identify EphrinB2 or EphB4 as a key intermediary that links HSC signal transduction pathways with angiogenesis and sinusoidal remodeling. Less
Interactions between hepatocytes and liver sinusoidal endothelial cells (LSECs) are essential for the development and maintenance of hepatic phenotypic functions. We repo... More
Interactions between hepatocytes and liver sinusoidal endothelial cells (LSECs) are essential for the development and maintenance of hepatic phenotypic functions. We report the assembly of three-dimensional liver sinusoidal mimics comprised of primary rat hepatocytes, LSECs, and an intermediate chitosan-hyaluronic acid polyelectrolyte multilayer (PEM). The height of the PEMs ranged from 30 to 55 nm and exhibited a shear modulus of approximately 100 kPa. Hepatocyte-PEM cellular constructs exhibited stable urea and albumin production over a 7-day period, and these values were either higher or similar to cells cultured in a collagen sandwich. This is of significance because the thickness of a collagen gel is approximately 1000-fold higher than the height of the chitosan-hyaluronic acid PEM. In the hepatocyte-PEM-LSEC liver-mimetic cellular constructs, LSEC phenotype was maintained, and these cultures exhibited stable urea and albumin production. CYP1A1/2 activity measured over a 7-day period was significantly higher in the hepatocyte-PEM-LSEC constructs than in collagen sandwich cultures. A 16-fold increase in CYP1A1/2 activity was observed for hepatocyte-PEM-10,000 LSEC samples, thereby suggesting that interactions between hepatocytes and LSECs are critical in enhancing the detoxification capability in hepatic cultures in vitro. Less
Increasing evidence suggests that hepatic fibrosis and pathological angiogenesis are interdependent processes that occur in parallel. Endothelial cell invasion is requisi... More
Increasing evidence suggests that hepatic fibrosis and pathological angiogenesis are interdependent processes that occur in parallel. Endothelial cell invasion is requisite for angiogenesis, and thus studies of the mechanisms governing liver endothelial cell (LEC) invasion during cirrhosis are of great importance. Emerging research implicates amoeboid-type motility and membrane blebbing as features that may facilitate invasion through matrix-rich microenvironments. Aquaporins (AQPs) are integral membrane water channels, recognized for their importance in epithelial secretion and absorption. However, recent studies also suggest links between water transport and cell motility or invasion. Therefore, the purpose of this study was to test the hypothesis that AQP-1 is involved in amoeboid motility and angiogenic invasion during cirrhosis. AQP-1 expression and localization was examined in normal and cirrhotic liver tissues derived from human and mouse. AQP-1 levels were modulated in LEC using retroviral overexpression or small interfering RNA (siRNA) knockdown and functional effects on invasion, membrane blebbing dynamics, and osmotic water permeability were assayed. Results demonstrate that AQP-1 is up-regulated in the small, angiogenic, neovasculature within the fibrotic septa of cirrhotic liver. AQP-1 overexpression promotes fibroblast growth factor (FGF)-induced dynamic membrane blebbing in LEC, which is sufficient to augment invasion through extracellular matrix. Additionally, AQP-1 localizes to plasma membrane blebs, where it increases osmotic water permeability and locally facilitates the rapid, trans-membrane flux of water. Conclusion: AQP-1 enhances osmotic water permeability and FGF-induced dynamic membrane blebbing in LEC and thereby drives invasion and pathological angiogenesis during cirrhosis. Less
Prokineticins are secreted peptides that activate two G protein-coupled receptors: PKR1 and PKR2. Prokineticins induce angiogenesis and fenestration, but the cognate rece... More
Prokineticins are secreted peptides that activate two G protein-coupled receptors: PKR1 and PKR2. Prokineticins induce angiogenesis and fenestration, but the cognate receptors involved in these functions are unknown. We hypothesized a role for prokineticin receptor signaling pathways and expression profiles in determining the selective effects of prokineticins on coronary endothelial cells (H5V). Activation of the PKR1/ MAPK/Akt signaling pathway stimulates proliferation, migration, and angiogenesis in H5V cells, in which PKR1 predominates over PKR2. PKR1 was colocalized with GĪ±11 and was internalized following the stimulation of these cells with prokineticin-2. Knock down of PKR1 or GĪ±11 expression in H5V cells effectively inhibited prokineticin-2-induced vessel formation and MAPK/Akt activation, indicating a role for PKR1/GĪ±11 in this process. However, in conditions in which PKR2 predominated over PKR1, these cells displayed a fenestrated endothelial cell phenotype. H5V cells overexpressing PKR2 displayed large numbers of multivesicular bodies and caveolar clusters and a disruption of the distribution of zonula occluden-1 tight junction protein. Prokineticin-2 induced the colocalization of PKR2 with GĪ±12, and activated GĪ±12, which bound to zonula occluden-1 to trigger the degradation of this protein in these cells. Prokineticin-2 induced the formation of vessel-like structures by human aortic endothelial cells expressing only PKR1, and disorganized the tight junctions in human hepatic sinusoidal endothelial cells expressing only PKR2, confirming the divergent roles of these receptors. Our findings show the functional characteristics of coronary endothelial cells depend on the expression of PKR1 and PKR2 levels and the divergent signaling pathways used by these receptors. Less
Background & aims: The liver is an organ with paradoxic immunologic properties and is known for its tolerant microenvironment, which holds important implications for hepa... More
Background & aims: The liver is an organ with paradoxic immunologic properties and is known for its tolerant microenvironment, which holds important implications for hepatic diseases. The molecular basis for this local immune suppression, however, is poorly understood. In this study, we aimed to determine the role of liver sinusoidal endothelial cell lectin (LSECtin), a recently identified member of the dendritic cell-specific ICAM-3 grabbing nonintegrin (DC-SIGN) family, in the regulation of hepatic T-cell immune response. Methods: The regulation of T-cell effector function by LSECtin was determined by co-stimulated T cells with anti-CD3/CD28 monoclonal antibody and LSECtin protein, or co-culture of T-cell receptor transgenic T cells with mouse LSECs in vitro. We generated LSECtin knockout mice and prepared recombinant LSECtin protein and complementary DNA plasmids to analyze the role of LSECtin in hepatic T-cell immune regulation in vivo. Results: We showed that LSECtin specifically recognized activated T cells and negatively regulated their immune responses. In mice with T-cell-mediated acute liver injury, the lack of LSECtin accelerated the disease owing to an increased T-cell immune response, whereas the exogenous administration of recombinant LSECtin protein or plasmid ameliorated the disease via down-regulation of T-cell immunity. Conclusions: Our results reveal that LSECtin is a novel regulator of T cells and expose a crucial mechanism for hepatic T-cell immune suppression, perhaps opening up a new approach for treatment of inflammatory diseases in the liver. Less
Although lymphocyte recirculation to the endothelium plays a critical role in the movement of immune cells from the blood into tissues and sites of inflammation, the mech... More
Although lymphocyte recirculation to the endothelium plays a critical role in the movement of immune cells from the blood into tissues and sites of inflammation, the mechanisms involved in lymphocyte trafficking via the hepatic circulation have yet to be elucidated fully. In this study, we investigated the role of stabilin-2, which is expressed specifically in the sinusoidal endothelium, in the adhesion of lymphocytes to the hepatic endothelium. Stabilin-2-expressing cells mediate the adhesion of PBLs. This interaction was attributed specifically to the interaction of stabilin-2 with alphaMbeta2 integrin. Using mutant stabilin-2 molecules with deletions in the extracellular domain, we mapped the binding site for alphaMbeta2 integrin to the fasciclin 1 (FAS1) domains of stabilin-2. The specificity of the interaction between alphaMbeta2 integrin and the FAS1 domain was confirmed further by binding assays using neutralizing antibodies. More physiologically, we showed that the down-regulation of stabilin-2 results in the defective binding of lymphocytes to hepatic sinusoidal endothelial cells under conditions of static and physiological flow. Together, these data show that stabilin-2 can reconstitute the lymphocyte-endothelial adhesion cascade under physiological shear stress. We propose a critical role for stabilin-2 in lymphocyte adhesion to specialized endothelia, such as that of the hepatic sinusoid. Less
NO antagonizes hepatic stellate cell (HSC) contraction, although activated HSC in cirrhosis demonstrate impaired responses to NO. Decreased NO responses in activated HSC ... More
NO antagonizes hepatic stellate cell (HSC) contraction, although activated HSC in cirrhosis demonstrate impaired responses to NO. Decreased NO responses in activated HSC and mechanisms by which NO affects activated HSC remain incompletely understood. In normal rat HSC, the NO donor diethylamine NONOate (DEAN) significantly increased cGMP production and reduced serum-induced contraction by 25%. The guanylate cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) abolished 50% of DEAN effects, whereas the cGMP analog 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) reiterated half the observed DEAN response, suggesting both cGMP-dependent protein kinase G (PKG)-dependent and -independent mechanisms of NO-mediated antagonism of normal HSC contraction. However, NO donors did not increase cGMP production from in vivo activated HSC from bile duct-ligated rats and showed alterations in intracellular Ca(2+) accumulation suggesting defective cGMP-dependent effector pathways. The LX-2 cell line also demonstrated lack of cGMP generation in response to NO and a lack of effect of ODQ and 8-BrcGMP in modulating the NO response. However, cGMP-independent effects in response to NO were maintained in LX-2 and were associated with S-nitrosylation of proteins, an effect reiterated in primary HSC. Adenovirus-based overexpression of PKG significantly attenuated contraction of LX-2 by 25% in response to 8-BrcGMP. In summary, these studies demonstrate that NO affects HSC through cGMP-dependent and -independent pathways. The HSC activation process is associated with maintenance of cGMP-independent actions of NO but defects in cGMP-PKG-dependent NO signaling that are improved by PKG gene delivery in LX-2 cells. Activating targets downstream from NO-cGMP in activated HSC may represent a novel therapeutic target for portal hypertension. Less
Here, we describe a simple protocol for the design and construction of a laser-guided direct writing (LGDW) system able to micropattern the self-assembly of liver sinusoi... More
Here, we describe a simple protocol for the design and construction of a laser-guided direct writing (LGDW) system able to micropattern the self-assembly of liver sinusoid-like structures with micrometer resolution in vitro. To the best of our knowledge, LGDW is the only technique able to pattern cells "on the fly" with micrometer precision on arbitrary matrices, including soft gels such as Matrigel. By micropatterning endothelial cells on Matrigel, one can control the self-assembly of vascular structures and associated liver tissue. LGDW is therefore uniquely suited for studying the role of tissue architecture and mechanical properties at the single-cell resolution, and for studying the effects of heterotypic cell-cell interactions underlying processes such as liver morphogenesis, differentiation and angiogenesis. The total time required to carry out this protocol is typically 7 h. Less
Low-density lipoprotein (LDL) is an important carrier of plasma cholesterol and triglycerides whose concentration is regulated by the liver parenchymal cells. Abnormal LD... More
Low-density lipoprotein (LDL) is an important carrier of plasma cholesterol and triglycerides whose concentration is regulated by the liver parenchymal cells. Abnormal LDL regulation is thought to cause atherosclerosis, while viral binding to LDL has been suggested to facilitate hepatitis C infection. Primary hepatocytes quickly lose the ability to clear LDL during in vitro culture. Here we show that the coculture of hepatocytes with liver sinusoidal endothelial cells (LSEC) significantly increases the ability of hepatocytes to uptake LDL in vitro. LDL uptake does not increase when hepatocytes are cocultured with other cell types such as fibroblasts or umbilical vein endothelial cells. We find that LSECs induce the hepatic expression of the LDL receptor and the epidermal growth factor receptor. In addition, while hepatocytes in single culture did not take up hepatitis C virus (HCV)-like particles, the hepatocytes cocultured with LSECs showed a high level of HCV-like particle uptake. We suggest that coculture with LSECs induces the emergence of a sinusoidal surface in primary hepatocytes conducive to the uptake of HCV-like particles. In conclusion, our findings describe a novel model of polarized hepatocytes in vitro that can be used for the study of LDL metabolism and hepatitis C infection. Less
