Adenovirus-mediated hepatic syndecan-1 overexpression induces hepatocyte proliferation and hyperlipidaemia in mice

Increased syndecan-1 and glypican-3 predict poor perinatal outcome and treatment resistance in intrahepatic cholestasis

BACKGROUND

Intrahepatic cholestasis of pregnancy (ICP) increases the risk of adverse pregnancy outcomes. This study aimed to explore the association between serum syndecan-1 and glypican-3 levels and the adverse perinatal outcome as well as the responses to the treatment of ursodeoxycholic acid (UDCA).

METHODS

This prospective, case control study included 88 pregnant women (44 women with ICP and 44 healthy controls). The primary end points were the perinatal outcome and the response to UDCA therapy. A logistic regression model was used to identify the independent risk factors of adverse pregnancy outcomes and reduced response to UDCA therapy.

RESULTS

Women with ICP had significantly higher serum syndecan-1 (1.27 ± 0.36 ng/mL vs. 0.98 ± 0.50 ng/mL; P = 0.003), glypican-3 (1.78 ± 0.13 ng/mL vs.1.69 ± 0.16 ng/mL; P = 0.004), AST (128.59 ± 1.44 vs. 13.29 ± 1.32 U/L; P < 0.001), and ALT (129.84 ± 1.53 vs. 8.00 ± 3.67 U/L; P < 0.001) levels compared with the controls. The increased levels of syndecan-1 (OR = 4.715, 95% CI: 1.554-14.310; P = 0.006), glypican-3 (OR = 8.465, 95% CI: 3.372-21.248; P = 0.007), ALT (OR = 1.382, 95% CI: 1.131-1.690; P = 0.002), and postprandial bile acid (PBA) (OR = 3.392, 95% CI: 1.003-12.869; P = 0.026) were correlated to ICP. The adverse neonatal outcome was related to increased glypican-3 (OR = 4.275, 95% CI: 2.726-5.635; P = 0.039), and PBA (OR = 3.026, 95% CI: 1.069-13.569; P = 0.037). Increases of syndecan-1 (OR = 7.464, 95% CI: 2.130-26.153, P = 0.017) and glypican-3 (OR = 6.194, 95% CI: 2.951-13.002; P = 0.025) were the risk factors of decreased response to UDCA treatment.

CONCLUSION

Syndecan-1 and glypican-3 might be powerful determinants in predicting adverse perinatal outcome in patients with ICP, and they can be used to predict the response to the UDCA treatment.

Factors Enhancing Serum Syndecan-1 Concentrations: A Large-Scale Comprehensive Medical Examination

Endothelial disorders are related to various diseases. An initial endothelial injury is characterized by endothelial glycocalyx injury. We aimed to evaluate endothelial glycocalyx injury by measuring serum syndecan-1 concentrations in patients during comprehensive medical examinations. A single-center, prospective, observational study was conducted at Asahi University Hospital. The participants enrolled in this study were 1313 patients who underwent comprehensive medical examinations at Asahi University Hospital from January 2018 to June 2018. One patient undergoing hemodialysis was excluded from the study. At enrollment, blood samples were obtained, and study personnel collected demographic and clinical data. No treatments or exposures were conducted except for standard medical examinations and blood sample collection. Laboratory data were obtained by the collection of blood samples at the time of study enrolment. According to nonlinear regression, the concentrations of serum syndecan-1 were significantly related to age (p = 0.016), aspartic aminotransferase concentration (AST, p = 0.020), blood urea nitrogen concentration (BUN, p = 0.013), triglyceride concentration (p < 0.001), and hematocrit (p = 0.006). These relationships were independent associations. Endothelial glycocalyx injury, which is reflected by serum syndecan-1 concentrations, is related to age, hematocrit, AST concentration, BUN concentration, and triglyceride concentration.

Molecular targets and signaling pathways regulated by nuclear translocation of syndecan-1

Background

The cell-surface heparan sulfate proteoglycan syndecan-1 is important for tumor cell proliferation, migration, and cell cycle regulation in a broad spectrum of malignancies. Syndecan-1, however, also translocates to the cell nucleus, where it might regulate various molecular functions.

Results

We used a fibrosarcoma model to dissect the functions of syndecan-1 related to the nucleus and separate them from functions related to the cell-surface. Nuclear translocation of syndecan-1 hampered the proliferation of fibrosarcoma cells compared to the mutant lacking nuclear localization signal. The growth inhibitory effect of nuclear syndecan-1 was accompanied by significant accumulation of cells in the G0/G1 phase, which indicated a possible G1/S phase arrest.

We implemented multiple, unsupervised global transcriptome and proteome profiling approaches and combined them with functional assays to disclose the molecular mechanisms that governed nuclear translocation and its related functions. We identified genes and pathways related to the nuclear compartment with network enrichment analysis of the transcriptome and proteome. The TGF-β pathway was activated by nuclear syndecan-1, and three genes were significantly altered with the deletion of nuclear localization signal: EGR-1 (early growth response 1), NEK11 (never-in-mitosis gene a-related kinase 11), and DOCK8 (dedicator of cytokinesis 8). These candidate genes were coupled to growth and cell-cycle regulation. Nuclear translocation of syndecan-1 influenced the activity of several other transcription factors, including E2F, NFκβ, and OCT-1. The transcripts and proteins affected by syndecan-1 showed a striking overlap in their corresponding biological processes. These processes were dominated by protein phosphorylation and post-translation modifications, indicative of alterations in intracellular signaling. In addition, we identified molecules involved in the known functions of syndecan-1, including extracellular matrix organization and transmembrane transport.

Conclusion

Collectively, abrogation of nuclear translocation of syndecan-1 resulted in a set of changes clustering in distinct patterns, which highlighted the functional importance of nuclear syndecan-1 in hampering cell proliferation and the cell cycle. This study emphasizes the importance of the localization of syndecan-1 when considering its effects on tumor cell fate.

Electronic supplementary material

The online version of this article (10.1186/s12860-017-0150-z) contains supplementary material, which is available to authorized users.

Hepatic syndecan-1 changes associate with dyslipidemia after renal transplantation

Syndecan-1 is a transmembrane heparan sulfate (HS) proteoglycan present on hepatocytes and involved in uptake of triglyceride-rich lipoproteins via its HS polysaccharide side chains. We hypothesized that altered hepatic syndecan-1 metabolism could be involved in dyslipidemia related to renal transplantation. In a rat renal transplantation model elevated plasma triglycerides were associated with fivefold increased expression of hepatic syndecan-1 mRNA (p < 0.01), but not protein. Expression of syndecan-1 sheddases (ADAM17, MMP9) and heparanase was significantly up-regulated after renal transplantation (all p < 0.05). Profiling of HS side chains revealed loss of hepatic HS upon renal transplantation accompanied by significant decreased functional capacity for VLDL binding (p = 0.02). In a human renal transplantation cohort (n = 510), plasma levels of shed syndecan-1 were measured. Multivariate analysis showed plasma syndecan-1 to be independently associated with triglycerides (p < 0.0001) and inversely with HDL cholesterol (p < 0.0001). Last, we show a physical association of syndecan-1 to HDL from renal transplant recipients (RTRs), but not to HDL from healthy controls. Our data suggest that after renal transplantation loss of hepatic HS together with increased syndecan-1 shedding hampers lipoprotein binding and uptake by the liver contributing to dyslipidemia. Our data open perspectives toward improvement of lipid profiles by targeted inhibition of syndecan-1 catabolism in renal transplantation.

Negative correlation between serum syndecan-1 and apolipoprotein A1 in patients with type 2 diabetes mellitus

Heparan sulfate proteoglycans (HSPGs) are involved in the regulation of cell growth, apoptosis and lipid metabolism in vitro. Syndecans are the primary form of HSPGs. Syndecan-1 is involved in the processes of cell growth, differentiation, adhesion, wound healing and inflammation. Additionally, as a sinusoidal transmembrane HSPG facing the plasma compartment, syndecan-1 is a promising target to be involved in lipoprotein physiology. We aimed to examine the possible correlation of syndecan-1 and lipid profile in type 2 diabetes mellitus. In this study, serum syndecan-1 was detected by ELISA, and potential correlations between syndecan-1 and triglyceride, cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, lipoprotein a, apolipoprotein (apo) B, apoA1 and apoB/apoA1 were analyzed. Forty-one patients with type 2 diabetes and 31 age-matched, non-diabetic healthy subjects (controls) were enrolled. Syndecan-1 in patients with diabetes (26.15 ± 2.42 ng/ml) was significantly higher than that of the controls (16.85 ± 1.98 ng/ml, t = -2.98, P = 0.005). Serum syndecan-1 level correlated negatively with apoA1 (r = -0.46, P = 0.003). Multiple regression analysis showed that apoA1 (b = -0.43, P = 0.003) was a predictor of serum syndecan-1 levels in subjects with type 2 diabetes.

Enhanced syndecan-1 expression on neutrophils in patients with type 2 diabetes mellitus

The peripheral neutrophils are one of the main inflammatory cells and significantly influence the damage of endothelium. Type 2 diabetes is a manifestation of an ongoing low-grade inflammation. In diabetes, impairment of neutrophil adhesion to the endothelium and migration to the site of inflammation were detected, which associated closely with adhesion molecules expressed on neutrophils and endothelial cells. To detect the expression of syndecan-1 on neutrophils in patients with type 2 diabetes mellitus, we recruited 29 patients with type 2 diabetes mellitus without any diabetic complication and 24 healthy subjects (controls). Expression of syndecan-1 was determined by flow cytometry, and potential correlations between syndecan-1 and clinical characteristics were analyzed. On neutrophils, percentage of positive syndecan-1 cells was significantly higher in subjects with diabetes (10.363 ± 1.689%) than that of the controls (3.775 ± 0.634%, P = 0.001). An association between body mass index (BMI) and percentage of positive syndecan-1 neutrophils was detected (r = 0.415, P = 0.025). When BMI was categorized into subgroups of ≤25 kg/m(2) (n = 10) and >25 kg/m(2) (n = 19), the average percentages of positive syndecan-1 neutrophils in patients with diabetes were 5.733 ± 1.842% and 12.642 ± 2.251%, respectively (t = -2.137, P = 0.042). A multiple regression analysis showed that BMI (β = 0.783, P < 0.000) was a significant predictor of positive syndecan-1 neutrophils in subjects with type 2 diabetes.

Hepatic heparan sulfate proteoglycans and endocytic clearance of triglyceride-rich lipoproteins

Hypertriglyceridemia, characterized by the accumulation of triglyceride-rich lipoproteins in the blood, affects 10-20% of the population in western countries and increases the risk of atherosclerosis, coronary artery disease, and pancreatitis. The etiology of hypertriglyceridemia is complex, and much interest exists in identifying and characterizing the biological and environmental factors that affect the synthesis and turnover of plasma triglycerides. Genetic studies in mice have recently identified that heparan sulfate proteoglycans are a class of receptors that mediate the clearance of triglyceride-rich lipoproteins in the liver. Heparan sulfate proteoglycans are expressed by endothelial cells that line the hepatic sinusoids and the underlying hepatocytes, and are present in the perisinusoidal space (space of Disse). This chapter discusses the dependence of lipoprotein binding on heparan sulfate structure and the identification of hepatocyte syndecan-1 as the primary proteoglycan that mediates triglyceride-rich lipoprotein clearance.

Effect of syndecan-1 overexpression on mesenchymal tumour cell proliferation with focus on different functional domains

OBJECTIVES

Syndecan-1 is a transmembrane proteoglycan involved in various biological processes. Its extracellular, transmembrane and cytoplasmic domains may all participate in signal transduction. The aim of this study was to investigate the biological roles of these domains of syndecan-1.

MATERIALS AND METHODS

We transfected cells of two mesenchymal tumour cell lines with a full-length syndecan-1 construct and three truncated variants, namely 78 construct lacking the EC domain with exception of DRKE sequence; 77 construct lacking extracellular the whole domain and RMKKK corresponding to a short cytoplasmic motif. Subcellular distribution was revealed using confocal laser microscopy. Overexpression of the constructs was verified using real-time RT-PCR and by FACS analysis and effects of syndecan-1 on cell behaviour were explored. Cell cycle analysis allowed for dissection of mechanisms regulating cell proliferation.

RESULTS

Overexpression of syndecan-1 influenced expression profile of the other syndecan members, and decreased tumour cell proliferation significantly by two mechanisms, as follows: increased length of G0/G1 phase was the most evident change in RMKKK and 77 transfectants, whereas prolonged S phase was more obvious in full-length transfectants. Overexpression of syndecan-1 changed the tumour cell morphology in an epithelioid direction.

CONCLUSIONS

Both full-length and truncated syndecan-1 inhibited proliferation of the mesenchymal tumour cells, providing new insights into the importance for cancer growth of different functional domains of this proteoglycan.

Syndecan-1 is the primary heparan sulfate proteoglycan mediating hepatic clearance of triglyceride-rich lipoproteins in mice

Elevated plasma triglyceride levels represent a risk factor for premature atherosclerosis. In mice, accumulation of triglyceride-rich lipoproteins can occur if sulfation of heparan sulfate in hepatocytes is diminished, as this alters hepatic lipoprotein clearance via heparan sulfate proteoglycans (HSPGs). However, the relevant HSPG has not been determined. In this study, we found by RT-PCR analysis that mouse hepatocytes expressed the membrane proteoglycans syndecan-1, -2, and -4 and glypican-1 and -4. Analysis of available proteoglycan-deficient mice showed that only syndecan-1 mutants (Sdc1-/- mice) accumulated plasma triglycerides. Sdc1-/- mice also exhibited prolonged circulation of injected human VLDL and intestinally derived chylomicrons. We found that mice lacking both syndecan-1 and hepatocyte heparan sulfate did not display accentuated triglyceride accumulation compared with single mutants, suggesting that syndecan-1 is the primary HSPG mediating hepatic triglyceride clearance. Immunoelectron microscopy showed that syndecan-1 was expressed specifically on the microvilli of hepatocyte basal membranes, facing the space of Disse, where lipoprotein uptake occurs. Abundant syndecan-1 on wild-type murine hepatocytes exhibited saturable binding of VLDL and inhibition by heparin and facilitated degradation of VLDL. Furthermore, adenovirus-encoded syndecan-1 restored binding, uptake, and degradation of VLDL in isolated Sdc1-/- hepatocytes and the lipoprotein clearance defect in Sdc1-/- mice. These findings provide the first in vivo genetic evidence that syndecan-1 is the primary hepatocyte HSPG receptor mediating the clearance of both hepatic and intestinally derived triglyceride-rich lipoproteins.

Heparan sulfate proteoglycans and triglyceride-rich lipoprotein metabolism

PURPOSE OF REVIEW

Clearance of triglyceride-rich lipoprotein remnants by the liver is a key step in preventing hypertriglyceridemia, an independent risk factor for cardiovascular disease. We review recent genetic evidence that heparan sulfate proteoglycans work in concert with the LDL receptor in the liver to facilitate binding and clearance of both triglyceride and cholesterol-rich lipoproteins from the circulation.

RECENT FINDINGS

Partial reduction of sulfation of liver heparan sulfate using the Cre-loxP system caused accumulation of hepatic and dietary triglyceride-rich lipoprotein particles due to delayed clearance. Compounding the mutation with LDL receptor deficiency caused enhanced accumulation of both cholesterol and triglyceride-rich particles compared with mice lacking only LDL receptors. These findings provide the first genetic evidence that hepatic heparan sulfate proteoglycans play a central role in the clearance of lipoproteins by the liver and work independently of LDL receptors.

SUMMARY

A role for hepatocyte heparan sulfate in lipoprotein metabolism has now been genetically established in mice. Given this finding, mild, but clinically relevant, hyperlipidemias in human patients may be a result of alterations in heparan sulfate structure or possible genetic polymorphisms in the relevant biosynthetic genes.