mTORC1 Down-Regulates Cyclin-Dependent Kinase 8 (CDK8) and Cyclin C (CycC).

In non-alcoholic fatty liver disease (NAFLD) and insulin resistance, hepatic de novo lipogenesis is often elevated, but the underlying mechanisms remain poorly understood. Recently, we show that CDK8 functions to suppress de novo lipogenesis. Here, we identify the mammalian target of rapamycin complex 1 (mTORC1) as a critical regulator of CDK8 and its activating partner CycC. Using pharmacologic and genetic approaches, we show that increased mTORC1 activation causes the reduction of the CDK8-CycC complex in vitro and in mouse liver in vivo. In addition, mTORC1 is more active in three mouse models of NAFLD, correlated with the lower abundance of the CDK8-CycC complex. Consistent with the inhibitory role of CDK8 on de novo lipogenesis, nuclear SREBP-1c proteins and lipogenic enzymes are accumulated in NAFLD models. Thus, our results suggest that mTORC1 activation in NAFLD and insulin resistance results in down-regulation of the CDK8-CycC complex and elevation of lipogenic protein expression.

Selective antileukemia effect of stabilized nanohybrid vesicles based on cholesteryl succinyl silane.

A nanohybrid vesicle was developed from cholesteryl succinyl silane(CSS) in combination of sol-gel process and self-assembly technique. The silicalike surface adds CSS vesicles remarkably high stability against destabilization in blood or leakage of drug cargos. It was found that CSS vesicles alone exhibited selective antiproliferative effects on leukemia cells without destroying normal blood cells. In addition, they are able to encapsulate not only hydrophilic guest species inside the inner water compartment but also hydrophobic molecules in the cholesteryl succinyl bilayer membrane. More importantly, CSS vesicles loaded with doxorubicin enhanced the anticancer efficiency of cancer therapeutics greatly while minimizing the use of inactive materials and lowering the exposure of normal cells to toxic side effects. This makes CSS vesicle a promising carrier for the treatment of cancer, especially for leukemia.

Liposomal architecture boosts biocompatibility of nanohybrid cerasomes.

Biomimetic cerasome has drawn much attention as a novel drug delivery system because its atomic layer of polyorganosiloxane surface imparts higher morphological stability than conventional liposomes and its liposomal bilayer structure reduces the overall rigidity and density greatly compared to silica nanoparticles. But, the issues about the interactions between cerasomes and biological systems have not been addressed as far as we could find. Herein, we reported cellular uptake of cerasomes and their biological effects toward human umbilical vein endothelial cells (HUVECs) compared with silica nanoparticles. The results indicated that the uptake of cerasomes by HUVECs was a concentration-, time-, and energy-dependent process and occurred probably through a process of clathrin-mediated endocytosis, which resulted in rearrangement of the cell cytoskeleton. Cerasomes affected different aspects of cell function to a smaller extent than silica nanoparticles, including cell proliferation, cell cycle, cell apoptosis, endogenous ROS level and pro-inflammatory molecular expression. In a word, cerasomes are more biocompatible than silica nanoparticles due to the incorporation of the liposomal architecture into cerasomes. The preliminary data will assist in the further development of new cerasome-based delivery systems.

Modified heparins inhibit integrin alpha(IIb)beta(3) mediated adhesion of melanoma cells to platelets in vitro and in vivo.

The adhesion of tumor cells with platelets is important in the process of tumor metastasis. A huge work has indicated that anti-adhesion is an effective strategy for metastasis inhibition. In this article, we assess the role of platelet integrin alpha(IIb)beta(3) in adhesion of melanoma cells to platelets and the effects of heparin and modified heparins on the adhesion in vitro and in vivo. We show that platelet integrin alpha(IIb)beta(3) is involved in the interaction of human melanoma A375 cells with platelets, and the high affinity epitope resides on the alpha(IIb) subunit rather than beta(3) subunit. Heparin sulfate-like proteoglycans on tumor cell surface are implicated in the adhesion of A375 cells to integrin alpha(IIb)beta(3). We also show that RO-heparin, CR-heparin, N-2,3-DS-heparin and 2,3-O-DS-heparin can significantly inhibit A375 cells binding to the CHO cells expressing integrin alpha(IIb)beta(3) under static and flow conditions, and remarkably inhibit the adhesion of A375 cells to the immobilized platelet layers under flow conditions. We find that A375 cells and B16F10 cells are arrested in the pulmonary vessels and adhered to platelets, and the initial interaction of tumor cells with platelets in lung vessel and long-term establishment of metastatic foci can be inhibited by heparin as well as CR-heparin and N-2,3-DS-heparin. These data suggest that modified heparins can inhibit tumor cell-platelet interaction mediated by platelet integrin alpha(IIb)beta(3) and modified heparins may be a potential substitute for heparin in inhibiting tumor metastasis.

Inhibitory effects of chemically modified heparin on the P-selectin-mediated adhesion of breast cancer cells in vitro.

P-selectin plays a crucial role during hematogenous metastasis, and the blockade of P-selectin binding to its ligand can attenuate metastasis in various tumor models. Heparin or chemically modified heparins with decreased anticoagulant activities exhibit marked inhibitory effects on P-selectin-mediated adhesion. Here, we prepared chemically modified heparins with reduced anticoagulant activities and investigated whether they effectively inhibited P-selectin binding to breast cancer cells under static and flow conditions. The results indicated that P-selectin binding to ZR-75-30 cells was attenuated by chemically modified heparins in a sulfation-dependent manner under static and flow conditions. Flow cytometric analysis with heparan sulfate-specific monoclonal antibody revealed that heparan sulfate-like proteoglycans on the tumor cell surface were not implicated in this process. Instead, other glycoproteins were found to serve as P-selectin ligands. These findings suggest that further detailed research involving chemically modified heparins with low or no anti-coagulant activities is warranted, and that chemically modified heparins should be considered in the treatment of metastatic breast cancer disease, with P-selectin potentially being a good target.

Novel hollow microcapsules based on iron-heparin complex multilayers.

Iron-polysaccharide complex have been extensively utilized in the treatment of iron deficiency anemia for parenteral administration. Herein, a novel iron-heparin complexed hollow capsules with nanoscaled wall thickness have been fabricated by means of alternating deposition of ferric ions (III) (Fe+) and heparin (Hep) onto the surface of submicroscaled (488 nm) and microscaled (10.55 microm) polystyrene latex particles via both electrostatic interaction and chemical complexation processes, followed by dissolution of the cores using tetrahydrofuran. Confocal micrographs and atomic force microscopy (AFM) images prove that iron-heparin complexed submicroscaled hollow capsules keep spherical shapes in solution and even after drying. The activated partial thromboplastin time (APTT) assay shows that complexing with ferric ions do not compromise the catalytic capacity of heparin to promote antithrombin III-mediated thrombin inactivation. The anticoagulant activity value of (Fe3+/Hep)8 capsules is evaluated to be about 95.7 U/mg, indicating that approximately 0.55 mg heparin was in 1 mg powder of submicroscaled (Fe3+/Hep)8 hollow capsules. Compared with the same dosage of heparin, iron-heparin complexed hollow capsules display a more prolonged anticoagulant duration than heparin. All these results reveal that such submicroscaled iron-heparin complexed hollow capsules have application potential as an injectable anticoagulant vehicle.

Purified polysaccharide from Ginkgo biloba leaves inhibits P-selectin-mediated leucocyte adhesion and inflammation.

AIM: To investigate the anti-inflammatory mechanism of the polysaccharides of Ginkgo biloba leaves (PGBL) by inhibiting leucocyte adhesion. METHODS: The rough PGBL were isolated and purified. The anti-inflammatory effects of purified PGBL (p-PGBL) were assayed by ear edema induced by xylol and the acute peritonitis model in mice. The effect of p-PGBL on inhibiting the interaction between P-selectin and its ligands was investigated by flow cytometry and flow chamber. RESULTS: p-PGBL could effectively inhibit the acute inflammation in mice and interfere with the adhesion of HL-60 cells, a human leukaemia cell line, or neutrophils to P-selectin in static conditions, as well as the adhesion of neutrophils to Chinese hamster ovary cells expressing human P-selectin and human umbilical vein endothelial cells in flow conditions in a dose-dependant manner. CONCLUSIONS: p-PGBL can inhibit the inflammatory process through interfering with the interaction between P-selectin and its ligands.

Chemically modified heparin inhibits the in vitro adhesion of nonsmall cell lung cancer cells to P-selectin.

PURPOSE: Several independent studies have indicated that tumor metastasis can be inhibited by chemically modified heparin with low anticoagulant activity in the different tumor models. The mechanism of inhibition by the heparin derivatives in part accounts for the interference of tumor cell-platelet interaction mediated by P-selectin. METHODS: In the present study, we demonstrated that both heparin and chemically modified heparins inhibited the adhesion of nonsmall cell lung cancer (NSCLC) cells to P-selectin under static or flow conditions in vitro. RESULTS: Flow cytometric analysis with the heparan sulfate-specific monoclonal antibody revealed that both NSCLC cells express heparan sulfate-like proteoglycans. Furthermore, heparinase treatment impaired P-selectin binding, indicating that heparan sulfate-like proteoglycans on the tumor cell surface are implicated in the adhesion of NSCLC cells to P-selectin. CONCLUSIONS: These findings suggest that some chemically modified heparins with low anticoagulant activity may deserve further testing in the experimental NSCLC treatment protocols.

Engagement of PSGL-1 upregulates CSF-1 transcription via a mechanism that may involve Syk.

PSGL-1, the optimal selectin ligand demonstrated by in vivo studies to date, is an essential adhesive molecule mediating the rolling of leukocytes on the endothelial cells and the recruitment of leukocytes to the inflamed tissue. Recent studies demonstrated, in addition to its direct role in capture of leukocytes from the bloodstream, PSGL-1 also functions as a signal-transducing receptor and initiates a series of intracellular signal events during the activation of leukocytes. Our present work showed antibody engagement of PSGL-1 upregulated the transcriptional activity of CSF-1 promotor and increased the endogenous expression of CSF-1 mRNA in Jurkat cell. Overexpression of wild-typed non-receptor tyrosine kinase Syk, but not kinase dead mutant of Syk, promoted the upregulation of the transcriptional activity of CSF-1 promoter caused by antibody engagement of PSGL-1. Additionally, special inhibitor of Syk Piceatannol suppressed the increase of CSF-1 mRNA caused by the engagement of PSGL-1. The results suggest that signal transducted by PSGL-1 upregulate the transcriptional activity of CSF-1, and non-receptor tyrosine kinase Syk participates in this pathway.

Selectively desulfated heparin inhibits P-selectin-mediated adhesion of human melanoma cells.

Accumulating evidence has suggested that one of the mechanisms by which heparin inhibits metastasis is by blocking the P-selectin-based interaction of platelets with tumor cells. Here we demonstrate that the sulfate groups at C6/N and especially C6, but not C2 and C3, of heparin play a critical role in P-selectin recognition and that 2-O,3-O-desulfated heparin can block P-selectin-mediated A375 human melanoma cell adhesion. Our findings show that chemical modification of heparin, especially 2-O,3-O-desulfation, may result in a therapeutic agent that is anti-metastatic because it blocks unwanted P-selectin-dependent adhesion but that lacks dose-limiting anticoagulant effects.

P-Selectin-mediated acute inflammation can be blocked by chemically modified heparin, RO-heparin.

Selectins are carbohydrate-binding cell adhesion molecules that play a major role in the initiation of inflammatory responses. Heparin can bind to P-selectin, and its anti-inflammatory property is mainly due to inhibition of P-selectin. However, the strong anticoagulant activity of heparin limits its clinical use. We prepared periodate-oxidized, borohydride-reduced heparin (RO-heparin) by chemical modification and tested its anticoagulant and anti-inflammatory activities. Activated partial thromboplastin time (aPTT) assays showed that, compared with heparin, RO-heparin had greatly reduced anticoagulant activity. Intravenous administration of this compound led to reduction in the peritoneal infiltration of neutrophils in a mouse acute inflammation model. In vitro cell adhesion experiments demonstrated that the effect of RO-heparin on inflammatory responses was mainly due to inhibiting the interaction of P-selectin with its ligands. These results indicate that RO-heparin may be a safer treatment for inflammation than heparin, especially when selectin is targeted.

Signaling function of PSGL-1 in neutrophil: tyrosine-phosphorylation-dependent and c-Abl-involved alteration in the F-actin-based cytoskeleton.

P-selectin glycoprotein ligand-1 (PSGL-1) is the best-characterized selectin ligand that has been demonstrated to mediate leukocytes rolling on endothelium and leukocytes recruitment into inflamed tissue in vivo. In addition to its direct role in leukocyte capturing, PSGL-1 also functions as a signal-transducing receptor. The present work showed that after cross-linking of PSGL-1 with KPL1, an anti-PSGL-1 monoclonal antibody, PSGL-1 linked to the cytoskeleton and became a detergent-insoluble component in activated neutrophils. The antibody cross-linking led to the polymerization and redistribution of F-actin-based cytoskeleton, and this alteration of cytoskeleton was spatiotemporally related to the polarization of PSGL-1. PSGL-1's polarization was cytoskeleton-dependent because it was eliminated by cytochalasin B. Furthermore, the polymerization and redistribution of F-actin filaments were tyrosine-phosphorylation-dependent since the alteration of F-actin-based cytoskeleton was severely blocked by genistein, a universal tyrosine kinase inhibitor. STI571, a small molecule inhibitor for cytoplasmic tyrosine kinase c-Abl, also inhibited the alteration of F-actin-based cytoskeleton, and c-Abl was redistributed to where F-actin concentrated in the activated neutrophils. The results suggested that cross-linking of PSGL-1 induces the phosphorylation-dependent and c-Abl-involved alteration of F-actin-based cytoskeleton in neutrophils.

Modified heparin inhibits P-selectin-mediated cell adhesion of human colon carcinoma cells to immobilized platelets under dynamic flow conditions.

Accumulating evidence indicates that the formation of tumor cell platelet emboli complexes in the blood stream is a very important step during metastases and that the anti-metastasis effects of heparin are partially due to a blockade of P-selectin on platelets. In this study, heparin and chemically modified heparins were tested as inhibitors of three human colon carcinoma cell lines (COLO320, LS174T, and CW-2) binding to P-selectin, adhering to CHO cells expressing a transfected human P-selectin cDNA, and adhering to surface-anchored platelets expressing P-selectin under static and flow conditions. The aim was to screen for heparin derivatives with high anti-adhesion activity but negligible anticoagulant activity. In this study, four modified heparins with high anti-adhesion activity were identified including RO-heparin, CR-heparin, 2/3ODS-heparin, and N/2/3DS-heparin. NMR analysis proved the reliability of structure of the four modified heparins. Our findings suggested that the 6-O-sulfate group of glucosamine units in heparin is critical for the inhibition of P-selectin-mediated tumor cell adhesion. Heparan sulfate-like proteoglycans on these tumor cell surfaces are implicated in adhesion of the tumor cells to P-selectin. Some chemically modified heparins with low anticoagulant activities, such as 2/3ODS-heparin, may have potential value as therapeutic agents that block P-selectin-mediated cell adhesion and prevent tumor metastasis.