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Protein tyrosine phosphatase 1B (PTP1B) is a key molecule in modulating low-degree inflammatory conditions such as diabetes. The role of PTP1B in other chronic inflammations, however, remains unknown. Here, we report that PTP1B deficiency ameliorates Dextran Sulfate Sodium (DSS)-induced murine experimental colitis via expanding CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs). Employing DSS-induced murine experimental colitis as inflammatory animal model, we found that, compared with wild-type littermates, PTP1B-null mice demonstrated greater resistance to DSS-induced colitis, as reflected by slower weight-loss, greater survival rates and decreased PMN and macrophage infiltration into the colon. The evidence collectively also demonstrated that the resistance of PTP1B-null mice to DSS-induced colitis is based on the expansion of MDSCs. First, PTP1B-null mice exhibited a greater frequency of MDSCs in the bone marrow (BM), peripheral blood and spleen when compared with wild-type littermates. Second, PTP1B levels in BM leukocytes were significantly decreased after cells were induced into MDSCs by IL-6 and GM-CSF, and the MDSC induction occurred more rapidly in PTP1B-null mice than in wild-type littermates, suggesting PTP1B as a negative regulator of MDSCs. Third, the adoptive transfer of MDSCs into mice with DSS-colitis significantly attenuated colitis, which accompanies with a decreased serum IL-17 level. Finally, PTP1B deficiency increased the frequency of MDSCs from BM cells likely through enhancing the activities of signal transducer and activator of transcription 3 (STAT3) and Janus kinase 2 (JAK2). In conclusion, our study provides the first evidences that PTP1B deficiency ameliorates murine experimental colitis via expanding MDSCs.

This study aimed to identify major proteins in the pathogenesis of coronary artery in-stent restenosis (ISR) in diabetic minipigs with sirolimus-eluting stenting, and to investigate the roles of key candidate molecules, particularly ADAM10, in human arterial smooth muscle cells (HASMCs).The stents were implanted in the coronary arteries of 15 diabetic and 26 non-diabetic minipigs, and angiography was repeated at six months. The intima of one vascular segment with significant ISR and one with non-ISR in diabetic minipigs were isolated and cultured in conditioned medium (CM). The CM was analyzed by LC-MS/MS to uncover proteins whose levels were significantly increased (≥ 1.5-fold) in ISR than in non-ISR tissues. After literature searching, we focused on the identified proteins, whose biological functions were most potentially related to ISR pathophysiology. Among them, ADAM10 was significantly increased in diabetic and non-diabetic ISR tissues as compared with non-ISR controls. In cell experiments, retrovirus-mediated overexpression of ADAM10 promoted growth and migration of HASMCs. The effects of ADAM10 were more remarkable in high-glucose culture than in low-glucose culture. Using shRNA and an inhibitor of γ-secretase (GSI), we found that the influences of ADAM10 were in part mediated by Notch1 and notch 3 pathway, which up-regulated Notch downstream genes and enhanced nuclear translocation of the small intracellular component of Notch1 and Notch3.This study has identified significantly increased expression of ADAM10 in the ISR versus non-ISR segment in diabetic minipigs and implicates ADAM10 in the enhanced neointimal formation observed in diabetes after vascular injury.

SIRPα, an ITIMs-containing signaling receptor, negatively regulates leukocyte responses through extracellular interactions with CD47. However, the dynamics of SIRPα-CD47 interactions on the cell surface and the governing mechanisms remain unclear. Here we report that while the purified SIRPα binds to CD47 and that SIRPα is expressed on monocytes and monocytic THP-1 or U937, these SIRPα are ineffective to mediate cell binding to immobilized CD47. However, cell binding to CD47 is significantly enhanced when monocytes transmigrating across endothelia, or being differentiated into macrophages. Cell surface labeling reveals SIRPα to be diffused on naïve monocytes but highly clustered on transmigrated monocytes and macrophages. Protein crosslink and equilibrium centrifugation confirm that SIRPα in the latter cells forms oligomerized complexes resulting in increased avidity for CD47 binding. Furthermore, formation of SIRPα complexes/clusters requires the plasma membrane 'lipid rafts' and the activity of Src family kinase during macrophage differentiation. These results together suggest that 'clustering' SIRPα into plasma membrane microdomains is essential for activated monocytes and macrophages to effectively interact with CD47 and initiate intracellular signaling.

Cell-secreted miRNAs are highly stable and can serve as biomarkers for various diseases and signaling molecules in intercellular communication. The mechanism underlying the stability of circulating miRNAs, however, remains incompletely understood. Here we show that Argonaute 2 (Ago2) complexes and microvesicles (MVs) provide specific and non-specific protection for miRNA in cell-secreted MVs, respectively. First, the resistance of MV-encapsulated miRNAs to RNaseA was both depended on intact vesicular structure of MVs and protease-sensitive. Second, an immunoprecipitation assay using a probe complementary to human miR-16, a miRNA primarily located in the MVs and showed a strong, protease-sensitive resistance to RNaseA, identified Ago2 as a major miR-16-associated protein. Compared with protein-free miR-16, Ago2-associated miR-16 was resistant to RNaseA in a dose- and time-dependent fashion. Third, when the miR-16/Ago2 complex was disrupted by trypaflavine, the resistance of miR-16 to RNaseA was decreased. In contrast, when the association of miR-16 with the Ago2 complexes was increased during cell apoptosis, although the total amount of miR-16 and Ago2 remained unchanged, the resistance of miR-16 to RNaseA in the MVs was enhanced. A similar correlation between the increase of miR-223/Ago2 association and the resistance of miR-223 against RNaseA was observed during all trans retinoic acid (ATRA)-induced cell differentiation of promyelocytic HL60 cells. In conclusion, the association of miRNAs with Ago2 complexes, an event that is linked to cell functional status, plays a critical role in stabilizing the circulating miRNAs in cell-secreted MVs.

BACKGROUND: Platelet depletion is a key feature of hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC) infection. The mechanism underlying STEC-induced platelet depletion, however, is not completely understood. METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrated for the first time that platelet surface expression of CD47 was significantly decreased in C57BL6 mice treated with concentrated culture filtrates (CCF) from STEC O157:H7. STEC O157:H7 CCF treatment also led to a sharp drop of platelet counts. The reduction of cell surface CD47 was specific for platelets but not for neutrophil, monocytes and red blood cells. Down-regulation of platelet surface CD47 was also observed in isolated human platelets treated with O157:H7 CCF. Platelet surface CD47 reduction by O157:H7 CCF could be blocked by anti-TLR4 antibody but not anti-CD62 antibody. Down-regulation of platelet surface CD47 was positively correlated with platelet activation and phagocytosis by human monocyte-derived macrophages. Furthermore, the enhanced phagocytosis process of O157:H7 CCF-treated platelets was abolished by addition of soluble CD47 recombinants. CONCLUSIONS/SIGNIFICANCE: Our results suggest that platelet CD47 down-regulation may be a novel mechanism underneath STEC-induced platelet depletion, and that the interactions between CD47 and its receptor, signal regulatory protein alpha (SIRPalpha), play an essential role in modulating platelet homeostasis.

BACKGROUND: Signal regulate protein alpha (SIRPalpha) is involved in many functional aspects of monocytes. Here we investigate the role of SIRPalpha in regulating beta(2) integrin-mediated monocyte adhesion, transendothelial migration (TEM) and phagocytosis. METHODOLOGY/PRINCIPAL FINDINGS: THP-1 monocytes/macropahges treated with advanced glycation end products (AGEs) resulted in a decrease of SIRPalpha expression but an increase of beta(2) integrin cell surface expression and beta(2) integrin-mediated adhesion to tumor necrosis factor-alpha (TNFalpha)-stimulated human microvascular endothelial cell (HMEC-1) monolayers. In contrast, SIRPalpha overexpression in THP-1 cells showed a significant less monocyte chemotactic protein-1 (MCP-1)-triggered cell surface expression of beta(2) integrins, in particular CD11b/CD18. SIRPalpha overexpression reduced beta(2) integrin-mediated firm adhesion of THP-1 cells to either TNFalpha-stimulated HMEC-1 monolayers or to immobilized intercellular adhesion molecule-1 (ICAM-1). SIRPalpha overexpression also reduced MCP-1-initiated migration of THP-1 cells across TNFalpha-stimulated HMEC-1 monolayers. Furthermore, beta(2) integrin-mediated THP-1 cell spreading and actin polymerization in response to MCP-1, and phagocytosis of bacteria were both inhibited by SIRPalpha overexpression. CONCLUSIONS/SIGNIFICANCE: SIRPalpha negatively regulates beta(2) integrin-mediated monocyte adhesion, transendothelial migration and phagocytosis, thus may serve as a critical molecule in preventing excessive activation and accumulation of monocytes in the arterial wall during early stage of atherosclerosis.