Inhibition Of P-selectin Glycoprotein Ligand-1 Research Articles

P-Selectin Glycoprotein Ligand-1 Deficiency Protects Against Aortic Aneurysm Formation Induced by DOCA Plus Salt.

P-selectin glycoprotein ligand-1 (PSGL-1) acts as a crucial regulator for the inflammatory cells infiltration by mediating the adhesion of leukocytes. However, the role of PSGL-1 in aortic aneurysm remains elusive. Here, we investigated the role of PSGL-1 in aortic aneurysm (AA) development. We first detected PSGL-1 expression in samples from aortic aneurysm patients and mouse AA models via western blotting, immunofluorescence, and flow cytometry, and then we used global PSGL-1 knockout mice and their wild type controls to establish an aortic aneurysm model induced by deoxycorticosterone acetate (DOCA) plus high salt (HS). The incidence, fatality rates, and the pathological changes of aortic aneurysm were analyzed in each group. The inflammation, adhesion molecules expression, and PSGL-1 mediated leukocyte-endothelial adhesion and their underlying mechanisms were explored further. Increased PSGL-1 levels were observed in human and mouse aortic aneurysm, and on leukocytes of mice treated with DOCA+HS. PSGL-1 deficiency reduced the incidence and severity of aortic aneurysm significantly, as well as decreased elastin fragmentation, collagen accumulation, and smooth muscle cells degeneration. Mechanistically, the protective effect of PSGL-1 inhibition was mediated by the reduced adhesion molecules, and the subsequently reduced leukocyte-endothelial adhesion through the NF-κB pathway, which finally led to reduced inflammatory cells infiltration and decreased inflammatory factors expression. PSGL-1 deficiency is protective against inflammatory cells migration and recruitment in the condition of AA through attenuation of leukocyte-endothelial adhesion. Inhibition of PSGL-1 may be a potential therapeutic target for the prevention and treatment of human AA.

P-selectin glycoprotein ligand-1-mediated leukocyte recruitment regulates hepatocellular damage in acute obstructive cholestasis in mice

Leukocytes mediate hepatocellular injury in obstructive cholestasis. The aim of the present study was to define the role of P-selectin glycoprotein ligand-1 (PSGL-1) in cholestasis-induced leukocyte recruitment and liver damage. C57BL/6 mice were pre-treated with an anti-PSGL-1 antibody or a control antibody prior to bile duct ligation (BDL) for 12 h. Hepatic recruitment of leukocytes and sinusoidal perfusion were determined by means of intravital fluorescence microscopy. Liver damage was monitored by measuring serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Hepatic levels of CXC chemokines were determined by ELISA. BDL caused significant hepatocellular damage indicated by increased serum activities of ALT and AST as well as decreased sinusoidal perfusion and clear-cut hepatic infiltration of leukocytes. Administration of the anti-PSGL-1 antibody reduced BDL-induced levels of ALT by 78% and AST by 77%. Inhibition of PSGL-1 decreased BDL-provoked leukocyte rolling and adhesion in post-sinusoidal venules by more than 81%. Moreover, we found that immunoneutralisation of PSGL-1 restored sinusoidal perfusion and decreased hepatic formation of CXC chemokines in cholestatic mice. Our novel data show that PSGL-1 plays an important role in cholestatic liver damage by regulating leukocyte rolling in post-sinusoidal venules. Consequently, interference with PSGL-1 attenuates cholestasis-provoked leukocyte adhesion and extravasation in the liver. Thus, inhibition of PSGL-1 may help to protect against hepatocellular damage in cholestatic diseases.

P‐selectin glycoprotein‐ligand‐1 regulates pulmonary recruitment of neutrophils in a platelet‐independent manner in abdominal sepsis

Neutrophil-mediated lung injury is an insidious feature in sepsis although the mechanisms regulating pulmonary recruitment of neutrophils remain elusive. Here, we investigated the role of P-selectin glycoprotein-ligand-1 (PSGL-1) in sepsis-induced neutrophil recruitment and tissue injury in the lung. Bronchoalveolar infiltration of neutrophils, levels of myeloperoxidase, oedema formation and CXC chemokines were determined 24 h after caecal ligation and puncture (CLP) in mice. Animals were pretreated with a control antibody, monoclonal antibodies directed against PSGL-1 and P-selectin as well as a platelet-depleting antibody directed against GP1balpha. CLP caused pulmonary damage characterized by oedema formation, neutrophil infiltration and increased levels of CXC chemokines in the lung. Immunoneutralization of PSGL-1 or P-selectin reduced CLP-induced neutrophil recruitment in the bronchoalveolar space by more than 56% and lung myeloperoxidase activity by 62%. Notably, the inhibitory effect of the anti-PSGL-1 antibody on sepsis-induced neutrophil infiltration was also observed in platelet-depleted mice. Moreover, inhibition of PSGL-1 and P-selectin abolished CLP-induced oedema formation and tissue damage in the lung. CLP-induced formation of CXC chemokines was not changed in mice pretreated with the anti-PSGL-1 and anti-P-selectin antibodies. These data demonstrate that PSGL-1 plays a key role in pulmonary infiltration of neutrophils as well as lung oedema associated with abdominal sepsis. Moreover, our findings suggest that PSGL-1-dependent neutrophil recruitment is independent of circulating platelets. Thus, these novel findings indicate that PSGL-1 may be a useful target to protect against sepsis-induced accumulation of neutrophils and tissue damage in the lung.

PSGL-1–mediated activation of EphB4 increases the proangiogenic potential of endothelial progenitor cells

Endothelial progenitor cell (EPC) transplantation has beneficial effects for therapeutic neovascularization; however, only a small proportion of injected cells home to the lesion and incorporate into the neocapillaries. Consequently, this type of cell therapy requires substantial improvement to be of clinical value. Erythropoietin-producing human hepatocellular carcinoma (Eph) receptors and their ephrin ligands are key regulators of vascular development. We postulated that activation of the EphB4/ephrin-B2 system may enhance EPC proangiogenic potential. In this report, we demonstrate in a nude mouse model of hind limb ischemia that EphB4 activation with an ephrin-B2-Fc chimeric protein increases the angiogenic potential of human EPCs. This effect was abolished by EphB4 siRNA, confirming that it is mediated by EphB4. EphB4 activation enhanced P selectin glycoprotein ligand-1 (PSGL-1) expression and EPC adhesion. Inhibition of PSGL-1 by siRNA reversed the proangiogenic and adhesive effects of EphB4 activation. Moreover, neutralizing antibodies to E selectin and P selectin blocked ephrin-B2-Fc-stimulated EPC adhesion properties. Thus, activation of EphB4 enhances EPC proangiogenic capacity through induction of PSGL-1 expression and adhesion to E selectin and P selectin. Therefore, activation of EphB4 is an innovative and potentially valuable therapeutic strategy for improving the recruitment of EPCs to sites of neovascularization and thereby the efficiency of cell-based proangiogenic therapy.

PSGL-1 as a novel therapeutic target

The first events of leukocyte recruitment into the tissues are leukocyte tethering (capture) and rolling along the vessel wall, which are mediated primarily by selectins. P-selectin glycoprotein ligand-1 (PSGL-1) is a dimeric, mucin-type glycoprotein ligand expressed by all leukocytes and is a ligand for E-, P- and L-selectin. Quantitative and qualitative differences in the expression, affinity binding to the selectins and glycosylation of PSGL-1 between leukocyte subtypes suggest that potential PSGL-1 blockade should not have broad negative consequences in physiology and host defense. PSGL-1 has a well-documented role in organ targeting during inflammation in animal models, and inhibition of PSGL-1, though challenging, represents an attractive basis for antiinflammatory strategies. The consistent number of studies accumulated in the last 10 years since PSGL-1 was first characterized should induce us to ask whether we should put more effort into developing new drugs aimed to target more effectively PSGL-1 function in human diseases.

Platelet–monocyte complex formation: effect of blocking PSGL-1 alone, and in combination with αIIbβ3 and αMβ2, in coronary stenting

Background: Binding of platelet P-selectin to P-selectin glycoprotein ligand 1 (PSGL-1) is an initial event in the interactions between platelets and monocytes. Platelet–monocyte complexes (PMCs) have been implicated in several vascular disease processes, including acute coronary syndromes (ACS) and complications after percutaneous coronary intervention (PCI). We investigated the effect of ex vivo blockade of PSGL-1, alone and in combination with blockade of the αMβ 2 (Mac-1) and α IIbβ 3 (GP IIb/IIIa) integrins, on PMC formation. Methods and results: Dual-label flow cytometry was used to detect PMCs in the blood of 10 volunteers and 10 patients undergoing PCI who received intravenous GP IIb/IIIa antagonists. PSGL-1 blockade, both prior to and after platelet stimulation, markedly reduced the formation of PMCs. Concomitant ex vivo blockade of the αMβ 2 and α IIbβ 3 integrins did not result in further decreases of PMCs compared to PSGL-1 blockade alone. Antagonism of PSGL-1 also led to near elimination of leukocyte–platelet interactions under flowing conditions. Conclusion: Blockade of PSGL-1 alone is sufficient to inhibit and reverse the formation of PMCs following platelet stimulation. Concurrent antagonism of PSGL-1 and the α IIbβ 3 and αMβ 2 integrins was not more effective than inhibition of PSGL-1 alone. These results suggest that platelet–monocyte complex formation is mostly dependent on PSGL-1.