Claudine Kieda

Selective human endothelial cell activation by chemokines as a guide to cell homing

An original model of organo‐specific, immortalized and stabilized endothelial cell lines was used to delineate the part played by some chemokines (CCL21, CX3CL1, CCL5 and CXCL12) and their receptors in endothelium organo‐specificity. Chemokine receptor expression and chemokine presentation were investigated on organo‐specific human endothelial cell lines. Although the chemokines showed distinct binding patterns for the various endothelial cell lines, these were not correlated with the expression of the corresponding receptors (CX3CR1, CXCR4, CCR5 and CCR7). Experiments with CCL21 on peripheral lymph node endothelial cells demonstrated that the chemokine did not co‐localize with its receptor but was associated with extracellular matrix components. The specific activity of chemokines was clearly shown to be related to the endothelial cell origin. Indeed, CX3CL1 and CCL21 promoted lymphocyte recruitment by endothelial cells from the appendix and peripheral lymph nodes, respectively, while CX3CL1 pro‐angiogenic activity was restricted to endothelial cells from the appendix and skin. The high specificity of the chemokine/endothelium interaction allowed the design of a direct in vitro endothelial cell targeting assay. This unique cellular model demonstrated a fundamental role for chemokines in conferring on the endothelium its organo‐specificity and its potential for tissue targeting through the selective binding, presentation and activation properties of chemokines.

Receptor-mediated transcytosis of cyclophilin B through the blood-brain barrier

Abstract: Cyclophilin B (CyPB) is a cyclosporin A (CsA)‐binding protein mainly located in intracellular vesicles and secreted in biological fluids. In previous works, we demonstrated that CyPB interacts with T lymphocytes and enhances in vitro cellular incorporation and activity of CsA. In addition to its immunosuppressive activity, CsA is able to promote regeneration of damaged peripheral nerves. However, the crossing of the drug from plasma to neural tissue is restricted by the relative impermeability of the blood—brain barrier. To know whether CyPB might also participate in the delivery of CsA into the brain, we have analyzed the interactions of CyPB with brain capillary endothelial cells. First, we demonstrated that CyPB binds to two types of binding sites present at the surface of capillary endothelial cells from various species of tissues. The first type of binding sites (KD = 300 nM; number of sites = 3 × 106) is related to interactions with negatively charged compounds such as proteoglycans. The second type of binding sites, ∼50,000 per cell, exhibits a higher affinity for CyPB (KD = 15 nM) and is involved in an endocytosis process, indicating it might correspond to a functional receptor. Finally, the use of an in vitro model of blood—brain barrier allowed us to demonstrate that CyPB is transcytosed by a receptor‐mediated pathway (flux = 16.5 fmol/cm2/h). In these conditions, CyPB did not significantly modify the passage of CsA, indicating that it is unlikely to provide a pathway for CsA brain delivery.

Myeloid cells are tunable by a polyanionic polysaccharide derivative and co-determine host rescue from lethal virus infection

Insight into molecular and cellular mechanisms of innate immunity is critical to understand viral pathogenesis and immunopathology and might be exploited for therapy. Whereas the molecular mechanisms of the IFN defense are well established, cellular mechanisms of antiviral immunity are only emerging, and their pharmacological triggering remains unknown. COAM is a polysaccharide derivative with antiviral activity but without comprehension about its mechanism of action. The COAM mixture was fractionated, and prophylactic treatment of mice with COAM polymers of high MW resulted in a conversion from 100% lethal mengovirus infection to an overall survival rate of 93% without obvious clinical sequelae. Differential and quantitative analysis of peritoneal leukocytes demonstrated that COAM induced a profound influx of neutrophils. Selective cell depletion experiments pointed toward neutrophils and macrophages as key effector cells in the rescue of mice from lethal mengovirus. COAM was able to induce mRNA and protein expression of the mouse neutrophil chemokine GCP‐2. Binding of GCP‐2 to COAM was demonstrated in solution and confirmed by SPR technology. Although COAM was not chemotactic for neutrophils, COAM‐anchored muGCP‐2 retained chemotactic activity for human and mouse neutrophils. In conclusion, this study established that COAM rescued mice from acute and lethal mengovirus infection by recruiting antiviral leukocytes to the site of infection, as proposed through the induction, binding, and concentration of endogenous chemokines. These findings reinforce the role of neutrophils and macrophages as critical cells that can be manipulated toward antiviral defense.

Endothelium in Pathologic Angiogenesis and Angiogenesis-Mediated Therapies

This chapter describes a short historical overview of the progress in endothelium research and point the importance of organ-selective characteristics according to the present knowledge about endothelium biology. Uncovering the advantages that the endothelial cell properties and characteristics provide for the development of future targeted therapies, the review describes why mature endothelial cells due to their organ-specificity can be useful to target diseased organs.