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Platelet TLR‐4 activation by pathogen‐ or damage‐associated molecular pattern molecules triggers pro‐thrombotic, proinflammatory, and pro‐coagulant effector responses. Moreover, platelet TLR4 has a prominent role as a sensor of high lipopolysaccharide circulating levels during sepsis and in the clearance of pathogens mediated by neutrophils. This review presents evidence pointing to TLR4 as a bridge connecting thrombosis and innate immunity. [ABSTRACT FROM AUTHOR]

Under normal conditions, platelets do not interact with blood vessel walls; however, upon activation, platelets firmly attach to endothelial cells. Communication between platelets and endothelial cells during the normal or activated state takes place at multiple levels. Cross-talk may occur over a distance via transient interactions or through receptor-mediated cell–cell adhesion. Platelets may release or transfer substances that affect endothelial cell function and vice versa. Excessive dialogue between platelets and the endothelium exists in several disease states as a causative factor and/or as a consequence of the disease process. Glycans are covalent assemblies of sugars that exist in either free form or in covalent complexes with proteins or lipids. Among other functions, glycans confer stability to the proteins to which they are attached, play key roles in signal transduction and control cell development and differentiation. Glycans not only influence the structure and function of hemostatic molecules but are also increasingly recognized as key molecules regulating platelet-endothelial interactions. The present review outlines the current knowledge regarding glycan-mediated interactions between platelets and endothelial cells and their role in physiopathological processes. [ABSTRACT FROM AUTHOR]

Galectins (Gals), a family of mammalian lectins, play diverse roles under physiological and pathological conditions. Here, we analyzed the tandem-repeat Gal-8 synthesis, secretion and effects on the endothelium physiology. Gal-8M and Gal-8L isoforms were secreted under basal conditions by human microvascular endothelial cells (HMEC-1). However, expression and secretion of the Gal-8M isoform, but not Gal-8L, were increased in response to bacterial lipopolysaccharide (LPS) stimulus and returned to control values after LPS removal. Similarly, cell surface Gal-8 exposure was increased after stimulation with LPS. To evaluate Gal-8 effects on the endothelium physiology, HMEC-1 cells were incubated in the presence of recombinant Gal-8M. Pretreated HMEC-1 cells became proadhesive to human normal platelets, indicating that Gal-8 actually activates endothelial cells. This effect was specific for lectin activity as it was prevented by the simultaneous addition of lactose, but not by sucrose. Endothelial cells also increased their exposition of von Willebrand factor after Gal-8 treatment, which constitutes another feature of cell activation that could be, in turn, responsible for the observed platelet adhesion. Several pro-inflammatory molecules were abundantly produced by Gal-8 stimulated endothelial cells: CXCL1 (GRO-α), GM-CSF, IL-6 and CCL5 (RANTES), and in a lower degree CCL2 (MCP-1), CXCL3 (GRO-γ) and CXCL8 (IL-8). In agreement, Gal-8M induced nuclear factor kappa B phosphorylation. Altogether, these results not only confirm the pro-inflammatory role we have already proposed for Gal-8 in other cellular systems but also suggest that this lectin is orchestrating the interaction between leukocytes, platelets and endothelial cells. [ABSTRACT FROM AUTHOR]

It has been reported previously that activation of vascular endothelium by outer membrane proteins of the spirochetes Borrelia sp. and Treponema sp. resulted in enhanced expression of endothelial cell adhesion molecules. To investigate the role of leptospiral proteins in this process, a predicted lipoprotein encoded by the gene LIC10365 was selected, which belongs to a paralogous family that presents a domain of unknown function, DUF1565. The LIC10365 gene was cloned and the protein expressed in Escherichia coli C43 (DE3) strain using the vector pAE. The recombinant protein tagged with N-terminal hexahistidine was purified by metal-charged chromatography and was used to assess its ability to activate cultured human umbilical vein endothelial cells. The rLIC10365 activated endothelium in such a manner that E-selectin and intercellular adhesion molecule 1 (ICAM-1) became upregulated in a dose-dependent fashion. The LIC10365-encoded protein was identified in vivo in the renal tubules of animal during experimental infection with Leptospira interrogans. Collectively, these results implicate the LIC10365-coding protein of L. interrogans as a potential effector molecule in the promotion of a host inflammatory response. This is the first report of a leptospiral protein capable of up-regulating the expression of endothelial cell adhesion molecules ICAM-1 and E-selectin. [ABSTRACT FROM AUTHOR]