The infection of microvascular endothelial cells with ExoU-producing Pseudomonas aeruginosa triggers the release of von Willebrand factor and platelet adhesion

An increased plasma concentration of von Willebrand factor (vWF) is detected in individuals with many infectious diseases and is accepted as a marker of endothelium activation and prothrombotic condition. To determine whether ExoU, a Pseudomonas aeruginosa cytotoxin with proinflammatory activity, enhances the release of vWF, microvascular endothelial cells were infected with the ExoU-producing PA103 P. aeruginosa strain or an exoU-deficient mutant. Significantly increased vWF concentrations were detected in conditioned medium and subendothelial extracellular matrix from cultures infected with the wild-type bacteria, as determined by enzyme-linked immunoassays. PA103-infected cells also released higher concentrations of procoagulant microparticles containing increased amounts of membrane-associated vWF, as determined by flow cytometric analyses of cell culture supernatants. Both flow cytometry and confocal microscopy showed that increased amounts of vWF were associated with cytoplasmic membranes from cells infected with the ExoU-producing bacteria. PA103-infected cultures exposed to platelet suspensions exhibited increased percentages of cells with platelet adhesion. Because no modulation of the vWF mRNA levels was detected by reverse transcription-polymerase chain reaction assays in PA103-infected cells, ExoU is likely to have induced the release of vWF from cytoplasmic stores rather than vWF gene transcription. Such release is likely to modify the thromboresistance of microvascular endothelial cells.

Transmigração endotelial do fungo patogênico Sporothrix schenckii: modulação da via de p38MAPK/MLCK, Src e de moléculas de adesão celular / Endothelial transmigration of the pathogenic fungus, Sporothrix schenckii: pathway modulation of p38MAPK/MLCK, Src and cell adhesion molecules

Sporothrix schenckii é um fungo dimórfico, agente etiológico da esporotricose, uma micose subaguda ou crônica que pode eventualmente evoluir para complicações sistêmicas, principalmente em pacientes imunocomprometidos. O endotélio exerce um papel crucial durante infecções disseminadas já que, juntamente com as células epiteliais, representa uma barreira a ser ultrapassada por microorganismos invasores. Em estudos anteriores, observamos que S. schenckii transmigra preferencialmente pela rota paracelular (passagem entre células endoteliais adjacentes), interagindo em seguida com componenetes da matriz subendotelial. Também foram identificadas algumas vias de sinalização relacionadas à diferentes fases da interação de leveduras de S. schenckii com o endotélio in vitro (associação/endocitose, transmigração). No entanto, a correlação entre tais vias de sinalização e os mecanismos celulares da invasão do endotélio pelo fungo não foram efetivamente demonstrados. No presente trabalho, a análise do perfil de proteínas endoteliais totais fosforiladas em resíduos de tirosina mostrou que S. schenckii induz fosforilações em tempos curtos (< 15 minutos), em proteínas de massas moleculares 20, 13, 12 e 6KDa, enquanto alunas proteínas de mais alto peso molecular (83, 123, 136, 140 e 193 KDa) persistem fosforiladas em tempos mais longos durante a infecção (6 horas). As vias de transdução de sinais disparadas pela interação do fungo com o endotélio foram investigadas através do uso de inibidores da ativação de MAPKs p38 (SB 203580) e ERK (PD 98059), MLCK (W7) e de um quelante de Ca2+ intracelular (BAPTA). A transmigração de S. schenckii através de monocamadas de HUVECs por 6 horas mostrou ser dependente da ativação de ERK e p38, ions Ca2+ intracelular e MLCK. Estas vias estão também envolvidas nos rearranjos do citoesqueleto de actina que levam à contratilidade celular e aumento da permeabilidade endotelial. A interação do fungo com HUVECs induziu ativação de Src...

Sporothrix schenckii, a dimorphic fungus, is the causative agent of sporotrichosis, a cutaneous/subcutaneous mycosis which can eventually evolve to systemic complications, mainly in immunocompromised patients. The primary interaction of pathogenic fungi with endothelial cells (EC) is throught to be essential for the development of systemic infections. We have previously shown that S. schenckii cross endothelial monolayers through a paracellular pathway, in a process also modulated by the subendothelial matrix, and that the fungus is able to alter host signaling pathways. We observed that the interaction of S. schenckii with human umbilical vein endothelial cells (HUVECs) was regulated by tyrosine-phosphorylation of EC proteins. In the present work, we observed that S. schenckii stimulates the early increase (<15 minutes) in tyrosine-phorphorylation of 20, 13, 12 e 6 KDa endothelial proteins, whereas tyrosine-phosphorylation of higher molecular weight proteins (83, 123, 136, 140 e 193 KDa) persists up to 6 hours of endothelial infection. Selective signal transduction inhibitors (SB203580 and W7, for blocking p38 MAPK and MLCK activation, respectively) were able to inhibit transendothelial migration of S. schenckii. The process was also modulated by Ca++ions. These signaling pathways are crucial for the actin rearrangement associated to impairment of endothelial permeability. Long-term (3 hours) interaction of S. schenckii with HUVECs lead to increase of MLC2 phosphorylation and Src activation. Src was shown by others to be involved in the phosphorylation of VE-cadherin, thus provoking adherent junctions (AJs) disassembly. We found that S. schenckii induces tyrosine-phosphorylation of endothelial VE-cadherin up to 3 hours of interaction with endothelial cells. VE-cadherin phosphorylation can be triggered by the activation of E-selectin in endothelial cells. Since the time-course of the major signaling events correlated with the time needed...

Cultivos primarios de células endoteliales aisladas de cordón umbilical humano: un modelo biológico para el estudio de los mecanismos de infección por enterococos / Primary cultures of human umbilical chord vein endothelial cells: a biological model for studying enterococcal infection mechanisms

Aunque las especies de enterococos son flora normal del tracto gastrointestinal humano, se encuentran entre los tres agentes patógenos microbianos que más se asocian con infecciones intrahospitalarias. Tradicionalmente, los enterococos se han considerado bacterias extracelulares. Sin embargo, es creciente la información que reporta su ingreso a través de líneas celulares epiteliales o macrófagos. A pesar de que estos microorganismos constituyen el tercer grupo de aislamientos obtenido de pacientes con bacteriemia o endocarditis, su interacción con la célula endotelial no se ha descrito completamente. En el presente trabajo evaluamos si el aislamiento intrahospitalario de Enterococcus faecalis (Ef2880) podía penetrar en células endoteliales de la vena de cordón umbilical humano (HUVEC) cultivadas in vitro. Nuestros resultados indican que los cultivos primarios HUVEC después de ser inoculados con Ef2890, incubados y tratados con antibióticos bactericidas para las bacterias extracelulares y adheridas a la cara externa de la membrana celular, exhiben bacterias intracelulares que pueden ser recuperadas vivas cuatro horas después de la inoculación. El modelo biológico desarrollado se puede constituir en una herramienta útil para el estudio de las interacciones que establecen los enterococos con el endotelio