Sepsis is a systemic inflammatory syndrome induced by bacterial infection that can lead to multiorgan failure. Endothelial surface glycocalyx (ESG) decorating the inner wall of blood vessels is a regulator of multiple vascular functions. Here, we tested a hypothesis that patchy degradation of ESG occurs early in sepsis and is a result of exocytosis of Lysosome-related organelles. Time-lapse video microscopy revealed that exocytosis of Weibel-Palade bodies and secretory lysosomes occurred a few minutes after application of lipopolysaccharides to endothelial cells. Two therapeutic maneuvers, a nitric oxide intermediate, NG-hydroxy-L-arginine, and culture media conditioned by endothelial progenitor cells reduced the motility of Lysosome-related organelles. Confocal and stochastic optical reconstruction microscopy confirmed the patchy loss of ESG simultaneously with the exocytosis of Lysosome-related organelles and Weibel-Palade bodies in cultured endothelial cells and mouse aorta. The Loss of ESG was blunted by pretreatment with NG-hydroxy-L-arginine or culture media conditioned by endothelial progenitor cells. Moreover, these treatments resulted in a significant reduction in deaths of septic mice. Our data support the hypothesis assigning to stress-induced exocytosis of these organelles the role of a hair-trigger for Local degradation of ESG that initiates leukocyte infiltration, increase in vascular permeability, and partially accounts for the later rates of morbidity and mortality.
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