Activated protein C improves pial microcirculation in experimental endotoxemia in rats

Abstract

IntroductionThe brain is one of the first organs affected clinically in sepsis. Microcirculatory alterations are suggested to be a critical component in the pathophysiology of sepsis. The aim of this study was to investigate the effects of recombinant human activated protein C (rhAPC) on the pial microcirculation in experimental endotoxemia using intravital microscopy. Our hypothesis is rhAPC protects pial microcirculation in endotoxemia. MethodsEndotoxemia was generated in Lewis rats with intravenous injection of lipopolysaccharide (LPS, 5mg/kg i.v.). Dura mater was removed through a cranial window to expose pial vessels on the brain surface. The microcirculation, including leukocyte–endothelial interaction, functional capillary density (FCD) and plasma extravasation of pial vessels was examined by fluorescent intravital microscopy (IVM) 2h after administration of LPS, LPS and rhAPC or equivalent amount of saline (used as Control group). Plasma cytokine levels of interleukin 1 alpha (IL1-α), tumor necrosis factor-α (TNF-α), interferon γ (IFN-γ), Monocyte chemotactic protein-1 (MCP-1) and Granulocyte-macrophage colony-stimulating factor (GM-CSF) were evaluated after IVM. ResultsLPS challenge significantly increased leukocyte adhesion (773±190 vs. 592±152n/mm2 Control), decreased FCD (218±54 vs. 418±74cm/cm2 Control) and increased proinflammatory cytokine levels (IL-1α: 5032±1502 vs. 8±21pg/ml; TNF-α: 1823±1007 vs. 168±228pg/ml; IFN-γ: 785±434 vs. 0pg/ml; GM-CSF: 54±52 vs. 1±3pg/ml) compared to control animals. rhAPC treatment significantly reduced leukocyte adhesion (599±111n/mm2), increased FCD (516±118cm/cm2) and reduced IL-1α levels (2134±937pg/ml) in the endotoxemic rats. ConclusionAPC treatment significantly improves pial microcirculation by reducing leukocyte adhesion and increasing FCD.