Endothelial activation leading to vascular barrier breakdown plays an essential role in the pathophysiology of multiple-organ dysfunction syndrome (MODS) in sepsis. Increasing evidence suggests that the function of the vessel-protective factor Angiopoietin-1 (Ang-1), a ligand of the endothelial-specific Tie2 receptor, is inhibited by its antagonist Angiopoietin-2 (Ang-2) during sepsis. In order to reverse the effects of the sepsis-induced suppression of Ang-1 and elevation of Ang-2 we aimed to investigate whether an intravenous injection of recombinant human (rh) Ang-1 protects against MODS in murine sepsis.
Polymicrobiological abdominal sepsis was induced by cecal ligation and puncture (CLP). Mice were treated with either 1 μg of intravenous rhAng-1 or control buffer immediately after CLP induction and every 8h thereafter. Sham-operated animals served as time-matched controls.
Compared to buffer-treated controls, rhAng-1 treated septic mice showed significant improvements in several hematologic and biochemical indicators of MODS. Moreover, rhAng-1 stabilized endothelial barrier function, as evidenced by inhibition of protein leakage from lung capillaries into the alveolar compartment. Histological analysis revealed that rhAng-1 treatment attenuated leukocyte infiltration in lungs and kidneys of septic mice, probably due to reduced endothelial adhesion molecule expression in rhAng-1 treated mice. Finally, the protective effects of rhAng-1 treatment were reflected by an improved survival time in a lethal CLP model.
In a clinically relevant murine sepsis model, intravenous rhAng-1 treatment alone is sufficient to significantly improve a variety of sepsis-associated organ dysfunctions and survival time, most likely by preserving endothelial barrier function. Further studies are needed to pave the road for clinical application of this therapy concept.
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"Mice were intraperitoneally injected with 100 μg of a purified, functional grade anti-mouse TNF-α antibody (Ab) (clone MP6-XT3; eBioscience), with 500 μg of anti-mouse IL-6 Ab (MP5-20F3; BioXcell), or with 100 μg of an isotype control Ab (clone P22.214.171.124.1; eBioscience) on Days 1, 2, and 4 p.i. Mice were monitored daily until Day 30 p.i. For treatment with Ang-1, mice were intraperitoneally injected with 1μg of rhAng-1 (R&D Systems)(dissolved in 100 μL phosphate-buffered saline per injection) or the same volume of control buffer (100 μL phosphate-buffered saline per injection) . "
[Show abstract][Hide abstract]ABSTRACT: Severe dengue is caused by host responses to viral infection, but the pathogenesis remains unknown. This is, in part, due to the lack of suitable animal models. Here, we report a non-mouse-adapted low-passage DENV-3 clinical isolate, DV3P12/08, derived from recently infected patients. DV3P12/08 caused a lethal systemic infection in type I and II IFN receptor KO mice (IFN-α/β/γR KO mice), which have the C57/BL6 background. Infection with DV3P12/08 induced a cytokine storm, resulting in severe vascular leakage (mainly in the liver, kidney and intestine) and organ damage, leading to extensive hemorrhage and rapid death. DV3P12/08 infection triggered the release of large amounts of TNF-α, IL-6, and MCP-1. Treatment with a neutralizing anti-TNF-α antibody (Ab) extended survival and reduced liver damage without affecting virus production. Anti-IL-6 neutralizing Ab partly prolonged mouse survival. The anti-TNF-α Ab suppressed IL-6, MCP-1, and IFN-γ levels, suggesting that the severe response to infection was triggered by TNF-α. High levels of TNF-α mRNA were expressed in the liver and kidneys, but not in the small intestine, of infected mice. Conversely, high levels of IL-6 mRNA were expressed in the intestine. Importantly, treatment with Angiopoietin-1, which is known to stabilize blood vessels, prolonged the survival of DV3P12/08-infected mice. Taken together, the results suggest that an increased level of TNF-α together with concomitant upregulation of Tie2/Angiopoietin signaling have critical roles in severe dengue infection.
"Ang-1 takes part in maintaining endothelial integrity and inhibiting inflammation while Ang-2 promotes endothelial leak. Furthermore, treatments targeted in animal models of sepsis to block angio- poietin-2, or enhance angiopoietin-1 have been shown to be protective [29,464748. We and others have shown in smaller studies that the Ang-1/Ang-2 axis is implicated in sepsis pathogenesis and associated with poor outcomes [23,25,49]. "
[Show abstract][Hide abstract]ABSTRACT: Background:
Endothelial activation plays a role in organ dysfunction in the systemic inflammatory response syndrome (SIRS). Angiopoietin-1 (Ang-1) promotes vascular quiescence while angiopoietin-2 (Ang-2) mediates microvascular leak. Circulating levels of Ang-1 and Ang-2 in patients with SIRS could provide insight on risks for organ dysfunction and death distinct from inflammatory proteins. In this study, we determined if biomarkers of endothelial activation and inflammation exhibit independent associations with poor outcomes in SIRS.
We studied 943 critically ill patients with SIRS admitted to an Intensive Care Unit (ICU) of an academic medical center. We measured plasma levels of endothelial markers (Ang-1, Ang-2, soluble vascular cell adhesion molecule-1 (sVCAM-1)) and inflammatory markers (interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte-colony stimulating factor (G-CSF), soluble tumor necrosis factor receptor-1 (sTNFR-1)) within 24 hours of enrollment. We tested for associations between each marker and 28 day mortality, shock, and day 3 sequential organ failure assessment (SOFA) score. For 28 day mortality, we performed sensitivity analysis for those subjects with sepsis and those with sterile inflammation. We used multivariate models to adjust for clinical covariates and determine if associations identified with endothelial activation markers were independent of those observed with inflammatory markers.
Higher levels of all biomarkers were associated with increased 28 day mortality except levels of Ang-1 which were associated with lower mortality. After adjustment for comorbidities and sTNFR-1 concentration, a doubling of Ang-1 concentration was associated with lower 28 day mortality (Odds ratio (OR) = 0.81; p<0.01), shock (OR = 0.82; p<0.001), and SOFA score (β = -0.50; p<0.001), while Ang-2 concentration was associated with increased mortality (OR = 1.55; p<0.001), shock (OR = 1.51; p<0.001), and SOFA score (β = +0.63; p<0.001). sVCAM-1 was not independently associated with SIRS outcomes.
In critically ill patients with SIRS, early measurements of Ang-1 and Ang-2 are associated with death and organ dysfunction independently of simultaneously-measured markers of inflammation.
"It is anticipated that novel pre-analytical approaches and further advancement in epigenetic platforms as well as single-cell analysis will enable transcriptional and epigenetic studies of genes whose expression is not as markedly altered in whole tissue samples. Sepsis-induced reductions of angiogenic protein levels have previously been reported in the lung [46, 48, 49], kidney [50, 51], and liver  . Similar observations were made for sepsis downregulation of Kdr protein in the lung [45, 52]. "
[Show abstract][Hide abstract]ABSTRACT: The Tie-2/angiopoietin (Tie-2/Ang) and vascular endothelial growth factor receptor-ligand systems (VEGFR/VEGF) are recognized to play important roles in the regulation of microvascular endothelial function. Downregulation of these genes during sepsis has been implicated in the pathogenesis of sepsis-related microvascular leak and multiple organ dysfunction syndrome (MODS). Mechanisms responsible for dysregulation of angiogenic genes in sepsis are poorly defined.
Western blot, RT PCR and multiplex chromatin immunoprecipitation platform (Matrix ChIP) were used to investigate serum albumin leak, changes in gene expression and associated epigenetic alterations in a murine model of acute lung injury-induced sepsis (ALI-sepsis).
Experimental ALI-sepsis induced microvascular leak and downregulation of expression of Angpt1 (Ang1), Tek (Tie-2) and Kdr (Vegfr2 or Flk-1) genes in lung, kidney and liver. These changes correlate with a decrease in RNA polymerase II (Pol II) density at these genes, with the greatest response observed in the lung. ALI-sepsis reduced levels of transcription-permissive histone H3 lysine acetylation (H3KAc) at these loci in all examined tissues. Decreases in permissive H3K4m3 and H3Km2 marks were detected only in lung. In contrast, only minimal alterations in transcription-repressive histone modifications (H3K27m3, H3K9m2, H3K9m3 and H4K20m3) were observed in all tissues.
Our results demonstrate that decreases in transcription-permissive, but not increases in transcription-repressive, histone modifications at Angpt1, Tek and Kdr is a systemic, rather than a lung-restricted response, involving key end-organs in experimental ALI-sepsis. Given that ventilator-associated pneumonia is a major cause of sepsis in critically ill patients, elucidation of mechanisms mediating epigenetic alterations during sepsis provides fundamental new insights into the pathogenesis of sepsis-induced microvascular leak and subsequent end-organ injury/dysfunction.
Full-text · Article · May 2015 · Critical care (London, England)