Overexpression of Activated Protein C is Detrimental During Severe Experimental Gram-Negative Sepsis (Melioidosis)*

Kager, Liesbeth M.; Wiersinga, W. Joost; Roelofs, Joris J. T. H.; Boer, Onno J. de; Meijers, Joost C. M.; Isermann, Berend; Veer, Cornelis van’t; Poll, Tom van der

doi:10.1097/ccm.0b013e31828a4316

Cited by 8 publications

(15 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As reported earlier, transgenic APC high mice appear grossly normal, reproduce normally and do not show any signs of spontaneous bleeding [21]. Endogenous overexpression of APC in APC high mice has been confirmed in previous reports [21] as well as in our own laboratory [22]. Per time-point two groups of 8 mice were compared (WT and APC high ).…”

Section: Methodssupporting

confidence: 74%

“…We previously showed that APC high -mice have markedly increased levels of APC in various organs as was measured in plasma, lung-, kidney-, liver-, and spleen homogenates of uninfected APC high -mice [22]. To investigate whether overexpression of APC would impact on bacterial growth, we infected WT and APC high -mice with 5*10 4 CFU of S. pneumoniae and sacrificed them after 6, 24 or 48 hours to determine bacterial loads in lungs (the primary site of infection), blood, liver and spleen homogenates (to evaluate the extent of dissemination) (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…The total histopathology score was expressed as the sum of the scores of the individual parameters, with a maximum of 24. Staining for granulocytes, using fluorescein isothiocyanate-labeled rat-anti-mouse Ly-6G mAb (BD Pharmingen, San Diego, CA) was performed as described previously [22],[23]. All slides were slightly counterstained with methylgreen.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Overexpression of activated protein C hampers bacterial dissemination during pneumococcal pneumonia

et al. 2014

Self Cite

View full text Add to dashboard Cite

BackgroundDuring pneumonia, inflammation and coagulation are activated as part of anti-bacterial host defense. Activated protein C (APC) has anticoagulant and anti-inflammatory properties and until recently was a registered drug for the treatment of severe sepsis. Streptococcus (S.) pneumoniae is the most common causative pathogen in community-acquired pneumonia.MethodsWe aimed to investigate the effect of high APC levels during experimental pneumococcal pneumonia. Wild type (WT) and APC overexpressing (APChigh)-mice were intranasally infected with S. pneumoniae and sacrificed after 6, 24 or 48 hours, or followed in a survival study.ResultsIn comparison to WT mice, APChigh-mice showed decreased bacterial dissemination to liver and spleen, while no differences in bacterial loads were detected at the primary site of infection. Although no differences in the extent of lung histopathology were seen, APChigh-mice showed a significantly decreased recruitment of neutrophils into lung tissue and bronchoalveolar lavage fluid. Activation of coagulation was not altered in APChigh-mice. No differences in survival were observed between WT and APChigh-mice (P =0.06).ConclusionAPC overexpression improves host defense during experimental pneumococcal pneumonia. This knowledge may add to a better understanding of the regulation of the inflammatory and procoagulant responses during severe Gram-positive pneumonia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0559-3) contains supplementary material, which is available to authorized users.

show abstract

Section: Methodssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Overexpression of activated protein C hampers bacterial dissemination during pneumococcal pneumonia

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…In addition, the studies presented in this article focus on aPC generation as a surrogate marker of good things occurring in sepsis, but the effects of histones are likely pleiotropic and observed changes in aPC generation and its correlation with good clinical outcome need further study, as emphasized by recent data showing a negative correlation of outcome and aPC levels in 1 model of sepsis. 18 However, we propose that the described effects of histones and PF4 and heparinoids on aPC generation modeled in Figure 6 also apply to other downstream targets of heparinoids, and we anticipate that neutralization of more downstream targets, especially of histones, would be beneficial overall. We also think that the model in Figure 6 along with the data shown in Figures 5 may explain why heparin has been reported to be of variable use in sepsis, 4 and that concurrent measurements of aPTT and aPC levels in sepsis to titer the effects of heparinoids on outcome may improve clinical outcome.…”

Section: Discussionmentioning

confidence: 98%

“…16,17 As a cautionary note in a recent article using B. pseudomallei to cause melioidosis, mice overexpressing aPC demonstrated enhanced susceptibility to infection. 18 The implications of this observation on enhancing aPC generation in sepsis need further elucidation.…”

mentioning

confidence: 98%

Modulation of Protein C Activation by Histones, Platelet Factor 4, and Heparinoids

Kowalska

Zhao

Zhai

et al. 2014

ATVB

View full text Add to dashboard Cite

Objective-Histones are detrimental in late sepsis. Both activated protein C (aPC) and heparin can reverse their effect.Here, we investigated whether histones can modulate aPC generation in a manner similar to another positively charged molecule, platelet factor 4, and how heparinoids (unfractionated heparin or oxygen-desulfated unfractionated heparin with marked decrease anticoagulant activity) may modulate this effect. Approach and Results-We measured in vitro and in vivo effects of histones, platelet factor 4, and heparinoids on aPC formation, activated partial thromboplastin time, and murine survival. In vitro, histones and platelet factor 4 both affect thrombin/thrombomodulin aPC generation following a bell-shaped curve, with a peak of >5-fold enhancement. Heparinoids shift these curves rightward. Murine aPC generation studies after infusions of histones, platelet factor 4, and heparinoids supported the in vitro data. Importantly, although unfractionated heparin and 2-O, 3-O desulfated heparin both reversed the lethality of high-dose histone infusions, only mice treated with 2-O, 3-O desulfated heparin demonstrated corrected activated partial thromboplastin times and had significant levels of aPC. Conclusions-Our data provide a new contextual model of how histones affect aPC generation, and how heparinoid therapy may be beneficial in sepsis. These studies provide new insights into the complex interactions controlling aPC formation and suggest a novel therapeutic interventional strategy. Kowalska et al Histones, PF4, and Heparinoids and aPC Formation 121range that can be achieved locally at sites of platelet activation. 26 Moreover, other small positive proteins, such as protamine sulfate (PRT), can modulate aPC generation with a similar bell-shaped profile. 24 We have also shown that unfractionated heparin (UFH), which binds PF4 with greater affinity than does CS, effectively reduces available PF4, shifting the aPC generation bell-shaped curve to the right. Thus, added UFH enhances aPC formation at high PF4 concentrations while inhibiting at low PF4 concentrations.24 A similar effect of UFH was seen for the modulation of PRT on aPC.Chromatin has been shown to be released from activated neutrophils by a process called NETosis and can become a source for free histones 27 that, in turn, can worsen the outcome in sepsis in humans. 28 In murine models, infused histones alone can simulate many of the outcomes seen in endotoxemic lethal shock.2 Infused aPC 2 or UFH 29 reverse histoneinduced lethality in mice. Relevant to our studies, histones were shown to inhibit aPC generation in vitro in the presence of TM and IIa. 30 However, because histones are positively charged small proteins, such as PF4 and PRT, we hypothesized that they would modulate aPC generation by IIa complexed to TM CS along a bell-shaped curve, enhancing aPC generation at low concentrations and only inhibiting aPC generation at high concentrations. We reasoned that in severe sepsis, large amounts of both histones and PF4 are released and inhibit ...

show abstract

Melioidosis

Wiersinga

Virk

Torres

et al. 2018

Nat Rev Dis Primers

Self Cite

530

792

View full text Add to dashboard Cite

Burkholderia pseudomallei is a Gram-negative environmental bacterium and the aetiological agent of melioidosis, a life-threatening infection that is estimated to account for ∼89,000 deaths per year worldwide. Diabetes mellitus is a major risk factor for melioidosis, and the global diabetes pandemic could increase the number of fatalities caused by melioidosis. Melioidosis is endemic across tropical areas, especially in southeast Asia and northern Australia. Disease manifestations can range from acute septicaemia to chronic infection, as the facultative intracellular lifestyle and virulence factors of B. pseudomallei promote survival and persistence of the pathogen within a broad range of cells, and the bacteria can manipulate the host's immune responses and signalling pathways to escape surveillance. The majority of patients present with sepsis, but specific clinical presentations and their severity vary depending on the route of bacterial entry (skin penetration, inhalation or ingestion), host immune function and bacterial strain and load. Diagnosis is based on clinical and epidemiological features as well as bacterial culture. Treatment requires long-term intravenous and oral antibiotic courses. Delays in treatment due to difficulties in clinical recognition and laboratory diagnosis often lead to poor outcomes and mortality can exceed 40% in some regions. Research into B. pseudomallei is increasing, owing to the biothreat potential of this pathogen and increasing awareness of the disease and its burden; however, better diagnostic tests are needed to improve early confirmation of diagnosis, which would enable better therapeutic efficacy and survival.

show abstract

Overexpression of Activated Protein C is Detrimental During Severe Experimental Gram-Negative Sepsis (Melioidosis)*

Abstract: Constitutively enhanced expression of activated protein C impairs host defense during severe Gram-negative sepsis caused by B. pseudomallei.

Cited by 8 publications

References 43 publications

Overexpression of activated protein C hampers bacterial dissemination during pneumococcal pneumonia

Overexpression of activated protein C hampers bacterial dissemination during pneumococcal pneumonia

Modulation of Protein C Activation by Histones, Platelet Factor 4, and Heparinoids

Melioidosis

Contact Info

Product

Resources

About