Biomedical subjects

Sjoukje H Slofstra

Publications and source records attributed to Sjoukje H Slofstra.

7 recordsLinked to original sources

PubMed2006

Low dose endotoxin priming is accountable for coagulation abnormalities and organ damage observed in the Shwartzman reaction. A comparison between a single-dose endotoxemia model and a double-hit endotoxin-induced Shwartzman reaction.

The clinical response of sepsis to a systemic inflammatory infection may be complicated by disseminated intravascular coagulation or DIC. In order to experimentally study the syndrome of DIC, we aimed for a severe sepsis model complicated by disseminated coagulation. Most-simplified-experimental models describing coagulation abnormalities as a consequence of sepsis are based on single dose endotoxemia. The so called-Shwartzman reaction contrarily, is elicited by a low dose endotoxin priming followed by an LPS challenge and is characterized by pathological manifestations that represent the syndrome of DIC. In order to investigate whether the Shwartzman reaction is superior to a single endotoxin challenge as a model for sepsis-induced DIC and to determine what the pathological effect is of an encounter of low endotoxin prior to an LPS challenge, we undertook the present study. In this study we demonstrate that low-dose endotoxin priming prior to an LPS challenge in the Shwartzman reaction is accountable for micro-vascular thrombosis in lung and liver and subsequent (multi-) organ failure, not observed after a single-dose endotoxin challenge, which indicates that the Shwartzman reaction is well suited-model to study sepsis-induced DIC adversities. Remarkably, only minor differences in the innate immune response were established between the single-dose endotoxin challenge and the Shwartzman reaction.

Journal Article↗

PubMed2006

Signal transduction induced by activated protein C: no role in protection against sepsis?

The anticoagulant activated protein C (APC) is historically known as a risk factor for venous thrombosis. However, after the positive results of the protein C worldwide evaluation in severe sepsis (PROWESS) trial, which showed that APC was the first drug that considerably reduced sepsis-related mortality, APC is considered a pleiotropic protein with both anticoagulant and anti-inflammatory properties. In addition, in vitro studies have suggested that APC-induced intracellular signal transduction is a potential mechanism by which APC might be protective against sepsis. Recently, however, the efficacy of APC in sepsis has been argued, and also the extent to which the signal transduction capacity of APC contributes to its pro-survival effects is debated. Here, we review the role of APC in the body natural defense against sepsis and discuss the mechanism by which APC might act at a cellular level.

Animals↗

PubMed2005

Low molecular weight heparin attenuates multiple organ failure in a murine model of disseminated intravascular coagulation.

OBJECTIVE: Bacterial sepsis causes widespread vascular inflammation that frequently leads to disseminated intravascular coagulation (DIC). Although intravascular coagulation contributes to organ failure, it is often debated whether anticoagulant therapy produces any beneficial effects in patients with DIC. The aim of this study was to document potential beneficial effects of low molecular weight heparin (LMWH) in a lipopolysaccharide-induced DIC model. DESIGN: Controlled animal experiment combined with an in vitro laboratory study. SETTING: Academic research laboratory. SUBJECTS: C57BL/6 mice subjected to two injections of Serratia Marcescens lipopolysaccharide (LPS) resulting in the generalized Shwartzman's reaction as a model for DIC. INTERVENTIONS: LMWH (5 IU of anti-Xa activity) or saline was administered before both LPS injections and 10 hrs after the first exposure to LPS. To test the effect of LMWH on LPS-driven monocyte inflammatory responses, a human monocyte-human umbilical vein endothelial cell co-culture was used to determine E-selectin expression as a marker of monocyte adherence. MEASUREMENTS AND MAIN RESULTS: In our murine DIC model, LMWH had no effect on markers of inflammation. In addition, no effect of LMWH was detected on monocyte adherence in the human monocyte-human umbilical vein endothelial cell co-culture. Organ damage, contrarily, was significantly reduced as determined by hepatic necrosis (p < .05), lung epithelial protein leakage (p < .05), and creatinine release from kidneys into plasma (p < .01). LMWH protection from organ failure resulted in an increase in survival (p = .06) in this model for DIC. CONCLUSIONS: These results demonstrate the significance of blood coagulation in the progression of DIC and hint at a beneficial role for LMWH anticoagulation in the management of DIC.

Animals↗

PubMed2004

FVIIa:TF induces cell survival via G12/G13-dependent Jak/STAT activation and BclXL production.

Tissue factor (TF), apart from activating the extrinsic pathway of the blood coagulation, is a principal regulator of embryonic and oncogenic angiogenesis, inflammation, leukocyte reverse transmigration, and tumor progression. It has become clear that these events are mediated by intracellular signal transduction elicited by TF/factor VIIa (FVIIa) interaction, but the details of this signaling remain largely obscure. In this study, we show that FVIIa/TF-interaction produces STAT5 phosphorylation, STAT5 nuclear translocation and transactivation of a STAT5 reporter construct. FVIIa-dependent STAT5 activation was dependent on FVIIa proteolytic activity but not on generation of the downstream coagulation factors Xa and thrombin, nor on the TF cytoplasmic domain. FVIIa-induced STAT5 phosphorylation was dependent on functional G12/G13 class G proteins and Jak2 activity, but not Jak1 or Tyk2. Finally, we show that FVIIa leads to cell survival through a Jak2/STAT5-dependent production of the antiapoptotic STAT5 target Bcl(XL) as well as Jak2-dependent activation of the antiapoptotic protein PKB. In conclusion, our results show that FVIIa induces cell survival through STAT5-dependent Bcl(XL) production and Jak2-dependent activation of PKB. Finally, we demonstrated for the first time that TF/FVIIa-signal transduction is dependent on G12/G13 class G proteins.

Active Transport, Cell Nucleus↗

PubMed2003

Disseminated intravascular coagulation.

Disseminated Intravascular Coagulation (DIC) is an acquired syndrome representing a hypercoagulable state, haemorrhagic symptoms and multiple organ failure. The clinical relevance of this syndrome is complicated since there is no established way of diagnosing DIC and it is difficult to distinguish whether clinical features are attributable to the underlying disease or DIC. Experimental studies, based on models of gram-negative sepsis and the Generalized Shwartzman Reaction, show that DIC is characterized by strongly enhanced inflammatory activity, activated coagulation and impaired fibrinolysis. In this review we propose that activated neutrophils play a pivotal role in the pathophysiology of DIC, particularly by contributing to inflammation and vascular injury. Additionally, a distinct role for granulocytes in fibrinolysis has also been suggested. Although the underlying procoagulant pathways of DIC and the important role of tissue factor have been unravelled, therapeutic interventions counteracting the mediators of these pathways proved mainly unsuccessful (with the positive exception of activated protein C). Dissecting the molecular interactions at the onset and progression of DIC might therefore help to elucidate the fundamental consequences of DIC, possibly contributing to better diagnostic tools and more effective therapeutic options.

Blood Coagulation↗

PubMed2003

Trehalose and glycogen accumulation is related to the duration of the G1 phase of Saccharomyces cerevisiae.

Several factors may control trehalose and glycogen synthesis, like the glucose flux, the growth rate, the intracellular glucose-6-phosphate level and the glucose concentration in the medium. Here, the possible relation of these putative inducers to reserve carbohydrate accumulation was studied under well-defined growth conditions in nitrogen-limited continuous cultures. We showed that the amounts of accumulated trehalose and glycogen were regulated by the growth rate imposed on the culture, whereas other implicated inducers did not exhibit a correlation with reserve carbohydrate accumulation. Trehalose accumulation was induced at a dilution rate (D)</=0.10 h(-1), whereas glycogen accumulation gradually increased at decreasing growth rates. The growth rate dependency of trehalose accumulation was supported by studies in cells overexpressing the G(1)-cyclin CLN3. The trehalose level appeared to be dependent on the duration of the G(1) phase, as trehalose was only accumulated at a G(1) phase duration of more than 5 h in both wild-type and CLN3-overexpressing cells. On the other hand, the glycogen level was reduced by CLN3 overexpression in a cell cycle-independent manner. A possible regulatory mechanism that links trehalose and glycogen accumulation to the growth rate is discussed.

Carbon↗

PubMed2002

VIIa/tissue factor interaction results in a tissue factor cytoplasmic domain-independent activation of protein synthesis, p70, and p90 S6 kinase phosphorylation.

FVIIa binding to tissue factor (TF) and subsequent signal transduction have now been implicated in a variety of pathophysiological processes, including cytokine production during sepsis, tumor angiogenesis and neoangiogenesis, and leukocyte diapedesis. The molecular details, however, by which FVIIa/TF affects gene expression and cellular physiology, remain obscure. Here we show that FVIIa induces a transient phosphorylation of p70/p85(S6K) and p90(RSK) in BHK cells stably transfected with either full-length TF or with a cytoplasmic domain-truncated TF but not in wild type BHK cells. Phosphorylation of these kinases was also observed in HaCaT cells, expressing endogenous TF. Phosphorylation of p70/p85(S6K) coincided with protein kinase B and GSK-3beta phosphorylation. Activation of p70/p85(S6K) was sensitive to inhibitors of phosphatidylinositol 3-kinase and to rapamycin, whereas phosphorylation of p90(RSK) was sensitive to PD98059. FVIIa stimulation of p70/p85(S6K) and p90(RSK) correlated with phosphorylation of the eukaryotic initiation factor eIF-4E, up-regulation of protein levels of eEF1alpha and eEF2, and enhanced [(35)S]methionine incorporation. These effects were not influenced by inhibitors of thrombin or FXa generation and were strictly dependent on the presence of the extracellular domain of TF, but they did not require the intracellular portion of TF. We propose that a TF cytoplasmic domain-independent stimulation of protein synthesis via activation of S6 kinase contributes to FVIIa effects in pathophysiology.

Animals↗