Vascular endothelial growth factor is an important determinant of sepsis morbidity and mortality

Tissue-engineered model for real-time monitoring of liver inflammation

Tissue-engineered in vitro models have the potential to be used for investigating inflammation in the complex microenvironment found in vivo. We have developed an in vitro model of hepatic tissue that facilitates real-time monitoring of endothelium activation in liver tissue. This was achieved by creating a layered coculture model in which hepatocytes were embedded in collagen gel and a reporter clone of endothelial cells, which synthesizes green fluorescent protein in response to nuclear factor-kappa B (NF-κB) activation, was overlaid on top of the gel. The efficacy of our approach was established by monitoring in real time the dynamics of NF-κB-regulated fluorescence in response to tumor necrosis factor α. Our studies revealed that endothelial cells in coculture with hepatocytes exhibited a similar NF-κB-mediated fluorescence to both pulse and step stimulation of lipopolysaccharide. By contrast, endothelial cells in monoculture displayed enhanced NF-κB-regulated fluorescence to step in comparison to pulse lipopolysaccharide stimulation. The NF-κB-mediated fluorescence correlated with endothelial cell expression of NF-κB-regulated genes such as intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and E-Selectin, as well as with leukocyte adhesion. These findings suggest that our model provides a powerful platform for investigating hepatic endothelium activation in real time.

NF-κB and STAT3 signaling hubs for lung innate immunity

Innate immune responses to lung pathogens involve the coordinated expression of myriad affector and effector molecules of innate immunity, which must be induced and appropriately regulated in response to diverse stimuli generated by microbes or the infected host. Many intercellular and intracellular signaling pathways are involved, but we propose NF-κB and STAT3 transcription factors to be especially important signaling hubs for integrating these pathways to orchestrate effective host defense without excessive inflammatory injury.

Anti-inflammatory effects of C1-Inhibitor in porcine and human whole blood are independent of its protease inhibition activity

C1-Inhibitor (C1-INH) is an important biological inhibitor, regulating several protein cascade systems. Recent research has shown that the molecule exhibits properties not dependent on its protease inhibition activity. Serum and whole blood from pigs and humans were pre-incubated with C1-INH, iC1-INH or the complement inhibitors SPICE or compstatin. Whole, live Escherichia coli were then added for further incubation. Complement activation, a range of cytokines, chemokines and growth factors, as well as the leukocyte activation markers wCD11R3 (pig) and CD11b (human) were measured. Both C1-INH and iC1-INH dose-dependently and significantly (P<0.05) reduced a range of E. coli-induced pro-inflammatory cytokines and chemokines in porcine and human whole blood, as well as growth factors in human whole blood. Differences between the two forms of C1-INH and between the two species were modest. Most of these anti-inflammatory effects could not be explained by complement inhibition, as specific complement inhibitors had minor effect on several of the mediators. C1-Inhibitor had no inhibitory effect on E. coli-induced complement activation, while iC1-INH enhanced complement activation. The presented data indicate that C1-INH has broad anti-inflammatory effects in E. coli-induced inflammation in pig and human whole blood. These effects are largely independent of the protease inhibition activity.

Evidence in support of a role for anti-angiogenic factors in preterm prelabor rupture of membranes

OBJECTIVE

Vaginal bleeding, placental abruption, and defective placentation are frequently observed in patients with preterm prelabor rupture of membranes (PROM). Recently, a role of vascular endothelial growth factor (VEGF) and its receptor, VEGF receptor (VEGFR)- 1 has been implicated in the mechanisms of membrane rupture. The purpose of this study was to determine whether the soluble form of VEGFR-1 and -2 concentrations in amniotic fluid (AF) change with preterm PROM, intra-amniotic infection/inflammation (IAI), or parturition.

STUDY DESIGN

This cross-sectional study included 544 patients in the following groups: (1) midtrimester (MT) (n = 48); (2) preterm labor (PTL) leading to term delivery (n = 143); (3) PTL resulting in preterm delivery with (n = 72) and without IAI (n = 100); (4) preterm PROM with (n = 46) and without IAI (n = 42); (5) term in labor (n = 48); and (6) term not in labor (n = 45). The concentrations of sVEGFR-1 and sVEGFR-2 were determined by ELISA. Non-parametric statistics and logistic regression analysis were applied.

RESULTS

(1) Preterm PROM (with and without IAI) had a lower median AF concentration of sVEGFR-1 than patients with PTL who delivered at term (p < 0.001 for each comparison); (2) A decrease in AFsVEGFR-1 concentrations per each quartile was associated with PROM after adjusting for confounders (OR 1.8; 95%CI 1.4-2.3); (3) IAI, regardless of the membrane status, was not associated with a change in the median AF concentrations of sVEGFR-1 and sVEGFR-2 (p > 0.05 for each comparison); and (4) Spontaneous term and PTL did not change the median sVEGFR-1 and sVEGFR-2 concentrations (p > 0.05 for each comparison).

CONCLUSION

(1) This is the first evidence that preterm PROM is associated with a lower AF concentration of sVEGFR-1 than patients with PTL intact membranes. These findings cannot be attributed to gestational age, labor, or IAI; and (2) AF concentrations of sVEGFR-2 did not change with preterm PROM, IAI, or labor at term and preterm.

Activation of hypoxia inducible factor 1 is a general phenomenon in infections with human pathogens

Background

Hypoxia inducible factor (HIF)-1 is the key transcriptional factor involved in the adaptation process of cells and organisms to hypoxia. Recent findings suggest that HIF-1 plays also a crucial role in inflammatory and infectious diseases.

Methodology/Principal Findings

Using patient skin biopsies, cell culture and murine infection models, HIF-1 activation was determined by immunohistochemistry, immunoblotting and reporter gene assays and was linked to cellular oxygen consumption. The course of a S. aureus peritonitis was determined upon pharmacological HIF-1 inhibition. Activation of HIF-1 was detectable (i) in all ex vivo in biopsies of patients suffering from skin infections, (ii) in vitro using cell culture infection models and (iii) in vivo using murine intravenous and peritoneal S. aureus infection models. HIF-1 activation by human pathogens was induced by oxygen-dependent mechanisms. Small colony variants (SCVs) of S. aureus known to cause chronic infections did not result in cellular hypoxia nor in HIF-1 activation. Pharmaceutical inhibition of HIF-1 activation resulted in increased survival rates of mice suffering from a S. aureus peritonitis.

Conclusions/Significance

Activation of HIF-1 is a general phenomenon in infections with human pathogenic bacteria, viruses, fungi and protozoa. HIF-1-regulated pathways might be an attractive target to modulate the course of life-threatening infections.

Leptin exacerbates sepsis-mediated morbidity and mortality

The adipose-derived hormone leptin is well known for its contribution to energy metabolism and satiety signaling in the hypothalamus. Previous studies suggested that obesity is an independent risk factor for sepsis morbidity and mortality, and it is associated with elevated baseline levels of circulating leptin in normal, nonseptic patients. In mouse endotoxemia and cecal ligation puncture models of sepsis, we observed elevated levels of leptin and soluble leptin receptor (sLR). Exogenously administered leptin increased mortality in endotoxemia and cecal ligation puncture models and was associated with increased expression of adhesion and coagulation molecules, macrophage infiltration into the liver and kidney, and endothelial barrier dysfunction. Conversely, longform leptin receptor-deficient mice were protected from sepsis morbidity and mortality and had less endothelial dysfunction. Furthermore, an in vitro study revealed that leptin-induced endothelial dysfunction is likely mediated, at least in part, by monocytes. Moreover, administration of an sLR conferred a survival benefit. Human septic patients have increased circulating sLR concentrations, which were correlated with disease severity indices. Together, these data support a pathogenic role for leptin signaling during sepsis.

Imbalances in serum angiopoietin concentrations are early predictors of septic shock development in patients with post chemotherapy febrile neutropenia

BACKGROUND

Febrile neutropenia carries a high risk of sepsis complications, and the identification of biomarkers capable to identify high risk patients is a great challenge. Angiopoietins (Ang -) are cytokines involved in the control microvascular permeability. It is accepted that Ang-1 expression maintains endothelial barrier integrity, and that Ang-2 acts as an antagonizing cytokine with barrier-disrupting functions in inflammatory situations. Ang-2 levels have been recently correlated with sepsis mortality in intensive care units.

METHODS

We prospectively evaluated concentrations of Ang-1 and Ang-2 at different time-points during febrile neutropenia, and explored the diagnostic accuracy of these mediators as potential predictors of poor outcome in this clinical setting before the development of sepsis complications.

RESULTS

Patients that evolved with septic shock (n = 10) presented higher levels of Ang-2 measured 48 hours after fever onset, and of the Ang-2/Ang-1 ratio at the time of fever onset compared to patients with non-complicated sepsis (n = 31). These levels correlated with sepsis severity scores.

CONCLUSIONS

Our data suggest that imbalances in the concentrations of Ang-1 and Ang-2 are independent and early markers of the risk of developing septic shock and of sepsis mortality in febrile neutropenia, and larger studies are warranted to validate their clinical usefulness. Therapeutic strategies that manipulate this Ang-2/Ang-1 imbalance can potentially offer new and promising treatments for sepsis in febrile neutropenia.

The role of angiogenic factors in predicting clinical outcome in severe bacterial infection in Malawian children

Introduction

Severe sepsis is a disease of the microcirculation, with endothelial dysfunction playing a key role in its pathogenesis and subsequent associated mortality. Angiogenesis in damaged small vessels may ameliorate this dysfunction. The aim of the study was to determine whether the angiogenic factors (vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and angiopoietin-1 (Ang-1) and -2 (Ang-2)) are mortality indicators in Malawian children with severe bacterial infection.

Methods

In 293 children with severe bacterial infection, plasma VEGF, PDGF, FGF, and Ang-1 and Ang-2 were measured on admission; in 50 of the children with meningitis, VEGF, PDGF, and FGF were also measured in the CSF. Healthy controls comprised children from some of the villages of the index cases. Univariable and multivariable logistic regression analyses were performed to develop a prognostic model.

Results

The median age was 2.4 years, and the IQR, 0.7 to 6.0 years. There were 211 children with bacterial meningitis (72%) and 82 (28%) with pneumonia, and 154 (53%) children were HIV infected. Mean VEGF, PDGF, and FGF concentrations were higher in survivors than in nonsurvivors, but only PDGF remained significantly increased in multivariate analysis (P = 0.007). Mean Ang-1 was significantly increased, and Ang-2 was significantly decreased in survivors compared with nonsurvivors (6,000 versus 3,900 pg/ml, P = 0.03; and 7,700 versus 11,900 pg/ml, P = 0.02, respectively). With a logistic regression model and controlling for confounding factors, only female sex (OR, 3.95; 95% CI, 1.33 to 11.76) and low Ang-1 (OR, 0.23; 95% CI, 0.08 to 0.69) were significantly associated with mortality. In children with bacterial meningitis, mean CSF VEGF, PDGF, and FGF concentrations were higher than paired plasma concentrations, and mean CSF, VEGF, and FGF concentrations were higher in nonsurvivors than in survivors (P = 0.02 and 0.001, respectively).

Conclusions

Lower plasma VEGF, PDGF, FGF, and Ang-1 concentrations and higher Ang-2 concentrations are associated with an unfavorable outcome in children with severe bacterial infection. These angiogenic factors may be important in the endothelial dysregulation seen in severe bacterial infection, and they could be used as biomarkers for the early identification of patients at risk of a poor outcome.

Sepsis mediators

During sepsis, the plasma levels of numerous inflammatory markers are enhanced. Some of these markers are the mediators responsible for the syndromes observed during sepsis as well as for organ dysfunction and eventually death. Their role has been demonstrated in experimental models that employed either transgenic and gene-targeted animals or the use of neutralizing agents. Accordingly, anaphylatoxins generated after complement system activation, factors of coagulation and fibrinolysis, proinflammatory cytokines, chemokines, proteases, lipid mediators, nitric oxide, and cell markers of stress (eg, high mobility group box-1) have been shown to contribute to the deleterious events observed during sepsis. On the other hand, the counter-regulation of the inflammatory process, which involves mediators such as anti-inflammatory cytokines and some neuromediators, can jeopardize the immune status of the host and render the patients more sensitive to nosocomial infections.

Acute pyelonephritis during pregnancy changes the balance of angiogenic and anti-angiogenic factors in maternal plasma

OBJECTIVE

Angiogenic factors have been implicated in the pathophysiology of sepsis. In experimental models of sepsis (endotoxemia and/or cecal ligation puncture), there is increased expression of vascular endothelial growth factors (VEGF) and the administration of exogenous soluble VEGF receptor (sVEGFR)-1, an antagonist to VEGF, reduces morbidity and mortality. Moreover, a dramatic elevation in sVEGFR-1 has been demonstrated in human sepsis. Although a balance between angiogenic and anti-angiogenic factors is essential for feto-placental development, the changes of angiogenic factors during pregnancy in the context of infection have never been explored. Angiogenic factors also play crucial roles in the pathophysiology of preeclampsia (PE). This study was conducted to determine if maternal plasma concentrations of placental growth factor (PlGF), sVEGFR-2, and soluble endoglin (sEng) change in pregnancies complicated by acute pyelonephritis (AP) compared with normal pregnancy and PE.

STUDY DESIGN

A case-control study was conducted in patients with AP, normal pregnant (NP) women, and patients with PE (n=36 for each group) matched for gestational age. AP was diagnosed in the presence of fever (temperature >or=38 degrees C), clinical signs of infection, and a positive urine culture for microorganisms. Plasma concentrations of PlGF, sVEGFR-2, and sEng were determined by ELISA. The results of plasma sVEGFR-1 concentrations have previously been reported, but were included in this study to provide a complete picture of the angiogenic/anti-angiogenic profiles. Serum concentrations of interleukin (IL)-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, interferon (IFN)-gamma, granulocyte macrophage colony stimulating factor, and tumor necrosis factor (TNF) were also determined using high sensitivity multiplexed immunoassays in patients with AP and NP.

RESULTS

AP was associated with a lower median plasma concentration of PlGF and sVEGFR-2 than NP (both p<0.001). There were no significant differences in the median plasma concentrations of sEng and sVEGFR-1 between AP and NP (p=0.7 and 0.5, respectively). In contrast, there was a 5-fold decrease of the median plasma concentration of PlGF, and an 8-10-fold increase of the median plasma concentrations of sVEGFR-1 and sEng in PE compared with those in AP (all p<0.001). No significant difference in the median plasma concentration of sVEGFR-2 was observed between patients with PE and AP (p=0.5). Pregnant women with AP had median plasma concentrations of IL-6, IL-7, IL-8, IL-10, IFN-gamma, and TNF-alpha significantly higher than those in NP women (all p<0.001, except IL-7 p=0.004).

CONCLUSION

AP is associated with changes in the profile of angiogenic and anti-angiogenic factors. Although some of these changes resemble those in PE (decreased PlGF and sVEGFR-2), the magnitude of the changes of PlGF is much higher in PE. We conclude that despite high plasma inflammatory cytokine concentrations, acute systemic inflammation in pregnancy has a different angiogenic/anti-angiogenic profile than that of PE.

Altered occludin expression in brain capillaries induced by obstructive jaundice in rats

The development of increased oxidative stress in the context of obstructive cholestasis has been proven in various rats' organs including the brain. The present study aimed to detect alterations of tight junction-associated occludin in rat brain capillaries after bile duct ligation (BDL). In experiment 1, occludin expression was evaluated by Western blot analysis in 5 animals 10 days after BDL and compared with 5 sham-operated ones. In experiment 2, groups of 9 animals each were used to assess occludin levels on the 1st, 5th, and 10th days after BDL and to associate these measurements with the in vivo superoxide radical production measured by means of an ultrasensitive fluorescent assay. The results indicated that occludin expression in BDL animals, as opposed to sham-operated, was significantly reduced at every time point studied, being lowest in the rats remaining on BDL condition for 10 days. Moreover, it was demonstrated that the time-dependent downregulation of occludin expression in the brain endothelial was significantly correlated with the time-dependent increase of brain superoxide radical level, implying a relationship between these two abnormalities. In conclusion, the evidence presented herein suggests the implication of occludin and, therefore, of blood-brain barrier in the pathophysiology of extrahepatic cholestasis.

Sepsis biomarkers: a review

INTRODUCTION

Biomarkers can be useful for identifying or ruling out sepsis, identifying patients who may benefit from specific therapies or assessing the response to therapy.

METHODS

We used an electronic search of the PubMed database using the key words "sepsis" and "biomarker" to identify clinical and experimental studies which evaluated a biomarker in sepsis.

RESULTS

The search retrieved 3370 references covering 178 different biomarkers.

CONCLUSIONS

Many biomarkers have been evaluated for use in sepsis. Most of the biomarkers had been tested clinically, primarily as prognostic markers in sepsis; relatively few have been used for diagnosis. None has sufficient specificity or sensitivity to be routinely employed in clinical practice. PCT and CRP have been most widely used, but even these have limited ability to distinguish sepsis from other inflammatory conditions or to predict outcome.

The association between vascular endothelial growth factor levels and clinically evident peripheral edema in dogs with systemic inflammatory response syndrome

OBJECTIVE

To determine the relationship between plasma vascular endothelial growth factor (VEGF) levels, severity of illness, and edema formation in critically ill dogs.

DESIGN

Prospective, observational, descriptive, clinical study.

SETTING

University Teaching Hospital.

ANIMALS

Twenty-eight dogs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Physical examination and multifrequency bioimpedance (MFBIA) measurements were performed daily on 28 critically ill dogs with evidence of severe inflammatory disease and compared with the corresponding plasma VEGF levels. The change in VEGF values and the relationship between MFBIA measurements and clinical evidence of edema were also examined. Eighteen dogs had a positive VEGF level, 12 dogs had clinical evidence of edema, and 7 dogs had both a positive VEGF level and clinical evidence of edema. There was no statistically significant correlation between VEGF levels and the presence of edema on physical examination (P=0.2). VEGF values were also evaluated with respect to WBC count, survival prediction index, presence of known sepsis, change in extracellular water, and outcome. No statistical relationship could be identified between VEGF levels in the blood of dogs with inflammatory disease and their survival prediction index (P=0.1), the WBC count (P=0.2), or presence of sepsis (P=0.2). Dogs with a VEGF level >70 pg/mL (n=3) were less likely to survive (P=0.04). Because of high variability within and between animals, conclusions regarding changes in MFBIA could not be made, suggesting that this technology requires further refinement and investigation in critically ill dogs.

CONCLUSIONS

A relationship between VEGF and clinically evident increased vascular permeability was not found in this study. Dogs with markedly elevated VEGF levels may be more likely to die, but further studies are needed to determine the diagnostic and prognostic value of VEGF in critically ill dogs.

Vascular endothelial growth factor activation of endothelial cells is mediated by early growth response-3

Endothelial cell activation and dysfunction underlie many vascular disorders, including atherosclerosis, tumor growth, and sepsis. Endothelial cell activation, in turn, is mediated primarily at the level of gene transcription. Here, we show that in response to several activation agonists, including vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha, and thrombin, endothelial cells demonstrate rapid and profound induction of the early growth response (Egr) genes egr-1 and egr-3. In VEGF-treated endothelial cells, induction of Egr-3 was far greater and more prolonged compared with Egr-1. VEGF-mediated stimulation of Egr-3 involved the inducible binding of NFATc, serum response factor, and CREB to their respective consensus motifs in the upstream promoter region of Egr-3. Knockdown of Egr-3 markedly impaired VEGF-mediated proliferation, migration, and tube formation of endothelial cells and blocked VEGF-induced monocyte adhesion. Egr-3 knockdown abrogated VEGF-mediated vascular outgrowth from ex vivo aortic rings and attenuated Matrigel plug vascularization and melanoma tumor growth in vivo. Together, these findings suggest that Egr-3 is a critical determinant of VEGF signaling in activated endothelial cells. Thus, Egr-3 represents a potential therapeutic target in VEGF-mediated vasculopathic diseases.

A systems biology perspective on sVEGFR1: its biological function, pathogenic role and therapeutic use

Angiogenesis is the growth of new capillaries from pre-existent microvasculature. A wide range of pathological conditions, from atherosclerosis to cancer, can be attributed to either excessive or deficient angiogenesis. Central to the physiological regulation of angiogenesis is the vascular endothelial growth factor (VEGF) system – its ligands and receptors (VEGFRs) are thus prime molecular targets of pro-angiogenic and anti-angiogenic therapies. Of growing interest as a prognostic marker and therapeutic target in angiogenesis-dependent diseases is soluble VEGF receptor-1 (sVEGFR1, also known as sFlt-1) – a truncated version of the cell membrane-spanning VEGFR1. For instance, it is known that sVEGFR1 is involved in the endothelial dysfunction characterizing the pregnancy disorder of pre-eclampsia, and sVEGFR1’s therapeutic potential as an anti-angiogenic agent is being evaluated in pre-clinical models of cancer. This mini review begins with an examination of the protein domain structure and biomolecular interactions of sVEGFR1 in relation to the full-length VEGFR1. A synopsis of known and inferred physiological and pathological roles of sVEGFR1 is then given, with emphasis on the utility of computational systems biology models in deciphering the molecular mechanisms by which sVEGFR1’s purported biological functions occur. Finally, we present the need for a systems biology perspective in interpreting circulating VEGF and sVEGFR1 concentrations as surrogate markers of angiogenic status in angiogenesis-dependent diseases.

Inhibition of VEGF or TGF-{beta} signaling activates endothelium and increases leukocyte rolling

OBJECTIVE

Motivated by the central roles that vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta play in the assembly and maintenance of the vasculature, we examined the impact of systemic VEGF or TGF-beta signal inhibition on endothelial activation as detected by leukocyte-endothelial interactions.

METHODS AND RESULTS

VEGF or TGF-beta inhibition, accomplished using adenovirus expression of soluble Flt1 (Ad-sFlt1) or soluble endoglin (Ad-sEng), resulted in a significant increase in the number of leukocytes rolling along the mesenteric venous endothelium and a significant decrease in rolling velocity in Ad-sEng mice. Neutralization of VEGF or TGF-beta resulted in endothelial surface expression of P-selectin and impaired peripheral vasodilatation. Neither inhibition of VEGF nor TGF-beta was associated with platelet or leukocyte activation, as detected by the activation markers platelet P-selectin and the active integrin alphaIIbbetaIII, or by leukocyte expression of L-selectin. Soluble vascular cell adhesion molecule (VCAM)-1 and E-selectin were increased in sEng-expressing mice, indicating higher levels of these adhesion receptors.

CONCLUSIONS

VEGF or TGF-beta neutralization leads to impaired endothelium-mediated vasodilatation and elevated expression of surface adhesion molecules, resulting in increased leukocyte adhesion. These results indicate an essential role for both VEGF and TGF-beta in maintaining the endothelium in a nonactivated state and have implications for therapeutic approaches that neutralize VEGF or TGF-beta.

Shock-induced stress induces loss of microvascular endothelial Tie2 in the kidney which is not associated with reduced glomerular barrier function

Both hemorrhagic shock and endotoxemia induce a pronounced vascular activation in the kidney which coincides with albuminuria and glomerular barrier dysfunction. We hypothesized that changes in Tie2, a vascular restricted receptor tyrosine kinase shown to control microvascular integrity and endothelial inflammation, underlie this loss of glomerular barrier function. In healthy murine and human kidney, Tie2 is heterogeneously expressed in all microvascular beds, although to different extents. In mice subjected to hemorrhagic and septic shock, Tie2 mRNA and protein were rapidly, and temporarily, lost from the renal microvasculature, and normalized within 24 h after initiation of the shock insult. The loss of Tie2 protein could not be attributed to shedding as both in mice and healthy volunteers subjected to endotoxemia, sTie2 levels in the systemic circulation did not change. In an attempt to identify the molecular control of Tie2, we activated glomerular endothelial cell cultures and human kidney slices in vitro with LPS or TNF-α, but did not observe a change in Tie2 mRNA levels. In parallel to the loss of Tie2 in vivo, an overt influx of neutrophils in the glomerular compartment, which coincided with proteinuria, was seen. As neutrophil-endothelial cell interactions may play a role in endothelial adaptation to shock, and these effects cannot be mimicked in vitro, we depleted neutrophils before shock induction. While this neutrophil depletion abolished proteinuria, Tie2 was not rescued, implying that Tie2 may not be a major factor controlling maintenance of the glomerular filtration barrier in this model.

The Down syndrome critical region gene 1 short variant promoters direct vascular bed-specific gene expression during inflammation in mice

Down syndrome critical region gene 1 (DSCR-1) short variant (DSCR-1s) is an inhibitor of calcineurin/NFAT signaling encoded by exons 4-7 of DSCR1. We previously reported that VEGF induces DSCR-1s expression in endothelial cells, which in turn negatively feeds back to attenuate endothelial cell activation. Here, in order to characterize the role of the promoter that drives DSCR-1s expression in mediating inducible expression in vivo and to determine the functional relevance of DSCR-1s in inflammation, we targeted a DNA construct containing 1.7 kb of the human DSCR1s promoter coupled to the lacZ reporter to the hypoxanthine guanine phosphoribosyl transferase (Hprt) locus of mice. We determined that lacZ was uniformly expressed in the endothelium of transgenic embryos but was markedly downregulated postnatally. Systemic administration of VEGF or LPS in adult mice resulted in cyclosporine A-sensitive reactivation of the DSCR1s promoter and endogenous gene expression in a subset of organs, including the heart and brain. The DSCR1s promoter was similarly induced in the endothelium of tumor xenografts. In a mouse model of endotoxemia, DSCR-1s-deficient mice demonstrated increased sepsis mortality, whereas adenovirus-mediated DSCR-1s overexpression protected against LPS-induced lethality. Collectively, these data suggest that the DSCR1s promoter directs vascular bed-specific expression in activated endothelium and that DSCR-1s serves to dampen the host response to infection.

Vascular endothelial growth factor (VEGF) receptor-2 tyrosine 1175 signaling controls VEGF-induced von Willebrand factor release from endothelial cells via phospholipase C-gamma 1- and protein kinase A-dependent pathways

There is increasing evidence that vascular endothelial growth factor (VEGF) contributes to inflammation independent of its angiogenic functions. Targeting some of the components in endothelial Weibel-Palade bodies (WPBs) effectively inhibits VEGF-induced inflammation, but little is known about how VEGF regulates WPB exocytosis. In this study, we showed that VEGF receptor-2 (VEGFR2), but not VEGFR1, is responsible for VEGF-induced release of von Willebrand factor (vWF), a major marker of WPBs. This is in good contrast to VEGF-stimulated interleukin-6 release from endothelium, which is selectively mediated through VEGFR1. We further demonstrated that VEGFR2-initiated phospholipase C-gamma1 (PLCgamma1)/calcium signaling is important but insufficient for full vWF release, suggesting the possible participation of another effector pathway. We found that cAMP/protein kinase A (PKA) signaling is required for full vWF release. Importantly, a single mutation of Tyr(1175) in the C terminus of VEGFR2, a tyrosine residue crucial for embryonic vasculogenesis, abolished vWF release, concomitant with defective activations of both PLCgamma1 and PKA. These data suggest that Tyr(1175) mediates both PLCgamma1-dependent and PKA-dependent signaling pathways. Taken together, our results not only reveal a novel Tyr(1175)-mediated signaling pathway but also highlight a potentially new therapeutic target for the management of vascular inflammation.

Elevated serum angiopoietin 2 levels are associated with increased mortality in sepsis

The vascular growth factor angiopoietin 2 (Ang-2) is known to promote inflammation and endothelial dysfunction, but its prognostic capacity and relationship to outcomes in human sepsis are unknown. This is a prospective observational cohort study of 66 patients newly admitted to a tertiary care medical intensive care unit (ICU), which included ICU patients with no sepsis (n = 20) as well as those with sepsis (n = 10), severe sepsis (n = 12), and septic shock (n = 24). Clinical data were collected until hospital discharge, and Ang-2 and IL-6 levels were determined on specimens obtained after ICU admission. Serum Ang-2 correlated with IL-6 and severity-of-illness scores. In the septic cohort, circulating Ang-2 levels were significantly higher (P = 0.01) in those who died (24.9 ng/mL; interquartile range, 21.5-38.0 ng/mL) compared with those who survived (13.5 ng/mL; interquartile range, 8.1-21.6 ng/mL). Elevated circulating serum Ang-2 levels are associated with increased hospital mortality in patients with sepsis.

Antiinflammatory effects of the ETS factor ERG in endothelial cells are mediated through transcriptional repression of the interleukin-8 gene

ERG (Ets-related gene) is an ETS transcription factor that has recently been shown to regulate a number of endothelial cell (EC)-restricted genes including VE-cadherin, von Willebrand factor, endoglin, and intercellular adhesion molecule-2. Our preliminary data demonstrate that unlike other ETS factors, ERG exhibits a highly EC-restricted pattern of expression in cultured primary cells and several adult mouse tissues including the heart, lung, and brain. In response to inflammatory stimuli, such as tumor necrosis factor-alpha, we observed a marked reduction of ERG expression in ECs. To further define the role of ERG in the regulation of normal EC function, we used RNA interference to knock down ERG. Microarray analysis of RNA derived from ERG small interfering RNA- or tumor necrosis factor-alpha-treated human umbilical vein (HUV)ECs revealed significant overlap (P<0.01) in the genes that are up- or downregulated. Of particular interest to us was a significant change in expression of interleukin (IL)-8 at both protein and RNA levels. Exposure of ECs to tumor necrosis factor-alpha is known to be associated with increased neutrophil attachment. We observed that knockdown of ERG in HUVECs is similarly associated with increased neutrophil attachment compared to control small interfering RNA-treated cells. This enhanced adhesion could be blocked with IL-8 neutralizing or IL-8 receptor blocking antibodies. ERG can inhibit the activity of the IL-8 promoter in a dose dependent manner. Direct binding of ERG to the IL-8 promoter in ECs was confirmed by chromatin immunoprecipitation. In summary, our findings support a role for ERG in promoting antiinflammatory effects in ECs through repression of inflammatory genes such as IL-8.

Relationship between circulating vascular endothelial growth factor and its soluble receptors in adults with dengue virus infection: a case-control study

BACKGROUND

We performed a case-control study to assess the relationship between vascular endothelial growth factor (VEGF) and its soluble receptors (sVEGFR-1 and 2) in adult patients with dengue fever (DF) and dengue hemorrhagic fever (DHF).

METHODS

We recruited 60 adult patients (34 DF and 26 DHF) with serologically-confirmed dengue infections, 10 patients with non-hemorrhagic infections, and 31 community-based healthy volunteers. The levels of VEGF, sVEGFR-1, and sVEGFR-2 were measured and the differences in these markers were compared using one-way analysis of variance (ANOVA), which was adjusted for multiple comparisons.

RESULTS

We observed lower VEGF levels in DF and DHF compared to study controls (p<0.01). sVEGFR-1 was higher in DHF than DF, whilst sVEGFR-2 was lower in DF and DHF compared to study controls (all p<0.01). In DHF, lower VEGF levels were observed in older patients. The use of a single marker, sVEGFR-1>350 pg/ml, was predictive of DHF.

CONCLUSION

The changes in VEGF and its soluble receptors highlight the importance of vascular permeability cytokines in the pathogenesis of DHF.

Vascular endothelial growth factor induces protein kinase D-dependent production of proinflammatory cytokines in endothelial cells

Emerging evidence indicates that vascular endothelial growth factor (VEGF) plays a critical role in host inflammatory responses in several disease states, including atherosclerosis, sepsis, and rheumatoid arthritis. In this study, we determined the effect of VEGF on endothelial induction of proinflammatory cytokines and investigated the responsible signal pathways. By using a cytokine antibody array that detects the end point protein products released from endothelial cells (ECs), we found that VEGF, via VEGF receptor 2 (VEGFR2), predominantly induced the production of proinflammatory cytokine interleukin (IL)-6 and CXC chemokines IL-8 and growth-related oncogene-alpha (GRO-alpha) in ECs but not in leukocytes among 36 cytokines in the array. The production of these inflammatory cytokines by VEGF was much stronger than the induction of cell adhesion molecule in ECs. We further found that the cytokine production by VEGF was essentially mediated by the Gö-6976-sensitive protein kinase D (PKD) family kinases. Importantly, the VEGF-induced production of IL-6, IL-8, and GRO-alpha was inhibited approximately 70%, 40%, or 37% by PKD1 silencing (more than 90% knockdown) with three small interference RNAs that target different PKD1 regions. Moreover, silencing PKD2 downregulated VEGFR2 and markedly inhibited the cytokine production by VEGF in ECs. Our results indicate that VEGF, via VEGFR2-PKD1 axis, induces the production of proinflammatory cytokine IL-6, IL-8, and GRO-alpha in ECs but not in leukocytes, which may offer new insights into the mechanism of the proinflammatory activity of VEGF.

P-selectin glycoprotein-ligand-1 regulates pulmonary recruitment of neutrophils in a platelet-independent manner in abdominal sepsis

BACKGROUND AND PURPOSE

Neutrophil-mediated lung injury is an insidious feature in sepsis although the mechanisms regulating pulmonary recruitment of neutrophils remain elusive. Here, we investigated the role of P-selectin glycoprotein-ligand-1 (PSGL-1) in sepsis-induced neutrophil recruitment and tissue injury in the lung.

EXPERIMENTAL APPROACH

Bronchoalveolar infiltration of neutrophils, levels of myeloperoxidase, oedema formation and CXC chemokines were determined 24 h after caecal ligation and puncture (CLP) in mice. Animals were pretreated with a control antibody, monoclonal antibodies directed against PSGL-1 and P-selectin as well as a platelet-depleting antibody directed against GP1balpha.

KEY RESULTS

CLP caused pulmonary damage characterized by oedema formation, neutrophil infiltration and increased levels of CXC chemokines in the lung. Immunoneutralization of PSGL-1 or P-selectin reduced CLP-induced neutrophil recruitment in the bronchoalveolar space by more than 56% and lung myeloperoxidase activity by 62%. Notably, the inhibitory effect of the anti-PSGL-1 antibody on sepsis-induced neutrophil infiltration was also observed in platelet-depleted mice. Moreover, inhibition of PSGL-1 and P-selectin abolished CLP-induced oedema formation and tissue damage in the lung. CLP-induced formation of CXC chemokines was not changed in mice pretreated with the anti-PSGL-1 and anti-P-selectin antibodies.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that PSGL-1 plays a key role in pulmonary infiltration of neutrophils as well as lung oedema associated with abdominal sepsis. Moreover, our findings suggest that PSGL-1-dependent neutrophil recruitment is independent of circulating platelets. Thus, these novel findings indicate that PSGL-1 may be a useful target to protect against sepsis-induced accumulation of neutrophils and tissue damage in the lung.

Endogenous EPCR/aPC-PAR1 signaling prevents inflammation-induced vascular leakage and lethality

Protease activated receptor 1 (PAR1) signaling can play opposing roles in sepsis, either promoting dendritic cell (DC)-dependent coagulation and inflammation or reducing sepsis lethality due to activated protein C (aPC) therapy. To further define this PAR1 paradox, we focused on the vascular effects of PAR1 signaling. Pharmacological perturbations of the intravascular coagulant balance were combined with genetic mouse models to dissect the roles of endogenously generated thrombin and aPC during escalating systemic inflammation. Acute blockade of the aPC pathway with a potent inhibitory antibody revealed that thrombin-PAR1 signaling increases inflammation-induced vascular hyperpermeability. Conversely, aPC-PAR1 signaling and the endothelial cell PC receptor (EPCR) prevented vascular leakage, and pharmacologic or genetic blockade of this pathway sensitized mice to LPS-induced lethality. Signaling-selective aPC variants rescued mice with defective PC activation from vascular leakage and lethality. Defects in the aPC pathway were fully compensated by sphingosine 1 phosphate receptor 3 (S1P3) deficiency or by selective agonists of the S1P receptor 1 (S1P1), indicating that PAR1 signaling contributes to setting the tone for the vascular S1P1/S1P3 balance. Thus, the activating proteases and selectivity in coupling to S1P receptor subtypes determine vascular PAR1 signaling specificity in systemic inflammatory response syndromes in vivo.

LFA-1 and MAC-1 mediate pulmonary recruitment of neutrophils and tissue damage in abdominal sepsis

Neutrophil-mediated lung damage is an insidious feature in septic patients, although the adhesive mechanisms behind pulmonary recruitment of neutrophils in polymicrobial sepsis remain elusive. The aim of the present study was to define the role of lymphocyte function antigen-1 (LFA-1) and membrane-activated complex 1 (Mac-1) in septic lung injury. Pulmonary edema, bronchoalveolar infiltration of neutrophils, levels of myeloperoxidase, and CXC chemokines were determined after cecal ligation and puncture (CLP). Mice were treated with monoclonal antibodies directed against LFA-1 and Mac-1 before CLP induction. Cecal ligation and puncture induced clear-cut pulmonary damage characterized by edema formation, neutrophil infiltration, and increased levels of CXC chemokines in the lung. Notably, immunoneutralization of LFA-1 or Mac-1 decreased CLP-induced neutrophil recruitment in the bronchoalveolar space by more than 64%. Moreover, functional inhibition of LFA-1 and Mac-1 abolished CLP-induced lung damage and edema. However, formation of CXC chemokines in the lung was intact in mice pretreated with the anti-LFA-1 and anti-Mac-1 antibodies. Our data demonstrate that both LFA-1 and Mac-1 regulate pulmonary infiltration of neutrophils and lung edema associated with abdominal sepsis. Thus, these novel findings suggest that LFA-1 or Mac-1 may serve as targets to protect against lung injury in polymicrobial sepsis.

Excess circulating angiopoietin-2 is a strong predictor of mortality in critically ill medical patients

Introduction

The endothelial specific angiopoietin (Ang)-Tie2 ligand-receptor system has been identified as a non-redundant mediator of endothelial activation in experimental sepsis. Binding of circulating Ang-1 to the Tie2 receptor protects the vasculature from inflammation and leakage, whereas binding of Ang-2 antagonises Tie2 signalling and disrupts endothelial barrier function. Here, we examine whether circulating Ang-1 and/or Ang-2 independently predict mortality in a cohort of critically ill medical patients.

Methods

Circulating vascular endothelial growth factor (VEGF), Ang-1 and Ang-2 were prospectively measured in sera from 29 healthy controls and 43 medical ICU patients by immunoradiometric assay (IRMA) and ELISA, respectively. Survival after 30 days was the primary outcome studied.

Results

Median serum Ang-2 concentrations were increasingly higher across the following groups: healthy controls, patients without sepsis, patients with sepsis and patients with septic shock. In contrast, Ang-1 and VEGF concentrations were significantly lower in all patient groups compared with healthy controls. Ang-2 correlated with partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂), tissue hypoxia, Sequential Organ Failure Assessment (SOFA) and Physiology and Chronic Health Evaluation II (APACHE II) score. Multivariate Cox regression analyses confirmed a strong independent prognostic impact of high Ang-2 as a novel marker of 30-day survival.

Conclusions

A marked imbalance of the Ang-Tie system in favour of Ang-2 is present in critically ill medical patients. Our findings highlight the independent prognostic impact of circulating Ang-2 in critical illness. Ang-2 may be used as a readily available powerful predictor of outcome and may open new perspectives to individualise treatment in the ICU.

Vascular endothelial growth factor and soluble fms-like tyrosine kinase-1 in septic shock patients treated with direct hemoperfusion with a polymyxin B-immobilized fiber column

Sepsis is characterized by a systemic inflammatory response to a microbial pathogen. In sepsis, capillary permeability is a tightly regulated feature of microcirculation in all organ beds and is fundamentally altered. We investigated the vascular endothelial growth factor (VEGF) level as a vascular permeability factor and the soluble fms-like tyrosine kinase-1 (Flt-1) level as an antagonist of the VEGF receptors. Serum VEGF and soluble Flt-1 levels in 21 patients with septic shock, who were treated with direct hemoperfusion with a polymyxin B-immobilized fiber column (DHP-PMX), were measured by enzyme-linked immunoassay. The VEGF and the soluble Flt-1 levels were more elevated in patients with septic shock than in controls. Between 14 survivors and 7 non-survivors, there was no significant difference in VEGF level before the DHP-PMX therapy, but the soluble Flt-1 level of survivors was significantly lower than that of non-survivors. Although there was no significant difference between starting and ending VEGF levels in survivors, in non-survivors the VEGF level at the end of DHP-PMX therapy was significantly lower than that at the start. In survivors, the soluble Flt-1 level at the end of DHP-PMX therapy was significantly lower than that at the start. On the other hand, in non-survivors, there was no significant difference between the ending and starting soluble Flt-1 levels. The soluble Flt-1 level may be a suitable marker of disease severity and mortality.

Angiopoietin-2 is associated with decreased endothelial nitric oxide and poor clinical outcome in severe falciparum malaria

Adherence of parasitized erythrocytes to activated endothelium causes microvascular obstruction, tissue ischemia, and clinical complications in severe malaria (SM); however, the mechanisms leading to endothelial activation remain unclear. The angiogenic factors, angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF) are modulators of endothelial activation, with Ang-2 release from Weibel-Palade bodies (WPBs) being regulated by endothelial nitric oxide (NO). We explored the relationships between endothelial NO bioavailability, Ang-2, VEGF, tissue perfusion, and clinical outcomes in SM. We measured plasma Ang-2 and VEGF, together with biomarkers of severity from 146 adults with and without SM, in parallel with longitudinal measures of endothelial function by using reactive hyperemia peripheral arterial tonometry (a measure of endothelial NO bioavailability). Regression was used to relate concentrations of Ang-2/VEGF with malaria disease severity, biomarkers of perfusion, endothelial activation, and parasite biomass. The longitudinal relationship between Ang-2 and endothelial function was assessed by using a mixed-effects model. Ang-2 concentrations were elevated in SM and associated with increased venous lactate, plasma intercellular cell adhesion molecule-1 concentrations, parasite biomass, and mortality. In contrast, VEGF concentrations were inversely associated with these biomarkers. Ang-2 concentrations were significantly better predictors of death than venous lactate (P = 0.03). Recovery of endothelial function was associated with falling concentrations of Ang-2. Ang-2 release from endothelial cells with reduced NO bioavailability is likely to contribute to endothelial activation, sequestered parasite biomass, impaired perfusion, and poor outcome in severe falciparum malaria. Agents that improve endothelial NO, reduce WPB exocytosis, and/or antagonize Ang-2 may have therapeutic roles in SM.

Elevated levels of placental growth factor represent an adaptive host response in sepsis

Recently, we demonstrated that circulating levels of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are increased in sepsis (Yano, K., P.C. Liaw, J.M. Mullington, S.C. Shih, H. Okada, N. Bodyak, P.M. Kang, L. Toltl, B. Belikoff, J. Buras, et al. 2006. J. Exp. Med. 203:1447–1458). Moreover, enhanced VEGF/Flk-1 signaling was shown to contribute to sepsis morbidity and mortality. We tested the hypothesis that PlGF also contributes to sepsis outcome. In mouse models of endotoxemia and cecal ligation puncture, the genetic absence of PlGF or the systemic administration of neutralizing anti-PlGF antibodies resulted in higher mortality compared with wild-type or immunoglobulin G–injected controls, respectively. The increased mortality associated with genetic deficiency of PlGF was reversed by adenovirus (Ad)-mediated overexpression of PlGF. In the endotoxemia model, PlGF deficiency was associated with elevated circulating levels of VEGF, induction of VEGF expression in the liver, impaired cardiac function, and organ-specific accentuation of barrier dysfunction and inflammation. Mortality of endotoxemic PlGF-deficient mice was increased by Ad-mediated overexpression of VEGF and was blocked by expression of soluble Flt-1. Collectively, these data suggest that up-regulation of PlGF in sepsis is an adaptive host response that exerts its benefit, at least in part, by attenuating VEGF signaling.

A prospective, observational study of soluble FLT-1 and vascular endothelial growth factor in sepsis

Prior murine and human studies suggest that vascular endothelial growth factor (VEGF) contributes to endothelial cell activation and severity of illness in sepsis. Furthermore, circulating levels of soluble VEGF receptor 1 (sFLT) levels were found to increase as part of the early response to sepsis in mice. The objective of the study was to evaluate the blood levels of free VEGF-A and sFLT in patients presenting to the emergency department (ED) with suspected infection and to assess the relationship of these levels with severity of illness and inflammation. It was a prospective, observational study initiated in the ED of an urban, tertiary care, university hospital. Inclusion criteria were (1) ED patients aged 18 years or older and (2) clinical suspicion of infection. Eighty-three patients were enrolled in the study. The major findings were that (1) the mean VEGF and sFLT levels were increasingly higher across the following groups: noninfected control patients, infected patients without shock, and septic shock patients; (2) initial and 24-h VEGF levels had a significant correlation with the presence of septic shock at 24 h; (3) initial and 24-h sFLT levels correlated with Acute Physiology Age Chronic Health Evaluation II and Sepsis-related Organ/Failure Assessment scores initially and at 24 h; and (4) VEGF and sFLT levels correlated with inflammatory cascade activation. This is the first report of sFLT as a potential new marker of severity in patients with sepsis. Vascular endothelial cell growth factor and its signaling axis are important in the endothelial cell response to sepsis, and further elucidation of these mechanisms may lead to advances in future diagnostic and therapeutic opportunities.

Natural selection of FLT1 alleles and their association with malaria resistance in utero

Placental malaria (PM) caused by Plasmodium falciparum contributes significantly to infant mortality in sub-Saharan Africa and is associated with pregnancy loss. We hypothesized that fetal genes that modify PM would be associated with fetal fitness. During PM, placental trophoblasts produce soluble fms-like tyrosine kinase 1 (sFlt1), also known as soluble VEGF receptor 1, an angiogenesis inhibitor associated with preeclampsia. Here we present a study examining the genotype of the fms-related tyrosine kinase 1 (FLT1) 3' UTR in Tanzanian mother-infant pairs. First-time mothers suffer the most PM, and newborn FLT1 genotype distribution differed by birth order, with newborns of first-time mothers outside of Hardy-Weinberg equilibrium (HWE) during peak PM season. Among first-time but not other mothers, maternal FLT1 genotype was associated with a history of prior pregnancy loss. During PM, newborn FLT1 genotype was associated with low birth weight and placental inflammatory gene expression. FLT1 genotype was also associated with Flt1 levels among study subjects and in vitro. Thus, FLT1 variants confer fetal fitness in utero and are associated with the maternal immune response during PM. This indicates that FLT1 is under natural selection in a malaria endemic area and that human exposure to malaria can influence the evolutionary genetics of the maternal-fetal relationship.

Pre-existing renal disease promotes sepsis-induced acute kidney injury and worsens outcome

While it is known that risk of death from sepsis is higher in patients with pre-existing chronic kidney disease its mechanism is unknown. To study this we established a two-stage mouse model where renal disease was first induced by folic acid injection followed by sub-lethal cecal ligation and puncture to induce sepsis. Septic mice with pre-existing renal disease had significantly higher mortality, serum creatinine, vascular permeability, plasma vascular endothelial growth factor (VEGF) levels, bacteremia, serum IL-10, splenocyte apoptosis and more severe septic shock when compared to septic mice without pre-existing disease. To evaluate the contribution of vascular and immunological dysfunction, we treated the folate-septic mice with soluble Flt-1 to bind VEGF and chloroquine to reduce splenocyte apoptosis. These treatments together resulted in a significant improvement in kidney injury, hemodynamics and survival. Our study shows that the sequential mouse model mimics human sepsis frequently complicated by pre-existing renal disease and might be useful in evaluating preventive and therapeutic strategies.

Combined inhibition of complement and CD14 abolish E. coli-induced cytokine-, chemokine- and growth factor-synthesis in human whole blood

The relative role of complement and CD14 in E. coli-induced cytokine synthesis in an in vitro human whole blood model of sepsis was examined. Fresh lepirudin-anticoagulated whole blood was incubated with E. coli for 2h. Monoclonal antibodies or a C5a receptor antagonist were used to block complement. Inflammatory mediators (n=27) were measured by multiplex technology, selected cytokine mRNA by real time PCR, and CD11b, oxidative burst and phagocytosis by flow cytometry. E. coli significantly increased 18 of the 27 inflammatory mediators, including proinflammatory cytokines (TNF-alpha, IL-6, INF-gamma and IL-1beta), chemokines (IL-8, MCP-1, MIP-1alpha, MIP-1beta, eotaxin and IP-10), growth factors (VEGF, FGF-basic, G-CSF and GM-CSF) and other interleukins (IL-9, IL-15 and IL-17). Notably, the increases in all mediators were abolished by a combined inhibition of CD14 and complement using anti-C2 and anti-factor D in combination, whereas the relative effect of the inhibition of complement and CD14 varied. In comparison, a C5a receptor antagonist and anti-CD14 in combination reduced cytokine synthesis less efficiently. Real time PCR analysis confirmed that the cytokine synthesis was blocked at the mRNA level. Similarly, E. coli-induced CD11b up-regulation, oxidative burst and phagocytosis was totally inhibited by CD14, anti-C2 and anti-factor D in combination after 2h incubation. In conclusion, the combined inhibition of complement using anti-C2, anti-factor D and CD14 almost completely inhibits the E. coli-induced inflammatory response. The combined approach may therefore be a new treatment regimen in Gram-negative sepsis.

Vascular endothelial growth factor in severe sepsis and septic shock

BACKGROUND

Vascular endothelial growth factor (VEGF) levels have been shown to be elevated in severe sepsis. We investigated the value of VEGF in predicting organ dysfunction and hospital mortality in adult patients with severe sepsis.

METHODS

We conducted a prospective observational cohort study in 24 closed multidisciplinary intensive care units (ICU) in Finland. All ICU admission episodes (4500) were screened for severe sepsis from November 1, 2004, to February 28, 2005. Patients were eligible if they fulfilled the criteria for severe sepsis.

RESULTS

Severe sepsis was found in 470 patients. Laboratory samples were obtained after informed consent from 250 patients at study entry (day 0) and from 215 patients after 72 h. These samples were compared with samples from 30 healthy individuals. The ICU mortality was 13.2% and hospital mortality 26%. Median serum VEGF concentrations on day 0 were 423 pg/mL (interquartile range [IQR] 159 and 858 pg/mL), and after 72 h were 521 pg/mL (IQR 182 and 1092 pg/mL), which were both higher than in healthy controls (P = 0.029 and 0.003, respectively). Low VEGF concentrations were associated with more severe renal and hematological dysfunction (Sequential Organ Failure Assessment scores 3-4 compared with scores 0-2). VEGF concentrations in day 0 and after 72 h were lower in nonsurvivors (P = 0.01 and <0.01, respectively) than in survivors, but the receiver operating characteristic curve analyses of concentrations of VEGF on day 0 and at 72 h revealed areas under the curve of 0.58 and 0.63 (95% confidence limits 0.48-0.68 and 0.54-0.72, P = 0.1 and 0.009, respectively).

CONCLUSIONS

VEGF concentrations are increased in patients with severe sepsis. Low concentrations are associated with hematological and renal dysfunction. VEGF concentrations were lower in nonsurvivors than in survivors, but did not adequately predict hospital mortality in patients with severe sepsis.

Novel PKC signaling is required for LPS-induced soluble Flt-1 expression in macrophages

In vitro activation of macrophages by LPS induces rapid release of vascular endothelial growth factor (VEGF) and soluble fms-like tyrosine kinase-1 receptor (sFlt-1), which are thought to be the effectors to cause sepsis. However, the signal pathway that controls the VEGF and sFlt-1 expressions in LPS-activated macrophages remains unclear. In this study, we demonstrated that phosphorylation of protein kinase C (PKC)delta played a key role in the VEGF and sFlt-1 signaling pathway of LPS-activated macrophages. PKC is a family of serine-threonine kinases, which are classified into three major groups based on homology and cofactor requirements: conventional PKCs, novel PKCs, and atypical PKCs. In the murine RAW264.7 cells, as well as in primary human monocytes/macrophages, pretreatment with a general PKC inhibitor GF109203X or with a novel PKCdelta inhibitor rottlerin or overexpression of a kinase-inactive form of PKCdelta (K376R) eliminated LPS-induced sFlt-1 expression and augmented LPS-induced VEGF expression at the protein and the transcription levels. In contrast, Gö6976, an inhibitor for the conventional PKCs, or myristoylated PKCzeta pseudosubstrate peptide, an inhibitor for the atypical PKCs, failed to exert the same effects. These data suggest that PKCdelta signaling is involved in LPS-induced sFlt-1 expression and serves as a negative mediator in LPS-induced VEGF expression in macrophages. A novel strategy controlling the LPS-induced PKC pathways, especially the PKCdelta isoform, may be developed based on this study.

New biomarkers in an acute model of live Escherichia coli-induced sepsis in pigs

We developed a live Escherichia coli model of acute sepsis in pigs with emphasize on biomarkers reflecting the early inflammatory response of sepsis. Healthy pigs, 25-35 kg, were challenged intravenously (IV) (n = 12) or intrapulmonary (n = 6) with live E. coli and observed for 3 and 5 h respectively. Control pigs received culture medium (n = 6 + 3). Haemodynamic parameters and a broad panel of inflammatory mediators were measured. The dose of bacteria was carefully titrated to obtain a condition resembling the early phase of human septic shock. The IV group displayed a pro-inflammatory response [significant increase in tumour necrosis factor-alpha, interleukin (IL)-6 and IL-8] and an early anti-inflammatory response (significant increase in IL-10). For the first time, we demonstrate a significant increase in IL-12 and matrix metalloproteinase-9 (MMP) early in pig sepsis. Coagulation was activated (significant increase in thrombin-antithrombin complexes) and there was a significant decrease in the serum proteins suggesting capillary leakage. Haemodynamic parameters reflected a septic condition with significant decrease in systemic blood pressure, increases in heart rate, pulmonary artery pressure and base deficit. None of these changes was observed in the control group. Interleukin-1beta and vascular endothelial growth factor increased in both groups. Nitric oxide measurements suggested an initial pulmonary vascular endothelial inflammatory response. The intrapulmonary group, which did not resemble septic condition, showed a substantial increase in MMP-9. In this porcine model of sepsis, IL-12 and MMP-9 were detected for the first time. These biomarkers may have an impact in the understanding and future treatment of sepsis.

Resuscitating the microcirculation in sepsis: the central role of nitric oxide, emerging concepts for novel therapies, and challenges for clinical trials

Microcirculatory dysfunction is a critical element of the pathogenesis of severe sepsis and septic shock. In this Bench-to-Bedside review, we present: 1) the central role of the microcirculation in the pathophysiology of sepsis; 2) new translational research techniques of in vivo video microscopy for assessment of microcirculatory flow in human subjects; 3) clinical investigations that reported associations between microcirculatory dysfunction and outcome in septic patients; 4) the potential role of novel agents to "rescue" the microcirculation in sepsis; 5) current challenges facing this emerging field of clinical investigation; and 6) a framework for the design of future clinical trials aimed to determine the impact of novel agents on microcirculatory flow and organ failure in patients with sepsis. We specifically focus this review on the central role and vital importance of the nitric oxide (NO) molecule in maintaining microcirculatory homeostasis and patency, especially when the microcirculation sustains an insult (as with sepsis). We also present the scientific rationale for clinical trials of exogenous NO administration to treat microcirculatory dysfunction and augment microcirculatory blood flow in early sepsis therapy.

Alterations in plasma soluble vascular endothelial growth factor receptor-1 (sFlt-1) concentrations during coronary artery bypass graft surgery: relationships with post-operative complications

Background

Plasma concentrations of sFlt-1, the soluble form of the vascular endothelial growth factor receptor (VEGF), markedly increase during coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). We investigated if plasma sFlt-1 values might be related to the occurrence of surgical complications after CABG.

Methods

Plasma samples were collected from the radial artery catheter before vascular cannulation and after opening the chest, at the end of ECC just before clamp release, after cross release, after weaning from ECC, at the 6^th and 24^th post-operative hour. Thirty one patients were investigated. The presence of cardiovascular, haematological and respiratory dysfunctions was prospectively assessed. Plasma sFlt-1 levels were measured with commercially ELISA kits.

Results

Among the 31 investigated patients, 15 had uneventful surgery. Patients with and without complications had similar pre-operative plasma sFlt-1 levels. Lowered plasma sFlt-1 levels were observed at the end of ECC in patients with haematological (p = 0.001, ANOVA) or cardiovascular (p = 0.006) impairments, but not with respiratory ones (p = 0.053), as compared to patients with uneventful surgery.

Conclusion

These results identify an association between specific post-CABG complication and the lower release of sFlt-1 during ECC. sFlt-1-induced VEGF neutralisation might, thus, be beneficial to reduce the development of post-operative adverse effects after CABG.

Priming effect of homocysteine on inducible vascular cell adhesion molecule-1 expression in endothelial cells

Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis, as well as for arterial and venous thrombosis. However, the mechanisms through which elevated circulating levels of homocysteine cause vascular injury and promote thrombosis remain unclear. Here, we tested the hypothesis that homocysteine (Hcy) sensitizes endothelial cells to the effect of inflammatory mediators. Human umbilical vein endothelial cells (HUVEC) were incubated with Hcy 1.0 mM for varying time points, and then treated in the absence or presence of 1.5 U/ml thrombin or 10 mg/ml lipopolysaccharide (LPS). Hcy alone had no effect on the expression of vascular cell adhesion molecule (VCAM)-1. However, Hcy enhanced thrombin- and LPS-mediated induction of VCAM-1 mRNA and protein levels. Consistent with these results, pretreatment of HUVEC with Hcy resulted in a two-fold increase in LSP-mediated induction of leukocyte adhesion. The latter effect was significantly inhibited by anti-VCAM-1 antibodies. Together, these findings suggest that Hcy sensitizes HUVEC to the effect of inflammatory mediators thrombin and LPS, at least in part through VCAM-1 expression and function.

Hypoxia-independent activation of HIF-1 by enterobacteriaceae and their siderophores

BACKGROUND & AIMS

Hypoxia inducible factor-1 (HIF-1) is the key transcriptional regulator during adaptation to hypoxia. Recent studies provide evidence for HIF-1 activation during bacterial infections. However, molecular details of how bacteria activate HIF-1 remain unclear. Here, we pursued the role of bacterial siderophores in HIF-1 activation during infection with Enterobacteriaceae.

METHODS

In vivo, HIF-1 activation and HIF-1-dependent gene induction in Peyer's patches were analyzed after orogastric infection with Yersinia enterocolitica. The course of an orogastric Y enterocolitica infection was determined using mice with a deletion of HIF-1alpha in the intestine. In vitro, the mechanism of HIF-1 activation was analyzed in infections with Y enterocolitica, Salmonella enterica subsp enterica, and Enterobacter aerogenes.

RESULTS

Infection of mice with Y enterocolitica led to functional activation of HIF-1 in Peyer's patches. Because mice with deletion of HIF-1alpha in the intestinal epithelium showed a significantly higher susceptibility to orogastric Y enterocolitica infections, bacterial HIF-1 activation appears to represent a host defense mechanism. Additional studies with Y enterocolitica, S enterica subsp enterica, or E aerogenes, and, moreover, application of their siderophores (yersiniabactin, salmochelin, aerobactin) caused a robust, dose-dependent HIF-1 response in human epithelia and endothelia, independent of cellular hypoxia. HIF-1 activation occurs most likely because of inhibition of prolylhydroxylase activity and is abolished upon infection with siderophore uptake deficient bacteria.

CONCLUSIONS

Taken together, this study reveals what we believe to be a previously unrecognized role of bacterial siderophores for hypoxia-independent activation of HIF-1 during infection with human pathogenic bacteria.

Combined anticoagulants ameliorate acute lung injury in sheep after burn and smoke inhalation

Burn and smoke inhalation-related multiple organ dysfunction is associated with a severe fall in the plasma concentration of antithrombin. Therefore the aim of the present study was to test the hypothesis that intravenous administration of recombinant human antithrombin in combination with aerosolized heparin will ameliorate acute lung injury in sheep exposed to cutaneous burn and smoke inhalation. Sheep were prepared operatively for study and, 7 days post-surgery, sheep were given a cutaneous burn (40% of total body surface area, third-degree burn) and insufflated with cotton smoke (48 breaths, <40 degrees C) under halothane anaesthesia. After injury, sheep were placed on a ventilator and resuscitated with Ringer's lactate solution. The animals were divided into three groups: sham group (non-injured and non-treated; n=6), saline group (injured and received saline; n=6) and rhAT.iv.+Hep group [injured and treated with rhAT (recombinant human antithrombin) and heparin; n=6]. In the rhAT.iv.+Hep group, rhAT was infused continuously for 48 h starting 1 h post-injury with a dose of 0.34 mg.h(-1).kg(-1) of body weight and heparin (10000 units) was aerosolized every 4 h starting at 1 h post-injury. The experiment lasted 48 h. Haemodynamics were stable in sham group, whereas the saline-treated sheep developed multiple signs of acute lung injury, including decreased pulmonary gas exchange, increased inspiratory pressures, extensive airway obstruction and increased pulmonary oedema. These pathological changes were associated with a severe fall in plasma antithrombin concentration, lung tissue accumulation of leucocytes and excessive production of NO. Treatment of injured sheep with anticoagulants attenuated all of the pulmonary pathophysiology observed. In conclusion, the results provide definitive evidence that anticoagulant therapy may be a novel and effective treatment tool in the management of burn patients with concomitant smoke inhalation injury.

Activated protein C modulates chemokine response and tissue injury in experimental sepsis

The protein C (PC) pathway plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality. We have explored the role of PC suppression in modulating early inflammatory events in a model of polymicrobial sepsis. We show that increased levels of organ damage and dysfunction are associated with decreased levels of endogenous PC. Notably, animals with low PC had correspondingly high levels of pulmonary iNOS expression, which correlated with chemokines KC/Gro and MIP2, previously shown to predict outcome in this model. Treatment with activated protein C (aPC) not only reduced the pathology score, leukocyte infiltration and markers of organ dysfunction, but also suppressed the induction of iNOS, and the chemokine response (including KC/Gro, MIP2, IP-10, RANTES, GCP-2 and lymphotactin), and increased apoA1. aPC treatment also suppressed the induction of VEGF, a marker recently suggested to play a pathophysiological role in sepsis. These data demonstrate a clear link between low protein C and degree of organ damage and dysfunction in sepsis, as well as the early reversal with aPC treatment. Moreover, our data show a direct role of aPC in broadly modulating monocyte and T-cell chemokines following systemic inflammatory response.

Animal models of human pneumonia

Pneumonia is a medical and public health priority, and advances against this disease will require improved knowledge of biological mechanisms. Human pneumonia is modeled with experimental infections of animals, most frequently mice. Mouse models are leading to important discoveries relevant to pneumonia, but their limitations must be carefully considered. Several approaches to establishing pneumonia in mice have been developed, and each has specific strengths and weaknesses. Similarly, procedures for characterizing microbial and host responses to infection have unique advantages and disadvantages. Mice are not small humans, and the applicability of results from murine models to human disease depends on understanding the similarities and differences between species. Additional considerations such as mouse strain, microbe strain, and prior mouse-microbe interactions also influence the design and interpretation of experiments. Results from studies of pneumonia in animals, combined with complementary basic and translational studies, are elucidating mechanisms responsible for susceptibility to and pathophysiology of lung infection.

Hypoxia inducible factor (HIF)-1 coordinates induction of Toll-like receptors TLR2 and TLR6 during hypoxia

Background

During acute infection and inflammation, dramatic shifts in tissue metabolism are typical, thereby resulting in profound tissue hypoxia. Therefore, we pursued the hypothesis, that tissue hypoxia may influence innate immune responses by transcriptional modulation of Toll-like receptor (TLRs) expression and function.

Methodology/Principal Findings

We gained first insight from transcriptional profiling of murine dendritic cells exposed to hypoxia (2% oxygen for 24 h). While transcript levels of other TLRs remained unchanged, we found a robust induction of TLR2 (2.36±0.7-fold; P<0.05) and TLR6 (3.46±1.56-fold; P<0.05). Additional studies in different cells types and cell-lines including human dendritic cells, monocytic cells (MM6), endothelia (HMEC-1) or intestinal epithelia (Caco-2) confirmed TLR2 and TLR6 induction of transcript, protein and function during hypoxia. Furthermore, analysis of the putative TLR2 and TLR6 promoters revealed previously unrecognized binding sites for HIF-1, which were shown by chromatin immunoprecipitation to bind the pivotal hypoxia-regulating transcription factor HIF-1alpha. Studies using loss and gain of function of HIF-1 confirmed a critical role of HIF-1alpha in coordinating TLR2 and TLR6 induction. Moreover, studies of murine hypoxia (8% oxygen over 6 h) showed TLR2 and TLR 6 induction in mucosal organs in vivo. In contrast, hypoxia induction of TLR2 and TLR6 was abolished in conditional HIF-1α mutant mice.

Conclusions/Significance

Taking together, these studies reveal coordinated induction of TLR2 and TLR6 during hypoxia and suggest tissue hypoxia in transcriptional adaptation of innate immune responses during acute infection or inflammation.