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

Calcineurin-NFAT activation and DSCR-1 auto-inhibitory loop: how is homoeostasis regulated?

Calcineurin-nuclear factor of activated T cells (NFAT) signalling plays a critical role not only in the immune and nervous systems, but also in cardiovascular development and pathological endothelial cell activation during angiogenesis or inflammation. Studies in NFAT-null mice demonstrated that there is high redundancy between functions of the different NFAT family members. Deletion of only one NFAT causes mild phenotypes, but compound deletions of multiple NFAT family members leads to severe abnormalities in multiple organ systems. Genome-wide transcription analysis revealed that many NFAT target genes are related to cell growth and inflammation, whereas the gene most strongly induced by NFAT in endothelial cells is an auto-inhibitory molecule, Down syndrome critical region (DSCR)-1. The NFAT-DSCR-1 signalling axis may vary depending on the cell-type or signal dosage level under the microenvironment. In the endothelium, stable expression of the DSCR-1 short isoform attenuates septic inflammatory shock, tumour growth and tumour metastasis to lung. Moreover, dysfunction of DSCR-1 and the NFAT priming kinase, DYRK1A, prevents NFAT nuclear occupancy. This change in NFAT nuclear localization is responsible for many of the features of Down syndrome. Thus, fine-tuning of the NFAT-DSCR-1 negative feedback loop may enable therapeutic manipulation in vasculopathic diseases.

Portal cytokine response and metabolic markers in the early stages of abdominal sepsis in pigs

BACKGROUND

The portal vein could play a major role in disseminating the local inflammation of acute bacterial peritonitis since it is responsible for the venous drainage of the gastrointestinal tract. We hypothesized that after peritoneal exposure to Escherichia coli, a gradient between the portal and systemic levels of cytokines would be expected.

METHODS

Acute peritonitis was induced by depositing 200 ml of broth with live E. coli in the peritoneal cavity of the animals in the B-group (n = 7). They were then observed for 4 h and compared with a control group (C-group, n = 7). Tumour necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-10 and vascular endothelial growth factor were measured repeatedly in the portal vein and the femoral artery. Portal vein metabolic markers (microdialysis), haemodynamics, biochemistry, plasma volume (PV), fluid shifts and total tissue water content were recorded or calculated.

RESULTS

The intervention led to PV contraction, increased fluid extravasation, increased pulmonary vascular resistance and reduced urinary output in the B-group as compared with the C-group. The levels of glucose in the portal vein were reduced in both study groups with no between-group differences. The levels of TNF-α and IL-6 increased markedly in the portal vein as well as in the systemic circulation of the B-group, but no gradient was seen between them. The corresponding levels of TNF-α and IL-6 remained low and stable in the C-group.

CONCLUSION

The portal vein appears to play a minor role in supplying TNF-α and IL-6 to the systemic circulation after peritoneal exposure to a substantial dose of E. coli.

Augmentation of LPS-induced vascular endothelial cell growth factor production in macrophages by transforming growth factor-β1

The effect of LPS on the production of vascular endothelial growth factor (VEGF) was examined using RAW 264.7 macrophage cells. LPS induced VEGF production in RAW 264.7 cells and mouse peritoneal cells. LPS induced VEGF production via the expression of hypoxia inducible factor-1α and LPS-induced VEGF production was dependent on the activation of p38 MAPK and NF-κB activation· Transforming growth factor (TGF)-β1 augmented LPS-induced VEGF production, although TGF-β1 alone did not induce VEGF production. The augmentation of LPS-induced VEGF production by TGF-β1 was inhibited by a p38 MAPK inhibitor and was correlated with the phosphorylation of Smad3. The enhancing effect of TGF-β1 on LPS-induced VEGF production was observed in vivo in the skin lesions of mice receiving a subcutaneous injection of LPS. Taken together, it is suggested that LPS induced the VEGF production in macrophages and that it was augmented by TGF-β1 in vitro and in vivo.

Placental growth factor, pregnancy-associated plasma protein-A, soluble receptor for advanced glycation end products, extracellular newly identified receptor for receptor for advanced glycation end products binding protein and high mobility group box 1 levels in patients with acute kidney injury: a cross sectional study

BACKGROUND

Placental growth factor (PlGF), pregnancy-associated plasma protein-A (PAPP-A), soluble receptor for advanced glycation end products (sRAGE), extracellular newly identified receptor for RAGE binding protein (EN-RAGE) and high mobility group box 1 (HMGB-1) are novel biomarkers in chronic kidney disease (CKD). However, their clinical significance in acute kidney injury (AKI) is unknown. The aim of this cross-sectional study was to determine whether selected biomarkers are changed in AKI patients.

METHODS

Serum PlGF, PAPP-A, sRAGE, EN-RAGE and HMGB-1 levels were assessed in 40 patients with AKI, 42 CKD 5 patients, 31 haemodialysis patients (HD) and 39 age-matched healthy controls.

RESULTS

PAPP-A was elevated in AKI (20.6 ± 16.9 mIU/L) compared with controls (9.1 ± 2.3 mIU/L, p < 0.001). PlGF was not increased in AKI (11.7 ± 7.4 pg/mL) versus controls (8.5 ± 2.4 pg/mL, n.s.), as well as sRAGE was not elevated in AKI (2400 ± 1400 pg/mL) compared with controls (1760 ± 730 pg/mL, n.s), but was lower compared with CKD 5 (3200 ± 1500 pg/mL, p < 0.05); EN-RAGE was elevated in AKI 480 ± 450 ng/mL in comparison with controls (60 ± 62 ng/mL), CKD 5 (190 ± 120 ng/mL), and HD (120 ± 100 ng/mL), all p < 0.001. Similarly, HMGB-1 was increased in AKI (5.8 ± 7.5 ng/mL) versus controls (1.7 ± 1.4 ng/mL), CKD 5 (3.2 ± 3.1 ng/mL) and HD (2.5 ± 2.1 ng/mL), all p < 0.001.In AKI group, in multivariate regression analysis: PAPP-A levels were associated with transferrin (p <0.001), negatively with albumin (p < 0.01) and prealbumin (p < 0.05); PlGF levels were associated with C--reactive protein (p < 0.001). EN-RAGE levels were associated with ferritin (p < 0.01) and orosomucoid (p = 0.02), and HMGB-1 levels with leukocyte count (p < 0.01) and negatively with proteinuria (p = 0.02).

CONCLUSIONS

In AKI patients, PAPP-A, EN-RAGE and HMGB1 are elevated, but sRAGE and PlGF are not increased. Whereas PAPP-A correlates with markers of nutrition; PlGF, EN-RAGE and HMGB-1 are related to inflammatory parameters.

Biomarkers of endothelial cell activation in early sepsis

PURPOSE

The objective of this study was to investigate the association of endothelial-related markers with organ dysfunction and in-hospital mortality to validate our earlier findings in a multicenter study. We hypothesize that (i) endothelial biomarkers will be associated with organ dysfunction and mortality in sepsis and that (ii) soluble fms-like tyrosine kinase 1 (sFlt-1) holds promise as a novel prognostic marker in sepsis.

METHODS

This was a prospective, multicenter, observational study of a convenience sample of emergency department (ED) patients with a suspected infection presenting to one of four urban, academic medical center EDs between January 2009 and January 2010. We collected plasma while the patients were in the ED and subsequently assayed endothelial-related biomarkers, namely, sFlt-1, soluble E-selectin, soluble intercellular adhesion molecule 1, soluble vascular cell adhesion molecule 1, and plasminogen activator inhibitor 1 (PAI-1). Outcomes were organ dysfunction and in-hospital mortality.

RESULTS

We enrolled a total of 166 patients: 63 with sepsis (38%), 61 with severe sepsis (37%), and 42 with septic shock (25%). All endothelial biomarkers were significantly associated with sepsis severity, P < 0.002. We found a significant intercorrelation between all biomarkers, strongest between sFlt-1 and PAI-1 (r = 0.61, P < 0.001) and PAI-1 and soluble E-selectin and soluble intercellular adhesion molecule 1 (r = 0.49, P < 0.001). Among the endothelial biomarkers, sFlt-1 had the strongest association with Sequential Organ Failure Assessment score (r = 0.58, P < 0.001). Soluble fms-like tyrosine kinase 1 and PAI-1 had the highest area under the operating receiver characteristic curve for mortality of 0.87.

CONCLUSIONS

This multicenter validation study confirms that markers of endothelial activation are associated with sepsis severity, organ dysfunction, and mortality in sepsis. This supports the hypothesis that the endothelium plays a central role in the pathophysiology of sepsis and may serve as a more accurate prediction tool and a target for therapies aimed at ameliorating endothelial cell dysfunction. In addition, sFLT-1 holds promise as a novel sepsis severity biomarker.

Decreased expression of serum and microvascular vascular endothelial growth factor receptor-2 in meningococcal sepsis*

OBJECTIVES

To determine the skin microvessel expression of vascular endothelial growth factor receptor 2 and serum-soluble vascular endothelial growth factor receptor 2 levels in children with meningococcal sepsis.

DESIGN

Observational study.

SETTING

Two tertiary academic children hospital PICUs.

PATIENTS

Children with meningococcal sepsis.

INTERVENTION

Skin biopsy and blood sample collection.

MEASUREMENTS AND MAIN RESULTS

Determination of skin microvessel vascular endothelial growth factor receptor 2 expression in skin biopsies by immunohistochemistry and measurement of serum-soluble vascular endothelial growth factor receptor 2 by enzyme-linked immunosorbent assay. Percentage of vascular endothelial growth factor receptor 2-positive skin microvessels and the staining intensity were significantly lower in children with meningococcal sepsis (n = 10) compared to controls (7.6% ± 8.8% vs 44.6% ± 39.2%; p = 0.009 and 0.7% ± 0.7% vs 1.7% ± 1.1%; p = 0.033, respectively). In addition, circulating serum levels of soluble vascular endothelial growth factor receptor 2 were decreased in sepsis (8,148 ± 1,140 pg/mL vs 13,414 ± 2,692 pg/mL; p < 0.001). Serum-soluble vascular endothelial growth factor receptor 2 levels (n = 28) were inversely correlated with Pediatric Risk of Mortality III score (r = -0.43; p = 0.023) and more decreased in nonsurvivors compared to survivors (5,640 ± 1,940 pg/mL vs 7,378 ± 2,336 pg/mL; p = 0.037).

CONCLUSIONS

Microvascular expression of vascular endothelial growth factor receptor 2 and serum-soluble vascular endothelial growth factor receptor 2 levels are decreased in children with sepsis. Serum-soluble vascular endothelial growth factor receptor 2 levels are inversely correlated with disease severity indicated by Pediatric Risk of Mortality III score and survival. Decreased vascular endothelial growth factor receptor 2 expression may hinder natural recovery from sepsis-associated microvascular injury and the effectiveness of therapeutic strategies targeting vascular endothelial growth factor-vascular endothelial growth factor receptor 2 signaling in sepsis patients.

Influence of endotoxin-mediated retinal inflammation on phenotype of diabetic retinopathy in Ins2 Akita mice

AIMS

To evaluate the impact of systemic exposure to bacterial lipopolysaccharide (LPS) on a rodent model of background diabetic retinopathy.

METHODS

Toll-like receptor 4 (TLR4)-mediated systemic inflammation was induced in Ins2(Akita) heterozygotes and age-matched C57BL6/J-Ins2(+) littermates by single or repeated intraperitoneal injections of the TLR4 ligand LPS (9 µg/g body weight). 24 hours after a single injection in 7-week-old mice retinal Il1b, Tnfa and Vegf transcripts were measured with real-time PCR. Vascular endothelial growth factor (VEGF) protein levels were evaluated with bead-based immunoassay. Leukostasis and endothelial injury were assessed in retinal wholemounts following perfusion with rhodamine or FITC conjugated concanavalin A to label leukocytes and propidium iodide to label dead or injured cells. In mice which had received three fortnightly injections between 10 and 16 weeks of age, retinal thicknesses and vascular structure were evaluated at 17-18 weeks of age using optical coherence tomography (OCT) and fluorescein angiography. Retinal architecture was assesed using resin-based histology.

RESULTS

Compared with normoglycaemic controls, systemic LPS exposure in Ins2(Akita) mice was associated with a 3.5-fold increase in endothelial cell injury and attenuated leukostasis in the retinal vasculature. Hyperglycaemia or acute LPS inflammation did not increase retinal VEGF content. Thinning (10-13 µm) of posterior retina was detected with OCT 2 weeks after repeated exposure to LPS in Ins2(Akita) mice but not in normoglycaemic controls. Capillary networks and retinal morphology were unaffected by recurrent LPS inflammation in Ins2(Akita) and control mice.

CONCLUSIONS

In hyperglycaemic mice, exposure to systemic LPS was associated with two hallmark pathologies of early background diabetic retinopathy, namely, the injury of capillary endothelium and in vivo thinning of the retina.

TNF-mediated damage to glomerular endothelium is an important determinant of acute kidney injury in sepsis

Severe sepsis is often accompanied by acute kidney injury (AKI) and albuminuria. Here we studied whether the AKI and albuminuria associated with lipopolysaccharide (LPS) treatment in mice reflects impairment of the glomerular endothelium with its associated endothelial surface layer. LPS treatment decreased the abundance of endothelial surface layer heparan sulfate proteoglycans and sialic acid, and led to albuminuria likely reflecting altered glomerular filtration permselectivity. LPS treatment decreased the glomerular filtration rate (GFR), while also causing significant ultrastructural alterations in the glomerular endothelium. The density of glomerular endothelial cell fenestrae was 5-fold lower, whereas the average fenestrae diameter was 3-fold higher in LPS-treated than in control mice. The effects of LPS on the glomerular endothelial surface layer, endothelial cell fenestrae, GFR, and albuminuria were diminished in TNF receptor 1 (TNFR1) knockout mice, suggesting that these LPS effects are mediated by TNF-α activation of TNFR1. Indeed, intravenous administration of TNF decreased GFR and led to loss of glomerular endothelial cell fenestrae, increased fenestrae diameter, and damage to the glomerular endothelial surface layer. LPS treatment decreased kidney expression of vascular endothelial growth factor (VEGF). Thus, our findings confirm the important role of glomerular endothelial injury, possibly by a decreased VEGF level, in the development and progression of AKI and albuminuria in the LPS model of sepsis in the mouse.

The dynamics of angiogenic factors and their soluble receptors in relation to organ dysfunction in disseminated intravascular coagulation associated with sepsis

We prospectively studied (1) the relationships between angiogenic factors, their soluble receptors and organ dysfunction and (2) the effects of disseminated intravascular coagulation (DIC)-induced platelet consumption, thrombin generation, and tissue hypoxia on the expression of the factors and receptors. Fifty patients with sepsis were classified into two subgroups: 37 patients with DIC and 13 patients without DIC. DIC patients showed higher Sequential Organ Failure Assessment (SOFA) scores, the prevalence of multiple organ dysfunction syndrome (MODS) and more increased soluble fibrin and lactate levels. We observed lower levels of vascular endothelial growth factor (VEGF), soluble VEGF receptor 2 (sVEGFR2), angiopoietin 1 (Ang1) and Ang1/Ang2, and higher sVEGFR1 and Ang2 levels in DIC patients, but not significant differences in soluble Tie2 expression during the study period. The levels of VEGF, sVEGFR1, and Ang2 in DIC patients correlated with the SOFA scores. Clear differences were observed in the levels of Ang2 in the DIC patients between survivors and nonsurvivors and between those with and without MODS. The area under receiver operating characteristic curves for predicting death and MODS by Ang2 were 0.710 and 0.784, respectively. The VEGF levels showed a marked correlation with the platelet counts. Soluble fibrin and lactate levels independently predicted increases in the levels of VEGF, sVEGFR1, and Ang2 in DIC patients. In conclusion, VEGF, sVEGFR1, Ang2, and Ang1/Ang2, especially Ang2, may have roles in the development of MODS in sepsis associated with DIC, and VEGF, sVEGFR1, and Ang2 serum levels correlated with the extent of DIC-induced platelet consumption, thrombin generation, and blood lactate levels.

Kupffer cells potentiate liver sinusoidal endothelial cell injury in sepsis by ligating programmed cell death ligand-1

PD-1 and PD-L1 have been reported to provide peripheral tolerance by inhibiting TCR-mediated activation. We have reported that PD-L1-/- animals are protected from sepsis-induced mortality and immune suppression. Whereas studies indicate that LSECs normally express PD-L1, which is also thought to maintain local immune liver tolerance by ligating the receptor PD-1 on T lymphocytes, the role of PD-L1 in the septic liver remains unknown. Thus, we hypothesized initially that PD-L1 expression on LSECs protects them from sepsis-induced injury. We noted that the increased vascular permeability and pSTAT3 protein expression in whole liver from septic animals were attenuated in the absence of PD-L1. Isolated LSECs taken from septic animals, which exhibited increased cell death, declining cell numbers, reduced cellular proliferation, and VEGFR2 expression (an angiogenesis marker), also showed improved cell numbers, proliferation, and percent VEGFR2(+) levels in the absence of PD-L1. We also observed that sepsis induced an increase of liver F4/80(+)PD-1(+)-expressing KCs and increased PD-L1 expression on LSECs. Interestingly, PD-L1 expression levels on LSECs decreased when PD-1(+)-expressing KCs were depleted with clodronate liposomes. Contrary to our original hypothesis, we document here that increased interactions between PD-1(+) KCs and PD-L1(+) LSECs appear to lead to the decline of normal endothelial function-essential to sustain vascular integrity and prevent ALF. Importantly, we uncover an underappreciated pathological aspect of PD-1:PD-L1 ligation during inflammation that is independent of its normal, immune-suppressive activity.

Early biomarker activity in severe sepsis and septic shock and a contemporary review of immunotherapy trials: not a time to give up, but to give it earlier

Improving time to diagnosis and intervention has positively impacted outcomes in acute myocardial infarction, stroke, and trauma through elucidating the early pathogenesis of those diseases. This insight may partly explain the futility of time-insensitive immunotherapy trials for severe sepsis and septic shock. The aim of this study was to examine the early natural history of circulatory biomarker activity in sepsis, relative to previous animal and human outcome trials. We conducted a literature search using PubMed, MEDLINE, and Google Scholar to identify outcome trials targeting biomarkers with emphasis on the timing of therapy. These findings were compared with the biomarker activity observed over the first 72 h of hospital presentation in a cohort of severe sepsis and septic shock patients. Biomarker levels in animal and human research models are elevated within 30 min after exposure to an inflammatory septic stimulus. Consistent with these findings, the biomarker cascade is activated at the most proximal point of hospital presentation in our patient cohort. These circulatory biomarkers overlap; some have bimodal patterns and generally peak between 3 and 36 h while diminishing over the subsequent 72 h of observation. When this is taken into account, prior outcome immunotherapy trials have generally enrolled patients after peak circulatory biomarker concentrations. In previous immunotherapy sepsis trials, intervention was delayed after the optimal window of peak biomarker activity. As a result, future studies need to recalibrate the timing of enrollment and administration of immunotherapy agents that still may hold great promise for this deadly disease.

Peptides modeled on the RGG domain of AUF1/hnRNP-D regulate 3' UTR-dependent gene expression

Messenger RNA binding proteins control post-transcriptional gene expression of targeted mRNAs. The RGG (arginine-glycine-glycine) domain of the AUF1/hnRNP-D mRNA binding protein is a regulatory region that is essential for protein function. The AUF1-RGG peptide, modeled on the RGG domain of AUF1, represses expression of the macrophage cytokine, VEGF. This report expands studies on the AUF1-RGG peptide and evaluates the role of post-translational modifications of the AUF1 protein. Results show that a minimal 31-amino acid AUF1-RGG peptide that lacks poly-glutamine and nuclear localization motifs retains suppressive activity on a VEGF-3'UTR reporter. Arginine residues in RGG motifs may be methylated with resulting changes in protein function. Mass spectroscopy analysis was performed on AUF1 expressed in RAW-264.7 cells. In resting cells, arginines in the first and second RGG motifs are monomethylated. Following activation with lipopolysaccharide, the arginines are dimethylated. To evaluate if the arginine residues are essential for AUF1-RGG activity, the methylatable arginines in the AUF1-3RGG peptide were mutated to lysine or alanine. The R→K and R→A mutants lack activity. We also demonstrate that PI3K/AKT inhibitors reduce VEGF gene expression. Although immunoscreening of AUF1 suggests that LPS and PI3K inhibitors alter the phosphorylation status of AUF1-p37, mass spectroscopy results show that the p37 AUF1 isoform is not phosphorylated with or without lipopolysaccharide stimulation. In summary, arginines in the RGG domain of AUF1 are methylated, and AUF1-RGG peptides may be novel reagents that reduce macrophage activation in inflammation.

Anti-vascular endothelial growth factor antibody attenuates inflammation and decreases mortality in an experimental model of severe sepsis

Introduction

Severe sepsis is associated with an unacceptably high rate of mortality. Recent studies revealed elevated levels of vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, in patients with sepsis. There was also an association between VEGF levels and sepsis severity. Here we investigate the effects of an anti-VEGF antibody (Bevacizumab, Bev) in an experimental model of sepsis.

Methods

Human umbilical vein endothelial cells (HUVECs), murine cecal ligation and puncture (CLP), and endotoxemia models of sepsis were used. HUVECs were treated with lipopolysaccharide (LPS) and/or Bev, harvested and cytokine mRNA levels determined using a semi-quantitative reverse transcription-polymerase chain reaction assay. The levels of inflammatory cytokine were also determined in HUVECs supernatants. In addition, the effects of Bev on mortality in the CLP and endotoxemia models of sepsis were evaluated.

Results

Treatment with Bev and LPS significantly decreased the expression and the level of inflammatory cytokines in HUVECs relative to LPS alone. In CLP and endotoxemia models, survival benefits were evident in mice given 0.1 mg/kg of Bev relative to the CLP or LPS alone (P <0.001 and P = 0.028, respectively), and in 6 h post-treated mice relative to the CLP alone for the effect of different time of Bev (P = 0.033). In addition, Bev treatment inhibited LPS-induced vascular leak in the lung, spleen and kidney in the murine endotoxemia model (P <0.05).

Conclusions

Anti-VEGF antibody may be a promising therapeutic agent due to its beneficial effects on the survival of sepsis by decreasing inflammatory responses and endothelial permeability.

Sepsis-induced leukocyte adhesion in the pulmonary microvasculature in vivo is mediated by CD11a and CD11b

Leukocyte accumulation is a rate-limiting step in inflammatory lung injury. The aim of this study was to define the role of CD11a/CD18 and CD11b/CD18 in sepsis-induced leukocyte rolling and adhesion in lung arterioles, capillaries and venules in male C57BL/6 mice using intravital fluorescence microscopy. Cecal ligation and puncture (CLP) markedly increased leukocyte rolling in arterioles and venules but not in capillaries in the lung. Immunoneutralization of CD11a, but not CD11b, decreased CLP-provoked leukocyte rolling in lung arterioles. Inhibition of CD11a or CD11b abolished CLP-induced arteriolar and venular leukocyte adhesion. Immunoneutralization of CD11a and CD11b reduced sepsis-induced leukocyte sequestration in pulmonary capillaries. Moreover, blocking CD11a or CD11b function improved microvascular blood flow in the lung of CLP animals. Considered together, our novel findings show that CD11a and CD11b mediate leukocyte adhesion in both arterioles and venules as well as trapping in capillaries in the lung. In addition, our data demonstrate that CD11a but not CD11b supports leukocyte rolling in pulmonary arterioles. Thus, these findings elucidate the molecular mechanisms behind leukocyte-endothelium interactions in the lung during systemic inflammation.

Endoglin in amniotic fluid as a risk factor for the subsequent development of bronchopulmonary dysplasia

OBJECTIVE

Cross-talk between inflammation and angiogenesis pathways has been recently reported. The objectives of this study were to: (i) examine whether amniotic fluid (AF) concentrations of soluble endoglin (sEng), a protein with anti-angiogenic properties, change during pregnancy, parturition, or intra-amniotic infection and/or inflammation (IAI); (ii) determine whether an increase in sEng in the AF of patients with preterm labor (PTL) and preterm prelabor rupture of membranes (PROM) is associated with adverse neonatal outcomes; and (iii) investigate potential sources of sEng in AF.

STUDY DESIGN

A cross-sectional study was conducted to include patients in the following groups: (i) mid-trimester (n = 20); (ii) PTL with term delivery (n = 95); (iii) PTL leading to preterm delivery with (n = 40) and without IAI (n = 46); (iv) preterm PROM with (n = 37) and without IAI (n = 37); (v) term in labor (n = 48) and not in labor (n = 44). AF concentrations of sEng were determined by enzyme-linked immunosorbent assay. Chorioamniotic membranes, umbilical cord blood, and AF macrophages were examined for the expression of endoglin.

RESULTS

(i) Patients with IAI had a higher median AF concentration of sEng than those without IAI (P = 0.02 for PTL and 0.06 for preterm PROM); (ii) AF concentrations of sEng in the 3rd and 4th quartiles were associated with IAI (OR 2.5 and 7.9, respectively); (iii) an AF sEng concentration ≥779.5 pg/mL was associated with bronchopulmonary dysplasia (BPD) (OR 7.9); (iv) endoglin was co-localized with CD14+ macrophages in AF pellets of patients with IAI by immunofluorescence and flow cytometry; and (v) the concentration of sEng in the supernatant was significantly increased after the treatment of macrophages with endotoxin or TNF-α.

CONCLUSIONS

Soluble endoglin participates in the host response against IAI. Activated macrophages may be a source of sEng concentrations in the AF of patients with IAI. An increase of sEng in the AF is associated with BPD and adverse neonatal outcomes.

Using angiogenic factors and their soluble receptors to predict organ dysfunction in patients with disseminated intravascular coagulation associated with severe trauma

Introduction

Disseminated intravascular coagulation (DIC) is characterized by the concomitant activation of coagulofibrinolytic disorders and systemic inflammation associated with endothelial dysfunction-induced microvascular permeability. Angiogenic factors, including vascular endothelial growth factor (VEGF), angiopoietin (Ang), and their receptors, play crucial roles in angiogenesis and microvascular permeability. The aim of the study was to assess the relationship between angiogenic factors, their soluble receptors and organ dysfunction associated with DIC after severe trauma.

Materials and methods

A total of 57 patients with severe trauma were divided into two subgroups; 30 DIC patients and 27 non-DIC patients. The DIC was diagnosed based on the Japanese Association for Acute Medicine (JAAM) DIC and the International Society on Thrombosis and Haemostasis (ISTH) overt DIC criteria. The serum levels of angiogenic factors were measured at the time of admission (Day 1), Day 3 and Day 5. This study compared levels of these angiogenic factors between the two DIC groups, and evaluated their predictive value for organ dysfunction.

Results

DIC patients, especially those with ISTH DIC, showed higher Sequential Organ Failure Assessment (SOFA) scores and lactate levels. There were lower levels of VEGF, Ang1 and the soluble Tie2 in the ISTH DIC patients than the non-DIC patients. The levels of soluble VEGF receptor-1 (sVEGFR1), Ang2 and the Ang2/Ang1 ratio in the ISTH DIC patients were higher than in non-DIC patients. The relationship between the presence of massive transfusion and angiogenic factors indicated the same results. The levels of sVEGFR1, Ang2 and the Ang2/Ang1 ratio correlated with the SOFA scores. In particular, sVEGFR1 and Ang2 were independent predictors of an increase in the SOFA score. The lactate levels independently predicted increases in the levels of sVEGFR1 and Ang2. The decrease in the platelet counts also independently predicted the increase in Ang2 levels in DIC patients.

Conclusions

Angiogenic factors and their soluble receptors, particularly sVEGFR1 and Ang2, are considered to play pivotal roles in the development of organ dysfunction in DIC associated with severe trauma. DIC-induced tissue hypoxia and platelet consumption may play crucial roles in inducing sVEGFR1 and Ang2, and in determining the prognosis of the severity of organ dysfunction.

Angiogenic factors and their soluble receptors predict organ dysfunction and mortality in post-cardiac arrest syndrome

INTRODUCTION

Post-cardiac arrest syndrome (PCAS) often leads to multiple organ dysfunction syndrome (MODS) with a poor prognosis. Endothelial and leukocyte activation after whole-body ischemia/reperfusion following resuscitation from cardiac arrest is a critical step in endothelial injury and related organ damage. Angiogenic factors, including vascular endothelial growth factor (VEGF) and angiopoietin (Ang), and their receptors play crucial roles in endothelial growth, survival signals, pathological angiogenesis and microvascular permeability. The aim of this study was to confirm the efficacy of angiogenic factors and their soluble receptors in predicting organ dysfunction and mortality in patients with PCAS.

METHODS

A total of 52 resuscitated patients were divided into two subgroups: 23 survivors and 29 non-survivors. The serum levels of VEGF, soluble VEGF receptor (sVEGFR)1, sVEGFR2, Ang1, Ang2 and soluble Tie2 (sTie2) were measured at the time of admission (Day 1) and on Day 3 and Day 5. The ratio of Ang2 to Ang1 (Ang2/Ang1) was also calculated. This study compared the levels of angiogenic factors and their soluble receptors between survivors and non-survivors, and evaluated the predictive value of these factors for organ dysfunction and 28-day mortality.

RESULTS

The non-survivors demonstrated more severe degrees of organ dysfunction and a higher prevalence of MODS. Non-survivors showed significant increases in the Ang2 levels and the Ang2/Ang1 ratios compared to survivors. A stepwise logistic regression analysis demonstrated that the Ang2 levels or the Ang2/Ang1 ratios on Day 1 independently predicted the 28-day mortality. The receiver operating characteristic curves of the Ang2 levels, and the Ang2/Ang1 ratios on Day 1 were good predictors of 28-day mortality. The Ang2 levels also independently predicted increases in the Sequential Organ Failure Assessment (SOFA) scores.

CONCLUSIONS

We observed a marked imbalance between Ang1 and Ang2 in favor of Ang2 in PCAS patients, and the effect was more prominent in non-survivors. Angiogenic factors and their soluble receptors, particularly Ang2 and Ang2/Ang1, are considered to be valuable predictive biomarkers in the development of organ dysfunction and poor outcomes in PCAS patients.

Selective V(1a) agonism attenuates vascular dysfunction and fluid accumulation in ovine severe sepsis

Vasopressin analogs are used as a supplement to norepinephrine in septic shock. The isolated effects of vasopressin agonists on sepsis-induced vascular dysfunction, however, remain controversial. Because V(2)-receptor stimulation induces vasodilation and procoagulant effects, a higher V(1a)- versus V(2)-receptor selectivity might be advantageous. We therefore hypothesized that a sole, titrated infusion of the selective V(1a)-agonist Phe(2)-Orn(8)-Vasotocin (POV) is more effective than the mixed V(1a)-/V(2)-agonist AVP for the treatment of vascular and cardiopulmonary dysfunction in methicillin resistant staphylococcus aureus pneumonia-induced, ovine sepsis. After the onset of hemodynamic instability, awake, chronically instrumented, mechanically ventilated, and fluid resuscitated sheep were randomly assigned to receive continuous infusions of either POV, AVP, or saline solution (control; each n = 6). AVP and POV were titrated to maintain mean arterial pressure above baseline - 10 mmHg. When compared with that of control animals, AVP and POV reduced neutrophil migration (myeloperoxidase activity, alveolar neutrophils) and plasma levels of nitric oxide, resulting in higher mean arterial pressures and a reduced vascular leakage (net fluid balance, chest and abdominal fluid, pulmonary bloodless wet-to-dry-weight ratio, alveolar and septal edema). Notably, POV stabilized hemodynamics at lower doses than AVP. In addition, POV, but not AVP, reduced myocardial and pulmonary tissue concentrations of 3-nitrotyrosine, VEGF, and angiopoietin-2, thereby leading to an abolishment of cumulative fluid accumulation (POV, 9 ± 15 ml/kg vs. AVP, 110 ± 13 ml/kg vs. control, 213 ± 16 ml/kg; P < 0.001 each) and an attenuated cardiopulmonary dysfunction (left ventricular stroke work index, PaO(2)-to-FiO(2) ratio) versus control animals. Highly selective V(1a)-agonism appears to be superior to unselective vasopressin analogs for the treatment of sepsis-induced vascular dysfunction.

PlGF: a multitasking cytokine with disease-restricted activity

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that also comprises VEGF-A (VEGF), VEGF-B, VEGF-C, and VEGF-D. Unlike VEGF, PlGF is dispensable for development and health but has diverse nonredundant roles in tissue ischemia, malignancy, inflammation, and multiple other diseases. Genetic and pharmacological gain-of-function and loss-of-function studies have identified molecular mechanisms of this multitasking cytokine and characterized the therapeutic potential of delivering or blocking PlGF for various disorders.

Adiponectin diminishes organ-specific microvascular endothelial cell activation associated with sepsis

Experimental sepsis was induced in male C57BL/6j, adiponectin-deficient mice (ADPNKO), and wild-type littermates by i.p. injection of 16 mg/kg lipopolysaccharide or cecal ligation and puncture. Blood and tissue samples were harvested 24 h after model induction. Circulating adiponectin is reduced in mice with endotoxemic challenge and after cecal ligation and puncture compared with healthy control mice. Quantitative reverse transcriptase-polymerase chain reaction for adiponectin reveals a pattern of response that is both model- and organ-specific. When challenged with sepsis, adiponectin deficiency results in increased expression of endothelial adhesion and coagulation molecules in the lung, liver, and kidney as quantified by reverse transcriptase-polymerase chain reaction, increased macrophage and neutrophil infiltration by immunohistochemistry, and vascular leakage in the liver and kidney. Adiponectin-deficient mice have reduced survival following cecal ligation and puncture and increased blood levels of interleukin 6, soluble vascular endothelial growth factor receptor 1, and soluble endothelial adhesion molecules E-selectin and intercellular adhesion molecule 1. Finally, ADPNKO promoted end-organ injury in the liver and kidney, whereas the lungs were not affected. These data suggest a protective role of adiponectin in diminishing microvascular organ-specific endothelial cell activation during sepsis.

Clinical utility of biomarkers of endothelial activation in sepsis--a systematic review

INTRODUCTION

A strong biologic rationale exists for targeting markers of endothelial cell (EC) activation as clinically informative biomarkers to improve diagnosis, prognostic evaluation or risk-stratification of patients with sepsis.

METHODS

The objective was to review the literature on the use of markers of EC activation as prognostic biomarkers in sepsis. MEDLINE was searched for publications using the keyword 'sepsis' and any of the identified endothelial-derived biomarkers in any searchable field. All clinical studies evaluating markers reflecting activation of ECs were included. Studies evaluating other exogenous mediators of EC dysfunction and studies of patients with malaria and febrile neutropenia were excluded.

RESULTS

Sixty-one studies were identified that fulfilled the inclusion criteria. Overall, published studies report positive correlations between multiple EC-derived molecules and the diagnosis of sepsis, supporting the critical role of EC activation in sepsis. Multiple studies also reported positive associations for mortality and severity of illness, although these results were less consistent than for the presence of sepsis. Very few studies, however, reported thresholds or receiver operating characteristics that would establish these molecules as clinically-relevant biomarkers in sepsis.

CONCLUSIONS

Multiple endothelial-derived molecules are positively correlated with the presence of sepsis in humans, and variably correlated to other clinically-important outcomes. The clinical utility of these biomarkers is limited by a lack of assay standardization, unknown receiver operating characteristics and lack of validation. Additional large-scale prospective clinical trials will be required to determine the clinical utility of biomarkers of endothelial activation in the management of patients with sepsis.

Endothelial cell activation in emergency department patients with sepsis-related and non-sepsis-related hypotension

Previous studies found increased circulating levels of biomarkers related to endothelial cell activation in patients with sepsis, particularly in the most severe sepsis stages of sepsis shock. It remains unclear, however, whether this activation is mainly driven by sepsis-specific mechanisms or occurs as a generalized inflammatory response. The objective of this analysis was to compare patterns of biomarkers of endothelial cell activation in patients with hypotension due to sepsis and nonsepsis etiologies. This is a secondary analysis of a prospective, observational cohort study including emergency department patients older than17 years with an episode of hypotension defined as any systolic blood pressure measurement less than 100 mmHg. Etiology of hypotension episodes was classified as sepsis or nonsepsis (eg, cardiac or hemorrhagic). Endothelial activation biomarkers of cell adhesion (E-selectin, vascular cell adhesion molecule 1 [VCAM-1], and intercellular adhesion molecule 1 [ICAM-1]), coagulation (plasminogen activator inhibitor 1 [PAI-1]), and vascular endothelial growth factor (VEGF) signaling (VEGF, soluble fms-like tyrosine kinase 1 [sFLT-1]) were assayed. A total of 161 patients were analyzed. Hypotension was classified as sepsis (n = 69), nonsepsis (cardiac [n = 35], hemorrhagic [n = 12]), or indeterminate (n = 45). With the exception of PAI-1, median plasma levels of all endothelial markers were significantly higher in patients with sepsis compared with nonsepsis etiology (P < 0.05 for all comparisons). Logistic regression analysis, adjusted for age, sex, mean blood pressure level, and mortality, confirmed a significant association of E-selectin (odds ratio [OR], 3.7; 95% confidence interval [CI], 1.7-7.8, P < 0.001) and sFLT-1 (OR, 2.0; CI, 1.1-3.8; P < 0.03) with sepsis etiology. Biomarkers VCAM-1 (OR, 2.0; CI, 0.88-4.4; P = 0.1), VEGF (OR, 1.5; CI, 0.98-2.2; P = 0.06), ICAM-1 (OR, 1.5; CI, 0.9-2.6; P = 0.2), and PAI-1 (OR, 1.4; CI, 0.8-2.3; P = 0.2) did not reach statistical significance. This study found a sepsis-specific activation of endothelium activation markers, particularly E-selectin and sFLT-1, in emergency department patients with hypotension.

Chronic kidney disease worsens sepsis and sepsis-induced acute kidney injury by releasing High Mobility Group Box Protein-1

We have shown that folate-induced kidney dysfunction and interstitial fibrosis predisposes mice to sepsis mortality. Agents that increase survival in normal septic mice were ineffective in a two-stage kidney disease model. Here we used the 5/6 nephrectomy mouse model of progressive chronic kidney disease (CKD) to study how CKD affects acute kidney injury (AKI) induced by sepsis. We induced sepsis using cecal ligation and puncture and found that the presence of CKD intensified the severity of kidney and liver injury, cytokine release, and splenic apoptosis. Accumulation of High Mobility Group Box Protein-1 (HMGB1; a late proinflammatory cytokine released from apoptotic cells), vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, interleukin (IL)-6, or IL-10 was increased in CKD or sepsis alone and to a greater extent in CKD-sepsis. Only part of the increase was explained by decreased renal clearance. Surprisingly, we found splenic apoptosis in CKD, even in the absence of sepsis. Although VEGF neutralization with soluble fms-like tyrosine kinase 1 (sFLT-1) (a soluble VEGF receptor) effectively treated sepsis, it was ineffective against CKD-sepsis. A single dose of HMGB1-neutralizing antiserum administered 6 h after sepsis alone was ineffective; however, CKD-sepsis was attenuated by anti-HMGB1. Splenectomy transiently decreased circulating HMGB1 levels, reversing the effectiveness of anti-HMGB1 treatment on CKD-sepsis. Thus, progressive CKD increases the severity of sepsis, in part, by reducing the renal clearance of several cytokines. CKD-induced splenic apoptosis and HMGB1 release could be important common mediators for both CKD and sepsis.

Vascular Pathology as a Potential Therapeutic Target in SCI

Acute traumatic spinal cord injury (SCI) is characterized by a progressive secondary degeneration which exacerbates the loss of penumbral tissue and neurological function. Here, we first provide an overview of the known pathophysiological mechanisms involving injured microvasculature and molecular regulators that contribute to the loss and dysfunction of existing and new blood vessels. We also highlight the differences between traumatic and ischemic injuries which may yield clues as to the more devastating nature of traumatic injuries, possibly involving toxicity associated with hemorrhage. We also discuss known species differences with implications for choosing models, their relevance and utility to translate new treatments towards the clinic. Throughout this review, we highlight the potential opportunities and proof-of-concept experimental studies for targeting therapies to endothelial cell-specific responses. Lastly, we comment on the need for vascular mechanisms to be included in drug development and non-invasive diagnostics such as serum and cerebrospinal fluid biomarkers and imaging of spinal cord pathology.

Biomarkers of endothelial dysfunction: can they help us deciphering systemic inflammation and sepsis?

The endothelial integrity, as mechanical barrier against microorganisms and as natural "anticoagulant", is crucial for physiologic organ function. Systemic activation of the endothelium upon inflammation, sepsis, and septic shock is always ending in blood-tissue barrier disruption. With increasing dysfunction, uncontrolled clotting activation, capillary microthrombi formation, tissue edema, local hypoxia, and ischemia are initiated. This in turn enhances a vicious circle leading to multiple organ failure and death. Therefore, biomarkers reflecting this special compartment may help in the early detection of systemic inflammation and its complications. This review provides an overview of the most important endothelial biomarkers and their possible use in sepsis.

Dopamine inhibits pulmonary edema through the VEGF-VEGFR2 axis in a murine model of acute lung injury

The neurotransmitter dopamine and its dopamine receptor D2 (D2DR) agonists are known to inhibit vascular permeability factor/vascular endothelial growth factor (VEGF)-mediated angiogenesis and vascular permeability. Lung injury is a clinical syndrome associated with increased microvascular permeability. However, the effects of dopamine on pulmonary edema, a phenomenon critical to the pathophysiology of both acute and chronic lung injuries, have yet to be established. Therefore, we sought to determine the potential therapeutic effects of dopamine in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compared with sham-treated controls, pretreatment with dopamine (50 mg/kg body wt) ameliorated LPS-mediated edema formation and lowered myeloperoxidase activity, a measure of neutrophil infiltration. Moreover, dopamine significantly increased survival rates of LPS-treated mice, from 0-75%. Mechanistically, we found that dopamine acts through the VEGF-VEGFR2 axis to reduce pulmonary edema, as dopamine pretreatment in LPS-treated mice resulted in decreased serum VEGF, VEGFR2 phosphorylation, and endothelial nitric oxide synthase phosphorylation. We used D2DR knockout mice to confirm that dopamine acts through D2DR to block vascular permeability in our lung injury model. As expected, a D2DR agonist failed to reduce pulmonary edema in D2DR(-/-) mice. Taken together, our results suggest that dopamine acts through D2DR to inhibit pulmonary edema-associated vascular permeability, which is mediated through VEGF-VEGFR2 signaling and conveys protective effects in an ALI model.

ST2 and IL-33 in pregnancy and pre-eclampsia

Normal pregnancy is associated with a mild systemic inflammatory response and an immune bias towards type 2 cytokine production, whereas pre-eclampsia is characterized by a more intense inflammatory response, associated with endothelial dysfunction and a type 1 cytokine dominance. Interleukin (IL)-33 is a newly described member of the IL-1 family, which binds its receptor ST2L to induce type 2 cytokines. A soluble variant of ST2 (sST2) acts as a decoy receptor to regulate the activity of IL-33. In this study circulating IL-33 and sST2 were measured in each trimester of normal pregnancy and in women with pre-eclampsia. While IL-33 did not change throughout normal pregnancy, or between non-pregnant, normal pregnant or pre-eclamptic women, sST2 was significantly altered. sST2 was increased in the third trimester of normal pregnancy (p<0.001) and was further increased in pre-eclampsia (p<0.001). This increase was seen prior to the onset of disease (p<0.01). Pre-eclampsia is a disease caused by placental derived factors, and we show that IL-33 and ST2 can be detected in lysates from both normal and pre-eclampsia placentas. ST2, but not IL-33, was identified on the syncytiotrophoblast layer, whereas IL-33 was expressed on perivascular tissue. In an in vitro placental perfusion model, sST2 was secreted by the placenta into the 'maternal' eluate, and placental explants treated with pro-inflammatory cytokines or subjected to hypoxia/reperfusion injury release more sST2, suggesting the origin of at least some of the increased amounts of circulating sST2 in pre-eclamptic women is the placenta. These results suggest that sST2 may play a significant role in pregnancies complicated by pre-eclampsia and increased sST2 could contribute to the type 1 bias seen in this disorder.

A Src family kinase inhibitor improves survival in experimental acute liver failure associated with elevated cerebral and circulating vascular endothelial growth factor levels

BACKGROUND AND AIMS

Acute liver failure (ALF) is frequently complicated by cerebral oedema, systemic inflammation and multiorgan dysfunction. Vascular endothelial growth factor (VEGF) may stimulate liver regeneration but it can also be pro-inflammatory, activating endothelial cells and increasing permeability, actions mediated through Src kinase signalling. We therefore examined whether a Src inhibitor could have therapeutic potential in ALF.

METHODS

Murine ALF was induced with azoxymethane. Liver pathology was graded by a blinded examiner and apoptosis quantified by immunohistochemistry. Cerebral VEGF expression was imaged using VEGF-green fluorescent protein transgenic mice. Circulating and macrophage-secreted VEGF levels were measured. Experimental animals received a Src inhibitor or vehicle controls.

RESULTS

VEGF was undetectable in normal plasma but reached a mean of 835 pg/ml at grade III encephalopathy (P<0.001). Ammonia, lipopolysaccharide and interferon-gamma acted synergistically to enhance VEGF secretion by macrophages. Production of VEGF by cerebral cortical astrocytes increased with disease progression. Late treatment with inhibitors of Src or VEGF did not improve liver histology, encephalopathy or survival. However, early use of a Src kinase inhibitor significantly reduced hepatic injury, delayed encephalopathy and allowed 25% of mice to survive an otherwise lethal insult.

CONCLUSION

Systemic and cerebral VEGF levels are significantly elevated during experimental ALF and may be exacerbated by hyperammonemia and macrophage activation. Early use of a Src inhibitor reduced hepatocellular injury and enabled survival, indicating such agents may have some promise in the treatment of ALF.

Lipopolysaccharide-induced Notch signaling activation through JNK-dependent pathway regulates inflammatory response

BACKGROUND

Notch and TLR pathways were found to act cooperatively to activate Notch target genes and to increase the production of TLR-induced cytokines in macrophages. However, the mechanism of LPS-induced Notch activation and its role in sepsis still remains unclear.

METHODS

We analyzed the expression patterns of Notch components in a LPS-stimulated murine macrophage cell line using real-time PCR and western blotting. The role of DAPT, a gamma-secretase inhibitor that is known to be a potent Notch inhibitor, in LPS-induced cytokine release and experimental sepsis in mice was also explored. Student's t-test was used to analyze the difference between the two groups.

RESULTS

We found that Notch signaling was activated after LPS stimulation. The expression of Jagged 1, a Notch ligand, induced by LPS occurred in a JNK-dependent manner. In addition, Notch target genes were upregulated by early Notch-independent activation followed by delayed Notch-dependent activation after LPS stimulation. Disruption of Notch signaling by DAPT attenuated the LPS-induced inflammatory responses, including vascular endothelial growth factor (VEGF) and high-mobility group box chromosomal protein 1 (HMGB1), both in vitro and in vivo and partially improved experimental sepsis survival.

CONCLUSIONS

These findings support the existence of a synergistic effect of Notch signaling and the LPS pathway both in vitro and in vivo. Therefore, in the future Notch inhibitors may be utilized as adjunctive agents for the treatment of sepsis syndrome.

Placental growth factor in patients with decreased renal function

BACKGROUND

Patients with decreased renal function are characterized by high cardiovascular morbidity and mortality due to complications of premature atherosclerosis. Placental growth factor (PlGF) is a proatherogenic cytokine and new biomarker of cardiovascular events. The aim of this study was to determine PlGF levels and describe their relationship to renal function and risk factors of atherogenesis in patients with decreased renal function.

METHODS

The study group consisted of 114 subjects: 45 patients with various degrees of decreased renal function (CHRI), 31 long-term hemodialysis (HD) patients, and 38 age-matched healthy control subjects. PlGF was assessed immunochemically (enzyme-linked immunosorbent assay) and routine biochemical parameters were measured using standard laboratory methods.

RESULTS

PlGF levels were significantly increased in CHRI and HD patients compared to controls (10.5 ± 3.3 pg/mL in CHRI patients and 11.5 ± 3.4 pg/mL HD patients vs. 8.1 ± 1.8 pg/mL in controls, both p < 0.0001). In CHRI patients, PlGF was detectable in the urine, and its urine concentration correlated with its serum levels. In HD patients, PlGF correlated with low-density lipoproteins (r = 0.36, p < 0.05), but was not related to C-reactive protein levels. Higher levels of PlGF were found in CHRI patients with cardiovascular disease, compared with those free of such complication.

CONCLUSIONS

PlGF levels are increased in patients with decreased kidney function. PlGF is detectable in the urine, and serum and urine levels of PlGF are significantly interrelated. It is higher in CHRI patients with cardiovascular disease. Further studies are required to demonstrate the usefulness and significance of PlGF in patients with chronic kidney disease.

Sepsis and acute kidney injury

Sepsis is a severe and dysregulated inflammatory response to infection characterized by end-organ dysfunction distant from the primary site of infection. Development of acute kidney injury (AKI) during sepsis increases patient morbidity, predicts higher mortality, has a significant effect on multiple organ functions, is associated with an increased length of stay in the intensive care unit, and hence consumes considerable healthcare resources. When compared with AKI of nonseptic origin, septic AKI is characterized by a distinct pathophysiology and therefore requires a different approach. Despite impressive advances in several fields of medicine, the pathophysiology, diagnostic procedures, and appropriate therapeutic interventions in sepsis are still highly debatable. Numerous immunomodulatory agents showing promise in preclinical studies fail to reduce the overwhelmingly high mortality rate of sepsis and provoke AKI when compared with other critically ill patients. Major impediments to progress in understanding, early diagnosis, and application of appropriate therapeutic modalities in sepsis-induced AKI include limited histopathologic information, few animal models that closely mimic human sepsis, and a relative shortage of specific diagnostic tools. Here we discuss the most recent advances in understanding the fundamental mechanisms of sepsis-induced AKI, characteristics of relevant animal models available, and potential therapies.

A dynamic view of trauma/hemorrhage-induced inflammation in mice: principal drivers and networks

BACKGROUND

Complex biological processes such as acute inflammation induced by trauma/hemorrhagic shock/ (T/HS) are dynamic and multi-dimensional. We utilized multiplexing cytokine analysis coupled with data-driven modeling to gain a systems perspective into T/HS.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were subjected to surgical cannulation trauma (ST) ± hemorrhagic shock (HS; 25 mmHg), and followed for 1, 2, 3, or 4 h in each case. Serum was assayed for 20 cytokines and NO(2) (-)/NO(3) (-). These data were analyzed using four data-driven methods (Hierarchical Clustering Analysis [HCA], multivariate analysis [MA], Principal Component Analysis [PCA], and Dynamic Network Analysis [DyNA]). Using HCA, animals subjected to ST vs. ST + HS could be partially segregated based on inflammatory mediator profiles, despite a large overlap. Based on MA, interleukin [IL]-12p40/p70 (IL-12.total), monokine induced by interferon-γ (CXCL-9) [MIG], and IP-10 were the best discriminators between ST and ST/HS. PCA suggested that the inflammatory mediators found in the three main principal components in animals subjected to ST were IL-6, IL-10, and IL-13, while the three principal components in ST + HS included a large number of cytokines including IL-6, IL-10, keratinocyte-derived cytokine (CXCL-1) [KC], and tumor necrosis factor-α [TNF-α]. DyNA suggested that the circulating mediators produced in response to ST were characterized by a high degree of interconnection/complexity at all time points; the response to ST + HS consisted of different central nodes, and exhibited zero network density over the first 2 h with lesser connectivity vs. ST at all time points. DyNA also helped link the conclusions from MA and PCA, in that central nodes consisting of IP-10 and IL-12 were seen in ST, while MIG and IL-6 were central nodes in ST + HS.

CONCLUSIONS/SIGNIFICANCE

These studies help elucidate the dynamics of T/HS-induced inflammation, complementing other forms of dynamic mechanistic modeling. These methods should be applicable to the analysis of other complex biological processes.

Sepsis and the broken endothelium

The study by Yang and colleagues examined 81 patients with septic shock due to pneumonia, along with 20 patients with pneumonia without organ dysfunction. Their major findings were that circulating levels of soluble vascular endothelial cell growth factor receptor-1 (sVEGFR-1) and urokinase-type plasminogen activator (uPA) were associated with organ dysfunction and mortality, whereas vascular endothelial cell growth factor (VEGF) levels had no such predictive power. Yang and colleagues are to be complimented for a well-conducted study of a reasonably (and helpfully!) homogeneous population of patients with sepsis that carefully and comprehensively analyzed the relationship between sVEGFR-1, uPA, VEGF and clinical outcome. The study serves not only to provide evidence in support of new diagnostic biomarker targets in sepsis, but also to augment the growing evidence of an important role of the endothelium in sepsis in general, and the VEGF signaling axis in particular.

Time-course of sFlt-1 and VEGF-A release in neutropenic patients with sepsis and septic shock: a prospective study

Background

Septic shock is the most feared complication of chemotherapy-induced febrile neutropenia. So far, there are no robust biomarkers that can stratify patients to the risk of sepsis complications. The VEGF-A axis is involved in the control of microvascular permeability and has been involved in the pathogenesis of conditions associated with endothelial barrier disruption such as sepsis. sFlt-1 is a soluble variant of the VEGF-A receptor VEGFR-1 that acts as a decoy receptor down-regulating the effects of VEGF-A. In animal models of sepsis, sFlt-1 was capable to block the barrier-breaking negative effects of VEGF-A and to significantly decrease mortality. In non-neutropenic patients, sFlt-1 has been shown to be a promising biomarker for sepsis severity.

Methods

We prospectively evaluated concentrations of sFlt-1 and VEGF-A at different time-points during febrile neutropenia, and evaluated the association of these levels with sepsis severity and septic shock development.

Results

Neutropenic patients that evolved with septic shock (n = 10) presented higher levels of sFlt-1 and VEGF-A measured 48 hours after fever onset than patients with non-complicated sepsis (n = 31) and levels of these biomarkers correlated with sepsis severity scores. Estimation of the diagnostic accuracy of sFlt-1 levels for the discrimination of patients that evolved to septic shock yielded promising results in our study population.

Discussion

Our data suggest that sFlt-1 and VEGF-A could be useful biomarkers for sepsis severity in patients with febrile neutropenia. In addition, the kinetics of sFlt-1 release in patients that evolve to septic shock suggest that the sFlt-1 could be a salvage compensatory mechanism in patients with septic shock, but that the magnitude of the sFlt-1 release observed in human sepsis is not sufficient to reproduce the beneficial anti-VEGF-A effects observed in animal models of sepsis.

Combinations of host biomarkers predict mortality among Ugandan children with severe malaria: a retrospective case-control study

Background

Severe malaria is a leading cause of childhood mortality in Africa. However, at presentation, it is difficult to predict which children with severe malaria are at greatest risk of death. Dysregulated host inflammatory responses and endothelial activation play central roles in severe malaria pathogenesis. We hypothesized that biomarkers of these processes would accurately predict outcome among children with severe malaria.

Methodology/Findings

Plasma was obtained from children with uncomplicated malaria (n = 53), cerebral malaria (n = 44) and severe malarial anemia (n = 59) at time of presentation to hospital in Kampala, Uganda. Levels of angiopoietin-2, von Willebrand Factor (vWF), vWF propeptide, soluble P-selectin, soluble intercellular adhesion molecule-1 (ICAM-1), soluble endoglin, soluble FMS-like tyrosine kinase-1 (Flt-1), soluble Tie-2, C-reactive protein, procalcitonin, 10 kDa interferon gamma-induced protein (IP-10), and soluble triggering receptor expressed on myeloid cells-1 (TREM-1) were determined by ELISA. Receiver operating characteristic (ROC) curve analysis was used to assess predictive accuracy of individual biomarkers. Six biomarkers (angiopoietin-2, soluble ICAM-1, soluble Flt-1, procalcitonin, IP-10, soluble TREM-1) discriminated well between children who survived severe malaria infection and those who subsequently died (area under ROC curve>0.7). Combinational approaches were applied in an attempt to improve accuracy. A biomarker score was developed based on dichotomization and summation of the six biomarkers, resulting in 95.7% (95% CI: 78.1–99.9) sensitivity and 88.8% (79.7–94.7) specificity for predicting death. Similar predictive accuracy was achieved with models comprised of 3 biomarkers. Classification tree analysis generated a 3-marker model with 100% sensitivity and 92.5% specificity (cross-validated misclassification rate: 15.4%, standard error 4.9%).

Conclusions

We identified novel host biomarkers of pediatric severe and fatal malaria (soluble TREM-1 and soluble Flt-1) and generated simple biomarker combinations that accurately predicted death in an African pediatric population. While requiring validation in further studies, these results suggest the utility of combinatorial biomarker strategies as prognostic tests for severe malaria.

Elevated Soluble fms-Like Tyrosine Kinase-1 Levels in Acute Coronary Occlusion

Objective—

Early recognition of an acute coronary occlusion (ACO) improves clinical outcomes. Soluble fms-like tyrosine kinase-1 (sFLT1) is an endothelium-derived protein induced by hypoxia. We tested whether sFLT1 levels are elevated in ACO.

Methods and Results—

Serum sFLT1 levels were measured by enzyme-linked immunosorbent assay in patients with ST-segment elevations and angiographically confirmed ACO, unstable angina/non ST-segment elevation myocardial infarction, and 2 control groups. To further explore sFLT1 release, a mouse model of ACO and in vitro human coronary artery endothelial cell injury were used. sFLT1 levels were increased in ACO compared with unstable angina/non-ST-elevation myocardial infarction, catheterized controls, or healthy volunteers (200.7±15.5 versus 70.7±44.0 versus 10.2±4.0 versus 11.7±1.7 pg/mL respectively, P <0.001 versus ACO). At presentation, all ACO patients had elevated sFLT1 levels (>15 pg/mL, 99th percentile in controls), whereas 57% had levels of the MB isoform of creatine kinase levels >10 ng/mL ( P <0.01) and 85% had ultrasensitive troponin I levels >0.05 ng/mL ( P <0.05). Within 60 minutes after symptom onset, sFLT1 was more sensitive than the MB isoform of creatine kinase or ultrasensitive troponin I for ACO (100% versus 20% versus 20% respectively; P ≤0.01 for each). Within 60 minutes of ACO in mice, sFLT1 levels were elevated. Hypoxia and thrombin increased sFLT1 levels within 15 minutes in human coronary artery endothelial cells.

Conclusion—

sFLT1 levels may be an early indicator of endothelial hypoxia in ACO.

A2B adenosine receptor blockade enhances macrophage-mediated bacterial phagocytosis and improves polymicrobial sepsis survival in mice

Antimicrobial treatment strategies must improve to reduce the high mortality rates in septic patients. In noninfectious models of acute inflammation, activation of A2B adenosine receptors (A2BR) in extracellular adenosine-rich microenvironments causes immunosuppression. We examined A2BR in antibacterial responses in the cecal ligation and puncture (CLP) model of sepsis. Antagonism of A2BR significantly increased survival, enhanced bacterial phagocytosis, and decreased IL-6 and MIP-2 (a CXC chemokine) levels after CLP in outbred (ICR/CD-1) mice. During the CLP-induced septic response in A2BR knockout mice, hemodynamic parameters were improved compared with wild-type mice in addition to better survival and decreased plasma IL-6 levels. A2BR deficiency resulted in a dramatic 4-log reduction in peritoneal bacteria. The mechanism of these improvements was due to enhanced macrophage phagocytic activity without augmenting neutrophil phagocytosis of bacteria. Following ex vivo LPS stimulation, septic macrophages from A2BR knockout mice had increased IL-6 and TNF-α secretion compared with wild-type mice. A therapeutic intervention with A2BR blockade was studied by using a plasma biomarker to direct therapy to those mice predicted to die. Pharmacological blockade of A2BR even 32 h after the onset of sepsis increased survival by 65% in those mice predicted to die. Thus, even the late treatment with an A2BR antagonist significantly improved survival of mice (ICR/CD-1) that were otherwise determined to die according to plasma IL-6 levels. Our findings of enhanced bacterial clearance and host survival suggest that antagonism of A2BRs offers a therapeutic target to improve macrophage function in a late treatment protocol that improves sepsis survival.

Plasma soluble vascular endothelial growth factor receptor-1 levels predict outcomes of pneumonia-related septic shock patients: a prospective observational study

INTRODUCTION

Despite recent advances in the management of septic shock, mortality rates are still unacceptably high. Early identification of the high-mortality risk group for early intervention remains an issue under exploration. Vascular endothelial growth factor (VEGF), soluble vascular endothelial growth factor receptor-1 (sVEGFR1) and urokinase plasminogen activator (uPA) have diverse effects in the pathogenesis of sepsis, which involve pro-inflammation, anti-inflammation, endothelial cell repair, and vascular permeability change. Their roles in predicting mortality and organ dysfunction remain to be clarified.

METHODS

Pneumonia-related septic shock patients from medical intensive care units were enrolled for this prospective observational study. We also included 20 patients with pneumonia without organ dysfunction for comparison. Plasma levels of VEGF and sVEGFR1 and uPA activity within 24 hours of shock onset were measured. We compared plasma levels of these biomarkers with APACHE II scores between subgroups of patients, and evaluated their predictive value for 28-day mortality and organ dysfunction.

RESULTS

A total of 101 patients, including 81 with pneumonia-related septic shock and 20 with pneumonia without organ dysfunction, were enrolled. Non-survivors of septic shock had significantly higher plasma sVEGFR1 levels (659.3 ± 1022.8 vs. 221.1 ± 268.9 pg/mL, respectively, P < 0.001) and uPA activity (47.2 ± 40.6 vs. 27.6 ± 17.2 units, respectively, P = 0.001) when compared with those of the survivors. Kaplan-Meier survival analysis demonstrated significantly higher mortality in patients with higher levels of sVEGFR1 (P < 0.001) and uPA activity (P = 0.031). In Cox regression analysis, plasma sVEGFR1 level was independently associated with, and best predicted, the 28-day mortality of septic shock (HR: 1.55, 95% CI: 1.05-2.30). Plasma sVEGFR1 level and uPA activity had good correlation with renal dysfunction, metabolic acidosis, and hematologic dysfunction; their levels significantly increased when the number of organ dysfunctions increased. In multivariate analysis, plasma sVEGFR1 level (HR: 2.82, 95% CI: 1.17-6.81) and uPA activity (HR: 2.75, 95% CI: 1.06-7.13) were independent predictors of the presence of concomitant multi-organ dysfunction. The predictive value of VEGF for mortality and organ dysfunction was limited in pneumonia-related septic shock patients.

CONCLUSIONS

High plasma sVEGFR1 level in the early stage of pneumonia-related septic shock independently predicted 28-day mortality and multi-organ dysfunction.

mTORC1-S6K activation by endotoxin contributes to cytokine up-regulation and early lethality in animals

Background

mTORC1 (mammalian target of rapamycin complex 1) activation has been demonstrated in response to endotoxin challenge, but the mechanism and significance are unclear. We investigated the effect of mTORC1 suppression in an animal model of endotoxemia and in a cellular model of endotoxin signaling.

Methodology/Principal Findings

Mice were treated with the mTORC1 inhibitor rapamycin or vehicle prior to lethal endotoxin challenge. Mortality and cytokine levels were assessed. Cultured macrophage-like cells were challenged with endotoxin with or without inhibitors of various pathways known to be upstream of mTORC1. Activated pathways, including downstream S6K pathway, were assessed by immunoblots. We found that mTORC1-S6K suppression by rapamycin delayed mortality of mice challenged with lethal endotoxin, and was associated with dampened circulating levels of VEGF, IL-1β, IFN-γ and IL-5. Furthermore, in vitro cellular studies demonstrated that LPS (lipopolysaccharide) activation of mTORC1-S6K still occurs in the presence of PI3K-Akt inhibition alone, but can be suppressed by concurrent inhibition of PI3K-Akt and MEK-ERK pathways.

Conclusions/Significance

We conclude that cellular activation of mTORC1-S6K contributes to cytokine up-regulation and mortality in response to endotoxin, and may occur via multiple pathways.

Differential regulation of human and murine P-selectin expression and function in vivo

Basal and inducible expression of human P-selectin in transgenic mice differs from that of murine P-selectin, resulting in distinct functions.

Leukocytes roll on P-selectin after its mobilization from secretory granules to the surfaces of platelets and endothelial cells. Tumor necrosis factor (TNF), IL-1β, and lipopolysaccharide increase synthesis of P-selectin in murine but not in human endothelial cells. To explore the physiological significance of this difference in gene regulation, we made transgenic mice bearing the human Selp gene and crossed them with mice lacking murine P-selectin (Selp^−/−). The transgenic mice constitutively expressed human P-selectin in platelets, endothelial cells, and macrophages. P-selectin mediated comparable neutrophil migration into the inflamed peritoneum of transgenic and wild-type (WT) mice. Leukocytes rolled similarly on human or murine P-selectin on activated murine platelets and in venules of the cremaster muscle subjected to trauma. However, TNF increased murine P-selectin in venules, slowing rolling and increasing adhesion, whereas it decreased human P-selectin, accelerating rolling and decreasing adhesion. Both P- and E-selectin mediated basal rolling in the skin of WT mice, but E-selectin dominated rolling in transgenic mice. During contact hypersensitivity, murine P-selectin messenger (m) RNA was up-regulated and P-selectin was essential for leukocyte recruitment. However, human P-selectin mRNA was down-regulated and P-selectin contributed much less to leukocyte recruitment. These findings reveal functionally significant differences in basal and inducible expression of human and murine P-selectin in vivo.

Placental growth factor mediates aldosterone-dependent vascular injury in mice

In clinical trials, aldosterone antagonists reduce cardiovascular ischemia and mortality by unknown mechanisms. Aldosterone is a steroid hormone that signals through renal mineralocorticoid receptors (MRs) to regulate blood pressure. MRs are expressed and regulate gene transcription in human vascular cells, suggesting that aldosterone might have direct vascular effects. Using gene expression profiling, we identify the pro-proliferative VEGF family member placental growth factor (PGF) as an aldosterone-regulated vascular MR target gene in mice and humans. Aldosterone-activated vascular MR stimulated Pgf gene transcription and increased PGF protein expression and secretion in the mouse vasculature. In mouse vessels with endothelial damage and human vessels from patients with atherosclerosis, aldosterone enhanced expression of PGF and its receptor, FMS-like tyrosine kinase 1 (Flt1). In atherosclerotic human vessels, MR antagonists inhibited PGF expression. In vivo, aldosterone infusion augmented vascular remodeling in mouse carotids following wire injury, an effect that was lost in Pgf-/- mice. In summary, we have identified PGF as what we believe to be a novel downstream target of vascular MR that mediates aldosterone augmentation of vascular injury. These findings suggest a non-renal mechanism for the vascular protective effects of aldosterone antagonists in humans and support targeting the vascular aldosterone/MR/PGF/Flt1 pathway as a therapeutic strategy for ischemic cardiovascular disease.

The association of endothelial cell signaling, severity of illness, and organ dysfunction in sepsis

Introduction

Previous reports suggest that endothelial activation is an important process in sepsis pathogenesis. We investigated the association between biomarkers of endothelial cell activation and sepsis severity, organ dysfunction sequential organ failure assessment (SOFA) score, and death.

Methods

This is a prospective, observational study including adult patients (age 18 years or older) presenting with clinical suspicion of infection to the emergency department (ED) of an urban, academic medical center between February 2005 and November 2008. Blood was sampled during the ED visit and biomarkers of endothelial cell activation, namely soluble fms-like tyrosine kinase-1 (sFlt-1), plasminogen activator inhibitors -1 (PAI-1), sE-selectin, soluble intercellular adhesion molecule (sICAM-1), and soluble vascular cell adhesion molecule (sVCAM-1), were assayed. The association between biomarkers and the outcomes of sepsis severity, organ dysfunction, and in-hospital mortality were analyzed.

Results

A total of 221 patients were included: sepsis without organ dysfunction was present in 32%, severe sepsis without shock in 30%, septic shock in 32%, and 6% were non-infected control ED patients. There was a relationship between all target biomarkers (sFlt-1, PAI-1, sE-selectin, sICAM-1, and sVCAM-1) and sepsis severity, P < 0.05. We found a significant inter-correlation between all biomarkers, including the strongest correlations between sFlt-1 and sE-selectin (r = 0.55, P < 0.001), and between sFlt-1 and PAI-1 (0.56, P < 0.001). Among the endothelial cell activation biomarkers, sFlt-1 had the strongest association with SOFA score (r = 0.66, P < 0.001), the highest area under the receiver operator characteristic curve for severe sepsis of 0.82, and for mortality of 0.91.

Conclusions

Markers of endothelial cell activation are associated with sepsis severity, organ dysfunction and mortality. An improved understanding of endothelial response and associated biomarkers may lead to strategies to more accurately predict outcome and develop novel endothelium-directed therapies in sepsis.