Neutrophils from critically ill septic patients mediate profound loss of endothelial barrier integrity

Urinary trypsin inhibitor attenuates LPS-induced endothelial barrier dysfunction by upregulation of vascular endothelial-cadherin expression

INTRODUCTION

Urinary trypsin inhibitor (UTI) decreases inflammatory cytokine levels and mortality in experimental animal models of inflammation. Here, we observed the effect of UTI on lipopolysaccharide (LPS)-induced hyperpermeability in human umbilical vein endothelial cells (HUVECs) and explored the role of vascular endothelial-cadherin (VE-cadherin) in its effect.

METHODS

The effect of UTI on endothelial barrier hyperpermeability was detected by an electrical cell-substrate impedance sensing (ECIS) system and a transwell chamber system. The expression of VE-cadherin in HUVECs was examined by real-time PCR and western blot.

RESULTS

We demonstrated that the alleviation of LPS-induced barrier dysfunction could be achieved by pretreatment with 3000 U/mL of UTI. VE-cadherin monoclonal antibody (mAb) could inhibit the protective effects. UTI maintained VE-cadherin expression by increasing protein stability at both the transcriptional and post-transcriptional levels. Meanwhile, VE-cadherin expression on the cell surface increased when the cells were pretreated with UTI. Furthermore, pretreatment with UTI decreased the phosphorylation of VE-cadherin at Tyr658 but not Tyr731.

CONCLUSIONS

Our data show that prophylactic UTI maintains the endothelial barrier function, increases VE-cadherin expression, and inhibits the phosphorylation of VE-cadherin at Tyr658 under inflammatory conditions. It suggests a scientific and potential clinical therapeutic importance of UTI in treatment of inflammatory disorders.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Low molecular weight heparin prevents lipopolysaccharide induced-hippocampus-dependent cognitive impairments in mice

Sepsis-associated encephalopathy (SAE) is a common complication after sepsis development, which is associated with the poor prognosis. However, no effective agent is currently available to treat this complication. The objective of the present study was to investigate whether low-molecular-weight heparin (LMWH) has protective effects against sepsis-induced cognitive impairments. Male mice were randomly divided into the control + vehicle, control + LMWH, lipopolysaccharide (LPS) + vehicle, or LPS + LMWH group. LMWH was administrated 30 min after the LPS administration (5 mg/kg) and daily afterward for 2 days. The survival rate was estimated by the Kaplan-Meier method. Behavioral tests were performed by open field and fear conditioning tests at day 7 after LPS administration. The levels of tumor necrosis factor alpha, interleukin (IL)-1β, IL-6, IL-10, malondialdehyde, and superoxide dismutase, Toll-like receptor 4, nuclear factor kappa B p65, inducible nitric oxide synthase, cyclooxygenase-2, occluding, high mobility group box-1, brain derived neurotrophic factor, and IBA1 positive cells were assessed at the indicated time points. LMWH attenuated LPS-induced hippocampus-dependent cognitive impairments, which was accompanied by decreased hippocampal IL-1β, malondialdehyde, Toll-like receptor 4, nuclear factor kappa B p65, inducible nitric oxide synthase, cyclooxygenase-2, high mobility group box-1 protein, and IBA1 positive cells, and increased occluding and brain derived neurotrophic factor levels. In conclusion, LMWH treatment protects against sepsis-induced cognitive impairments by attenuating hippocampal microglial activation, cytokine and oxidative stress production, disruption of blood-brain barrier, and the loss of synaptic plasticity related proteins.

Relationship between leukocytes recruitment and risk of rebleeding in patients with peptic ulcers

AIM

The aim of this study was to assess the impact of leukocytes reaction on rebleeding development among patients with peptic ulcers.

METHODS

This was a single-center cohort study enrolling 232 patients with a diagnosis of gastroduodenal ulcer bleeding. The end point was the in-hospital rebleeding rate during the three days after admission. The impact of clinical, demographic, endoscopic and laboratory data at the time of admission, as well as macrophages (CD68) and neutrophils count in ulcer margin, on bleeding outcome was assessed. In addition, impact of the leukocytes on the platelets aggregation induced with ADP (5μM) and collagen (1μM) was measured in vitro.

RESULTS

Acute ulcer bleeding was accompanied with an acute inflammatory response to damage and hemorrhage. Despite the increase of neutrophil count (P=0.031) in peripheral blood of bleeders, there were not significant influence of this parameter on the outcome. It was shown that the most significant predicting factors were an increased neutrophils (OR 1.4; 95% CI 1.1-1.8) and macrophages count in the ulcer margin (OR 3.5; 95% CI 1.9-4.87); an endoscopically diagnosed active bleeding (OR 3.0; 95% CI 1.4-6.3); an enhanced level of plasma fibrinogen (OR 1.04; 95% CI 1.0-1.08). Co-incubation of platelets with leukocytes significantly decreased the collagen induced aggregation (P=0.008) that could indicate either alteration of mechanisms of platelets adhesion, or inhibition of stabilization phase of thrombogenesis.

CONCLUSION

The severity of the local acute inflammatory reaction promotes progressive tissue damage of ulcer margin, and increases the risk of rebleeding.

Regulation of autophagy by the nuclear factor κB signaling pathway in the hippocampus of rats with sepsis

BACKGROUND

Sepsis with brain dysfunction has contributed to an increase risk of morbidity and mortality. In its pathophysiology, both autophagy and nuclear factor κB (NF-κB) have been suggested to play important roles. Based on the fact that crosstalk between autophagy and NF-κB, two stress-response signaling pathways, has been detected in other pathophysiological processes, this study was undertaken to explore the process of autophagy in the hippocampus of septic rats and the role NF-κB plays in the regulation of autophagy during the process.

METHODS

Cecal ligation and puncture (CLP) or a sham operation was conducted on male Wistar rats. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the NF-κB signaling pathway, or a vehicle control, was used to treat with the rats 2 h before the CLP operation. Hematoxylin-eosin staining and biological signal recording was used to measure the morphological and physiological signs of hippocampal dysfunction. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampus after CLP. Western blotting and immune histochemistry were used to detect the hippocampus levels of NF-κB and essential proteins involved in formation of the autophagosome (microtubule-associated protein light chain 3 (LC3), Beclin1, Lamp-1, and Rab7).

RESULTS

Compared with sham-operated rats, the CLP rats showed decreasing mean arterial pressure (MAP), increasing heart rate (HR), and pathological histological changes. CLP rats exhibited not only increased vacuolization through electron micrographs but also increased LC3-II, decreased Beclin1, LAMP-1, and Rab7 through the immunofluorescence and Western blot. However, PDTC + CLP rats revealed that inhibition of the NF-κB signal axis by PDTC increased the levels of LC3-II, Beclin1, LAMP-1, and Rab7 and improved physiological function including blood pressure and heart rate.

CONCLUSIONS

The autophagy process during the hippocampus of CLP rats might be blocked by the activation of NF-κB signaling pathway. Inhibition of NF-κB signaling pathway could enhance the completion of autophagy with a neuroprotective function in septic brains.

Advances in understanding of the pathogenesis of acute respiratory distress syndrome

The clinical syndrome of acute lung injury (ALI) occurs as a result of an initial acute systemic inflammatory response. This can be consequent to a plethora of insults, either direct to the lung or indirect. The insult results in increased epithelial permeability, leading to alveolar flooding with a protein-rich oedema fluid. The resulting loss of gas exchange leads to acute respiratory failure and typically catastrophic illness, termed acute respiratory distress syndrome (ARDS), requiring ventilatory and critical care support. There remains a significant disease burden, with some estimates showing 200,000 cases each year in the USA with a mortality approaching 50%. In addition, there is a significant burden of morbidity in survivors. There are currently no disease-modifying therapies available, and the most effective advances in caring for these patients have been in changes to ventilator strategy as a result of the ARDS network studies nearly 15 years ago. Here, we will give an overview of more recent advances in the understanding of the cellular biology of ALI and highlight areas that may prove fertile for future disease-modifying therapies.

Blood cells and endothelial barrier function

The barrier properties of endothelial cells are critical for the maintenance of water and protein balance between the intravascular and extravascular compartments. An impairment of endothelial barrier function has been implicated in the genesis and/or progression of a variety of pathological conditions, including pulmonary edema, ischemic stroke, neurodegenerative disorders, angioedema, sepsis and cancer. The altered barrier function in these conditions is often linked to the release of soluble mediators from resident cells (e.g., mast cells, macrophages) and/or recruited blood cells. The interaction of the mediators with receptors expressed on the surface of endothelial cells diminishes barrier function either by altering the expression of adhesive proteins in the inter-endothelial junctions, by altering the organization of the cytoskeleton, or both. Reactive oxygen species (ROS), proteolytic enzymes (e.g., matrix metalloproteinase, elastase), oncostatin M, and VEGF are part of a long list of mediators that have been implicated in endothelial barrier failure. In this review, we address the role of blood borne cells, including, neutrophils, lymphocytes, monocytes, and platelets, in the regulation of endothelial barrier function in health and disease. Attention is also devoted to new targets for therapeutic intervention in disease states with morbidity and mortality related to endothelial barrier dysfunction.

Properdin levels in human sepsis

Properdin is a normal serum protein that increases the production of complement activation products by binding C3b integral to convertase complexes and amplifying their activity at the site of activation. Thereby, it not only can aid in the resolution of infection but also contribute to tissue damage. In human sepsis, circulating complement C3 concentrations are decreased, though C3 is described as a positive acute phase reactant. However, properdin levels in human sepsis have not been reported. In this study, serum from 81 critically ill patients (predominately abdominal and respiratory sepsis) were analyzed for properdin levels at defined points of their stay in the intensive care unit (ICU) and compared with 61 age and sex-matched healthy volunteers. Properdin concentrations were significantly decreased in patients with sepsis on admission to ICU, but increased after clinical recovery to exceed levels observed in healthy volunteers. Properdin concentrations at ICU admission were decreased in non-survivors of sepsis compared to survivors, but this did not correlate with APACHE II score. However, pathologically low properdin levels (<7 μg/ml) were related to increased duration of treatment.

Transcriptomic correlates of organ failure extent in sepsis

OBJECTIVES

Sepsis is characterised by the frequent presence of organ failure and marked immunologic alterations. We studied the association between the extent of organ failure and the transcriptomic response of septic patients.

METHODS

Gene expression profiles in the blood of 74 surgical patients with sepsis were compared with those of 30 surgical patients with no sepsis. Differentially expressed genes were assessed for their correlation with the sequential organ failure (SOFA) score.

RESULTS

The expression levels of a group of genes participating in the cell cycle (HIST1H1C, CKS2, CCNA2, CDK1, CCNB2, CIT, CCNB1, AURKA, RAD51), neutrophil protease activity (ELANE, ADORA3, MPO, MMP8, CTSG), IL-1R and IL-18R response correlated directly with SOFA and mortality. Genes involved in T cell (LCK, CD3G, CD3D, ZAP70, ICOS, CD3E, CD28, IL2RB, CD8B, CD8A, CD40LG, IL23A, CCL5, SH2D1A, ITK, CD247, TBX21, GATA3, CCR7, LEF1, STAT4) and NK cell immunity (CD244, KLRK1, KLRD1) were inversely associated with SOFA and mortality.

CONCLUSIONS

The extent of organ failure in sepsis correlates directly with the existence of imbalanced innate and adaptive responses at the transcriptomic level. Quantification of the expression levels of the genes identified here could contribute to the simultaneous assessment of disease severity and immunological alterations in sepsis.

The mercurial nature of neutrophils: still an enigma in ARDS?

The acute respiratory distress syndrome (ARDS) is a life-threatening lung condition resulting from direct and indirect insults to the lung. It is characterized by disruption of the endothelial-epithelial barrier, alveolar damage, pulmonary edema, and respiratory failure. A key feature of ARDS is the accumulation of neutrophils in the lung microvasculature, interstitium, and alveolar space. Despite a clear association between neutrophil influx into the lung and disease severity, there is some debate as to whether neutrophils directly contribute to disease pathogenesis. The primary function of neutrophils is to provide immediate host defense against pathogenic microorganisms. Neutrophils release numerous antimicrobial factors such as reactive oxygen species, proteinases, and neutrophil extracellular traps. However, these factors are also toxic to host cells and can result in bystander tissue damage. The excessive accumulation of neutrophils in ARDS may therefore contribute to disease progression. Central to neutrophil recruitment is the release of chemokines, including the archetypal neutrophil chemoattractant IL-8, from resident pulmonary cells. However, the chemokine network in the inflamed lung is complex and may involve several other chemokines, including CXCL10, CCL2, and CCL7. This review will therefore focus on the experimental and clinical evidence supporting neutrophils as key players in ARDS and the chemokines involved in recruiting them into the lung.