Disturbed homeostasis of lung intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 during sepsis

Substance P Promotes Leukocyte Infiltration in the Liver and Lungs of Mice with Sepsis: A Key Role for Adhesion Molecules on Vascular Endothelial Cells

Substance P (SP), encoded by the Tac1 gene, has been shown to promote leukocyte infiltration and organ impairment in mice with sepsis. Neurokinin-1 receptor (NK1R) is the major receptor that mediates the detrimental impact of SP on sepsis. This investigation studied whether SP affects the expression of adhesion molecules, including intercellular cell adhesion molecule-1 (ICAM1) and vascular cell adhesion molecule-1 (VCAM1) on vascular endothelial cells in the liver and lungs, contributing to leukocyte infiltration in these tissues of mice with sepsis. Sepsis was induced by caecal ligation and puncture (CLP) surgery in mice. The actions of SP were inhibited by deleting the Tac1 gene, blocking NK1R, or combining these two methods. The activity of myeloperoxidase and the concentrations of ICAM1 and VCAM1 in the liver and lungs, as well as the expression of ICAM1 and VCAM1 on vascular endothelial cells in these tissues, were measured. The activity of myeloperoxidase and the concentration of ICAM1 and VCAM1 in the liver and lungs, as well as the expression of ICAM1 and VCAM1 on vascular endothelial cells in these tissues, increased in mice with CLP surgery-induced sepsis. Suppressing the biosynthesis of SP and its interactions with NK1R attenuated CLP surgery-induced alterations in the liver and lungs of mice. Our findings indicate that SP upregulates the expression of ICAM1 and VCAM1 on vascular endothelial cells in the liver and lungs, thereby increasing leukocyte infiltration in these tissues of mice with CLP surgery-induced sepsis by activating NK1R.

Possible pharmacological targets and mechanisms of sivelestat in protecting acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a life-threatening syndrome induced by various diseases, including COVID-19. In the progression of ALI/ARDS, activated neutrophils play a central role by releasing various inflammatory mediators, including elastase. Sivelestat is a selective and competitive inhibitor of neutrophil elastase. Although its protective effects on attenuating ALI/ARDS have been confirmed in several models of lung injury, clinical trials have presented inconsistent results on its therapeutic efficacy. Therefore, in this report, we used a network pharmacology approach coupled with animal experimental validation to unravel the concrete therapeutic targets and biological mechanisms of sivelestat in treating ALI/ARDS. In bioinformatic analyses, we found 118 targets of sivelestat against ALI/ARDS, and identified six hub genes essential for sivelestat treatment of ALI/ARDS, namely ERBB2, GRB2, PTK2, PTPN11, ESR1, and CCND1. We also found that sivelestat targeted several genes expressed in human lung microvascular endothelial cells after lipopolysaccharide (LPS) treatment at 4 h (ICAM-1, PTGS2, RND1, BCL2A1, TNF, CA2, and ADORA2A), 8 h (ICAM-1, PTGS2, RND1, BCL2A1, MMP1, BDKRB1 and SLC40A1), and 24 h (ICAM-1). Further animal experiments showed that sivelestat was able to attenuate LPS-induced ALI by inhibiting the overexpression of ICAM-1, VCAM-1, and PTGS2 and increasing the phosphorylation of PTK2. Taken together, the bioinformatic findings and experimentative data indicate that the therapeutic effects of sivelestat against ALI/ARDS mainly focus on the early stage of ALI/ARDS by pharmacological modulation of inflammatory reaction, vascular endothelial injury, and cell apoptosis-related molecules.

Spleen Tyrosine Kinase phosphorylates VE-cadherin to cause endothelial barrier disruption in acute lung injury

Increased endothelial cell (EC) permeability is a cardinal feature of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Tyrosine phosphorylation of VE-cadherin is a key determinant of EC barrier disruption. However, the identity and role of tyrosine kinases in this context are incompletely understood. Here we report that Spleen Tyrosine Kinase (Syk) is a key mediator of EC barrier disruption and lung vascular leak in sepsis. Inhibition of Syk by pharmacological or genetic approaches, each reduced thrombin-induced EC permeability. Mechanistically, Syk associates with and phosphorylates VE-cadherin to cause EC permeability. To study the causal role of endothelial Syk in sepsis-induced ALI, we used a remarkably efficient and cost-effective approach based on gene transfer to generate EC-ablated Syk mice. These mice were protected against sepsis-induced loss of VE-cadherin and inflammatory lung injury. Notably, the administration of Syk inhibitor R788 (fostamatinib); currently in phase II clinical trial for the treatment of COVID-19, mitigated lung injury and mortality in mice with sepsis. These data identify Syk as a novel kinase for VE-cadherin and a druggable target against ALI in sepsis.

Synergistic Pulmonoprotective Effect of Natural Prolyl Oligopeptidase Inhibitors in In Vitro and In Vivo Models of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a highly morbid inflammatory lung disease with limited pharmacological interventions. The present study aims to evaluate and compare the potential pulmonoprotective effects of natural prolyl oligopeptidase (POP) inhibitors namely rosmarinic acid (RA), chicoric acid (CA), epigallocatechin-3-gallate (EGCG) and gallic acid (GA), against lipopolysaccharide (LPS)-induced ARDS. Cell viability and expression of pro-inflammatory mediators were measured in RAW264.7 cells and in primary murine lung epithelial and bone marrow cells. Nitric oxide (NO) production was also assessed in unstimulated and LPS-stimulated RAW264.7 cells. For subsequent in vivo experiments, the two natural products (NPs) with the most favorable effects, RA and GA, were selected. Protein, cell content and lipid peroxidation levels in bronchoalveolar lavage fluid (BALF), as well as histopathological changes and respiratory parameters were evaluated in LPS-challenged mice. Expression of key mediators involved in ARDS pathophysiology was detected by Western blotting. RA and GA favorably reduced gene expression of pro-inflammatory mediators in vitro, while GA decreased NO production in macrophages. In LPS-challenged mice, RA and GA co-administration improved respiratory parameters, reduced cell and protein content and malondialdehyde (MDA) levels in BALF, decreased vascular cell adhesion molecule-1 (VCAM-1) and the inducible nitric oxide synthase (iNOS) protein expression, activated anti-apoptotic mechanisms and down-regulated POP in the lung. Conclusively, these synergistic pulmonoprotective effects of RA and GA co-administration could render them a promising prophylactic/therapeutic pharmacological intervention against ARDS.

Up-regulation of Myocardial Klotho Expression to Promote Cardiac Functional Recovery in Old Mice following Endotoxemia

Objective

Endotoxemic cardiac dysfunction contributes to greater morbidity and mortality in elderly patients with sepsis. This study tested the hypothesis that Klotho insufficiency in aging heart exaggerates and prolongs myocardial inflammation to hinder cardiac function recovery following endotoxemia.

Methods

Endotoxin (0.5 mg/kg, iv) was administered to young adult (3-4 months) and old (18-22 months) mice with or without subsequent treatment with recombinant interleukin-37 (IL-37, 50 μg/kg, iv) or recombinant Klotho (10 μg/kg, iv). Cardiac function was analyzed using a microcatheter 24, 48 and 96 h later. Myocardial levels of Klotho, ICAM-1, VCAM-1 and IL-6 were determined by immunoblotting and ELISA.

Results

In comparison to young adult mice, old mice had worse cardiac dysfunction accompanied by greater myocardial levels of ICAM-1, VCAM-1 and IL-6 at each time point following endotoxemia and failed to fully recover cardiac function by 96 h. The exacerbated myocardial inflammation and cardiac dysfunction were associated with endotoxemia-caused further reduction of lower myocardial Klotho level in old mice. Recombinant IL-37 promoted inflammation resolution and cardiac functional recovery in old mice. Interestingly, recombinant IL-37 markedly up-regulated myocardial Klotho levels in old mice with or without endotoxemia. Similarly, recombinant Klotho suppressed myocardial inflammatory response and promoted inflammation resolution in old endotoxemic mice, leading to complete recovery of cardiac function by 96 h.

Conclusion

Myocardial Klotho insufficiency in old endotoxemic mice exacerbates myocardial inflammatory response, impairs inflammation resolution and thereby hinders cardiac functional recovery. IL-37 is capable of up-regulating myocardial Klotho expression to improve cardiac functional recovery in old endotoxemic mice.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Deficiency of endothelial FGFR1 signaling via upregulation of ROCK2 activity aggravated ALI/ARDS

Vascular leakage and inflammation are pathological hallmarks of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Endothelial cells (ECs) serve as a semipermeable barrier and play a key role in disease progression. It is well known that fibroblast growth factor receptor 1 (FGFR1) is required for maintaining vascular integrity. However, how endothelial FGFR1 functions in ALI/ARDS remains obscure. Here, we revealed that conditional deletion of endothelial FGFR1 aggravated LPS-induced lung injury, including inflammation and vascular leakage. Inhibition of its downstream Rho-associated coiled-coil–forming protein kinase 2 (ROCK2) by AAV Vec-tie-shROCK2 or its selective inhibitor TDI01 effectively attenuated inflammation and vascular leakage in a mouse model. In vitro, TNFα-stimulated human umbilical vein endothelial cells (HUVECs) showed decreased FGFR1 expression and increased ROCK2 activity. Furthermore, knockdown of FGFR1 activated ROCK2 and thus promoted higher adhesive properties to inflammatory cells and higher permeability in HUVECs. TDI01 effectively suppressed ROCK2 activity and rescued the endothelial dysfunction. These data demonstrated that the loss of endothelial FGFR1 signaling mediated an increase in ROCK2 activity, which led to an inflammatory response and vascular leakage in vivo and in vitro. Moreover, inhibition of ROCK2 activity by TDI01 provided great value and shed light on clinical translation.

Model-interpreted outcomes of artificial neural networks classifying immune biomarkers associated with severe infections in ICU

Introduction

Millions of deaths worldwide are a result of sepsis (viral and bacterial) and septic shock syndromes which originate from microbial infections and cause a dysregulated host immune response. These diseases share both clinical and immunological patterns that involve a plethora of biomarkers that can be quantified and used to explain the severity level of the disease. Therefore, we hypothesize that the severity of sepsis and septic shock in patients is a function of the concentration of biomarkers of patients.

Methods

In our work, we quantified data from 30 biomarkers with direct immune function. We used distinct Feature Selection algorithms to isolate biomarkers to be fed into machine learning algorithms, whose mapping of the decision process would allow us to propose an early diagnostic tool.

Results

We isolated two biomarkers, i.e., Programmed Death Ligand-1 and Myeloperoxidase, that were flagged by the interpretation of an Artificial Neural Network. The upregulation of both biomarkers was indicated as contributing to increase the severity level in sepsis (viral and bacterial induced) and septic shock patients.

Discussion

In conclusion, we built a function considering biomarker concentrations to explain severity among sepsis, sepsis COVID, and septic shock patients. The rules of this function include biomarkers with known medical, biological, and immunological activity, favoring the development of an early diagnosis system based in knowledge extracted from artificial intelligence.

Dimethylarginine dimethylaminohydrolase 1 protects PM2.5 exposure-induced lung injury in mice by repressing inflammation and oxidative stress

BACKGROUND

Airborne fine particulate matter with aerodynamic diameter ≤ 2.5 μm (PM_2.5) pollution is associated with the prevalence of respiratory diseases, including asthma, bronchitis and chronic obstructive pulmonary disease. In patients with those diseases, circulating asymmetric dimethylarginine (ADMA) levels are increased, which contributes to airway nitric oxide deficiency, oxidative stress and inflammation. Overexpression of dimethylarginine dimethylaminohydrolase 1 (DDAH1), an enzyme degrading ADMA, exerts protective effects in animal models. However, the impact of DDAH1/ADMA on PM_2.5-induced lung injury has not been investigated.

METHODS

Ddah1^-/- and DDAH1-transgenic mice, as well as their respective wild-type (WT) littermates, were exposed to either filtered air or airborne PM_2.5 (mean daily concentration ~ 50 µg/m³) for 6 months through a whole-body exposure system. Mice were also acutely exposed to 10 mg/kg PM_2.5 and/or exogenous ADMA (2 mg/kg) via intratracheal instillation every other day for 2 weeks. Inflammatory response, oxidative stress and related gene expressions in the lungs were examined. In addition, RAW264.7 cells were exposed to PM_2.5 and/or ADMA and the changes in intracellular oxidative stress and inflammatory response were determined.

RESULTS

Ddah1^-/- mice developed more severe lung injury than WT mice after long-term PM_2.5 exposure, which was associated with greater induction of pulmonary oxidative stress and inflammation. In the lungs of PM_2.5-exposed mice, Ddah1 deficiency increased protein expression of p-p65, iNOS and Bax, and decreased protein expression of Bcl-2, SOD1 and peroxiredoxin 4. Conversely, DDAH1 overexpression significantly alleviated lung injury, attenuated pulmonary oxidative stress and inflammation, and exerted opposite effects on those proteins in PM_2.5-exposed mice. In addition, exogenous ADMA administration could mimic the effect of Ddah1 deficiency on PM_2.5-induced lung injury, oxidative stress and inflammation. In PM_2.5-exposed macrophages, ADMA aggravated the inflammatory response and oxidative stress in an iNOS-dependent manner.

CONCLUSION

Our data revealed that DDAH1 has a marked protective effect on long-term PM_2.5 exposure-induced lung injury.

Patho-Mechanisms for Hemorrhage/Sepsis-Induced Indirect Acute Respiratory Distress Syndrome: A Role for Lung TIE1 and Its Regulation by Neutrophils

INTRODUCTION

Severe hemorrhage (Hem) has been shown to be causal for the development of extra-pulmonary/indirect acute respiratory distress syndrome (iARDS) and is associated with severe endothelial cell (EC) injury. EC growth factors, Angiopoietin (Ang)-1 and -2, maintain vascular homeostasis via tightly regulated competitive interaction with the tyrosine kinase receptor, Tie2, expressed on ECs.

OBJECTIVE

Since it has been reported that the orphan receptor, Tie1, may be able to play a role in Ang:Tie2 signaling; we chose to examine Tie1's capacity to alter the lung Ang:Tie2 interaction in response to the sequential insults of shock/sepsis (cecal ligation and puncture [CLP]), culminating in iARDS.

METHODS

Male mice were subjected to Hem alone or sequential Hem followed 24 hours later by CLP that induces iARDS. Changes in lung and/or plasma levels of Tie1, Tie2, Ang-1, Ang-2, various systemic cytokine/chemokines and indices of lung injury/inflammation were then determined. The role of Tie1 was established by intravenous administration of Tie1 specific or control siRNA at 1 h post-Hem. Alternatively, the contribution of neutrophils was assessed by pre-treating mice with anti-neutrophil antibody depletion 48 h prior to Hem.

RESULTS

Lung tissue levels of Tie1 expression elevated over the first 6 to 24 h post-Hem alone. Subsequently, we found that treatment of Hem/CLP mice with Tie1-specific siRNA not only decreased Tie1 expression in lung tissue compared to control siRNA, but, suppressed the rise in lung inflammatory cytokines, lung MPO and the rise in lung protein leak. Finally, much as we have previously shown that neutrophil interaction with resident pulmonary vascular ECs contribute significantly to Ang-2 release and EC dysfunction, central to the development of iARDS. Here, we report that depletion of neutrophils also decreased lung tissue Tie1 expression and increased Tie2 activation in Hem/CLP mice.

CONCLUSION

Together, these data imply that shock-induced increased expression of Tie1 can contribute to EC activation by inhibiting Ang:Tie2 interaction, culminating in EC dysfunction and the development of iARDS.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

Exosomal hsa_circRNA_104484 and hsa_circRNA_104670 may serve as potential novel biomarkers and therapeutic targets for sepsis

In order to explore the role of exosomal circRNAs in the occurrence and development of sepsis, we looked for potential diagnostic markers to accurately identify sepsis and to lay a molecular basis for precise treatment. Ultracentrifugation was used to extract exosomes from the serum of patients with sepsis and healthy individuals. Then, changes in circRNA expression in exosomes were studied by circRNA microarray analysis. Gene ontology (GO) analysis and Kyoto City Encyclopaedia of Genes and Genomes (KEGG) pathway analysis were used to annotate the biological functions and pathways of genes, and a circRNA-miRNA-mRNA regulatory network was constructed. In the microarray analysis, 132 circRNAs were significantly differentially expressed, including 80 and 52 that were upregulated and downregulated, respectively. RT-qPCR verified the results of microarray analysis: hsa_circRNA_104484 and hsa_circRNA_104670 were upregulated in sepsis serum exosomes. ROC analysis showed that hsa_circRNA_104484 and hsa_circRNA_104670 in serum exosomes have the potential to be used as diagnostic markers for sepsis. The circRNA-miRNA-mRNA network predicted the potential regulatory pathways of differentially expressed circRNAs. There are differences in the expression of circRNA in serum exosomes between patients with sepsis and healthy individuals, which may be involved in the occurrence and development of the disease. Among them, elevations in hsa_circRNA_104484 and hsa_circRNA_104670 could be used as novel diagnostic biomarkers and molecular therapeutic targets.

Lung Pericytes in Pulmonary Vascular Physiology and Pathophysiology

Pericytes are mesenchymal-derived mural cells localized within the basement membrane of pulmonary and systemic capillaries. Besides structural support, pericytes control vascular tone, produce extracellular matrix components, and cytokines responsible for promoting vascular homeostasis and angiogenesis. However, pericytes can also contribute to vascular pathology through the production of pro-inflammatory and pro-fibrotic cytokines, differentiation into myofibroblast-like cells, destruction of the extracellular matrix, and dissociation from the vessel wall. In the lung, pericytes are responsible for maintaining the integrity of the alveolar-capillary membrane and coordinating vascular repair in response to injury. Loss of pericyte communication with alveolar capillaries and a switch to a pro-inflammatory/pro-fibrotic phenotype are common features of lung disorders associated with vascular remodeling, inflammation, and fibrosis. In this article, we will address how to differentiate pericytes from other cells, discuss the molecular mechanisms that regulate the interactions of pericytes and endothelial cells in the pulmonary circulation, and the experimental tools currently used to study pericyte biology both in vivo and in vitro. We will also discuss evidence that links pericytes to the pathogenesis of clinically relevant lung disorders such as pulmonary hypertension, idiopathic lung fibrosis, sepsis, and SARS-COVID. Future studies dissecting the complex interactions of pericytes with other pulmonary cell populations will likely reveal critical insights into the origin of pulmonary diseases and offer opportunities to develop novel therapeutics to treat patients afflicted with these devastating disorders. © 2021 American Physiological Society. Compr Physiol 11:2227-2247, 2021.

Increased Levels of VCAM-1 in Sera and VLA-4 Expression on Neutrophils in Dermatomyositis with Interstitial Lung Disease

Vascular cell adhesion molecule-1 (VCAM-1) and its ligand very late antigen (VLA-4) play important roles in many autoimmune diseases. Our study aimed to investigate the serum level of VCAM-1 and VLA-4 expression on peripheral blood neutrophil surface in patients with dermatomyositis (DM), especially focusing on patients with interstitial lung disease (ILD). Blood specimens of 42 patients with DM and 42 healthy controls matched for age and gender were recruited. Total serum VCAM-1 level was measured using commercial enzyme-linked immunosorbent assay (ELISA) and the percentages of VLA-4 expression on neutrophils were analyzed by flow cytometry. We divided patients into subgroups according to whether they had ILD and whether they exhibited diffuse alveolar damage (DAD) via high-resolution computed tomography (HRCT). sVCAM-1 was increased in classical DM (cDM) and clinical amyopathic dermatomyositis (CADM) compared with healthy controls (both p < .01). DM-ILD had higher sVCAM-1 levels than the none-ILD group (p < .01). sVCAM-1 was also significantly increased in the DAD group compared to the none-DAD group (p < .01). The percentages of VLA-4 expression on neutrophils in cDM and CADM patients were significantly elevated than that in healthy controls (both p < .01). The percentage of VLA-4 expression on neutrophils in DM patients with ILD was higher than none-ILD group (p < .01). In the patients with ILD, DAD group had a higher percentage of VLA-4 expression on neutrophils than none-DAD group (p < .01). Our findings indicated that serum VCAM-1 levels combined with VLA-4 expression on neutrophils might be useful for detecting the severity of lung disease in patients with DM.

Panton-valentine leucocidin carrying Staphylococcus aureus causing necrotizing pneumonia inactivates the JAK/STAT signaling pathway and increases the expression of inflammatory cytokines

PURPOSE

Methicillin-resistant Staphylococcus aureus (MRSA) carrying Panton-Valentine leukocidin, a pore-forming toxin, is a common cause of necrotizing pneumonia. However, the early pulmonary inflammatory response following PVL(+) MRSA infection is unknown. The purpose of this study was to use a murine model to determine the effect of PVL(+) MRSA on lung tissues and the expression of cytokines and JAK and STAT mRNA and protein.

METHODS

Mice were randomly divided into 3 groups and intra-nasally treated with PBS (control group), recombinant PVL (rPVL group), and PVL(+) MRSA (PVL group). At 24 and 48 h after inoculation, bronchoalveolar lavage fluid (BALF) was tested for cytokine levels, and lung tissues were tested for JAK and STAT mRNA and protein expression, and examined after hematoxylin and eosin staining.

RESULTS

Mice infected with the PVL(+) strain became ill, characterized by impaired mobility, hunched posture, ruffled fur, and labored breathing. Lung tissue exhibited tissue necrosis and hemorrhage. BALF levels of IL-8, TNF-α, IFN-γ, IL-12, sICAM-1, and sVCAM-1 were increased in the rPVL or PVL groups, while levels of IL-10 and IL-4 levels were similar among the groups. JAK1 and STAT1 mRNA expression and protein levels were increased in lung tissue from mice infected with PVL(+) MRSA and rPVL.

CONCLUSIONS

PVL is a significant S. aureus virulence factor, and upregulates the expression of proinflammatory cytokines but does not affect the expression of anti-inflammatory cytokines. The effect of PVL may be due to JAK/STAT pathway activation. Blockade of the JAK/STAT pathway may decrease the severity of PVL(+) MRSA pneumonia.

ICAM-1: A master regulator of cellular responses in inflammation, injury resolution, and tumorigenesis

ICAM-1 is a cell surface glycoprotein and an adhesion receptor that is best known for regulating leukocyte recruitment from circulation to sites of inflammation. However, in addition to vascular endothelial cells, ICAM-1 expression is also robustly induced on epithelial and immune cells in response to inflammatory stimulation. Importantly, ICAM-1 serves as a biosensor to transduce outside-in-signaling via association of its cytoplasmic domain with the actin cytoskeleton following ligand engagement of the extracellular domain. Thus, ICAM-1 has emerged as a master regulator of many essential cellular functions both at the onset and at the resolution of pathologic conditions. Because the role of ICAM-1 in driving inflammatory responses is well recognized, this review will mainly focus on newly emerging roles of ICAM-1 in epithelial injury-resolution responses, as well as immune cell effector function in inflammation and tumorigenesis. ICAM-1 has been of clinical and therapeutic interest for some time now; however, several attempts at inhibiting its function to improve injury resolution have failed. Perhaps, better understanding of its beneficial roles in resolution of inflammation or its emerging function in tumorigenesis will spark new interest in revisiting the clinical value of ICAM-1 as a potential therapeutic target.

The protective effects of angiotensin-converting enzyme inhibitor against cecal ligation and puncture-induced sepsis via oxidative stress and inflammation

AIMS

Sepsis is a severe public health problem affecting millions of individuals, with global mortality rates caused by lower respiratory tract infections are approximately 2.38 million people a year die from respiratory failure caused by infection. Although ACE is known to contribute to damage in septicemia, the pathophysiological mechanisms of sepsis remain unclear. While mortality can be significantly reduced through effective and sensitive antibiotic therapy, antibiotic resistance restricts the use of these drugs, and the investigation of novel agents and targets is therefore essential. Our aim was to determine whether Perindopril (PER) has anti-inflammatory and antioxidant capable of preventing these adverse conditions resulting in injury in previous studies.

MAIN METHODS

Sprague Dawley rats were randomly assigned into the control group, received oral saline solution alone for four days. the cecal ligation and puncture (CLP) group, underwent only cecal ligation and puncture induced sepsis, while the CLP + PER (2 mg/kg) underwent cecal ligation and puncture-induced sepsis together with oral administration of 2 mg/kg PER for four days before induction of sepsis.

KEY FINDINGS

Malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), Caspase-3 and nuclear factor kappa B (NF-kβ/p65) levels increased in the CLP group. On the other hand, PER (2 mg/kg) oral administration to septic rats decreased MDA, TNF-α and increase glutathione (GSH) in the lung tissue. In addition, PER administration also decreased the lung tissue NF-κB and Caspase-3 immunopositivity against sepsis.

SIGNIFICANCE

PER treatment may represent a promising means of preventing sepsis-induced lung injury via antioxidant and anti-inflammation effects.

Ablation of endothelial Pfkfb3 protects mice from acute lung injury in LPS-induced endotoxemia

Acute lung injury (ALI) is one of the leading causes of death in sepsis. Endothelial inflammation and dysfunction play a prominent role in development of ALI. Glycolysis is the predominant bioenergetic pathway for endothelial cells (ECs). However, the role of EC glycolysis in ALI of sepsis remains unclear. Here we show that both the expression and activity of PFKFB3, a key glycolytic activator, were markedly increased in lipopolysaccharide (LPS)-treated human pulmonary arterial ECs (HPAECs) in vitro and in lung ECs of mice challenged with LPS in vivo. PFKFB3 knockdown significantly reduced LPS-enhanced glycolysis in HPAECs. Compared with LPS-challenged wild-type mice, endothelial-specific Pfkfb3 knockout (Pfkfb3^ΔVEC) mice exhibited reduced endothelium permeability, lower pulmonary edema, and higher survival rate. This was accompanied by decreased expression of intracellular adhesion molecule-1 (Icam-1) and vascular cell adhesion molecule 1 (Vcam-1), as well as decreased neutrophil and macrophage infiltration to the lung. Consistently, PFKFB3 silencing or PFKFB3 inhibition in HPAECs and human pulmonary microvascular ECs (HPMVECs) significantly downregulated LPS-induced expression of ICAM-1 and VCAM-1, and monocyte adhesion to human pulmonary ECs. In contrast, adenovirus-mediated PFKFB3 overexpression upregulated ICAM-1 and VCAM-1 expression in HPAECs. Mechanistically, PFKFB3 silencing suppressed LPS-induced nuclear translocation of nuclear factor κB (NF-κB)-p65, and NF-κB inhibitors abrogated PFKFB3-induced expression of ICAM-1 and VCAM-1. Finally, administration of the PFKFB3 inhibitor 3PO also reduced the inflammatory response of vascular endothelium and protected mice from LPS-induced ALI. Overall, these findings suggest that targeting PFKFB3-mediated EC glycolysis is an efficient therapeutic strategy for ALI in sepsis.

Inter-α-inhibitor Ameliorates Endothelial Inflammation in Sepsis

PURPOSE

Vascular endothelial cells demonstrate severe injury in sepsis, and a reduction in endothelial inflammation would be beneficial. Inter-α-Inhibitor (IαI) is a family of abundant plasma proteins with anti-inflammatory properties and has been investigated in human and animal sepsis with encouraging results. We hypothesized that IαI may protect endothelia from sepsis-related inflammation.

METHODS

IαI-deficient or sufficient mice were treated with endotoxin or underwent complement-induced lung injury. VCAM-1 and ICAM-1 expression was measured in blood and lung as marker of endothelial activation. Human endothelia were exposed to activated complement C5a with or without IαI. Blood from human sepsis patients was examined for VCAM-1 and ICAM-1 and levels were correlated with blood levels of IαI.

RESULTS

IαI-deficient mice showed increased endothelial activation in endotoxin/sepsis- and complement-induced lung injury models. In vitro, levels of endothelial pro-inflammatory cytokines and cell growth factors induced by activated complement C5a were significantly decreased in the presence of IαI. This effect was associated with decreased ERK and NFκB activation. IαI levels were inversely associated with VCAM-1 and ICAM-1 levels in a human sepsis cohort.

CONCLUSIONS

IαI ameliorates endothelial inflammation and may be beneficial as a treatment of sepsis.

The role of the endothelium in asthma and chronic obstructive pulmonary disease (COPD)

COPD and asthma are important chronic inflammatory disorders with a high associated morbidity. Much research has concentrated on the role of inflammatory cells, such as the neutrophil, in these diseases, but relatively little focus has been given to the endothelial tissue, through which inflammatory cells must transmigrate to reach the lung parenchyma and cause damage. There is evidence that there is an abnormal amount of endothelial tissue in COPD and asthma and that this tissue and its’ progenitor cells behave in a dysfunctional manner. This article reviews the evidence of the involvement of pulmonary endothelium in COPD and asthma and potential treatment options for this.

A novel microfluidic assay reveals a key role for protein kinase C δ in regulating human neutrophil-endothelium interaction

A key step in neutrophil-mediated tissue damage is the migration of activated neutrophils across the vascular endothelium. Previously, we identified protein kinase C δ as a critical regulator of neutrophil migration in sepsis but did not identify specific steps in migration. In this study, we used our novel biomimetic microfluidic assay to delineate systematically the mechanism by which protein kinase C δ regulates individual steps in human neutrophil-endothelial interaction during inflammation. The biomimetic microfluidic assay includes a network of vascular channels, produced from in vivo images connected to a tissue compartment through a porous barrier. HUVECs cultured in vascular channels formed a complete lumen under physiologic shear flow. HUVECs were pretreated with TNF-α ± a protein kinase C δ inhibitor, and the tissue compartment was filled with a chemoattractant (fMLP or IL-8). Under physiologic shear flow, the role of protein kinase C δ on spatial and temporal neutrophil adherence/migration was quantified. Protein kinase C δ inhibition significantly reduced neutrophil adhesion in response to fMLP and IL-8 only under low shear rate and near bifurcations. Protein kinase C δ inhibition also decreased adherence to nonactivated HUVECs in response to fMLP or IL-8. Protein kinase C δ inhibition reduced neutrophil migration into the tissue compartment in response to fMLP and to a lesser degree, to IL-8. Antibody-coated microparticles demonstrated that protein kinase C δ inhibition down-regulated E-selectin and ICAM-1 but not VCAM-1 expression. With the use of a physiologically relevant in vitro model system, we demonstrate that protein kinase C δ plays an important role in the regulation of neutrophil adherence/migration during inflammation and identifies key steps regulated by protein kinase C δ in neutrophil-endothelial interactions.

Endotoxin tolerance drives neutrophil to infectious site

The objective of this randomized animal study and laboratory investigation was to investigate whether lipopolysaccharide tolerance redirects neutrophil migration between organs. Male BALB/c mice received subcutaneous injections of lipopolysaccharide (1 mg/kg) for 5 days, followed by cecal ligation and puncture (CLP). Cytokines and adhesion molecules were measured after tolerance and CLP challenge. Increased numbers of neutrophils were observed in the peritoneal cavity of tolerant mice, which was associated with increased levels of adhesion molecules and chemokines. In contrast, nontolerant mice accumulated higher numbers of neutrophils in the lungs compared with those in the peritoneal cavity. Neutrophil function accessed by hydrogen peroxide production from neutrophils recovered from peritoneal cavity showed that tolerance increased the capacity to produce hydrogen peroxide. Mortality was reduced in tolerant animals. This study demonstrated that tolerance reduces leukocyte accumulation in the lung after CLP by redirecting neutrophils to the site of infection.

Neutrophil migration under normal and sepsis conditions

Neutrophil migration is critical for pathogen clearance and host survival during severe sepsis. Interaction of neutrophil adhesion receptors with ligands on endothelial cells results in firm adhesion of the circulating neutrophils, followed by neutrophil activation and directed migration to sites of infection through the basement membrane and interstitial extracellular matrix. Proteolytic enzymes and reactive oxygen species are produced and released by neutrophils in response to a variety of inflammatory stimuli. Although these mediators are important for host defense, they also promote tissue damage. Excessive neutrophil migration during the early stages of sepsis may lead to an exaggerated inflammatory response with associated tissue damage and subsequent organ dysfunction. On the other hand, dysregulation of migration and insufficient migratory response that occurs during the latter stages of severe sepsis contributes to neutrophils' inability to contain and control infection and impaired wound healing. This review discusses the major steps and associated molecules involved in the balance of neutrophil trafficking, the precise regulation of which during sepsis spells life or death for the host.

Intercellular adhesion molecule 1 and progression of percent emphysema: the MESA Lung Study

BACKGROUND

Endothelial intercellular adhesion molecule (ICAM) 1 binds neutrophils and facilitates their transmigration into the lung; E-selectin facilitates leukocyte rolling. As neutrophils contribute to tissue destruction in emphysema and chronic obstructive pulmonary disease, we hypothesized that soluble ICAM-1 (sICAM-1) and E-selectin (sE-selectin) would be associated with longitudinal progression of emphysema and lung function decline.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) enrolled participants 45-84 years old without clinical cardiovascular disease in 2000-02. The MESA Lung Study assessed percent emphysema (<-950 Hounsfield units) on cardiac (2000-07) and full-lung CT scans (2010-12), and spirometry was assessed twice over five years. sICAM-1 and sE-selectin were measured at baseline. Mixed-effect models adjusted for demographics, anthropometry, smoking, C-reactive protein, sphingomyelin and scanner factors.

RESULTS

Among 1865 MESA Lung participants with measurement of sICAM-1 and percent emphysema the mean log-sICAM-1 was 5.5 ± 0.3 ng/mL and percent emphysema increased 0.73 percentage points (95% CI: 0.34, 1.12; P < 0.001) over ten years. A one SD increase in sICAM-1 was associated with an accelerated increase in percent emphysema of 0.23 percentage points over ten years (95% CI: 0.06, 0.39; P = 0.007). No significant association was found for sE-selectin, or between any adhesion molecule and lung function.

CONCLUSIONS

Higher levels of sICAM-1 were independently associated with progression of percent emphysema in a general population sample.

Nonhematopoietic β-Arrestin-1 inhibits inflammation in a murine model of polymicrobial sepsis

β-Arrestin-1 (βArr1), a scaffolding protein critical in G-protein coupled receptor desensitization has more recently been found to be important in the pathogenesis of various inflammatory diseases. We sought to understand the role of βArr1 in sepsis pathogenesis using a mouse model of polymicrobial sepsis. Although in previous studies we established that βArr1 deficiency protects mice from endotoxemia, here we demonstrate that the absence of βArr1 remarkably renders mice more susceptible to mortality in polymicrobial sepsis. In accordance with the mortality pattern, early production of inflammatory mediators was markedly enhanced in βArr1 knockout mice systemically and locally in various organs. In addition, enhanced inflammation in the heart was associated with increased NFκB activation. Compared to these effects, immune cell infiltration, thymic apoptosis, and immune suppression during polymicrobial sepsis were unaffected by a deficiency of βArr1. Additionally, enhanced inflammation and consequent higher mortality were not observed in heterozygous mice, suggesting that one allele of βArr1 was sufficient for this protective negative regulatory role. We further demonstrate that, unexpectedly, βArr1 in nonhematopoietic cells is critical and sufficient for inhibiting sepsis-induced inflammation, whereas hematopoietic βArr1 is likely redundant. Taken together, our results reveal a novel and previously unrecognized negative regulatory role of the nonhematopoietic βArr1 in sepsis-induced inflammation.

New approaches to the study of sepsis

Models of sepsis have been instructive in understanding the sequence of events in animals and, to an extent, in humans with sepsis. Events developing early in sepsis suggest that a hyperinflammatory state exists, accompanied by a buildup of oxidants in tissues reflective of a redox imbalance. Development of immunosuppression and degraded innate and adaptive immune responses are well-established complications of sepsis. In addition, there is robust activation of the complement system, which contributes to the harmful effects of sepsis. These events appear to be associated with development of multiorgan failure. The relevance of animal models of sepsis to human sepsis and the failure of human clinical trials are discussed, together with suggestions as to how clinical trial design might be improved.

Bacteremia during neutropenia is a predictive factor for invasive fungal infection in children

BACKGROUND

Invasive fungal infection (IFI) is a critical complication in the management of hematologic and malignant disease. Given that there is a tendency for IFI to occur after bacteremia following febrile episodes during neutropenia, the aim of this study was to determine if bacteremia was a predictive factor for IFI in pediatric patients with hematologic and malignant disease.

METHODS

Sixty-two patients (32 boys, 30 girls; median age, 4 years) with hematologic or malignant disease who had received chemotherapy, immunosuppressive therapy, and/or hematopoietic stem cell transplantation, and experienced febrile episodes during neutropenia were enrolled. In patient-based analysis, clinical features of 62 patients were compared between those with and without IFI. Meanwhile, in febrile episode-based analysis, clinical features were analyzed for 268 febrile episodes occurring during neutropenia in the 62 patients.

RESULTS

Patient-based analysis showed that relapse of original disease and acute myeloid leukemia were risk factors for IFI. Meanwhile, febrile episode-based analysis identified bacteremia following febrile episodes during neutropenia as a potential risk factor for IFI.

CONCLUSIONS

This is the first report to identify bacteremia following febrile episodes during neutropenia as a predictive factor for IFI in pediatric patients with hematologic or malignant disease. When bacteremia is detected in such patients, sufficient preventive measures against IFI, including intensive use of antifungal agents, are warranted.

A historical perspective on sepsis

In North America, approximately 700,000 cases of sepsis occur each year, with mortality ranging between 30% and 50%. The American Journal of Pathology has featured numerous articles on the topic, revealing mechanistic insights gleaned from both experimental rodent models and human sepsis. Nonetheless, there remains urgent need to determine the basis for sepsis-related complications and how they can be avoided, as well as how they can be most effectively treated once recognized. This historical perspective reviews what we currently understand about the mechanisms of sepsis, as well as the barriers that remain in our treatment strategies.

Inhibition of mammalian target of rapamycin augments lipopolysaccharide-induced lung injury and apoptosis

Acute lung injury during bacterial infection is associated with neutrophilic inflammation, epithelial cell apoptosis, and disruption of the alveolar-capillary barrier. TLR4 is required for lung injury in animals exposed to bacterial LPS and initiates proinflammatory responses in part via the transcription factor NF-κB. Ligation of TLR4 also initiates a proapoptotic response by activating IFN-β and STAT1-dependent genes. We recently demonstrated that mammalian target of rapamycin (mTOR), a key controller of cell growth and survival, can physically interact with STAT1 and suppress the induction of STAT1-dependent apoptosis genes. We therefore hypothesized that the mTOR inhibitor rapamycin would increase LPS-induced apoptosis and lung injury in vivo. Rapamycin increased lung injury and cellular apoptosis in C57BL/6J mice exposed to intratracheal LPS for 24 h. Rapamycin also augmented STAT1 activation, and the induction of STAT1-dependent genes that mediate cellular apoptosis (i.e., Fas, caspase-3). LPS-induced lung injury was attenuated in STAT1 knockout mice. In addition, LPS and IFN-β-induced apoptosis was absent in cultured cells lacking STAT1, and, unlike in wild-type cells, a permissive effect of rapamycin was not observed. In contrast to its effect on STAT1, rapamycin inhibited NF-κB activation in vivo and reduced selected markers of inflammation (i.e., neutrophils in the bronchoalveolar lavage fluid, TNF-α). Therefore, although it inhibits NF-κB and neutrophilic inflammation, rapamycin augments LPS-induced lung injury and apoptosis in a mechanism that involves STAT1 and the induction of STAT1-dependent apoptosis genes.

Angiopoietin-1 and angiopoietin-2 as clinically informative prognostic biomarkers of morbidity and mortality in severe sepsis

OBJECTIVE

To determine the utility of angiopoietin-1 and angiopoietin-2 as potentially novel biomarkers of morbidity and mortality in patients with severe sepsis.

DESIGN

Multicenter longitudinal cohort study.

SETTING

Three tertiary hospital intensive care units in Hamilton, Ontario, Canada.

PATIENTS

A total of 70 patients with severe sepsis were enrolled within 24 hrs of meeting the inclusion criteria for severe sepsis and followed until day 28, hospital discharge, or death.

INTERVENTIONS

Clinical data and plasma samples were obtained at intensive care unit admission for all 70 patients and then daily for 1 wk and weekly thereafter for a subset of 43 patients. Levels of angiopoietin-1 and angiopoietin-2 in stored plasma samples were measured and compared with clinical characteristics, including the primary outcomes of 28-day mortality and morbidity measured by the Multiple Organ Dysfunction score.

MEASUREMENTS AND MAIN RESULTS

Lower angiopoietin-1 plasma levels (≤ 5.5 ng/mL) at admission were associated with increased likelihood of death (relative risk 0.49 [95% confidence interval of 0.25-0.98], p = .046). Lower angiopoietin-1 levels remained a significant predictor of 28-day mortality in a multiple logistic regression model (adjusted odds ratio of 0.282 [95% confidence interval of 0.086-0.93], p = .037). Analysis of serial data using linear mixed models confirmed that sepsis survivors had higher levels of angiopoietin-1 (p = .012) and lower daily levels of angiopoietin-2 (p = .022) than nonsurvivors. Furthermore, survivors had higher peak angiopoietin-1 levels (median 13 vs. 10 ng/mL, p = .019) and lower nadir angiopoietin-2 levels (median 2.8 vs. 6.2 ng/mL, p = .013) than nonsurvivors. A score incorporating angiopoietin-1 and angiopoietin-2 and three other markers of endothelial activation discriminated with high accuracy between fatal and nonfatal cases (c-index of 0.80 [95% confidence interval of 0.69-0.90], p < .001). Plasma levels of angiopoietin-2 correlated with clinical markers of organ dysfunction and molecular markers of endothelial cell activation.

CONCLUSIONS

Angiopoietin-1 levels at admission and both angiopoietin-1 and angiopoietin-2 levels measured serially correlated with 28-day mortality in severe sepsis. Angiopoietin-2 levels also correlated with organ dysfunction/injury and a validated clinical sepsis score. These results suggest the use of angiopoietins as clinically informative biomarkers of disease severity and patient outcome in severe sepsis.

The harmful role of c5a on innate immunity in sepsis

There is accumulating evidence in humans and in experimental sepsis that robust activation of the complement system occurs along with development of defects in the innate immune system. In this report we review evidence that the complement activation product, C5a, appears in the plasma of rodents following cecal ligation and puncture (CLP). C5a interacts with its receptors (C5aR, C5L2) on phagocytes (polymorphonuclear neutrophils, PMNs, macrophages), ultimately paralyzing the ERK1/2 pathway of the mitogen-activated protein kinase signaling pathway. C5a is also interactive with its receptors on a variety of other cell types in various organs. Interaction of C5a with receptors on PMNs results in compromised innate immunity, with intense suppression of phagocytosis, chemotaxis and the respiratory burst. Endothelial cells acquire a pro-inflammatory phenotype (increased ICAM-1 and tissue factor expression), while macrophages are primed and produce large amounts of cytokines/chemokines. All of these outcomes are C5a and C5a receptor dependent. CLP also unleashes activation of clotting (and fibrinolytic) factors in a C5a-dependent manner. Finally, thymocytes upregulate C5aR and react with C5a, resulting in apoptosis via the intrinsic (mitochondrial) pathway. Collectively, these findings suggest that interception of C5a in sepsis preserves innate immune functions and may be a strategy for treatment of septic humans.

Ninjurin1: a potential adhesion molecule and its role in inflammation and tissue remodeling

Nerve injury induced protein 1, Ninj1 (Ninjurin1) is a cell surface protein that is induced by nerve injury and promotes axonal growth in the peripheral nervous system. However, the function of Ninj1 in the vascular system and central nervous system (CNS) is incompletely understood. Here we review recent studies that have shed further light on the role and regulation of Ninj1 in vascular remodeling and inflammation. Increasing evidence suggests that Ninj1 mediates cell communication and enhances the entry, migration, and activity of leukocytes such as monocytes and macrophages in developmental processes and inflammatory responses. Moreover, our recent studies show that Ninj1 regulates close interaction between leukocytes and vascular endothelial cells in vascular remodeling and inflamed CNS. Additionally, Ninj1 enhances the apoptosis-inducing activity of leukocytes and is cleaved by MMPs, resulting in loss of adhesion during tissue remodeling. The collective data described here show that Ninj1 is required for the entry, adhesion, activation, and movement of leukocytes during tissue remodeling and might be a potential therapeutic target to regulate the adhesion and trafficking of leukocytes in inflammation and leukocyte-mediated diseases such as multiple sclerosis, diabetic retinopathy, and neuropathy.

Obesity Exacerbates Sepsis-Induced Inflammation and Microvascular Dysfunction in Mouse Brain

OBJECTIVE

Obese patients with sepsis have higher morbidity and mortality than lean counterparts, but the mechanisms involved are unknown. The authors examined the inflammatory and thrombogenic responses of the cerebral microvasculature to sepsis induced by cecal ligation and perforation in obese and lean wild-type mice.

METHODS

Leukocyte and platelet adhesion in cerebral microvasculature and behavioral responses were measured in wild-type and obese mice 4 h postperforation. P-selectin expression in different vascular beds was assessed 6 h postperforation. The effects of immunoblockade of P-selectin, ICAM-1, and CD18 on leukocyte and platelet recruitment were evaluated in obese septic animals.

RESULTS

Cerebral venules of obese and wild-type mice assumed a proinflammatory and prothrombogenic phenotype 4 h post-perforation, with greatly exaggerated responses in obese mice compared to the lean counterparts. These enhanced responses were attenuated by blocking P-selectin, CD18, or ICAM-1. Obese mice also exhibited a more profound behavioral deficit after sepsis, which appears to be unrelated to the recruitment of leukocytes and platelets. Cecal ligation and perforation-induced P-selectin expression was greater in obese mice compared with lean counterparts.

CONCLUSIONS

These findings suggest that the increased morbidity to sepsis in obesity may result from exaggerated microvascular inflammatory and thrombogenic responses that include the activation of endothelial cells with subsequent expression of adhesion molecules, such as P-selectin.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSIONS AND IMPLICATIONS

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

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

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

Aspergillus fumigatus stimulates leukocyte adhesion molecules and cytokine production by endothelial cells in vitro and during invasive pulmonary disease

Invasive aspergillosis is characterized by hyphal invasion of the blood vessels, which contributes to the pathogenesis of this disease. During this angioinvasion, Aspergillus fumigatus interacts with the endothelial cell lining of the blood vessels. We investigated the response of vascular endothelial cells to A. fumigatus infection in vitro and in mouse models of invasive pulmonary aspergillosis. Infection with hyphae, but not with conidia, stimulated endothelial cells to synthesize E-selectin, vascular cell adhesion molecule 1 (VCAM-1), interleukin 8, and tumor necrosis factor alpha (TNF-alpha) in vitro. Killed hyphae induced approximately 40% less stimulation than did live hyphae. Endothelial cell stimulation required contact between the hyphae and endothelial cells but not endocytosis of the organisms. Studies with DeltagliP and DeltastuA null mutants of A. fumigatus indicated that the extent of endothelial cell stimulation was not influenced by gliotoxin or other StuA-dependent factors synthesized by A. fumigatus. In neutropenic mice infected with wild-type A. fumigatus, increased pulmonary expression of E-selectin, cytokine-induced neutrophil chemoattractant (KC), and TNF-alpha occurred only when neutropenia had resolved. In nonneutropenic mice immunosuppressed with corticosteroids, A. fumigatus stimulated earlier pulmonary expression of E-selectin, VCAM-1, and KC, while expression of intercellular adhesion molecule 1 and TNF-alpha was suppressed. In both mouse models, expression of E-selectin and KC was associated with high pulmonary fungal burden, angioinvasion, and neutrophil adherence to endothelial cells. Therefore, the expression of leukocyte adhesion molecules and secretion of proinflammatory cytokines by endothelial cells in response to A. fumigatus could enhance the host defense against this organism by contributing to the recruitment of activated leukocytes to sites of angioinvasion.

An age-associated increase in pulmonary inflammation after burn injury is abrogated by CXCR2 inhibition

Burn patients over the age of 60 are at a greater risk for developing pulmonary complications than younger patients. The mechanisms for this, however, have yet to be elucidated. The objective of this study was to determine whether increased chemoattraction plays a role in the age-related differences in pulmonary inflammation after burn injury. At 6 or 24 h after receiving sham or 15% total body surface area scald injury, lungs from young and aged mice were analyzed for leukocyte content by histological examination and immunostaining. Lungs were then homogenized, and levels of neutrophil chemokines, MIP-2 and KC, were measured. At 6 h after burn, the number of neutrophils was four times higher in the lungs of both burn groups compared with aged-matched controls (P<0.05), but no age difference was evident. At 24 h, in contrast, neutrophils returned to sham levels in the lungs of young, burn-injured mice (P<0.05) but did not change in the lungs of aged, burn-injured mice. Pulmonary levels of the neutrophil chemokine KC but not MIP-2 were consistently three times higher in aged, burn-injured mice compared with young, burn-injured mice at both time-points analyzed. Administration with anti-CXCR2 antibody completely abrogated the excessive pulmonary neutrophil content by 24 h (P<0.05), while not affecting the inflammatory response of the wounds. These studies show that CXCR2-mediated chemoattraction is involved in the pulmonary inflammatory response after burn and suggest that aged individuals sustaining a burn injury may benefit from treatment strategies that target neutrophil chemokines.

Role of oxidants in lung injury during sepsis

The role of oxidative stress has been well appreciated in the development of sepsis-induced acute lung injury (ALI). Oxidative stress in sepsis-induced ALI is believed to be initiated by products of activated lung macrophages and infiltrated neutrophils, promptly propagating to lung epithelial and endothelial cells. This leads to tissue damage and organ dysfunction. On stimulation, neutrophils (PMNs) enable their migration machinery. The lung undergoes changes favoring adhesion and transmigration of PMNs, resulting in PMN accumulation in lung, which is a characteristic of sepsis-induced ALI. Oxidative stress turns on the redox-sensitive transcription factors (NF-kappaB, AP-1), resulting in a large output of proinflammatory cytokines and chemokines, which further aggravate inflammation and oxidative stress. During the process, transcription factor nuclear factor-erythroid 2-p45-related factor 2 (Nrf2) and heme oxygenase (HO) appear to play the counterbalancing roles to limit the propagation of oxidative stress and inflammatory responses in lung. Many antioxidants have been tested to treat sepsis-induced ALI in animal models and in patients with sepsis. However, the results are inconclusive. In this article, we focus on the current understanding of the pathogenesis of sepsis-induced ALI and novel antioxidant strategies for therapeutic purposes.

Acute inflammation decreases the expression of connexin 40 in mouse lung

Transmigration of neutrophil polymorphonuclear leukocytes through the microvascular endothelium is a cardinal event of acute inflammation. In vitro, this process can be restricted by gap junctional intercellular communication, but whether it also occurs in vivo is unknown. Connexin 40 (Cx40) is a gap junctional protein abundantly present in the lung, notably in vascular endothelium. We hypothesized that acute lung inflammation would be aggravated in knockout mice genetically deficient in Cx40. This hypothesis was tested in two different models: 1) intranasal instillation of LPS at either supramaximal (50 microg/mouse) or inframaximal dose (0.01 microg/mouse) and 2) pulmonary inflammation as a distant consequence of an abdominal infection caused by cecal ligation and perforation. Pulmonary transmigration of neutrophils was assessed by counting these cells in bronchoalveolar lavage fluid (LPS model) or with the myeloperoxidase assay in homogenates of blood-free tissue (cecal ligation and perforation model). Pulmonary content in Cx40 and Cx43 was evaluated with immunoblots. In wild-type mice, there was a time-dependent decrease of Cx40 expression in both models. The time points for studies with the knockout mice were chosen in such a manner that inflammation was clearly present and Cx40 still largely expressed in wild-type animals. In either model, the development of lung inflammation did not differ between wild-type and Cx40-deficient mice. In conclusion, the pulmonary expression of the Cx40 protein is progressively and markedly decreased in two different murine models of acute lung inflammation, but there is no causal relationship between this process and the pulmonary transmigration of neutrophils.

Stress molecules in sepsis and systemic inflammatory response syndrome

During sepsis, microbial derived products ("pathogen-associated molecular patterns", PAMPs) are recognized as exogenous danger signals by specific sensors of the host ("pattern recognitions receptors", PRRs). This interaction leads to the release of numerous stress proteins that are a prerequisite to fight infection, though their overzealous production can contribute to tissue damage, organ dysfunction and eventually death. In critically ill patients, translocation of PAMPs can occur from the gut, and injured tissues and cells release endogenous danger signals called "alarmins" (e.g. High mobility group box-1); that share some properties with PAMPs. Thus, numerous similarities occur during infectious and non-infectious systemic inflammation.

BETA-GLUCAN ATTENUATES INFLAMMATORY CYTOKINE RELEASE AND PREVENTS ACUTE LUNG INJURY IN AN EXPERIMENTAL MODEL OF SEPSIS

Sepsis is one of the most important risk factors in acute respiratory distress syndrome (ARDS). beta-Glucan is a potent reticuloendothelial modulating agent, the immunobiological activity of which is mediated in part by an increase in the number and function of macrophages. In this study, we investigated the putative protective role of beta-glucan against sepsis-induced lung injury. Sepsis was induced by cecal ligation and puncture (CLP) in Wistar rats. The control group received saline, and the treatment groups received beta-glucan or beta-glucan + beta-1,3-D-glucanase. Five hours thereafter, plasma tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta, and IL-6 levels were determined. Presence of lung injury was determined via lung tissue myeloperoxidase (MPO) activity, intercellular adhesion molecule (ICAM) 1 levels, and histopathological examination at 18 h after CLP. In a separate set of experiments, survival was monitored for 7 days after CLP. beta-Glucan treatment led to a significant increase in survival rate (63% in glucan-treated rats vs 38% in saline-treated rats). Administration of the beta-glucan inhibitor abrogated beta-glucan's survival benefit (50%). After CLP, plasma TNF-alpha, IL-1beta, and IL-6 concentrations were increased in control animals. When beta-glucan was administered, it completely blocked the elevation of TNF-alpha, IL-1beta, and IL-6. Administration of beta-1,3-D-glucanase suppressed glucan-induced decrease in cytokines. Animals treated with beta-glucan showed a significant reduction in lung injury score, a marked decrease in ICAM-1 expression, and a significant decrease in MPO levels. In contrast, beta-1,3-D-glucanase caused a significantly increased MPO and ICAM-1 levels in the lung. These data reveal that beta-glucan treatment improved the course of CLP-induced peritonitis and attenuated the lung injury. Administration of beta-glucanase inhibited the beta-glucan activity and resulted in enhanced lung injury.

Upregulation of intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 after unilateral nerve injury in the peripheral taste system

In the peripheral taste system, activated macrophages are recruited to both sides of the tongue after unilateral sectioning of the chorda tympani nerve (CT). Neural degeneration elicits macrophage entry in other systems by upregulating vascular adhesion molecules. We hypothesized that CT sectioning leads to a bilateral increase in intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 expression on lingual vessels. To test this hypothesis, rats were euthanized at time points from 6 hr to 7 days post-sectioning. Frozen sections of tongue were processed for immunohistochemical staining for ICAM-1 and VCAM-1. Tongue homogenates from additional rats were analyzed with ELISA. ICAM-1 expression increases first on the denervated side of the tongue at 24 hr post-section and then on the uninjured side at 48 hr post-section. ICAM-1 remains elevated through Day 7 post-sectioning on both sides of the tongue. Dietary sodium restriction, which prevents the macrophage response to nerve sectioning, had no effect on ICAM-1 levels. VCAM-1+ vessels are increased on the denervated side of the tongue at 24-48 hr post-section in control-fed rats. However, dietary sodium restriction prevents the increase. These results indicate that vascular adhesion molecules are differentially regulated by CT sectioning. We suggest that macrophage entry, migration, and modulation of taste function are downstream of dynamic expression of adhesion molecules.

Phenotypic Heterogeneity of the Endothelium

Endothelial cells, which form the inner cellular lining of blood vessels and lymphatics, display remarkable heterogeneity in structure and function. This is the first of a 2-part review focused on phenotypic heterogeneity of blood vessel endothelium. This review provides an historical perspective of our understanding of endothelial heterogeneity, discusses the scope of phenotypic diversity across the vascular tree, and addresses proximate and evolutionary mechanisms of endothelial cell heterogeneity. The overall goal is to underscore the importance of phenotypic heterogeneity as a core property of the endothelium.

Longitudinal course and clinical significance of TGF-beta1, sL- and sE-Selectins and sICAM-1 levels during severe acute stress in children

OBJECTIVES

To elucidate the potential role of circulating levels of transforming growth factor-beta1 (TGF-beta1), soluble intercellular adhesion molecule-1 (sICAM-1), soluble L- and sE-Selectins (sL- and sE-Selectins) in children with sepsis, traumatic brain injury (TBI) or acute respiratory distress syndrome (ARDS).

DESIGN AND METHODS

Levels of TGF-beta1, sICAM-1, L- and sE-Selectins were determined using solid-phase sandwich enzyme-linked immunosorbent assay in plasma of 10 patients with sepsis, 10 patients with TBI, 10 patients with ARDS, compared to 10 ventilated controls with chronic illness but not in acute stress, on days 1, 3, 5, 7 and 10.

RESULTS

The highest values of sICAM-1 were observed in patients with TBI (p<0.001) and those of sE-Selectin in patients with sepsis (p=0.0001). Patients in the control group did not show an elevation of sE-Selectin and sICAM-1 levels longitudinally. Increased levels of measured molecules (TGF-beta1, p<0.02, sE-Selectin, p<0.02, sL-Selectin, p=0.06, sICAM-1, p<0.03) were demonstrated among survivors in the sepsis and ARDS groups of patients and were positively correlated with length of stay (p<0.04) and mechanical ventilation (p<0.001).

CONCLUSIONS

A sustained increase of adhesion molecules occurs during acute stress in children which may contribute to morbidity in patients with sepsis (sE-Selectin) or traumatic brain injury (sICAM-1). Suppression of the expected response of sE-Selectins, s-ICAM-1 and TGF-beta1 is associated with poor outcome.