Neutrophil-endothelial Interactions Research Articles

Daño por isquemia-reperfusión miocárdico en cirugía cardiaca con circulación extracorpórea. Aspectos bioquímicos

IntroductionSince the beginning of the cardiac surgery with cardiopulmonary bypass, myocardial-reperfusion injury has been recognized as one of the leading causes of morbidity and mortality related with this type of surgery. MethodologyA bibliographic review in Pubmed and other data base including Teseo has been carried out. ResultsFundaments of the cellular changes during the ischemic time, cellular changes in the reperfusion time, release of oxygen free radicals, complement activation, proinflammatory cytokines activation and neutrophil-endothelium interaction are exposed. A table with a selected list of drugs and compounds used against the myocardial ischemic -reperfusion injury syndrome is included. ConclusionsAt present, the myocardial reperfusion injury syndrome is an active line of research. There are many trials and studies on investigating new agents .The cardiac surgeon should be well informed in new strategies in myocardial protection in cardiac surgery.155 words

Protectin D1n-3 DPA and resolvin D5n-3 DPA are effectors of intestinal protection

The resolution of inflammation is an active process orchestrated by specialized proresolving lipid mediators (SPM) that limit the host response within the affected tissue; failure of effective resolution may lead to tissue injury. Because persistence of inflammatory signals is a main feature of chronic inflammatory conditions, including inflammatory bowel diseases (IBDs), herein we investigate expression and functions of SPM in intestinal inflammation. Targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was used to identify SPMs from n-3 polyunsaturated fatty acids in human IBD colon biopsies, quantifying a significant up-regulation of the resolvin and protectin pathway compared with normal gut tissue. Systemic treatment with protectin (PD)1n-3 DPA or resolvin (Rv)D5n-3 DPA protected against colitis and intestinal ischemia/reperfusion-induced inflammation in mice. Inhibition of 15-lipoxygenase activity reduced PD1n-3 DPA and augmented intestinal inflammation in experimental colitis. Intravital microscopy of mouse mesenteric venules demonstrated that PD1n-3 DPA and RvD5n-3 DPA decreased the extent of leukocyte adhesion and emigration following ischemia-reperfusion. These data were translated by assessing human neutrophil-endothelial interactions under flow: PD1n-3 DPA and RvD5n-3 DPA reduced cell adhesion onto TNF-α-activated human endothelial monolayers. In conclusion, we propose that innovative therapies based on n-3 DPA-derived mediators could be developed to enable antiinflammatory and tissue protective effects in inflammatory pathologies of the gut.

Inflammation in Sickle Cell Disease: Differential and Down-Expressed Plasma Levels of Annexin A1 Protein.

Sickle cell disease (SCD) is an inherited hemolytic anemia whose pathophysiology is driven by polymerization of the hemoglobin S (Hb S), leading to hemolysis and vaso-occlusive events. Inflammation is a fundamental component in these processes and a continuous inflammatory stimulus can lead to tissue damages. Thus, pro-resolving pathways emerge in order to restore the homeostasis. For example there is the annexin A1 (ANXA1), an endogenous anti-inflammatory protein involved in reducing neutrophil-endothelial interactions, accelerating neutrophil apoptosis and stimulating macrophage efferocytosis. We investigated the expression of ANXA1 in plasma of SCD patients and its relation with anemic, hemolytic and inflammatory parameters of the disease. Three SCD genotypes were considered: the homozygous inheritance for Hb S (Hb SS) and the association between Hb S and the hemoglobin variants D-Punjab (Hb SD) and C (Hb SC). ANXA1 and proinflammatory cytokines were quantified by ELISA in plasma of SCD patients and control individuals without hemoglobinopathies. Hematological and biochemical parameters were analyzed by flow cytometry and spectrophotometer. The plasma levels of ANXA1 were about three-fold lesser in SCD patients compared to the control group, and within the SCD genotypes the most elevated levels were found in Hb SS individuals (approximately three-fold higher). Proinflammatory cytokines were higher in SCD groups than in the control individuals. Anemic and hemolytic markers were higher in Hb SS and Hb SD genotypes compared to Hb SC patients. White blood cells and platelets count were higher in Hb SS genotype and were positively correlated to ANXA1 levels. We found that ANXA1 is down-regulated and differentially expressed within the SCD genotypes. Its expression seems to depend on the inflammatory, hemolytic and vaso-occlusive characteristics of the diseased. These data may lead to new biological targets for therapeutic intervention in SCD.

Intravascular Inflammation Triggers Intracerebral Activated Microglia and Contributes to Secondary Brain Injury After Experimental Subarachnoid Hemorrhage (eSAH).

Activation of innate immunity contributes to secondary brain injury after experimental subarachnoid hemorrhage (eSAH). Microglia accumulation and activation within the brain has recently been shown to induce neuronal cell death after eSAH. In isolated mouse brain capillaries after eSAH, we show a significantly increased gene expression for intercellular adhesion molecule-1 (ICAM-1) and P-selectin. Hence, we hypothesized that extracerebral intravascular inflammatory processes might initiate the previously reported microglia accumulation within the brain tissue. We therefore induced eSAH in knockout mice for ICAM-1 (ICAM-1-/-) and P-selectin glycoprotein ligand-1 (PSGL-1-/-) to find a significant decrease in neutrophil-endothelial interaction within the first 7days after the bleeding in a chronic cranial window model. This inhibition of neutrophil recruitment to the endothelium results in significantly ameliorated microglia accumulation and neuronal cell death in knockout animals in comparison to controls. Our results suggest an outside-in activation of the CNS innate immune system at the vessel/brain interface following eSAH. Microglia cells, as part of the brain's innate immune system, are triggered by an inflammatory reaction in the microvasculature after eSAH, thus contributing to neuronal cell death. This finding offers a whole range of new research targets, as well as possible therapy options for patients suffering from eSAH.

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.

NEUTROPHILS AND SYSTEMIC INFLAMMATORY RESPONSE SYNDROME

The paper summarizes the data available in the literature on the mechanisms responsible for the priming and activation of neutrophils circulating in the blood bed and on the adhesion and nonadhesion mechanisms of neutrophil-endothelium interactions and describes their role in the occurrence of systemic inflammatory response syndrome. The interaction of circulating neutrophils with the activated endothelium is the central event during inflammation. It includes diverse molecular events associated with neutrophil adhesion and migration and with impaired endothelial permeability. The simultaneous overactivation of the endothelium and neutrophils may give rise to endothelial damage caused by adherent neutrophils. The cytotoxic neutrophil-endothelium interaction makes a considerable contribution to the pathogenesis of vascular and tissue injuries in circulatory disturbances and if the systemic inflammatory response syndrome develops. Impaired neutrophil migration and phagocytosis in systemic inflammatory response syndrome, the association of these impairments with neutrophil priming and activation, and the clinical value of these indicators are discussed.

Abstract T MP112: Physical Activity Improves Stroke Outcome Through Modulation of Neutrophil Polynuclear Mobilization

Introduction: Physical activity has been previously reported to decrease severity of stroke in patient cohorts. Experimentally, in rats submitted to chronic physical activity, the infarct size is decreased and functional outcome is improved, with a decrease of neutrophil polynuclear mobilization. Hypothesis: We assessed the hypothesis that beneficial effect of physical activity observed in stroke could be related to neutrophil modulation. Methods: We recruited patients with supratentorial cerebral ischemia within 48 hours of symptom onset. We evaluated the presence, weekly duration and intensity (light, moderate, heavy) of previous physical activity. The primary end-point was the initial severity assessed by the NIHSS. The secondary end-point was neutrophil polynuclear count. Myeloperoxydase, chemokines (Monocyte Chemoattractant Protein-1, C-X-C chemokine 10), adhesion proteins (InterCellular Adhesion Molecule-1, vascular cell adhesion molecule1), von Willebrand factor, cytokines (interleukins-6, -8, -10) were dosed in plasma through Luminex methodology. Results: Of the 434 patients (mean age of 67 ± 15 years, 53% of men), 227 (52.3%) had a regular physical activity before ischemic event. Previous regular physical activity was independently associated with a lower severity of ischemic event assessed by the NIHSS (4.0 [1-9] vs 6.0 [2-15] ; p<0.002) and lower concentrations of neutrophil polynuclear (5.0 [3.8-6.4] vs 5.7 [4.1-7.7]; p<0.003), chemokines, interleukins, Von Willebrand factor, and myeloperoxydase. There was no strong evidence of difference in biological parameters according to duration of physical activity. Patients with moderate and heavy intensity had a lower level of chemokines, interleukins-8 and Von Willebrand factor. Conclusion: In conclusion, previous regular physical activity improves initial stroke severity through decrease of neutrophil polynuclear count. The decrease of attractant chemokines could suggest a decreased mobilization of neutrophils to parenchyma rather than an effect on neutrophil-endothelium interaction since adhesion proteins are not changed.

S99 Effects Of Differential Tnf Receptor Signalling In Modulating Neutrophil-endothelial Interactions In The Pulmonary Microvasculature

Neutrophil recruitment into the bronchoalveolar space is central to the pathogenesis of acute respiratory distress syndrome injury (ARDS), and occurs via interaction with the lung microvascular endothelium. Tumour Necrosis Factor (TNF) is a key mediator in these processes, activating endothelial cells and inducing changes in microvascular permeability, as well as priming neutrophils (a pre-requisite for neutrophil-mediated tissue damage) and modulating neutrophil lifespan. TNF signals through two cell surface receptors, TNFR1 and TNFR2 initiating distinct signalling pathways and cellular responses. In a human in vivo model of ARDS, selective TNFR1 antagonism attenuated pulmonary inflammation (O’Kane et al , Thorax 2013; 63:A50). Using TNF receptor specific muteins and a novel highly selective TNFR1 antagonist, we investigated the role of differential TNFR signalling on neutrophil-pulmonary microvascular endothelial cell interactions. TNF-induced alterations in the expression of the neutrophil cell surface molecules CD11b, CD62L, TNFR1 and TNFR2 were all modulated via TNFR1. TNFR1 was also the dominant receptor mediating reactive oxygen species generation by TNF-primed, fMLP-stimulated neutrophils. We further examined the role of TNF receptors in modulating neutrophil apoptosis; whilst engagement of both TNFR1 and 2 was required to induce early neutrophil apoptosis, TNFR1 antagonism reversed TNF-induced late survival to constitutive levels of apoptosis. TNFR1 antagonsim of human pulmonary microvascular endothelial monolayers significantly reduced TNF-induced production of IL-1beta, IL-6 and IL-8 (p Collectively, these results suggest that TNFR1 regulates multiple components of neutrophil-endothelial interactions. Selective TNFR1 antagonism may offer a novel therapeutic approach in ARDS; phase II clinical trials of this therapy are scheduled.

Laser speckle contrast imaging for measurement of hepatic microcirculation during the sepsis: A novel tool for early detection of microcirculation dysfunction

BackgroundSepsis is a fatal systemic inflammatory response syndrome caused by severe infection. The aim of this study was to measure hepatic microcirculation during the sepsis with laser speckle contrast imaging (LSCI), as well as investigating the underlying mechanisms. MethodsSepsis was induced by cecal ligation and puncture. Rats were divided into the sham group and sepsis group. The hepatic microcirculation was monitored with LSCI. In addition, hepatic endothelial function (expression of cell adhesion molecules, coagulation and vascular permeability) and neutrophils accumulation in the liver were compared between the two groups. ResultsDuring the sepsis, hepatic microcirculation decreased dramatically (290.3±70.1 LSPU (laser speckle perfusion units) at baseline vs. 230.4±60.7 LSPU at 12h vs. 125.2±25.4 LSPU at 48h, P<0.001). The rats developed hyperbilirubinemia since 6h. In the early phase of sepsis, the accumulation of neutrophils and formation of microthrombus increased rapidly. In the late phase, hepatic neutrophils accumulation was already at its maximum level. Meanwhile, the endothelial coagulation status shifted from procoagulation to anticoagulation. The vascular leakage was involved in the microcirculation dysfunction since 12h after sepsis. ConclusionsHepatic microcirculation dysfunction occurs early during the sepsis and is associated with liver injury. This microcirculation dysfunction is due to neutrophil–endothelium interactions, microthrombus formation and vascular leakage.

ANCA-Associated Vasculitides—An Update

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides are characterized by destruction of small vessels, granulomatous inflammation of the respiratory tract and necrotizing glomerulonephritis. This review describes the clinical diagnosis and therapy as well as the patho-physiology of ANCA-associated vasculitides with a specific focus on the interplay of ANCAs with activated neutrophils and the deleterious pathophysiological consequences of neutrophil-endothelium interaction.

Involvement of the nuclear factor-κB pathway in the adhesion of neutrophils to renal tubular cells after injury induced by neonatal postasphyxial serum

Nuclear factor κB (NF-κB) plays an important role in the regulation of inflammatory proteins. However, it is unclear whether the NF-κB/intercellular adhesion molecule-1 (ICAM-1) pathway is involved in the adhesion of neutrophils and renal injury after hypoxia-ischemia (HI) in neonates. In this report we investigated whether NF-κB and its downstream molecule ICAM-1 were involved in renal injury induced by postasphyxial serum (PS) from neonates. Human renal proximal tubular (HK-2) cells were preincubated with 10% fetal calf serum (control), 20% neonatal PS, or 20% PS plus pyrolidine dithiocarbamate (PDTC). The expression of IκBα, NF-κB p65, and ICAM-1 in HK-2 cells was determined by Western blot and/or immunohistochemistry. Nuclear translocation of NF-κB p65 in HK-2 cells was detected by immunofluorescence and Western blot. The ICAM-1 mRNA was determined by RT-PCR. Then HK-2 cells were cultured with neutrophils from neonates with asphyxia. After HK-2 cells had been cultured with neutrophils, we detected myeloperoxidase (MPO) activity, the leakage rate of lactate dehydrogenase (LDH), and cell viability. We found that PS preincubation resulted in significantly decreased IκBα expression and increased expression of NF-κB and ICAM-1, and facilitated the nuclear translocation of NF-κB in HK-2 cells. PS preincubation increased MPO activity, leading to elevated leakage rates of LDH and decreased cell viability after neutrophil exposure. Furthermore, the inhibition of NF-κB activity by PDTC significantly upregulated IκBα expression, decreased NF-κB and ICAM-1 expression, downregulated the nuclear translocation of NF-κB, and decreased MPO activity. This leads to decreased leakage rates of LDH and increased cell viability after neutrophil exposure. Our findings suggest that NF-κB/ICAM-1 pathway may be involved in neutrophil-endothelial interactions and neonatal renal injury after HI.

Neutrophil-endothelial interactions mediate angiopoietin-2-associated pulmonary endothelial cell dysfunction in indirect acute lung injury in mice.

Unresolved inflammation in the lung is thought to elicit loss of endothelial cell (EC) barrier integrity and impaired lung function. We have shown, in a mouse model of shock/sepsis, that neutrophil interactions with resident pulmonary cells appear central to the pathogenesis of indirect acute lung injury (iALI). Normally, EC growth factors angiopoietin (Ang)-1 and Ang-2 maintain vascular homeostasis through tightly regulated interaction with the kinase receptor Tie2 expressed on ECs. Although Ang-1/Tie2 has been shown to promote vessel integrity, stimulating downstream prosurvival/antiinflammatory signaling, Ang-2, released from activated ECs, is reported to promote vessel destabilization. This mechanism of regulation, together with recent clinical findings that plasma Ang-2 levels are significantly elevated in patients who develop acute respiratory distress syndrome, has focused our investigation on the contribution of Ang-2 to the development of iALI. A murine model of hemorrhagic shock-induced priming for the development of iALI after subsequent septic challenge was used in this study. Our findings show that 1) Ang-2 is elevated in our experimental model for iALI, 2) direct EC/neutrophil interactions contribute significantly to EC Ang-2 release, and 3) suppression of Ang-2 significantly decreases inflammatory lung injury, neutrophil influx, and lung and plasma IL-6 and TNF-α. These findings support our hypothesis and suggest that Ang-2 plays a role in the loss of pulmonary EC barrier function in the development of iALI in mice resultant from the sequential insults of hemorrhagic shock and sepsis and that this is mediated by EC interaction with activated neutrophils.

Proresolving and Tissue-Protective Actions of Annexin A1–Based Cleavage-Resistant Peptides Are Mediated by Formyl Peptide Receptor 2/Lipoxin A4 Receptor

Endogenous mechanisms regulating the host response during inflammation resolution are critical in ensuring disposal of noxious stimuli and return to homeostasis. In this article, we engineered novel Annexin A1 (AnxA1)-based peptides, AnxA1(2-50), that displayed specific binding to the AnxA1 receptor (formyl peptide receptor 2/Lipoxin A4 receptor [FPR2/ALX]; IC50 ∼4 nM). Intravenous administration of AnxA1(2-50) markedly reduced (>60%) leukocyte adhesion to postcapillary venules in wild type and Fpr1(-/-), but not Fpr2/Alx(-/-), mice. Generation of a metabolically stable form of this peptide (CR-AnxA1(2-50)), engineered by substituting a cleavage site shared by human proteinase 3 and neutrophil elastase, yielded an agonist that was resistant to neutrophil-mediated cleavage and displayed enhanced proresolving actions: accelerated resolution of self-limited inflammation and enhanced macrophage efferocytosis after sterile injury, when compared with AnxA1(2-50). These actions were retained with human primary leukocytes where CR-AnxA1(2-50) decreased neutrophil-endothelial interactions (∼25-45%), and stimulated neutrophil apoptosis and macrophage efferocytosis (∼45%). In murine cardiac ischemia/reperfusion injury, CR-AnxA1(2-50) elicited tissue-protective actions reducing infarct size (∼60%) and incidence of 24-h death. These results identify AnxA1(2-50) and CR-AnxA1(2-50) as FPR2/ALX agonists that harness the proresolving actions of AnxA1, and thus may represent therapeutic tools for treatment of inflammatory conditions.

Pharmacological Inhibition of p38 Mitogen-Activated Protein Kinases Affects KC/CXCL1-Induced Intraluminal Crawling, Transendothelial Migration, and Chemotaxis of NeutrophilsIn Vivo

p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

Hyperbaric Medicine for the Hospital-Based Physician

Hyperbaric oxygen (HBO2) is the inhalation of 100% oxygen at pressures > 1.4 times atmospheric pressure. Hyperbaric oxygen can be delivered in monoplace (single person) or multi-place (multi-person) chambers. Most clinical HBO2 exposures are between 2 and 2.4 atm abs for approximately 2 hours. Hyperbaric oxygen causes the blood and tissue oxygen levels to increase, reduces the volume of intravascular and tissue bubbles (to treat decompression sickness [DCS] and arterial gas embolism [AGE]), and accelerates wash-out of other gases, such as nitrogen or carbon monoxide (CO), which is important for DCS, AGE, and CO poisoning. Hyperbaric oxygen favorably modulates ischemia-reperfusion injury by transiently inhibiting neutrophil-endothelial interactions, which is important for patients with DCS, AGE, CO poisoning, and potentially other acute ischemic conditions. Because of enhanced oxygen delivery, HBO2 is used for acute crush injury, ischemic flaps and grafts, acute central retinal arterial occlusion, other acute arterial occlusions, and idiopathic sudden sensorineural hearing loss. Hyperbaric oxygen has antimicrobial effects and is offered for patients with limb- or life-threatening infections, such as clostridial gas gangrene and necrotizing fasciitis. The most common US indication for HBO2 is the treatment of ischemic wounds (eg, diabetic lower extremity wounds, late effects of radiation, and refractory osteomyelitis). In ischemic wounds, HBO2 can deliver sufficient oxygen to the nonhealing wound to stimulate angiogenesis and healing through multiple mechanisms, including increased collagen production, increased growth factor receptor numbers, upregulation of vascular endothelial growth factor, increased circulating endothelial progenitor cells, and improvement in neutrophil-mediated host defense. Clinical trials support efficacy of HBO2 for acute CO poisoning, diabetic lower extremity wounds, crush injury, and radiation necrosis. Most hyperbaric chambers are associated with wound care centers and may be hospital based or nonhospital based. We review some of the disorders treated with HBO2 that hospital-based clinicians may be asked to evaluate.

Specific Role of Neutrophil Inducible Nitric Oxide Synthase in Murine Sepsis-Induced Lung Injury In Vivo

Nitric oxide produced by inducible nitric oxide synthase (iNOS) contributes importantly to acute lung injury (ALI), but the specific contribution of neutrophil iNOS has not been defined. Thus, we defined the role of neutrophils and specifically neutrophil iNOS in a murine model of septic ALI. Four hours after cecal ligation/perforation, ALI was characterized by increases in pulmonary neutrophil infiltration (tissue myeloperoxidase activity, bronchoalveolar lavage neutrophils), microvascular leak of Evans blue (EB) dye-labeled albumin, and oxidant stress (8-isoprostane levels). Septic ALI was neutrophil dependent, as pretreatment with anti-CD18 before cecal ligation/perforation significantly (P < 0.05) attenuated septic increases in pulmonary myeloperoxidase (39 ± 11 vs. 85 ± 14 mU/mg protein), bronchoalveolar lavage neutrophils (0.5% ± 0.2% vs. 2.1% ± 0.6%), microvascular EB-albumin leak (1.3 ± 0.3 vs. 2.6 ± 0.7 μg EB/g per minute), and 8-isoprostane content (74 ± 15 vs. 115 ± 16 pg/mg protein). The role of neutrophil iNOS was assessed by creation of neutrophil-iNOS chimeric mice: iNOS(+/+) versus iNOS(-/-) mice were bone marrow depleted by irradiation and selectively reconstituted with iNOS(+/+) versus iNOS(-/-) neutrophils. Cecal ligation/perforation resulted in significant septic ALI in + to - neutrophil-iNOS chimeric mice (iNOS(+/+) neutrophils in iNOS(-/-) mice), but not in - to + neutrophil depleted-reconstituted mice (iNOS(-/-) neutrophils in iNOS(+/+) mice). There were no significant differences between iNOS(+/+) and iNOS(-/-) neutrophils in phagocytosis, respiratory burst, or CD11a/b/CD18 surface expression, although septic shedding of CD62L was blunted in iNOS(-/-) neutrophils. Neutrophil iNOS contributes importantly to murine septic ALI in vivo, but not simply through a change in neutrophil phenotype. We speculate that neutrophil iNOS may modulate neutrophil-endothelial interactions in complex fashion, including regulation of transendothelial neutrophil migration and pulmonary neutrophil infiltration.

Two-dimensional speckle tracking echocardiography: A novel approach to evaluate left atrial mechanical function

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On, Around, and Through: Neutrophil-Endothelial Interactions in Innate Immunity

This manuscript will review our current understanding of neutrophilic polymorphonuclear leukocyte (neutrophil) interactions with the endothelium during immune and inflammatory responses, focusing on the molecular mechanisms regulating neutrophil adhesion to and migration through the endothelium in response to infection or tissue injury. This is a complex and dynamic area of research and one that has been the topic of several recent comprehensive reviews to which the interested reader is referred (64, 118, 131). By design, this review will begin with a brief review of some basic aspects of neutrophil biology and endothelial adhesion to provide a foundation. The remainder of the review will focus on selected areas of this complex field, specifically the role of the endothelial glycocalyx in regulating neutrophil adhesion and the mechanisms and consequences of migration of neutrophils between (paracellular) and through (transcellular) endothelial cells during egress from the vasculature.

Leukocyte rolling and adhesion via ICAM-1 signals to endothelial permeability. Focus on “Leukocyte rolling and adhesion both contribute to regulation of microvascular permeability to albumin via ligation of ICAM-1”

THE VASCULAR ENDOTHELIUM plays a vital role in the inflammatory response by induction and surface expression of adhesion molecules and chemokines. At sites of acute inflammation, blood flow is increased and postcapillary venules exhibit increased permeability (leakiness) and support the influx of blood leukocytes, primarily neutrophils. The relationship between neutrophil influx and increased vessel permeability has been a topic of investigation for decades. Many investigations have reported a direct neutrophil-dependent increase in vessel permeability during inflammation using in vivo and in vitro models (reviewed in Ref. 4). One aspect that has received increased attention is whether endothelial cell adhesion molecules contribute to the regulation of vessel permeability, in addition to their well-characterized role in neutrophil rolling and adhesion. Intercellular adhesion molecule-1 (ICAM-1, also known as CD54) is an immunoglobulin superfamily member that is abundantly expressed on the endothelial cell surface and is enriched at endothelial cell borders in vivo and in vitro (2, 12, 14, 17). ICAM-1 surface expression is upregulated in endothelial cells by proinflammatory cytokines like TNF-, IL-1, IFN-, or bacterial endotoxins, and ICAM-1 serves as a receptor for leukocyte 2-integrins (LFA-1 and Mac-1) (reviewed in Ref. 15). In an experiment of nature, patients with leukocyte adhesion deficiency-1 (LAD-1) have a severe primary immune deficiency in which blood neutrophils fail to localize to sites of inflammation or injury. This defect occurs because patients’ neutrophils either lack 2-integrins or contain mutations in these molecules. Studies using neutrophils from LAD-1 patients or 2-integrin-deficient mice clearly demonstrate that these cells have normal selectin-dependent rolling on activated endothelium but fail to stably arrest and transmigrate. Additional studies have demonstrated that endothelial-expressed ICAM-1 contributes to both kinetics of leukocyte rolling and arrest in vivo as determined by intravital microscopy of the cremaster muscle microcirculation in ICAM-1 / mice (16). In this issue of American Journal of Physiology-Cell Physiology, Sumagin and colleagues (18) use elegant in vivo studies to demonstrate that microvascular permeability in the cremaster muscle model is regulated by leukocyte engagement of ICAM-1. The authors monitored permeability (Ps) in cremaster microcirculation by efflux of luminal fluorescent-tagged albumin by fluorescence confocal intravital microscopy. Prior studies by Sarelius and colleagues (19) in the same model demonstrated that ICAM-1 engagement induced a localized increase in vessel permeability in unstimulated arterioles and in TNF-stimulated venules. In agreement with this finding ,4ho f TNF- stimulation of arterioles and venules in ICAM-1 knockout (KO) animals did not result in increased vessel permeability as compared with wild-type (WT) mice under identical conditions. Similar results were seen with 2-integrin KO mice. In the current study, the authors provide further evidence linking ICAM-1 expression to regulation of endothelial permeability. Comparisons between unstimulated venules and TNF--treated venules reveal that neutrophil rolling regulates venule permeability in unstimulated venules while leukocyte adhesion regulates venule permeability in TNF--stimulated venules. The 2-integrin-blocking antibodies, which inhibit neutrophil arrest on endothelium, reduced the vessel permeability, and this was further reduced by treatment with a combination of 2-integrin and P-selectin blocking antibodies that inhibits both rolling and arrest. Interestingly, the reduction in venule permeability observed by blockade of P-selectin and 2-integrin function were suggested to be due to insufficient ICAM-1 engagement due to the absence of rolling leukocytes. To examine the role that neutrophils play, circulating neutrophils were depleted by antineutrophil GR-1 antibody treatment. Notably, depletion of neutrophils caused a marked decrease in

Lymphocyte function antigen‐1 regulates neutrophil recruitment and tissue damage in acute pancreatitis

Leucocyte infiltration is a rate-limiting step in the pathophysiology of acute pancreatitis (AP) although the adhesive mechanisms supporting leucocyte-endothelium interactions in the pancreas remain elusive. The aim of this study was to define the role of lymphocyte function antigen-1 (LFA-1) in regulating neutrophil-endothelium interactions and tissue damage in severe AP. Pancreatitis was induced by retrograde infusion of sodium taurocholate into the pancreatic duct in mice. LFA-1 gene-targeted mice and an antibody directed against LFA-1 were used to define the role of LFA-1. Taurocholate challenge caused a clear-cut increase in serum amylase, neutrophil infiltration, CXCL2 (macrophage inflammatory protein-2) formation, trypsinogen activation and tissue damage in the pancreas. Inhibition of LFA-1 function markedly reduced taurocholate-induced amylase levels, accumulation of neutrophils, production of CXC chemokines and tissue damage in the pancreas. Notably, intravital microscopy revealed that inhibition of LFA-1 abolished taurocholate-induced leucocyte adhesion in postcapillary venules of the pancreas. In addition, pulmonary infiltration of neutrophils was attenuated by inhibition of LFA-1 in mice challenged with taurocholate. However, interference with LFA-1 had no effect on taurocholate-induced activation of trypsinogen in the pancreas. Our novel data suggest that LFA-1 plays a key role in regulating neutrophil recruitment, CXCL2 formation and tissue injury in the pancreas. Moreover, these results suggest that LFA-1-mediated inflammation is a downstream component of trypsinogen activation in the pathophysiology of AP. Thus, we conclude that targeting LFA-1 may be a useful approach to protect against pathological inflammation in the pancreas.