Neutrophil adhesion and activation under flow

Cytosolic S100A8/A9 promotes Ca2+ supply at LFA-1 adhesion clusters during neutrophil recruitment

S100A8/A9 is an endogenous alarmin secreted by myeloid cells during many acute and chronic inflammatory disorders. Despite increasing evidence of the proinflammatory effects of extracellular S100A8/A9, little is known about its intracellular function. Here, we show that cytosolic S100A8/A9 is indispensable for neutrophil post-arrest modifications during outside-in signaling under flow conditions in vitro and neutrophil recruitment in vivo, independent of its extracellular functions. Mechanistically, genetic deletion of S100A9 in mice caused dysregulated Ca2+ signatures in activated neutrophils resulting in reduced Ca2+ availability at the formed LFA-1/F-actin clusters with defective β2 integrin outside-in signaling during post-arrest modifications. Consequently, we observed impaired cytoskeletal rearrangement, cell polarization, and spreading, as well as cell protrusion formation in S100a9-/- compared to wildtype (WT) neutrophils, making S100a9-/- cells more susceptible to detach under flow, thereby preventing efficient neutrophil recruitment and extravasation into inflamed tissue.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Modeling Brain Vasculature Immune Interactions In Vitro

The endothelial blood-brain barrier (BBB) protects central nervous system (CNS) neurons from the changeable milieu of the bloodstream by strictly controlling the movement of molecules and immune cells between the blood and the CNS. Immune cell migration across the vascular wall is a multistep process regulated by the sequential interaction of different signaling and adhesion molecules on the endothelium and the immune cells. Accounting for its unique barrier properties and trafficking molecule expression profile, particular adaptions in immune cell migration across the BBB have been observed. Thus, in vitro models of the BBB are desirable to explore the precise cellular and molecular mechanisms involved in immune cell trafficking across the BBB. The challenge to overcome is that barrier properties of brain microvascular endothelial cells are not intrinsic and readily lost in culture. With a focus on human in vitro BBB models, we here discuss the suitability of available in vitro models for the BBB for exploring the specific mechanisms involved in immune cell trafficking across the BBB.

The Crossroads of the Coagulation System and the Immune System: Interactions and Connections

The coagulation and immune systems, two vital systems in the human body, share intimate connections that fundamentally determine patient health. These systems work together through several common regulatory pathways, including the Tissue Factor (TF) Pathway. Immune cells expressing TF and producing pro-inflammatory cytokines can influence coagulation, while coagulation factors and processes reciprocally impact immune responses by activating immune cells and controlling their functions. These shared pathways contribute to maintaining health and are also involved in various pathological conditions. Dysregulated coagulation, triggered by infection, inflammation, or tissue damage, can result in conditions such as disseminated intravascular coagulation (DIC). Concurrently, immune dysregulation may lead to coagulation disorders and thrombotic complications. This review elucidates these intricate interactions, emphasizing their roles in the pathogenesis of autoimmune diseases and cancer. Understanding the complex interplay between these systems is critical for disease management and the development of effective treatments. By exploring these common regulatory mechanisms, we can uncover innovative therapeutic strategies targeting these intricate disorders. Thus, this paper presents a comprehensive overview of the mutual interaction between the coagulation and immune systems, highlighting its significance in health maintenance and disease pathology.

Unraveling the Molecular and Cellular Pathogenesis of COVID-19-Associated Liver Injury

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) continues to cause substantial morbidity and mortality. Most infections are mild; however, some patients experience severe and potentially fatal systemic inflammation, tissue damage, cytokine storm, and acute respiratory distress syndrome. Patients with chronic liver disease have been frequently affected, experiencing high morbidity and mortality. In addition, elevated liver enzymes may be a risk factor for disease progression, even in the absence of underlying liver disease. While the respiratory tract is a primary target of SARS-CoV-2, it has become evident that COVID-19 is a multisystemic infectious disease. The hepatobiliary system might be influenced during COVID-19 infection, ranging from a mild elevation of aminotransferases to the development of autoimmune hepatitis and secondary sclerosing cholangitis. Furthermore, the virus can promote existing chronic liver diseases to liver failure and activate the autoimmune liver disease. Whether the direct cytopathic effects of the virus, host reaction, hypoxia, drugs, vaccination, or all these risk factors cause liver injury has not been clarified to a large extent in COVID-19. This review article discussed the molecular and cellular mechanisms involved in the pathogenesis of SARS-CoV-2 virus-associated liver injury and highlighted the emerging role of liver sinusoidal epithelial cells (LSECs) in virus-related liver damage.

Neutrophil diversity in inflammation and cancer

Neutrophils are the most abundant circulating leukocytes in humans and the first immune cells recruited at the site of inflammation. Classically perceived as short-lived effector cells with limited plasticity and diversity, neutrophils are now recognized as highly heterogenous immune cells, which can adapt to various environmental cues. In addition to playing a central role in the host defence, neutrophils are involved in pathological contexts such as inflammatory diseases and cancer. The prevalence of neutrophils in these conditions is usually associated with detrimental inflammatory responses and poor clinical outcomes. However, a beneficial role for neutrophils is emerging in several pathological contexts, including in cancer. Here we will review the current knowledge of neutrophil biology and heterogeneity in steady state and during inflammation, with a focus on the opposing roles of neutrophils in different pathological contexts.

Humanized MISTRG as a preclinical in vivo model to study human neutrophil-mediated immune processes

Introduction

MISTRG mice have been genetically modified to allow development of a human myeloid compartment from engrafted human CD34+ haemopoietic stem cells, making them particularly suited to study the human innate immune system in vivo. Here, we characterized the human neutrophil population in these mice to establish a model that can be used to study the biology and contribution in immune processes of these cells in vivo.

Methods and results

We could isolate human bone marrow neutrophils from humanized MISTRG mice and confirmed that all neutrophil maturation stages from promyelocytes (CD11b–CD16–) to end-stage segmented cells (CD11b+CD16+) were present. We documented that these cells possessed normal functional properties, including degranulation, reactive oxygen species production, adhesion, and antibody-dependent cellular cytotoxicity towards antibody-opsonized tumor cells ex vivo. The acquisition of functional capacities positively correlated with the maturation state of the cell. We found that human neutrophils were retained in the bone marrow of humanized MISTRG mice during steady state. However, the mature segmented CD11b+CD16+ human neutrophils were released from the bone marrow in response to two well-established neutrophil-mobilizing agents (i.e., G-CSF and/or CXCR4 antagonist Plerixafor). Moreover, the neutrophil population in the humanized MISTRG mice actively reacted to thioglycolate-induced peritonitis and could infiltrate implanted human tumors, as shown by flow cytometry and fluorescent microscopy.

Discussion

These results show that functional human neutrophils are generated and can be studied in vivo using the humanized MISTRG mice, providing a model to study the various functions of neutrophils in inflammation and in tumors.

β2-Integrin Adhesive Bond Tension under Shear Stress Modulates Cytosolic Calcium Flux and Neutrophil Inflammatory Response

On arrested neutrophils a focal adhesive cluster of ~200 high affinity (HA) β₂-integrin bonds under tension is sufficient to trigger Ca²⁺ flux that signals an increase in activation in direct proportion to increments in shear stress. We reasoned that a threshold tension acting on individual β₂-integrin bonds provides a mechanical means of transducing the magnitude of fluid drag force into signals that enhance the efficiency of neutrophil recruitment and effector function. Tension gauge tethers (TGT) are a duplex of DNA nucleotides that rupture at a precise shear force, which increases with the extent of nucleotide overlap, ranging from a tolerance of 54pN to 12pN. TGT annealed to a substrate captures neutrophils via allosteric antibodies that stabilize LFA-1 in a high- or low-affinity conformation. Neutrophils sheared on TGT substrates were recorded in real time to form HA β₂-integrin bonds and flux cytosolic Ca²⁺, which elicited shape change and downstream production of reactive oxygen species. A threshold force of 33pN triggered consolidation of HA β₂-integrin bonds and triggered membrane influx of Ca²⁺, whereas an optimum tension of 54pN efficiently transduced activation at a level equivalent to chemotactic stimulation on ICAM-1. We conclude that neutrophils sense the level of fluid drag transduced through individual β₂-integrin bonds, providing an intrinsic means to modulate inflammatory response in the microcirculation.

A2A adenosine receptor activation prevents neutrophil aging and promotes polarization from N1 towards N2 phenotype

Extracellular adenosine is a biologically active signaling molecule that accumulates at sites of metabolic stress in sepsis. Extracellular adenosine has potent immunosuppressive effects by binding to and activating G protein-coupled A_2A adenosine receptors (A_2AARs) on the surface of neutrophils. A_2AAR signaling reproduces many of the phenotypic changes in neutrophils that are characteristic of sepsis, including decreased degranulation, impaired chemotaxis, and diminished ability to ingest and kill bacteria. We hypothesized that A_2AARs also suppress neutrophil aging, which precedes cell death, and N1 to N2 polarization. Using human neutrophils isolated from healthy subjects, we demonstrate that A_2AAR stimulation slows neutrophil aging, suppresses cell death, and promotes the polarization of neutrophils from an N1 to N2 phenotype. Using genetic knockout and pharmacological blockade, we confirmed that A_2AARs decrease neutrophil aging in murine sepsis induced by cecal ligation and puncture. A_2AARs expression is increased in neutrophils from septic patients compared to healthy subject but A_2AAR expression fails to correlate with aging or N1/N2 polarization. Our data reveals that A_2AARs regulate neutrophil aging in healthy but not septic neutrophils.

Neutrophil Extracellular Traps and Neutrophil-Derived Extracellular Vesicles: Common Players in Neutrophil Effector Functions

Neutrophil granulocytes are a central component of the innate immune system. In recent years, they have gained considerable attention due to newly discovered biological effector functions and their involvement in various pathological conditions. They have been shown to trigger mechanisms that can either promote or inhibit the development of autoimmunity, thrombosis, and cancer. One mechanism for their modulatory effect is the release of extracellular vesicles (EVs), that trigger appropriate signaling pathways in immune cells and other target cells. In addition, activated neutrophils can release bactericidal DNA fibers decorated with proteins from neutrophil granules (neutrophil extracellular traps, NETs). While NETs are very effective in limiting pathogens, they can also cause severe damage if released in excess or cleared inefficiently. Since NETs and EVs share a variety of neutrophil molecules and initially act in the same microenvironment, differential biochemical and functional analysis is particularly challenging. This review focuses on the biochemical and functional parallels and the extent to which the overlapping spectrum of effector molecules has an impact on biological and pathological effects.

Effect of washed versus unwashed red blood cells on transfusion-related immune responses in preterm newborns

Objectives

Transfusion with washed packed red blood cells (PRBCs) may be associated with reduced transfusion‐related pro‐inflammatory cytokine production. This may be because of alterations in recipient immune responses.

Methods

This randomised trial evaluated the effect of transfusion with washed compared with unwashed PRBCs on pro‐inflammatory cytokines and endothelial activation in 154 preterm newborns born before 29 weeks’ gestation. Changes in plasma cytokines and measures of endothelial activation in recipient blood were analysed after each of the first three transfusions.

Results

By the third transfusion, infants receiving unwashed blood had an increase in IL‐17A (P = 0.04) and TNF (P = 0.007), whereas infants receiving washed blood had reductions in IL‐17A (P = 0.013), TNF (P = 0.048), IL‐6 (P = 0.001), IL‐8 (P = 0.037), IL‐12 (P = 0.001) and IFN‐γ (P = 0.001). The magnitude of the post‐transfusion increase in cytokines did not change between the first and third transfusions in the unwashed group but decreased in the washed group for IL‐12 (P = 0.001), IL‐17A (P = 0.01) and TNF (P = 0.03), with the difference between the groups reaching significance by the third transfusion (P < 0.001 for each cytokine).

Conclusion

The pro‐inflammatory immune response to transfusion in preterm infants can be modified when PRBCs are washed prior to transfusion. Further studies are required to determine whether the use of washed PRBCs for neonatal transfusion translates into reduced morbidity and mortality.

Detection and functional resolution of soluble immune complexes by an FcγR reporter cell panel

Fc-gamma receptor (FcγR) activation by soluble IgG immune complexes (sICs) represents a major mechanism of inflammation in certain autoimmune diseases such as systemic lupus erythematosus (SLE). A robust and scalable test system allowing for the detection and quantification of sIC bioactivity is missing. We developed a comprehensive reporter cell panel detecting activation of FcγRs. The reporter cell lines were integrated into an assay that enables the quantification of sIC reactivity via ELISA or a faster detection using flow cytometry. This identified FcγRIIA(H) and FcγRIIIA as the most sIC-sensitive FcγRs in our test system. Reaching a detection limit in the very low nanomolar range, the assay proved also to be sensitive to sIC stoichiometry and size reproducing for the first time a complete Heidelberger-Kendall curve in terms of immune receptor activation. Analyzing sera from SLE patients and mouse models of lupus and arthritis proved that sIC-dependent FcγR activation has predictive capabilities regarding severity of SLE disease. The assay provides a sensitive and scalable tool to evaluate the size, amount, and bioactivity of sICs in all settings.

Modeled vascular microenvironments: immune-endothelial cell interactions in vitro

The advancement of in vitro techniques enables a better understanding of biological processes and improves drug screening platforms. In vitro studies allow for enhanced observation of cell behavior, control over the mimicked microenvironment, and the ability to use human cells. In particular, advances in vascular microenvironment recapitulation are of interest given vasculature influence in cardiovascular vascular diseases and cancer. These investigate alterations in endothelial cell behavior and immune cell interactions with endothelial cells. Specific immune cells such as monocytes, macrophages, neutrophils, and T cells influence endothelial cell behavior by promoting or inhibiting vasculogenesis through cell-cell interaction or soluble signaling. Results from these studies showcase cell behavior in vascular diseases and in the context of tumor metastasis. In this review, we discuss examples of in vitro studies modeling immune cell-endothelial cell interactions to present methods and recent findings in the field. Schematic showcasing common methods of in vitro experimentation of endothelial-immune cell interactions, including interactions with flow, static culture, or in-direct contact.

Quantification of fast molecular adhesion by fluorescence footprinting

Rolling adhesion is a unique process in which the adhesion events are short-lived and operate under highly nonequilibrium conditions. These characteristics pose a challenge in molecular force quantification, where in situ measurement of these forces cannot be achieved with molecular force sensors that probe near equilibrium. Here, we demonstrated a quantitative adhesion footprint assay combining DNA-based nonequilibrium force probes and modeling to measure the molecular force involved in fast rolling adhesion. We were able to directly profile the ensemble molecular force distribution in our system during rolling adhesion with a dynamic range between 0 and 18 pN. Our results showed that the shear stress driving bead rolling motility directly controls the molecular tension on the probe-conjugated adhesion complex. Furthermore, the shear stress can steer the dissociation bias of components within the molecular force probe complex, favoring either DNA probe dissociation or receptor-ligand dissociation.

A Comparative Study on Changes in Total and Differential Milk Cell Counts, Activity, and Expression of Milk Phagocytes of Healthy and Mastitic Indigenous Sahiwal Cows

Milk somatic cell counts (SCCs) have been used as a gold standard to monitor mammary health as well as an indicator of raw milk quality. The present work was undertaken to compare the changes in the milk SCC, milk differential leukocyte counts (DLCs), phagocytic activity (PA) of milk neutrophils and macrophages (by nitroblue tetrazolium assay), extracellular trap formation (PicoGreen assay) and mRNA expression of various genes in milk neutrophils and macrophages (reverse transcription–polymerase chain reaction), and milk plasma cortisol concentration (enzyme-linked immunosorbent assay) in healthy, subclinical mastitis (SCM), and clinical mastitis (CM) cows. Milk was collected from healthy, SCM, and CM cows grouped based on their SCCs and California mastitis test with eight cows in each group. Milk SCC was estimated by SCC counter, and DLC was done after staining the milk slide under a microscope at 100×. Total SCCs in healthy, SCM, and CM cows were on an average of 128.30, 300.3, and 694.40 × 10³ cells/mL, respectively. Milk DLCs indicated a lower percentage of macrophage and lymphocytes and a higher (p < 0.05) percentage of neutrophils in SCM and CM compared to healthy milk. The percentage of mature segmented neutrophils was lower, whereas immature band neutrophils were higher (p < 0.05) in the SCM and CM groups as compared to healthy cows. The viability, in vitro PA, and extracellular trap formation of neutrophils were lower (p < 0.05) in SCM and CM milk samples as compared to healthy samples. However, the PA of macrophage remained unchanged in all the studied groups. The relative mRNA expression of Toll-like receptors (TLR2, TLR4), myeloperoxidase, and interleukin 2α (IL-2α) receptor (CD25) were minimum in healthy samples and increased (p < 0.05) with the progress of mammary inflammation. However, CD44 decreased (p < 0.05), and CD62L remained unchanged in mastitis as compared to healthy cows. Plasma cortisol concentrations were higher (p < 0.05) in mastitis as compared to healthy cows and were negatively correlated with the number of milk macrophages and the functions of milk phagocytes. Estimation of total SCC, milk DLC, and activity of milk phagocytes is essential for effective control and prevention of incidence of mastitis in dairy cows.

Perinatal Inflammation: Could Partial Blocking of Cell Adhesion Molecule Function Be a Solution?

In spite of the great advances made in recent years in prenatal and perinatal medicine, inflammation can still frequently result in injury to vital organs and often constitutes a major cause of morbidity. It is today well established that in neonates—though vulnerability to infection among neonates is triggered by functional impairments in leukocyte adhesion—the decreased expression of cell adhesion molecules also decreases the inflammatory response. It is also clear that the cell adhesion molecules, namely, the integrins, selectins, and the immunoglobulin (Ig) gene super family, all play a crucial role in the inflammatory cascade. Thus, by consolidating our knowledge concerning the actions of these vital cell adhesion molecules during the prenatal period as well as regarding the genetic deficiencies of these molecules, notably leukocyte adhesion deficiency (LAD) I, II, and III, which can provoke severe clinical symptoms throughout the first year of life, it is anticipated that intervention involving blocking the function of cell adhesion molecules in neonatal leukocytes has the potential to constitute an effective therapeutic approach for inflammation. A promising perspective is the potential use of antibody therapy in preterm and term infants with perinatal inflammation and infection focusing on cases in which LAD is involved, while a further important scientific advance related to this issue could be the combination of small peptides aimed at the inhibition of cellular adhesion.

The Neutrophil Secretome as a Crucial Link between Inflammation and Thrombosis

Cardiovascular diseases are a leading cause of death. Blood-cell interactions and endothelial dysfunction are fundamental in thrombus formation, and so further knowledge of the pathways involved in such cellular crosstalk could lead to new therapeutical approaches. Neutrophils are secretory cells that release well-known soluble inflammatory signaling mediators and other complex cellular structures whose role is not fully understood. Studies have reported that neutrophil extracellular vesicles (EVs) and neutrophil extracellular traps (NETs) contribute to thrombosis. The objective of this review is to study the role of EVs and NETs as key factors in the transition from inflammation to thrombosis. The neutrophil secretome can promote thrombosis due to the presence of different factors in the EVs bilayer that can trigger blood clotting, and to the release of soluble mediators that induce platelet activation or aggregation. On the other hand, one of the main pathways by which NETs induce thrombosis is through the creation of a scaffold to which platelets and other blood cells adhere. In this context, platelet activation has been associated with the induction of NETs release. Hence, the structure and composition of EVs and NETs, as well as the feedback mechanism between the two processes that causes pathological thrombus formation, require exhaustive analysis to clarify their role in thrombosis.

Effect of Cannabinoid 2 Receptor Modulation on the Peripheral Immune Response in Central Nervous System Injury-Induced Immunodeficiency Syndrome

Introduction: Acute central nervous system (CNS) injury, such as stroke, spinal cord injury, or traumatic brain injury can result in dysregulated immune response, and the condition is known as CNS injury-induced immunodeficiency syndrome (CIDS). The endocannabinoid system is an important homeostatic regulator in the CNS and immune system. Activation of cannabinoid 2 receptors (CB2R) on immune cells has been reported to dampen inflammation, suggesting a potential role of CB2R in the peripheral immune response following CNS injury. In this study, we have investigated the effect of CB2R modulation on the peripheral immune response during CIDS. Materials and Methods: Experimental CNS injury was induced in C57BL/6 mice through intracerebral injection of the vasopressor peptide, endothelin-1. A selective CB2R agonist (HU308) was used as an early treatment before the onset of CIDS and AM630, a selective CB2R antagonist, was administered as a later-phase therapy to combat the systemic immunodeficiency following the CNS injury. The peripheral immune response to endotoxin was studied 24 h after the CNS injury using intravital microscopy to examine leukocyte activation within the intestinal microcirculation in mice. Brain infarct size, and plasma levels of cytokines and soluble adhesion molecules were measured as additional parameters for the assessment of treatment outcomes. Results: Our results showed that early CB2R activation with HU308 reduced brain injury size and restored leukocyte response to endotoxin in the peripheral microcirculation. Late CB2R inhibition with AM630 also improved the peripheral leukocyte response to endotoxin and did not exacerbate the extent of brain injury. Discussion: CB2R activation has the potential to mitigate CNS injury as an early treatment by limiting neuroinflammation and preventing the development of CIDS. At the later stage with already-established CIDS, treatment may require dampening CB2R activation to improve the patient's outcome.

Suppressive Role of Bam32/DAPP1 in Chemokine-Induced Neutrophil Recruitment

Bam32 (B cell adaptor molecule of 32 kDa) functions in the immune responses of various leukocytes. However, the role of neutrophil Bam32 in inflammation is entirely unknown. Here, we determined the role of Bam32 in chemokine CXCL2-induced neutrophil chemotaxis in three mouse models of neutrophil recruitment. By using intravital microscopy in the mouse cremaster muscle, we found that transmigrated neutrophil number, neutrophil chemotaxis velocity, and total neutrophil chemotaxis distance were increased in Bam32^−/− mice when compared with wild-type (WT) mice. In CXCL2-induced mouse peritonitis, the total emigrated neutrophils were increased in Bam32^−/− mice at 2 but not 4 h. The CXCL2-induced chemotaxis distance and migration velocity of isolated Bam32^−/− neutrophils in vitro were increased. We examined the activation of small GTPases Rac1, Rac2, and Rap1; the levels of phospho-Akt2 and total Akt2; and their crosstalk with Bam32 in neutrophils. The deficiency of Bam32 suppressed Rap1 activation without changing the activation of Rac1 and Rac2. The pharmacological inhibition of Rap1 by geranylgeranyltransferase I inhibitor (GGTI298) increased WT neutrophil chemotaxis. In addition, the deficiency of Bam32, as well as the inhibition of Rap1 activation, increased the levels of CXCL2-induced Akt1/2 phosphorylation at Thr308/309 in neutrophils. The inhibition of Akt by SH-5 attenuated CXCL2-induced adhesion and emigration in Bam32^−/− mice. Together, our results reveal that Bam32 has a suppressive role in chemokine-induced neutrophil chemotaxis by regulating Rap1 activation and that this role of Bam32 in chemokine-induced neutrophil recruitment relies on the activation of PI3K effector Akt.

Vascular endothelial ERp72 is involved in the inflammatory response in a rat model of skeletal muscle injury

The vascular inflammatory response involves the coordinated action of a large network of molecular mediators and culminates in the transmigration of leukocytes into the site of inflammation. Inflammatory mediators include a variety of protein families, including adhesion molecules such as integrins and members of the immunoglobulin superfamily, as well as other cytokines and chemokines. In this study, a rat model of traumatic skeletal muscle injury was used to demonstrate endoplasmic reticulum resident protein 72 (ERp72) overexpression in the early phase of the inflammatory response that follows skeletal muscle injury. Reverse transcription‑quantitative PCR, western blotting, dual‑labeling immunohistochemistry and immunofluorescence experiments confirmed that ERp72 was expressed on the endothelial cells of blood vessels present at the injured area. In addition, a cell‑based neutrophil adhesion assay indicated that a polyclonal antibody specific for ERp72 significantly reduced adhesion of neutrophils to activated human umbilical vein endothelial cells (35% reduction). These data suggested that ERp72 expression on vascular endothelial cells may play a role in skeletal muscle inflammation and could be considered as a target for the modulation of leukocyte‑endothelial cell interactions in an inflammatory setting.

Frontline Science: A flexible kink in the transmembrane domain impairs β2 integrin extension and cell arrest from rolling

β2 integrins are the main adhesion molecules in neutrophils and other leukocytes and are rapidly activated by inside-out signaling, which results in conformational changes that are transmitted through the transmembrane domain (TMD). Here, we investigated the biologic effect of introducing a proline mutation in the β2 integrin TMD to create a flexible kink that uncouples the topology of the inner half of the TMD from the outer half and impairs integrin activation. The β2 integrin alpha chains, αL, αM, αX, and αD, all contain an inserted (I) domain with homology to von Willebrand factor A domain. β2 activation was monitored in a homogenous binding assay of 2 reporter monoclonal antibodies: KIM127 reporting extension (E+ ) and mAb24 reporting the high-affinity (H+ ) conformation of the β2 I-like domain. The proline mutation partially diminished chemokine-induced extension, but not the high-affinity conformation. The proline mutation in the TMD of β2 completely inhibited arrest of rolling HL-60 cells in response to the chemokine IL-8. TMD mutant HL-60 cells rolling on P-selectin and ICAM-1 were unable to reduce their rolling velocity in response to IL-8. Quantitative dynamic footprinting live-cell imaging showed that blocking TMD topology transmission impaired the chemokine-induced activation of β2, limiting the appearance of extended high-affinity (E+ H+ ) β2. This also resulted in a defect in early spreading (3 min after arrest), which could be overcome by forced integrin activation using Mn2+ . We conclude that the TMD proline mutation severely impairs β2 integrin extension, cell arrest, and early spreading.

Effect of packed red blood cell transfusion on IL-8 and sICAM-1 in premature neonates at different postnatal ages

BACKGROUND

Transfusion-related immunomodulation (TRIM) has been described in adults; however, its existence in neonates is not confirmed. The generation of TRIM is attributed to increased concentrations of IL-8, sICAM-1 and other pro-inflammatory cytokines. This study aimed to monitor changes in IL-8, sICAM-1 as markers for TRIM in premature infants at different postnatal ages.

METHODS

Preterm infants with a gestational age between 28 and 32 weeks who were receiving PRBC transfusion during the first 28 days of life were included in the study. Infants were stratified into two groups according to their postnatal age: Group 1 with postnatal ages of (0-14) days and Group 2 of (15-28) days. The concentrations of IL-8 and sICAM-1 were measured by enzyme-linked immunosorbent assay (ELISA) before transfusion, 6 h after the end of transfusion and in the donor's PRBCs bag immediately before infusion into the baby.

RESULTS

IL-8 concentration in the PRBCs bags correlated with post-transfusion level in Group 2 (r = 0.59, p = 0.002) but not in Group 1 (r = 0.39, p = 0.06). sICAM-1 concentration in the bag correlated with infants'concentrations in neither group. In Group 1, pre-transfusion concentrations of both cytokines (IL-8 and sICAM-1) did not correlate whereas post-transfusion concentrations did correlate (r = -0.09, p = 0.68 and r = 0.4, p = 0.05 respectively). In Group 2, the concentrations of both cytokines did not correlate with each other during pre-transfusion (r = 0.11, p = 0.58) as well as post-transfusion (r = 0.12, p = 0.56). There was no significant increase in either cytokines after transfusion in each group.

CONCLUSION

This study showed positive correlation between IL-8 concentration in the transfusion bag and post transfusion in Group 2 infants which could be attributed to passive transmission from the bags. This study does not support an immune modulatory effect for packed RBC in preterm infants.

Shedding New Light on The Role of ανβ3 and α5β1 Integrins in Rheumatoid Arthritis

ανβ3 and α5β1 are essential glycoproteins involved in the pathogenesis of rheumatoid arthritis (RA). Understanding of the role these integrins play in disease have been analyzed via description of cells-expressing ανβ3 and α5β1 and their mediators to trigger inflammation. ανβ3 and α5β1 facilitate cells-ECM and cell-cell communication, producing pro-inflammatory factors. Pro-inflammatory factors are essential for the building of undesirable new blood vessels termed angiogenesis which can further lead to destruction of bones and joints. Despite many attempts to target these glycoproteins, there are still some problems, therefore, there is still interest in understanding the synergistic role these integrins play in the pathogenesis of RA. The purpose of this review is to gain insights into the biological effects of ανβ3 and α5β1 in synovial tissues that are relevant to pathogenesis and therapy of RA.

Role and mechanisms of cytokines in the secondary brain injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common and severe cerebrovascular disease that has high mortality. Few survivors achieve self-care. Currently, patients receive only symptomatic treatment for ICH and benefit poorly from this regimen. Inflammatory cytokines are important participants in secondary injury after ICH. Increases in proinflammatory cytokines may aggravate the tissue injury, whereas increases in anti-inflammatory cytokines might be protective in the ICH brain. Inflammatory cytokines have been studied as therapeutic targets in a variety of acute and chronic brain diseases; however, studies on ICH are limited. This review summarizes the roles and functions of various pro- and anti-inflammatory cytokines in secondary brain injury after ICH and discusses pathogenic mechanisms and emerging therapeutic strategies and directions for treatment of ICH.

Dioclea violacea lectin ameliorates inflammation in the temporomandibular joint of rats by suppressing intercellular adhesion molecule-1 expression

Inflammation of temporomandibular joint (TMJ) tissues are the most common cause of pain conditions associated with temporomandibular disorders (TMDs). After a tissue and/or neural damage, the inflammatory response is characterized by plasma extravasation and leukocytes infiltration in the TMJ tissues, which in turn, release inflammatory cytokines cascades responsible for inflammatory pain. Lectins are glycoproteins widely distributed in nature that may exhibit anti-inflammatory properties. This study demonstrated by molecular docking and MM/PBSA that the lectin from Dioclea violacea (DVL) interacts favorably with α-methyl-D-mannoside, N-acetyl-D-glucosamine, and core1-sialyl-Lewis X which are associated with leukocytes migration during an inflammatory response. Wistar rats pretreated with intravenously injection of DVL demonstrated a significant inhibition of plasma extravasation induced by carrageenan (a non-neurogenic inflammatory inductor) and mustard oil (a neurogenic inflammatory inductor) in the TMJ periarticular tissues (p < 0.05; ANOVA, Tukey's test). In addition, DVL significantly reduced carrageenan-induced leukocyte migration in the TMJ periarticular tissues mediated by down-regulation of ICAM-1 expression. These results suggest a potential anti-inflammatory effect of DVL in inflammatory conditions of TMJ.

Regulation of neutrophils in type 2 immune responses

Type 2 immune responses contribute to the resistance to helminths and toxins as well as several physiological processes. Although they usually do not participate in type 2 immune responses, neutrophils have been shown in mice to enhance the anti-helminth response, but they also contribute to increased target tissue damage. Increased pathology and morbidity is also observed in type 2 immune-mediated disorders, such as allergic asthma, when neutrophils become a predominant subset of the infiltrate. How neutrophil recruitment is regulated during type 2 immune responses is now starting to become clear, with recent data showing that signaling via the prototypic type 2 cytokine interleukin-4 receptor mediates direct and indirect inhibitory actions on neutrophils in mice and humans.

Intravital imaging by simultaneous label-free autofluorescence-multiharmonic microscopy

Intravital microscopy (IVM) emerged and matured as a powerful tool for elucidating pathways in biological processes. Although label-free multiphoton IVM is attractive for its non-perturbative nature, its wide application has been hindered, mostly due to the limited contrast of each imaging modality and the challenge to integrate them. Here we introduce simultaneous label-free autofluorescence-multiharmonic (SLAM) microscopy, a single-excitation source nonlinear imaging platform that uses a custom-designed excitation window at 1110 nm and shaped ultrafast pulses at 10 MHz to enable fast (2-orders-of-magnitude improvement), simultaneous, and efficient acquisition of autofluorescence (FAD and NADH) and second/third harmonic generation from a wide array of cellular and extracellular components (e.g., tumor cells, immune cells, vesicles, and vessels) in living tissue using only 14 mW for extended time-lapse investigations. Our work demonstrates the versatility and efficiency of SLAM microscopy for tracking cellular events in vivo, and is a major enabling advance in label-free IVM.

Label-free and real-time visualization of the tumor microenvironment is attractive but challenging. Here the authors present an approach for simultaneous autofluorescence functional imaging and second/third harmonic generation imaging of structural features, using a single excitation source.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

IRF3 Inhibits Neutrophil Recruitment in Mice Infected with Pseudomonas aeruginosa

Pseudomonas aeruginosa is the major cause of morbidity and mortality in patients with ventilator-associated pneumonia. Interferon regulatory factor 3 (IRF3) is a transcription factor that plays an important role in the immune response to viral infection via the IRF3/IFN-β signaling pathway. Controversial data exist regarding the role of IRF3 in immune cell recruitment during bacterial infections. IRF3 has been shown to promote neutrophil recruitment and bacterial clearance in mice infected with P. aeruginosa by inducing the production of specific chemokines and cytokines. In contrast, our study showed that IRF3 knockout (KO) mice infected with P. aeruginosa exhibited greater survival rates, demonstrated enhanced bacterial clearance, and showed significantly increased neutrophil recruitment to the lungs, when compared with the wild-type (WT) mice. The peritoneal lavage fluid collected from IRF3 KO mice 4 h after intraperitoneal injection with P. aeruginosa or 3% thioglycolate contained a significantly increased number of neutrophils. Furthermore, neutrophils from the bone marrow (BM) of IRF3 KO mice showed greater adhesiveness to the extracellular matrix when compared with those of WT mice, post-P. aeruginosa infection. In addition, IRF3 induced the expression of target genes in WT neutrophils infected with P. aeruginosa. These findings indicate that IRF3 exacerbates P. aeruginosa-induced mortality in mice by inhibiting neutrophil adhesion and recruitment to the lungs. Together, these data indicate that the inhibition of IRF3 might provide a possible mechanism for controlling P. aeruginosa infections.

P- and E-selectin receptor antagonism prevents human leukocyte adhesion to activated porcine endothelial monolayers and attenuates porcine endothelial damage

BACKGROUND

Alongside the need to develop more effective and less toxic immunosuppression, the shortage of human organs available for organ transplantation is one of the major hurdles facing the field. Research into xenotransplantation, as an alternative source of organs, has unveiled formidable challenges. Porcine lungs perfused with human blood rapidly sequester the majority of circulating neutrophils and platelets, which leads to inflammation and organ failure within hours, and is not significantly attenuated by genetic modifications to the pig targeted to diminish antibody binding and complement and coagulation cascade activation.

METHODS

Here, we model the interaction of freshly isolated human leukocytes with xenotransplanted vasculature under physiologic flow conditions using microfluidic channels coated with porcine endothelial cells. Both isolated human neutrophils and whole human blood were perfused over transgenic pig aortic endothelial cells that had been activated with rhTNF-α or rhIL-4 using the BioFlux system. Novel compounds GMI-1271 and rPSGL1.Fc were tested as E- and P- selectin antagonists, respectively. Cellular adhesion and rolling events were tracked using FIJI (imageJ).

RESULTS

Porcine endothelium activated with either rhTNF-α or rhIL-4 expressed high amounts of selectins, to which isolated human neutrophils readily rolled and tethered. Both E-and P-selectin antagonism significantly reduced the number of neutrophils rolling and rolling distance in a dose-dependent manner, with near total inhibition at higher doses (P < .001). Similarly, with whole human blood, selectin blocking compounds exhibited dose-dependent inhibition of prevalent leukocyte adhesion and severe endothelial injury (Untreated: 394 ± 97 PMNs/hpf, 57 ± 6% loss EC; GMI1271+rPSGL1.Fc: 23 ± 9 PMNs/hpf, 8 ± 6% loss EC P < .01).

CONCLUSIONS

Selectin blockade may be useful as part of an integrated strategy to prevent neutrophil-mediated organ xenograft injury, especially during the early time points following reperfusion.

MICROVASCULAR FLOW ABNORMALITIES ASSOCIATED WITH RETINAL VASCULITIS: A Potential of Mechanism of Retinal Injury

PURPOSE

To investigate the structural optical coherence tomography and related microvascular flow characteristics in eyes with retinal vasculitis.

METHODS

Regions involved with perivascular infiltration in eyes with retinal vasculitis, but no evidence of large vessel occlusion were evaluated with optical coherence tomography (OCT), OCT angiography, and fluorescein angiography.

RESULTS

Ten eyes of 5 patients with a variety of etiologies of retinal vasculitis were evaluated. These patients did not have either cotton wool spots or deeper placoid areas of retinal ischemia. Around large vessels there was perivascular infiltration with leakage and staining seen during fluorescein angiography. Structural OCT showed slight thickening with loss of visualization of normal retinal laminations. OCT angiography showed a lack of flow signal in capillary sized vessels in the same areas. Treatment resulted in a rapid thinning of the affected areas, with the inner and middle layers of the retina becoming thinner than surrounding uninvolved areas. OCT angiography did not show a return of capillary perfusion in these regions. The thickness change in the structural OCT as shown by a heat map had a pattern mimicking the original perivascular infiltration around large retinal vessels.

CONCLUSION

Capillary level perfusion abnormalities can develop in regions adjacent to large vessel inflammatory infiltrate that result in retinal thinning without the development of usual stigmata of acute microvascular flow obstruction such as cotton wool spots. This suggests that retinal damage may occur in retinal vasculitis that would not be recognized without using OCT-based imaging modalities.

Role of the Glycocalyx as a Barrier to Leukocyte-Endothelium Adhesion

Leukocyte (WBC) to endothelial cell (EC) adhesion is a receptor-mediated process governed by the avidity and affinity of selectins, which modulate adhesive forces during WBC rolling, and integrins, which determine the strength of firm adhesion. Adhesion receptors on the EC surface lie below an endothelial surface layer (ESL) comprised of the EC glycocalyx and adsorbed proteins which, in vivo, have a thickness on the order 500 nm. The glycocalyx consists of a matrix of the glycosaminoglycans heparan sulfate and chondroitin sulfate, bound to proteoglycans and encased in hyaluronan. Together, these carbohydrates form a layer that varies in glycan content along the length of post-capillary venules where WBC-EC adhesion occurs. Thickness and porosity of the glycocalyx can vary dramatically during the inflammatory response as observed by increased infiltration and diffusion of macromolecules within the layer following activation of the EC by cytokines and chemoattractants. In models of inflammation in the living animal, the shedding of glycans and diminished thickness of the glycocalyx rapidly occur to facilitate penetration by the WBCs and adhesion to the EC. The primary effectors of glycan shedding appear to be metalloproteases and heparanase released by the EC. Retardation of glycan shedding and WBC-EC adhesion has been demonstrated in vivo using MMP inhibitors and low-molecular-weight heparin (LMWH), where the latter competitively binds to heparanase liberated by the EC. Together, these agents may serve to stabilize the ESL and provide a useful strategy for treatment of inflammatory disorders.

Ligand-specific binding forces of LFA-1 and Mac-1 in neutrophil adhesion and crawling

The force spectra for various LFA-1/Mac-1–ligand bonds were compared and their functions tested in mediating PMN recruitment under flow. Multiple endothelial ligands present distinct bond rupture forces and lifetimes, which correlate well with their biological phenotypes. In addition to ICAM, JAM or RAGE is also crucial in cell adhesion and crawling.

Lymphocyte function–associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) and their counterreceptors such as intercellular cell adhesion molecules (ICAM-1 and ICAM-2), junctional adhesion molecules (JAM-A, JAM-C), and receptors for advanced glycation end products (RAGE) are crucial for promoting polymorphonuclear leukocyte (neutrophil, PMN) recruitment. The underlying mechanisms of ligand-specific bindings in this cascade remain incompletely known. We compared the dynamic force spectra for various LFA-1/Mac-1–ligand bonds using single-molecule atomic force microscopy (AFM) and tested their functions in mediating PMN recruitment under in vitro shear flow. Distinct features of bond rupture forces and lifetimes were uncovered for these ligands, implying their diverse roles in regulating PMN adhesion on endothelium. LFA-1 dominates PMN adhesion on ICAM-1 and ICAM-2, while Mac-1 mediates PMN adhesion on RAGE, JAM-A, and JAM-C, which is consistent with their bond strength. All ligands can trigger PMN spreading and polarization, in which Mac-1 seems to induce outside-in signaling more effectively. LFA-1–ICAM-1 and LFA-1/Mac-1–JAM-C bonds can accelerate PMN crawling under high shear stress, presumably due to their high mechanical strength. This work provides new insight into basic molecular mechanisms of physiological ligands of β2 integrins in PMN recruitment.

Role of the Cytoskeleton in Myeloid Cell Function

During an innate immune response, myeloid cells undergo complex morphological adaptations in response to inflammatory cues, which allow them to exit the vasculature, enter the tissues, and destroy invading pathogens. The actin and microtubule cytoskeletons are central to many of the most essential cellular functions including cell division, cell morphology, migration, intracellular trafficking, and signaling. Cytoskeletal structure and regulation are crucial for many myeloid cell functions, which require rapid and dynamic responses to extracellular signals. In this chapter, we review the roles of the actin and microtubule cytoskeletons in myeloid cells, focusing primarily on their roles in chemotaxis and phagocytosis. The role of myeloid cell cytoskeletal defects in hematological disorders is highlighted throughout.

Mechanisms of endothelial activation in sepsis and cell culture models to study the heterogeneous host response

Sepsis is currently viewed as a fundamental disintegration of control functions from intracellular signalling to immunoregulatory and neuroendocrine mechanisms. The immediate threat in sepsis is invasive infection, and the need to activate immune defense mechanisms to clear the pathogen before irreparable damage occurs. In the process of pathogen elimination, however, the systemic host response to infection may cause collateral damage to the endothelium and may lead to the destruction of host tissues.A number of experimental models have been developed to monitor endothelial activation and to study endothelial dysfunction under septic conditions. Here, we review the application of these models to assess the highly variable host response in sepsis and to investigate the efficacy of adsorbent-based extracorporeal therapies. We also highlight the need for efficient diagnostic tools, which are indispensable to select patients who are likely to benefit from distinct adjunctive therapies.

Force-dependent calcium signaling and its pathway of human neutrophils on P-selectin in flow

P-selectin engagement of P-selectin glycoprotein ligand-1 (PSGL-1) causes circulating leukocytes to roll on and adhere to the vascular surface, and mediates intracellular calcium flux, a key but unclear event for subsequent arresting firmly at and migrating into the infection or injured tissue. Using a parallel plate flow chamber technique and intracellular calcium ion detector (Fluo-4 AM), the intracellular calcium flux of firmly adhered neutrophils on immobilized P-selectin in the absence of chemokines at various wall shear stresses was investigated here in real time by fluorescence microscopy. The results demonstrated that P-selectin engagement of PSGL-1 induced the intracellular calcium flux of firmly adhered neutrophils in flow, increasing P-selectin concentration enhanced cellular calcium signaling, and, force triggered, enhanced and quickened the cytoplasmic calcium bursting of neutrophils on immobilized P-selectin. This P-selectin-induced calcium signaling should come from intracellular calcium release rather than extracellular calcium influx, and be along the mechano-chemical signal pathway involving the cytoskeleton, moesin and Spleen tyrosine kinase (Syk). These results provide a novel insight into the mechano-chemical regulation mechanism for P-selectin-induced calcium signaling of neutrophils in flow.

Mechanical regulation of calcium signaling of HL-60 on P-selectin under flow

Background

Binding of P-selectin to P-selectin glycoprotein ligand-1 (PSGL-1) makes neutrophils roll on and adhere to inflammatory site. Intracellular calcium bursting of adhered neutrophils is a key event for subsequent arresting firmly at and migrating into the injured tissue. But, it remains unclear how the cytoplasmic calcium signaling of the cells were modulated by the fluid shear stress. Here, we focus on mechanical regulation of P-selectin-induced calcium signaling of neutrophil-like HL-60 cells under flow.

Methods

HL-60 cells were loaded with Fluo-4 AM for fluorescent detection of intracellular calcium ion, and then perfused over P-selectin-coated bottom of parallel-plate flow chamber. The intracellular calcium concentration of firmly adhered cell under flow was observed in real time by fluorescence microscopy.

Results

Force triggered, enhanced and quickened cytoplasmic calcium bursting of HL-60 on P-selectin. This force-dependent calcium signaling was induced by the immobilized P-selectin coated on substrates in absence of chemokine. Increasing of both shear stress and P-selectin concentration made the calcium signaling intensive, through quickening the cytosolic calcium release and upregulating both probability and peak level of calcium signaling.

Conclusions

Immobilized P-selectin-induced calcium signaling of HL-60 cells is P-selectin concentration- and mechanical force-dependent. The higher both the P-selectin concentration and the external force on cell, the more intensive the calcium signaling. It might provide a novel insight into the mechano-chemical regulation mechanism for intracellular signaling pathways induced by adhesion molecules.

Intercellular Interactions as Regulators of NETosis

Neutrophil extracellular traps (NETs) are chromatin-derived webs extruded from neutrophils in response to either infection or sterile stimulation with chemicals, cytokines, or microbial products. The vast majority of studies have characterized NET release (also called NETosis) in pure neutrophil cultures in vitro. The situation is surely more complex in vivo as neutrophils constantly sample not only pathogens and soluble mediators but also signals from cellular partners, including platelets and endothelial cells. This complexity is beginning to be explored by studies utilizing in vitro co-culture, as well as animal models of sepsis, infective endocarditis, lung injury, and thrombosis. Indeed, various selectins, integrins, and surface glycoproteins have been implicated in platelet–neutrophil interactions that promote NETosis, albeit with disparate results across studies. NETosis can also clearly be regulated by soluble mediators derived from platelets, such as eicosanoids, chemokines, and alarmins. Beyond platelets, the role of the endothelium in modulating NETosis is being increasingly revealed, with adhesive interactions likely priming neutrophils toward NETosis. The fact that the same selectins and surface glycoproteins may be expressed by both platelets and endothelial cells complicates the interpretation of in vivo data. In summary, we suggest in this review that the engagement of neutrophils with activated cellular partners provides an important in vivo signal or “hit” toward NETosis. Studies should, therefore, increasingly consider the triumvirate of neutrophils, platelets, and the endothelium when exploring NETosis, especially in disease states.

Serum levels of soluble adhesion molecules in newly diagnosed acute myeloid leukemia and in complete remission suggest endothelial cell activation by myeloblasts

BACKGROUND AND AIMS

Despite high-dose multi-agent chemotherapy and allogeneic stem cell transplantation, the relapse rate of acute myeloid leukemia (AML) is high. Further, the disease is highly resistent to drugs. We speculated that deeper understanding of AML-endothelial cell interactions might provide new targets for selective modulation of the AML microenvironment and form the basis for novel treatment approaches. In this study, we evaluated levels of endothelium derived soluble adhesion molecules in active disease and in complete remission (CR) and their relationship with inflammatory cytokines.

METHODS

Baseline serum levels of 25 cytokines and 5 soluble adhesion molecules were measured in 84 AML patients using biochip array technology. CR samples were evaluated in 44 patients of this cohort. The control group consisted of 15 healthy blood donors.

RESULTS

All analytes were independent of age or disease origin. Some correlations were restricted to active AML, some were ubiquitous and some were found in remission. In active disease, E-selectin (E-SEL) and VCAM-1 correlated with leukocyte count, E-SEL correlated with P-selectin (P-SEL). Platelet count related to IL-7, EGF and VEGF but not to P-SEL. In CR, P-SEL correlated with platelet count and EGF but not with E-SEL. There was no relationship of P-SEL and E-SEL in the control group.

CONCLUSIONS

Leukemic activity is associated with a different pattern of soluble adhesion molecule levels. Both E-SEL and P-SEL may be derived from endothelial cells. Their levels correlated in active disease. E-SEL correlated with leukocyte count. In CR, P-SEL physiologically correlated with platelet count. The correlation with E-SEL was insignificant and absent in the control group. Our data suggest activation of endothelial cells in the presence of myeloblasts.

Neutrophils assist the metastasis of circulating tumor cells in pancreatic ductal adenocarcinoma: A new hypothesis and a new predictor for distant metastasis

During our research on circulating tumor cells (CTCs) derived from tumor-adjacent vessels in pancreatic ductal adenocarcinoma (PDAC), we found that CTCs are sometimes surrounded by white blood cells (WBCs) in blood. We hypothesize that such interaction between WBCs and CTCs in blood is a mechanism by which WBCs assist in the metastasis of CTCs. We present our laboratory finding, with our evaluation of the association between the neutrophil-to-lymphocyte ratio (NLR, the most investigated clinical parameter of WBCs) and distant metastasis after curative surgery in PDAC. The laboratory finding was presented through immunofluorescence. In the clinical segment, we performed a retrospective study on PDAC patients with distant metastasis after curative surgery who were referred to Peking University Third Hospital between 2005 and 2014. The data on the possible clinical factors were collected by a retrospective review of the patients' records. Immunofluorescence results showed that CTCs are surrounded by WBCs in tumor-adjacent vessels of PDAC patients. In the clinical segment, 112 (70%) of a total of 160 PDAC patients were found to have developed distant metastases after surgery; among the 112 patients, only 89 had entire data and were enrolled for further analysis (84.3% patients had liver metastasis). No significant association was found between the NLR and overall survival (hazard ratio [HR] = 1.027, 95% confidence interval [CI] 0.723-1.459, P = 0.88); however, a significant relationship between the NLR and distant metastasis after curative surgery was found on the univariate (HR = 1.641, 95% CI 1.058-2.545, P = 0.027) and multivariate analyses (HR = 2.15, 95% CI 1.279-3.615, P = 0.004). Neutrophils might assist in distant metastasis through interaction with CTCs in blood. Moreover, NLR is an effective predictor for distant metastasis after curative surgery for PDAC.

Rac GTPase Activating Protein ARHGAP25 Regulates Leukocyte Transendothelial Migration in Mice

ARHGAP25 is a Rac-specific GTPase-activating protein that is expressed primarily in hematopoietic cells. The involvement of ARHGAP25 in regulating the recruitment of leukocytes to inflammatory sites was investigated in genetically modified mice. Using intravital microscopy, we show that Arhgap25 deficiency affects all steps of leukocyte recruitment with a predominant enhancement of transendothelial migration of neutrophilic granulocytes. Increased transmigration of Arhgap25-deficient leukocytes is demonstrated in inflamed cremaster muscle venules, in a peritonitis model, and in an in vitro chemotaxis assay. Using bone marrow chimeric mice lacking ARHGAP25 in the hematopoietic compartment, we show that enhanced migration in the absence of ARHGAP25 is due to defective leukocyte function. In search for potential mechanisms of ARHGAP25-regulated migration of neutrophils, we detected an increase in the amount of active, GTP-bound Rac and Rac-dependent cytoskeletal changes in the absence of ARHGAP25, suggesting a critical role of ARHGAP25 in counterbalancing the Rac-activating effect of nucleotide exchange factors. Taken together, using Arhgap25-deficient mice, we identified ARHGAP25 as a relevant negative regulator of leukocyte transendothelial migration.

Safety, pharmacokinetics and pharmacodynamics of GLPG0974, a potent and selective FFA2 antagonist, in healthy male subjects

Aims

Free fatty acids (FFA) can act as direct signalling molecules through activation of several membrane‐bound G‐protein coupled receptors. The FFA2 receptor (known as GPR43) is activated by short chain fatty acids (SCFA) such as acetate and has been shown to play a major role in SCFA‐induced neutrophil activation and migration and to contribute in the development and control of inflammation. GLPG0974 is a potent and selective antagonist of the human FFA2. The main objectives of the two phase 1 trials were to characterize the safety, tolerability, pharmacokinetics and pharmacodynamics of GLPG0974.

Methods

Two consecutive randomized, double‐blind, placebo‐controlled, single centre trials in healthy subjects were performed. In the first, GLPG0974 was administered as single doses up to 250 mg and in the second, multiple daily doses up to 400 mg for 14 days were evaluated. Non‐compartmental analysis was used to determine GLPG0974 pharmacokinetics while target engagement was investigated through the inhibition of neutrophils in acetate‐simulated whole blood samples using surface expression of CD11b activated epitope as a marker of neutrophil activation.

Results

The investigation of safety/tolerability and pharmacokinetics in the early development phase showed that GLPG0974 was safe and well tolerated up to a daily dose of 400 mg. GLPG0974 showed good and dose proportional exposure up to 400 mg daily as well as a substantial and sustained inhibition of acetate‐stimulated neutrophil activation.

Conclusion

Based on these results, a proof‐of‐concept study was initiated to evaluate the safety, tolerability and efficacy of GLPG0974 in patients with mild to moderate ulcerative colitis.

Gαi2 and Gαi3 Differentially Regulate Arrest from Flow and Chemotaxis in Mouse Neutrophils

Leukocyte recruitment to inflammation sites progresses in a multistep cascade. Chemokines regulate multiple steps of the cascade, including arrest, transmigration, and chemotaxis. The most important chemokine receptor in mouse neutrophils is CXCR2, which couples through Gαi2- and Gαi3-containing heterotrimeric G proteins. Neutrophils arrest in response to CXCR2 stimulation. This is defective in Gαi2-deficient neutrophils. In this study, we show that Gαi3-deficient neutrophils showed reduced transmigration but normal arrest in mice. We also tested Gαi2- or Gαi3-deficient neutrophils in a CXCL1 gradient generated by a microfluidic device. Gαi3-, but not Gαi2-, deficient neutrophils showed significantly reduced migration and directionality. This was confirmed in a model of sterile inflammation in vivo. Gαi2-, but not Gαi3-, deficient neutrophils showed decreased Ca(2+) flux in response to CXCR2 stimulation. Conversely, Gαi3-, but not Gαi2-, deficient neutrophils exhibited reduced AKT phosphorylation upon CXCR2 stimulation. We conclude that Gαi2 controls arrest and Gαi3 controls transmigration and chemotaxis in response to chemokine stimulation of neutrophils.

Cytokines as Early Markers of Colorectal Anastomotic Leakage: A Systematic Review and Meta-Analysis

Purpose. Colorectal anastomotic leakage (CAL) is one of the most severe complications after colorectal surgery. This meta-analysis evaluates whether systemic or peritoneal inflammatory cytokines may contribute to early detection of CAL. Methods. Systematic literature search was performed in the acknowledged medical databases according to the PRISMA guidelines to identify studies evaluating systemic and peritoneal levels of TNF, IL-1β, IL-6, and IL-10 for early detection of CAL. Means and standard deviations of systemic and peritoneal cytokine levels were extracted, respectively, for patients with and without CAL. The meta-analysis of the mean differences was carried out for each postoperative day using Review Manager. Results. Seven articles were included. The meta-analysis was performed with 5 articles evaluating peritoneal cytokine levels. Peritoneal levels of IL-6 were significantly higher in patients with CAL compared to patients without CAL on postoperative days 1, 2, and 3 (P < 0.05). Similar results were found for peritoneal levels of TNF but on postoperative days 3, 4, and 5 (P < 0.05). The articles regarding systemic cytokine levels did not report any significant difference accordingly. Conclusion. Increased postoperative levels of peritoneal IL-6 and TNF are significantly associated with CAL and may contribute to its early detection.