Coexpression of GMP-140 and PAF by endothelium stimulated by histamine or thrombin: a juxtacrine system for adhesion and activation of neutrophils

Buffalo bbu-miR-493-5p Promotes Myoblast Proliferation and Differentiation

In recent years, the meat and dairy value of buffaloes has become a major concern in buffalo breeding, and the improvement of buffalo beef quality is key to protecting buffalo germplasm resources and solving the problem of beef supply. MiRNAs play a significant role in regulating muscle development. However, the precise mechanism by which they regulate the development of buffalo skeletal muscles remains largely unexplored. In this study, we examined miRNA expression profiles in buffalo myoblasts during the proliferation and differentiation stages. A total of 177 differentially expressed miRNAs were identified, out of which 88 were up-regulated and 89 down-regulated. We focused on a novel miRNA, named bbu-miR-493-5p, that was significantly differentially expressed during the proliferation and differentiation of buffalo myoblasts and highly expressed in muscle tissues. The RNA-FISH results showed that bbu-miR-493-5p was primarily located in the cytoplasm to encourage buffalo myoblasts' proliferation and differentiation. In conclusion, our study lays the groundwork for future research into the regulatory role of miRNAs in the growth of buffalo muscle.

Cellular and molecular mechanisms in COVID-19 coagulopathy: role of inflammation and endotheliopathy

INTRODUCTION

Coronavirus 2 (CoV-2) infection or coronavirus disease 2019 (COVID-19) is frequently associated with microvascular thrombosis.The microthrombosis in COVID-19 is the result of the interplay between inflammation and endotheliopathy. Elevated interleukin-6 (IL-6) characterizes COVID-19 inflammation resulting in endotheliopathy and coagulopathy marked by elevated D-dimer (DD). Aim of this study is to identify and to describe the coagulation changes in 100 moderate COVID-19 patients having lung involvement and to determine the association of coagulopathy with the severity and prognosis.

METHODS

Inflammation, endothelial and coagulation molecules were measured in moderate and mild disease.

RESULTS

IL-6 and tumor necrosis factor-α (TNF-α) and tissue factor (TF), von Willebrand factor (VWF), and tissue factor pathway inhibitor (TFPI) significantly increased in moderate disease as well as D-dimer, thrombin antithrombin complex (TAT), Fibrinogen (Fib), platelet factor-4 (PF4), β-thromboglobulin (β-TG), P-selectin, and platelet adhesion. Shortened clotting time (CT) and clot formation time (CFT), high maximum clot firmness (MCF) and low LY at 30 min were present in 100% of moderate COVID-19 patients compared with mild COVID-19 patients.

CONCLUSIONS

These findings demonstrate that moderate COVID-19 has a profound inflammation associated with severee ndotheliopathy and intense coagulation activation uncontrolled by TFPI. Attention should be paid to coagulopathy in COVID-19. Closely monitoring of coagulation and application of appropriate anticoagulation may improve the prognosis of moderate COVID-19 and to prevent the progression to severe COVID-19 disease.

Vascular Endothelial Cells: Heterogeneity and Targeting Approaches

Forming the inner layer of the vascular system, endothelial cells (ECs) facilitate a multitude of crucial physiological processes throughout the body. Vascular ECs enable the vessel wall passage of nutrients and diffusion of oxygen from the blood into adjacent cellular structures. ECs regulate vascular tone and blood coagulation as well as adhesion and transmigration of circulating cells. The multitude of EC functions is reflected by tremendous cellular diversity. Vascular ECs can form extremely tight barriers, thereby restricting the passage of xenobiotics or immune cell invasion, whereas, in other organ systems, the endothelial layer is fenestrated (e.g., glomeruli in the kidney), or discontinuous (e.g., liver sinusoids) and less dense to allow for rapid molecular exchange. ECs not only differ between organs or vascular systems, they also change along the vascular tree and specialized subpopulations of ECs can be found within the capillaries of a single organ. Molecular tools that enable selective vascular targeting are helpful to experimentally dissect the role of distinct EC populations, to improve molecular imaging and pave the way for novel treatment options for vascular diseases. This review provides an overview of endothelial diversity and highlights the most successful methods for selective targeting of distinct EC subpopulations.

The lipid biology of sepsis

Sepsis, defined as the dysregulated immune response to an infection leading to organ dysfunction, is one of the leading causes of mortality around the globe. Despite the significant progress in delineating the underlying mechanisms of sepsis pathogenesis, there are currently no effective treatments or specific diagnostic biomarkers in the clinical setting. The perturbation of cell signaling mechanisms, inadequate inflammation resolution, and energy imbalance, all of which are altered during sepsis, are also known to lead to defective lipid metabolism. The use of lipids as biomarkers with high specificity and sensitivity may aid in early diagnosis and guide clinical decision making. In addition, identifying the link between specific lipid signatures and their role in sepsis pathology may lead to novel therapeutics. In this review, we discuss the recent evidence on dysregulated lipid metabolism both in experimental and human sepsis focused on bioactive lipids, fatty acids, and cholesterol as well as the enzymes regulating their levels during sepsis. We highlight not only their potential roles in sepsis pathogenesis but also the possibility of using these respective lipid compounds as diagnostic and prognostic biomarkers of sepsis.

Effect of acyl and alkyl analogs of platelet-activating factor on inflammatory signaling

Platelet-activating factor (PAF), a bioactive ether phospholipid with significant pro-inflammatory properties, was identified almost half a century ago. Despite extensive study of this autocoid, therapeutic strategies for targeting its signaling components have not been successful, including the recent clinical trials with darapladib, a drug that targets plasma PAF-acetylhydrolase (PAF-AH). We recently provided experimental evidence that the previously unrecognized acyl analog of PAF, which is concomitantly produced along with PAF during biosynthesis, dampens PAF signaling by acting both as a sacrificial substrate for PAF-AH and probably as an endogenous PAF-receptor antagonist/partial agonist. If this is the scenario in vivo, PAF-AH needs to catalyze the selective hydrolysis of alkyl-PAF and not acyl-PAF. Accordingly, different approaches are needed for treating inflammatory diseases in which PAF signaling is implicated. The interplay between acyl-PAF, alkyl-PAF, PAF-AH, and PAF-R is complex, and the outcome of this interplay has not been previously appreciated. In this review, we discuss this interaction based on our recent findings. It is very likely that the relative abundance of acyl and alkyl-PAF and their interactions with PAF-R in the presence of their hydrolyzing enzyme PAF-AH may exert a modulatory effect on PAF signaling during inflammation.

Selectins-The Two Dr. Jekyll and Mr. Hyde Faces of Adhesion Molecules-A Review

Selectins belong to a group of adhesion molecules that fulfill an essential role in immune and inflammatory responses and tissue healing. Selectins are glycoproteins that decode the information carried by glycan structures, and non-covalent interactions of selectins with these glycan structures mediate biological processes. The sialylated and fucosylated tetrasaccharide sLe^x is an essential glycan recognized by selectins. Several glycosyltransferases are responsible for the biosynthesis of the sLe^x tetrasaccharide. Selectins are involved in a sequence of interactions of circulated leukocytes with endothelial cells in the blood called the adhesion cascade. Recently, it has become evident that cancer cells utilize a similar adhesion cascade to promote metastases. However, like Dr. Jekyll and Mr. Hyde’s two faces, selectins also contribute to tissue destruction during some infections and inflammatory diseases. The most prominent function of selectins is associated with the initial stage of the leukocyte adhesion cascade, in which selectin binding enables tethering and rolling. The first adhesive event occurs through specific non-covalent interactions between selectins and their ligands, with glycans functioning as an interface between leukocytes or cancer cells and the endothelium. Targeting these interactions remains a principal strategy aimed at developing new therapies for the treatment of immune and inflammatory disorders and cancer. In this review, we will survey the significant contributions to and the current status of the understanding of the structure of selectins and the role of selectins in various biological processes. The potential of selectins and their ligands as therapeutic targets in chronic and acute inflammatory diseases and cancer will also be discussed. We will emphasize the structural characteristic of selectins and the catalytic mechanisms of glycosyltransferases involved in the biosynthesis of glycan recognition determinants. Furthermore, recent achievements in the synthesis of selectin inhibitors will be reviewed with a focus on the various strategies used for the development of glycosyltransferase inhibitors, including substrate analog inhibitors and transition state analog inhibitors, which are based on knowledge of the catalytic mechanism.

Endothelial signaling by neutrophil-released oncostatin M enhances P-selectin-dependent inflammation and thrombosis

In the earliest phase of inflammation, histamine and other agonists rapidly mobilize P-selectin to the apical membranes of endothelial cells, where it initiates rolling adhesion of flowing neutrophils. Clustering of P-selectin in clathrin-coated pits facilitates rolling. Inflammatory cytokines typically signal by regulating gene transcription over a period of hours. We found that neutrophils rolling on P-selectin secreted the cytokine oncostatin M (OSM). The released OSM triggered signals through glycoprotein 130 (gp130)-containing receptors on endothelial cells that, within minutes, further clustered P-selectin and markedly enhanced its adhesive function. Antibodies to OSM or gp130, deletion of the gene encoding OSM in hematopoietic cells, or conditional deletion of the gene encoding gp130 in endothelial cells inhibited neutrophil rolling on P-selectin in trauma-stimulated venules of the mouse cremaster muscle. In a mouse model of P-selectin-dependent deep vein thrombosis, deletion of OSM in hematopoietic cells or of gp130 in endothelial cells markedly inhibited adhesion of neutrophils and monocytes and the rate and extent of thrombus formation. Our results reveal a paracrine-signaling mechanism by which neutrophil-released OSM rapidly influences endothelial cell function during physiological and pathological inflammation.

More Than Just a Removal Service: Scavenger Receptors in Leukocyte Trafficking

Scavenger receptors are a highly diverse superfamily of proteins which are grouped by their inherent ability to bind and internalize a wide array of structurally diverse ligands which can be either endogenous or exogenous in nature. Consequently, scavenger receptors are known to play important roles in host homeostasis, with common endogenous ligands including apoptotic cells, and modified low density lipoproteins (LDLs); additionally, scavenger receptors are key regulators of inflammatory diseases, such as atherosclerosis. Also, as a consequence of their affinity for a wide range of microbial products, their role in innate immunity is also being increasingly studied. However, in this review, a secondary function of a number of endothelial-expressed scavenger receptors is discussed. There is increasing evidence that some endothelial-expressed scavenger receptors are able to directly bind leukocyte-expressed ligands and subsequently act as adhesion molecules in the trafficking of leukocytes in lymphatic and vascular tissues. Here, we cover the current literature on this alternative role for endothelial-expressed scavenger receptors and also speculate on their therapeutic potential.

Protein Biochip Array of Adhesion Molecule Expression in Peripheral Blood of Patients with Nasal Polyposis

Nasal polyposis is a chronic non-infectious inflammatory disease of the nasal and paranasal cavity mucosa of unknown multifactorial origin in which inflammatory cells, and in particular eosinophils, seem to play a pivotal role. Eosinophil migration from the bloodstream to nasal polyps is considered to be specific and is a complex process involving several different molecules such as ICAM-1, VCAM-1, and L-, P- and E-selectins. The aim of this study was to investigate, using a protein biochip array technology, the concentrations of these molecules in the peripheral blood of a group of patients affected by nasal polyposis. Patients exhibited a significantly higher expression of VCAM-1, E-selectin, and L-selectin compared to healthy controls, and Spearman's rank correlation test limited to the molecules with significant between-group differences demonstrated a significant correlation between VCAM-1 and E-selectin, VCAM-1 and L-selectin, and E-selectin and L-selectin. The results of this investigation are in line with those coming from various imunohistochemical analyses, and seem to confirm the role of inflammation in the pathogenesis of nasal polyposis. These molecules may also represent novel therapeutic targets in the treatment of nasal polyps, and may allow the selection of pharmacological prophylactics that would allow effective inhibition of the inflammation induced by a given allergen.

Intravital Imaging of Myeloid Cells: Inflammatory Migration and Resident Patrolling

Myeloid cell recruitment to sites of infection and injury started out as a simple model that has been referred to as the universal concept of leukocyte recruitment. However, as we gain more insight into the different mechanisms, it is becoming clear that each organ and perhaps even each cell has its own unique mechanism of recruitment. Moreover, as the ability to visualize specific cell types in specific organs becomes more accessible, it is also becoming clear that there are resident populations of leukocytes, some within the tissues and others attached to the vasculature of tissues, the latter poised to affect the local environment. In this review, we will first highlight the imaging approaches that have allowed us to gain spectacular insight into locale and function of specific cell types, and then we will discuss what we have learned from this approach as far as myeloid cells are concerned. We will also highlight some of the gaps in our knowledge, which exist almost certainly because of the challenges of being able to visualize certain compartments of the body.

Platelet activating factor-induced expression of p21 is correlated with histone acetylation

Ultraviolet (UV)-irradiated keratinocytes secrete the lipid mediator of inflammation, platelet-activating factor (PAF). PAF plays an essential role in UV-induced immune suppression and skin cancer induction. Dermal mast cell migration from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced PAF activates mast cell migration by up-regulating mast cell CXCR4 surface expression. Recent findings indicate that PAF up-regulates CXCR4 expression via histone acetylation. UV-induced PAF also activates cell cycle arrest and disrupts DNA repair, in part by increasing p21 expression. Do epigenetic alterations play a role in p21 up-regulation? Here we show that PAF increases Acetyl-CREB-binding protein (CBP/p300) histone acetyltransferase expression in a time and dose-dependent fashion. Partial deletion of the HAT domain in the CBP gene, blocked these effects. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the p21 promoter. PAF-treatment had no effect on other acetylating enzymes (GCN5L2, PCAF) indicating it is not a global activator of histone acetylation. This study provides further evidence that PAF activates epigenetic mechanisms to affect important cellular processes, and we suggest this bioactive lipid can serve as a link between the environment and the epigenome.

Platelets in Pulmonary Immune Responses and Inflammatory Lung Diseases

Platelets are essential for physiological hemostasis and are central in pathological thrombosis. These are their traditional and best known activities in health and disease. In addition, however, platelets have specializations that broaden their functional repertoire considerably. These functional capabilities, some of which are recently discovered, include the ability to sense and respond to infectious and immune signals and to act as inflammatory effector cells. Human platelets and platelets from mice and other experimental animals can link the innate and adaptive limbs of the immune system and act across the immune continuum, often also linking immune and hemostatic functions. Traditional and newly recognized facets of the biology of platelets are relevant to defensive, physiological immune responses of the lungs and to inflammatory lung diseases. The emerging view of platelets as blood cells that are much more diverse and versatile than previously thought further predicts that additional features of the biology of platelets and of megakaryocytes, the precursors of platelets, will be discovered and that some of these will also influence pulmonary immune defenses and inflammatory injury.

Expression of E- and P-selectin in Tumor Necrosis Factor—induced Dermatitis in Dogs

Adhesion molecules on endothelial cells play an important role in leukocyte recruitment in several inflammatory processes. Vascular selectins mediate the initial adhesion of leukocytes to the blood vessel wall during their extravasation into inflamed tissues, and in vitro studies in dogs have shown that selectin expression can be induced by cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). The objective of this study was to determine whether vascular selectins are induced by cytokines in vivo in a cutaneous model of inflammation in dogs. Skin biopsies were collected from nine dogs at various time points after an intradermal injection of TNF-α (10 ng/site) or phosphate-buffered saline containing 0.1% bovine serum albumin, and immunohistochemistry was performed using anti-P-selectin (MD3) and anti-E-selectin (CL37) monoclonal antibodies. In all animals, TNF-α induced an inflammatory reaction that was maximal at 12 hours and then decreased by 24 and 48 hours. Control skin displayed no expression of E- and P-selectin, whereas TNF-α induced the expression of P-selectin and E-selectin on dermal vessels that was highest at 12 hours and 3 hours, respectively ( P < 0.05). Numerous platelet aggregates recognized by the anti-P-selectin antibody were present in the lumina of vessels and in perivascular tissues. These results demonstrate that TNF-α can induce the expression of P- and E-selectin in vivo in dog skin and suggest that these selectins are involved in leukocyte recruitment in canine dermatitis.

P-Selectin Expressed by a Human SELP Transgene Is Atherogenic in Apolipoprotein E-Deficient Mice

OBJECTIVE

During inflammation, P-selectin expressed on activated endothelial cells and platelets mediates rolling adhesion of leukocytes. Atherosclerosis-prone mice crossed with P-selectin-deficient (Selp(-/-)) mice develop smaller lesions. Cytokines, such as tumor necrosis factor-α, increase Selp transcripts and augment atherosclerosis in mice. However, they decrease SELP transcripts in humans, challenging assumptions that human P-selectin is atherogenic. We used mice expressing a human SELP transgene to examine the atherogenic role of P-selectin.

APPROACH AND RESULTS

We crossed apolipoprotein E-deficient (Apoe(-/-)) mice with Selp(-/-) mice or transgenic mice expressing the entire human SELP gene (TgSELP(+/-)). Aortas developed larger, macrophage-rich atheromas in Apoe(-/-)Selp(-/-)TgSELP(+/-) mice than in Apoe(-/-)Selp(-/-) mice after 8 or 16 weeks on a Western diet. Confocal microscopy of Apoe(-/-)Selp(-/-)TgSELP(+/-) aortas revealed staining for human P-selectin in endothelial cells overlying atheromas but not in lesional macrophages. We also observed staining for human P-selectin in aortic endothelial cells of 3- to 4-week-old Apoe(-/-)Selp(-/-)TgSELP(+/-) weanlings before atheromas developed. Furthermore, human SELP transcripts were ≈3-fold higher in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) weanlings than in Selp(+/-)TgSELP(+/-) weanlings, whereas murine Selp and Sele transcripts were equivalent in weanlings of both genotypes. Human SELP transcripts in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) mice remained nearly constant during 16 weeks on a Western diet, whereas murine Selp and Sele transcripts progressively increased. Bone marrow transplantation in Apoe(-/-)Selp(-/-) and Apoe(-/-)Selp(-/-)TgSELP(+/-) mice demonstrated that both platelets and endothelial cells must express human P-selectin to promote atherogenesis.

CONCLUSIONS

P-selectin expressed by human SELP is atherogenic in Apoe(-/-) mice, suggesting that P-selectin contributes to atherogenesis in humans.

Accumulation of CD62P during storage of apheresis platelet concentrates and the role of CD62P in transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-associated morbidity and mortality. Activated platelets have important roles in TRALI and CD62P was identified to be an important indicator of platelet activation. However, the precise roles of CD62P in TRALI have remained elusive. The present study assessed CD62P accumulation during storage of apheresis platelet concentrates (A‑Plts) and established a mouse model of TRALI to further investigate the roles of CD62P in TRALI. The results showed that the CD62P concentration in A‑Plts was increased with the storage time. Mice were treated with monoclonal major histocompatibility complex (MHC)‑1 antibody to induce TRALI. The murine model of TRALI was successfully established as evidenced by pulmonary oedema, accompanied by decreased clearance of bronchoalveolar lavage fluid (BALF), increased pulmonary and systemic inflammation, elevated lung myeloperoxidase (MPO) activity as well as increased pulmonary and systemic coagulation in the TRALI group compared with those in the control group. To further determine the role of CD62P in TRALI, mice were treated with anti‑CD62P antibody to knockdown CD62P in vivo. It was found that pulmonary oedema, BALF clearance, pulmonary and systemic inflammation, MPO activity as well as pulmonary and systemic coagulation were decreased in the TRALI + anti‑CD62P antibody group compared with those in the TRALI + isotype antibody group. The present study supported the notion that CD62P is involved in mediating TRALI and may provide an important molecular basis for enhancing the clinical safety and effectiveness of platelet transfusion.

Platelet-Activating Factor Induces Epigenetic Modifications in Human Mast Cells

Ultraviolet (UV) radiation-induced systemic immune suppression is a major risk factor for skin cancer induction. The migration of dermal mast cells from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced keratinocyte-derived platelet-activating factor (PAF) activates mast cell migration, in part by up regulating the expression of CXCR4 on the surface of mast cells. Others have indicated that epigenetic mechanisms regulate CXCR4 expression, so we asked whether PAF activates epigenetic mechanisms in mast cells. Human mast cells were treated with PAF and the effect on DNA methylation and/or acetylation was measured. PAF suppressed the expression of DNA methyltransferase (DNMT) 1 and 3b. On the other hand, PAF increased p300 histone acetyltransferase expression, and the acetylation of histone H3, which coincided with a decreased expression of the histone deacetylase HDAC2. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the CXCR4 promoter. Finally, inhibiting histone acetylation blocked p300 up-regulation and suppressed PAF-induced surface expression of CXCR4. Our findings suggest a novel molecular mechanism for PAF, activation of epigenetic modifications. We suggest that PAF may serve as an endogenous molecular mediator that links the environment (UV radiation) with the epigenome.

Selectins: initiators of leucocyte adhesion and signalling at the vascular wall

The selectins are transmembrane, Ca(2+)-dependent lectins that mediate leucocyte rolling on vascular surfaces, the first adhesive step during inflammation and immune surveillance. Leucocytes express L-selectin, activated platelets express P-selectin, and activated endothelial cells express E- and P-selectin. Rolling involves force-regulated, rapidly reversible interactions of selectins with a limited number of glycosylated cell surface ligands. Rolling permits leucocytes to interact with immobilized chemokines that convert β2 integrins to high-affinity conformations, which mediate arrest, post-arrest adhesion strengthening, and transendothelial migration. However, rolling leucocytes also transduce signals through selectin ligands, the focus of this review. These signals include serial activation of kinases and recruitment of adaptors that convert integrins to intermediate-affinity conformations, which decrease rolling velocities. In vitro, selectin signalling enables myeloid cells to respond to suboptimal levels of chemokines and other agonists. This cooperative signalling triggers effector responses such as degranulation, superoxide production, chemokine synthesis, and release of procoagulant/proinflammatory microparticles. In vivo, selectin-mediated adhesion and signalling likely contributes to atherosclerosis, arterial and deep vein thrombosis, ischaemia-reperfusion injury, and other cardiovascular diseases.

Viscoelasticity and Ultrastructure in Coagulation and Inflammation: Two Diverse Techniques, One Conclusion

The process of blood clotting has been studied for centuries. A synopsis of current knowledge pertaining to haemostasis and the blood components, including platelets and fibrin networks which are closely involved in coagulation, are discussed. Special emphasis is placed on tissue factor (TF), calcium and thrombin since these components have been implicated in both the coagulation process and inflammation. Analysis of platelets and fibrin morphology indicate that calcium, tissue factor and thrombin at concentrations used during viscoelastic analysis (with thromboelastography or TEG) bring about alterations in platelet and fibrin network ultrastructure, which is similar to that seen in inflammation. Scanning electron microscopy indicated that, when investigating platelet structure in disease, addition of TF, calcium or thrombin will mask disease-induced alterations associated with platelet activation. Therefore, washed platelets without any additives is preferred for morphological analysis. Furthermore, morphological and viscoelastic analysis confirmed that thrombin activation is the preferred method of fibrin activation when investigating fibrin network ultrastructure.

Fluid shear stress increases neutrophil activation via platelet-activating factor

Leukocyte exposure to hemodynamic shear forces is critical for physiological functions including initial adhesion to the endothelium, the formation of pseudopods, and migration into tissues. G-protein coupled receptors on neutrophils, which bind to chemoattractants and play a role in neutrophil chemotaxis, have been implicated as fluid shear stress sensors that control neutrophil activation. Recently, exposure to physiological fluid shear stresses observed in the microvasculature was shown to reduce neutrophil activation in the presence of the chemoattractant formyl-methionyl-leucyl-phenylalanine. Here, however, human neutrophil preexposure to uniform shear stress (0.1-2.75 dyn/cm(2)) in a cone-and-plate viscometer for 1-120 min was shown to increase, rather than decrease, neutrophil activation in the presence of platelet activating factor (PAF). Fluid shear stress exposure increased PAF-induced neutrophil activation in terms of L-selectin shedding, αMβ2 integrin activation, and morphological changes. Neutrophil activation via PAF was found to correlate with fluid shear stress exposure, as neutrophil activation increased in a shear stress magnitude- and time-dependent manner. These results indicate that fluid shear stress exposure increases neutrophil activation by PAF, and, taken together with previous observations, differentially controls how neutrophils respond to chemoattractants.

Leukocyte migration into inflamed tissues

Leukocyte migration through activated venular walls is a fundamental immune response that is prerequisite to the entry of effector cells such as neutrophils, monocytes, and effector T cells to sites of infection, injury, and stress within the interstitium. Stimulation of leukocytes is instrumental in this process with enhanced temporally controlled leukocyte adhesiveness and shape-changes promoting leukocyte attachment to the inner wall of blood vessels under hydrodynamic forces. This initiates polarized motility of leukocytes within and through venular walls and transient barrier disruption facilitated sequentially by stimulated vascular cells, i.e., endothelial cells and their associated pericytes. Perivascular cells such as macrophages and mast cells that act as tissue inflammatory sentinels can also directly and indirectly regulate the exit of leukocytes from the vascular lumen. In this review, we discuss current knowledge and open questions regarding the mechanisms involved in the interactions of different effector leukocytes with peripheral vessels in extralymphoid organs.

Inflammation and the blood microvascular system

Acute and chronic inflammation is associated with changes in microvascular form and function. At rest, endothelial cells maintain a nonthrombogenic, nonreactive surface at the interface between blood and tissue. However, on activation by proinflammatory mediators, the endothelium becomes a major participant in the generation of the inflammatory response. These functions of endothelium are modified by the other cell populations of the microvessel wall, namely pericytes, and smooth muscle cells. This article reviews recent advances in understanding the roles played by microvessels in inflammation.

Macrophage derived platelet activating factor implicated in the resolution phase of gouty inflammation

Human blood derived in vitro differentiated monocytes or macrophages are a population of cells which have been investigated over the years to determine the role these cells play in the resolution phase of gout. Macrophages are able to phagocytose monosodium urate monohydrate (MSU) crystals without releasing inflammatory factors. This study analysed macrophage platelet activating factor secretion and its possible role in the pathway of gout resolution. Analysis of sunatants from in vitro differentiated macrophages stimulated with MSU crystals revealed the secretion of platelet activating factor (PAF)  1.54 ± 0.10 mean ± SEM; ng/mL per 10⁶ cells. This secretion was absent in immature monocytes treated similarly. When these monocytes were pretreated with recombinant human PAF-acetylhydrolase (rhuPAF-AH) and MSU crystals resulted in TNFα suppression. Addition of WEB2086, a platelet activating factor (PAF) antagonist, to differentiated macrophages with MSU crystals unmasked TNFα secretion 0.7 ± 0.06 mean ± SEM; ng/mL per 10⁶ cells. This study identifies a role for PAF and the PAF receptor antagonist in the pathway by which macrophages ingest MSU crystals and resolve the concomitant inflammation.

Assessment of the E-selectin rs5361 (561A>C) polymorphism and soluble protein concentration in acute coronary syndrome: association with circulating levels

Introduction. The acute coronary syndrome (ACS) is a complex disease where genetic and environmental factors are involved. E-selectin gene is a candidate for ACS progression due to its contribution in the inflammatory process and endothelial function. The rs5361 (561A>C) polymorphism in the E-selectin gene has been linked to changes in gene expression, affinity for its receptor, and plasmatic levels; therefore it is associated with an increased risk of cardiovascular disease. The aim of this study was to determine the association of the rs5361 polymorphism with ACS and to measure serum levels of soluble E-selectin (sE-selectin). Materials and Methods. 283 ACS patients and 205 healthy subjects (HS) from Western Mexico were included. The polymerase chain reaction-restriction fragment length polymorphism was used to determine the rs5361 polymorphism. The sE-selectin levels were measured by enzyme-linked immunosorbent assay. Results. Neither genotype nor allele frequencies of the rs5361 polymorphism showed statistical differences between groups. The sE-selectin levels were significantly higher in ACS patients compared to HS (54.58 versus 40.41 ng/ml, P = 0.02). The C allele had no effect on sE-selectin levels. Conclusions. The rs5361 E-selectin gene polymorphism is not a susceptibility marker for ACS in Western Mexico population. However, sE-selectin may be a biological marker of ACS.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Lessons from rare maladies: leukocyte adhesion deficiency syndromes

PURPOSE OF REVIEW

The leukocyte adhesion deficiency (LAD) syndromes are rare genetically determined conditions with challenging clinical features. These immunodeficiencies also provide insights that are broadly relevant to the biology of leukocytes, platelets, intercellular interactions, and intracellular signaling. Recent discoveries merit their review in the context of existing knowledge.

RECENT FINDINGS

New activities of β(2) integrins, which are deficient or absent in LAD-I, and new β(2) integrin-dependent functions of neutrophils and other leukocytes have recently been identified. Genetic defects and mechanisms accounting for impaired fucosylation of selectin ligands and defective selectin binding and signaling in LAD-II are now apparent. LAD-III, which presents with bleeding similar to that in Glanzmann thrombasthenia and platelet dysfunction in addition to impaired leukocyte adhesion, is now known to be due to absence of KINDLIN-3, a cytoplasmic protein that acts cooperatively with TALIN-1 in activating β(1), β(2), and β(3) integrins. Understanding of the leukocyte adhesion cascade and interactions of leukocytes with inflamed endothelium, which are impaired in each of the LAD syndromes, continues to be refined.

SUMMARY

Although LAD syndromes are rare maladies, their investigation is generating new knowledge directly applicable to the diagnosis and care of patients and to fundamental paradigms in immunobiology and hemostasis.

Migration of leukocytes across the vascular intima molecules and mechanisms

The process of leukocyte emigration from the blood into a site of inflammation can be dissected into four distinct but continuous stages involving sequential interactions of different adhesion molecules on the leukocyte and endothelial surfaces. Although the molecules mediating adhesion to the luminal surface have been well studied, much less is known about the final stage of this process, transendothelial migration. This is the stage in which a leukocyte bound to the vascular wall passes between adjacent endothelial cells; it is a complex process in its own right, involving continuous structural, mechanical, and biochemical changes in both interacting cell types. Distinct cell adhesion molecule and signal transduction mechanisms that appear to be involved in this phase are discussed here.

The Tie2 receptor antagonist angiopoietin-2 in systemic lupus erythematosus: its correlation with various disease activity parameters

BACKGROUND

Systemic lupus erythematosus is one of the autoimmune diseases characterized by multisystem involvement associated with autoantibody and immune complex vasculitis along with endothelial cell damage.

OBJECTIVE

to study the possible role of Angiopoietin- 2 (Ang-2) as a recently highlighted inflammatory and angiogenic mediator in the pathogenesis of SLE and its correlation with the state of another inflammatory marker, P-Selectin, as well as with various markers of the disease activity.

PATIENTS AND METHODS

The present study included 3 main groups: active SLE patients (group I), inactive SLE patients (group II) and healthy normal control subjects (group III). Groups I and II were subjected to disease activity assessment using the SLEDAI scoring system and measurement of plasma Ang-2 and P-Selectin by ELISA in addition to various laboratory investigations to assess disease activity as: Complete blood count, ESR, serum creatinine, C3, C4 and 24-h urinary proteins.

RESULTS

The mean level of Plasma Ang-2 and P-selectin showed a high significant increase in active group compared to inactive SLE patients and control subjects (p < 0.001).There was a significant positive correlation between Ang-2, P-Selectin, and each of SLEDAI score and 24-h urinary proteins in all SLE patients as well as in the active group, and Ang-2 was a significant independent marker for proteinuria. A significant negative correlation was found between Ang-2, P-Selectin and each of C3, C4. Ang-2 and P-Selectin showed a high sensitivity and specificity in the patients with SLE.

CONCLUSION

Our study suggests that Ang-2 may be a more useful marker than P-Selectin, C3 and C4 in the assessment of disease activity.

The reciprocal relationship between inflammation and coagulation

Inflammation and coagulation constitute two host defense systems with complementary roles in eliminating invading pathogens, limiting tissue damage, and restoring homeostasis. Extensive cross talk exists between these 2 systems, whereby inflammation leads to activation of coagulation, and coagulation considerably affects inflammatory activity. Infection leads to the production of proinflammatory cytokines that, in turn, stimulate the production of tissue factor. Activation of the coagulation system and ensuing thrombin generation are dependent on the expression of tissue factor. Conversely, activated coagulation proteases may affect specific receptors on inflammatory cells and endothelial cells and thereby modulate the inflammatory response. Activation of coagulation with the simultaneous down-regulation of endothelial-bound anticoagulant mechanisms and endogenous fibrinolysis characterizes the pathophysiology of sepsis. The mechanisms by which these highly complex and codependent defense strategies are linked together both in health and disease is the focus of this review.

Rapid histamine-induced neutrophil recruitment is sphingosine kinase-1 dependent

Leukocyte recruitment to sites of inflammation is critical for the development of acute allergic responses. Rapid P-selectin up-regulation by endothelial cells is a key promoter of leukocyte infiltration in response to mediators such as histamine. However, the mechanisms underpinning this process are still incompletely understood. We examined the role of the sphingosine kinase/sphingosine-1-phosphate (SK/S1P) pathway and showed that in human umbilical vein endothelial cells, histamine rapidly activates SK in an extracellular signal-regulated kinase (ERK) 1/2-dependent manner, concurrent with the induction of P-selectin expression. Histamine activated both SK-1 and SK-2 isoforms; inhibition of SK-1, but not SK-2, attenuated histamine-induced P-selectin up-regulation and neutrophil rolling in vitro. S1P receptor antagonists failed to prevent histamine-induced P-selectin expression, and exogenous S1P did not increase P-selectin expression, suggesting that S1P cell surface receptors are not involved in this process. Finally, the role of both SK-1 and SK-2 in histamine-induced leukocyte rolling in vivo was assessed using pharmacological and genetic methods. Consistent with the in vitro findings, mice pretreated with either sphingosine kinase inhibitor or fingolimod (FTY720) significantly attenuated histamine-induced leukocyte rolling in the cremaster muscle. Similarly, Sphk1(-/-) but not Sphk2(-/-) mice exhibited reduced histamine-induced leukocyte rolling. These findings demonstrate a key role for SK-1 in histamine-induced rapid P-selectin up-regulation and associated leukocyte rolling, and suggest that endothelial SK-1 is an important contributor to allergic inflammation.

Platelets: versatile effector cells in hemostasis, inflammation, and the immune continuum

Platelets are chief effector cells in hemostasis. In addition, however, their specializations include activities and intercellular interactions that make them key effectors in inflammation and in the continuum of innate and adaptive immunity. This review focuses on the immune features of human platelets and platelets from experimental animals and on interactions between inflammatory, immune, and hemostatic activities of these anucleate but complex and versatile cells. The experimental findings and evidence for physiologic immune functions include previously unrecognized biologic characteristics of platelets and are paralleled by new evidence for unique roles of platelets in inflammatory, immune, and thrombotic diseases.

The link between vascular features and thrombosis

The mechanisms of vascular control of thrombotic events remain unclear. The vasculature possesses essential anticoagulant factors that regulate coagulation. Because the endothelium-to-blood ratios are much higher in the microcirculation, it is likely that stasis contributes to thrombotic risk, due in large part to failure to rapidly access the microcirculation and to gain access to this highly anticoagulant environment. Inflammation can potentiate thrombosis in part through downregulation of the vascular anticoagulants, a process that appears to be exacerbated in aging, a well-known risk factor for thrombosis. Surgery and trauma, two major risk factors for thrombosis, result in the release of a variety of cellular components that trigger coagulation through separate mechanisms.

Upregulation of coronary endothelial P-selectin in a monkey heart ischemia reperfusion model

The design of targeted ultrasound contrast agents for molecular imaging of myocardial ischemia-reperfusion (IR) requires the availability of an adequate in vivo model in a species in which cross reactivity with the target occurs. P-selectin (Psel) is an activation-dependent endothelial receptor that supports rapid and reversible cell adhesion in a flowing system. Together with E- and L-selectins it constitutes the selectin family of adhesion molecules. We investigated the myocardial expression of selectins in a closed chest minimally invasive monkey myocardial IR model. Catheter-based occlusion (30-50 min) followed by reperfusion (3 or 5 h) of left anterior descending artery (LAD) was performed in anesthetised monkeys. At the end of each procedure animals were killed, and their hearts were excised. The tissues were analyzed immunohistochemically using an anti-human Psel antibody (AK-6 clone) that cross reacts with rhesus monkey. Histopathological features confirm the presence of IR injuries in myocardial tissues. There was significant increase in the Psel expression in vessels from the IR areas. However, significantly higher Psel immunoreactivity was also seen in areas which are distant from IR injuries.

Integrin-independent role of CalDAG-GEFI in neutrophil chemotaxis

Chemotaxis and integrin activation are essential processes for neutrophil transmigration in response to injury. CalDAG-GEFI plays a key role in the activation of beta1, beta2, and beta3 integrins in platelets and neutrophils by exchanging a GDP for a GTP on Rap1. Here, we explored the role of CalDAG-GEFI and Rap1b in integrin-independent neutrophil chemotaxis. In a transwell assay, CalDAG-GEFI-/- neutrophils had a 46% reduction in transmigration compared with WT in response to a low concentration of LTB4. Visualization of migrating neutrophils in the presence of 10 mM EDTA revealed that CalDAG-GEFI-/- neutrophils had abnormal chemotactic behavior compared with WT neutrophils, including reduced speed and directionality. Interestingly, Rap1b-/- neutrophils had a similar phenotype in this assay, suggesting that CalDAG-GEFI may be acting through Rap1b. We investigated whether the deficit in integrin-independent chemotaxis in CalDAG-GEFI-/- neutrophils could be explained by defective cytoskeleton rearrangement. Indeed, we found that CalDAG-GEFI-/- neutrophils had reduced formation of F-actin pseudopodia after LTB4 stimulation, suggesting that they have a defect in polarization. Overall, our studies show that CalDAG-GEFI helps regulate neutrophil chemotaxis, independent of its established role in integrin activation, through a mechanism that involves actin cytoskeleton and cellular polarization.

Role of nitroso radicals as drug targets in circulatory shock

A vast amount of circumstantial evidence implicates oxygen-derived free radicals (especially, superoxide and hydroxyl radical) and high-energy oxidants [such as peroxynitrite (OONO(-))] as mediators of shock and ischaemia/reperfusion injury. Reactive oxygen species can initiate a wide range of toxic oxidative reactions. These include initiation of lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3 phosphate dehydrogenase, inhibition of membrane sodium/potassium adenosine 5'-triphosphate-ase activity, inactivation of membrane sodium channels and other oxidative modifications of proteins. All these toxicities are likely to play a role in the pathophysiology of shock and ischaemia and reperfusion. Moreover, various studies have clearly shown that treatment with either OONO(-) decomposition catalysts, which selectively inhibit OONO(-), or with superoxide dismutase (SOD) mimetics, which selectively mimic the catalytic activity of the human SOD enzymes, have been shown to prevent in vivo the delayed vascular decompensation and the cellular energetic failure associated with shock and ischaemia/reperfusion injury.

Expression patterns of angiopoietin-1, -2, and tie-2 receptor in ulcerative colitis support involvement of the angiopoietin/tie pathway in the progression of ulcerative colitis

The active stage of ulcerative colitis (UC) involves transmigration of polymorphonuclear (PMN) cells to colonic epithelia. The angiopoietin (Ang) pathway plays a role as the regulator of PMN transmigration. To clarify the role of the Ang/Tie pathway in the activation of UC, especially in cypt abscess formation, 67 tissue samples were obtained from patients with UC and ten controls without UC for immunohistochemical analysis for the expression of Ang-1, -2, or Tie-2. The epithelia of crypt abscess was strongly positive for Ang-1 and -2 for all 57 samples derived from patients with active UC, though the colorectal epithelium without crypt abscess showed minimal expression of Ang-1, -2, and Tie-2. Numerous transepithelial migrating PMN cells in crypt abscesses also expressed Tie-2. The specimens of UC patients in remission showed significantly less immunoreactivity for Ang-1, -2, or Tie-2. These findings suggest that the Ang/Tie pathway may play a role in the progression of UC.

P-selectin expression in cold preserved kidneys in University of Wisconsin and histidine-tryptophan-ketoglutarate solutions

The differences and efficacy of standard preservation solutions in kidney transplantation, University of Wisconsin (UW) and histidine-tryptophan-ketoglutarate (HTK), remain a topic of debate in recent clinical studies. P-selectins represent glycoproteins expressed on endothelial cells and platelets responsible for the earliest events in ischemia/reperfusion injury in kidney transplantation. This study aimed to compare the levels of P-selectin expression between cold preserved kidney tissues in UW and HTK solutions. Thirty kidneys were procured from male Lewis rats and stored in cold (4°C) solutions for periods of 4, 12, 16, 20, and 24h. Group 1 (n=15) kidneys were stored in UW solutions, and group 2 (n=15) kidneys were submerged in HTK solutions. At the end of each time point, the kidneys underwent preparation and levels of P-selectin expression in the tissues were measured using Immunoblot analyses and adjusted volumetric quantification of Western blot signals. For all periods of cold preservation, P-selectin expression was significantly down-regulated in kidney tissues stored in UW compared with HTK solutions (P<0.001). In summary, UW demonstrated a significant benefit over HTK solution in down-regulating P-selectin expression in cold preserved kidney grafts.

Amniotic fluid angiopoietin-2 in term and preterm parturition, and intra-amniotic infection/inflammation

OBJECTIVE

Recent observations have revealed an interaction between inflammation and angiogenesis, which may be mediated by angiopoietins and chemokines. Given the importance of inflammation in parturition, we sought to determine whether angiopoietin-2 (Ang-2) is present in amniotic fluid (AF) and if its concentration changes with gestational age, labor, and in intra-amniotic infection/inflammation (IAI) in patients with spontaneous preterm labor and intact membranes.

STUDY DESIGN

This cross-sectional study included 486 patients in the following groups: 1) women in the mid-trimester of pregnancy (14-18 weeks) who underwent amniocentesis for genetic indications and delivered a normal neonate at term (n=52); 2) normal pregnant women at term with (n=48) and without (n=45) spontaneous labor; 3) patients with an episode of spontaneous preterm labor (PTL) and intact membranes who were classified into: a) PTL without IAI who delivered at term (n=152); b) PTL without IAI who delivered preterm (<37 weeks gestation; n=107); and c) PTL with IAI (n=82). Ang-2 concentration in AF was determined by enzyme-linked immunoassay. Non-parametric statistics were used for analysis.

RESULTS

1) Ang-2 was detected in all AF samples; 2) the median AF Ang-2 concentration at term was significantly lower than that in the mid-trimester (1877.4 pg/mL vs. 3525.2 pg/mL; P<0.001); 3) among patients with PTL, the median AF Ang-2 concentration was significantly higher in patients with IAI than in those without IAI (4031.3 pg/mL vs. 2599.4 pg/mL; P<0.001) and those with PTL without IAI who delivered at term (4031.3 pg/mL vs. 2707.3 pg/mL; P<0.001); and 4) no significant differences were observed in the median AF Ang-2 concentration between patients with spontaneous labor at term and those at term not in labor (1722.9 pg/mL vs. 1877.4 pg/mL; P=0.6).

CONCLUSIONS

1) Ang-2, a protein involved in the process of vascular remodeling, is a physiologic constituent of the amniotic fluid and its concentration decreased with advancing gestation; 2) the median Ang-2 concentration in amniotic fluid is higher in patients with IAI than in those without; and 3) spontaneous parturition at term is not associated with changes in the AF concentration of Ang-2. These findings support the view of a link between angiopoietins and inflammation.

Leukocyte adhesion molecules in animal models of inflammatory bowel disease

The dysregulated recruitment of leukocytes into the intestine is required for the initiation and maintenance of inflammatory bowel disease (IBD). Several families of molecules regulate the influx of these cells into sites of inflammation. Interference with some of these molecules has already shown efficacy in the clinics and antibodies that target the molecules involved have been approved by the FDA for use in Crohn's disease (CD), multiple sclerosis (i.e., natalizumab), and psoriasis (i.e., efalizumab). Here, we discuss basic aspects of the different families of relevant molecules and compile a large body of preclinical studies that supported the targeting of specific steps of the leukocyte adhesion cascade for therapeutic purposes in colitis and in novel models of CD-like ileitis.

Regulation of endothelial barrier function by reactive oxygen and nitrogen species

Excessive generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), by activated neutrophils and endothelial cells, has been implicated in the pathophysiology of endothelial barrier dysfunction. Disruption of the integrity of this barrier markedly increases permeability to fluids, solutes and inflammatory cells and is the hallmark of many disorders such as acute lung injury (ALI) and sepsis. There has been considerable progress in our understanding of the sequence of molecular and structural events that mediate the response of endothelial cells to oxidants and nitrosants. In addition, substantial experimental evidence demonstrates improvement of endothelial barrier dysfunction with antioxidant strategies. However, no significant benefits have been observed, so far, in clinical trials of antioxidants for the treatment of endothelial barrier dysfunction. This article will review the available evidence implicating ROS and RNS in endothelial barrier dysfunction, explore potential underlying mechanisms, and identify areas of further research.

Integrin alpha(v)beta(3) on human endothelial cells binds von Willebrand factor strings under fluid shear stress

Acutely secreted von Willebrand factor (VWF) multimers adhere to endothelial cells, support platelet adhesion, and may induce microvascular thrombosis. Immunofluorescence microscopy of live human umbilical vein endothelial cells showed that VWF multimers rapidly formed strings several hundred micrometers long on the cell surface after stimulation with histamine. Unexpectedly, only a subset of VWF strings supported platelet binding, which depended on platelet glycoprotein Ib. Electron microscopy showed that VWF strings often consisted of bundles and networks of VWF multimers, and each string was tethered to the cell surface by a limited number of sites. Several approaches implicated P-selectin and integrin alpha(v)beta(3) in anchoring VWF strings. An RGDS peptide or a function-blocking antibody to integrin alpha(v)beta(3) reduced the number of VWF strings formed. In addition, integrin alpha(v) decorated the VWF strings by immunofluorescence microscopy. Furthermore, lentiviral transduction of shRNA against the alpha(v) subunit reduced the expression of cell-surface integrin alpha(v)beta(3) and impaired the ability of endothelial cells to retain VWF strings. Soluble P-selectin reduced the number of platelet-decorated VWF strings in the absence of Ca(2+) and Mg(2+) but had no effect in the presence of these cations. These results indicate that VWF strings bind specifically to integrin alpha(v)beta(3) on human endothelial cells.

Potential mechanism for recruitment and migration of CD133 positive cells to areas of vascular inflammation

OBJECTIVE

Mast cells are found in large numbers in atherosclerotic plaques. The present study was conducted to determine whether tryptase stimulation of human coronary artery endothelial cells (HCAEC) would lead to an increase in transmigration of CD133 positive cells (CD133+). In vitro these cells can differentiate into mast cells under the influence of specific cytokines and growth factors.

METHODS AND RESULTS

CD133+ cells were isolated from umbilical cord blood. They express mRNA for several adhesion molecules that are also utilized in neutrophil migration and can migrate across an HCAEC monolayer. Migration increased significantly when HCAEC were stimulated with tryptase and decreased when CD133+ cells were pretreated with CV3988, a platelet activating factor receptor (PTAFR) antagonist. Following long-term cell culture, these cells stained positively for the presence of tryptase, a mast cell enzyme.

CONCLUSION

CD133+ cells can be utilized as a mast cell precursor population. The transendothelial migration is facilitated by the presence of tryptase and may utilize the PAF/PTAFR interaction in a manner similar to that involved in neutrophil transmigration. Following transmigration, a subset of these progenitor cells may mature into mast cells in the subendothelial space and play a role in propagation of the inflammatory process in atherosclerosis.

Blood coagulation, inflammation, and malaria

Malaria remains a highly prevalent disease in more than 90 countries and accounts for at least 1 million deaths every year. Plasmodium falciparum infection is often associated with a procoagulant tonus characterized by thrombocytopenia and activation of the coagulation cascade and fibrinolytic system; however, bleeding and hemorrhage are uncommon events, suggesting that a compensated state of blood coagulation activation occurs in malaria. This article (i) reviews the literature related to blood coagulation and malaria in a historic perspective, (ii) describes basic mechanisms of coagulation, anticoagulation, and fibrinolysis, (iii) explains the laboratory changes in acute and compensated disseminated intravascular coagulation (DIC), (iv) discusses the implications of tissue factor (TF) expression in the endothelium of P. falciparum infected patients, and (v) emphasizes the procoagulant role of parasitized red blood cells (RBCs) and activated platelets in the pathogenesis of malaria. This article also presents the Tissue Factor Model (TFM) for malaria pathogenesis, which places TF as the interface between sequestration, endothelial cell (EC) activation, blood coagulation disorder, and inflammation often associated with the disease. The relevance of the coagulation-inflammation cycle for the multiorgan dysfunction and coma is discussed in the context of malaria pathogenesis.

Sodium/hydrogen exchange inhibition with cariporide reduces leukocyte adhesion via P-selectin suppression during inflammation

BACKGROUND AND PURPOSE

The Na(+)/H(+) exchange (NHE) inhibitor cariporide is known to ameliorate ischaemia/reperfusion (I/R) injury by reduction of cytosolic Ca(2+) overload. Leukocyte activation and infiltration also mediates I/R injury but whether cariporide reduces I/R injury by affecting leukocyte activation is unknown. We studied the effect of cariporide on thrombin and I/R induced leukocyte activation and infiltration models and examined P-selectin expression as a potential mechanism for any identified effects.

EXPERIMENTAL APPROACH

An in vivo rat mesenteric microcirculation microscopy model was used with stimulation by thrombin (0.5 micro ml(-1)) superfusion or ischaemia (by haemorrhagic shock for 60 min) and reperfusion (90 min).

KEY RESULTS

Treatment with cariporide (10 mg kg(-1) i.v.) significantly reduced leukocyte rolling, adhesion and extravasation after thrombin exposure. Similarly, cariporide reduced leukocyte rolling (54+/-6.2 to 2.4+/-1.0 cells min(-1), P<0.01), adherence (6.3+/-1.9 to 1.2+/-0.4 cells 100 microm(-1), P<0.01) and extravasation (9.1+/-2.1 to 2.4+/-1.1 cells per 20 x 100 microm perivascular space, P<0.05), following haemorrhagic shock induced systemic ischaemia and reperfusion. The cell adhesion molecule P-selectin showed a profound decrease in endothelial expression following cariporide administration in both thrombin and I/R stimulated groups (35.4+/-3.2 vs 14.2+/-4.1% P-selectin positive cells per tissue section, P<0.01).

CONCLUSIONS AND IMPLICATIONS

The NHE inhibitor cariporide is known to limit reperfusion injury by controlling Ca(2+) overload but these data are novel evidence for a vasculoprotective effect of NHE inhibition at all levels of leukocyte activation, an effect which is likely to be mediated at least in part by a reduction of P-selectin expression.

The role of histamine H1 and H4 receptors in allergic inflammation: the search for new antihistamines

Histamine has a key role in allergic inflammatory conditions. The inflammatory responses resulting from the liberation of histamine have long been thought to be mediated by the histamine H1 receptor, and H1-receptor antagonists--commonly known as antihistamines--have been used to treat allergies for many years. However, the importance of histamine in the pathology of conditions such as asthma and chronic pruritus may have been underestimated. Here, we review accumulating evidence suggesting that histamine indeed has roles in inflammation and immune function modulation in such diseases. In particular, the discovery of a fourth histamine receptor (H4) and its expression on numerous immune and inflammatory cells has prompted a re-evaluation of the actions of histamine, suggesting a new potential for H4-receptor antagonists and a possible synergy between H1 and H4-receptor antagonists in targeting various inflammatory conditions.