Cellular adhesion and the endothelium: P-selectin

Evidence for control of cerebral neurovascular function by circulating platelets in healthy older adults

Platelets play a vital role in preventing haemorrhage through haemostasis, but complications arise when platelets become overly reactive, leading to pathophysiology such as atherothrombosis. Elevated haemostatic markers are linked to dementia and predict its onset in long-term studies. Despite epidemiological evidence, the mechanism linking haemostasis with early brain pathophysiology remains unclear. Here, we aimed to determine whether a mechanistic association exists between platelet function and cerebral neurovascular function in 52 healthy mid- to older-age adults. To do this, we combined, for the first time, magnetic resonance imaging of cerebral neurovascular function, peripheral vascular physiology and in vitro platelet assaying. We show an association between platelet reactivity and cerebral neurovascular function that is both independent of vascular reactivity and mechanistically specific: Distinct platelet signalling mechanisms (ADP, collagen-related peptide, thrombin receptor activator peptide 6) were associated with different physiological components of the haemodynamic response to neuronal (visual) stimulation (full-width half-maximum, time to peak, area under the curve), an association that was not mediated by peripheral vascular effects. This finding challenges the previous belief that systemic vascular health determines the vascular component of cerebral neurovascular function, highlighting a specific link between circulating platelets and the neurovascular unit. Because altered cerebral neurovascular function marks the initial stages of neurodegenerative pathophysiology, understanding this novel association is now imperative, with the potential to lead to a significant advancement in our comprehension of early dementia pathophysiology. KEY POINTS: Haemostasis (platelet function) has been linked to the early stages of dementia, but the precise mechanisms are not well understood. This study considers whether a causal mechanism exists through atherothrombotic effects on the vasculature which can in turn affect brain health, or through platelet-specific interactions with brain physiology. Here, we show that elevated platelet reactivity is associated with blunted (delayed, shorter and smaller) cerebral blood flow responses to neuronal activation in healthy middle-aged and older adults. However, the association between platelet reactivity and cerebral neurovascular function was not mediated by systemic vascular reactivity. This finding challenges the previous belief that systemic vascular health determines the vascular component of cerebral neurovascular function, highlighting a specific link between circulating platelets and the neurovascular unit in early dementia pathophysiology.

The endothelium at the interface between tissues and Staphylococcus aureus in the bloodstream

SUMMARYStaphylococcus aureus is a major human pathogen. It can cause many types of infections, in particular bacteremia, which frequently leads to infective endocarditis, osteomyelitis, sepsis, and other debilitating diseases. The development of secondary infections is based on the bacterium's ability to associate with endothelial cells lining blood vessels. The success of endothelial colonization and infection by S. aureus relies on its ability to express a wide array of cell wall-anchored and secreted virulence factors. Establishment of endothelial infection by the pathogen is a multistep process involving adhesion, invasion, extravasation, and dissemination of the bacterium into surrounding tissues. The process is dependent on the type of endothelium in different organs (tissues) and pathogenetic potential of the individual strains. In this review, we report an update on the organization of the endothelium in the vessels, the structure and function of the virulence factors of S. aureus, and the several aspects of bacteria-endothelial cell interactions. After these sections, we will discuss recent advances in understanding the specific mechanisms of infections that develop in the heart, bone and joints, lung, and brain. Finally, we describe how neutrophils bind to endothelial cells, migrate to the site of infection to kill bacteria in the tissues, and how staphylococci counteract neutrophils' actions. Knowledge of the molecular details of S. aureus-endothelial cell interactions will promote the development of new therapeutic strategies and tools to combat this formidable pathogen.

A bone to pick-cellular and molecular mechanisms of bone pain in sickle cell disease

The bone is one of the most commonly affected organs in sickle cell disease (SCD). Repeated ischemia, oxidative stress and inflammation within the bone is largely responsible for promoting bone pain. As more individuals with SCD survive into adulthood, they are likely to experience a synergistic impact of both aging and SCD on their bone health. As bone health deteriorates, bone pain will likely exacerbate. Recent mechanistic and observational studies emphasize an intricate relationship between bone remodeling and the peripheral nervous system. Under pathological conditions, abnormal bone remodeling plays a key role in the propagation of bone pain. In this review, we first summarize mechanisms and burden of select bone complications in SCD. We then discuss processes that contribute to pathological bone pain that have been described in both SCD as well as non-sickle cell animal models. We emphasize the role of bone-nervous system interactions and pitfalls when designing new therapies especially for the sickle cell population. Lastly, we also discuss future basic and translational research in addressing questions about the complex role of stress erythropoiesis and inflammation in the development of SCD bone complications, which may lead to promising therapies and reduce morbidity in this vulnerable population.

Single-cell transcriptomics uncover hub genes and cell-cell crosstalk in patients with hypertensive nephropathy

Hypertensive nephropathy (HTN) is one of the leading causes of end-stage renal disease, yet the molecular mechanisms are still unknown. To explore novel mechanisms and gene targets for HTN, the gene expression profiles of renal biopsy samples obtained from 2 healthy living donor controls and 5 HTN patients were determined by single-cell RNA sequencing. Key hub genes expression were validated by the Nephroseq v5 platform. The HTN endothelium upregulated cellular adhesion genes (ICAM2 and CEACAM1), inflammatory genes (ETS2 and IFI6) and apoptosis related genes (CNN3). Proximal tubules in HTN highly expressed hub genes including BBOX1, TPM1, TMSB10, SDC4, and NUP58, which might be potential novel targets for proximal tubular injury. The upregulated genes in tubules of HTN were mainly participating in inflammatory signatures including IFN-γ signature, NF-κB signaling, IL-12 signaling and Wnt signaling pathway. Receptor-ligand interaction analysis indicated potential cell-cell crosstalk between endothelial cells or mesangial cells with other renal resident cells in HTN. Together, our data identify a distinct cell-specific gene expression profile, pathogenic inflammatory signaling and potential cell-cell communications between endothelial cells or mesangial cells with other renal resident cells in HTN. These findings may provide a promising novel landscape for mechanisms and treatment of human HTN.

Crizanlizumab in sickle cell disease

Vaso-occlusion in sickle cell disease (SCD) leads to a myriad of manifestations driving morbidity and mortality in patients with SCD. Increased leucocyte adhesion and P-selectin expression on platelets and endothelial cells is an inciting event that leads to obstruction of microcirculation by adhesion with rigid sickled red blood cells. Crizanlizumab is a first-in-class monoclonal antibody that inhibits P-selectin and has been shown to decrease the frequency of vaso-occlusive pain crises in patients with SCD in clinical trials. The role of crizanlizumab in other manifestations of SCD still needs further investigation.

A phase 1 study in healthy participants to characterize the safety and pharmacology of inclacumab, a fully human anti-P-selectin antibody, in development for treatment of sickle cell disease

PURPOSE

We evaluated the safety, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of intravenous (IV) inclacumab, a fully human IgG4 anti-P-selectin monoclonal antibody in development for the treatment of sickle cell disease, at doses up to and exceeding those previously tested in healthy individuals.

METHODS

In this phase 1, open-label, single-ascending-dose study, 15 healthy participants were enrolled into cohorts receiving 20 mg/kg (n = 6) or 40 mg/kg (n = 9) IV inclacumab and observed for up to 29 weeks post-dose. Safety, PK parameters, thrombin receptor-activating peptide (TRAP)-activated platelet-leukocyte aggregate (PLA) formation, P-selectin inhibition, plasma soluble P-selectin, and anti-drug antibodies were characterized.

RESULTS

Two inclacumab-related treatment-emergent adverse events were reported in 1 participant; no dose-limiting toxicities were observed. Plasma PK parameters were generally dose-proportional, with a terminal half-life of 13 to 17 days. Mean TRAP-activated PLA formation decreased within 3 h from the start of infusion, and inhibition was sustained for ~ 23 weeks. Mean P-selectin inhibition > 90% was observed up to 12 weeks post-dose. The mean ratio of free to total soluble P-selectin decreased rapidly from pre-dose to end of infusion, then increased gradually to 78% of the baseline ratio by week 29. Treatment-emergent anti-drug antibodies were observed in 2 of 15 participants (13%), without apparent impact on safety, PK, or PD.

CONCLUSIONS

Inclacumab was well tolerated, with PK as expected for a monoclonal antibody against a membrane-bound target and a long duration of PD effects after both single IV doses, supporting a prolonged dosing interval.

TRIAL REGISTRATION

ACTRN12620001156976; registered November 4, 2020.

Managing the Cerebrovascular Complications of Sickle Cell Disease: Current Perspectives

The importance of protecting brain function for people with sickle cell disease (SCD) cannot be overstated. SCD is associated with multiple cerebrovascular complications that threaten neurocognitive function and life. Without screening and preventive management, 11% of children at 24% of adults with SCD have ischemic or hemorrhagic strokes. Stroke screening in children with SCD is well-established using transcranial Doppler ultrasound (TCD). TCD velocities above 200 cm/s significantly increase the risk of stroke, which can be prevented using chronic red blood cell (RBC) transfusion. RBC transfusion is also the cornerstone of acute stroke management and secondary stroke prevention. Chronic transfusion requires long-term management of complications like iron overload. Hydroxyurea can replace chronic transfusions for primary stroke prevention in a select group of patients or in populations where chronic transfusions are not feasible. Silent cerebral infarction (SCI) is even more common than stroke, affecting 39% of children and more than 50% of adults with SCD; management of SCI is individualized and includes careful neurocognitive evaluation. Hematopoietic stem cell transplant prevents cerebrovascular complications, despite the short- and long-term risks. Newer disease-modifying agents like voxelotor and crizanlizumab, as well as gene therapy, may treat cerebrovascular complications, but these approaches are investigational.

Molecular Mechanisms of Hepatic Dysfunction in Sickle Cell Disease: Lessons From The Townes Mouse Model

Sickle cell disease (SCD) is an autosomal-recessive-genetic disorder that affects ~100,000 Americans and millions of people worldwide. Erythrocyte sickling, vaso-occlusion, sterile inflammation and hemolysis are the major pathophysiological pathways leading to liver injury in SCD. Although hepatic dysfunction affects up to 10-40% of SCD patients, therapeutic approaches to prevent liver injury in SCD are not known, and the molecular mechanisms promoting progressive liver injury in SCD remain poorly understood. Animal models have been beneficial in bridging the gap between preclinical and translational research in SCD. Recent advances in methodology have allowed the development of several humanized mouse models to address various aspects of SCD related liver diseases. This review provides an overview of current knowledge of the molecular mechanisms and potential therapeutic options of SCD associated liver dysfunction using the Townes mouse model.

A critical evaluation of crizanlizumab for the treatment of sickle cell disease

INTRODUCTION

P-selectin is a key adhesion molecule in the pathogenesis of sickle cell disease, including acute painful event(s). Many of the mediators activated in prototypical pain crisis are also involved in other complications seen in this population. Crizanlizumab is a monoclonal antibody approved in the US in 2019 for patients of all genotypes of sickle cell disease. By blocking P-selectin, it effectively prevents acute painful event(s) and has a manageable safety profile.

AREAS COVERED

In this review, we provide an overview of the (i) biology of P-selectin in sickle cell disease, (ii) various agents inhibiting P-selectin, (iii) pharmacology of crizanlizumab, (iv) preclinical and clinical data on crizanlizumab, and (v) its potential for other indications, ongoing studies, regulatory status, and cost issues. Further, we describe its position among other approved agents in sickle cell disease and project future directions as well.

EXPERT OPINION

Crizanlizumab holds great promise in modulating the natural history of sickle cell disease and may have pleotropic effects. Studies are ongoing to define its role in preventing other sickle cell-related complications, non-sickle cell inflammatory states, and thrombotic disorders.

Plasma microparticles of intubated COVID-19 patients cause endothelial cell death, neutrophil adhesion and netosis, in a phosphatidylserine-dependent manner

COVID-19 urges scientists to better describe its pathophysiology to find new therapeutic approaches. While risk factors such as ageing, obesity and diabetes mellitus suggest a central role of endothelial cells (ECs), autopsies revealed clots in the pulmonary microvasculature, which are rich in neutrophils and DNA traps produced by these cells and called NETs. Moreover, submicron extracellular vesicles called microparticles (MPs), are described in several diseases as involved in pro-inflammatory pathways. Therefore, we analyzed 3 patient groups: one for which intubation was not necessary, an intubated group, and the last one after extubating. In the most severe group, the intubated group, platelet-derived MPs and endothelial cell-derived MPs exhibited increased concentration and size, when compared to uninfected controls. MPs of intubated COVID-19 patients triggered ECs death and overexpression of two adhesion molecules: P-selectin and VCAM-1. Strikingly, neutrophils adhesion and NET production were increased following incubation with these ECs. Importantly, we also showed that preincubation of these COVID-19 MPs with the phosphatidylserine capping endogenous protein annexin A5, abolished cytotoxicity, P-selectin and VCAM-1 induction, all like increases in neutrophil adhesion and NET release. Altogether our results unveil that MPs are a key actor in COVID-19 pathophysiology and point towards a potential therapeutic: annexin A5.

P-selectin deficiency promotes liver senescence in sickle cell disease mice

Sickle cell disease (SCD) is caused by a homozygous mutation in the β-globin gene, which leads to erythrocyte sickling, vasoocclusion, and intense hemolysis. P-selectin inhibition has been shown to prevent vasoocclusive events in patients with SCD; however, the chronic effect of P-selectin inhibition in SCD remains to be determined. Here, we used quantitative liver intravital microscopy in our recently generated P-selectin-deficient SCD mice to show that chronic P-selectin deficiency attenuates liver ischemia but fails to prevent hepatobiliary injury. Remarkably, we find that this failure in resolution of hepatobiliary injury in P-selectin-deficient SCD mice is associated with the increase in cellular senescence and reduced epithelial cell proliferation in the liver. These findings highlight the importance of investigating the long-term effects of chronic P-selectin inhibition therapy on liver pathophysiology in patients with SCD.

P-selectin-deficient mice to study pathophysiology of sickle cell disease

P-selectin–deficient SCD mice are protected from lung vaso-occlusion. P-selectin–deficient SCD mice will be useful in assessing the benefits of anti–P-selectin therapy in diverse complications of SCD.

Sickle cell vaso-occlusion: The dialectic between red cells and white cells

The pathophysiology of sickle cell anemia, a hereditary hemoglobinopathy, has fascinated clinicians and scientists alike since its description over 100 years ago. A single gene mutation in the HBB gene results in the production of abnormal hemoglobin (Hb) S, whose polymerization when deoxygenated alters the physiochemical properties of red blood cells, in turn triggering pan-cellular activation and pathological mechanisms that include hemolysis, vaso-occlusion, and ischemia-reperfusion to result in the varied and severe complications of the disease. Now widely regarded as an inflammatory disease, in recent years attention has included the role of leukocytes in vaso-occlusive processes in view of the part that these cells play in innate immune processes, their inherent ability to adhere to the endothelium when activated, and their sheer physical and potentially obstructive size. Here, we consider the role of sickle red blood cell populations in elucidating the importance of adhesion vis-a-vis polymerization in vaso-occlusion, review the direct adhesion of sickle red cells to the endothelium in vaso-occlusive processes, and discuss how red cell- and leukocyte-centered mechanisms are not mutually exclusive. Given the initial clinical success of crizanlizumab, a specific anti-P selectin therapy, we suggest that it is appropriate to take a holistic approach to understanding and exploring the complexity of vaso-occlusive mechanisms and the adhesive roles of the varied cell types, including endothelial cells, platelets, leukocytes, and red blood cells.

P-Selectin Blockade in the Treatment of Painful Vaso-Occlusive Crises in Sickle Cell Disease: A Spotlight on Crizanlizumab

Microvascular vaso-occlusion driven pain crisis is the hallmark of sickle cell disease with profound morbidity and increased mortality. Selectins, most notably P-selectins have an integral role in this phenomenon. P-selection was first identified in 1989. In 2019, after 3 decades of basic, translational, and clinical work with this pathway, the US Food and Drug Administration approved a P-selectin antibody, crizanlizumab to reduce frequency of pain crisis in patients more than 16 years with sickle cell disease. We review the fundamentals of P-selectin pathobiology, P-selectin blocking agents, clinical data with the use of crizanlizumab and prospects of this novel class of drugs in the context of other treatments for painful vaso-occlusive episodes.

Effects and Side Effects of Platelet Transfusion

Aside from their canonical role in hemostasis, it is increasingly recognized that platelets have inflammatory functions and can regulate both adaptive and innate immune responses. The main topic this review aims to cover is the proinflammatory effects and side effects of platelet transfusion. Platelets prepared for transfusion are subject to stress injury upon collection, preparation, and storage. With these types of stress, they undergo morphologic, metabolic, and functional modulations which are likely to induce platelet activation and the release of biological response modifiers (BRMs). As a consequence, platelet concentrates (PCs) accumulate BRMs during processing and storage, and these BRMs are ultimately transfused alongside platelets. It has been shown that BRMs present in PCs can induce immune responses and posttransfusion reactions in the transfusion recipient. Several recent reports within the transfusion literature have investigated the concept of platelets as immune cells. Nevertheless, current and future investigations will face the challenge of encompassing the immunological role of platelets in the scope of transfusion.

Plasma microparticles of sickle patients during crisis or taking hydroxyurea modify endothelium inflammatory properties

Microparticles (MPs) are submicron extracellular vesicles exposing phosphatidylserine (PS), detected at high concentration in the circulation of sickle cell anemia (SS) patients. Several groups studied the biological effects of MPs generated ex vivo. Here, we analyzed for the first time the impact of circulating MPs on endothelial cells (ECs) from 60 sickle cell disease (SCD) patients. MPs were collected from SCD patients and compared with MPs isolated from healthy individuals (AA). Other plasma MPs were purified from SS patients before and 2 years after the onset of hydroxyurea (HU) treatment or during a vaso-occlusive crisis and at steady-state. Compared with AA MPs, SS MPs increased EC ICAM-1 messenger RNA and protein levels, as well as neutrophil adhesion. We showed that ICAM-1 overexpression was primarily caused by MPs derived from erythrocytes, rather than from platelets, and that it was abolished by MP PS capping using annexin V. MPs from SS patients treated with HU were less efficient to induce a proinflammatory phenotype in ECs compared with MPs collected before therapy. In contrast, MPs released during crisis increased ICAM-1 and neutrophil adhesion levels, in a PS-dependent manner, compared with MPs collected at steady-state. Furthermore, neutrophil adhesion was abolished by a blocking anti-ICAM-1 antibody. Our study provides evidence that MPs play a key role in SCD pathophysiology by triggering a proinflammatory phenotype of ECs. We also uncover a new mode of action for HU and identify potential therapeutics: annexin V and anti-ICAM-1 antibodies.

The Evolving Pharmacotherapeutic Landscape for the Treatment of Sickle Cell Disease

Sickle cell disease (SCD) is an extremely heterogeneous disease that has been associated with global morbidity and early mortality. More effective and inexpensive therapies are needed. During the last five years, the landscape of the pharmacotherapy of SCD has changed dramatically. Currently, 54 drugs have been used or under consideration to use for the treatment of SCD. These fall into 3 categories: the first category includes the four drugs (Hydroxyurea, L-Glutamine, Crizanlizumab tmca and Voxelotor) that have been approved by the United States Food and Drug Administration (FDA) based on successful clinical trials. The second category includes 22 drugs that failed, discontinued or terminated for now and the third category includes 28 drugs that are actively being considered for the treatment of SCD. Crizanlizumab and Voxelotor are included in the first and third categories because they have been used in more than one trial. New therapies targeting multiple pathways in the complex pathophysiology of SCD have been achieved or are under continued investigation. The emerging trend seems to be the use of multimodal drugs (i.e. drugs that have different mechanisms of action) to treat SCD similar to the use of multiple chemotherapeutic agents to treat cancer.

Effects of Yak skin gelatin on platelet activation

Studies have shown that gelatin is not only a good hemostatic material, but also a food additive with potentially broad use. Yak skin gelatin is a new gelatin resource, but its oral coagulant effects have not been studied. Given the central role of platelets in hemostasis, in this study we examined the pharmacodynamical differences between different molecular Yak skin gelatins on platelet activation. The hemostatic effects of Yak skin gelatins with different molecular weight distributions were evaluated for bleeding time (BT), clotting time (CT), and platelet activity by measuring the contents of P-selectin, platelet membrane glycoprotein Ia/IIa (GP Ia/IIa), platelet membrane glycoprotein IIb/IIIa (GP IIb/IIIa), and platelet membrane glycoprotein IV (GP IV). Intragastric administration of Yak skin gelatin resulted in a significant reduction in CT and BT, and an increase in the contents of P-selectin, GP Ia/IIa, GP IIb/IIIa, and GP IV in all groups in comparison with the control group. The strongest activation of platelets by Yak skin gelatin was observed with size between 0.1 μm and 0.22 μm, and activation may have been in response to improving GP IIb/IIIa and GP IV levels. When measuring the levels of an established indicator of platelet activation, platelet activation-dependent granule membrane protein (CD62P), its promotion was observed for all molecular weight ranges of Yak skin gelatins. In brief, Yak skin gelatin has hemostatic effects, and Yak skin gelatin fractions between 0.1 μm and 0.22 μm are the primary effectors of hemostasis via promoting platelet membrane glycoprotein activities and strengthening platelet function.

Emerging disease-modifying therapies for sickle cell disease

Sickle cell disease afflicts millions of people worldwide and approximately 100,000 Americans. Complications are myriad and arise as a result of complex pathological pathways ‘downstream’ to a point mutation in DNA, and include red blood cell membrane damage, inflammation, chronic hemolytic anemia with episodic vaso-occlusion, ischemia and pain, and ultimately risk of cumulative organ damage with reduced lifespan of affected individuals. The National Heart, Lung, and Blood Institute’s 2014 evidence-based guideline for sickle cell disease management states that additional research is needed before investigational curative therapies will be widely available to most patients with sickle cell disease. To date, sickle cell disease has been cured by hematopoietic stem cell transplantation in approximately 1,000 people, most of whom were children, and significantly ameliorated by gene therapy in a handful of subjects who have only limited follow-up thus far. During a timespan in which over 20 agents were approved for the treatment of cystic fibrosis by the Food and Drug Administration, similar approval was granted for only two drugs for sickle cell disease (hydroxyurea and L-glutamine) despite the higher prevalence of sickle cell disease. This trajectory appears to be changing, as the lack of multimodal agent therapy in sickle cell disease has spurred engagement among many in academia and industry who, in the last decade, have developed new drugs poised to prevent complications and alleviate suffering. Identified therapeutic strategies include fetal hemoglobin induction, inhibition of intracellular HbS polymerization, inhibition of oxidant stress and inflammation, and perturbation of the activation of the endothelium and other blood components (e.g. platelets, white blood cells, coagulation proteins) involved in the pathophysiology of sickle cell disease. In this article, we present a crash-course review of disease-modifying approaches (minus hematopoietic stem cell transplant and gene therapy) for patients with sickle cell disease currently, or recently, tested in clinical trials in the era following approval of hydroxyurea.

Mast Cells Induce Blood Brain Barrier Damage in SCD by Causing Endoplasmic Reticulum Stress in the Endothelium

Endothelial dysfunction underlies the pathobiology of cerebrovascular disease. Mast cells are located in close proximity to the vasculature, and vasoactive mediators released upon their activation can promote endothelial activation leading to blood brain barrier (BBB) dysfunction. We examined the mechanism of mast cell-induced endothelial activation via endoplasmic reticulum (ER) stress mediated P-selectin expression in a transgenic mouse model of sickle cell disease (SCD), which shows BBB dysfunction. We used mouse brain endothelial cells (mBECs) and mast cells-derived from skin of control and sickle mice to examine the mechanisms involved. Compared to control mouse mast cell conditioned medium (MCCM), mBECs incubated with sickle mouse MCCM showed increased, structural disorganization and swelling of the ER and Golgi, aggregation of ribosomes, ER stress marker proteins, accumulation of galactose-1-phosphate uridyl transferase, mitochondrial dysfunction, reactive oxygen species (ROS) production, P-selectin expression and mBEC permeability. These effects of sickle-MCCM on mBEC were inhibited by Salubrinal, a reducer of ER stress. Histamine levels in the plasma, skin releasate and in mast cells of sickle mice were higher compared to control mice. Compared to control BBB permeability was increased in sickle mice. Treatment of mice with imatinib, Salubrinal, or P-selectin blocking antibody reduced BBB permeability in sickle mice. Mast cells induce endothelial dysfunction via ER stress-mediated P-selectin expression. Mast cell activation contributes to ER stress mediated endothelial P-selectin expression leading to increased endothelial permeability and impairment of BBB. Targeting mast cells and/or ER stress has the potential to ameliorate endothelial dysfunction in SCD and other pathobiologies.

Pentraxin-3 and endothelial dysfunction

Pentraxin 3 (PTX3) is involved in vascular inflammation and endothelial dysfunction through various mechanisms. Until now, most studies confirmed an important link between PTX3 and endothelial dysfunction and identified several pathogenetic pathways. PTX3 modulates inflammatory cells, thus stimulating vascular inflammation. Within endothelial cells, it decreases nitric oxide (NO) synthesis, inhibits cell proliferation and alters their functions. PTX3 blocks the effect of fibroblast growth factor 2 (FGF2) by making a molecular complex with these molecules inactivating them. However, there are substances like the tumor necrosis factor-inducible gene 6 protein (TSG-6) that block the PTX3-FGF2 interaction. Interacting with P-selectin, it promotes vascular inflammatory response and endothelial dysfunction. PTX3 also increases the matrix metalloproteinases synthesis directly or by blocking NO synthesis. From a clinical point of view, PTX3 positively correlates with arterial hypertension, flow mediated dilation and, with intima media thickness. Therefore, the involvement of PTX3 in the pathogenesis and evaluation of endothelial dysfunction is clear, and it may become a biomarker in this direction, but further studies are needed to determine its reliability in this direction. Last but not least, PTX3 could become an effective therapeutic target for preventing this dysfunction, but further research needs to be conducted.

Effect of crizanlizumab on pain crises in subgroups of patients with sickle cell disease: A SUSTAIN study analysis

The cell adhesion molecule P-selectin plays a key role in the pathogenesis of a vaso-occlusive crisis (VOC) in patients with sickle cell disease (SCD). In the double-blind, placebo-controlled phase 2 SUSTAIN study, crizanlizumab (humanized, anti-P-selectin monoclonal antibody) 5 mg/kg significantly lowered the rate of VOC in patients with SCD by 45% vs placebo. In SUSTAIN, patients with SCD were randomized to crizanlizumab 2.5 mg/kg, crizanlizumab 5 mg/kg, or placebo intravenously 14 times over 52 weeks. The primary endpoint was the annual rate of VOC with crizanlizumab vs placebo. This post hoc descriptive analysis evaluated the proportion of patients who did not experience a VOC during the study in the following subgroups: VOCs in the year prior to study entry (2-4/5-10), SCD genotype (HbSS/non-HbSS), and concomitant hydroxyurea use (yes/no). More patients were VOC event-free in the crizanlizumab 5 mg/kg arm than in the placebo arm, including those with more frequent prior VOCs (ie, 5-10; 28.0% vs 4.2%), the HbSS genotype (31.9% vs 17.0%) and/or using concomitant hydroxyurea (33.3% vs 17.5%). Further analyses of secondary endpoints demonstrated that crizanlizumab treatment significantly increased time-to-first VOC vs placebo in these subgroups. The rates of treatment-emergent adverse events were similar between treatment arms across all subgroups. This post hoc analysis of SUSTAIN shows that in patients with a high number of prior VOCs, on concomitant hydroxyurea and/or with the HbSS genotype, crizanlizumab treatment increases the likelihood of patients being VOC event-free and delays time-to-first VOC.

Association between P-selectin levels and left atrial blood stasis in patients with nonvalvular atrial fibrillation

BACKGROUND

P-selectin - a biomarker of platelet and endothelial cell activation is elevated in patients with non-valvular atrial fibrillation (NVAF). However, the association between sP-selectin level and thromboembolic complications in NVAF patients remains controversial. We tested the hypothesis that plasma soluble P-selectin (sPSL) level correlates with the measures of left atrial blood stasis in NVAF.

METHODS

Plasma sPSL concentration was measured using solid-phase ELISA in 103 NVAF patients (age 63 ± 14 years; 26% women) and 48 normal sinus rhythm controls (NSR; age 64 ± 14 years; 41% women) who were not on aspirin. Within the group of NVAF cases, 27 had no spontaneous echocardiographic contrast (SEC) detected by transesophageal echocardiography, 31had mild SEC, 15 moderate, 20 severe, and 10 patients had left atrial appendage thrombus (LAAT).

RESULTS

The median soluble sPSL level was higher in NVAF cases compared to NSR controls [(interquartile range) 26 (20-32) ng/mL vs 22 (15-29) ng/mL, p = 0.0045]. Only NVAF patients with CHA₂DS₂-VASc score ≥ 1 had higher sPSL level compared to NSR controls. Patients with severe SEC had significantly higher sPSL levels [32 (24-38) ng/mL] compared to all other NVAF patients (p = 0.0042) and to NSR controls (p < 0.0001). Also NVAF patients with LAAT had higher sPSL level compared to NSR controls.

CONCLUSIONS

There is a direct correlation between p-selectin level and severe blood stasis in the left atrium. Only NVAF patients with CHA₂DS₂-VASc score ≥ 1 or with LAAT had higher sPSL level compared to NSR controls.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

Characterization of a P-selectin-binding moiety from Bupleurum chinense polysaccharide and its antagonistic effect against P-selectin-mediated function

P-selectin is a promising therapeutic target for acute inflammation-related diseases, and interest has been growing in the search for high-affinity glycoconjugate ligands that can target the initial P-selectin-mediated recruitment of neutrophils to the site of inflammation. In our previous study, we isolated a water-soluble polysaccharide (BCPS) from Bupleurum chinense and showed that it exhibits anti-inflammatory effect by antagonizing P-selectin-mediated adhesion of HL-60 cells to CHO-P cells. In this study, we prepared a P-selectin-based affinity chromatography medium and used it to purify the P-selectin-binding moiety of BCPS. The purified P-selectin-binding moiety of BCPS, designated as BCPS-m, was mainly composed of arabinose, galactose and glucose, and had a relative molecular weight of 3600 Da. The backbone of BCPS-m was composed of 1,5-linked arabinose, 1,4-linked and 1,4,6-linked glucose, and with branched 1-linked glucose or galactose terminal. BCPS-m could disrupt the P-selectin-mediated binding of HL-60 cells to CHO-P cells (CHO cells that stably expressed an exogenous P-selectin). It also blocked the interaction between P-selectin and its physiological ligand PSGL-1 significantly, resulting in much greater reduction (77%) in P-selectin-PSGL-1 binding than that caused by BCPS (35%). The data suggested that BCPS-m could be the key P-selectin-binding moiety of BCPS, and that it may be a better P-selectin antagonist than BCPS.

Nitric oxide pathology and therapeutics in sickle cell disease

Sickle cell disease is caused by a mutant form of hemoglobin that polymerizes under hypoxic conditions which leads to red blood cell (RBC) distortion, calcium-influx mediated RBC dehydration, increased RBC adhesivity, reduced RBC deformability, increased RBC fragility, and hemolysis. These impairments in RBC structure and function result in multifaceted downstream pathology including inflammation, endothelial cell activation, platelet and leukocyte activation and adhesion, and thrombosis, all of which contribute vascular occlusion and substantial morbidity and mortality. Hemoglobin released upon RBC hemolysis scavenges nitric oxide (NO) and generates reactive oxygen species (ROS) and thereby decreases bioavailability of this important signaling molecule. As the endothelium-derived relaxing factor, NO acts as a vasodilator and also decreases platelet, leukocyte, and endothelial cell activation. Thus, low NO bioavailability contributes to pathology in sickle cell disease and its restoration could serve as an effective treatment. Despite its promise, clinical trials based on restoring NO bioavailability have so far been mainly disappointing. However, particular "NO donating" agents such as nitrite, which unlike some other NO donors can improve sickle RBC properties, may yet prove effective.

Potential therapeutic action of nitrite in sickle cell disease

Sickle cell disease is caused by a mutant form of hemoglobin that polymerizes under hypoxic conditions, increasing rigidity, fragility, calcium influx-mediated dehydration, and adhesivity of red blood cells. Increased red cell fragility results in hemolysis, which reduces nitric oxide (NO) bioavailability, and induces platelet activation and inflammation leading to adhesion of circulating blood cells. Nitric Oxide inhibits adhesion and platelet activation. Nitrite has emerged as an attractive therapeutic agent that targets delivery of NO activity to areas of hypoxia through bioactivation by deoxygenated red blood cell hemoglobin. In this study, we demonstrate anti-platelet activity of nitrite at doses achievable through dietary interventions with comparison to similar doses with other NO donating agents. Unlike other NO donating agents, nitrite activity is shown to be potentiated in the presence of red blood cells in hypoxic conditions. We also show that nitrite reduces calcium associated loss of phospholipid asymmetry that is associated with increased red cell adhesion, and that red cell deformability is also improved. We show that nitrite inhibits red cell adhesion in a microfluidic flow-channel assay after endothelial cell activation. In further investigations, we show that leukocyte and platelet adhesion is blunted in nitrite-fed wild type mice compared to control after either lipopolysaccharide- or hemolysis-induced inflammation. Moreover, we demonstrate that nitrite treatment results in a reduction in adhesion of circulating blood cells and reduced red blood cell hemolysis in humanized transgenic sickle cell mice subjected to local hypoxia. These data suggest that nitrite is an effective anti-platelet and anti-adhesion agent that is activated by red blood cells, with enhanced potency under physiological hypoxia and in venous blood that may be useful therapeutically.

Hypoxia-enhanced adhesion of red blood cells in microscale flow

OBJECTIVES

The advancement of microfluidic technology has facilitated the simulation of physiological conditions of the microcirculation, such as oxygen tension, fluid flow, and shear stress in these devices. Here, we present a micro-gas exchanger integrated with microfluidics to study RBC adhesion under hypoxic flow conditions mimicking postcapillary venules.

METHODS

We simulated a range of physiological conditions and explored RBC adhesion to endothelial or subendothelial components (FN or LN). Blood samples were injected into microchannels at normoxic or hypoxic physiological flow conditions. Quantitative evaluation of RBC adhesion was performed on 35 subjects with homozygous SCD.

RESULTS

Significant heterogeneity in RBC adherence response to hypoxia was seen among SCD patients. RBCs from a HEA population showed a significantly greater increase in adhesion compared to RBCs from a HNA population, for both FN and LN.

CONCLUSIONS

The approach presented here enabled the control of oxygen tension in blood during microscale flow and the quantification of RBC adhesion in a cost-efficient and patient-specific manner. We identified a unique patient population in which RBCs showed enhanced adhesion in hypoxia in vitro. Clinical correlates suggest a more severe clinical phenotype in this subgroup.

Endothelial Alterations in Systemic Lupus Erythematosus and Rheumatoid Arthritis: Potential Effect of Monocyte Interaction

Patients with systemic autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are prone to develop atherosclerosis and cardiovascular diseases five times more often than the general population; this increase in frequency could be partially explained by an increase in the macrovasculature endothelial damage. In these autoimmune diseases, a microvascular endothelial injury has also been reported in different organs and tissues, especially in sites where ultrafiltration processes occur. Different components that are characteristic to the immunopathology of RA and SLE could be involved in the endothelial cell activation, permeability increase, functional alteration, and vascular injury. Circulating immune complexes (IC) detected in SLE and RA have been proposed to participate in the endothelial injury. In the vascular environment, IC can generate different responses that could be mediated by monocytes, because these cells have patrolling and monitoring functions on the endothelium. However, with certain stimuli such as TLR ligands, the monocytes are retained in the lumen, releasing proinflammatory mediators that participate in the endothelial damage. This paper aims to review some aspects about the endothelial activation and dysfunction in the context of SLE and RA, as well as the potential role that monocytes apparently play in this process.

Recent Advances in Aptamers Targeting Immune System

The immune system plays important role in protecting the organism by recognizing non-self molecules from pathogen such as bacteria, parasitic worms, and viruses. When the balance of the host defense system is disturbed, immunodeficiency, autoimmunity, and inflammation occur. Nucleic acid aptamers are short single-stranded DNA (ssDNA) or RNA ligands that interact with complementary molecules with high specificity and affinity. Aptamers that target the molecules involved in immune system to modulate their function have great potential to be explored as new diagnostic and therapeutic agents for immune disorders. This review summarizes recent advances in the development of aptamers targeting immune system. The selection of aptamers with superior chemical and biological characteristics will facilitate their application in the diagnosis and treatment of immune disorders.

Intravascular hemolysis and the pathophysiology of sickle cell disease

Hemolysis is a fundamental feature of sickle cell anemia that contributes to its pathophysiology and phenotypic variability. Decompartmentalized hemoglobin, arginase 1, asymmetric dimethylarginine, and adenine nucleotides are all products of hemolysis that promote vasomotor dysfunction, proliferative vasculopathy, and a multitude of clinical complications of pulmonary and systemic vasculopathy, including pulmonary hypertension, leg ulcers, priapism, chronic kidney disease, and large-artery ischemic stroke. Nitric oxide (NO) is inactivated by cell-free hemoglobin in a dioxygenation reaction that also oxidizes hemoglobin to methemoglobin, a non-oxygen-binding form of hemoglobin that readily loses heme. Circulating hemoglobin and heme represent erythrocytic danger-associated molecular pattern (eDAMP) molecules, which activate the innate immune system and endothelium to an inflammatory, proadhesive state that promotes sickle vaso-occlusion and acute lung injury in murine models of sickle cell disease. Intravascular hemolysis can impair NO bioavailability and cause oxidative stress, altering redox balance and amplifying physiological processes that govern blood flow, hemostasis, inflammation, and angiogenesis. These pathological responses promote regional vasoconstriction and subsequent blood vessel remodeling. Thus, intravascular hemolysis represents an intrinsic mechanism for human vascular disease that manifests clinical complications in sickle cell disease and other chronic hereditary or acquired hemolytic anemias.

[Effect of ulinastatin on serum levels of tumor necrosis factor-α, P-selectin, and thrombin-antithrombin complex in young rats with sepsis]

OBJECTIVE

To investigate the effect of ulinastatin (UTI) for early drug intervention on the serum levels of tumor necrosis factor-α (TNF-α), P-selectin, and thrombin-antithrombin complex (TAT) in young rats with sepsis.

METHODS

A total of 120 male rats aged 4 weeks were randomly divided into normal control group, sham-operation group, sepsis group, low-dose UTI group (50 000 U/kg), and high-dose UTI group (200 000 U/kg), with 24 rats in each group. Modified cecal ligation and puncture was performed to establish a rat model of sepsis, and the rats in the low- and high-dose UTI groups were given caudal vein injection of UTI after model establishment. ELISA was used to measure the serum levels of TNF-α, P-selectin, and TAT at 6, 12, and 24 hours after model establishment.

RESULTS

The sepsis group had significant increases in the serum levels of TNF-α, P-selectin, and TAT at 6 hours, and the serum levels of TNF-α and TAT continued to increase by 24 hours (P<0.05); P-selectin reached the peak at 12 hours and decreased slightly at 24 hours (P<0.05). The UTI groups had similar change patterns in the levels of P-selectin and TAT as the sepsis group. The UTI groups had significant increases in the level of TNF-α at 6 hours, but gradually decreased over time. The changes in serum levels of TNF-α, P-selectin, and TAT in the UTI groups were significantly smaller than in the sepsis group (P<0.05). The high-dose UTI group had significantly smaller changes in serum levels of TNF-α, P-selectin, and TAT than the low-dose UTI group (P<0.05).

CONCLUSIONS

Early intervention with UTI can significantly improve coagulation function and inhibit the production of TNF-α, P-selectin, and TAT in young rats with sepsis. High-dose UTI has a significantly greater effect than low-dose UTI.

Emerging point-of-care technologies for sickle cell disease screening and monitoring

INTRODUCTION

Sickle Cell Disease (SCD) affects 100,000 Americans and more than 14 million people globally, mostly in economically disadvantaged populations, and requires early diagnosis after birth and constant monitoring throughout the life-span of the patient. Areas covered: Early diagnosis of SCD still remains a challenge in preventing childhood mortality in the developing world due to requirements of skilled personnel and high-cost of currently available modalities. On the other hand, SCD monitoring presents insurmountable challenges due to heterogeneities among patient populations, as well as in the same individual longitudinally. Here, we describe emerging point-of-care micro/nano platform technologies for SCD screening and monitoring, and critically discuss current state of the art, potential challenges associated with these technologies, and future directions. Expert commentary: Recently developed microtechnologies offer simple, rapid, and affordable screening of SCD and have the potential to facilitate universal screening in resource-limited settings and developing countries. On the other hand, monitoring of SCD is more complicated compared to diagnosis and requires comprehensive validation of efficacy. Early use of novel microdevices for patient monitoring might come in especially handy in new clinical trial designs of emerging therapies.

Aqueous extract from Ipomoea asarifolia (Convolvulaceae) leaves and its phenolic compounds have anti-inflammatory activity in murine models of edema, peritonitis and air-pouch inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Ipomoea asarifolia (Desr.) Roem. and Schult.(Convolvulaceae), popularly known as salsa or salsa-brava, is a plant of which the decoction of leaves is used in folk medicine to treat various inflammatory disorders such of dermatitis, scabies, symptoms of syphilis, skin ulcers and external wounds. However, little is known about possible compounds and mechanisms of action of the plant to support the activities reported by popular use.

AIM OF THE STUDY

The study aimed to identify bioactive molecules present in the crude extract of I. asarifolia leaves and investigate the anti-inflammatory potential of this extract in different experimental in vivo models to improve the understanding on that activity.

MATERIAL AND METHODS

Aqueous extract of I. asarifolia leaves was prepared by decoction (1:10 m/v) and its chromatographic profile was obtained by high performance liquid chromatography coupled with diode array detector (HPLC-DAD) and liquid chromatography diode array detector coupled with mass spectrometry (LC-DAD-MS). The potential anti-inflammatory activity of the extract was assessed using the following in vivo models: xylene-induced ear edema (20, 30 and 40mg/kg), evaluating the degree of edema formation; carrageenan-induced peritonitis (10, 20 and 30mg/kg), evaluating leukocyte migration and cytokine levels (IL-1β, IL-6, IL-12 and TNF-α) at 4h; zymosan-induced air pouch inflammation (20, 30 and 40mg/kg), evaluating the kinetics of leukocyte migration by total and differential counts at 6, 24 and 48h. The same tests were conducted using pure compounds identified in the aqueous extract from I. asarifolia leaves in different doses for each experimental model.

RESULTS

The compounds identified in the aqueous extract of I. asarifolia leaves by HPLC-DAD and LC-DAD-MS were rutin, chlorogenic acid and caffeic acid. The extract significantly reduced ear edema induced by xylene (81%, 85% and 86% for doses of 20, 30 and 40mg/kg, respectively, p<0.001), as well as cell migration in experimental models of peritonitis (70%, 78% and 83% for doses of 10, 20 and 30mg/kg, respectively, p<0.001) and air pouch inflammation (58%, 67% and 53% for doses of 20, 30 and 40mg/kg, respectively, p<0.001). In addition, the extract demonstrated the ability to significantly inhibit the production of cytokines IL-1β, IL-6, IL-12 and TNF-α (p<0.001). The secondary metabolites tested (rutin, chlorogenic acid and caffeic acid) also showed the ability to significantly (p<0.001) decrease the parameters analyzed above.

CONCLUSION

This is the first study to identify and confirm these phenolic compounds in I. asarifolia leaves extract and to suggest that these compounds contribute to the anti-inflammatory activity in vivo, as reported by ethnomedicinal use of this plant. Through the different experimental models performed, we can conclude that the results obtained with the aqueous extract from I. asarifolia leaves support its popular use for the treatment of inflammatory disorders.

Markers of endothelial dysfunction and leucocyte activation in Saudi and non-Saudi haplotypes of sickle cell disease

Sickle cell disease (SCD) is an autosomal recessive inherited hemoglobinopathy, characterized by chronic hemolysis and recurrent vaso-occlusive crisis (VOC). This study investigates changes in leucocyte subsets and the relationship between cell adhesion molecule expression and disease manifestations in patients during steady state and acute VOC. We compared soluble E-selectin and P-selectin levels in 84 SCD patients, in steady state and during VOC to 84 healthy controls. Using immunophenotyping, we also compared lymphocyte subsets in these three groups. Further, we compared E-selectin and P-selectin levels in patients of Saudi ethnicity to non-Saudi patients, in all three groups. Lymphocyte subsets showed high percentages of total T lymphocytes, T helper and suppressor lymphocytes, B lymphocytes as well as NK cells in patients with SCD during steady state, while B lymphocytes and NK cells were significantly higher during acute VOC crisis. High levels of both soluble E-selectin (sE-selectin) and soluble P-selectin (sP-selectin) markers were demonstrated in the serum of patients with SCD during both steady state and acute VOC. Levels of selectins were significantly higher in acute VOC. The immunophenotypic expression of L-selectin, on leucocytes, was high in SCD both during steady state and during acute VOC in comparison to normal control subjects. There was no significant difference in all three study groups between Saudi and non-Saudi patients. These findings suggest that patients with SCD have increased expression of adhesion molecules: E-selectin and P-selectin, which play an important role in the pathogenesis of VOC. Despite the distinct phenotype of Saudi patients with SCD, there was no significant difference in levels of soluble E-selectin and soluble P-selectin between Saudi and non-Saudi patients in all three groups. While sickle cell disease is a well-recognized state of chronic inflammation, the role of specific adhesion molecules is steadily unraveling. Studies are underway to investigate the potential role of selectin antagonists, for prevention and reversal of acute vascular occlusions in SCD patients.

Sickle cell disease biochip: a functional red blood cell adhesion assay for monitoring sickle cell disease

Sickle cell disease (SCD) afflicts millions of people worldwide and is associated with considerable morbidity and mortality. Chronic and acute vaso-occlusion are the clinical hallmarks of SCD and can result in pain crisis, widespread organ damage, and early movtality. Even though the molecular underpinnings of SCD were identified more than 60 years ago, there are no molecular or biophysical markers of disease severity that are feasibly measured in the clinic. Abnormal cellular adhesion to vascular endothelium is at the root of vaso-occlusion. However, cellular adhesion is not currently evaluated clinically. Here, we present a clinically applicable microfluidic device (SCD biochip) that allows serial quantitative evaluation of red blood cell (RBC) adhesion to endothelium-associated protein-immobilized microchannels, in a closed and preprocessing-free system. With the SCD biochip, we have analyzed blood samples from more than 100 subjects and have shown associations between the measured RBC adhesion to endothelium-associated proteins (fibronectin and laminin) and individual RBC characteristics, including hemoglobin content, fetal hemoglobin concentration, plasma lactate dehydrogenase level, and reticulocyte count. The SCD biochip is a functional adhesion assay, reflecting quantitative evaluation of RBC adhesion, which could be used at baseline, during crises, relative to various long-term complications, and before and after therapeutic interventions.

Extracellular microvesicle microRNAs in children with sickle cell anaemia with divergent clinical phenotypes

Sickle cell anaemia (SCA) is the most frequent genetic haemoglobinopathy, which exhibits a highly variable clinical course characterized by hyper-coagulable and pro-inflammatory states, as well as endothelial dysfunction. Extracellular microvesicles are released into biological fluids and play a role in modifying the functional phenotype of target cells. We hypothesized that potential differences in plasma-derived extracellular microvesicles (EV) function and cargo from SCA patients may underlie divergent clinical trajectories. Plasma EV from SCA patients with mild, intermediate and severe clinical disease course were isolated, and primary endothelial cell cultures were exposed. Endothelial cell activation, monocyte adhesion, barrier disruption and exosome cargo (microRNA microarrays) were assessed. EV disrupted the endothelial barrier and induced expression of adhesion molecules and monocyte adhesion in a SCA severity-dependent manner compared to healthy children. Microarray approaches identified a restricted signature of exosomal microRNAs that readily distinguished severe from mild SCA, as well as from healthy children. The microRNA candidates were further validated using quantitative real time polymerase chain reaction assays, and revealed putative gene targets. Circulating exosomal microRNAs may play important roles in predicting the clinical course of SCA, and in delineation of individually tailored, mechanistically-based clinical treatment approaches of SCA patients in the near future.

Adhesion Molecules: Master Controllers of the Circulatory System

This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

New radiotracers for imaging of vascular targets in angiogenesis-related diseases

Tremendous advances over the last several decades in positron emission tomography (PET) and single photon emission computed tomography (SPECT) allow for targeted imaging of molecular and cellular events in the living systems. Angiogenesis, a multistep process regulated by the network of different angiogenic factors, has attracted world-wide interests, due to its pivotal role in the formation and progression of different diseases including cancer, cardiovascular diseases (CVD), and inflammation. In this review article, we will summarize the recent progress in PET or SPECT imaging of a wide variety of vascular targets in three major angiogenesis-related diseases: cancer, cardiovascular diseases, and inflammation. Faster drug development and patient stratification for a specific therapy will become possible with the facilitation of PET or SPECT imaging and it will be critical for the maximum benefit of patients.

Investigational selectin-targeted therapy of sickle cell disease

INTRODUCTION

Under conditions of blood flow, selectins mediate the intercellular adhesion between erythrocytes, leukocytes, platelets and vascular endothelium that contribute to vaso-occlusion and tissue damage in sickle cell disease (SCD). Therefore, selectin antagonists have the potential to ameliorate SCD.

AREAS COVERED

In this review, the author discusses the cellular and molecular basis of vaso-occlusion in SCD, and presents evidence that selectin-mediated cell adhesion has clinical importance in this disorder. The author discusses molecular structure of human selectins and their physiological ligands and highlights clinical trials of selectin-targeted therapy of SCD. Herein, the author also assesses the benefits and limitations of the selectin antagonists that are currently under evaluation for SCD, and offers suggestions for the future.

EXPERT OPINION

In Phase I and II clinical trials, rivipansel and heparin demonstrated promising efficacy and safety in SCD. Although selectin blockade could potentially impair immune response, an increased incidence of infection was not reported in SCD patients treated with heparin (n = 127) or rivipansel (n = 111). The efficacy and safety findings from Phase I and II clinical studies are encouraging the commencement of Phase III studies to further evaluate selectin-targeted therapy in SCD.