Characterization of the novel P-selectin inhibitor PSI-697 [2-(4-chlorobenzyl)-3-hydroxy-7,8,9,10-tetrahydrobenzo[h] quinoline-4-carboxylic acid] in vitro and in rodent models of vascular inflammation and thrombosis

Selectins in Biology and Human Disease: Opportunity in E-selectin Antagonism

Selectins are cell adhesion proteins discovered in the 1980s. As C-type lectins, selectins contain an essential calcium ion in the ligand-binding pocket and recognize the isomeric tetrasaccharides sialyl Lewisx (sLex) and sialyl Lewisa (sLea). Three selectins, E-selectin, P-selectin, and L-selectin, play distinct, complementary roles in inflammation, hematopoiesis, and tumor biology. They have been implicated in the pathology of diverse inflammatory disorders, and several selectin antagonists have been tested clinically. E-selectin plays a unique role in leukocyte activation, making it an attractive target for intervention, for example, in sickle cell disease (SCD). This review summarizes selectin biology and pathology, structure and ligand binding, and selectin antagonists that have reached clinical testing with an emphasis on E-selectin.

Association of the rs3917647 polymorphism of the SELP gene with malnutrition in gastric cancer

BACKGROUND

Malnutrition and cachexia are common syndromes in patients with gastric cancer (GC) and are associated with poor quality of life and poor disease prognosis. However, there is still a lack of molecular factors that can predict malnutrition or cachexia in cancer. Studies have shown that among the potential contributors to the development of cancer cachexia, the level of the inflammatory response to P-selectin is regulated by single nucleotide polymorphisms (SNPs) located in the promoter region of the SELP gene. The aim of this study was to evaluate the association between the single nucleotide polymorphism (SNP)-2028 A/G of the SELP gene and malnutrition in patients receiving chemotherapy for gastric cancer (GC).

METHODS

The study group consisted of 220 GC patients treated with chemotherapy at Jinhua Municipal Central Hospital. DNA was extracted from peripheral leukocytes of whole blood samples using an animal DNA extraction kit. DNA was amplified using a 1.1 × T3 Super PCR mix, and loci corresponding to the peaks were genotyped using SNP1 software.

RESULTS

Patients carrying the A allele had a reduced risk of developing malnutrition compared to patients with the GG genotype (P < 0.001; OR = 3.411; 95% CI = 1.785-6.516). In addition, multivariate analysis indicated that the AA genotype significantly (more than 16-fold) reduced the risk of developing malnutrition (P < 0.001; OR = 0.062; 95% CI = 0.015-0.255).

CONCLUSION

SELP -2028A/G SNP may be a useful marker for assessing the risk of malnutrition in GC patients.

Novel strategies in antithrombotic therapy: targeting thrombosis while preserving hemostasis

Antithrombotic therapy is a delicate balance between the benefits of preventing a thrombotic event and the risks of inducing a major bleed. Traditional approaches have included antiplatelet and anticoagulant medications, require careful dosing and monitoring, and all carry some risk of bleeding. In recent years, several new targets have been identified, both in the platelet and coagulation systems, which may mitigate this bleeding risk. In this review, we briefly describe the current state of antithrombotic therapy, and then present a detailed discussion of the new generation of drugs that are being developed to target more safely existing or newly identified pathways, alongside the strategies to reverse direct oral anticoagulants, showcasing the breadth of approaches. Combined, these exciting advances in antithrombotic therapy bring us closer than we have ever been to the "holy grail" of the field, a treatment that separates the hemostatic and thrombotic systems, preventing clots without any concurrent bleeding risk.

High expression of P-selectin induces neutrophil extracellular traps via the PSGL-1/Syk/Ca2+/PAD4 pathway to exacerbate acute pancreatitis

Background

Excessive neutrophil extracellular traps (NETs) is involved in the progression of acute pancreatitis (AP) but the mechanisms controlling NETs formation in AP are not fully understood. Therefore, our study sought to investigate the mechanism of the highly expressed P-selectin stimulating the formation of NETs in AP.

Methods

NETs formation was detected by flow cytometry, immunofluorescence staining, and cf-DNA and MPO-DNA complexes were measured as biomarkers of NETs formation. Neutrophils treated with P-selectin and pharmacological inhibitors were examined by western blot, immunofluorescence staining and flow cytometry. Mouse model of AP was established by caerulein and the effect of inhibiting P-selectin by PSI-697 on the level of NETs and PAD4 in pancreatic tissue was observed. The severity of AP was evaluated by histopathological score and the detection of serum amylase and lipase.

Results

Patients with AP had elevated levels of NETs and P-selectin compared with healthy volunteers. Stimulation of P-selectin up-regulated the expression of PSGL-1, increased the phosphorylation of Syk, mediated intracellular calcium signal and led to the activation and expression of PAD4, which modulated NETs formation in neutrophils. Pretreament with PSI-697 blunted NETs formation and PAD4 expression in the pancreatic tissue, and ameliorated the severity of AP in mice.

Conclusion

Taken together, these results suggest that P-selectin induces NETs through PSGL-1 and its downstream Syk/Ca2+/PAD4 signaling pathway, and that targeting this pathway might be a promising strategy for the treatment of AP.

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

P- and E- selectin in venous thrombosis and non-venous pathologies

Venous thromboembolism is a very common and costly health problem worldwide. Anticoagulant treatment for VTE is imperfect: all have the potential for significant bleeding, and none prevent the development of post thrombotic syndrome after deep vein thrombosis or chronic thromboembolic pulmonary hypertension after pulmonary embolism. For these reasons, alternate forms of therapy with improved efficacy and decreased bleeding are needed. Selectins are a family (P-selectin, E-selectin, L-selectin) of glycoproteins that facilitate and augment thrombosis, modulating neutrophil, monocyte, and platelet activity. P- and E-selectin have been investigated as potential biomarkers for thrombosis. Inhibition of P-selectin and E-selectin decrease thrombosis and vein wall fibrosis, with no increase in bleeding. Selectin inhibition is a promising avenue of future study as either a stand-alone treatment for VTE or as an adjunct to standard anticoagulation therapies.

Nanoparticles of a New Small-Molecule P-Selectin Inhibitor Attenuate Thrombosis, Inflammation, and Tumor Growth in Two Animal Models

Purpose

To assess whether the newly designed small-molecule oral P-selectin inhibitor 3S-1,2,3,4-tetrahydro-β-carboline-3-methyl aspartyl ester (THCMA) as a nanomedicine enhances antithrombosis, anti-inflammation, and antitumor activity more than the clinical trial drug PSI-697.

Methods

THCMA was designed as an amphiphile containing pharmacophores of PSI-697. Its nanofeatures were explored with TEM, SEM, Tyndall effect, ζ-potential, FT-ICR-MS, and NOESY 2D ¹H NMR. The P-selectin inhibitory effect of THCMA was demonstrated with molecular docking, ultraviolet (UV) spectra, and competitive ELISA. In vivo and in vitro assays — anti-arterial thrombosis, anti–venous thrombosis, anti-inflammation, antitumor growth, anti–platelet aggregation, rat-tail bleeding time, anticoagulation index, soluble P-selectin (sP-selectin) expression, and serum TNFα expression — were performed to explore bioactivity and potential mechanisms. Water solubility of THCMA was measured using UV-absorption spectra.

Results

THCMA self-assembled into nanorings of approximately 100 nm in diameter. Its water solubility was about 1,030-fold that of PSI-697. THCMA exhibited more potent P-selectin inhibitory effect than PSI-697. The oral efficacy of THCMA was 100-fold that of PSI-697 in inhibiting arterial and venous thrombosis and tenfold in inhibiting inflammation. THCMA inhibited thrombosis at a dose that produces no coagulation disorders and no bleeding risk. THCMA exhibited enhanced antitumor activity over PSI-697 without systemic chemotherapy toxicity. THCMA significantly inhibited platelet aggregation in vitro and downregulated the expression levels of serum sP-selectin and TNFα in vivo.

Conclusion

A new small-molecule P-selectin inhibitor, THCMA, has been successfully designed as a nanomedicine with largely enhanced oral efficacy compared to the clinical trial drug PSI-697, and thus might be developed for the oral treatment of arterial thrombosis, venous thrombosis, inflammation, and cancer-associated thrombosis.

Novel antiplatelet targets in the treatment of acute coronary syndromes

Acute coronary syndromes (ACS) are a global cause of mortality and morbidity that affect millions of lives worldwide. Following atherosclerotic plaque rupture, platelet activation and aggregation are the two major elements that initiate thrombus formation inside a coronary artery, which can obstruct blood flow and cause myocardial ischemia; ergo, antiplatelet therapy forms a major part of the treatment strategy for ACS. Patients with ACS routinely receive dual antiplatelet therapy (DAPT), which consists of aspirin and a platelet P2Y₁₂ inhibitor to both treat and prevent atherothrombosis. Use of platelet glycoprotein (GP) IIb/IIIa inhibitors is now limited due to the risk of severe bleeding and thrombocytopenia. Thus, administration of GPIIb/IIIa inhibitors is generally restricted to bail out thrombotic events associated with PCI. Furthermore, current antiplatelet medications mainly rely on thromboxane A₂ and P2Y₁₂ inhibition, which have broad-acting effects on platelets and are known to cause bleeding, which especially limits the long-term use of these agents. In addition, not all ACS patients treated with current antiplatelet treatments are protected from recurrence of arterial thrombosis, since many platelet mechanisms and activation pathways remain uninhibited by current antiplatelet therapy. Pharmacological antagonism of novel targets involved in platelet function could shape future antiplatelet therapies that could ultimately lead to more effective or safer therapeutic approaches. In this article, we focus on inhibitors of promising targets that have not yet been introduced into clinical practice, including inhibitors of GPVI, protease-activated receptor (PAR)-4, GPIb, 5-hydroxytryptamine receptor subtype 2A (5-HT_2A), protein disulfide isomerase, P-selectin and phosphoinositide 3-kinase β.

Microparticles from aged packed red blood cell units stimulate pulmonary microthrombus formation via P-selectin

INTRODUCTION

During storage, packed red blood cells undergo a series of physical, metabolic, and chemical changes collectively known as the red blood cell storage lesion. One key component of the red blood cell storage lesion is the accumulation of microparticles, which are submicron vesicles shed from erythrocytes as part of the aging process. Previous studies from our laboratory indicate that transfusion of these microparticles leads to lung injury, but the mechanism underlying this process is unknown. In the present study, we hypothesized that microparticles from aged packed red blood cell units induce pulmonary thrombosis.

MATERIALS AND METHODS

Leukoreduced, platelet-depleted, murine packed red blood cells (pRBCS) were prepared then stored for up to 14 days. Microparticles were isolated from stored units via high-speed centrifugation. Mice were transfused with microparticles. The presence of pulmonary microthrombi was determined with light microscopy, Martius Scarlet Blue, and thrombocyte stains. In additional studies microparticles were labelled with CFSE prior to injection. Murine lung endothelial cells were cultured and P-selectin concentrations determined by ELISA. In subsequent studies, P-selectin was inhibited by PSI-697 injection prior to transfusion.

RESULTS

We observed an increase in microthrombi formation in lung vasculature in mice receiving microparticles from stored packed red blood cell units as compared with controls. These microthrombi contained platelets, fibrin, and microparticles. Treatment of cultured lung endothelial cells with microparticles led to increased P-selectin in the media. Treatment of mice with a P-selectin inhibitor prior to microparticle infusion decreased microthrombi formation.

CONCLUSIONS

These data suggest that microparticles isolated from aged packed red blood cell units promote the development of pulmonary microthrombi in a murine model of transfusion. This pro-thrombotic event appears to be mediated by P-selectin.

The inhibitory role of recombinant P-selectin glycoprotein ligand immunoglobulin G on portal vein thrombosis based on a novel rat model

The current study aimed to reveal a novel method for constructing a portal vein thrombosis (PVT) model in rats and to evaluate the inhibitory role of recombinant P-selectin glycoprotein ligand immunoglobulin G (rPSGL-Ig) on the formation of PVT. The PVT model was constructed in rats through intermittent portal vein obstruction (IPVO) combined with endangium destruction. A total of 4 mg/kg rPSGL-Ig was intraperitoneally pre-injected into rats 1 h prior to model construction. Changes in the thrombus size and vessel diameter were observed by B-scan ultrasonography. Histopathological changes in the portal vein, central hepatic vein and vasa intestini tenuis were observed using hematoxylin and eosin staining. Additionally, histopathological changes in the portal vein were observed by transmission electron microscopy. A total of 8 mg/kg rPSGL-Ig or 2×104 U/kg urokinase were used to compare the thrombolytic effects and thrombus sizes. The PVT model was successfully constructed in rats, and exhibited a significantly greater thrombus size and vessel diameter compared with the control group (P<0.05). Intervention with rPSGL-Ig significantly inhibited the formation of PVT, and resulted in a significantly lower thrombus size and vessel diameter compared with the model group (P<0.05). Additionally, histopathological changes in the portal vein, central hepatic vein and vasa intestini tenuis in PVT rats were considerably reversed following the intervention with rPSGL-Ig. rPSGL-Ig demonstrated a lower thrombolytic effect compared with that of URO. IPVO combined with endangium destruction effectively constructed a PVT model in rats. rPSGL-Ig effectively prevented PVT in rats. rPSGL-Ig may be used in future studies for the treatment of patients with PVT.

Mutant Kras-induced upregulation of CD24 enhances prostate cancer stemness and bone metastasis

Prostate cancer (PCA), one of the most common malignant tumors in men, is the second leading cause of cancer deaths in males worldwide. We report here that PCA models harboring conditional LSL/KrasG12D or BRAFF-V600E allele with prostate-specific abrogated p53 function recapitulate human PCA precursor lesions, histopathology, and clinical behaviors. We found that the development of reprogrammed EMT-like phenotypes and skeleton metastatic behavior requires concurrent activated Kras and p53 depletion in PCA. Microarray analyses of primary PCA cells derived from these models identified several cancer stemness genes including CD24, EpCAM, and CD133 upregulated by KRASG12D. Among these stemness markers, we identified CD24 as a key driver of tumorigenesis and metastasis in vivo. These data demonstrate that specific factors involved in cancer stemness are critical for metastatic conversion of PCA and may be ideal targets for therapeutic intervention.

Convergent Synthesis of Sialyl LewisX- O-Core-1 Threonine

Selectins are a class of cell adhesion molecules that play a critical role during the initial steps of inflammation. The N-terminal domain of P-selectin glycoprotein ligand-1 (PSGL-1) binds to all selectins, but with the highest affinity to P-selectin. Recent evidence suggests that the blockade of P-selectin/PSGL-1 interactions provides a viable therapeutic option for the treatment of many inflammatory diseases. Herein, we report the total synthesis of threonine bearing sialyl LewisX (sLeX) linked to a Core-1- O-hexasaccharide 1, as a key glycan of the N-terminal domain of PSGL-1. A convergent synthesis using α-selective sialylation and a regioselective [4+2] glycosylation are the key features of this synthesis.

Preparation of 3-hydroxyquinolines from direct oxidation of dihydroquinolinium salts

A series of functionalized 3,4-dihydroquinolinium salts were prepared from the reaction of aryldiazonium salt with alkene in a nitrile solution. Further oxidation yielding either 3-hydroxyquinoline or quinoline products was investigated. A one-pot process from aryldiazonium salts, alkenes and nitriles leading to 3-hydroxyquinolines was also developed. Furthermore, an intramolecular trapping of an N-arylnitrilium ion with a vinyl group at the ortho position leading to 2-substituted quinolines was revealed.

3-Hydroxyquinoline derivatives can be prepared by a cascade cyclization of aryldiazonium salts with nitriles and alkenes followed by oxygenation.

Platelets and platelet adhesion molecules: novel mechanisms of thrombosis and anti-thrombotic therapies

Platelets are central mediators of thrombosis and hemostasis. At the site of vascular injury, platelet accumulation (i.e. adhesion and aggregation) constitutes the first wave of hemostasis. Blood coagulation, initiated by the coagulation cascades, is the second wave of thrombin generation and enhance phosphatidylserine exposure, can markedly potentiate cell-based thrombin generation and enhance blood coagulation. Recently, deposition of plasma fibronectin and other proteins onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that occurs prior to platelet accumulation (i.e. the classical first wave of hemostasis). These three waves of hemostasis, in the event of atherosclerotic plaque rupture, may turn pathogenic, and cause uncontrolled vessel occlusion and thrombotic disorders (e.g. heart attack and stroke). Current anti-platelet therapies have significantly reduced cardiovascular mortality, however, on-treatment thrombotic events, thrombocytopenia, and bleeding complications are still major concerns that continue to motivate innovation and drive therapeutic advances. Emerging evidence has brought platelet adhesion molecules back into the spotlight as targets for the development of novel anti-thrombotic agents. These potential antiplatelet targets mainly include the platelet receptors glycoprotein (GP) Ib-IX-V complex, β3 integrins (αIIb subunit and PSI domain of β3 subunit) and GPVI. Numerous efforts have been made aiming to balance the efficacy of inhibiting thrombosis without compromising hemostasis. This mini-review will update the mechanisms of thrombosis and the current state of antiplatelet therapies, and will focus on platelet adhesion molecules and the novel anti-thrombotic therapies that target them.

The Effect of Treatment of Vitamin D Deficiency on the Level of P-Selectin and hs-CRP in Patients With Thromboembolism: A Pilot Randomized Clinical Trial

Despite the known role of vitamin D deficiency in development of thrombosis, no studies have evaluated the impact of treating of vitamin D deficiency on the markers of thrombosis. A pilot randomized clinical trial was done on 40 vitamin D-deficient patients with deep vein thrombosis (DVT) or pulmonary embolism (PE). The intervention group received an oral dose of 50,000 IU vitamin D₃ every week for 8 weeks, followed by 1 pearl every 2 weeks for 4 weeks (a total of 3 months), while the control group did not receive vitamin D. Then, P-selectin and hs-CRP were measured at baseline and 1 and 3 months after the intervention. There was no significant decrease in hs-CRP in either group after 1 month (P = .955) or after 3 months (P = .525). Likewise, there was no significant decrease in P-selectin between the 2 groups after 1 month (P = .921) or 3 months (P = .795). The results indicated that treatment of vitamin D deficiency had no significant effect on hs-CRP or P-selectin after 3 months among DVT/PE patients. However, treatment of vitamin D deficiency in these patients resulted in the control of the international normalized ratio (INR) with the lower doses of warfarin. This observation is the first clinical report of enhancement of the anticoagulant effect of warfarin by the supplementing of vitamin D. Larger trials are needed to clearly show the effect of treating of vitamin D deficiency on thrombosis.

Cellular adhesion and the endothelium: P-selectin

P-selectin on endothelial cell surfaces is central to impaired microvascular blood flow in sickle cell disease (SCD). Restoration of blood flow is expected to provide therapeutic benefit for SCD patients, whatever the mechanism of action of the treatment. Long-term oral administration of a P-selectin-blocking agent potentially improves blood flow and averts acute painful vaso-occlusive crises in patients with SCD. This review focuses on the pathophysiology of the impairment of microvascular blood flow in SCD with an emphasis on the role of P-selectin and summarizes the status of development of antiselectin therapies as a means of improving microvascular flow.

The challenge of targeting notch in hematologic malignancies

Notch signaling can play oncogenic and tumor suppressor roles depending on cell type. Hematologic malignancies encompass a wide range of transformed cells, and consequently the roles of Notch are diverse in these diseases. For example Notch is a potent T-cell oncogene, with >50% of T-cell acute lymphoblastic leukemia (T-ALL) cases carry activating mutations in the Notch1 receptor. Targeting Notch signaling in T-ALL with gamma-secretase inhibitors, which prevent Notch receptor activation, has shown pre-clinical activity, and is under evaluation clinically. In contrast, Notch signaling inhibits acute myeloblastic leukemia growth and survival, and although targeting Notch signaling in AML with Notch activators appears to have pre-clinical activity, no Notch agonists are clinically available at this time. As such, despite accumulating evidence about the biology of Notch signaling in different hematologic cancers, which provide compelling clinical promise, we are only beginning to target this pathway clinically, either on or off. In this review, we will summarize the evidence for oncogenic and tumor suppressor roles of Notch in a wide range of leukemias and lymphomas, and describe therapeutic opportunities for now and the future.

Effect of PSI-697, a novel P-selectin inhibitor, on platelet-monocyte aggregate formation in humans

Background

Platelet activation is central to the pathogenesis of acute coronary syndromes. Surface expression of P‐selectin on activated platelets induces formation of platelet–monocyte aggregates and promotes vascular inflammation and thrombosis. P‐selectin antagonism may represent a novel therapeutic strategy in vascular disease. We aimed to investigate the effects of the novel P‐selectin antagonist PSI‐697 on platelet–monocyte aggregate formation in humans.

Methods and Results

In a double‐blind, randomized, placebo‐controlled crossover study, healthy smokers were randomized to receive either oral PSI‐697 600 mg or matched placebo. The sequence of treatment was also randomized, with all subjects receiving both PSI‐697 and placebo. Platelet–monocyte aggregates were measured by flow cytometry at 4 and 24 hours in the presence and absence of thrombin receptor‐activating peptide (TRAP; 0.1 to 1.0 μm/L). The ex vivo addition of TRAP caused a concentration‐dependent increase in platelet–monocyte aggregates from 8.2% to 94.8% (P<0.001). At 4 and 24 hours, plasma concentrations of PSI‐697 increased to 1906 and 83 ng/mL, respectively (P<0.001). PSI‐697 had no demonstrable effect on either stimulated or unstimulated platelet–monocyte aggregates at 4 or 24 hours (P>0.05). P‐selectin‐blocking antibody (CLB‐Thromb6), but not PSI‐697, inhibited both stimulated and unstimulated platelet–monocyte aggregate formation in vitro (P<0.001).

Conclusions

The novel small‐molecule P‐selectin antagonist PSI‐697 did not inhibit basal or stimulated platelet–monocyte aggregate formation in humans at the dose tested. Its clinical efficacy remains to be established.

Clinical Trial Registration

URL: http://EudraCT.ema.europa.eu Unique identifier: 2007‐005695‐14.

Pharmacological modulation of the inflammatory actions of platelets

Patients with inflammatory diseases often exhibit a change in platelet function, with these alterations being clearly distinct from the well-characterized role of platelets in haemostasis and thrombosis. It has recently been revealed that platelets can behave as innate inflammatory cells in immune responses with roles in leukocyte recruitment, migration into tissues, release of cytotoxic mediators, and in tissue remodelling following injury.Platelets exhibit a wide range of receptors for mediators involved in the inflammatory pathway and the immune response (Fig. 1). These include purinergic receptors, selectins, integrins, toll-like receptors, immunoglobulins, and chemokine receptors, but the precise role platelets play in the inflammatory process is still under investigation. Nevertheless, given that many of these receptors are distinct from those involved in thrombosis and haemostasis, this raises the real possibility of targeting these receptors to regulate inflammatory diseases without compromising haemostasis.

The human endogenous circadian system causes greatest platelet activation during the biological morning independent of behaviors

Background

Platelets are involved in the thromboses that are central to myocardial infarctions and ischemic strokes. Such adverse cardiovascular events have day/night patterns with peaks in the morning (∼9AM), potentially related to endogenous circadian clock control of platelet activation. The objective was to test if the human endogenous circadian system influences (1) platelet function and (2) platelet response to standardized behavioral stressors. We also aimed to compare the magnitude of any effects on platelet function caused by the circadian system with that caused by varied standardized behavioral stressors, including mental arithmetic, passive postural tilt and mild cycling exercise.

Methodology/Principal Findings

We studied 12 healthy adults (6 female) who lived in individual laboratory suites in dim light for 240 h, with all behaviors scheduled on a 20-h recurring cycle to permit assessment of endogenous circadian function independent from environmental and behavioral effects including the sleep/wake cycle. Circadian phase was assessed from core body temperature. There were highly significant endogenous circadian rhythms in platelet surface activated glycoprotein (GP) IIb-IIIa, GPIb and P-selectin (6–17% peak-trough amplitudes; p≤0.01). These circadian peaks occurred at a circadian phase corresponding to 8–9AM. Platelet count, ATP release, aggregability, and plasma epinephrine also had significant circadian rhythms but with later peaks (corresponding to 3–8PM). The circadian effects on the platelet activation markers were always larger than that of any of the three behavioral stressors.

Conclusions/Significance

These data demonstrate robust effects of the endogenous circadian system on platelet activation in humans—independent of the sleep/wake cycle, other behavioral influences and the environment. The ∼9AM timing of the circadian peaks of the three platelet surface markers, including platelet surface activated GPIIb-IIIa, the final common pathway of platelet aggregation, suggests that endogenous circadian influences on platelet function could contribute to the morning peak in adverse cardiovascular events as seen in many epidemiological studies.

Venous valvular stasis-associated hypoxia and thrombosis: what is the link?

This review focuses on the role of the venous valves in the genesis of thrombus formation in venous thromboembolic disease (VTE). Clinical VTE and the evidence for the valvular origin of venous thrombosis are reviewed. Virchow's triad is then used as a framework for discussion to approach the question posed regarding the link between venous valvular stasis-associated hypoxia and thrombosis. Thus, the effects of blood flow stasis, hypercoagulability of blood, and the characteristics of the vessel wall within the venous valvular sinus are assessed in turn.

Targeting P-selectin in acute pancreatitis

IMPORTANCE OF THE FIELD

Acute pancreatitis (AP) is a multifactorial disorder not fully understood yet. In particular, the pathogenetic pathways promoting a severe life-threatening course of AP are the subject of ongoing investigations. P-selectin has been shown to play a central role in the complex pathophysiology in AP as well as various other inflammatory conditions.

AREAS COVERED IN THIS REVIEW

P-selectin function in AP is reviewed with focus on its dual function as a mediator of leukocyte recruitment and cell adhesion, which implies the unique effect of linking both inflammation and coagulation, especially in the progression from mild to severe necrotizing AP. Potential therapeutic aspects are discussed with regard to the clinical situation.

WHAT THE READER WILL GAIN

A better understanding of the pathogenic role of P-selectin in AP and of the rationale for a therapeutic blockade.

TAKE HOME MESSAGE

P-selectin is a glycoprotein that mediates the adhesion of activated platelets and leukocytes to the vessel wall in various inflammatory conditions. Both pathophysiological steps are closely linked and play a key role in the course of severe AP. A treatment approach by inhibition of P-selectin could be of distinct interest as a therapeutic option in severe AP.

Discovery of 2-[1-(4-chlorophenyl)cyclopropyl]-3-hydroxy-8-(trifluoromethyl)quinoline-4-carboxylic acid (PSI-421), a P-selectin inhibitor with improved pharmacokinetic properties and oral efficacy in models of vascular injury

Previously, we reported the discovery of PSI-697 (1a), a C-2 benzyl substituted quinoline salicylic acid-based P-selectin inhibitor. It is active in a variety of animal models of cardiovascular disease. Compound 1a has also been shown to be well tolerated and safe in healthy volunteers at doses of up to 1200 mg in a phase 1 single ascending dose study. However, its oral bioavailability was low. Our goal was to identify a back up compound with equal potency, increased solubility, and increased exposure. We expanded our structure-activity studies in this series by branching at the alpha position of the C-2 benzyl side chain and through modification of substituents on the carboxylic A-ring of the quinoline. This resulted in discovery of PSI-421 with marked improvement in aqueous solubility and pharmacokinetic properties. This compound has shown oral efficacy in animal models of arterial and venous injury and was selected as a preclinical development compound for potential treatment of such diseases as atherosclerosis and deep vein thrombosis.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.

P-selectin antagonism reduces thrombus formation in humans

BACKGROUND

Interaction of P-selectin with its glycoprotein ligand (P-selectin glycoprotein ligand type 1) mediates inflammatory processes that may also include vascular thrombosis. Platelet P-selectin expression is increased in patients with coronary heart disease, and its antagonism represents a potential future therapeutic target for the prevention and treatment of atherothrombosis.

AIM

To investigate the effects of the novel small molecule P-selectin antagonist PSI-697 on thrombus formation in humans.

METHODS AND RESULTS

In a double-blind randomized crossover study, thrombus formation was measured in 12 healthy volunteers, using the Badimon ex vivo perfusion chamber under conditions of low and high shear stress. Saline placebo, low-dose (2 m) and high-dose (20 m) PSI-697 and the glycoprotein IIb-IIIa receptor antagonist tirofiban (50 ng mL(-1)) were administered into the extracorporeal circuit prior to the perfusion chamber. As compared with saline placebo, blockade of platelet glycoprotein IIb-IIIa receptor with tirofiban produced 28% and 56% reductions in thrombus formation in the low-shear and high-shear chambers, respectively. PSI-697 caused a dose-dependent, but more modest, reduction in thrombus formation. Low-dose PSI-796 (2 m) reduced total thrombus area by 14% (P = 0.04) and 30% (P = 0.0002) in the low-shear and high-shear chambers, respectively. At the high dose (20 m), PSI-697 reduced total thrombus area by 18% (P = 0.0094) and 41% (P = 0.0008) in the low-shear and high-shear chambers, respectively.

CONCLUSIONS

P-selectin antagonism with PSI-697 reduces ex vivo thrombus formation in humans. These findings provide further evidence that P-selectin antagonism may be a potential target for the prevention and treatment of cardiovascular disease.