Characterization of Novel P-Selectin Targeted Complement Inhibitors in Murine Models of Hindlimb Injury and Transplantation

The complement system has long been recognized as a potential druggable target for a variety of inflammatory conditions. Very few complement inhibitors have been approved for clinical use, but a great number are in clinical development, nearly all of which systemically inhibit complement. There are benefits of targeting complement inhibition to sites of activation/disease in terms of efficacy and safety, and here we describe P-selectin targeted complement inhibitors, with and without a dual function of directly blocking P-selectin-mediated cell-adhesion. The constructs are characterized in vitro and in murine models of hindlimb ischemia/reperfusion injury and hindlimb transplantation. Both constructs specifically targeted to reperfused hindlimb and provided protection in the hindlimb ischemia/reperfusion injury model. The P-selectin blocking construct was the more efficacious, which correlated with less myeloid cell infiltration, but with similarly reduced levels of complement deposition. The blocking construct also improved tissue perfusion and, unlike the nonblocking construct, inhibited coagulation, raising the possibility of differential application of each construct, such as in thrombotic vs. hemorrhagic conditions. Similar outcomes were obtained with the blocking construct following vascularized composite graft transplantation, and treatment also significantly increased graft survival. This is outcome may be particularly pertinent in the context of vascularized composite allograft transplantation, since reduced ischemia reperfusion injury is linked to a less rigorous alloimmune response that may translate to the requirement of a less aggressive immunosuppressive regime for this normally nonlife-threatening procedure. In summary, we describe a new generation of targeted complement inhibitor with multi-functionality that includes targeting to vascular injury, P-selectin blockade, complement inhibition and anti-thrombotic activity. The constructs described also bound to both mouse and human P-selectin which may facilitate potential translation.

A PSGL-1 glycomimetic reduces thrombus burden without affecting hemostasis

Events mediated by the P-selectin/PSGL-1 pathway play a critical role in the initiation and propagation of venous thrombosis by facilitating the accumulation of leukocytes and platelets within the growing thrombus. Activated platelets and endothelium express P-selectin, which binds P-selectin glycoprotein ligand-1 (PSGL-1) that is expressed on the surface of all leukocytes. We developed a pegylated glycomimetic of the N terminus of PSGL-1, PEG40-GSnP-6 (P-G6), which proved to be a highly potent P-selectin inhibitor with a favorable pharmacokinetic profile for clinical translation. P-G6 inhibits human and mouse platelet-monocyte and platelet-neutrophil aggregation in vitro and blocks microcirculatory platelet-leukocyte interactions in vivo. Administration of P-G6 reduces thrombus formation in a nonocclusive model of deep vein thrombosis with a commensurate reduction in leukocyte accumulation, but without disruption of hemostasis. P-G6 potently inhibits the P-selectin/PSGL-1 pathway and represents a promising drug candidate for the prevention of venous thrombosis without increased bleeding risk.

P-selectin antibody treatment after blunt thoracic trauma prevents early pulmonary arterial thrombosis without changes in viscoelastic measurements of coagulation

INTRODUCTION

Previously, in a murine model of blunt thoracic trauma, we provided evidence of primary pulmonary thrombosis associated with increased expression of the cell adhesion molecule, P-selectin. In this study, mice are treated with P-selectin blocking antibody after injury to investigate the clinical viability of this antibody for the prevention of pulmonary thrombosis. In addition, viscoelastic testing is performed to investigate if P-selectin inhibition has a detrimental impact on normal hemostasis.

METHODS

A murine model of thoracic trauma was used. Mice were divided into sham control and experimental injury groups. Thirty minutes after trauma, mice were treated with the following: P-selectin blocking antibody, isotype control antibody, low-dose heparin, high-dose heparin, or normal saline. At 90 minutes, whole blood was collected for characterization of coagulation by viscoelastic coagulation monitor (VCM Vet; Entegrion, Durham, NC). Mean clotting time, clot formation time, clot kinetics (α angle), and maximum clot firmness were compared between each treatment group.

RESULTS

Mice that received P-selectin antibody 30 minutes after blunt thoracic trauma had four- to fivefold less (p < 0.001) arterial fibrin accumulation than those that received the isotype control. In both sham and trauma groups, compared with vehicle (normal saline) alone, no statistical difference was noted in any coagulation parameters after injection with P-selectin antibody, isotype control, or low-dose heparin. In addition, blinded histopathological evaluation yielded no difference in hemorrhage scores between injured mice treated with P-selectin blocking antibody and those treated with isotype antibody control.

CONCLUSION

This study supports the clinical use of P-selectin blocking antibody for the prevention of pulmonary thrombosis by confirming its efficacy when given after a blunt thoracic trauma. In addition, we demonstrated that the administration of P-selectin antibody does not adversely affect systemic coagulation as measured by viscoelastic testing, suggesting that P-selectin antibody can be safely given during the acute posttraumatic period.

P-selectin axis plays a key role in microglia immunophenotype and glioblastoma progression

Glioblastoma (GB) is a highly invasive type of brain cancer exhibiting poor prognosis. As such, its microenvironment plays a crucial role in its progression. Among the brain stromal cells, the microglia were shown to facilitate GB invasion and immunosuppression. However, the reciprocal mechanisms by which GB cells alter microglia/macrophages behavior are not fully understood. We propose that these mechanisms involve adhesion molecules such as the Selectins family. These proteins are involved in immune modulation and cancer immunity. We show that P-selectin mediates microglia-enhanced GB proliferation and invasion by altering microglia/macrophages activation state. We demonstrate these findings by pharmacological and molecular inhibition of P-selectin which leads to reduced tumor growth and increased survival in GB mouse models. Our work sheds light on tumor-associated microglia/macrophage function and the mechanisms by which GB cells suppress the immune system and invade the brain, paving the way to exploit P-selectin as a target for GB therapy.

Fucoidan-based micelles as P-selectin targeted carriers for synergistic treatment of acute kidney injury

Acute kidney injury (AKI) is a life-threatening disease without effective treatment. The utilization of curcumin (Cur) for the treatment of AKI is still facing challenges due to its poor water-solubility and low bioavailability. Herein, kidney-targeted octenyl succinic anhydride-grafted fucoidan loaded with Cur (OSA-Fucoidan/Cur) was fabricated for synergistic treatment of AKI. It was found that OSA-Fucoidan/Cur micelles had a sustained drug release behavior and excellent physicochemical stability. Cellular uptake studies demonstrated that the specific binding between fucoidan and P-selectin overexpressed on H2O2-stimulated HUVECs contributed to the higher internalization of OSA-Fucoidan/Cur micelles by the cells. In addition, OSA-Fucoidan micelles exhibited an ideal kidney-targeted characteristic in lipopolysaccharide (LPS)-induced AKI mice. In vivo studies showed that the combination of Cur and OSA-Fucoidan endowed the OSA-Fucoidan/Cur micelles with synergistically anti-inflammatory and antioxidant abilities, thereby largely enhancing the therapeutic efficacy of AKI. Therefore, OSA-Fucoidan/Cur micelles may represent a potential kidney-targeted nanomedicine for effective treatment of AKI.

Microwave Responsive Nanoplatform via P-Selectin Mediated Drug Delivery for Treatment of Hepatocellular Carcinoma with Distant Metastasis

Hepatocellular carcinoma (HCC) with metastatic disease is associated with a low survival in clinical practice. Many curative options including liver resection, transplantation, and thermal ablation are effective in local but limited for patients with distant metastasis. In this study, the efficacy, specificity, and safety of P-selectin targeted delivery and microwave (MW) responsive drug release is investigated for development of HCC therapy. By encapsulating doxorubicin (DOX) and MW sensitizer (1-butyl-3-methylimidazolium-l-lactate, BML) into fucoidan conjugated liposomal nanoparticles (TBP@DOX), specific accumulation and prominent release of DOX in orthotopic HCC and lung metastasis are achieved with adjuvant MW exposure. This results in orthotopic HCC growth inhibition that is not only 1.95-fold higher than found for nontargeted BP@DOX and 1.6-fold higher than nonstimuli responsive TP@DOX but is also equivalent to treatment with free DOX at a 10-fold higher dose. Furthermore, the optimum anticancer efficacy against distant lung metastasis and effective prevention of widespread dissemination with a prolonged survival is described. In addition, no adverse metabolic events are identified using the TBP@DOX nanodelivery system despite these events being commonly observed with traditional DOX chemotherapy. Therefore, administering TBP@DOX with MW exposure could potentially enhance the therapeutic efficacy of thermal-chemotherapy of HCC, especially those in the advanced stages.

Design and development of ICCA as a dual inhibitor of GPIIb/IIIa and P-selectin receptors

BACKGROUND

The impact of upregulation of platelet membrane glycoprotein (GP)IIb/IIIa and P-selectin on the onset of arterial thrombosis, venous thrombosis, and cancer encourages to hypothesize that dual inhibitor of GPIIb/IIIa and P-selectin receptors should simultaneously inhibit arterial thrombosis, block venous thrombosis, and slow tumor growth.

METHODS

For this reason, the structural characteristics and the CDOCKER interaction energies of 12 carbolines were analyzed. This led to the design of 1-(4-isopropyl-phenyl)-β-carboline-3-carboxylic acid (ICCA) as a promising inhibitor of GPIIb/IIIa and P-selectin receptors.

RESULTS

The synthetic route provided ICCA in 48% total yield and 99.6% high-performance liquid chromatography purity. In vivo 5 μmol/kg oral ICCA downregulated GPIIb/IIIa and P-selectin expression thereby inhibited arterial thrombosis, blocked venous thrombosis, and slowed down tumor growth, but did not damage the kidney and the liver.

CONCLUSION

Therefore, ICCA could be a promising candidate capable of downregulating GPIIb/IIIa and P-selectin receptors, inhibiting arterial thrombosis, blocking venous thrombosis, and slowing down tumor growth.

ATIQCTPC: a nanomedicine capable of targeting tumor and blocking thrombosis in vivo

To overcome the harmful side effects, low tolerance, and undesirable outcomes of the anticancer drugs, we used ethane-1,2-diamine to bridge antitumoral (S)-3-acetyl-4-oxo-tetrahydroindolo[2,3-a]quinolizine-6-carboxylic acid (ATIQC) and tumor-targeting d-glucuronic acid, thereby providing (6S)-3-acetyl-4-oxo-N-(2-(3,4,5,6-tetrahydroxytetrahydro-2H-pyran-2-carboxamido)ethyl)-4,6,7,12-tetrahydroindolo[2,3-a]quinolizine-6-carboxamide (ATIQCTPC). Atomic force microscopy images visualized, that in serum, ATIQCTPC formed particles of height <81 nm. These particles effectively avoided phagocytosis of macrophages and were stable in blood circulation. Distribution analysis indicated that ATIQCTPC accumulated and released ATIQC in the tumor tissue through a targeting manner. Thus, the antitumor and the anti-thrombotic activities of ATIQCTPC were 100-fold higher than those of ATIQC, and ATIQCTPC was able to prevent cancer patients from suffering from thrombosis. Based on the observation that ATIQCTPC decreased serum tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) in S180 mice, we hypothesized that this is the mechanism that ATIQCTPC utilized to slow tumor growth. Additionally, we observed that ATIQCTPC inhibited thrombosis by decreasing serum P-selectin of thrombotic rats. The intermolecular association and the hexamerization manner of ATIQCTPC were experimentally evidenced and correlated with the formation of the nanoparticles.

Crizanlizumab for the Prevention of Pain Crises in Sickle Cell Disease

BACKGROUND

The up-regulation of P-selectin in endothelial cells and platelets contributes to the cell-cell interactions that are involved in the pathogenesis of vaso-occlusion and sickle cell-related pain crises. The safety and efficacy of crizanlizumab, an antibody against the adhesion molecule P-selectin, were evaluated in patients with sickle cell disease.

METHODS

In this double-blind, randomized, placebo-controlled, phase 2 trial, we assigned patients to receive low-dose crizanlizumab (2.5 mg per kilogram of body weight), high-dose crizanlizumab (5.0 mg per kilogram), or placebo, administered intravenously 14 times over a period of 52 weeks. Patients who were receiving concomitant hydroxyurea as well as those not receiving hydroxyurea were included in the study. The primary end point was the annual rate of sickle cell-related pain crises with high-dose crizanlizumab versus placebo. The annual rate of days hospitalized, the times to first and second crises, annual rates of uncomplicated crises (defined as crises other than the acute chest syndrome, hepatic sequestration, splenic sequestration, or priapism) and the acute chest syndrome, and patient-reported outcomes were also assessed.

RESULTS

A total of 198 patients underwent randomization at 60 sites. The median rate of crises per year was 1.63 with high-dose crizanlizumab versus 2.98 with placebo (indicating a 45.3% lower rate with high-dose crizanlizumab, P=0.01). The median time to the first crisis was significantly longer with high-dose crizanlizumab than with placebo (4.07 vs. 1.38 months, P=0.001), as was the median time to the second crisis (10.32 vs. 5.09 months, P=0.02). The median rate of uncomplicated crises per year was 1.08 with high-dose crizanlizumab, as compared with 2.91 with placebo (indicating a 62.9% lower rate with high-dose crizanlizumab, P=0.02). Adverse events that occurred in 10% or more of the patients in either active-treatment group and at a frequency that was at least twice as high as that in the placebo group were arthralgia, diarrhea, pruritus, vomiting, and chest pain.

CONCLUSIONS

In patients with sickle cell disease, crizanlizumab therapy resulted in a significantly lower rate of sickle cell-related pain crises than placebo and was associated with a low incidence of adverse events. (Funded by Selexys Pharmaceuticals and others; SUSTAIN ClinicalTrials.gov number, NCT01895361 .).

Better Nanoparticle Targeting with P-Selectin

A study in mice indicates that the adhesion molecule P-selectin, which is expressed on the endothelium during inflammation, may serve as a target for the delivery of drug-filled nanoparticles to tumors. Antitumor efficacy was achieved in several mouse models of cancer, and the researchers successfully used this approach even against noninflammatory tumors, by first using ionizing radiation to trigger P-selectin's expression on the tumor vasculature.

Inhibitory function of P-selectin-mediated leukocyte adhesion by the polysaccharides from Sanguisorba officinalis

CONTEXT

P-selectin is a promising target for inflammatory-related diseases. Polysaccharides are the active ingredients of Sanguisorba officinalis L. (Rosaceae) responsible for its anti-inflammatory activities; however, the molecular mechanism is not clear yet.

OBJECTIVE

This study evaluates the effects of polysaccharides (SOPs) from Sanguisorba officinalis on their antagonistic function against P-selectin-mediated leukocyte adhesion.

MATERIALS AND METHODS

The antagonistic function of SOPs was investigated by flow cytometry and static adhesion assay at the concentrations of 25 and 100 μg/ml. The dynamic interaction between HL-60 cells and CHO-P cell monolayer treated with SOPs (25 and 100 μg/ml) was analyzed in a parallel plate flow chamber, and quantitatively calculated by ImageJ software (NIH, Bethesda, MD). In vitro protein binding assay was carried out to evaluate the blocking effects of SOPs (25 and 100 μg/ml) on the interaction between P-selectin and PSGL-1.

RESULTS

SOPs-treatment (100 μg/ml) significantly reduced the percentage of HL-60 cells binding to P-selectin (p < 0.01) determined by flow cytometry. In addition, SOPs (25 and 100 μg/ml) markedly blocked the adhesion between HL-60 cells and CHO-P cells under static condition, and the inhibitory rates reached 39.9% and 71.2%, respectively. Compared with the positive control group, SOPs-treatment (25 and 100 μg/ml) significantly reduced the percentage of HL-60 cells rolling on CHO-P cell monolayers by 43.5% and 75.2%, respectively. Protein binding assay showed the interaction between P-selectin and PSGL-1 was significantly blocked by SOPs.

DISCUSSION AND CONCLUSION

SOPs possess a significant antagonistic function against P-selectin-mediated leukocyte adhesion, and SOPs could be considered as a promising candidate for amelioration of inflammation-related diseases.

SDA, a DNA aptamer inhibiting E- and P-selectin mediated adhesion of cancer and leukemia cells, the first and pivotal step in transendothelial migration during metastasis formation

Endothelial (E-) and platelet (P-) selectin mediated adhesion of tumor cells to vascular endothelium is a pivotal step of hematogenous metastasis formation. Recent studies have demonstrated that selectin deficiency significantly reduces metastasis formation in vivo. We selected an E- and P-Selectin specific DNA Aptamer (SDA) via SELEX (Systematic Evolution of Ligands by EXponential enrichment) with a K_d value of approximately 100 nM and the capability of inhibiting the interaction between selectin and its ligands. Employing human colorectal cancer (HT29) and leukemia (EOL-1) cell lines we could demonstrate an anti-adhesive effect for SDA in vitro. Under physiological shear stress conditions in a laminar flow adhesion assay, SDA inhibited dynamic tumor cell adhesion to immobilized E- or P-selectin. The stability of SDA for more than two hours allowed its application in cell-cell adhesion assays in cell culture medium. When adhesion of HT29 cells to TNFα-stimulated E-selectin presenting human pulmonary microvascular endothelial cells was analyzed, inhibition via SDA could be demonstrated as well. In conclusion, SDA is a potential new therapeutic agent that antagonizes selectin-mediated adhesion during metastasis formation in human malignancies.

A potent oral P-selectin blocking agent improves microcirculatory blood flow and a marker of endothelial cell injury in patients with sickle cell disease

Abnormal blood flow accounts for most of the clinical morbidity of sickle cell disease (SCD) [1,2]. Most notably, occlusion of flow in the microvasculature causes the acute pain crises [3] that are the commonest cause for patients with SCD to seek medical attention [4] and major determinants of their quality of life [5]. Based on evidence that endothelial P-selectin is central to the abnormal blood flow in SCD we provide results from four of our studies that are germane to microvascular blood flow in SCD. A proof-of-principle study established that doses of heparin lower than what are used for anticoagulation but sufficient to block P-selectin improved microvascular blood flow inpatients with SCD. An in vitro study showed that Pentosan Polysulfate Sodium (PPS) had greater P-selectin blocking activity than heparin. A Phase I clinical study demonstrated that a single oral dose of PPS increased microvascular blood flow in patients with SCD. A Phase II clinical study that was not completed documented that daily oral doses of PPS administered for 8 weeks lowered plasma levels of sVCAM-1 and tended to improve microvascular blood flow in patients with SCD. These data support the concept that P-selectin on the microvascular endothelium is critical to both acute vascular occlusion and chronically impaired microvascular blood flow in SCD. They also demonstrate that oral PPS is beneficial to microvascular sickle cell blood flow and has potential as an efficacious agent for long-term prophylactic therapy of SCD.

P-selectin mediates neutrophil rolling and recruitment in acute pancreatitis

BACKGROUND

The adhesive mechanisms regulating leucocyte-endothelium interactions in the pancreas remain elusive, but selectins may play a role. This study examined the molecular mechanisms mediating leucocyte rolling along the endothelium in the pancreas and the therapeutic potential of targeting the rolling adhesive interaction in acute pancreatitis (AP).

METHODS

Pancreatitis was induced by retrograde infusion of 5 per cent sodium taurocholate into the pancreatic duct, repeated intraperitoneal administration of caerulein (50 µg/kg) or intraperitoneal administration of L-arginine (4 g/kg) in C57BL/6 mice. A control and a monoclonal antibody against P-selectin were administered before and after induction of AP. Serum and tissue were sampled to assess the severity of pancreatitis, and intravital microscopy was used to study leucocyte rolling.

RESULTS

Taurocholate infusion into the pancreatic duct increased the serum level of trypsinogen, trypsinogen activation, pancreatic neutrophil infiltration, macrophage inflammatory protein (MIP) 2 formation and tissue damage. Immunoneutralization of P-selectin decreased the taurocholate-induced increase in serum trypsinogen (median (range) 17·35 (12·20-30·00) versus 1·55 (0·60-15·70) µg/l; P = 0·017), neutrophil accumulation (4·00 (0·75-4·00) versus 0·63 (0-3·25); P = 0·002) and tissue damage, but had no effect on MIP-2 production (14·08 (1·68-33·38) versus 3·70 (0·55-51·80) pg/mg; P = 0·195) or serum trypsinogen activating peptide level (1·10 (0·60-1·60) versus 0·45 (0-1·80) µg/l; P = 0·069). Intravital fluorescence microscopy revealed that anti-P-selectin antibody inhibited leucocyte rolling completely in postcapillary venules of the inflamed pancreas.

CONCLUSION

Inhibition of P-selectin protected against pancreatic tissue injury in experimental pancreatitis. Targeting P-selectin may be an effective strategy to ameliorate inflammation in AP.

Ascidian dermatan sulfates attenuate metastasis, inflammation and thrombosis by inhibition of P-selectin

BACKGROUND

Cancer-associated thrombosis and enduring inflammation are strongly associated with cancer progression and metastasis. Heparin is the mostly clinically used anticoagulant/antithrombotic drug, and has recently been shown to exhibit antimetastatic and anti-inflammatory activities that are linked to inhibition of P-selectin and/or L-selectin. P-selectin-mediated platelet-tumor cell and tumor cell-endothelium interactions facilitate the initial steps of metastasis.

OBJECTIVES AND METHODS

The aim of the present study was to determine the capacity of dermatan sulfates to inhibit P-selectin and to test their potential to affect thrombosis, inflammation and metastasis in respective experimental mouse models.

RESULTS

Two dermatan sulfates isolated from the ascidians Styela plicata and Phallusia nigra, composed of the same disaccharide core structure (IdoA2-GalNAc)(n) , but sulfated at carbon 4 or 6 of the GalNAc, respectively, have opposed heparin cofactor II (HCII) activities and are potent inhibitors of P-selectin. The ascidian dermatan sulfates effectively attenuated metastasis of both MC-38 colon carcinoma and B16-BL6 melanoma cells and the infiltration of inflammatory cells in a thioglycollate peritonitis mouse model. Moreover, both glycosaminoglycans reduced thrombus size in an FeCl(3) -induced arterial thrombosis model, irrespective of their HCII activities. The analysis of arterial thrombi demonstrated markedly reduced platelet deposition after dermatan sulfate treatment, suggesting that the glycosaminoglycan inhibited P-selectin and thereby the binding of activated platelets during thrombus formation.

CONCLUSIONS

Collectively, these findings provide evidence that specific inhibition of P-selectin represents a potential therapeutic target in thrombosis, inflammation and metastasis, and that ascidian dermatan sulfates may serve as antiselectin agents.

E- and P-selectin: differences, similarities and implications for the design of P-selectin antagonists

Selectins form a family of Ca2+ -dependent carbohydrate binding proteins that mediate the initial step of leukocyte recruitment in the inflammatory process. Blocking of selectins is therefore considered a promising therapeutic approach to treat acute and chronic inflammatory diseases which are caused by excessive extravasation of leukocytes. This mini-review highlights the major structural differences between E- and P-selectin and summarizes the resulting strategies for the design of selectin antagonists.

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.

Isolation and characterization of N-feruloyltyramine as the P-selectin expression suppressor from garlic (Allium sativum)

Garlic (Allium sativum) is a medicinal and culinary plant reported to have several positive health effects on cardiovascular diseases, particularly via suppressing platelet activation. Therefore, active compounds inhibiting platelet activation were isolated from garlic extract using a P-selectin expression suppressing activity-guided fractionation technique. Garlic cloves were extracted with methanol, sequentially partitioned using ethyl acetate, and n-butanol. The ethyl acetate portion was fractionated using silica gel chromatography. The fraction with highest P-selectin expression suppressing activity was further purified using HPLC, and the compounds in the fraction were analyzed using MS, MS/MS, and NMR spectroscopic methods. Using NMR spectroscopy, the compound with highest suppressing activity was confirmed as N-feruloyltyramine. At the concentration of 0.05 microM, N-feruloyltyramine was able to suppress P-selectin expression on platelets by 31% (P < 0.016). Since COX enzymes are deeply involved in the regulation of P-selectin expression on platelets, potential effects of N-feruloyltyramine on COX enzymes were investigated. As expected at the concentration of 0.05 microM, N-feruloyltyramine was found to be a very potent compound able to inhibit COX-I and -II enzymes by 43% (P < 0.012) and 33% (P < 0.014), respectively. N-Feruloyltyramine is likely to inhibit COX enzymes, thereby suppressing P-selectin expression on platelets.

Effect of curcumin on the adhesion of platelets to brain microvascular endothelial cells in vitro

AIM

To determine whether curcumin prevents the adhesion of platelets to brain microvascular endothelial cells (BMECs) cultured in vitro.

METHODS

[3H]Adenine- labeled platelets were incubated with BMECs to investigate the role of curcumin in the adhesion of platelets to BMECs. The number of platelets adhering to the BMECs monolayer was determined by liquid scintillation spectroscopy. The thrombin-induced expression of platelets P-selectin, glycoprotein IIb (GPIIb), and glycoprotein IIIa (GPIIIa) on the cell surface, was measured by flow cytometry. P-selectin mRNA levels of BMECs were determined by RT-PCR. The TNF-alpha- induced expressions of P-selectin and E-selectin on the surface of BMECs were determined by Western blotting.

RESULTS

The adhesion between thrombin-activated platelets and normal BMECs, and that of TNF-alpha-activated BMECs and normal platelets were significantly increased, and this increase could be inhibited by curcumin (30-240 micromol/L) in a concentration-dependant manner. The platelets activated with thrombin and BMECs stimulated by TNF-alpha demonstrated an upregulated expressions of P-selectin and E-selectin, and this increase, when pretreated with curcumin for 30 min, could be restrained dose dependently. Curcumin also inhibited the increase of the GPIIb/GPIIIa expression of thrombinactivated platelets in a concentration-dependent manner.

CONCLUSION

Curcumin can inhibit the platelets to BMECs. This effect may be related to the decreased expressions of P-selectin, E-selectin, and GPIIb/GPIIIa on platelets and BMECs.