DMSO inhibits human platelet activation through cyclooxygenase-1 inhibition. A novel agent for drug eluting stents?

MMP-2 knockdown blunts age-dependent carotid stiffness by decreasing elastin degradation and augmenting eNOS activation

AIMS

Arterial stiffness is a hallmark of vascular aging that precedes and strongly predicts the development of cardiovascular diseases. Age-dependent stiffening of large elastic arteries is primarily attributed to increased levels of matrix metalloproteinase-2 (MMP-2). However, the mechanistic link between age-dependent arterial stiffness and MMP-2 remains unclear. Thus, we aimed to investigate the efficacy of MMP-2 knockdown using small interfering RNA (siRNA) on age-dependent arterial stiffness.

METHODS AND RESULTS

Pulse wave velocity (PWV) was assessed in right carotid artery of wild type (WT) mice from different age groups. MMP-2 levels in the carotid artery and plasma of young (3 months) and old (20-25 months) WT mice were determined. Carotid PWV as well as vascular and circulating MMP-2 were elevated with increasing age in mice. Old WT mice (18-21-month-old) were treated for 4 weeks with either MMP-2 or scrambled (Scr) siRNA via tail vein injection. Carotid PWV was assessed at baseline, 2 and 4 weeks after start of the treatment. MMP-2 knockdown reduced vascular MMP-2 levels and attenuated age-dependent carotid stiffness. siMMP-2 treated mice showed increased elastin to collagen ratio, lower plasma desmosine (DES), enhanced phosphorylation of endothelial nitric oxide synthase (eNOS) and higher levels of vascular cyclic guanosine monophosphate (cGMP). An age-dependent increase in direct protein-protein interaction between MMP-2 and eNOS was also observed. Lastly, DES, an elastin breakdown product, was measured in a patient cohort (n = 64, 23-86 years old), where carotid-femoral PWV was also assessed; here, plasma levels of DES directly correlated with age and arterial stiffness.

CONCLUSION

MMP-2 knockdown attenuates age-dependent carotid stiffness by blunting elastin degradation and augmenting eNOS bioavailability. Given the increasing clinical use of siRNA technology, MMP2 knockdown should be investigated further as a possible strategy to mitigate age-dependent arterial stiffness and related CV diseases.

TRANSLATIONAL PERSPECTIVE

Arterial stiffness is a hallmark of vascular aging that precedes and strongly predicts the development of cardiovascular diseases. This study provides translational evidence to support a key role for MMP-2 on the development of age-associated arterial stiffness. Silencing of MMP-2 using siRNA technology shows an effect on aged mice where it attenuates age-dependent carotid stiffness by reducing elastin degradation and increasing eNOS bioavailability. Additionally, in humans we show that elastin breakdown increases with age and increased PWV. These findings indicate MMP-2 knockdown as a promising novel strategy to attenuate age-dependent arterial stiffness and cardiovascular diseases.

Vitrification with microinjection of single seminiferous tubules: an efficient cryopreservation approach for limited testicular tissue

RESEARCH QUESTION

Is vitrification with microinjection of single seminiferous tubules an efficient cryopreservation approach for limited testicular tissue?

DESIGN

Testicular tissue from 10 patients with normal spermatogenesis were assigned to a fresh control group or one of the following cryopreservation procedures: uncontrolled slow freezing (USF) using either 1.5 or 2.1 M DMSO combined with sucrose and vitrification with or without single seminiferous tubules microinjection.

RESULTS

Single seminiferous tubules microinjected with cryoprotective agents (CPA) enhanced the penetration of CPA compared with CPA-treated testicular tissue fragments. Microinjection of seminiferous tubules (VLP) maintained tubule structural integrity and germ cell numbers, and reduced spermatogonial apoptosis after cryopreservation compared with vitrification without microinjection (apoptosis rate: VLP versus vitrification without microinjection, P = 0.047; VLP versus USF, P= 0.049). Freezing of single seminiferous tubules using 0.25-ml straws and traditional sperm freezing methods protected sperm retrieval and recovery rates, and the progressive motility index.

CONCLUSIONS

Vitrification of single seminiferous tubule with microinjection of low CPA concentration is an effective approach to testicular cryopreservation.

Sirtuin 5 promotes arterial thrombosis by blunting the fibrinolytic system

AIMS

Arterial thrombosis as a result of plaque rupture or erosion is a key event in acute cardiovascular events. Sirtuin 5 (SIRT5) belongs to the lifespan-regulating sirtuin superfamily and has been implicated in acute ischaemic stroke and cardiac hypertrophy. This project aims at investigating the role of SIRT5 in arterial thrombus formation.

METHODS AND RESULTS

Sirt5 transgenic (Sirt5Tg/0) and knock-out (Sirt5-/-) mice underwent photochemically induced carotid endothelial injury to trigger arterial thrombosis. Primary human aortic endothelial cells (HAECs) were treated with SIRT5 silencing-RNA (si-SIRT5) as well as peripheral blood mononuclear cells from acute coronary syndrome (ACS) patients and non-ACS controls (case-control study, total n = 171) were used to increase the translational relevance of our data. Compared to wild-type controls, Sirt5Tg/0 mice displayed accelerated arterial thrombus formation following endothelial-specific damage. Conversely, in Sirt5-/- mice, arterial thrombosis was blunted. Platelet function was unaltered, as assessed by ex vivo collagen-induced aggregometry. Similarly, activation of the coagulation cascade as assessed by vascular and plasma tissue factor (TF) and TF pathway inhibitor expression was unaltered. Increased thrombus embolization episodes and circulating D-dimer levels suggested augmented activation of the fibrinolytic system in Sirt5-/- mice. Accordingly, Sirt5-/- mice showed reduced plasma and vascular expression of the fibrinolysis inhibitor plasminogen activator inhibitor (PAI)-1. In HAECs, SIRT5-silencing inhibited PAI-1 gene and protein expression in response to TNF-α. This effect was mediated by increased AMPK activation and reduced phosphorylation of the MAP kinase ERK 1/2, but not JNK and p38 as shown both in vivo and in vitro. Lastly, both PAI-1 and SIRT5 gene expressions are increased in ACS patients compared to non-ACS controls after adjustment for cardiovascular risk factors, while PAI-1 expression increased across tertiles of SIRT5.

CONCLUSION

SIRT5 promotes arterial thrombosis by modulating fibrinolysis through endothelial PAI-1 expression. Hence, SIRT5 may be an interesting therapeutic target in the context of atherothrombotic events.

Effect of different carboxylated poly l-lysine and dimethyl sulfoxide combinations on post thaw rabbit sperm functionality and fertility

Antifreeze proteins are biologically active substances which protect living organisms against freezing injuries. The effect of a synthetic antifreeze protein carboxylated poly l-lysine (CPLL) in the extender was evaluated in the presence of a conventional cryoprotective agent, dimethyl sulfoxide (Me₂SO), for freezing rabbit sperm cells. The experiment was conducted according to 2 × 3 factorial design including two Me₂SO (5 or 8%) and three CPLL (0, 0.5 or 1%) concentrations. CPLL supplementation improved post-thaw live and live-acrosome intact sperm rates (P<0.01) without a prominent influence on the motility (P>0.05) and live-membrane intact (P>0.05) sperm rates. The most striking effect of CPLL supplementation was seen on the DNA integrity where it reduced DNA fragmentation of sperm cells significantly by interacting Me₂SO (P < 0.01) during freezing and thawing. However, it could not replace Me₂SO in the extender and did not improve pregnancy rate. In conclusion, CPLL supplementation to the extender in the presence of Me₂SO improved sperm quality parameters and post-thaw DNA integrity.

Platelets function as an acute viral reservoir during HIV-1 infection by harboring virus and T-cell complex formation

Platelets were recently found to harbor infectious HIV virions in infected individuals who are on antiretroviral treatment with poor CD4+ T-cell recovery. In this study, we screened platelets from recently infected individuals, before and after antiretroviral therapy, for the presence of virus and examined platelet activation, as well as CD4+ T-cell recovery. This was followed by in vitro studies assessing platelet-CD4+ T-cell complex formation as a contributing factor to viral transmission. HIV+ platelets were detected in 10 of 10 acutely infected individuals with no prior history of antiretroviral therapy. The percentage of HIV+ platelets dropped significantly after 3 months of antiretroviral therapy in all of the study participants. These individuals also demonstrated significant recovery of CD4+ T cells. Interestingly, the percentage of HIV+ platelets correlated positively with viral load but not with CD4+ T-cell count. Furthermore, we found that platelet activation with soluble CD40L or thrombin receptor activator peptide 6 (TRAP6) increased platelet-virus interactions in vitro. TRAP6-mediated interactions were reduced by platelet antagonists, aspirin, and R406. We demonstrated that platelets transmit the virus to CD4+ T cells, and this transinfection was abolished by inhibiting platelet-T-cell complex formation via exposure to an anti-CD62P antibody. Additionally, treatment with TRAP6 significantly increased the transinfection, which was also inhibited by aspirin and R206. These results reveal that platelets have the potential to promote HIV viral spread during the acute stage of infection, by harboring infectious virus transmitting infection to susceptible CD4+ T cells through complex formation.

Historical control data for hematology parameters obtained from toxicity studies performed on different Wistar rat strains: Acceptable value ranges, definition of severity degrees, and vehicle effects

The physiological and health status of control animals may vary. Due to this variation, it is important to define acceptable ranges of control hematology parameters to gain a better understanding of adverse and non-adverse effects of test substances. After generating historical control data for two Wistar rat strains (RccHan™:WIST and Crl:WI(Han)) from different breeders, the data sets were statistically analyzed using Minitab®. After noticing that single outliers can affect the study control data set, the respective outliers were verified relative to the available histopathology findings, for example, inflammatory pulmonary lesions following vehicle aspiration or spontaneous sperm granuloma affecting the health status and hematology data of the respective animals. Such data points were excluded from the control data set. Comparing both data sets, it was obvious that different blood sampling and anesthesia methods as well as strain differences may result in slightly different values. After excluding the outliers, a data set from animals with presumably good health status was generated to define acceptable ranges and severity degrees. To evaluate effects, possibly influencing hematology parameters and defined acceptable ranges, selected vehicles and different study types were observed.

Prospective Determination of Aspirin Sensitivity in Patients Resistant to Low Dose Aspirin: A Proof of Concept Study

This study tested the capability of an assay to predict aspirin response and reduce ischemic events, and healthcare costs, and delays to optimal treatment. Patients who needed aspirin in the course of normal medical care were included. Patients were excluded if they had disorders affecting platelet function, alcohol use within 24 hours of a test, or NSAID use. Dose escalation of chewable aspirin from 81 mg, to 162 mg, to 325 mg daily occurred based on the results of whole blood impedance aggregation testing to the agonists, collagen (1ug/mL, 5 ug/mL) and arachidonate (0.5 mM) after 10-14 days of treatment. The experimental in vitro test was conducted in triplicate by performing aggregometry on samples spiked to a concentration of 10 uM of aspirin in 0.05% dimethyl sulfoxide. Of the 36 patients who were compliant 16 were found to be resistant to the antiplatelet effects of 81 mg daily aspirin. Nine of these patients were predicted to stay resistant despite dose increase. Once tested at higher doses, ten remained resistant. Seven of the 16 patients were predicted to become sensitive to a higher dose while six actually did. Predicted response to increased doses of aspirin was in good agreement with actual response. Sensitivity of the assay was 83% and specificity was 80%. Results are promising and indicate that it is possible to predict, with reasonable accuracy, if a patient will have an adequate platelet response to aspirin or if the patient will never respond to aspirin necessitating an alternative antiplatelet regimen. Larger, multisite studies are inevitably needed.

The off-label use of drugs for parenteral nutrition as a solvent of substances slightly soluble in water in pharmacological research

Because of the problem to evaluate biological activity in water-soluble substances in all phases of preclinical and clinical studies, the research work enabled to develop the original solvent for poorly soluble compounds based on substances for parenteral nutrition. The main aim is to examine the impact of the original solvent based on substances for parenteral nutrition on biological systems exemplified by the hemostatic system, characterized by sensitivity and variability of the effects in response to any impact, and its comparison with the solvents that are conventional in pharmacological research. Experimental work is performed according to the “guidance on preclinical research of new pharmacological substances” in vitro. The findings show that traditional solvents at low dosages affect all the researched indicators of the hemostasis system. The smallest effect in respect of the hemostatic system was characterized by ethanol, and the most apparent antiaggregational effect was registered with dioxane. 10% concentration of original blend of lipids made no effect on hemostasis system. Thus, according to their own findings and experience in application of lipid emulsions as substances of parenteral nutrition, they can be considered to be an adequate solvent in all phases of preclinical and clinical studies of new drugs.

Proteomic Analysis of Human Adipose Derived Stem Cells during Small Molecule Chemical Stimulated Pre-neuronal Differentiation

Background

Adipose derived stem cells (ADSCs) are acquired from abdominal liposuction yielding a thousand fold more stem cells per millilitre than those from bone marrow. A large research void exists as to whether ADSCs are capable of transdermal differentiation toward neuronal phenotypes. Previous studies have investigated the use of chemical cocktails with varying inconclusive results.

Methods

Human ADSCs were treated with a chemical stimulant, beta-mercaptoethanol, to direct them toward a neuronal-like lineage within 24 hours. Quantitative proteomics using iTRAQ was then performed to ascertain protein abundance differences between ADSCs, beta-mercaptoethanol treated ADSCs and a glioblastoma cell line.

Results

The soluble proteome of ADSCs differentiated for 12 hours and 24 hours was significantly different from basal ADSCs and control cells, expressing a number of remodeling, neuroprotective and neuroproliferative proteins. However toward the later time point presented stress and shock related proteins were observed to be up regulated with a large down regulation of structural proteins. Cytokine profiles support a large cellular remodeling shift as well indicating cellular distress.

Conclusion

The earlier time point indicates an initiation of differentiation. At the latter time point there is a vast loss of cell population during treatment. At 24 hours drastically decreased cytokine profiles and overexpression of stress proteins reveal that exposure to beta-mercaptoethanol beyond 24 hours may not be suitable for clinical application as our results indicate that the cells are in trauma whilst producing neuronal-like morphologies. The shorter treatment time is promising, indicating a reducing agent has fast acting potential to initiate neuronal differentiation of ADSCs.

Attenuation of Multiple Organ Damage by Continuous Low-Dose Solvent-Free Infusions of Resveratrol after Severe Hemorrhagic Shock in Rats

Therapeutic effects of continuous intravenous infusions of solvent-free low doses of resveratrol on organ injury and systemic consequences resulting from severe hemorrhagic shock in rats were studied. Hemorrhagic shock was induced by withdrawing arterial blood until a mean arterial blood pressure (MAP) of 25-30 mmHg was reached. Following a shock phase of 60 min, rats were resuscitated with the withdrawn blood plus lactated Ringer's. Resveratrol (20 or 60 μg/kg × h) was continuously infused intravenously starting with the resuscitation phase (30 min) and continued until the end of the experiment (total treatment time 180 min). Animals of the shock control group received 0.9% NaCl solution. After the observation phase (150 min), rats were sacrificed. Resveratrol significantly stabilized the MAP and peripheral oxygen saturation after hemorrhagic shock, decreased the macroscopic injury of the small intestine, significantly attenuated the shock-induced increase in tissue myeloperoxidase activity in the small intestine, liver, kidney and lung, and diminished tissue hemorrhages (particularly in the small intestine and liver) as well as the rate of hemolysis. Already very low doses of resveratrol, continuously infused during resuscitation after severe hemorrhagic shock, can significantly improve impaired systemic parameters and attenuate multiple organ damage in rats.

Antiplatelet and anti-proliferative action of disintegrin from Echis multisquamatis snake venom

Aim

To purify the platelet aggregation inhibitor from Echis multisquamatis snake venom (PAIEM) and characterize its effect on platelet aggregation and HeLa cell proliferation.

Methods

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) were used for PAIEM identification. Platelet aggregation in the presence of PAIEM was studied on aggregometer Solar-AP2110. The changes of shape and granularity of platelets in the presence of PAIEM were studied on flow cytometer COULTER EPICS XL, and degranulation of platelets was estimated using spectrofluorimetry. Indirect enzyme-linked immunosorbent assay was used for the determination of target of PAIEM on platelet surface. An assay based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to evaluate the effect of PAIEM on the proliferation of HeLa cells in cell culture.

Results

The molecular weight of the protein purified from Echis multisquamatis venom was 14.9 kDa. Half-maximal inhibitory concentration (IC₅₀) of PAIEM needed to inhibit adenosine diphosphate (ADP)-induced platelet aggregation was 7 μM. PAIEM did not affect thrombin- or ADP-induced platelet activation, but it did prevent binding of the anti-IIb antibody to glycoprotein IIb/IIIa (GPIIbIIIa)-receptor of adhered platelets and inhibited the viability of HeLa cells by 54%.

Conclusion

As a member of the disintegrin family, PAIEM inhibited platelet aggregation and cell proliferation possibly by blocking integrin-mediated interactions. However, it did not impair cellular signaling causing any changes in platelet shape and granularity and did not affect ADP-induced platelet degranulation. This disintegrin was shown to be a potent inhibitor of integrin-mediated cellular interactions including platelet aggregation or cancer cell proliferation.

Toxic effects of dimethyl sulfoxide on red blood cells, platelets, and vascular endothelial cells in vitro

Dimethyl sulfoxide (DMSO) is widely used in biological studies as a cryoprotective agent for cells and tissues, and also for cryopreserved platelets (PLTs). However, few data on the toxic effects of DMSO following intravenous infusion of cryopreserved PLTs are available. The aim of this study was to explore dose-related effects of DMSO on red blood cells (RBCs), PLTs and vascular endothelial cells in vitro. The results showed that DMSO treatments had significant effects on RBCs, affecting osmotic fragility and increasing hemolysis. Free hemoglobin (FHb) level of RBCs was 0.64 ± 0.19 g L^-1 after incubation for 6 h with 0.6% DMSO, and these levels were elevated compared with controls (0.09 ± 0.05 g L^-1). Aggregation of PLTs induced by adenosine diphosphate, thrombin (THR), and thrombin receptor activator peptide (TRAP) were inhibited by DMSO treatment because the THR generation capacity was reduced. The intensity of the cytosolic esterase-induced fluorescence response from carboxy dimethyl fluorescein diacetate (CMFDA) in PLTs was decreased about 29% ± 0.04% after treatment with DMSO. DMSO also inhibited the proliferation of the vascular endothelial cell line EAhy926 cells by blocking the G1 phase. Apoptosis of EAhy926 cells with 0.6% DMSO stimulation was increased threefold compared to controls. On the basis of these findings, it was concluded that DMSO was toxic to the hematologic system. This should be taken into account when assessing the infusion effects of cryopreserved PLTs or other blood products requiring DMSO as a vehicle, such as cryopreserved stem cells, in order to avoid adverse therapeutic effects.

Effects of atorvastatin on ADP-, arachidonic acid-, collagen-, and epinephrine-induced platelet aggregation

Objective

Atorvastatin reduces the incidence of cardiovascular events. However, the effects of atorvastatin on platelet aggregation are unknown.

Methods

Blood samples were obtained from 126 healthy volunteers. Prepared isolated platelet suspensions were adjusted with saline to three different concentrations of 100 × 10⁹, 300 × 10⁹, and 600 × 10⁹ platelets/L. Platelet samples were incubated with atorvastatin (10⁻⁷mol/L, 10⁻⁶mol/L or 10⁻⁵mol/L), and stimulated with ADP (10 µmol/L), arachidonic acid (0.5 mmol/L), collagen (2 µg/mL), and epinephrine (1 mg/mL). The maximal amplitude of aggregation and the curve slope were measured by electric impedance aggregometry.

Results

Atorvastatin inhibited platelet aggregation at moderate (300 × 10⁹/L) and high (600 × 10⁹/L) concentrations. However, an inhibitory effect of atorvastatin at low concentrations (100 × 10⁹/L) was not observed.

Conclusions

The study shows that atorvastatin inhibits platelet aggregation in vitro, and this inhibitory effect is related to platelet concentrations.

Cytoskeleton dynamics in drug-treated platelets

Platelet activation is a key process in blood clot formation. During activation, platelets go through both chemical and physical changes, including secretion of chemical messengers and cellular shape change. Platelet shape change is mediated by the two major cytoskeletal elements in platelets, the actin matrix and microtubule ring. Most studies to date have evaluated these structures qualitatively, whereas this paper aims to provide a quantitative method of examining changes in these structures by fluorescently labeling the element of interest and performing single cell image analysis. The method described herein tracks the diameter of the microtubule ring and the circumference of the actin matrix as they change over time. Platelets were incubated with a series of drugs that interact with tubulin or actin, and the platelets were observed for variation in shape change dynamics throughout the activation process. Differences in shape change mechanics due to drug incubation were observable in each case.

Cryopreserved stem cell products containing dimethyl sulfoxide lead to activation of the coagulation system without any impact on engraftment

BACKGROUND

Dimethyl sulfoxide (DMSO) is extensively used as a cryoprotectant in stem cell preservation. Little is known on direct hemostatic changes in recipients of hematopoietic stem cell transplantation (HSCT), immediately after DMSO administration. The objectives of the current study were to measure hemostatic changes during HSCT.

STUDY DESIGN AND METHODS

In this prospective analysis, changes in plasma biomarkers, platelets (PLTs), or endothelial cells (D-dimers, thrombin-antithrombin complex [TAT], microparticle activity as thrombin-generation potential [MPA], whole blood aggregation, von Willebrand factor) were measured before and immediately after HSCT. Furthermore, associations with clinical complications were recorded.

RESULTS

A total of 54 patients were included in the study. Mean MPA and TAT increased significantly immediately after HSCT, returning to baseline the day after the procedure (p<0.01). No significant differences in engraftment for neutrophils and PLTs were found in patients presenting a high increase of TAT or MPA compared with those presenting with a smaller increase. Patients with a high increase in TAT and MPA had received a greater number of total mononucleated cells (p<0.001) and higher transplant volumes (p=0.002).

CONCLUSIONS

Infusion of stem cells containing DMSO reversibly activated coagulation, measured as thrombin generation. This finding was not associated with acute adverse events and did not influence engraftment. Further studies are needed to compare variable DMSO concentrations as well as DMSO-free products, to better address the influence of DMSO on hemostasis.

Thrombin inhibitory activity of some polyphenolic compounds

Thrombin, also known as an active plasma coagulation factor II, belongs to the family of serine proteases and plays a crucial role in blood coagulation process. The process of thrombin generation is the central event of the hemostatic process and regulates blood coagulant activity. For this reason, thrombin inhibition is key to successful novel antithrombotic pharmacotherapy. The aim of our present study was to examine the effects of the well-known polyphenolic compounds on the activity of thrombin, by characterization of its interaction with selected polyphenols using different biochemical methods and biosensor BIAcore analyses. Only six compounds, cyanidin, quercetin, silybin, cyanin, (+)-catechin and (-)-epicatechin, of all examined in this study polyphenols caused the inhibition of thrombin amidolytic activity. But only three of the six compounds (cyanidin, quercetin and silybin) changed thrombin proteolytic activity. BIAcore analyses demonstrated that cyanidin and quercetin caused a strong response in the interaction with immobilized thrombin, while cyanin and (-)-epicatechin induced a low response. Lineweaver-Burk curves show that used polyphenol aglycones act as competitive thrombin inhibitors. Our results suggest that polyphenolic compounds might be potential structural bases and source to find and project nature-based, safe, orally bioavailable direct thrombin inhibitors.

Serine/threonine phosphatases regulate platelet αIIbβ3 integrin receptor outside-in signaling mechanisms and clot retraction

AIMS

We studied the role of serine/threonine phosphatases (PSTPs) on αIIbβ3 signaling and the potential selectivity of the level of PSTP inhibition with okadaic acid (OA) on αIIbβ3 signaling for regulation of platelet aggregation and clot retraction.

MAIN METHODS

We used washed platelets from normal donors and OA as inhibitor of PSTPs. Clot retraction was induced by 1U/mL of thrombin. Reorganized cytoskeleton was isolated from Triton X-100 lysed platelets. The presence of proteins incorporated to the cytoskeleton was assayed by immunoblotting with specific antibodies.

KEY FINDINGS

We found that both 100 and 500 nM OA blocked platelet mediated clot retraction. In contrast, only 500 nM OA inhibited thrombin-induced inside-out αIIbβ3 activation, platelet aggregation, and cytoskeletal reorganization. Among markers of αIIbβ3 outside-in signaling, 500 nM OA inhibited the incorporation to the cytoskeleton of syk, src, and FAK (Focal Adhesion Kinase) tyrosine kinases and the incorporation and phosphorylation at Tyr(759) of the β3 chain of αIIbβ3, while 100 nM OA only inhibited the FAK translocation and its tyrosine phosphorylation.

SIGNIFICANCE

The level of inhibition of PSTPs by low or high OA concentration (33% and 73% inhibition, respectively) in intact whole cells differentially regulates platelet aggregation and integrin signaling, but have a common effect in blocking clot retraction. The latter may be associated with the presence of phosphorylated FAK in the cytoskeleton. This study reveals a novel target for anti-platelet treatment to block clot retraction without affecting the platelet hemostatic function by a partial inhibition of PSTPs.

Antiplatelet agents can promote two-peaked thrombin generation in platelet rich plasma: mechanism and possible applications

BACKGROUND

Thrombin generation assay is a convenient and widely used method for analysis of the blood coagulation system status. Thrombin generation curve (TGC) is usually bell-shaped with a single peak, but there are exceptions. In particular, TGC in platelet-rich plasma (PRP) can sometimes have two peaks.

OBJECTIVE

We sought to understand the mechanism underlying the occurrence of two peaks in the PRP thrombin generation curve.

METHODS

Tissue factor-induced thrombin generation in PRP and platelet-poor plasma (PPP) was monitored using continuous measurement of the hydrolysis rate of the thrombin-specific fluorogenic substrate Z-Gly-Gly-Arg-AMC. Expression of phosphatidylserine (PS) and CD62P on the surface of activated platelets was measured by flow cytometry using corresponding fluorescently labeled markers.

RESULTS

The addition of the P(2)Y(12) receptor antagonist MeS-AMP (160 µM), 83 nM prostaglandin E(1) (PGE(1)), or 1.6% DMSO to PRP caused the appearance of two peaks in the TGC. The PS exposure after thrombin activation on washed platelets in a suspension supplemented with DMSO, PGE(1) or MeS-AMP was delayed, which could indicate mechanism of the second peak formation. Supplementation of PRP with 1.6% DMSO plus 830 nM PGE(1) mediated the disappearance of the second peak and decreased the amplitude of the first peak. Increasing the platelet concentration in the PRP promoted the consolidation of the two peaks into one.

CONCLUSIONS

Procoagulant tenase and prothrombinase complexes in PRP assemble on phospholipid surfaces containing PS of two types--plasma lipoproteins and the surface of activated platelets. Thrombin generation in the PRP can be two-peaked. The second peak appears in the presence of platelet antagonists as a result of delayed PS expression on platelets, which leads to delayed assembly of the membrane-dependent procoagulant complexes and a second wave of thrombin generation.

Reduction of platelet cytosolic phospholipase A2 activity by atorvastatin and simvastatin: biochemical regulatory mechanisms

Statins have demonstrated effects beyond reducing cholesterol level that may contribute to their clinical benefit, including effects on platelet biochemistry and function.

OBJECTIVES

To explore and compare the antiplatelet effect of two lipophilic statins (atorvastatin and simvastatin) and one hydrophilic statin (pravastatin) concerning: a) collagen-induced platelet aggregation and thromboxane A2 (TXA2) synthesis; b) the additive effect of statins on TXA2 synthesis in platelets treated with a submaximally effective concentration of aspirin and c) the biochemical mechanisms involved.

METHODS AND RESULTS

Washed human platelets were incubated with statins (1-20μM), and stimulated with collagen (1μg/ml) or arachidonic acid (AA) (200μM) and TXB2 was quantified by ELISA. Incubation with simvastatin or atorvastatin reduced (36.2% and 31.0%, respectively) collagen-induced TXB2 synthesis (p<0.05) and platelet aggregation (p<0.001), whereas pravastatin had no effects. Simultaneous incubation with a submaximally effective concentration of aspirin (1μM) and atorvastatin or simvastatin significantly increased the inhibition of TXB2 synthesis by aspirin by 4.4- and 4.1-fold, respectively. Statins did not affect AA-induced TXB2 synthesis, excluding an effect on COX-1/TXA2 synthase activities. Atorvastatin and simvastatin concentration-dependently inhibited the collagen-induced increase in cytosolic calcium and the kinetics of cPLA2 phosphorylation. Lipophilic statins reduced phosphorylation of both ERK1/2 and p38 MAPK, which regulate cPLA2 phosphorylation and calcium movement.

CONCLUSION

We report for the first time a direct downregulation by atorvastatin and simvastatin of platelet cPLA2 activity through effects on calcium and MAPK, which reduce collagen-induced TXA2 synthesis. These mechanisms might contribute to their beneficial effects, even in aspirin-treated patients.

Optimization of Multiplate(®) whole blood platelet aggregometry in the Beagle dog and Wistar rat for ex vivo drug toxicity testing

This study was performed to optimize and standardize the use of the Multiplate(®) whole blood impedance aggregometer in the Beagle dog and Wistar rat for use in a research laboratory environment. The anticoagulants citrate, heparin and hirudin were compared and platelet aggregation responses to ADP, collagen, arachidonic acid and Par-4 agonist were evaluated to determine their half maximal effective concentrations (EC(50)) in blood containing low concentrations of a drug solvent (0.1% DMSO). The results indicate that citrate anticoagulation is not suitable for Multiplate(®) whole blood aggregometry because of the presence of spontaneous aggregation. ADP and collagen were found to be appropriate agonists for both species, whereas in the Beagle dog Par-4 agonist failed to induce aggregation and arachidonic acid induced platelet aggregation showed a high interindividual variability. The agonists EC(50) calculated in hirudin blood were 2.70 μM ADP, 0.85 μg/ml collagen, 0.03 mM arachidonic acid and 165.7 μM Par-4 agonist in the Wistar rat, and 0.95 μM ADP and 0.23 μg/ml collagen in the Beagle dog.

Effects of slow, sustained, and rate-tunable nitric oxide donors on human aortic smooth muscle cells proliferation

Smooth muscle cell (SMC) proliferation has been accepted as a common event in the pathophysiology of vascular diseases, including atherogenesis and intimal hyperplasia. Delivery of the nitric oxide synthase (NOS) substrate l-arginine, pharmacological nitric oxide (NO) donors, NO gas or overexpression of NOS proteins can inhibit SMC proliferation and reduce the injury responses within the blood vessel wall. Although commercial development of NO donors that attempt to provide exogenous delivery of NO has accelerated over the last few years, none of the currently available products can provide controlled, sustained, time-tunable release of NO. Nitrosamine-based NO donors, prepared in our laboratory, present a unique and innovative alternative for possible treatments for long-term NO deficiency-related diseases, including atherosclerosis, asthma, erectile dysfunction, cancer, and neurodegenerative diseases. A family of secondary amines prepared via nucleophilic aromatic displacement reactions could be readily N-nitrosated to produce NO donors. NO release takes place in three distinct phases. During the initial phase, the release rate is extremely fast. In the second phase, the release is slower and the rate remains essentially the same during the final stage. These compounds inhibited up to 35% human aortic smooth muscle cell proliferation in a concentration-dependent manner.

Dimethyl sulfoxide and sodium bicarbonate in the treatment of refractory cancer pain

Pain is a major concern of cancer patients and a significant problem for therapy. Pain can become a predominant symptom in advanced cancers. In this open-label clinical study, the authors have treated 26 cancer patients who have been declared as terminal without the option of conventional treatment. These patients suffered from high levels of pain that was poorly managed by all available interventional approaches recommended by World Health Organization (WHO) guideline. The results indicate that intravenous infusion of dimethyl sulfoxide (DMSO) and sodium bicarbonate (SB) solution can be a viable, effective, and safe treatment for refractory pain in cancer patients. These patients had pain due to the disease progression and complication of chemotherapy and radiation. Moreover, the preliminary clinical outcome of 96-day follow-up suggests that the application of DMSO and SB solution intravenously could lead to better quality of life for patients with nontreatable terminal cancers. The data of this clinical observation indicates that further research and application of the DMSO and SB combination may help the development of an effective, safe, and inexpensive therapy to manage cancer pain.

Antiplatelet effects of Spatholobus suberectus via inhibition of the glycoprotein IIb/IIIa receptor

ETHNOPHARMACOLOGICAL RELEVANCE

The vine stem of Spatholobus suberectus is a widely used blood-activating and stasis-dispelling medicine for the treatment of diseases related to blood stasis syndrome in traditional medicine in Korea, Japan, and China.

AIM OF THE STUDY

To demonstrate the clinical effects of Spatholobus suberectus against blood stasis syndromes using in vitro and in vivo platelet aggregation studies and to investigate its exact mechanisms.

MATERIALS AND METHODS

We extracted vine stems of Spatholobus suberectus, using 95% EtOH (SSE) and investigated its antiplatelet activity on platelet aggregation induced by collagen and ADP in human platelet-rich plasma (PRP). For the mechanism study, a glycoprotein IIb/IIIa (GP IIb/IIIa) assay using flow cytometric analysis and a thromboxane A(2) (TXA(2)) assay were performed. In addition, we investigated the effects of SSE in a thromboembolic mouse model.

RESULTS

SSE significantly inhibited ADP- and collagen-induced platelet aggregation in human PRP concentration-dependently without affecting plasma clotting time. It also significantly inhibited fibrinogen binding to the GP IIb/IIIa receptor and partly inhibited the formation of TXA(2). In the in vivo study, oral administration of SSE dose-dependently suppressed the death of thromboembolism model mice induced by intravenous injection of collagen plus epinephrine.

CONCLUSIONS

SSE showed antiplatelet activity without anticoagulant effects mainly through the inhibition of fibrinogen binding to the GP IIb/IIIa receptor. Our current results support the clinical usage of SSE in the East Asian region treating atherothrombotic diseases and may represent a new natural source to develop antiplatelet agents.

Antithrombotic effects of ethanol extract of Crataegus orientalis in the carrageenan-induced mice tail thrombosis model

INTRODUCTION

Crataegus species (common name is Hawthorn) are medicinal plants, which have flavonoids, triterpene acids, proanthocyanidins, and organic acids as main constituents, used in the treatment of cardiovascular diseases. One of the main causes of multiple cardiovascular diseases is intravascular thrombosis and current agents, which are used for the treatment and prevention of thrombosis, have some side effects. Therefore, new antithrombotic and thrombolytic agents are still needed.

MATERIALS AND METHODS

Antithrombotic function of ethanol extract of Crataegus orientalis (COE) leaves was investigated in carrageenan-induced mice tail thrombosis model. Mice were injected with 40 μl (1%) carrageenan (Type I) dissolved in physiological saline by intraplantar administration in the right hind paw. After carrageenan injection, the extract was administered at the doses of 100, 200, and 300 mg/kg. Heparin was used as a positive control (10 and 100 IU). The length of tail-thrombosis was measured at 24th, 48th, and 72nd hours.

RESULTS AND CONCLUSION

100mg/kg COE and 10IU heparin were not significant when compared to control groups at the time interval (24-72 h) that results was obtained. At 24th hour, both 200 and 300 mg/kg of COE showed a significant antithrombotic activity (p<0.05 and p<0.01, respectively). However, 200 mg/kg COE lost its significance and there was a decrease in the significance values of 300 mg/kg COE (p<0.05) at 48 and 72 h. From these results, it was concluded that COE significantly inhibited carrageenan-induced mice tail thrombosis in vivo.