The suppressive effect of pyrrole-2-carboxylic acid on platelet aggregation

In the course of a search for novel antibiotics, an antiplatelet substance was isolated from the fermentation broth of Streptomyces sp. No. 82-85. Thereafter, the active substance was identified as pyrrole-2-carboxylic acid (P2C) by structural studies. The effects of P2C on adenosine diphosphate (ADP)-, arachidonic acid-, collagen- or tumor cell-induced platelet aggregation were examined in vitro and ex vivo. In in vitro studies, P2C (25-100 micrograms/ml) suppressed the aggregation of platelets of normal Wistar rats. The intraperitoneal administration of P2C (200 mg/kg) to rats and rabbits suppressed platelet aggregation induced by ADP, arachidonic acid and collagen when examined for 0.5-3 hours after administration. The agent also suppressed platelet aggregation induced by both mouse syngenic tumors, Meth-A fibrosarcoma and IMC carcinoma in vitro.     

The mechanism of anti-platelet activity of davallialactone: involvement of intracellular calcium ions, extracellular signal-regulated kinase 2 and p38 mitogen-activated protein kinase

This study was designed to investigate the effect of davallialactone, which was isolated from the mushroom Inonotus xeranticus, on platelet aggregation induced by collagen, thrombin and ADP. We found that davallialactone dose-dependently inhibited platelet aggregation that was stimulated either by collagen (2.5 microg/ml), a potent ligand of integrin alpha2beta1 and glycoprotein VI, or by thrombin (0.1U/ml), a potent agonist of the protease-activated receptors (PARs) PAR1 and PAR3. In addition, davallialactone inhibited platelet aggregation induced by ADP, an agonist of P2Y receptor. To understand the mechanism of anti-platelet activity, we determined whether davallialactone affected the downstream signaling in collagen-activated platelets. Using the fura-2/AM fluorometric assay, we found that davallialactone dose-dependently inhibited intracellular calcium concentration levels ([Ca2+]i). Moreover, davallialactone inhibited the phosphorylation of extracellular signal-regulated protein kinase (ERK)-2 and p38 mitogen-activated protein kinase (MAPK), in a dose-dependent manner. The tyrosine phosphorylation of 60 and 85kDa proteins, which were activated by collagen, were differentially inhibited by davallialactone. Taken together, these data suggest that davallialactone may have potential anti-platelet aggregation activity via suppression of intracellular downstream signaling pathways.     

山茱萸环烯醚萜苷对家兔、大鼠血小板聚集及出血时间的影响

目的：研究山茱萸环烯醚萜苷（CIG）对血小板聚集和出血时间的影响。方法：应用比浊法测定家兔（体外实验）及血瘀模型大鼠（体内实验）的血小板聚集率;断尾法观察大鼠出血时间。采用肾上腺素加冰水刺激法制备血瘀大鼠模型。结果：在体外实验中,CIG（0.75～3 mg/mL）能明显抑制二磷酸腺苷（ADP）或花生四烯酸（AA）诱导的家兔血小板聚集（P〈0.05,P〈0.01）,对血小板活化因子（PAF）诱导的血小板聚集无显著影响,但更大剂量（6～12 mg/mL）能抑制PAF诱导的血小板聚集（P〈0.01）。在体内实验中,CIG大剂量（180 mg/kg）灌胃给药能显著抑制ADP诱导的血瘀模型大鼠血小板聚集（P〈0.01）,延长正常大鼠的出血时间（P〈0.05）。结论：山茱萸环烯醚萜苷具有抗血小板聚集作用,大剂量能够延长出血时间。     

香草酸抗血小板聚集作用的体内外研究

目的香草酸是一种酚酸类化合物,具有抗氧化、抗炎等药理作用,其抗血栓作用尚未有报道。本实验室前期通过筛选发现香草酸具有良好的抗血小板聚集作用,因此本研究通过体内外实验对香草酸抗血小板聚集的作用进行系统评价。方法采用花生四烯酸(arachidonic acid,AA)、二磷酸腺苷(adenosine diphosphate,ADP)、凝血酶(thrombin,THR)诱导体内外血小板聚集模型,结合凝血四项检测评价香草酸抗血小板聚集及抗血栓的作用。结果体外实验中,香草酸对ADP和AA诱导的血小板聚集具有显著抑制作用,并剂量依赖性抑制ADP诱导的血小板聚集;体内试验中,香草酸(10、30和100 mg/kg)能够剂量依赖性抑制ADP和AA诱导的血小板聚集;同时,香草酸(100 mg/kg)能显著降低纤维蛋白原、增加凝血酶原时间,对活化部分凝血活酶时间和血浆凝血酶时间无明显影响。结论本研究首次发现香草酸对ADP和AA诱导的血小板聚集具有抑制作用,为研发具有自主知识产权的抗血小板聚集药物提供了实验依据。     

Pharmacological properties of the novel anti-platelet aggregating agent 4-cyano-5,5-bis(4-methoxyphenyl)-4-pentenoic acid

Various pharmacological properties of a new antiplatelet aggregating agent, 4-cyano-5,5-bis(4-methoxyphenyl)-4-pentenoic acid (E-5510), were examined in order to elucidate its mode of action, Firstly, the inhibitory effect on in vitro aggregation of platelets from humans and various experimental animals was studied. E-5510 inhibited human platelet aggregation induced by collagen, arachidonic acid, adenosine diphosphate (ADP), platelet activating factor (PAF) and epinephrine. Thrombin-induced platelet aggregation, which was not inhibited by acetylsalicylic acid (ASA) or the thiazole drug, 4,5-bis(4-methoxyphenyl)-2-(trifluoromethyl) thiazole, was inhibited by E-5510. E-5510 inhibited collagen-induced platelet aggregation in platelet-rich plasma (PRP) from guinea pigs, beagle dogs and monkey to the same degree as in human PRP, but its effect was weaker in rat PRP. Human platelet adhesion to a collagen-coated plastic disk and thrombin-induced adenosine triphosphate (ATP) release from human platelets were also inhibited by this compound. Next, the ex vivo anti-platelet effect of E-5510 was examined in guinea pigs and beagle dogs. E-5510 was the most potent among the tested drugs (ticlopidine, ASA, cilostazol and the thiazole drug. The anti-platelet effect of this compound appeared within 1 h and lasted more than 8 h after oral administration. The above results suggest that E-5510 may antagonize platelet activation by inhibiting phospholipase C and/or A2, which results in suppression of both phosphatidylinositol breakdown and arachidonic acid release from phospholipids, as well as by inhibiting cyclooxygenase. E-5510 exerted its anti-platelet action without affecting prostaglandin I2 production in the blood vessels. It is considered that E-5510 has a highly potent anti-platelet aggregating effect and a unique multi-site mode of action. This compound is a promising candidate as an antithrombotic drug for clinical use.     

Cicaprost, an orally active prostacyclin analogue: its effects on platelet aggregation and skin blood flow in normal volunteers.

1. Prostacyclin (PGI2) and its analogues may be useful in peripheral vascular disease. However, most have to be given intravenously due to their metabolic instability. 2. We have investigated the pharmacological effects of cicaprost, a synthetic PGI2 analogue which is metabolically stable and bioavailable after oral administration, in eight healthy male volunteers. 3. This was a double-blind, placebo-controlled, cross-over study. The volunteers were given either placebo, 5 micrograms, 7.5 micrograms or 10 micrograms cicaprost (at 09.00 h, 14.00 h, 19.00 h and again at 09.00 h the following day) on four separate occasions each 14 days apart. 4. Platelet aggregation induced by collagen and ADP in platelet rich plasma (PRP) and whole blood were measured prior to and 1 h after the trial medication. Laser Doppler flowmetry measured skin blood flow on the face before and after medication. 5. There was a statistically significant dose relationship in the inhibition of platelet aggregation induced by 2 microM ADP and 0.4 microgram ml-1 collagen in PRP and 2 microM ADP and 0.6 microgram ml-1 collagen in whole blood by cicaprost (P = 0.008, P = 0.34, P = 0.011 and P = 0.036, respectively). The threshold dose was 7.5 micrograms. Attenuation of anti-platelet effects was seen with the 14.00 h and 19.00 h doses. This may be due to a decrease in absorption after meals or to the development of tachyphylaxis. 6. Similar dose dependent effects of cicaprost on skin blood flow were also found (P = 0.01 and P = 0.006 for maximum output signal and red blood cell flux, respectively). The threshold dose was 7.5 micrograms. 7. In conclusion, cicaprost has significant anti-platelet and vasodilatory effects when given in doses of 7.5 micrograms and 10 micrograms three times a day in healthy male volunteers.     

Components of traditional Chinese medicine inhibit platelet aggregation by blocking ADP receptor subtypes P2Y_1 and P2Y_(12)

Platelets aggregation and thrombosis formation are major reasons of cardiovascular and cerebral vascular diseases.To develop new generative,potent and safe agents for inhibiting platelet aggregation and preventing above diseases are urgently required.Some traditional Chinese medicines of″Houxue Huayu″have been shown to inhibit platelet aggregation potently.In the present study the mechanisms and the molecular targets of puerarin,salvianolic acid B and the analogue of 3-n-butylphthalide,dl-PHPB were investigated and compared with ticlopidine.Four platelet aggregation inducers,ADP,arachidonic acid,collagen and thrombin were used in the study.It was found that puerarin and dl-PHPB specifically inhibited ADP induced platelet aggregation like ticlopidine did.However,salvianolic acid B inhibited both ADP and collagen induced platelet aggregations with similar potency.Due to existing two ADP receptor subtypes on platelets,P2Y1 and P2Y12,we studied the action of above compounds on the receptors and the signaling pathways.It was found that dl-PHPB decreased IP1 accumulation produced by ADP,but had no effect on IP1 level induced by m-3M3 FBS,an activator of PLC.M-3M3 FBS might attenuate the inhibitory effect of dl-PHPB on ADP-induced platelet aggregation.In addition,dl-PHPB did not affect cyclic AMP formation in platelets by ADP,which is different from P2Y12 antagonist ticlopidine.Puerarin showed the similar effects of dl-PHPB.Therefore,the actions of dl-PHPB and puerarin might be through P2Y1receptor-PLC-βpathway.Salvianolic acid B did not reduce the IP1 accumulation stimulated by ADP.It might act on the receptor subtype P2Y12.Our results suggest that components of Chinese herb medicine might be a resource for development of novel anti-platelet drugs.     

烟酰水杨酸对Collagen、ADP、AA诱导的兔血小板聚集的影响

目的观察烟酰水杨酸(NSA)对Collagen、ADP、AA诱导的兔血小板聚集的影响。方法用比浊法测定了NSA体外、体内对兔血小板聚集的影响。结果NSA能明显抑制体外、体内Collagen、ADP诱导的血小板聚集,体外最大抑制率分别为55.7%、61.3%,体内最大抑制率分别为42.2%、74.8%。NSA对AA诱导的兔血小板聚集没有影响。结论NSA具有抑制Collagen、ADP诱导的血小板聚集的作用。其抑制作用具有明显的量效关系。     

Effects of propranolol in vitro and in vivo on platelet function and thromboxane formation in normal volunteers

In vitro and ex vivo effects of propranolol on platelet aggregation, formation of thromboxane B2 (TXB2) and platelet sensitivity to prostacyclin were studied in healthy men. Propranolol, added in vitro to platelet rich plasma (PRP) inhibited platelet aggregation and TXB2 formation induced by ADP, 1-epinephrine, collagen and arachidonic acid. Concentrations of 20-100 microM propranolol were effective when ADP, 1-epinephrine and collagen were used as stimuli. Higher concentrations (250-500 microM) were needed to inhibit aggregation induced by arachidonic acid. Oral administration of propranolol either as a single dose (120 mg) or for one week (3 x 40 mg/day) did, however, not affect platelet aggregation, thromboxane formation and platelet sensitivity to prostacyclin. In addition, withdrawal of propranolol was without effect on these parameters. Although propranolol has potent effects on platelet function in vitro, it seems that the blood levels achievable by oral administration of propranolol are too low to affect platelet aggregation and TXB2 formation.     

PAF-induced platelet aggregation ex vivo as a method for monitoring pharmacological activity in healthy volunteers

Platelet aggregation induced ex vivo by aggregating factors such as adrenaline, ADP, collagen or PAF may be useful as a model for describing drug effects in humans. In the two studies reported here, PAF-induced platelet aggregation ex vivo was used as an indicator of the pharmacological activity in healthy volunteers of the newly developed specific PAF-antagonist WEB 2086. In intravenous and inhalative single rising dose tolerance trials this method proved useful for monitoring the pharmacological action of the compound tested. After administration of placebo no relevant pharmacological activity was observed. In both studies increasing dosages of the test substance showed clear, dose-related inhibition of PAF-induced platelet aggregation. Ex vivo PAF-induced platelet aggregation thus provides a simple and rapid means of assessing functional PAF antagonism during trials of PAF-antagonists in human volunteers.     

银杏叶提取物制剂、阿司匹林及氯吡格雷抗血小板聚集作用比较及对血小板活化因子含量的影响

目的:观察银杏叶提取物(EGB)制剂、阿司匹林及氯吡格雷对家兔血小板聚集率及血小板活化因子(PAF)含量的影响。方法:采用体内实验,观察EGB制剂、阿司匹林及氯吡格雷对由花生四烯酸(AA)、二磷酸腺苷(ADP)和PAF诱导的家兔血小板聚集作用的影响,以及对给药前后家兔PAF含量的影响。结果:与生理盐水组比较,EGB制剂抑制AA、ADP、PAF诱导的家兔血小板聚集有统计学差异(P<0.05,P<0.01),并能够降低血清中PAF的含量(P<0.05),阿司匹林对AA诱导的血小板聚集有统计学差异(P<0.01),氯吡格雷对ADP诱导的血小板聚集有统计学差异(P<0.01),而阿司匹林和氯吡格雷对PAF的含量没有显著影响。结论:EGB制剂具有抗血小板聚集作用,抗PAF诱导的血小板聚集作用最强,并能显著降低PAF含量。     

Inhibition of platelet function by KB-2796]

The anti-platelet activity of KB-2796, 1-[bis(4-fluorophenyl)methyl]-4- (2,3,4-trimethoxybenzyl) piperazine dihydrochloride, was studied in guinea pigs and mice. When guinea pig platelet-rich plasma (PRP) was employed, platelet function was inhibited at high doses of KB-2796. The IC50 value for [3H]5-HT release was 940 microM, and the IC50 values for collagen- and ADP-induced platelet aggregation were 210 and 390 microM, respectively. Oral administration of KB-2796 at 10-100 mg/kg dose-dependently inhibited the transient thrombocytopenia induced by collagen, but not that caused by ADP. KB-2796 protected mice from death after intravenous injection of collagen plus epinephrine, with an ED50 value of 9.5 mg/kg, p.o. Oral administration of KB-2796 at 10-100 mg/kg dose-dependently reduced guinea pig platelet retention in glass bead columns and reduced the leakage of ADP and ATP from erythrocytes passing through similar columns. KB-2796, at a concentration of 1-10 microM, produced a stabilizing effect on guinea pig erythrocytes against hypotonic hemolysis. These results suggest that KB-2796 is an inhibitor of platelet function and that its inhibition is related mainly to the inhibition of leakage of ADP and ATP from erythrocytes.     

Antiplatelet action of ilexoside D,a triterpenoid saponin fromIlex pubescens

The anti-platelet activity of ilexoside D isolated from the roots ofIlex pubescens Hook. et Arn. was investigated inin vitro andex vivo models of platelet aggregation induced by ADP, thrombin or collagen in rats.In vitro ilexoside D inhibited more effectively platelet aggregation induced by ADP and thrombin than by collagen as compared with aspirin.Ex vivo ilexoside D also inhibited platelet aggregation induced by ADP and collagen, but not by thrombin, and the inhibitory action of ilexoside D was more effective than that of aspirin. However,in vitro ilexoside D inhibited very poorly the generation of malonyldialdehyde, which is known to be concomitantly released with thromboxane A₂ during platelet aggregation. These results suggest that the anti-platelet activity of ilexoside D may not be responsible for prostaglandin synthesis in platelets.     

Antiplatelet and antithrombotic activity of L-3-n-butylphthalide in rats

3-n-butylphthalide (NBP) is a potentially beneficial drug for the treatment of ischemic stroke with multiple actions on different pathophysiological processes. In the present study, the effect of l-, d-, and dl-NBP was investigated on ADP-, collagen-, and AA-induced platelet aggregation. l-NBP was the most potent among l-, d-, and dl-NBP. At higher concentration the effect of dl-NBP on platelet aggregation was greater than that of l- or d-NBP alone. The ex vivo antiaggregatory activity of l-NBP 100mg/kg declined gradually after 2 hours, but a considerable antiplatelet activity was still observed 4h after l-NBP administration. NBP was given orally and resulted in a dose-dependent inhibition of thrombus formation. Of the two isomers, l-NBP was the most potent. It significantly protected mice from a mixture of collagen and epinephrine induced thromboembolic death. When 100 mg/kg of l-NBP were administered orally to rats, the bleeding time increased 2.1-fold compared with the control group. At the same dose, ex vivo platelet aggregation induced by ADP, collagen, and AA was inhibited by l-NBP and the antithrombotic effects of the compound were also observed. Thus, NBP exerts oral anti-platelet and anti-thrombotic efficacy without perturbing systemic hemostasis in rats. l-NBP is more potent than d- and dl-NBP as antiplatelet agent.     

Comparative pharmacology of endothelium-derived relaxing factor, nitric oxide and prostacyclin in platelets

1 The pharmacological effects of endothelium-derived relaxing factor (EDRF), nitric oxide (NO) and prostacyclin on human and rabbit platelets were examined. 2 EDRF is released from porcine aortic endothelial cells, cultured on microcarriers and treated with indomethacin, in sufficient quantities to inhibit platelet aggregation induced by 9,11-dideoxy-9 alpha, 11 alpha-methano epoxy-prostaglandin F2 alpha (U46619) and collagen. 3 The anti-aggregating activity of EDRF was potentiated by M&B 22948, a selective inhibitor of cyclic GMP phosphodiesterase, and by superoxide dismutase (SOD) and was inhibited by haemoglobin and Fe2+. 4 Both NO and prostacyclin inhibited platelet aggregation. 5 The anti-aggregatory activity of NO, but not that of prostacyclin, was potentiated by M&B 22948 and by SOD and was inhibited by haemoglobin and Fe2+. Thus NO is a potent inhibitor of platelet aggregation whose activity on platelets mimics that of EDRF. 6 It is likely that the inhibitory effect of NO on platelets represents the action of endogenous EDRF and therefore this substance, together with prostacyclin, is a regulator of platelet-vessel wall interactions.     

Antiplatelet effects of piplartine,an alkamide isolated from Piper tuberculatum: possible involvement of cyclooxygenase blockade and antioxidant activity

Objectives Piplartine (piperlongumine; 5,6‐dihydro‐1‐[1‐oxo‐3‐(3,4,5‐trimethoxyphenyl]‐2(1H) pyridinone) is an alkaloid amide isolated from Piper species (Piperaceae). It has been reported to show multiple pharmacological activities in vitro and in vivo. Methods We evaluated the in‐vitro antiplatelet effect of piplartine isolated from the roots of P. tuberculatum, on human platelet aggregation induced in platelet‐rich plasma by the agonists collagen, adenosine 5′‐diphosphate (ADP), arachidonic acid (AA) and thrombin. Key findings Piplartine (100μg/ml) caused a 30% inhibition in platelet aggregation when collagen was the agonist. At 200 μg/ml, piplartine significantly inhibited the aggregation induced by arachidonic acid (100%), collagen (59%) or ADP (52%) but not that induced by thrombin. The highest concentration of piplartine (300 μg/ml) inhibited thrombin‐ (37%), ADP‐ (71%) and collagen‐ (98%) induced aggregation. The inhibitory effect of piplartine on ADP‐induced platelet aggregation was not modified by pretreatment with pentoxifylline (a phosphodiesterase inhibitor), l ‐arginine (a substrate for nitric oxide synthase) or ticlopidine (a P2Y₁₂ purinoceptor antagonist). However, aspirin, a well‐known inhibitor of cyclooxygenase, greatly increased the inhibitory effect of piplartine on arachidonic‐acid‐induced platelet aggregation. Conclusions The mechanism underlying the piplartine antiplatelet action is not totally clarified. It could be related to the inhibition of cyclooxgenase activity and a decrease in thromboxane A₂ formation, similar to that occurring with aspirin. This and other possible mechanisms require further study.     

Anti-thrombotic effects of higenamine

The anti-platelet and anti-thrombotic effects of higenamine, a benzyltetrahydroisoquinoline alkaloid of the roots of Aconitum japonicum (Ranunculaceae), were investigated. The degree of platelet aggregation was measured with platelet rich plasma (PRP). An acute thrombotic condition was induced in mice by the injection of the mixture of collagen and epinephrine. The thrombus formation was induced inside the arterio-venous shunt tube installed between an abdominal aorta and the renal vein of rats. Higenamine showed inhibitory activities to both human and rat platelet aggregation induced by ADP, collagen and epinephrine. It was more inhibitory to epinephrine induced aggregation (IC(50); 19 and 7.2 microM to human and rat platelets respectively) than ADP- or collagen-induced aggregation. The anti-thrombotic effects of higenamine were also observed in both mouse acute thrombosis model and rat arterio-venous shunt (AV-shunt) models. The oral administration of higenamine (50 or 100 mg/kg) increased the recovery rates from the acute thrombotic challenge in mice and lowered the weight of thrombus formed inside the AV-shunt tube in rats.     

乙酰丹酚酸A对血小板功能的影响

乙酰丹酚酸以A(ASAA)是丹参有效成分衍生物。体外实验表明,ASAA对ADP、胶原、AA和凝血酶诱导的大鼠和兔血小板聚集有明显抑制作用。在半体内实验中,ASAA对多种诱导剂所致血小板聚集也有显著抑制作用,且持续时间达2h以上。此外,在抑制血小板聚集的同时,ASAA对胶原诱导的血小板5-HT释放也有显著抑制作用。上述结果提示,ASAA可能是一作用广泛的血小板功能抑制剂。     

Antiaggregation effect of alum on human platelets

OBJECTIVE: The purpose of this study was to evaluate the effect of alum on human platelet aggregation. METHODS: Platelet-rich plasma fractions were prepared from fresh blood drawn from a group of healthy male volunteers. Platelet aggregation was induced by various inducers. The percent aggregation was recorded in the absence and presence of various concentrations of alum. RESULTS: Alum at concentrations less than 1.5 mg/ml inhibited platelet aggregation induced by collagen, epinephrine. ADP and thrombin in a dose-dependent manner. The IC50s were 0.668, 0.324, 0.250 and 0.191 mg/ml of alum, for collagen-, epinephrine-, ADP- and thrombin-induced platelet aggregation, respectively. In contrast, alum at concentrations up to 1.5 mg/ml did not inhibit ristocetin-induced platelet aggregation. CONCLUSION: Alum has an anti-platelet action and should be used cautiously in the treatment of intractable intravesical hemorrhage. Alum is a cheap anti-platelet drug that needs further investigation.     

Estimation of anti-platelet drugs on human platelet aggregation with a novel whole blood aggregometer by a screen filtration pressure method

1. The effects of anti-platelet drugs on human whole blood aggregation were evaluated using a novel whole blood aggregometer by a screen filtration pressure (SFP) method. 2. The SFP whole blood aggregometer was found to successfully detect whole blood aggregation induced by ADP, collagen and TRAP by measuring the SFP of blood samples. The platelet aggregation threshold index (PATI), the concentration of agonist required with an inducing pressure rate of 50%, varied time-dependently after collection of blood. High values for ADP and collagen were noted immediately after blood collection, suggesting low aggregation activity of platelets, and gradually increase thereafter. 3. Cilostazol (phosphodiesterase 3 inhibitor), dipyridamole, aspirin and tirofiban all inhibited whole blood aggregation in vitro. Inhibitory effects of cilostazol and dipyridamole, but not tirofiban, were markedly enhanced 6 or 7 fold by long pre-incubation (60 min), compared with short pre-incubation (2 min). Such enhancement was only observed with ADP- and not collagen-induced whole blood aggregation. A similar phenomenon was also observed for aggregation with platelet rich plasma (PRP). Cilostazol inhibition of ADP-induced platelet aggregation was more potent with PRP than whole blood (PATI(200)=3.80+/-0.95 microM for whole blood; 2.04+/-0.61 microM for PRP). Inhibitory effects of dipyridamole were attenuated in PRP without erythrocytes. 4. These results demonstrate that the SFP aggregometer can sensitively detect anti-platelet aggregatory effects of various kinds of drugs. So that it is a useful tool for evaluation of anti-platelet drugs.