• Journal of Applied Biological Chemistry
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• v.64 no.3
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• pp.317-322
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• 2021

Among the different cardiovascular disorders (CVDs), the activation of platelets is a necessary step. Based on this knowledge, therapeutic treatments for CVDs that target the disruption of platelet activation are proving to be worthwhile. One such substance, a bioactive 6,7-dihydroxy derived from coumarin, is 6,7-Dihydroxy-2H-1-benzopyran-2-one (esculetin). This compound has demonstrated several pharmacological effects on CVDS as well as various other disorders including diabetes, obesity, and renal failure. In various reports, esculetin and its effect has been explored in experimental mouse models, human platelet activation, esculetin-inhibited collagen, and washed human platelets exhibiting aggregation via arachidonic acid. Yet, esculetin affected aggregation with agonists like U46619 or thrombin in no way. This study investigated esculetin and how it affected human platelet aggregation activated through U46619. Ultimately, we confirmed that esculetin had an effect on the aggregation of human platelets when induced from U46619 and clarified the mechanism. Esculetin interacts with the downregulation of both phosphoinositide 3-kinase/Akt and mitogen-activated protein kinases, important phosphoproteins that are involved in activating platelets and their signaling process. The effects of esculetin reduced TXA₂ production, phospholipase A₂ activation, and platelet secretion of intracellular granules (ATP/serotonin), ultimately causing inhibition of overall platelet aggregation. These results clearly define the effect of esculetin in inhibiting platelet activity and thrombus formation in humans.

• Biomedical Science Letters
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• v.21 no.2
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• pp.103-114
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• 2015

In this study, we investigated the effect of rice bran water extract fermented with Lactobacillus plantarum KCCM-12116 (RBLp) on ADP ($20{\mu}M$)-, collagen ($10{\mu}g/mL$)-, and thrombin (0.2 U/mL)-stimulated platelet aggregation. RBLp dose-dependently inhibited ADP-, collagen-, and thrombin-induced platelet aggregation, with $IC_{50}$ values of 501.1, 637.2, and > $2,000{\mu}g/mL$, respectively. The platelet aggregation induced by ADP plus RBLp ($750{\mu}g/mL$) was increased by the adenylate cyclase inhibitor, SQ22536, and the cAMP-dependent protein kinase (A-kinase) inhibitor, Rp-8-Br-cAMPS. Treatment with RBLp increased the phosphorylation of VASP ($Ser^{157}$), an A-kinase substrate, which was also inhibited by SQ22536 and Rp-8-Br-cAMPS. It is thought that the RBLp-induced increases in cAMP contributed to the phosphorylation of VASP ($Ser^{157}$), which in turn resulted in an inhibition of ADP-induced platelet aggregation, thereby indicating that RBLp has an antiplatelet effect via cAMP-dependent phosphorylation of VASP ($Ser^{157}$). Thus, RBLp may have therapeutic potential for the treatment (or prevention) of platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.455-461
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• 2023

Glycyrrhiza glabra is a well-known medicinal herb that grows in various parts of the world and glabridin is a major chemical compound that is found in the root extract of Glycyrrhiza glabra. Glabridin is a natural compound known to have antioxidant, anti-inflammatory, anti-atherogenic, anti-osteoporotic and skin-whitening. In this study, we investigated if glabridin inhibited platelet aggregation and thrombus formation. We observed that glabridin inhibited collagen-induced platelet aggregation and suppressed signal transduction molecules such as phosphatidylinositol-3 kinase (PI₃K), Akt, glycogen synthase kinase-3α/β (GSK-3α/β), SYK, cytosolic phospholipase A₂, and p38 expression. In addition, glabridin suppressed thromboxane A₂ generation and thrombin-induced clot retraction. Taken together, glabridin showed strong antiplatelet effects and may be used to block thrombosis- and platelet-mediated cardiovascular diseases.

• Biomedical Science Letters
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• v.15 no.4
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• pp.273-279
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• 2009

Cordycepin (3'-deoxyadenosine) is an adenosine analogue isolated from Cordyceps militaris, and it has been used as an anti-cancer and anti-inflammation ingredient in traditional Chinese medicine. We investigated the effects of cordycepin on human platelet aggregation induced by thapsigargin, and determined the cytosolic free $Ca^{2+}$ levels ($[Ca^{2+}]_i$), an aggregation-stimulating factor. Cordycepin significantly inhibited thapsigargin-induced platelet aggregation. Its inhibitory effect was continually sustained at the maximal aggregation concentration of thapsigargin. The thapsigargin-induced $[Ca^{2+}]_i$ were clearly reduced by cordycepin in the presence of exogenous $CaCl_2$ or extracellular $Ca^{2+}$-chelator (EDTA). These results suggest that cordycepin inhibited thapsigargin-induced $Ca^{2+}$-influx from extracellular domain and thapsigargin-induced $Ca^{2+}$-mobilization from intracellular $Ca^{2+}$ storage. Accordingly, our data demonstrated that cordycepin may have a beneficial effect on platelet aggregation-mediated thrombotic diseases by inhibiting a $[Ca^{2+}]_i$-elevation.

• Biomolecules & Therapeutics
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• v.22 no.3
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• pp.254-259
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• 2014

The pentacyclic triterpenoid ursolic acid (UA) and its isomer oleanolic acid (OA) are ubiquitous in food and plant medicine, and thus are easily exposed to the population through natural contact or intentional use. Although they have diverse health benefits, reported cardiovascular protective activity is contentious. In this study, the effect of UA and OA on platelet aggregation was examined on the basis that alteration of platelet activity is a potential process contributing to cardiovascular events. Treatment of UA enhanced platelet aggregation induced by thrombin or ADP, which was concentration-dependent in a range of $5-50{\mu}M$. Quite comparable results were obtained with OA, in which OA-treated platelets also exhibited an exaggerated response to either thrombin or ADP. UA treatment potentiated aggregation of whole blood, while OA failed to increase aggregation by thrombin. UA and OA did not affect plasma coagulation assessed by measuring prothrombin time and activated partial thromboplastin time. These results indicate that both UA and OA are capable of making platelets susceptible to aggregatory stimuli, and platelets rather than clotting factors are the primary target of them in proaggregatory activity. These compounds need to be used with caution, especially in the population with a predisposition to cardiovascular events.

• Toxicological Research
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• v.16 no.4
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• pp.311-315
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• 2000

Previous studies showed that benzoquinone derivatives inhibited platelet aggregation. but there is no information available on their cytotoxicity to platelets. 1n the present study. washed platelets isolated from rats were treated with 1.4-benzoquinone. a representative benzoquinone derivative. to examine its antiaggregating effect and cytotoxicity. 1.4-Benzoquinone significantly inhibited thrombin-induced platelet aggregation. Consistent with this finding. 1.4-benzoquinone suppressed cytosolic calcium increase induced by thrombin. To examine the cytotoxicity by 1 A-benzoquinone in platelets. turbidometry and lactate dehydrogenase release were measured. Treatment with 1.4-benzoquinone resulted in slight cytotoxicity (30% release at 60 min) to platelets. However. the cytotoxicity was not correlated with increase of cytosolic calcium levels in platelets. All these data suggested that 1.4-benzoquinone inhibited thrombin-induced platelet aggregation mediated by inhibition elf calcium level increase and that 1.4-benzoquinone reveals cytotoxicity to some extent without alteration of calcium level in platelets.

• Toxicological Research
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• v.13 no.3
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• pp.229-235
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• 1997

The elevation of intracellular calcium in various tissues due to oxidative stress induced by either menadione or adriamycin has been well documented. The increase of calcium level in platelets results in aggregation of platelets. To test the hypothesis that chemically induced calcium elevations can play a role in platelet aggregation, we have studied the effects of menadione and adriamycin on aggregation of platelets isolated from female rats. Treatment with menadione and adriamycin to platelet rich plasma (PRP) appeared to induce platelet aggregations up to 60%, as determined by aggregometry. However, exposure of PRP to rnenadione or adriamycin led to a loss of viability, as measured by lactate dehydrogenase (LDH) leakage. Morphological studies of platelets revealed that, when PRP was treated with menadione, aggregates of platelets were not observed and the numbers of platelets were decreased significantly. This suggests that menadione and adriamycin decreased turbidity by inducing platelet lysis rather than platelet aggregation. These cellular toxicities induced by menadione or adriamycin was not correlated with oxygen consumption rate but with depletion of protein thiols, suggesting that protein thiols might play an important role in chemical-induced platelet toxicity.

• Korean Journal of Pharmacognosy
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• v.51 no.2
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• pp.100-106
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• 2020

The extract of Cudrania tricuspidata is used in ethnomedicine throughout Eastern Asia in China, Korea and Japan. In Korean traditional medicine, Cudrania tricuspidata has been used to treat eczema, mumps, tuberculosis, contusions, insomnia and acute arthritis. In addition, it has been reported that root extract of Cudrania tricuspidata has anti-platelet effects. Therefore, we investigated which compound in Cudrania tricuspidata has inhibitory effect on platelet aggregation. In this study, we tried to explain the inhibitory mechanism of steppogenin from Cudrania tricuspidata on human platelet aggregation. Collagen-induced human platelet aggregation and [Ca²⁺]_i mobilization were dose-dependently inhibited by steppogenin and we determined the inhibition by steppogenin is due to the down regulation of extracellular-signal-regulated kinase(ERK) and inositol-1,4,5-triphosphate receptor type I(IP₃RI) phosphorylation. In addition, steppogenin inhibited collagen-induced fibronectin adhesion to αIIb/β3 and thromboxane A₂ generation. Thus, in the present study, steppogenin showed an inhibitory effect on human platelet aggregation, suggesting its potential use for preventing platelet-induced cardiovascular disease.

• Archives of Pharmacal Research
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• v.14 no.4
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• pp.352-356
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• 1991

The anti-platelet activity of ilexoside D isolated from the roots of Ilex pubescens Hook. et Arn. was investigated in in vitro and ex 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 $A_2$ during platelet aggregation. These results suggest that the anti-platelet activity of ilexoside D may not be responsible for prostaglandin synthesis in platelets.

• Korean Journal of Veterinary Research
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• v.36 no.4
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• pp.873-886
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• 1996

For better understanding the interrelationship of hemorrhage and aggregation mechanism, cyclopiazonic acid(CPA) known as promoting the aggregation of platelet, aflatoxin $B_1(AFB_1)$ inhibiting platelet aggregation were used as toxic mycotoxins in these studies. In order to investigate the potential role of prostaglandin metabolism on the platelet aggregation, a variety of prostaglandin metabolites such as $PGF_{2{\alpha}}$, $PGE_2$ and $TXB_2$ were measured in homogenized rabbit platelets by TLC and LSC. And the role of $Ca^{{+}{+}}$ on the platelet aggregation was investigated by flow cytometer. Finally, the morphological effects of mycotoxins on platelet were determined by transmission electron microscope. The results and conclusions obtained from these studies are: 1) CPA induced no changes but $AFB_1$ increased $PGE_2$ and $TXB_2$. 2) CPA promoted ADP, collagen, thrombin, A.A., and PAF-induced $Ca^{{+}{+}}$ release. $AFB_1$, however, decreased $Ca^{{+}{+}}$ level except collagen-induced $Ca^{{+}{+}}$ release. When the calcium blocker, verapamil, was used, CPA decreased thrombin-induced $Ca^{{+}{+}}$ release and increased collagen, ADP, PAF and A.A.-induced $Ca^{{+}{+}}$ release. $AFB_1$ in contrast decreased the all factors induced $Ca^{{+}{+}}$ release. 3) $AFB_1$ did not induce any ultrastructural changes except large vacuole formation in a few platelets. And CPA also did not induce any changes except moderate shape change, indicator of platelet activation. In conclusion, CPA promoted platelet aggregation by the increases of $Ca^{{+}{+}}$ release but had no changes in A.A. metabolites. Antiaggregating effects of $AFB_1$ may be due to decreases of $Ca^{{+}{+}}$ release and increases of $PGE_2$ and $PGF_{2{\alpha}}$ formation. These data provide the basis for the future study of mobilization and function of $Ca^{{+}{+}}$ in platelet aggregation.