Inhibitory Effects of Resveratrol on Platelet Activation Induced by Thromboxane A2Receptor Agonist in Human Platelets

2011 ◽  
Vol 39 (01) ◽  
pp. 145-159 ◽  
Author(s):  
Yumin Yang ◽  
Xiaoling Wang ◽  
Li Zhang ◽  
Huiping An ◽  
Zhigao Zao

Resveratrol (RSVL), a polyphenolic compound found in red wine is believed to be a contributor in decreasing the incidence of coronary heart disease. Although its primary target is unknown, it blocks platelet aggregation by an ill-defined mechanism. Protein kinase C (PKC), which would redistribute from the cytosol to the platelet membrane upon platelet stimulation, plays a key role in the signal transduction system of platelets in human. In this study, we investigated the effect of RSVL and a PKC inhibitor (DL-erythro-1,3-Dihydroxy-2-aminooctadecane, PKCI) on platelet aggregation induced by a thromboxane A2receptor agonist (U46619, 9,11-Dideoxy-11α, 9α-epoxymethanoprostaglandin F2α) using a platelet aggregometer. We also studied the platelet membranebound fibrinogen (PFig) content and the activity of protein kinase C (PKC) in platelets from healthy volunteers using flow cytometry, and a phosphorimaging system, respectively. Our results showed that RSVL blocked platelet aggregation and PFig content induced by U46619 in a concentration-dependent manner. PKCI and RSVL had an additive effect in inhibiting platelet aggregation and PFig content. Furthermore, RSVL (final concentration 50 μM) remarkably depressed the activity of PKC in the membrane of platelets and the percentage of membrane PKC activity in total PKC activity. Taken together, these results suggested that RSVL suppressed U46619-induced platelet aggregation and PFig content partially through the inhibition of the activity of PKC in platelets.

2008 ◽  
Vol 36 (03) ◽  
pp. 603-613 ◽  
Author(s):  
Yu-Min Yang ◽  
Xing-Xiang Wang ◽  
Jun-Zhu Chen ◽  
Shi-Jun Wang ◽  
Hu Hu ◽  
...  

Inappropriate platelet activation is the key point of thrombogenesis. The aim of the present study was to investigate the effects of resveratrol (RESV), a compound extracted from the Chinese medicinal herb Polygonum cuspidatum sieb et Zucc, on the platelet activation induced by adenosine diphosphate (ADP) and its possible mechanism. The percentage of platelet aggregation and surface P-selectin-positive platelets, and the activity of protein kinase C (PKC) of platelet were observed with platelet aggregometer, flow cytometry and phosphorimaging system, respectively. RESV at 25, 50 and 100 μM showed anti-platelet aggregation and inhibition of surface P-selectin-positive platelets in a concentration-dependent manner. RESV (50 μM) inhibited the activity of PKC in the membrane fraction of platelets and decreased the percentage of membrane associated PKC activity in total PKC activity. Moreover, DL-erythro-1,3-Dihydroxy-2-aminooctadecane, an elective protein kinase C inhibitor (PKCI), and RESV had additive effects of inhibiting the percentage of platelet aggregation and surface P-selectin-positive platelets. It is suggested that RESV may inhibit platelet aggregation, the percentage of surface P-selectin-positive platelets and subsequent thrombus formation. The mechanisms may be partly relative to the decrease of the activity of PKC of platelets.


1993 ◽  
Vol 295 (1) ◽  
pp. 321-327 ◽  
Author(s):  
F N Ko ◽  
Y L Chang ◽  
Y H Kuo ◽  
Y L Lin ◽  
C M Teng

Daphnoretin, a biologically active principle isolated from Wikstroemia indica C.A. Mey., caused platelet aggregation in washed rabbit platelets, platelet-rich plasma and whole blood. The aggregation of and ATP release from platelets induced by daphnoretin were similar to phorbol ester- and diacylglycerol-induced aggregation and release. The EC50 values of daphnoretin-, phorbol 12,13-dibutyrate (PDBu)- and 1-oleoyl-2-acetylglycerol (OAG)-induced platelet aggregation in washed rabbit platelets were 17.2 +/- 2.8 microM, 20.6 +/- 2.1 nM and 38.6 +/- 1.7 microM respectively. Platelet aggregation induced by daphnoretin and PDBu was not inhibited by indomethacin, BN52021 or sodium nitroprusside. ADP-scavenging systems, apyrase and phosphocreatine/creatine kinase, showed weak inhibition of the aggregation, and EGTA, triflavin, verapamil and prostaglandin E1 markedly inhibited the aggregation. Staurosporine, a potent protein kinase C inhibitor, suppressed daphnoretin-, PDBu- and OAG-induced aggregation and ATP release in a concentration-dependent manner. The IC50 values of staurosporine on daphnoretin (50 microM)-, PDBu (100 nM)- and OAG (50 microM)-induced aggregation were 37.7 +/- 8.3, 52.2 +/- 6.3 and 42.8 +/- 8.9 nM respectively. Daphnoretin did not cause significant thromboxane B2 formation in rabbit platelets. Neither daphnoretin nor PDBu caused [3H]inositol monophosphate formation or an increase in intracellular Ca2+ concentration in myo-[3H]inositol-labelled and Fura-2-loaded platelets. Platelet cytosolic protein kinase C was activated by daphnoretin and PDBu in a concentration-dependent manner with an EC50 of 12.4 +/- 1.2 microM and 18.7 +/- 1.4 nM respectively. Membrane-associated protein kinase C activity was increased by either daphnoretin or PDBu. [3H]PDBu binding to washed rabbit platelets was inhibited by daphnoretin in a concentration-dependent manner with an IC50 value of 45.2 +/- 5.2 microM. These results indicate that daphnoretin is a protein kinase C activator in rabbit platelets.


1987 ◽  
Author(s):  
S Krishnamurthi ◽  
V V Kakkar

We have compared the abilities of exogenously added U46619, the PG endoperoxide analogue and, sn-l-oleoyl 2-acetylglycerol (OAG) and sn-1,2-dioctanoylglycerol (diCg), the membrane-permeant DAG analogues, at restoring weak agonist-induced secretion in indomethacin (10μM)-treated platelets (I-PL) in the absence of endogenous PG/Tx synthesis. [14C]-5HT secretion from pre-loaded, washed human platelets was correlated with the levels of [Ca2+]i, using platelets loaded with quin 2. Concentrations of OAG (62-125μM) and diCg (15-30μM), which have previously been shown to be fully effective at activating protein kinase C, failed to significantly enhance [14C]-5HT secretion in combination with ADP (10μM), adrenaline (10μM) or PAF (0.2μM) although they potentiated platelet aggregation, when added 10-30 sec after these agonists to I-PL. eg ADP-0%, 30jiM diCg-9.8%, ADP+diCg-11.9%, 5HT release (p>O.05). In contrast, a low concentration of U46619 (0.2μM), that induced no aggregation, [14C]-5HT secretion or rise in [Ca2+]i levels on its own, was able to synergize strongly at potentiating secretion in combination with all three weak agonists examined, as well as in combination with OAG and diCg (U46619-0%, ADP+U46619-20.4%, U46619+30μM diC8-48% 5HT release) . The greater effectiveness of U46619 at potentiating secretion in combination with the weak agonists was not related to different degrees of [Ca2+]i mobilisation, as ADP and PAF-induced rise in [Ca2+]i occurred to a similar degree in the presence of U46619 and diCg. At a higher concentration of U46619 (0.6μM), which was maximally effective at inducing secretion and elevating [Ca2+]i levels on its own, addition of the weak agonists or OAG or diCg, along with U46619, resulted in a further enhancement of secretion which was independent of changes in [Ca2+]i levels. The results demonstrate that U46619 but not OAG or diCg, is able to fully restore weak agonist-induced secretion in indomethacin-treated platelets, suggesting that the actions of endogenously formed PG endoperoxides/TxA2 cannot be substituted by DAG and raised [Ca2+]i levels and, may be mediated via a mechanism additional to that involving these mediators.


2000 ◽  
Vol 347 (2) ◽  
pp. 561-569 ◽  
Author(s):  
Tsukasa OHMORI ◽  
Yutaka YATOMI ◽  
Naoki ASAZUMA ◽  
Kaneo SATOH ◽  
Yukio OZAKI

Proline-rich tyrosine kinase 2 (Pyk2) (also known as RAFTK, CAKβ or CADTK) has been identified as a member of the focal adhesion kinase (FAK) family of protein-tyrosine kinases and it has been suggested that the mode of Pyk2 activation is distinct from that of FAK. In the present study we investigated the mode of Pyk2 activation in human platelets. When platelets were stimulated with thrombin, Pyk2, as well as FAK, was markedly tyrosine-phosphorylated, in a manner mostly dependent on αIIbβ3 integrin-mediated aggregation. The residual Pyk2 tyrosine phosphorylation observed in the absence of platelet aggregation was completely abolished by pretreatment with BAPTA/AM [bis-(o-aminophenoxy)ethane-N,N,Nʹ,Nʹ-tetra-acetic acid acetoxymethyl ester]. The Pyk2 phosphorylation was inhibited by protein kinase C (PKC) inhibitors at concentrations that inhibited platelet aggregation. In contrast, direct activation of PKC with the active phorbol ester PMA induced the tyrosine phosphorylation of Pyk2 and FAK but only when platelets were fully aggregated with the exogenous addition of fibrinogen (the ligand for αIIbβ3 integrin). Furthermore, PMA-induced Pyk2 (and FAK) tyrosine phosphorylation was also observed when platelets adhered to immobilized fibrinogen. The activation of the von Willebrand factor (vWF)--glycoprotein Ib pathway with botrocetin together with vWF failed to induce Pyk2 (and FAK) tyrosine phosphorylation. Most Pyk2 and FAK was present in the cytosol and membrane skeleton fractions in unstimulated platelets. When platelets were stimulated with thrombin, both Pyk2 and FAK were translocated to the cytoskeleton in an aggregation-dependent manner. In immunoprecipitation studies, Pyk2, as well as FAK, seemed to associate with Shc through Grb2. With the use of glutathione S-transferase fusion proteins containing Shc-SH2, Grb2-SH2, and Grb2 N-terminal and C-terminal SH3 domains, it was implied that the proline-rich region of Pyk2 (and FAK) binds to the N-terminal SH3 domain of Grb2 and that the phosphotyrosine residue of Shc binds to the SH2 domain of Grb2. Although Pyk2 and FAK have been reported to be differentially regulated in many cell types, our results suggest that, in human platelets, the mode of Pyk2 activation is mostly similar to that of FAK, in terms of αIIbβ3 integrin-dependent and PKC-dependent tyrosine phosphorylation. Furthermore, Pyk2, as well as FAK, might have one or more important roles in post-aggregation tyrosine phosphorylation events, in association with the cytoskeleton and through interaction with adapter proteins including Grb2 and Shc.


1987 ◽  
Author(s):  
J A Ware ◽  
M Smith ◽  
E W Salzman

Platelet aggregation and secretion induced by phorbol ester (PMA) or diacylglycerol (DAG) are preceded by an increase in [Ca++] that is detected byaequorin, but not by quin2, fura-2, or indo-1, suggesting that these indicatorsreflect different aspects of Ca++ homeostasis, possibly different functional Ca++ pools. Addition of two conventional agonists in subthreold concentrations synergistically enhances the [Ca++] rise and aggregation.However, if PMA or DAG is the first agonist the subsequent quin2-indicated [Ca++] rise after thrombin is reduced.Whether aequorin-indicated [Ca++] is similarly affected is unknown. We studied gel-filtered platelets loaded with aequorin or a fluorophore and added PMA, DAG, thrombin or ADP, alone or in combination. Either PMA or DAG alone caused a concentration-dependent increase in [Ca++] detectable with aequorin but not with the fluorophores; simultaneous addition of thrombin or ADP with DAG or PMA produced a larger [Ca++] rise than either alone. However, addition of DAG or PMA as a first agonist reduced subsequent aequorin-indicated [Ca++] rises following thrombin or ADP in a concentration and time-dependent manner. Inhibition of ADP or thrombin-induced [Ca++] rise was not always accompanied by inhibition of aggregation or secretion. Combination of subthreshold concentrations of ADP and thrombin produced an enhanced [Ca++] rise and aggregation. However, this synergistic effect was inhibited by preincubation with DAG or PMA. Neither this effect nor DAG-induced [Ca++] rise was inhibited by the protein kinase C inhibitor H-7. In genera^ preincubation of platelets with an agonist enhances Ca rise and aggregation in response to a second agonist; in contrasl protein kinase C activators, which themselves elevate [Ca++] as shown by aequorin, inhibit aequorin-indicated Ca rises after ADP or thrombin, and limit synergism between these two agonists.


1993 ◽  
Vol 264 (5) ◽  
pp. F845-F853
Author(s):  
M. M. Friedlaender ◽  
D. Jain ◽  
Z. Ahmed ◽  
D. Hart ◽  
R. L. Barnett ◽  
...  

Previous work from this laboratory has identified an endothelin (ET) type A (ETA) receptor on cultured rat renal medullary interstitial cells (RMIC), coupled to phosphatidylinositol-specific phospholipase C (PI-PLC), dihydropyridine-insensitive receptor-operated Ca2+ channels, and phospholipase A2. The current studies explored a role for ET stimulation of phosphatidylcholine-specific phospholipase D (PC-PLD) in intracellular signaling of this cell type. ET stimulated PLD activation, as measured by phosphatidic acid (PA) or phosphatidylethanol (PEt) accumulation, in a time- and concentration-dependent manner. Inhibition of diacylglycerol (DAG) kinase by ethylene glycol dioctanoate or 6-(2)4-[(4-fluorophenyl)-phenylmethylene]-1-piperadinyl]ethy l-7-methyl-5H - thiaxolo-[3,2-alpyrimidin]-5-one (R 59022) failed to blunt PA accumulation, indicating that PLD, and not DAG, was the source of PA. Inhibition of PA phosphohydrolase (PAP) by propranolol increased late accumulation of PA, suggesting that the prevailing metabolic flow was in the direction of PA to DAG. Phorbol 12-myristate 13-acetate (PMA) augmented ET-evoked PEt accumulation, whereas downregulation of protein kinase C (PKC) obviated agonist-induced PEt production. PMA augmentation of PLD activity proceeded independent of cytosolic free Ca2+ concentration. Ca2+ derived from either intracellular or extracellular sources enhanced ET-related PEt accumulation but was without effect in PKC-downregulated cells. Collectively, these observations indicate that ET stimulates PLD production in RMIC. PKC is the major regulator of this process, with Ca2+ playing a secondary, modulatory role. In addition, these data suggest that PC-PLD is coupled to the ETA receptor.


Blood ◽  
1993 ◽  
Vol 82 (9) ◽  
pp. 2704-2713 ◽  
Author(s):  
R Vezza ◽  
R Roberti ◽  
GG Nenci ◽  
P Gresele

Abstract Prostaglandin E2 (PGE2) is produced by activated platelets and by several other cells, including capillary endothelial cells. PGE2 exerts a dual effect on platelet aggregation: inhibitory, at high, supraphysiologic concentrations, and potentiating, at low concentrations. No information exists on the biochemical mechanisms through which PGE2 exerts its proaggregatory effect on human platelets. We have evaluated the activity of PGE2 on human platelets and have analyzed the second messenger pathways involved. PGE2 (5 to 500 nmol/L) significantly enhanced aggregation induced by subthreshold concentrations of U46619, thrombin, adenosine diphosphate (ADP), and phorbol 12-myristate 13-acetate (PMA) without simultaneously increasing calcium transients. At a high concentration (50 mumol/L), PGE2 inhibited both aggregation and calcium movements. PGE2 (5 to 500 nmol/L) significantly enhanced secretion of beta-thromboglobulin (beta TG) and adenosine triphosphate from U46619- and ADP-stimulated platelets, but it did not affect platelet shape change. PGE2 also increased the binding of radiolabeled fibrinogen to the platelet surface and increased the phosphorylation of the 47-kD protein in 32P- labeled platelets stimulated with subthreshold doses of U46619. Finally, the amplification of U46619-induced aggregation by PGE2 (500 nmol/L) was abolished by four different protein kinase C (PKC) inhibitors (calphostin C, staurosporine, H7, and TMB8). Our results suggest that PGE2 exerts its facilitating activity on agonist-induced platelet activation by priming PKC to activation by other agonists. PGE2 potentiates platelet activation at concentrations produced by activated platelets and may thus be of pathophysiologic relevance.


2009 ◽  
Vol 29 (6) ◽  
pp. 477-487
Author(s):  
Pochuen Shieh ◽  
Chih-Hung Lee ◽  
Ng Ling Yi ◽  
Chung-Ren Jan

The effect of the cardiovascular drug carvedilol on cytosolic free Ca2+ concentrations ([Ca 2+]i) and viability was examined in Statens Seruminstitut rabbit cornea (SIRC) corneal epithelial cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] (WST-1), respectively. Carvedilol at concentrations between 1 and 30 μM increased [Ca 2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. Carvedilol induced Mn2+ quench of fura-2 fluorescence implicating Ca2+ influx. The Ca2+ influx was inhibited by suppression of protein kinase C activity. In Ca2+-free medium, after pretreatment with 1 μM thapsigargin (an endoplasmic reticulum Ca 2+ pump inhibitor), carvedilol-induced [Ca2+]i rise was reduced; and conversely, carvedilol pretreatment inhibited a major part of thapsigargin-induced [Ca 2+]i rise. Addition of the phospholipase C inhibitor 1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione (U73122; 2 μM) did not change carvedilol-induced [Ca2+]i rise. At concentrations between 5 and 70 μM, carvedilol killed cells in a concentration-dependent manner. The cytotoxic effect of 20 μM carvedilol was not reversed by prechelating cytosolic Ca2+ with BAPTA/AM. Apoptosis was induced by 5—70 μM carvedilol. Collectively, in SIRC corneal epithelial cells, carvedilol-induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca 2+ influx via protein kinase C-regulated Ca2+ channels. Carvedilol-caused cytotoxicity was mediated by Ca2+-independent apoptosis in a concentration-dependent manner.


2002 ◽  
Vol 96 (3) ◽  
pp. 651-658 ◽  
Author(s):  
Joen R. Sheu ◽  
George Hsiao ◽  
Hsiung N. Luk ◽  
Yi W. Chen ◽  
Ta L. Chen ◽  
...  

Background Midazolam is widely used as a sedative and anesthetic induction agent. The aim of this study was to systematically examine the inhibitory mechanisms of midazolam in platelet aggregation. Methods The inhibitory mechanisms of midazolam in platelet aggregation were explored by means of analysis of the platelet glycoprotein IIb-IIIa complex, phosphoinositide breakdown, intracellular Ca+2 mobilization, measurement of membrane fluidity, thromboxane B2 formation, and protein kinase C activity. Results In this study, midazolam dose-dependently (6-26 microm) inhibited platelet aggregation in human platelets stimulated by agonists. Midazolam also dose-dependently inhibited phosphoinositide breakdown and intracellular Ca+2 mobilization in human platelets stimulated by collagen. Midazolam (6-26 mum) significantly inhibited thromboxane A2 formation stimulated by collagen in human platelets. Moreover, midazolam (15 and 26 mum) dose-dependently decreased the fluorescence of platelet membranes tagged with diphenylhexatriene. Rapid phosphorylation of a platelet protein of Mr 47,000 (P47), a marker of protein kinase C activation, was triggered by collagen (2 microg/ml). This phosphorylation was markedly inhibited by midazolam (26 microm). Conclusions These results indicate that the antiplatelet activity of midazolam may be involved in the following pathways: the effects of midazolam may initially be caused by induction of conformational changes in platelet membrane, leading to a change in the activity of phospholipase C, and subsequent inhibition of phosphoinositide breakdown and thromboxane A2 formation, thereby leading to inhibition of both intracellular Ca+2 mobilization and phosphorylation of P47 protein.


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