scholarly journals Endotoxic lipid A induces intracellular Ca2+ increase in human platelets

1991 ◽  
Vol 278 (1) ◽  
pp. 75-80 ◽  
Author(s):  
M Romano ◽  
M Molino ◽  
C Cerletti
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Lipid A ◽  
Human Platelets ◽  
Free System ◽  
Fura 2 ◽  
Kinase C ◽  
Activated Platelets ◽  
A Cell ◽  
Protein Kinase C Activation

The activation of protein kinase C by endotoxic lipid A was observed with both intact platelets and in a cell-free system [Romano & Hawiger (1990) J. Biol. Chem. 265, 1765-1770]. We have now studied the action of lipid A on intracellular Ca2+ concentration ([Ca2+]i). Lipid A induced a concentration-dependent rise in [Ca2+]i in human platelets loaded with fura-2, which reached a maximum at 37.1 +/- 3.8 s (tmax). Maximum [Ca2+]i levels, observed at 30 microM lipid A, were 432 +/- 60 nM. EGTA (2 mM) or NiCl2 (1 mM) each decreased the lipid A-dependent elevation of [Ca2+]i by 50-60% without significant modification of tmax, but shortening the time for 50% recovery (t50) from greater than 400 s to 113.1 +/- 29.1 s and 54 +/- 2.1 s, respectively. Quenching of the fura-2 signal was also observed in lipid A-stimulated platelets resuspended with MnCl2 (1 mM), suggesting that both mobilization and external influx of Ca2+ occur. Intracellular Ca2+ mobilization depended on release from Ins(1,4,5)P3-sensitive stores, since Ins(1,4,5)P3 accumulation was detected in lipid A-activated platelets. Staurosporine, an inhibitor of protein kinase C, blocked the [Ca2+]i rise generated by lipid A in platelets [concn. giving 50% inhibition (IC50) = 0.1 microM], prolonging the tmax. to 54.7 +/- 5.1 s, but decreasing the t50 to 157.5 +/- 31.8 s. Staurosporine also suppressed InsP3 accumulation (IC50 = 0.15 microM). These results suggest that platelet activation by lipid A involves an interaction between [Ca2+]i elevation and protein kinase C activation.

ENDOTOXIC LIPID A INDUCES BINDING OF FIBRINOGEN TO HUMAN PLATELETS VIA PROTEIN KINASE C PATHWAY

1987 ◽  
Author(s):  
Sheila Timmons ◽  
Jadwiqa Grabarek ◽  
Jack Hawiqer
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Lipid A ◽  
Human Platelets ◽  
Biologically Active ◽  
Active Principle ◽  
Gram Negative ◽  
Kinase C ◽  
Induced Aggregation ◽  
Protein Kinase C Activation

Endotoxic Lipid A is the biologically active principle of lipopolysaccharide of Gram-negative bacteria, a most frequent cause of sepsis underlying Disseminated Intravascular Coagulation (DIC) and shock. We have shown that endotoxic Lipid A activates Protein Kinase C in human platelets. Phosphorylation of a 47kDa protein (P47), a marker for Protein Kinase C activation, was observed within the first minute of interaction of Lipid A with platelets. This was accompanied by gradual exposure of the receptor for 125I-labeled fibrinogen (F). Binding of 125I-F was saturable and specific. When Lipid X, a precursor of endotoxic Lipid A and its competitive inhibitor, was used, the binding of 125I-F was blocked with 50% inhibition at a 1:1 stoichiometry between Lipid X and Lipid A. At the same time, phosphorylation of P47 was prevented. Since Lipid X constitutes a "half molecule" of Lipid A, we interpret these results as indicative of competitive blocking of endotoxic Lipid A in terms of Protein Kinase C activation and exposure of platelet receptors for fibrinogen. Binding of fibrinogen is necessary for platelet aggregation and endotoxic Lipid A-induced aggregation was also blocked by Lipid X. Endotoxic Lipid A-induced exposure of fibrinogen receptors via the Protein Kinase C pathway can contribute to involvement of platelets in microcirculatory thrombosis observed in patients with DIC and Gram-negative sepsis

Comparison of the modes of action of Ca2+ ionophore A23187 and thrombin in protein kinase C activation in human platelets

FEBS Letters ◽  
1985 ◽  
Vol 192 (1) ◽  
pp. 4-8 ◽  
Author(s):  
Kimihiko Sano ◽  
Hajime Nakamura ◽  
Tamotsu Matsuo ◽  
Yasuhiro Kawahara ◽  
Hisashi Fukuzaki ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Human Platelets ◽  
Ionophore A23187 ◽  
Modes Of Action ◽  
Kinase C ◽  
Protein Kinase C Activation

scholarly journals Prostaglandin E2 potentiates platelet aggregation by priming protein kinase C

Blood ◽  
1993 ◽  
Vol 82 (9) ◽  
pp. 2704-2713 ◽  
Author(s):  
R Vezza ◽  
R Roberti ◽  
GG Nenci ◽  
P Gresele
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Prostaglandin E2 ◽  
Platelet Activation ◽  
Human Platelets ◽  
Platelet Surface ◽  
Kinase C ◽  
Activated Platelets ◽  
Induced Aggregation

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.

Modification of Na+/H+ Exchanger in Human Platelets by 1,2-Dioctanoylglycerol, a Protein Kinase C Activator

1990 ◽  
Vol 64 (01) ◽  
pp. 165-171 ◽  
Author(s):  
Yukio Ozaki ◽  
Yuki Mastsumoto ◽  
Yutaka Yatomi ◽  
Masaaki Higashihara
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rate Constant ◽  
Human Platelets ◽  
Kinase C ◽  
Km Value ◽  
The Difference ◽  
The One ◽  
Protein Kinase C Activation

SummaryProtein kinase C activation in human platelets has a modulatory role in maintaining intracellular pH (pHi), by adjusting pHi at a particular value (7.22). Changes in pHi induced by protein kinase C appeared to be dependent upon the difference between H+ efflux catalyzed by the Na+/H+ exchanger and H+ production. The pHi recovery after acid loading was significantly facilitated by protein kinase C activation. Analysis of the rate constant for pHi recovery suggested that the turnover rate or the apparent affinity of the Na+/H+ exchanger for H+ was increased. Protein kinase C also decreased the Km value of the Na+/H+ exchanger for extracellular Na+. Thus, it is suggested that the role of protein kinase C in platelet pHi regulation is dual, adjusting the pHi value at a certain setpoint on the one hand, and increasing the rate constant of the Na+/H+ exchanger on the other.

Protein Kinase C Activation and Lipid Peroxidation by Doxorubicin Analogues

1989 ◽  
Vol 75 (4) ◽  
pp. 358-361 ◽  
Author(s):  
Romolo A. Gambetta ◽  
Patrizia Banfi ◽  
Cinzia Lanzi ◽  
Annarita Franzi ◽  
Franco Zunino
Keyword(s):  
Lipid Peroxidation ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Human Platelets ◽  
Sugar Moiety ◽  
Kinase C ◽  
Induce Lipid Peroxidation ◽  
Pkc Activation ◽  
Activate Protein Kinase ◽  
Protein Kinase C Activation

Several doxorubicin analogues have been tested for their capacity to activate protein kinase C (PKC) and to induce lipid peroxidation in intact human platelets. Only doxorubicin and 4′-iodo-doxorubicin were able to induce lipid peroxidation and PKC activation the first beeing the most effective. N-acetyl-doxorubicin, N-trifluoroacetyl-doxorubicin-14-valerate (AD32) and doxorubicin-14-propionate were not effective on either event. This correlation supports that PKC activation in human platelets by doxorubicin is mediated by lipid peroxidation and suggests that the effect is specific for anthracyclines with a doxorubicin aglycone and a free charged amino group in the sugar moiety. The results stress the new action of anthracyclines, whose pharmacologic implications are presently under investigation on nucleated cells.

scholarly journals Protein kinase C activation is not a key step in ADP-mediated exposure of fibrinogen receptors on human platelets

FEBS Letters ◽  
1995 ◽  
Vol 364 (1) ◽  
pp. 87-90 ◽  
Author(s):  
Fabio M. Pulcinelli ◽  
Barrie Ashby ◽  
Pier Paolo Gazzaniga ◽  
James L. Daniel
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Human Platelets ◽  
Kinase C ◽  
Protein Kinase C Activation
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