Biomaterial Database

Endotoxic lipid A induces intracellular Ca2+ increase in human platelets. 1991

M Romano, and M Molino, and C Cerletti

Istituto di Patologia Medica e Medicina Mediterranea, Università di Messina, Italy.

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.

UI	MeSH Term	Description	Entries
D007295	Inositol Phosphates	Phosphoric acid esters of inositol. They include mono- and polyphosphoric acid esters, with the exception of inositol hexaphosphate which is PHYTIC ACID.	Inositol Phosphate,Phosphate, Inositol,Phosphates, Inositol
D008050	Lipid A	Lipid A is the biologically active component of lipopolysaccharides. It shows strong endotoxic activity and exhibits immunogenic properties.
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D009532	Nickel	A trace element with the atomic symbol Ni, atomic number 28, and atomic weight 58.69. It is a cofactor of the enzyme UREASE.
D011493	Protein Kinase C	An serine-threonine protein kinase that requires the presence of physiological concentrations of CALCIUM and membrane PHOSPHOLIPIDS. The additional presence of DIACYLGLYCEROLS markedly increases its sensitivity to both calcium and phospholipids. The sensitivity of the enzyme can also be increased by PHORBOL ESTERS and it is believed that protein kinase C is the receptor protein of tumor-promoting phorbol esters.	Calcium Phospholipid-Dependent Protein Kinase,Calcium-Activated Phospholipid-Dependent Kinase,PKC Serine-Threonine Kinase,Phospholipid-Sensitive Calcium-Dependent Protein Kinase,Protein Kinase M,Calcium Activated Phospholipid Dependent Kinase,Calcium Phospholipid Dependent Protein Kinase,PKC Serine Threonine Kinase,Phospholipid Sensitive Calcium Dependent Protein Kinase,Phospholipid-Dependent Kinase, Calcium-Activated,Serine-Threonine Kinase, PKC
D001792	Blood Platelets	Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation.	Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004533	Egtazic Acid	A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.	EGTA,Ethylene Glycol Tetraacetic Acid,EGATA,Egtazic Acid Disodium Salt,Egtazic Acid Potassium Salt,Egtazic Acid Sodium Salt,Ethylene Glycol Bis(2-aminoethyl ether)tetraacetic Acid,Ethylenebis(oxyethylenenitrile)tetraacetic Acid,GEDTA,Glycoletherdiamine-N,N,N',N'-tetraacetic Acid,Magnesium-EGTA,Tetrasodium EGTA,Acid, Egtazic,EGTA, Tetrasodium,Magnesium EGTA
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005456	Fluorescent Dyes	Chemicals that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.	Flourescent Agent,Fluorescent Dye,Fluorescent Probe,Fluorescent Probes,Fluorochrome,Fluorochromes,Fluorogenic Substrates,Fluorescence Agents,Fluorescent Agents,Fluorogenic Substrate,Agents, Fluorescence,Agents, Fluorescent,Dyes, Fluorescent,Probes, Fluorescent,Substrates, Fluorogenic