scholarly journals Vitamin E potentiates arachidonate release and phospholipase A2 activity in rat heart myoblastic cells

1996 ◽  
Vol 319 (2) ◽  
pp. 385-391 ◽  
Author(s):  
Khai TRAN ◽  
Jason T WONG ◽  
Edmund LEE ◽  
Alvin C. CHAN ◽  
Patrick C. CHOY
Keyword(s):  
Enzyme Activity ◽  
Protein Kinase C ◽  
Vitamin E ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Rat Heart ◽  
Lipid Vesicles ◽  
Ionophore A23187 ◽  
Kinase C ◽  
Arachidonate Release

Cytosolic phospholipase A2 (cPLA2) selectively catalyses the release of arachidonic acid from the sn-2 position of glycerophospholipids to produce prostaglandins and leukotrienes. In this study, vitamin E enrichment of rat heart myoblastic H9c2 cells caused an increase in the release of arachidonate during ionophore (A23187) stimulation. PLA2 activity in the cytosolic fraction was also enhanced but enzyme activity in the particulate fraction was not affected by this treatment. Immunoblotting analysis with a polyclonal anti-cPLA2 antibody showed an increased level of the enzyme in vitamin E-treated cells. Direct incorporation of vitamin E into lipid vesicles in the assay mixture resulted in modulation of enzyme activity in a biphasic manner. Pretreatment of cells with phorbol 12-myristate 13-acetate, a known activator of protein kinase C, synergistically potentiated the ionophore-induced arachidonate release in both the control and vitamin E-treated cells. However, vitamin E treatment by itself did not affect the protein kinase C activity, indicating that the vitamin E-induced activation of cPLA2 was independent of the protein kinase C cascade. Collectively, these results suggest that vitamin E potentiates arachidonate release through the direct and/or indirect modulation of cPLA2 activity.

scholarly journals Diradylglycerols stimulate phospholipase A2 and subsequent exocytosis in ram spermatozoa. Evidence that the effect is not mediated via protein kinase C

1994 ◽  
Vol 297 (1) ◽  
pp. 225-232 ◽  
Author(s):  
E R S Roldan ◽  
C Fragio
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Kinase Inhibitor ◽  
Ionophore A23187 ◽  
Kinase C ◽  
Acrosomal Exocytosis ◽  
Phospholipase A2 Activity

We tested the hypothesis that the role of diacylglycerol (DAG) in sperm acrosomal exocytosis is related to the activation of phospholipase A2, and that this effect is not mediated via protein kinase C. Treatment of [14C]arachidonic acid-labelled ram spermatozoa with Ca2+ and the ionophore A23187 stimulated both liberation of arachidonic acid and acrosomal exocytosis. No changes in [14C]DAG or [14C]monoacylglycerol were found after stimulation of spermatozoa, thus suggesting that arachidonic acid may be released exclusively via phospholipase A2. An increase in the endogenous levels of diradylglycerols (DRGs), resulting from exposure either to the DAG kinase inhibitor R 59022 or to exogenous 1-oleoyl-2-acetyl-sn-glycerol or 1,2-dioctanoyl-sn-glycerol, led to an increase in both phospholipase A2 activity and exocytosis when cells were stimulated with A23187 and Ca2+. Addition of DRGs that do not stimulate protein kinase C(1,3-dioctanoylglycerol, 1-O-hexadecyl-2-acetyl-rac-glycerol) also resulted in an increase in phospholipase A2 activity and exocytosis. On the other hand, phorbol esters (phorbol 12,13-dibutyrate; phorbol 12-myristate 13-acetate) did not enhance enzyme activity or exocytosis. Finally, exposure to 1-O-hexadecyl-2-O-methyl-rac-glycerol, a compound known to inhibit protein kinase C, did not affect phospholipase A2 activity or acrosomal exocytosis. We therefore conclude that in spermatozoa the messenger role of DAG is related to the activation of phospholipase A2, which in turn would generate an array of metabolites directly or indirectly involved in bringing about exocytosis of the acrosome.

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 Prostacyclin inhibits platelet aggregation induced by phorbol ester or Ca2+ ionophore at steps distal to activation of protein kinase C and Ca2+-dependent protein kinases

1989 ◽  
Vol 258 (1) ◽  
pp. 57-65 ◽  
Author(s):  
W Siess ◽  
E G Lapetina
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Shape Change ◽  
Ionophore A23187 ◽  
Maximal Effect ◽  
Kinase C ◽  
Dependent Protein ◽  
High Concentrations

Suspensions of aspirin-treated, 32P-prelabelled, washed platelets containing ADP scavengers in the buffer were activated with either phorbol 12,13-dibutyrate (PdBu) or the Ca2+ ionophore A23187. High concentrations of PdBu (greater than or equal to 50 nM) induced platelet aggregation and the protein kinase C (PKC)-dependent phosphorylation of proteins with molecular masses of 20 (myosin light chain), 38 and 47 kDa. No increase in cytosolic Ca2+ was observed. Preincubation of platelets with prostacyclin (PGI2) stimulated the phosphorylation of a 50 kDa protein [EC50 (concn. giving half-maximal effect) 0.6 ng of PGI2/ml] and completely abolished platelet aggregation [ID50 (concn. giving 50% inhibition) 0.5 ng of PGI2/ml] induced by PdBu, but had no effect on phosphorylation of the 20, 38 and 47 kDa proteins elicited by PdBu. The Ca2+ ionophore A23187 induced shape change, aggregation, mobilization of Ca2+, rapid phosphorylation of the 20 and 47 kDa proteins and the formation of phosphatidic acid. Preincubation of platelets with PGI2 (500 ng/ml) inhibited platelet aggregation, but not shape change, Ca2+ mobilization or the phosphorylation of the 20 and 47 kDa proteins induced by Ca2+ ionophore A23187. The results indicate that PGI2, through activation of cyclic AMP-dependent kinases, inhibits platelet aggregation at steps distal to protein phosphorylation evoked by protein kinase C and Ca2+-dependent protein kinases.

Regulation of rat Na+-K+-ATPase activity by PKC is modulated by state of phosphorylation of Ser-943 by PKA

1997 ◽  
Vol 273 (6) ◽  
pp. C1981-C1986 ◽  
Author(s):  
Xian-Jun Cheng ◽  
Jan-Olov Höög ◽  
Angus C. Nairn ◽  
Paul Greengard ◽  
Anita Aperia
Keyword(s):  
Enzyme Activity ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Response To Treatment ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Present Evidence ◽  
Cos Cells ◽  
Kinase C ◽  
Kinase A

We have previously shown that the rat Na+-K+-ATPase α1-isoform is phosphorylated at Ser-943 by protein kinase A (PKA) and at Ser-23 by protein kinase C (PKC), which in both cases results in inhibition of enzyme activity. We now present evidence that suggests that the phosphorylation of Ser-943 by PKA modulates the response of Na+-K+-ATPase to PKC. Rat Na+-K+-ATPase α1 or a mutant in which Ser-943 was changed to Ala-943 was stably expressed in COS cells. The inhibition of enzyme activity measured in response to treatment with the phorbol ester, phorbol 12,13-dibutyrate (PDBu; 10−6 M), was significantly reduced in the cells expressing the Ala-943 mutant compared with that observed in cells expressing wild-type enzyme. In contrast, for cells expressing Na+-K+-ATPase α1 in which Ser-943 was mutated to Asp-943, the effect of PDBu was slightly enhanced. The PDBu-induced inhibition was not mediated by activation of the adenosine 3′,5′-cyclic monophosphate/PKA system and was not achieved via direct phosphorylation of Ser-943. Sp-5,6-DCl-cBIMPS, a specific PKA activator, increased the phosphorylation of Ser-943, and this was associated with an enhanced response to PDBu. Thus the effect of PKC on rat Na+-K+-ATPase α1 is determined not only by the activity of PKC but also by the state of phosphorylation of Ser-943.

Mechanism of Hepatic Heme Oxygenase-1 Induction by Isoflurane

2006 ◽  
Vol 104 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Alexander Hoetzel ◽  
Daniel Leitz ◽  
Rene Schmidt ◽  
Eva Tritschler ◽  
Inge Bauer ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Heme Oxygenase ◽  
Kupffer Cell ◽  
Cell Function ◽  
Heme Oxygenase 1 ◽  
Gadolinium Chloride ◽  
Kinase C

Background The heme oxygenase pathway represents a major cell and organ protective system in the liver. The authors recently showed that isoflurane and sevoflurane up-regulate the inducible isoform heme oxygenase 1 (HO-1). Because the activating cascade remained unclear, it was the aim of this study to identify the underlying mechanism of this effect. Methods Rats were anesthetized with pentobarbital intravenously or with isoflurane per inhalation (2.3 vol%). Kupffer cell function was inhibited by dexamethasone or gadolinium chloride. Nitric oxide synthases were inhibited by either N(omega)-nitro-L-arginine methyl ester or S-methyl thiourea. N-acetyl-cysteine served as an antioxidant, and diethyldithiocarbamate served as an inhibitor of cytochrome P450 2E1. Protein kinase C and phospholipase A2 were inhibited by chelerythrine or quinacrine, respectively. HO-1 was analyzed in liver tissue by Northern blot, Western blot, immunostaining, and enzymatic activity assay. Results In contrast to pentobarbital, isoflurane induced HO-1 after 4-6 h in hepatocytes in the pericentral region of the liver. The induction was prevented in the presence of dexamethasone (P < 0.05) and gadolinium chloride (P < 0.05). Inhibition of nitric oxide synthases or reactive oxygen intermediates did not affect isoflurane-mediated HO-1 up-regulation. In contrast, chelerythrine (P < 0.05) and quinacrine (P < 0.05) resulted in a blockade of HO-1 induction. Conclusion The up-regulation of HO-1 by isoflurane in the liver is restricted to parenchymal cells and depends on Kupffer cell function. The induction is independent of nitric oxide or reactive oxygen species but does involve protein kinase C and phospholipase A2.

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