scholarly journals Protein kinase C-mediated phospholipase A2 activation, platelet-activating factor generation and prostacyclin release in spontaneously beating rat cardiomyocytes

1993 ◽  
Vol 290 (2) ◽  
pp. 477-482 ◽  
Author(s):  
D J Church ◽  
S Braconi ◽  
M B Vallotton ◽  
U Lang
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Platelet Activating Factor ◽  
Eicosatetraenoic Acid ◽  
Induced Response ◽  
Rat Cardiomyocytes ◽  
Kinase C ◽  
Eicosanoid Release ◽  
Pkc Alpha

The expression of protein kinase C (PKC) isoenzymes and the effects of PKC activation on myocardial phospholipase A2 (PLA2) activity, platelet-activating factor (PAF) generation and eicosanoid release were studied in spontaneously beating cultured rat cardiomyocytes. Western blotting analysis indicated that these cells contain PKC alpha, beta, delta and zeta, but not PKC gamma or epsilon. Stimulation of cardiomyocytes with 4 beta-phorbol 12-myristate 13-acetate (PMA) led to a rapid increase in particulate-bound PKC activity, a response attributed to the activation of alpha-, delta- and zeta- type PKCs but not beta-type PKC. Translocation of PKC alpha, delta and zeta was accompanied by simultaneous increases in cellular lysophosphatidylcholine (lyso-PC), PAF, 15(S)-hydroxy-5,8,-11,13-eicosatetraenoic acid (15-HETE), prostaglandin E2 (PGE2) and prostacyclin (PGI2) generation, suggesting that one or more of these isoenzymes directly or indirectly activates a PLA2 in these cells. Confirming this, 4 beta-phorbol 12-monoacetate and 4 alpha-phorbol had no effect on cellular eicosanoid formation, while the PMA-induced response was fully abolished both in the presence of the PKC inhibitors staurosporine and CGP 41251 and in PKC-down-regulated cells. PKC alpha, delta and/or zeta therefore appear to play an important role in the PMA-mediated activation of cardiomyocyte PLA2, an event leading to subsequent production of PGI2, PGE2, 15-HETE, lyso-PC and PAF in this tissue.

scholarly journals Differential regulation of phospholipase D and phospholipase A2 by protein kinase C in P388D1 macrophages

1997 ◽  
Vol 321 (3) ◽  
pp. 805-810 ◽  
Author(s):  
Jesús BALSINDE ◽  
María A. BALBOA ◽  
Paul A. INSEL ◽  
Edward A. DENNIS
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Phospholipase D ◽  
Phorbol Esters ◽  
Platelet Activating Factor ◽  
Lipid Mediator ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Pkc Activation

Activation of P388D1 macrophages by phorbol myristate acetate (PMA) resulted in the translocation of the protein kinase C (PKC) isoforms α, Δ, and ε from the cytosol to membranes. Furthermore, PMA activated phospholipase D (PLD) in these cells, and potentiated the effect of the inflammatory lipid mediator platelet-activating factor (PAF) on PLD activation. PAF also activated phospholipase A2 (PLA2) and enhanced arachidonic acid (AA) release in P388D1 macrophages, and bacterial lipopolysaccharide (LPS) increased the responsiveness of these cells to PAF. In contrast with PLD, PLA2 activation in P388D1 macrophages was found to take place independently of PKC. This was supported by the following evidence: (i) PMA neither induced AA release nor enhanced the PAF response; (ii) inclusion of PMA along with LPS during priming did not have any effect on PAF-stimulated AA release; (iii) down-regulation of PMA-activatable PKC isoforms by chronic treatment with the phorbol ester had no effect on the PAF response; and (iv) the PKC inhibitor staurosporine did not alter the PAF-induced AA release. The present study provides an example of cells in which the direct activation of PKC by phorbol esters does not lead to a primed and/or enhanced AA release. As a unique example in which PKC activation is neither necessary nor sufficient for AA release to occur, this now allows study of the separate and distinct roles for PLD and PLA2 in signal-transduction processes. This has hitherto been difficult to achieve because of the lack of specific inhibitors of these two phospholipases.

Protein kinase C(alpha) actively downregulates through caveolae-dependent traffic to an endosomal compartment

2000 ◽  
Vol 113 (14) ◽  
pp. 2575-2584
Author(s):  
C. Prevostel ◽  
V. Alice ◽  
D. Joubert ◽  
P.J. Parker
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Initial Step ◽  
Receptor Internalization ◽  
Similar Process ◽  
Receptor Desensitization ◽  
Kinase C ◽  
Annexin I ◽  
Pkc Alpha

Receptor desensitization occurs through receptor internalization and targeting to endosomes, a prerequisite for sorting and degradation. Such trafficking processes may not be restricted to membrane associated receptors but may also play an important role in the downregulation of cytoplasmic transducers such as protein kinase C (PKC). It is demonstrated here that acute TPA exposure induces the transport of activated PKC(alpha) from the plasma membrane to endosomes. This process requires PKC activity and catalytically competent PKC can even promote a similar process for a truncated regulatory domain PKC(α) protein. It is established that PKC(α) is targeted to the endosome compartment as an active kinase, where it colocalizes with annexin I, a substrate of PKC. Thus, PKC(alpha) downregulation shares features with plasma membrane associated receptor sorting and degradation. However, it is shown that PKC(α) delivery to the endosome compartment is not a Rab5 mediated process in contrast to the well characterised internalisation of the transferrin receptor. An alternative route for PKC(alpha) is evidenced by the finding that the cholesterol binding drugs nystatin and filipin, known to inhibit caveolae mediated trafficking, are able to block PKC(alpha) traffic and down regulation. Consistent with this, the endosomes where PKC(alpha) is found also contain caveolin. It is concluded that the initial step in desensitisation of PKC(alpha) involves active delivery to endosomes via a caveolae mediated process.

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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