arachidonyltrifluoromethane and 4-bromophenacyl-bromide

To determine the cellular mechanisms underlying mast cell histamine release induced by ionic and nonionic radiographic contrast media.. Histamine release from rat pulmonary mast cells was measured after incubation with various radiographic contrast media. The cellular cAMP content was determined by an enzymatic immunoassay.. Both ionic and nonionic contrast media stimulated the histamine release, although the former was more potent than the latter. Dibutyryl cAMP suppressed histamine release evoked by ionic but not nonionic contrast media in a manner dependent on A kinase. The cellular cAMP content was lowered only by ionic contrast media. However, a secretory phospholipase A2 inhibitor p-bromophenacyl bromide inhibited both ionic and nonionic contrast media-evoked histamine releases.. We demonstrated for the first time the difference and similarity in the cellular mechanisms underlying histamine release induced by ionic and nonionic contrast media, in which the reduction in cAMP was specific for ionic materials and the activation of secretory phospholipase A2 may be common to both agents.

Topics: Acetophenones; Animals; Arachidonic Acids; Bucladesine; Calcium; Contrast Media; Cyclic AMP; Enzyme Inhibitors; Histamine Release; In Vitro Techniques; Lung; Male; Mast Cells; Phospholipases A; Phospholipases A2; Rats; Rats, Sprague-Dawley

4-Bromophenacyl bromide (BPB) is generally used as a phospholipase A(2) (PLA2) inhibitor. In the present study, we demonstrate that BPB induces Ca2+ influx in human gingival fibroblasts. In fura-2-loaded human gingival fibroblasts, BPB evoked a transient increase in intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. The BPB-induced Ca2+ mobilization was also shown in a single fluo-3-loaded-fibroblast. The BPB-induced increase in [Ca2+]i was completely abolished by the elimination of the external Ca2+. Ca2+ influx induced by the Ca2+-mobilizing agonist histamine was markedly enhanced in the presence of BPB. These suggest that the BPB-induced Ca2+ mobilization is due to the influx of extracellular Ca2+. However, it is unlikely that the effect of BPB is dependent on the inhibition of PLA2 activity, because other PLA2 inhibitors, such as AACOCF3, quinacrine dihydrochloride and manoalide, failed to induce Ca2+ mobilization. Chemical compounds similar to BPB, but which have no -CH2-Br at position 1 in the benzene ring failed to evoke Ca2+ mobilization, indicating that the position of -CH2--Br in BPB is important for causing the Ca2+ influx.

Topics: Acetophenones; Aniline Compounds; Arachidonic Acids; Bradykinin; Calcium; Cells, Cultured; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fibroblasts; Fluorescent Dyes; Gingiva; Histamine; Humans; Kinetics; Phospholipases A; Phospholipases A2; Quinacrine; Spectrometry, Fluorescence; Structure-Activity Relationship; Terpenes; Xanthenes

Phospholipase A2 (PLA2) has been postulated to play a role in the regulation of cytokine expression. Therefore, the objective of the present study was to investigate the effects of PLA2 inhibitors p-bromophenacyl bromide (BPB) and arachidonyl trifluoromethyl ketone (AACOCF3) on interleukin-2 (IL-2) expression in murine primary splenocytes. Pretreatment of the splenocytes with both BPB and AACOCF3 suppressed phorbol 12-myristate 13-acetate plus ionomycin-induced IL-2 secretion in a concentration-dependent manner. Inhibition > 90% of IL-2 secretion was observed at 1 microM BPB and 10 microM AACOCF3 compared to the respective vehicle control. Likewise, IL-2 steady-state mRNA expression was inhibited by both PLA2 inhibitors in a concentration-dependent fashion with > 90% inhibition at 1 microM BPB and 20 microM AACOCF3. Taken together, these data demonstrated that PLA2 inhibitors BPB and AACOCF3 are robust inhibitors of IL-2 expression at both the mRNA and protein levels in murine splenocytes. Moreover, these findings suggest that drugs and chemicals which inhibit PLA2 may have marked effects on T-cell function.

Topics: Acetophenones; Animals; Arachidonic Acids; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Gene Expression; Interleukin-1; Mice; Phospholipases A; Phospholipases A2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Spleen; Time Factors

In an evaluation of the contribution of swelling-induced amino acid release, through the regulatory volume decrease (RVD) process, to cerebral ischemic injury, studies of the role of phospholipases and protein kinases in the response to hyposmotic stress were undertaken using an in vivo rat cortical cup model. Hyposmotic stress induced significant releases of aspartate, glutamate, glycine, phosphoethanolamine, taurine and GABA from the rat cerebral cortex. Taurine release was most affected, exhibiting a greater than 9-fold increase during the hyposmotic stimulus. The phospholipase A2 (PLA2) inhibitors 4-bromophenacyl bromide (1 microM) and 7,7-dimethyleicosadienoic acid (5 microM) had no significant effects on hyposmotically induced amino acid release. AACOCF3 (50 microM), an inhibitor of cytosolic PLA2 decreased taurine release to 84% of DMSO controls. The release of the other amino acids was not affected. The phospholipase C inhibitor U73122 (5 microM) had no significant effects on amino acid release. The protein kinase C (PKC) inhibitor chelerythrine (5 microM) significantly reduced hyposmotically induced taurine release to 72% of saline controls but had no significant effects on the other amino acids. Stimulation of PKC with phorbol 12-myristate, 13-acetate (10 microM) did not significantly change taurine, glutamate, glycine or phosphethanolamine release. The releases of aspartate and GABA were enhanced 2 to 3 fold. Phorbol 12,13-didecanoate (10 microM), another potent stimulator of PKC, significantly increased taurine release to 122% of DMSO controls. The releases of aspartate, glutamate and glycine were enhanced 2.5 to 3.5 fold. Similarly, stimulation of protein kinase A with forskolin (100 microM) significantly increased taurine, aspartate, and glycine release 1.5- to 2-fold compared to DMSO controls. In summary, phospholipases may play a minor role in volume regulation. These studies also support the hypothesis that protein kinases play a modulatory role in the RVD response. The results show that although RVD may play a role, additional mechanisms, including phospholipase activation, must be involved in the ischemia-evoked release of excitotoxic amino acids.

Topics: Acetophenones; Alanine; Amino Acids; Animals; Arachidonic Acids; Aspartic Acid; Brain Edema; Cerebral Cortex; Colforsin; Cyclic AMP-Dependent Protein Kinases; Dimethyl Sulfoxide; Enzyme Inhibitors; Estrenes; Ethanolamines; Fatty Acids, Unsaturated; gamma-Aminobutyric Acid; Glutamic Acid; Glycine; Hypotonic Solutions; Male; Osmotic Pressure; Phosphodiesterase Inhibitors; Phospholipases A; Phospholipases A2; Protein Kinase C; Pyrrolidinones; Rats; Rats, Sprague-Dawley; Serine; Solvents; Taurine; Water-Electrolyte Balance

It has been established that amyloid beta peptide (AbetaP) activates phospholipase A2, phospholipase C and phospholipase D of LA-N-2 cells and other cell types. Nicotine in addition to being a cholinergic agonist, may be neuroprotective. We have investigated the ability of (-)nicotine to blunt the phospholipase activations by AbetaP in LA-N-2 cells. (-)Nicotine inhibits the AbetaP activation of phospholipase A2, with an IC50 of 76 microM and of phospholipase D with an IC50 of 252 microM. (-)Nicotine did not blunt the AbetaP activation of phospholipase C. These inhibitions of AbetaP activations were not observed with (+)nicotine or cotinine. The (-)nicotine inhibition of AbetaP activation of these two phospholipases was unaffected by hexamethonium and D-tubocurarine. There was no inhibition of the phospholipase A2 activity present in homogenates of LA-N-2 cells. Exposure of LA-N-2 cells to (-)nicotine for 2 h resulted in the blockade of phospholipase A2 activation by kainate and AbetaP but did not affect the ability of quisqualate and AbetaP to activate phospholipase D. These data suggest that if the nicotine inhibition of AbetaP activations is receptor occupancy mediated then it is by an atypical receptor type.

Topics: Acetophenones; Amyloid beta-Peptides; Arachidonic Acids; Aristolochic Acids; Brain; Brain Chemistry; Cells, Cultured; Cotinine; Enzyme Activation; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Hexamethonium; Kainic Acid; Nicotine; Nicotinic Agonists; Nicotinic Antagonists; Phenanthrenes; Phospholipase D; Phospholipases A; Phospholipases A2; Quisqualic Acid; Tubocurarine; Type C Phospholipases

The role of phospholipase A2 (PLA2) and its metabolite arachidonic acid (AA) in the proliferation and differentiation of HL-60 cells was investigated. Addition of either 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) or retinoic acid (RA) to HL-60 cells for 2 h inhibited PMA-stimulated PLA2 activity measured by [3H]AA release. The inhibitor of PLA2 activity, p-bromophenacyl bromide (BPB), significantly inhibited the proliferation of HL-60 cells and of fibroblast L929 and Swiss 3T3 cells in a dose-dependent manner. The effect of BPB on proliferation is probably through its inhibitory effect on PLA2 activity, since the same doses of BPB which inhibited proliferation also inhibited PLA2 activity determined by [3H]AA release. The importance of PLA2 activity for cell growth was further supported by the effect of two other PLA2 inhibitors, AACOCF3 and scalaradial, which inhibited HL-60 proliferation in a dose-dependent manner. BPB, AACOCF3 and scalaradial significantly increased the doubling time to 32.4 h, 34.0 h and 31.8 h, respectively, compared with 24.6 h in the control. The inhibitory effect of BPB on HL-60 proliferation was reversed by addition of exogenous free AA to HL-60 cells, indicating the importance of this metabolite for the proliferation process. This reversible effect is specific for AA since it was not achieved by other fatty acids like linolenic acid (LA) or oleic acid (OA). Addition of free AA to HL-60 cells did not induce differentiation, as expected. Although BPB, AACOCF3, or scalaradial inhibited proliferation, they did not induce differentiation nor affect the differentiation induced by 1,25(OH)2D3 or RA. These results implicate that PLA2 activity has no regulatory role in differentiation of HL-60 cells. The differential effect of PLA2 inhibitors on proliferation and differentiation of HL-60 cells suggests that these two processes function under different regulatory mechanisms.

Topics: 3T3 Cells; Acetophenones; Animals; Anti-Inflammatory Agents; Arachidonic Acid; Arachidonic Acids; Blotting, Northern; Calcitriol; Cell Differentiation; Cell Division; Enzyme Inhibitors; Granulocytes; HL-60 Cells; Homosteroids; Humans; Mice; Phospholipases A; Phospholipases A2; Sesterterpenes; Terpenes; Tetradecanoylphorbol Acetate; Tretinoin