Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of membrane phospholipids in porcine testicular androgen and 16-androstene biosynthesis was examined by monitoring the effects of phospholipase treatments on the activities of the steroid transforming enzymes. Untreated (control) microsomes from immature pig testes converted pregnenolone to 17-hydroxypregnenolone and DHA to 5,16-androstadien-3 beta-ol (andien-beta) and 4,16-androstadien-3-one (dienone) in the 16-androstene pathway, these metabolites accounting for most (65%) of the pregnenolone converted. The 4-ene steroids in the androgen pathway (progesterone, 17-hydroxyprogesterone, androstenedione and testosterone) totalled less than 10% of the pregnenolone metabolites. No estrogens or 5 alpha-reduced metabolites were detected. Treatment with phospholipase A2 or C, decreased the conversion of pregnenolone to 4-ene-3-oxo steroids but did not decrease the quantities of 5-ene-3 beta-hydroxysteroids. Confirmation of these findings was obtained by measuring the individual enzymatic steps. Phospholipases A2 and C significantly reduced the conversion of DHA to androstenedione and andien-beta to dienone but did not affect 17-hydroxylase or 'andien-beta-synthetase'. However, when the C-17, 20 lyase step was measured alone, phospholipase C decreased the quantity of androstenedione produced indicating that the side-chain cleavage reaction may involve a lipid component. The different effects of phospholipases on these enzymes suggests that pregnenolone metabolism may be regulated by alterations in the membrane microenvironment.
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PMID:Phospholipases modulate immature pig testicular androgen and 16-androstene biosynthetic pathways in vitro. 173 40

An in vitro system designed to mimic the effect of various plasma nonesterified (polyunsaturated) fatty acids on platelet function and metabolism was employed. Human platelet aggregation induced by submaximal (1.8 micrograms/ml) collagen stimulation was significantly inhibited by 2 min preincubation with 20 microM albumin-bound docosahexaenoic acid (22:6n-3) (DHA), but not by the other fatty acids tested. [3H]Phosphatidic acid (PA) formation, an indicator of phospholipase C activation following platelet stimulation, was moderately inhibited by eicosapentaenoic acid (20:5n-3), 11,14,17-eicosatrienoic acid (20:3n-3), dihomo-gamma-linolenic acid (20:3n-6), as well as DHA, but not by arachidonic acid (20:4n-6); this inhibition of phospholipase C activation could not explain the differential effect of DHA on platelet aggregation. The decreased production of thromboxane A2 (TxA2), as assessed by [3H]12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) formation, may account for the inhibition of collagen-induced aggregation by 20 microM DHA. Surprisingly, preincubation with 40 microM albumin-bound DHA, even though resulting in greater inhibition of collagen-induced aggregation, had less impact on HHT formation. A small but significant increase in [3H]prostaglandin D2 (PGD2) levels following 3-min collagen stimulation may have contributed to the greater antiaggregatory effect of 40 muM DHA. It is concluded that increased plasma nonesterified DHA may contribute to the dampened platelet activation and altered metabolism following fish oil supplementation of the diet.
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PMID:Albumin-bound docosahexaenoic acid and collagen-induced human platelet reactivity. 213 12

The beta-adrenergic receptor located in chick erythrocyte membranes was characterized using (-)-[3H]-dihydroalprenolol ([3H]-DHA) with rapid filtration techniques. The affinity of beta-adrenergic antagonist, (-)-propranolol, was approximately 100-fold higher than that of (+)-propranolol. Catecholamines were bound with the receptor in the following order, (-)-isoproterenol greater than (-)-norepinephrine greater than (-)-epinephrine, suggested the binding site to be beta 1-classification. When the membrane preparation was treated with phosphatidylcholine-hydrolyzing phospholipase C (PCase) of Clostridium perfringens or phosphatidylinositol-specific phospholipase C (PIase) of Bacillus thuringiensis, [3H]-DHA binding was decreased to the level of 66 or 86% of the control, respectively. The treatment with sphingomyelinase C (SMase) of Bacillus cereus, however, did not cause any appreciable reduction of [3H]-DHA binding. Throughout these experiments, the equilibrium dissociation constant (KD) of [3H]-DHA was not influenced by phospholipases C. The affinity of isoproterenol for beta-receptor was decreased in the absence of GTP, but not altered in the presence of GTP by PIase action. Treatment with PCase or SMase, however, did not affect the affinity of isoproterenol for beta-receptor. Treatment with PIase inhibited basal, isoproterenol-stimulated and forskolin-stimulated adenylate cyclase activities. On the other hand, PCase treatment inhibited only isoproterenol-stimulated adenylate cyclase activity, but not basal and forskolin-stimulated activities. These results suggest that membrane phospholipids, especially phosphatidylcholine (PC) and phosphatidylinositol (PI), are directly related to the receptor binding and that PI interacts with adenylate cyclase activity.
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PMID:Effects of phospholipases C on the beta-receptor-adenylate cyclase system of chick erythrocyte membranes. 287 18

We examined effects of acute unilateral enucleation on incorporation from blood of intravenously injected unsaturated [1-14C]arachidonic acid ([14C]AA) and [1-14C]docosahexaenoic acid ([14C]DHA), and of saturated [9,10-3H]palmitic acid ([3H]PA), into visual and nonvisual brain areas of awake adult Long-Evans hooded rats. Regional cerebral metabolic rate for glucose (rCMRglc) values also were assessed with 2-deoxy-D-[1-14C]glucose ([14C]DG). One day after unilateral enucleation, an awake rat was placed in a brightly lit visual stimulation box with black and white striped walls, and a radiolabeled fatty acid was infused for 5 min or [14C]DG was injected as a bolus. [14C]DG also was injected in a group of rats kept in the dark for 4 h. Fifteen minutes after starting an infusion of a radiolabeled fatty acid, or 45 min after injecting [14C]DG, the rat was killed and the brain was prepared for quantitative autoradiography. Incorporation coefficients k* of fatty acids, or rCMRglc values, were calculated in homologous brain regions contralateral and ipsilateral to enucleation. As compared with ipsilateral regions, rCMRglc was reduced significantly (by as much as -39%) in contralateral visual areas, including the superior colliculus, lateral geniculate body, and layers I, IV, and V of the primary (striate) and secondary (association, extrastriate) visual cortices. Enucleation did not affect incorporation of [3H]PA into contralateral visual regions, but reduced incorporation of [14C]AA and of [14C]DHA by -18.5 to -2.1%. Percent reductions were correlated with percent reductions in rCMRglc in most but not all regions. No effects were noted at any of nine non-visual structures that were examined. These results indicate that enucleation acutely reduces neuronal activity in contralateral visual areas of the awake rat and that the reductions are coupled to reduced incorporation of unsaturated fatty acids into sn-2 regions of phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Reduced fatty acid incorporation likely reflects reduced activity of phospholipases A2 and/or phospholipase C.
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PMID:In vivo cerebral incorporation of radiolabeled fatty acids after acute unilateral orbital enucleation in adult hooded Long-Evans rats. 811 26

The effect of ascorbic acid 6-docosahexaenoate (DHA-VC) on the phospholipase-C-mediated hydrolysis of phosphatidylcholine was investigated. In human non-small cell lung cancer cells (PC-14) exposed to DHA-VC for 24 hr, a dose-dependent increase in phosphatidylcholine-specific phospholipase C (PC-PLC) activity was seen. PC-PLC activity in whole-cell homogenate of PC-14 cells was increased about 2.5-fold by 2 hr of treatment with DHA-VC (20 micrograms/ml). Treatment with DHA-VC also augmented PC-PLC activity in the crude membrane extract. On the other hand, DHA-VC inhibited the activity of phospholipase A2 (ID50 = 800 micrograms/ml). Another water-soluble analog, choline docosahexaenoate, also stimulated PC-PLC activity. To explore the effect of DHA-VC on phosphatidylcholine turnover, we analyzed phospholipids labeled with [14C] choline or [3H]myristate by thin-layer chromatography, and found that the amount of [14C]- and [3H]-labeled phosphatidylcholine was constant in the presence of DHA-VC. These results suggest that phosphatidylcholine turnover was not influenced by DHA-VC. DHA-VC treatment increased protein kinase C activity of the cells in the late phase (120 min), suggesting that DHA-VC-induced diacylglycerol production mediated by PC-PLC causes protein kinase C activation. Considering that significant inhibition of DNA synthesis occurred 12 hr after 2 hr of treatment with DHA-VC (20 micrograms/ml), DHA-VC-induced PC-PLC activation seems to be an early event in DHA-VC-induced cytotoxicity, which suggests that the effects of DHA-VC on signal transduction pathways may play an important role in the cytotoxicity of DHA-VC.
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PMID:Novel water-soluble derivatives of docosahexaenoic acid increase diacylglycerol production mediated by phosphatidylcholine-specific phospholipase C. 838 49

The objective of the present study was to investigate the effect of membrane fatty acid (FA) composition on the activity of phospholipase C (PLC) in HT-29 human colon cancer cells. The membrane FA composition was altered by supplementing cultured cells with FAs of different composition. The FAs were stearic acid (18:0; SA), gamma linolenic acid (18:3 omega 6; gamma LnA); alpha linolenic acid (18:3 omega 3; alpha LnA;); eicosapentaenoic acid (20:5 omega 3; EPA) and docosahexaenoic acid (22:6 omega 3; DHA). The fatty acids were supplemented as a FA/BSA complex. Cells supplemented with SA served as the control. Tumor growth was followed by counting the number of cells in culture. The results indicate that polyunsaturated fatty acid (PUFA) supplementation had no consistent effect on tumor growth from 1 day to another throughout the 15 days of growth. The fatty acid composition of membranes indicates that cells incorporated and modified the supplemented fatty acids by desaturation, elongation and retroconversion. The unsaturation index (UI) of membranes of cells supplemented with EPA and DHA was higher than other groups. PLC activity; measured in the absence of GTP gamma(S) in the assay mixture; was not influenced by membrane FA modification. However, in the presence of GTP gamma(S) PLC of cells supplemented with 18:3(omega 6) was the lowest among the groups. It has been shown that 18:3(omega 6) accumulated the most in the phosphatidylethanolamine (PE) fraction. There was a negative correlation between the activity of PLC in the presence of G protein activation and PE 18:3 (omega 6) content without affecting UI. It was concluded that G protein may be sensitive to the level of 18:3(omega 6) content and not to the general fluidity of the membranes.
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PMID:The effect of unsaturated fatty acids on membrane composition and signal transduction in HT-29 human colon cancer cells. 895 Feb 5

In this study, we demonstrate that astroglial 5-HT2A receptors are linked to the mobilization of polyunsaturated fatty acids (PUFA). Stimulation of C6 glioma cells, prelabeled with [3H]arachidonate (AA, 20:4n6) and [14C]docosahexaenoate (DHA, 22:6n3), with serotonin and the 5-HT(2A/2C) receptor agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI) resulted in the mobilization of both [3H] and [14C] into the supernatant of the cell monolayers. The increased radioactivity in the supernatant was mainly associated with free fatty acids. Experiments using inhibitors of phosphoinositide-specific phospholipase C and PLA2, inhibited the DOI-stimulated mobilization of AA and DHA, suggesting the involvement of both phospholipases. Ketanserin (1 microM), a 5-HT(2A/2C) receptor antagonist, and MDL 100,907 (R(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-pi peridine-methanol) (1 microM), a highly selective antagonist for 5-HT2A receptors, significantly decreased the DOI-stimulated release of AA and DHA. These results indicate that the 5-HT2A receptor is coupled to the mobilization of PUFA. The release of AA and DHA in response to serotonin may represent a mechanism through which astroglia provide these polyunsaturated fatty acids to neurons.
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PMID:Mobilization of arachidonate and docosahexaenoate by stimulation of the 5-HT2A receptor in rat C6 glioma cells. 936 99

The studies of dietary fish oil supplementation in healthy volunteers demonstrate a significant increase in neutrophil EPA content, a concomitant reduction in neutrophil AA content, and suppression of neutrophil LTB4 synthesis by supplementation with dietary fish oil containing approximately 3-4 g EPA daily for a minimum of 4 weeks. Suppression of neutrophil chemotactic responsiveness to LTB4 and FMLP was observed after dietary n-3 PUFA supplementation at these levels. Dietary EPA is more active than DHA in eliciting these effects in human neutrophils. Dietary n-3 PUFA supplementation inhibits neutrophil chemotaxis to these ligands through the inhibition of the signal transduction pathway between the receptor and phospholipase C, as demonstrated by the inhibition of chemotaxin-stimulated IP3 formation, in the absence of an effect on the number or affinity of the respective chemotaxin receptors. In patients with RA, dietary supplementation with n-3 PUFA resulted in decreased AA content of cellular lipids, with an augmented EPA content and decreased LTB4 generation by neutrophils. Dietary supplementation with n-3 PUFA also resulted in augmentation of depressed neutrophil chemotaxis to LTB4 and FMLP. Preliminary findings suggest that the decreased responsiveness to chemotaxins of neutrophils from RA patients is due to down-regulation of chemotaxin receptor number, resulting in decreased signaling via chemotaxin receptors. Dietary fish oil PUFA partially reversed the down-regulation of the chemotaxin receptor of neutrophils of RA patients, but had a lesser effect on chemotaxin receptor signaling and function, probably due to a post-receptor inhibition induced by fish oil PUFA, as was previously observed in healthy controls. Several small clinical trials have each suggested that dietary supplementation with n-3 PUFA resulted in modest improvements in disease activity. Meta-analysis of these studies confirms statistically significant improvements in tender joint count and morning stiffness after 3 months of dietary fish oil supplementation in patients with RA. Dietary supplementation with gamma-linolenic acid-rich oils also inhibits neutrophil LTB4 formation, has other anti-inflammatory and immunosuppressive effects, and shows promise of therapeutic efficacy in RA.
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PMID:The effects of dietary n-3 polyunsaturated fatty acids on neutrophils. 1009 12

Retinal lipids of crayfish, kept at 4 degrees C under continuous darkness for 3 weeks, consisted mainly of phosphatidylcholine (PC) and phosphatidylethanolamine (PE); sphingomyelin (SM), phosphatidylinositol (PI) and phosphatidylserine (PS) were minor contributors. PI, involved in the phototransduction cascade, never reached greater concentrations than 7% of the total. High concentrations of polyunsaturated fatty acids (PUFA) such as 20:4n-6, 20:5n-3 and 22:6n-3 (DHA, docosahexaenoic acid) were present in PC, PE and PS, but scarce in SM and PI. In retinae of crayfish kept at 4 degrees C in darkness for 3 weeks and then exposed to white light (6 h; ca. 4,500 lx), SM and PS remained seemingly unaffected. PC, however, significantly decreased within 10 min to 65% of the initial value and 50% at 180 min. To study the reduction of PC, lipids of retinae suspended in physiological solution with/without phospholipase C (PLC) and phospholipase A2 (PLA2) inhibitors such as DMDA (= DEDA), manoalide, ET-18-OCH3, and U-73122 were measured. Only free fatty acids (FFA) of retinae with inhibitors of PLA2 like DMDA and manoalide decreased. Retinae irradiated by white light for 3 h displayed a significant reduction of PC, compared with those that had remained in continuous darkness. However, the PC of retinae with PLA2-inhibitors was not decreased by light. Our results provide evidence that not only photoreceptor cell PLC, but also PLA2 is activated by light.
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PMID:Light activation of phospholipase A2 in the photoreceptor of the crayfish (Procambarus clarkii). 1076 25

We investigated, in monocytic leukemia U937 cells, the effects of docosahexaenoic acid (DHA; 22:6 n-3) on calcium signaling and determined the implication of phospholipase C (PLC) and protein kinase C (PKC) in this pathway. DHA induced dose-dependent increases in [Ca2+]i, which were contributed by intracellular pool, via the production of inositol-1,4,5-triphosphate (IP3) and store-operated Ca2+ (SOC) influx, via opening of Ca2+ release-activated Ca2+ (CRAC) channels. Chemical inhibition of PLC, PKCgamma, and PKCdelta, but not of PKCbeta I/II, PKCalpha, or PKCbetaI, significantly diminished DHA-induced increases in [Ca2+]i. In vitro PKC assays revealed that DHA induced a approximately 2-fold increase in PKCgamma and -delta activities, which were temporally correlated with the DHA-induced increases in [Ca2+]i. In cell-free assays, DHA, but not other structural analogs of fatty acids, activated these PKC isoforms. Competition experiments revealed that DHA-induced activation of both the PKCs was dose-dependently inhibited by phosphatidylserine (PS). Furthermore, DHA induced apoptosis via reactive oxygen species (ROS) production, followed by caspase-3 activation. Chemical inhibition of PKCgamma/delta and of SOC/CRAC channels significantly attenuated both DHA-stimulated ROS production and caspase-3 activity. Our study suggests that DHA-induced activation of PLC/IP3 pathway and activation of PKCgamma/delta, via its action on PS binding site, may be involved in apoptosis in U937 cells.
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PMID:Docosahexaenoic acid induces increases in [Ca2+]i via inositol 1,4,5-triphosphate production and activates protein kinase C gamma and -delta via phosphatidylserine binding site: implication in apoptosis in U937 cells. 1787 67


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