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von Hegedus JH, de Jong AJ, Hoekstra AT, Spronsen E, Zhu W, Cabukusta B, Kwekkeboom JC, Heijink M, Bos E, Berkers CR, Giera MA, Toes REM, Ioan-Facsinay A. Oleic acid enhances proliferation and calcium mobilization of CD3/CD28 activated CD4 + T cells through incorporation into membrane lipids. Eur J Immunol 2024:e2350685. [PMID: 38890809 DOI: 10.1002/eji.202350685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 05/06/2024] [Accepted: 05/10/2024] [Indexed: 06/20/2024]
Abstract
Unsaturated fatty acids (UFA) are crucial for T-cell effector functions, as they can affect the growth, differentiation, survival, and function of T cells. Nonetheless, the mechanisms by which UFA affects T-cell behavior are ill-defined. Therefore, we analyzed the processing of oleic acid, a prominent UFA abundantly present in blood, adipocytes, and the fat pads surrounding lymph nodes, in CD4+ T cells. We found that exogenous oleic acid increases proliferation and enhances the calcium flux response upon CD3/CD28 activation. By using a variety of techniques, we found that the incorporation of oleic acid into membrane lipids, rather than regulation of cellular metabolism or TCR expression, is essential for its effects on CD4+ T cells. These results provide novel insights into the mechanism through which exogenous oleic acid enhances CD4+ T-cell function.
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Affiliation(s)
- Johannes Hendrick von Hegedus
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Anja J de Jong
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Anna T Hoekstra
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric Spronsen
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Wahwah Zhu
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Birol Cabukusta
- Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Joanneke C Kwekkeboom
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marieke Heijink
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Erik Bos
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Celia R Berkers
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - Martin A Giera
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Rene E M Toes
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Andreea Ioan-Facsinay
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
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Oleic acid-based nanosystems for mitigating acute respiratory distress syndrome in mice through neutrophil suppression: how the particulate size affects therapeutic efficiency. J Nanobiotechnology 2020; 18:25. [PMID: 32005196 PMCID: PMC6995149 DOI: 10.1186/s12951-020-0583-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 01/21/2020] [Indexed: 12/20/2022] Open
Abstract
Background Oleic acid (OA) is reported to show anti-inflammatory activity toward activated neutrophils. It is also an important material in nanoparticles for increased stability and cellular internalization. We aimed to evaluate the anti-inflammatory activity of injectable OA-based nanoparticles for treating lung injury. Different sizes of nanocarriers were prepared to explore the effect of nanoparticulate size on inflammation inhibition. Results The nanoparticles were fabricated with the mean diameters of 105, 153, and 225 nm. The nanocarriers were ingested by isolated human neutrophils during a 5-min period, with the smaller sizes exhibiting greater uptake. The size reduction led to the decrease of cell viability and the intracellular calcium level. The OA-loaded nanosystems dose-dependently suppressed the superoxide anion and elastase produced by the stimulated neutrophils. The inhibition level was comparable for the nanoparticles of different sizes. In the ex vivo biodistribution study, the pulmonary accumulation of nanoparticles increased following the increase of particle size. The nanocarriers were mainly excreted by the liver and bile clearance. Mice were exposed to intratracheal lipopolysaccharide (LPS) to induce acute respiratory distress syndrome (ARDS), like lung damage. The lipid-based nanocarriers mitigated myeloperoxidase (MPO) and cytokines more effectively as compared to OA solution. The larger nanoparticles displayed greater reduction on MPO, TNF-α, and IL-6 than the smaller ones. The histology confirmed the decreased pulmonary neutrophil recruitment and lung-architecture damage after intravenous administration of larger nanoparticles. Conclusions Nanoparticulate size, an essential property governing the anti-inflammatory effect and lung-injury therapy, had different effects on activated neutrophil inhibition and in vivo therapeutic efficacy.
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Carrillo C, Giraldo M, Cavia MM, Alonso-Torre SR. Effect of oleic acid on store-operated calcium entry in immune-competent cells. Eur J Nutr 2016; 56:1077-1084. [PMID: 26830415 DOI: 10.1007/s00394-016-1157-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 01/13/2016] [Indexed: 01/01/2023]
Abstract
PURPOSE To study the mechanism by which oleic acid (OA) (C18:1) exerts its beneficial effects on immune-competent cells. Since store-operated Ca2+ entry (SOCE) is a Ca2+ influx pathway involved in the control of multiple physiological processes including cell proliferation, we studied the effect of OA in Ca2+ signals of Jurkat T cells and THP-1 monocytes, paying particular attention to SOCE. METHODS Changes in [Ca2+]i were measured using the Fura-2 fluorescence dye. Mn2+ uptake was monitored as a rate of quenching of Fura-2 fluorescence measured at the Ca2+-insensitive wavelengths. Thapsigargin was used to induce SOCE in Fura-2-loaded cells. RESULTS We showed a clear dose-dependent SOCE-inhibitory effect of OA in both cell lines. Such an inhibitory effect was PKC independent and totally restored by albumin, suggesting that OA exerts its effect somewhere in the membrane. We also demonstrated that OA induces increases in [Ca2+]i partly mediated by an extracellular Ca2+ influx through econazole-insensitive channels. Finally, we compared the effect of OA with stearic acid (C18:0), assuming the emerged evidence concerning the link between saturated fats and inflammation disorders. Stearic acid failed to inhibit SOCE, independently on the concentration tested, thus intensifying the physiological relevance of our findings. CONCLUSION We suggest a physiological pathway for the beneficial effects of OA in inflammation.
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Affiliation(s)
- Celia Carrillo
- Nutrition and Food Science, Faculty of Sciences, University of Burgos, Pl. Misael Bañuelos s/n, 09001, Burgos, Spain.
| | - María Giraldo
- Nutrition and Food Science, Faculty of Sciences, University of Burgos, Pl. Misael Bañuelos s/n, 09001, Burgos, Spain
| | - M Mar Cavia
- Nutrition and Food Science, Faculty of Sciences, University of Burgos, Pl. Misael Bañuelos s/n, 09001, Burgos, Spain
| | - Sara R Alonso-Torre
- Nutrition and Food Science, Faculty of Sciences, University of Burgos, Pl. Misael Bañuelos s/n, 09001, Burgos, Spain
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Guermouche B, Yessoufou A, Soulimane N, Merzouk H, Moutairou K, Hichami A, Khan NA. n-3 Fatty Acids Modulate T-Cell Calcium Signaling in Obese Macrosomic Rats. ACTA ACUST UNITED AC 2012; 12:1744-53. [PMID: 15601968 DOI: 10.1038/oby.2004.216] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE We investigated the effects of a diet containing EPAX-7010, rich in PUFAs such as eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)], i.e., a PUFA/EPAX regimen, on T-cell activation in diabetic pregnant rats and their obese pups. RESEARCH METHODS AND PROCEDURES Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on Day 5 of gestation. T-cell blastogenesis was assayed by using (3)H-thymidine, whereas intracellular free calcium concentrations ([Ca(2+)]i) were measured by using Fura-2 in diabetic pregnant rats and their obese offspring. RESULTS Concavalin-A-stimulated T-cell proliferation was decreased in both pregnant diabetic rats and their obese pups as compared with control animals. Feeding the PUFA/EPAX diet restored T-cell proliferation in both groups of animals. We also employed ionomycin, which at 50 nM opens calcium channels, and thapsigargin (TG), which recruits [Ca(2+)]i from endoplasmic reticulum pool. We observed that ionomycin-induced increases in [Ca(2+)]i in T-cells of diabetic mothers and obese offspring were greater than in those of control rats. Furthermore, feeding PUFA/EPAX diet diminished significantly the ionomycin-evoked rise in [Ca(2+)]i in diabetic and obese animals. TG-induced increases in [Ca(2+)]i in T-cells of diabetic pregnant rats and their obese offspring were greater than in those of control rats. The feeding of the experimental diet significantly curtailed the TG-evoked increases in [Ca(2+)]i in both diabetic and obese rats. DISCUSSION Together, these observations provide evidence that T-cell activation and T-cell calcium signaling are altered during gestational diabetes and macrosomia. Hence, dietary fish oils, particularly eicosapentaenoic acid and docosahexaenoic acid, may restore these T-cell abnormalities.
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Affiliation(s)
- Baya Guermouche
- Départment de Biologie, Faculté des Sciences, Université de Tlemcen, Algeria
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Oleic acid inhibits store-operated calcium entry in human colorectal adenocarcinoma cells. Eur J Nutr 2011; 51:677-84. [DOI: 10.1007/s00394-011-0246-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 09/07/2011] [Indexed: 11/26/2022]
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Wheal AJ, Alexander SPH, Randall MD. Vasorelaxation to N-oleoylethanolamine in rat isolated arteries: mechanisms of action and modulation via cyclooxygenase activity. Br J Pharmacol 2010; 160:701-11. [PMID: 20590573 DOI: 10.1111/j.1476-5381.2010.00770.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The endocannabinoid-like molecule N-oleoylethanolamine (OEA) is found in the small intestine and regulates food intake and promotes weight loss. The principal aim of the present study was to evaluate the vascular effects of OEA. EXPERIMENTAL APPROACH Perfused isolated mesenteric arterial beds were pre-contracted with methoxamine or high potassium buffers and concentration-response curves to OEA were constructed. Combinations of inhibitors to block nitric oxide production, sensory nerve activity, cyclooxygenase activity, potassium channels, chloride channels and gap junctions, and a cannabinoid CB(1) receptor antagonist, were used during these experiments. The effects of OEA on caffeine-induced contractions in calcium-free buffer were also assessed. Isolated thoracic aortic rings were used as a comparison. KEY RESULTS OEA caused concentration-dependent vasorelaxation in rat isolated mesenteric arterial beds and thoracic aortic rings, with a greater maximal response in mesenteric vessels. This relaxation was sensitive to inhibition of sensory nerve activity and endothelial removal in both preparations. The cyclooxygenase inhibitor indomethacin reversed the effects of capsaicin pre-treatment in perfused mesenteric arterial beds and indomethacin alone enhanced vasorelaxation to OEA. The OEA-induced vasorelaxation was inhibited by a CB(1) receptor antagonist only in aortic rings. In mesenteric arteries, OEA suppressed caffeine-induced contractions in calcium-free buffer. CONCLUSIONS AND IMPLICATIONS The vasorelaxant effects of OEA are partly dependent on sensory nerve activity and a functional endothelium in the vasculature. In addition, vasorelaxation to OEA is enhanced following cyclooxygenase inhibition. OEA may also interfere with the release of intracellular calcium in arterial preparations.
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Affiliation(s)
- A J Wheal
- Smooth Muscle Pharmacology Group, School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK.
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Sawabe Y, Shimamoto C, Sakai A, Kuwabara H, Saad AH, Nakano T, Takitani K, Tamai H, Mori H, Marunaka Y, Nakahari T. Peroxisome proliferation activation receptor α modulation of Ca2+-regulated exocytosis via arachidonic acid in guinea-pig antral mucous cells. Exp Physiol 2010; 95:858-68. [DOI: 10.1113/expphysiol.2010.053603] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Erriquez J, Bernascone S, Ciarletta M, Filigheddu N, Graziani A, Distasi C. Calcium signals activated by ghrelin and D-Lys(3)-GHRP-6 ghrelin antagonist in developing dorsal root ganglion glial cells. Cell Calcium 2009; 46:197-208. [PMID: 19665224 DOI: 10.1016/j.ceca.2009.07.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 07/03/2009] [Accepted: 07/13/2009] [Indexed: 11/27/2022]
Abstract
Ghrelin is a hormone regulating energy homeostasis via interaction with its receptor, GHSR-1a. Ghrelin activities in dorsal root ganglia (DRG) cells are unknown. Herein we show that ghrelin induces a change of cytosolic calcium concentration in both glia and neurons of embryonic chick DRG. Both RT-PCR and binding studies performed with fluorescent ghrelin in the presence of either unlabeled ghrelin or GHSR-1a antagonist D-Lys(3)-GHRP-6, indicate that DRG cells express GHSR-1a. In glial cells the response is characterized by a rapid transient rise in [Ca(2+)](i) followed by a long lasting rise. The calcium elevation is dependent on calcium release from thapsigargin-sensitive intracellular stores and on activation of two distinct Ca(2+) entry pathways, a receptor activated calcium entry and a store operated calcium entry. Surprisingly, D-Lys(3)-GHRP-6 exerts several activities in the absence of exogenous ghrelin: (i) it activates calcium release from thapsigargin-sensitive intracellular stores and calcium entry via voltage-operated channels in non-neuronal cells; (ii) it inhibits calcium oscillations in non-neuronal cells exhibiting spontaneous Ca(2+) activity and iii) it promotes apoptosis of DRG cells, both neurons and glia. In summary, we provide the first evidence for ghrelin activity in DRG, and we also demonstrate that the widely used D-Lys(3)-GHRP-6 ghrelin antagonist features ghrelin independent activities.
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Affiliation(s)
- Jessica Erriquez
- Dipartimento di Scienze Chimiche Alimentari Farmaceutiche e Farmacologiche, Università del Piemonte Orientale A. Avogadro, Novara, Italy
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Sweeney Z, Minatti A, Button D, Patrick S. Small-Molecule Inhibitors of Store-Operated Calcium Entry. ChemMedChem 2009; 4:706-18. [DOI: 10.1002/cmdc.200800452] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Oliveira VH, Nascimento KSO, Freire MM, Moreira OC, Scofano HM, Barrabin H, Mignaco JA. Mechanism of modulation of the plasma membrane Ca(2+)-ATPase by arachidonic acid. Prostaglandins Other Lipid Mediat 2008; 87:47-53. [PMID: 18718873 DOI: 10.1016/j.prostaglandins.2008.07.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 07/15/2008] [Accepted: 07/22/2008] [Indexed: 10/25/2022]
Abstract
The intracellular level of long chain fatty acids controls the Ca(2+) concentration in the cytoplasm. The molecular mechanisms underlying this Ca(2+) mobilization are not fully understood. We show here that the addition of low micromolar concentrations of fatty acids directly to the purified plasma membrane Ca(2+)-ATPase enhance ATP hydrolysis, while higher concentration decrease activity, exerting a dual effect on the enzyme. The effect of arachidonic acid is similar in the presence or absence of calmodulin, acidic phospholipids or ATP at the regulatory site, thereby precluding these sites as probable acid binding sites. At low arachidonic acid concentrations, neither the affinity for calcium nor the phosphoenzyme levels are significantly modified, while at higher concentrations both are decreased. The action of arachidonic acid is isoenzyme specific. The increase on ATP hydrolysis, however, is uncoupled from calcium transport, because arachidonic acid increases the permeability of erythrocyte membranes to calcium. Oleic acid has no effect on membrane permeability while linoleic acid shows an effect similar to that of arachidonic acid. Such effects might contribute to the entry of extracellular Ca(2+) following to fatty acid release.
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Affiliation(s)
- Vanessa H Oliveira
- Instituto de Bioquímica Médica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil
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Inhibition of the histamine-induced Ca2+ influx in primary human endothelial cells (HUVEC) by volatile anaesthetics. Eur J Anaesthesiol 2008; 25:976-85. [PMID: 18631421 DOI: 10.1017/s0265021508004778] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVE Vasoactive substances such as histamine, acetylcholine or ATP increase the [Ca2+]i of endothelial cells, which leads to the activation of nitric oxide synthase (eNOS). The NO produced by this enzyme relaxes the underlying smooth muscle. Evidence suggests that eNOS activation is dependent on agonist-induced Ca2+ entry. Recently we have shown that in human endothelial cells (HUVEC), this Ca2+ entry is sensitive to isoflurane. The objective here was to study the mechanism by which volatile anaesthetics can depress the histamine-induced Ca2+ entry into HUVEC cells. METHODS HUVECs on coverslips were loaded with the Ca2+ indicator Fluo-3 and inserted in a gastight, temperature-controlled perfusion chamber. Excitation was at 488 nm and fluorescence signals were monitored with a confocal laser scanning microscope (MRC1024, Biorad). Direct measurement of the Ca2+ influx was with Mn2+ as surrogate for calcium at 360 nm in cells loaded with Fura-2. RESULTS Addition of histamine induces a biphasic [Ca2+]i increase consisting of Ca2+ release from internal stores and a Ca2+ influx from the external medium (plateau phase). The plateau phase was dose-dependently inhibited by enflurane and sevoflurane (13.7 resp. 21.9% inhibition by 1 MAC anaesthetic). Direct measurement of the Ca2+ influx using the Mn2+ quench of the Fura-2 fluorescence gave similar results. The inhibition of the anaesthetics was not reduced by inhibition of the cGMP pathway, inactivation of protein kinase C, depolarization of the cells or the presence of specific Ca2+-dependent K+ channel inhibitors. Interestingly, unsaturated fatty acids inhibit the histamine-induced Ca2+ influx in a similar way as the volatile anaesthetics. CONCLUSIONS Volatile anaesthetics dose-dependently inhibit the histamine-induced Ca2+ influx in HUVECs by a mechanism that may involve unspecific perturbation of the lipid bilayer.
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Huang YS, Wang SM, Hsu KL, Tseng YZ, Wu JC. Mechanism of oleic acid-induced myofibril disassembly in rat cardiomyocytes. J Cell Biochem 2007; 102:638-49. [PMID: 17428005 DOI: 10.1002/jcb.21317] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study investigated the mechanism of oleic acid (OA)-induced disassembly of myofibrils in cardiomyocytes. OA treatment disrupted myofibrils, as revealed by the disorganization of several sarcomeric proteins. Since focal adhesions (FAs) are implicated in myofibril assembly, we examined structural changes in FAs after OA treatment. Immunofluorescence studies with antibodies against FA proteins (vinculin, integrin beta1D, and paxillin) showed that FAs and costameres disintegrated or disappeared after OA treatment and that the changes in FA proteins occurred prior to myofibril disassembly. The effects of OA on FAs and myofibrils were reversed after removal of OA. OA decreased expression of integrin beta1D, paxillin, vinculin, and actin, and induced tyrosine dephosphorylation of FA kinase (FAK) and paxillin. These effects were blocked by pretreatment with sodium orthovanadate, a protein tyrosine phosphatase (PTP) inhibitor. This inhibitor also prevented OA-induced myofibril disassembly, indicating the involvement of PTP in myofibril disassembly. Furthermore, OA increased protein levels of PTP-PEST. The upregulation of this phosphatase correlated with the tyrosine dephosphorylation of paxillin and FAK, which are targets for PTP-PEST. In addition, OA decreased RhoA activity and the phosphorylation of cofilin, a downstream target of RhoA. Cofilin dephosphorylation increased its actin-severing activity and led to the depolymerization of F-actin, which might provide another potential mechanism for OA-induced myofibril disassembly.
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Affiliation(s)
- Yuahn-Sieh Huang
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
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Holmes AM, Roderick HL, McDonald F, Bootman MD. Interaction between store-operated and arachidonate-activated calcium entry. Cell Calcium 2007; 41:1-12. [PMID: 16765441 DOI: 10.1016/j.ceca.2006.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/22/2006] [Accepted: 04/12/2006] [Indexed: 11/30/2022]
Abstract
A ubiquitous pathway for cellular Ca(2+) influx involves 'store-operated channels' that respond to depletion of intracellular Ca(2+) pools via an as yet unknown mechanism. Due to its wide-spread expression, store-operated Ca(2+) entry (SOCE) has been considered a principal route for Ca(2+) influx. However, recent evidence has suggested that alternative pathways, activated for example by lipid metabolites, are responsible for physiological Ca(2+) influx. It is not clear if these messenger-activated Ca(2+) entry routes exist in all cells and what interaction they have with SOCE. In the present study we demonstrate that HEK-293 cells and Saos-2 cells express an arachidonic acid (AA)-activated Ca(2+) influx pathway that is distinct from SOCE on the basis of sensitivity to pharmacological blockers and depletion of cellular cholesterol. We examined the functional interaction between SOCE and the arachidonate-triggered Ca(2+) influx (denoted non-SOCE). Both Ca(2+) entry routes could underlie substantial long-lasting Ca(2+) elevations. However, the two pathways could not operate simultaneously. With cells that had an on-going SOCE response, addition of arachidonate gave two profound effects. Firstly, it rapidly inhibited SOCE. Secondly, the mode of Ca(2+) influx switched to the non-SOCE mechanism. Addition of arachidonate to naïve cells resulted in rapid activation of the non-SOCE pathway. However, this Ca(2+) entry route was very slowly engaged if the SOCE pathway was already operative. These data indicate that the SOCE and arachidonate-activated non-SOCE pathways interact in an inhibitory manner. We probed the plausible mechanisms by which these two pathways may communicate.
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Affiliation(s)
- Anthony M Holmes
- The Babraham Institute, Laboratory of Molecular Signalling, Babraham, Cambridge CB2 4AT, UK
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Fujiwara S, Shimamoto C, Nakanishi Y, Katsu KI, Kato M, Nakahari T. Enhancement of Ca2+-regulated exocytosis by indomethacin in guinea-pig antral mucous cells: arachidonic acid accumulation. Exp Physiol 2005; 91:249-59. [PMID: 16263797 DOI: 10.1113/expphysiol.2005.032482] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ca2+-regulated exocytosis is enhanced by an autocrine mechanism via the PGE2-cAMP pathway in antral mucous cells of guinea-pigs. The inhibition of the PGE2-cAMP pathway by H-89 (an inhibitor of protein kinase A, PKA) or aspirin (ASA, an inhibitor of cyclo-oxygenase, COX) decreased the frequency of ACh-stimulated exocytotic events by 60%. Indomethacin (IDM, an inhibitor of COX), however, decreased the frequency of ACh-stimulated exocytotic events only by 30%. Moreover, IDM increased the frequency of ACh-stimulated exocytotic events by 50% in H-89-treated or ASA-treated cells. IDM inhibits the synthesis of Prostaglandin (PGG/H) and (15R)-15-hydroxy-5,8,11 cis-13-trans-eicosatetraenoic acid (15R-HPETE), while ASA inhibits only the synthesis of PGG/H. Thus, IDM may accumulate arachidonic acid (AA). AACOCF3 or N-(p-amylcinnamoyl) anthranilic acid (ACA; both inhibitors of phospholipase A2, PLA2), which inhibits AA synthesis, decreased the frequency of ACh-stimulated exocytotic events by 60%. IDM, however, did not increase the frequency in AACOCF3-treated cells. AA increased the frequency of ACh-stimulated exocytotic events in AACOCF3- or ASA-treated cells, similar to IDM in ASA- and H-89-treated cells. Moreover, in the presence of AA, IDM did not increase the frequency of ACh-stimulated exocytotic events in ASA-treated cells. The PGE2 release from antral mucosa indicates that inhibition of PLA2 by ACA inhibits the AA accumulation in unstimulated and ACh-stimulated antral mucosa. The dose-response study of AA and IDM demonstrated that the concentration of intracellular AA accumulated by IDM is less than 100 nm. In conclusion, IDM modulates the ACh-stimulated exocytosis via AA accumulation in antral mucous cells.
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Affiliation(s)
- Shoko Fujiwara
- Department of Physiology, Osaka Medical College, 2-7 Daigakucho, Takatsuki 569-8686, Japan
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Moneer Z, Pino I, Taylor E, Broad L, Liu Y, Tovey S, Staali L, Taylor C. Different phospholipase-C-coupled receptors differentially regulate capacitative and non-capacitative Ca2+ entry in A7r5 cells. Biochem J 2005; 389:821-9. [PMID: 15918794 PMCID: PMC1180733 DOI: 10.1042/bj20050145] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Several receptors, including those for AVP (Arg8-vasopressin) and 5-HT (5-hydroxytryptamine), share an ability to stimulate PLC (phospholipase C) and so production of IP3 (inositol 1,4,5-trisphosphate) and DAG (diacylglycerol) in A7r5 vascular smooth muscle cells. Our previous analysis of the effects of AVP on Ca2+ entry [Moneer, Dyer and Taylor (2003) Biochem. J. 370, 439-448] showed that arachidonic acid released from DAG stimulated NO synthase. NO then stimulated an NCCE (non-capacitative Ca2+ entry) pathway, and, via cGMP and protein kinase G, it inhibited CCE (capacitative Ca2+ entry). This reciprocal regulation ensured that, in the presence of AVP, all Ca2+ entry occurred via NCCE to be followed by a transient activation of CCE only when AVP was removed [Moneer and Taylor (2002) Biochem. J. 362, 13-21]. We confirm that, in the presence of AVP, all Ca2+ entry occurs via NCCE, but 5-HT, despite activating PLC and evoking release of Ca2+ from intracellular stores, stimulates Ca2+ entry only via CCE. We conclude that two PLC-coupled receptors differentially regulate CCE and NCCE. We also address evidence that, in some A7r5 cells lines, AVP fails either to stimulate NCCE or inhibit CCE [Brueggemann, Markun, Barakat, Chen and Byron (2005) Biochem. J. 388, 237-244]. Quantitative PCR analysis suggests that these cells predominantly express TRPC1 (transient receptor potential canonical 1), whereas cells in which AVP reciprocally regulates CCE and NCCE express a greater variety of TRPC subtypes (TRPC1=6>2>3).
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Affiliation(s)
- Zahid Moneer
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Irene Pino
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Emily J. A. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Lisa M. Broad
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Yingjie Liu
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Stephen C. Tovey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Leila Staali
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
- To whom correspondence should be addressed (email )
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Luo D, Sun H, Lan X, Xiao R, Han Q. Direct coupling between arachidonic acid-induced Ca2+ release and Ca2+ entry in HEK293 cells. Prostaglandins Other Lipid Mediat 2005; 75:141-51. [PMID: 15789621 DOI: 10.1016/j.prostaglandins.2004.11.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Arachidonic acid (AA) modulates intracellular Ca2+ signaling via Ca2+ release or/and Ca2+ entry. However, the mechanism underlies either process is unknown; nor is it clear as to whether the two processes are mechanistically linked. By using Fura2/AM, we found that AA induced mobilization of internal Ca2+ store and an increment in Ca2+, Mn2+ and Ba2+ influx in HEK293 cells. The AA-mediated Ca2+ signaling was not due to AA metabolites, and insensitive to capacitative Ca2+ entry inhibitors. Interestingly, isotetrandrine and Gd3+ inhibited both AA-induced Ca2+ release and Ca2+ entry in a concentration-dependent manner without affecting Ca2+ discharge caused by carbachol, caffeine, or thapsigargin. Additionally, similar pattern of inhibition was observed with tetracaine treatment. More importantly, the three compounds exhibited almost equal potent inhibition of AA-initiated Ca2+ release as well as Ca2+ influx. Therefore, this study, for the first time, provides evidence for a direct coupling between AA-mediated Ca2+ release and Ca2+ entry.
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Affiliation(s)
- Dali Luo
- Institute of Cardiovascular Science at Health Science Center, Peking University, Beijing 100083, PR China.
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Grossini E, Avanzi G, Gallicchio M, Molinari C, Vacca G, Bellomo G. Regulation of Ca2+ movements by cyclovirobuxine D in ECV304 endothelial cells. Pharmacol Res 2005; 52:154-61. [PMID: 15967381 DOI: 10.1016/j.phrs.2005.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 01/11/2005] [Accepted: 01/17/2005] [Indexed: 10/25/2022]
Abstract
In Fura-2/loaded ECV304 endothelial cells cyclovirobuxine D promoted a transient increase in cytosolic free Ca2+ originating from both an intracellular pool sensitive to the endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin and the extracellular space. The intracellular pool was apparently different from that mobilized by other agents acting through IP3 generation. The integrity of the plasma membrane was an absolute requirement. In cells treated with digitonin, cyclovirobuxine D did not promote any Ca2+ release from the intracellular stores even at high concentrations and in the absence or presence of thapsigargin or sodium azide, the inhibitors of the endoplasmic reticular or mitochondrial Ca2+ uptake. Furthermore, cyclovirobuxine D was effective in halting the persistent increase in cytosolic Ca2+ caused by thapsigargin, inhibiting the operation of the "capacitative" Ca2+ membrane channels as demonstrated by the decrease in the extent of both Ca2+-overshoot and Mn2+ influx. Additional effects of cyclovirobuxine D included a depolarization of plasma membrane apparently related to an enhanced influx of Na+ from the extracellular space. The results obtained indicate that cyclovirobuxine D markedly affects intracellular Ca2+ homeostasis in ECV304 endothelial cells by both promoting a discharge of intracellular pools and by interfering with the operation of store-dependent channels via plasma membrane depolarization.
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Affiliation(s)
- Elena Grossini
- Dipartimento di Scienze Mediche, Facoltà di Medicina e Chirurgia, Università del Piemonte Orientale A. Avogadro, via Solaroli 17, I-28100 Novara, Italy.
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18
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Martínez MA, Lajas AI, Yago MD, Redondo PC, Granados MP, González A, Rosado JA, Martínez-Victoria E, Mañas M, Pariente JA. Dietary virgin olive oil enhances secretagogue-evoked calcium signaling in rat pancreatic acinar cells. Nutrition 2004; 20:536-41. [PMID: 15165616 DOI: 10.1016/j.nut.2004.03.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE We evaluated the long-term effects of a fat-enriched diet (virgin olive oil) on calcium mobilization and amylase secretion induced by cholecystokinin-octapeptide (CCK-8) in rat pancreatic acinar cells. Olive oil is a major component of the Mediterranean diet, and its role in human health is actively being debated. METHODS Weaning male Wistar rats (21 d old) were assigned to one of two experimental groups and fed for 8 wk with a commercial chow (control group) or an experimental diet (olive group) containing 100 g/kg of virgin olive oil as dietary fat. Intracellular free calcium [Ca(2+)](i) levels were determined by loading the pancreatic cells with the fluorescent ratio-metric calcium indicator Fura-2 on an inverted fluorescent microscope. For measurement of amylase secretion, cells were incubated with the appropriate secretagogue for 30 min, and amylase activities in the supernatant were determined by the Phadebas blue starch method. Analysis of variance was used to test differences between groups. RESULTS Compared with the control group, the CCK-8-induced increase in [Ca(2+)](i) occurred in cells from rats in the olive group (P < 0.05). This stimulatory effect of dietary virgin olive oil was observed in calcium oscillations and large [Ca(2+)](i) transients induced by low (20 pM/L) and high (10 nM/L) concentrations of CCK-8, respectively. In addition to the effects of dietary virgin olive oil on calcium mobilization, it increased (P < 0.05) amylase secretion in response to CCK-8. Olive oil treatment did not significantly alter resting [Ca(2+)](i) or amylase release values compared with the control group. Similar results were obtained when pancreatic acinar cells were stimulated with a high concentration of acetylcholine (10 microM/L). CONCLUSION The present results demonstrate that a diet supplemented with virgin olive oil can modify pancreatic cell function as assessed by [Ca(2+)](i) mobilization and amylase release evoked by secretagogues in rat pancreatic acinar cells. A role for fatty acids in calcium signaling is suggested.
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Affiliation(s)
- María A Martínez
- Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, Granada, Spain
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Aires V, Hichami A, Moutairou K, Khan NA. Docosahexaenoic acid and other fatty acids induce a decrease in pHi in Jurkat T-cells. Br J Pharmacol 2004; 140:1217-26. [PMID: 14645139 PMCID: PMC1574148 DOI: 10.1038/sj.bjp.0705563] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Docosahexaenoic acid (DHA) induced rapid (t1/2=33 s) and dose-dependent decreases in pHi in BCECF-loaded human (Jurkat) T-cells. Addition of 5-(N,N-dimethyl)-amiloride, an inhibitor of Na+/H+ exchanger, prolonged DHA-induced acidification as a function of time, indicating that the exchanger is implicated in pHi recovery. 2. Other fatty acids like oleic acid, arachidonic acid, eicosapentaenoic acid, but not palmitic acid, also induced a fall in pHi in these cells. 3. To assess the role of calcium in the DHA-induced acidification, we conducted experiments in Ca2+-free (0% Ca2+) and Ca2+-containing (100% Ca2+) buffer. We observed that there was no difference in the degree of DHA-induced transient acidification in both the experimental conditions, though pHi recovery was faster in 0% Ca2+ medium than that in 100% Ca2+ medium. 4. In the presence of BAPTA, a calcium chelator, a rapid recovery of DHA-induced acidosis was observed. Furthermore, addition of CaCl2 into 0% Ca2+ medium curtailed DHA-evoked rapid pHi recovery. In 0% Ca2+ medium, containing BAPTA, DHA did not evoke increases in [Ca2+]i, though this fatty acid still induced a rapid acidification in these cells. These observations suggest that calcium is implicated in the long-lasting DHA-induced acidosis. 5. DHA-induced rapid acidification may be due to its deprotonation in the plasma membrane (flip-flop model), as suggested by the following observations: (1) DHA with a -COOH group induced intracellular acidification, but this fatty acid with a -COOCH3 group failed to do so, and (2) DHA, but not propionic acid, -induced acidification was completely reversed by addition of fatty acid-free bovine serum albumin in these cells. 6. These results suggest that DHA induces acidosis via deprotonation and Ca2+ mobilization in human T-cells.
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Affiliation(s)
- Virginie Aires
- UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la vie, 6, Boulevard Gabriel, Dijon 21000, France
| | - Aziz Hichami
- UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la vie, 6, Boulevard Gabriel, Dijon 21000, France
| | - Kabirou Moutairou
- UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la vie, 6, Boulevard Gabriel, Dijon 21000, France
| | - Naim Akhtar Khan
- UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la vie, 6, Boulevard Gabriel, Dijon 21000, France
- Author for correspondence:
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20
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Watson EL, Jacobson KL, Singh JC, DiJulio DH. Arachidonic acid regulates two Ca2+ entry pathways via nitric oxide. Cell Signal 2004; 16:157-65. [PMID: 14636886 DOI: 10.1016/s0898-6568(03)00102-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Several regulated Ca2+ entry pathways have been identified, with capacitative Ca2+ entry (CCE) being the most characterized. In the present study, we examined Ca2+ entry pathways regulated by arachidonic acid (AA) in mouse parotid acini. AA induced Ca2+ release from intracellular stores, and increased Ca2+ entry. AA inhibited thapsigargin (Tg)-induced CCE, whereas AA activated Ca2+ entry when CCE was blocked by gadolinium (Gd3+). AA-induced Ca2+ entry was associated with depletion of calcium from ryanodine-sensitive stores; both AA-induced Ca2+ release and Ca2+ entry were inhibited by tetracaine and the nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (7-NI). The nitric oxide (NO) donor, 1,2,3,4-ox-triazolium,5-amino-3-(3,4-dichlorophenyl)-chloride (GEA 3162), but not 8-bromo-cGMP, mimicked the effects of AA in inhibiting CCE. Results suggest that AA acts via nitric acid to inhibit the CCE pathway that is selective for Ca2+, and to activate a second Ca2+ entry pathway that is dependent on depletion of Ca2+ from ryanodine-sensitive stores.
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Affiliation(s)
- Eileen L Watson
- Department of Oral Biology, University of Washington, Seattle, WA 98195, USA.
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21
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Gamberucci A, Giunti R, Benedetti A. Progesterone inhibits capacitative Ca2+ entry in Jurkat T lymphocytes by a membrane delimited mechanism, independently of plasma membrane depolarization. Cell Calcium 2004; 36:175-80. [PMID: 15193865 DOI: 10.1016/j.ceca.2004.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Accepted: 03/01/2004] [Indexed: 10/26/2022]
Abstract
The non-genomic inhibitory effect of progesterone on capacitative calcium entry was studied in Jurkat T lymphocytes. Capacitative calcium entry was induced by depleting intracellular calcium stores with thapsigargin and evaluated by a calcium free/calcium readmission protocol, in Fura-2 loaded cells. Progesterone (10-40 microg/ml) inhibited calcium entry and concomitantly depolarized cells, as revealed by measuring the plasma membrane potential with the fluorescent probe bis-oxonol. However, experiments run under depolarizing conditions (i.e. by substituting for Na+ with K+ ions in the medium) revealed that progesterone (10-40 microg/ml) could inhibit capacitative calcium entry independently of plasma membrane depolarization. The direct inhibition of calcium entry by progesterone was: (i) reverted by a treatment suitable to remove progesterone bound to cell surface, (ii) apparently related to the extent of membrane bound progesterone (measured radioisotopically), and (iii) specific, in that other related steroid compounds did not inhibit calcium entry.
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Affiliation(s)
- Alessandra Gamberucci
- Dipartimento di Fisiopatologia, Medicina Sperimentale e Sanità Pubblica, Università di Siena, 53100, Italy
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22
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Sergeeva M, Strokin M, Wang H, Ubl JJ, Reiser G. Arachidonic acid in astrocytes blocks Ca(2+) oscillations by inhibiting store-operated Ca(2+) entry, and causes delayed Ca(2+) influx. Cell Calcium 2003; 33:283-92. [PMID: 12618149 DOI: 10.1016/s0143-4160(03)00011-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ATP-elicited oscillations of the concentration of free intracellular Ca(2+) ([Ca(2+)](i)) in rat brain astrocytes were abolished by simultaneous arachidonic acid (AA) addition, whereas the tetraenoic analogue 5,8,11,14-eicosatetraynoic acid (ETYA) was ineffective. Inhibition of oscillations is due to suppression by AA of intracellular Ca(2+) store refilling. Short-term application of AA, but not ETYA, blocked Ca(2+) influx, which was evoked by depletion of stores with cyclopiazonic acid (CPA) or thapsigargin (Tg). Addition of AA after ATP blocked ongoing [Ca(2+)](i) oscillations. Prolonged AA application without or with agonist could evoke a delayed [Ca(2+)](i) increase. This AA-induced [Ca(2+)](i) rise developed slowly, reached a plateau after 5 min, could be reversed by addition of bovine serum albumin (BSA), that scavenges AA, and was blocked by 1 microM Gd(3+), indicative for the influx of extracellular Ca(2+). Specificity for AA as active agent was demonstrated by ineffectiveness of C16:0, C18:0, C20:0, C18:2, and ETYA. Moreover, the action of AA was not affected by inhibitors of oxidative metabolism of AA (ibuprofen, MK886, SKF525A). Thus, AA exerted a dual effect on astrocytic [Ca(2+)](i), firstly, a rapid reduction of capacitative Ca(2+) entry thereby suppressing [Ca(2+)](i) oscillations, and secondly inducing a delayed activation of Ca(2+) entry, also sensitive to low Gd(3+) concentration.
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Affiliation(s)
- Marina Sergeeva
- Institut für Neurobiochemie, Medizinische Fakultät der Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, D-39120 Magdeburg, Germany
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23
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Hichami A, Joshi B, Simonin AM, Khan NA. Role of three isoforms of phospholipase A2 in capacitative calcium influx in human T-cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5557-63. [PMID: 12423354 DOI: 10.1046/j.1432-1033.2002.03261.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study was conducted on human Jurkat T-cell lines in order to elucidate the role of phospholipase A2 in capacitative calcium entry. We have employed thapsigargin (TG) that induces increases in [Ca2+]i by emptying the calcium pool of endoplasmic reticulum, followed by capacitative calcium entry. We designed a Ca2+ free/Ca2+ reintroduction (CFCR) protocol for the experiments, conducted in Ca2+-free medium. By employing CFCR protocol, we observed that addition of exogenous arachidonic acid (AA) stimulated TG-induced capacitative calcium influx. The liberation of endogenous AA and its autocrine action seems to be implicated during TG-induced capacitative calcium influx: TG potentiates the induction of constitutively expressed mRNA of four PLA2 isoforms (type 1B, IV, V, VI), the inhibitors of the three PLA2 isotypes (type 1B, V, VI) inhibit TG-induced release of [3H]AA into the extracellular medium, and finally, these PLA2 inhibitors do curtail TG-stimulated capacitative calcium entry in these cells. These results suggest that stimulation of three isoforms of PLA2 by thapsigargin liberates free AA that, in turn, induces capacitative calcium influx in human T-cells.
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Affiliation(s)
- Aziz Hichami
- UPRES Lipides & Nutrition, Université de Bourgogne 21000 Dijon, France; Central Jalma Research Institute for Leprosy, Agra, UP, India
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24
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Triboulot C, Hichami A, Denys A, Khan NA. Dietary (n-3) polyunsaturated fatty acids exert antihypertensive effects by modulating calcium signaling in T cells of rats. J Nutr 2001; 131:2364-9. [PMID: 11533280 DOI: 10.1093/jn/131.9.2364] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
After 10 wk of feeding an experimental diet enriched with (n-3) polyunsaturated fatty acids (PUFA), i.e., eicosapentaenoic acid [EPA, 20:5(n-3)] and [DHA, 22:6(n-3)] (EPAX), blood pressure in spontaneously hypertensive rats (SHR), but not in normotensive Wistar-Kyoto (WKY) rats was reduced relative to rats fed an unsupplemented control diet. Concanavalin A-stimulated T-cell proliferation was diminished in both strains of rats fed the PUFA/EPAX diet. The experimental diet lowered secretion of interleukin-2 in SHR, but not in WKY rats compared with rats fed the control diet. To determine whether there was a defect in calcium homeostasis in T cells during hypertension, we employed the following agents: caffeine, which recruits calcium from the cytosolic Ca(2+)-induced Ca(2+)-release pool; ionomycin, which at low concentrations opens calcium channels; and thapsigargin (TG), which mobilizes [Ca(2+)]i from the endoplasmic reticulum (ER) pool. Caffeine-induced increases in [Ca(2+)]i were not modified by the PUFA/EPAX diet. The ionomycin-induced increases in [Ca(2+)]i in T cells from SHR were greater than in those from WKY rats; consumption of the PUFA/EPAX diet did not modify Ca(2+) influx in cells of either strain. The TG-induced increases in [Ca(2+)]i in T cells from SHR were greater than those in cells from WKY rats. Interestingly, consumption of the experimental diet reduced TG-evoked increases in [Ca(2+)]i in T cells from SHR and increased those in T cells from WKY rats, indicating that the PUFA/EPAX diet could reverse the calcium mobilization from the ER pool in T cells. These results suggest that (n-3) PUFA exert antihypertensive effects and modulate T-cell calcium signaling during hypertension in rats.
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Affiliation(s)
- C Triboulot
- UPRES Lipids & Nutrition, Faculty of Life Sciences, Université de Bourgogne, Dijon 21000, France
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25
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Du X, Jiang Y, Qian W, Lu X, Walsh JP. Fatty acids inhibit growth-factor-induced diacylglycerol kinase alpha activation in vascular smooth-muscle cells. Biochem J 2001; 357:275-82. [PMID: 11415460 PMCID: PMC1221952 DOI: 10.1042/0264-6021:3570275] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have previously shown that unsaturated fatty acids amplify platelet-derived-growth-factor (PDGF)-induced protein kinase C (PKC) activation in vascular smooth-muscle cells (VSMCs). Diacylglycerol-induced PKC activation is normally terminated by diacylglycerol kinases (DGKs). We thus hypothesized that fatty acids act by inhibiting a DGK. Fractionation of VSMC extracts demonstrated that the DGK alpha isoform was the major DGK activity present. PDGF markedly increased the DGK activity of cultured cells. An inhibitor selective for the DGK alpha isoform, R59949 [3-[2-[4-(bis-(4-fluorophenyl)methylene]piperidin-1-yl)ethyl]-2,3-dihydro-2-thioxo-4(1H)-quinazolinone], abolished the growth-factor-induced increase in DGK activity, but had little effect on basal activity. PDGF thus selectively activates DGKalpha. Epidermal growth factor and alpha-thrombin stimulated total DGK activity similarly to PDGF. Activation by epidermal growth factor was sensitive to R59949, again suggesting involvement of DGKalpha. However, the alpha-thrombin-induced activity was unaffected by this agent. Unsaturated fatty acids inhibited growth-factor-induced DGKalpha activation, but had no effect on basal activity. Fatty acids also amplified the PDGF-induced increase in cell diacylglycerol content. These results indicate that inhibition of DGKalpha contributes to fatty-acid-induced amplification of PKC activation. Increased levels of fatty acids in diabetes may thus contribute to chronic PKC activation associated with this disorder.
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Affiliation(s)
- X Du
- Department of Medicine, Indiana University School of Medicine, Roudebush VA Medical Center (111-E), 1481 West Tenth Street, Indianapolis, IN 46202, USA
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26
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Luo D, Broad LM, Bird GS, Putney JW. Mutual antagonism of calcium entry by capacitative and arachidonic acid-mediated calcium entry pathways. J Biol Chem 2001; 276:20186-9. [PMID: 11274150 DOI: 10.1074/jbc.m100327200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In nonexcitable cells, the predominant mechanism for regulated entry of Ca(2+) is capacitative calcium entry, whereby depletion of intracellular Ca(2+) stores signals the activation of plasma membrane calcium channels. A number of other regulated Ca(2+) entry pathways occur in specific cell types, however, and it is not know to what degree the different pathways interact when present in the same cell. In this study, we have examined the interaction between capacitative calcium entry and arachidonic acid-activated calcium entry, which co-exist in HEK293 cells. These two pathways exhibit mutual antagonism. That is, capacitative calcium entry is potently inhibited by arachidonic acid, and arachidonic acid-activated entry is inhibited by the pre-activation of capacitative calcium entry with thapsigargin. In the latter case, the inhibition does not seem to result from a direct action of thapsigargin, inhibition of endoplasmic reticulum Ca(2+) pumps, depletion of Ca(2+) stores, or entry of Ca(2+) through capacitative calcium entry channels. Rather, it seems that a discrete step in the pathway signaling capacitative calcium entry interacts with and inhibits the arachidonic acid pathway. The findings reveal a novel process of mutual antagonism between two distinct calcium entry pathways. This mutual antagonism may provide an important protective mechanism for the cell, guarding against toxic Ca(2+) overload.
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Affiliation(s)
- D Luo
- Laboratory of Signal Transduction, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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Stulnig TM, Berger M, Roden M, Stingl H, Raederstorff D, Waldhäusl W. Elevated serum free fatty acid concentrations inhibit T lymphocyte signaling. FASEB J 2000; 14:939-47. [PMID: 10783148 DOI: 10.1096/fasebj.14.7.939] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Unbound cis-unsaturated free (i.e., nonesterified) fatty acids (FFA) inhibit T lymphocyte activation in vitro and therefore may exert immunosuppressive effects. However, in blood serum the major proportion of FFA is tightly bound to albumin, whereas unbound FFA are hardly detectable. Since serum FFA elevation occurs under pathological conditions like insulin resistance or cancer, which are often associated with a disturbed immune response, we addressed the question of whether increased serum FFA concentrations could affect T lymphocyte activation under in vivo conditions. Our studies revealed that 1) addition of pure long-chain cis-unsaturated FFA in the absence of albumin inhibited calcium response in cultured Jurkat T cells. 2) In healthy volunteers, serum FFA elevation by a lipid/heparin infusion, including predominantly unsaturated fatty acids, decreased calcium response of cultured T cells in contrast to studies without heparin. 3) Most notably, stepwise increasing serum FFA by lipid/heparin infusion also inhibited calcium response of simultaneously isolated autologous peripheral blood T lymphocytes as well as their CD4(+) and CD8(+) subsets. In conclusion, our data emphasize that serum FFA elevation is able to exert immunosuppressive effects in vivo.
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Affiliation(s)
- T M Stulnig
- Department of Internal Medicine III, University of Vienna, Austria.
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28
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Makowska A, Zablocki K, Duszyński J. The role of mitochondria in the regulation of calcium influx into Jurkat cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:877-84. [PMID: 10651826 DOI: 10.1046/j.1432-1327.2000.01066.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In electrically nonexcitable cells the activity of the plasma membrane calcium channels is controlled by events occurring in mitochondria, as well as in the lumen of the endoplasmic reticulum. Thapsigargin, a specific inhibitor of endoplasmic reticulum Ca2+-ATPase, produces the release of calcium from the endoplasmic reticulum and thus, activation of store-operated calcium channels in the plasma membrane. However, thapsigargin failed to produce significant activation of the channels in Jurkat cells that had been pretreated with mitochondria-directed agents: an uncoupler (carbonyl cyanide m-chlorophenylhydrazone) and oligomycin. This is in spite of the fact that Jurkat cells pretreated with carbonyl cyanide m-chlorophenylhydrazone plus oligomycin are otherwise energetically competent, due to a high rate of glycolysis and the inhibition of mitochondrial F1Fo-ATPase by oligomycin. The pool of intracellular ATP was found not to be influenced by the pretreatments of cells with oligomycin or with oligomycin plus carbonyl cyanide m-chlorophenylhydrazone. In the control cells, we found that the ATP pool amounted to 23.2 +/- 1.9 nmoles per 107 cells (n = 4). In cells pretreated with oligomycin the level of ATP was 21.8 +/- 1.9 nmoles per 107 cells (n = 4), and in cells pretreated with both oligomycin and an uncoupler the level of ATP was 22.1 +/- 0.2 nmoles per 107 cells (n = 3). Moreover, in cells pretreated with oligomycin plus carbonyl cyanide m-chlorophenylhydrazone and suspended in a nominally calcium-free medium, thapsigargin produces transient increases in cytosolic calcium identical to those in the control cells. Thus, this pretreatment does not modify either the content of intracellular calcium stores and/or the activity of calcium ATPase in the plasma membrane. Similar results were obtained when Jurkat cells were challenged by myxothiazol, a potent inhibitor of mitochondrial cytochrome bc1 oxidoreductase. Thapsigargin, although producing calcium release from intracellular stores, was ineffective in triggering the activation of calcium channels in the plasma membrane in the case of cells pretreated with myxothiazol and oligomycin. Our results suggest that coupled mitochondria participate directly in the control of calcium channel activity in the plasma membrane of Jurkat cells. When the mitochondrial protonmotive force is collapsed, either by carbonyl cyanide m-chlorophenylhydrazone or myxothiazol, the channel remains inactive even under conditions of empty intracellular calcium stores.
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Affiliation(s)
- A Makowska
- Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland
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29
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n–3 PUFA dietary supplementation inhibits proliferation and store-operated calcium influx in thymoma cells growing in Balb/c mice. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)32050-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Lambert DM, DiPaolo FG, Sonveaux P, Kanyonyo M, Govaerts SJ, Hermans E, Bueb J, Delzenne NM, Tschirhart EJ. Analogues and homologues of N-palmitoylethanolamide, a putative endogenous CB(2) cannabinoid, as potential ligands for the cannabinoid receptors. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1440:266-74. [PMID: 10521710 DOI: 10.1016/s1388-1981(99)00132-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The presence of CB(2) receptors was reported in the rat basophilic cell line RBL-2H3 and N-palmitoylethanolamide was proposed as an endogenous, potent agonist of this receptor. We synthesized a series of 10 N-palmitoylethanolamide homologues and analogues, varying by the elongation of the fatty acid chain from caproyl to stearoyl and by the nature of the amide substituent, respectively, and evaluated the affinity of these compounds to cannabinoid receptors in the rat spleen, RBL-2H3 cells and CHO-CB(1) and CHO-CB(2) receptor-transfected cells. In rat spleen slices, CB(2) receptors were the predominant form of the cannabinoid receptors. No binding of [(3)H]SR141716A was observed. [(3)H]CP-55,940 binding was displaced by WIN 55,212-2 and anandamide. No displacement of [(3)H]CP-55,940 or [(3)H]WIN 55,212-2 by palmitoylethanolamide derivatives was observed in rat spleen slices. In RBL-2H3 cells, no binding of [(3)H]CP-55,940 or [(3)H]WIN 55,212-2 could be observed and conversely, no inhibitory activity of N-palmitoylethanolamide derivatives and analogues was measurable. These compounds do not recognize the human CB(1) and CB(2) receptors expressed in CHO cells. In conclusion, N-palmitoylethanolamide was, in our preparations, a weak ligand while its synthesized homologues or analogues were essentially inactive. Therefore, it seems unlikely that N-palmitoylethanolamide is an endogenous agonist of the CB(2) receptors but it may be a compound with potential therapeutic applications since it may act via other mechanisms than cannabinoid CB(1)-CB(2) receptor interactions.
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Affiliation(s)
- D M Lambert
- Unité de Chimie Pharmaceutique et de Radiopharmacie, Département des Sciences pharmaceutiques, Université catholique de Louvain, UCL 7340, Avenue Mounier 73, B-1200, Brussels, Belgium.
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Affiliation(s)
- K Kiselyov
- Dept of Physiology, University of Texas, Southwestern Medical Center at Dallas, Dallas, TX 75235, USA
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Zhang MI, O'Neil RG. The diversity of calcium channels and their regulation in epithelial cells. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1999; 46:43-83. [PMID: 10332501 DOI: 10.1016/s1054-3589(08)60469-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- M I Zhang
- Department of Integrative Biology, Pharmacology, and Physiology, University of Texas-Houston Health Science Center 77030, USA
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Seiler L, Matyas S, Fleckenstein-Grün G. Extracellular ATP increases [Ca2+]i in primarily cultured pig coronary smooth muscle cells via a P2Y purinoceptor subtype. J Cardiovasc Pharmacol 1999; 33:807-13. [PMID: 10226870 DOI: 10.1097/00005344-199905000-00019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In primarily cultured pig coronary smooth muscle cells, extracellular adenosine triphosphate (ATP; 10(-9) to 10(-3) M) dose-dependently increases intracellular calcium ([Ca2+]i). The [Ca2+]i transients measured by fura-2 fluorescence consist of peak and plateau phases with [Ca2+]i values of 191.84 +/- 5.67 nM (n = 10) and 91.67 +/- 1.89 nM, respectively. In Ca(2+)-free solution, the peak phases persisted, but there was a loss of the plateau response, indicating an initial ATP-stimulated intracellular Ca2+ release and a subsequent transarcolemmal Ca2+ entry. Various agonists have been used to characterize the P2 purinoceptor subtype involved in the ATP-induced Ca2+ transients. The rank order of potency was uridine triphosphate (UTP) > ATP >> 2-meSATP > beta,gamma-meATP = alpha,beta-meATP = adenosine = 0. To examine the refilling of ATP-sensitive stores, four repetitive 60-s ATP responses were produced throughout with a 5-min recovery period in between. Now the ATP peaks gradually declined in Ca(2+)-free solution, indicating the emptying of the stores. If, however, Ca2+ entry was allowed in the "refilling period" (i.e., between the ATP pulses), the Ca2+ peaks could be maintained or restored, respectively. The data suggest that the ATP-dependent [Ca2+]i transients may be mediated via a UTP > ATP-activated P2Y purinoceptor subtype, mediating both an intracellular Ca2+ release and a transarcolemmal Ca2+ influx. The refilling of Ca2+ stores may occur through the unstimulated membrane after agonist stimulation. A putative pathway may be a "capacitative" Ca2+ entry induced on depletion of intracellular Ca2+ stores.
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Affiliation(s)
- L Seiler
- Department of Physiology I, Albert-Ludwigs-University, Freiburg, Germany
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White R, Hiley CR. The actions of some cannabinoid receptor ligands in the rat isolated mesenteric artery. Br J Pharmacol 1998; 125:533-41. [PMID: 9806337 PMCID: PMC1565654 DOI: 10.1038/sj.bjp.0702111] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The actions of a number of cannabinoid receptor ligands were investigated using the myograph-mounted rat isolated mesenteric artery. Anandamide, CP 55,940, HU-210, palmitoylethanolamide and WIN 55,212-2 all caused concentration-dependent relaxations of methoxamine-precontracted vessels which were not affected by removal of the endothelium. 2. Precontracting vessels with 60 mM KCl instead of methoxamine greatly reduced the vasorelaxant effects of anandamide and palmitoylethanolamide. High K+ solution caused a modest decrease in the relaxant potency of CP 55,940 and HU-210, and had no effect on relaxations induced by WIN 55,212-2. 3. Relaxations of methoxamine-induced tone by anandamide, CP 55,940 and HU-210, but not palmitoylethanolamide and WIN 55,212-2, were attenuated by the cannabinoid receptor antagonist, SR 141716A. Relaxation of vessels contracted with 60 mM KCl by CP 55,940 was also sensitive to SR 141716A. 4. Anandamide and CP 55,940 caused small but concentration-dependent contractions in resting vessels in the absence of extracellular calcium. These were not sensitive to SR 141716A. Palmitoylethanolamide and WIN 55,212-2 produced smaller contractions only at higher concentrations. 5. Anandamide and CP 55,940, but not palmitoylethanolamide and WIN 55,212-2, caused concentration-dependent inhibition of the phasic contractions induced by methoxamine in calcium-free conditions, but only anandamide caused inhibition of contractions to caffeine under such conditions. These inhibitory effects were not antagonised by SR 141716A. 6. The present study provides the first detailed investigation of the actions of cannabinoid agonists on vascular smooth muscle. Our results show that these compounds exert both receptor-dependent and -independent effects on agonist-induced calcium mobilization in the rat isolated mesenteric artery.
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Affiliation(s)
- R White
- Department of Pharmacology, University of Cambridge
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Gamberucci A, Fulceri R, Benedetti A, Bygrave FL. On the mechanism of action of econazole, the capacitative calcium inflow blocker. Biochem Biophys Res Commun 1998; 248:75-7. [PMID: 9675088 DOI: 10.1006/bbrc.1998.8810] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability of bovine serum albumin to reverse the inhibitory action of econazole and the unsaturated fatty acid oleate on store-dependent Ca2+ inflow was examined in Ehrlich ascites tumour cells. We report that inhibition of Ca2+ inflow by both compounds is reversed immediately upon addition of bovine serum albumin. It is concluded that the inhibitory action of econazole resembles that of unsaturated fatty acids. The mechanism appears to be one pertaining to nonspecific events at the plasma membrane, possibly involving alterations in plasma membrane fluidity/structure.
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Affiliation(s)
- A Gamberucci
- Istituto di Patologia Generale, Universita di Siena, Italy
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Filipeanu CM, Brailoiu E, Petrescu G, Nelemans SA. Extracellular and intracellular arachidonic acid-induced contractions in rat aorta. Eur J Pharmacol 1998; 349:67-73. [PMID: 9669498 DOI: 10.1016/s0014-2999(98)00180-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Arachidonic acid induced contractions of de-endothelized rat aortic rings. A more potent effect was obtained after intracellular administration of arachidonic acid using liposomes. Contractions induced by extracellular arachidonic acid were inhibited similarly to phenylephrine-induced contractions by the L-type Ca2+ channel blocker, methoxyverapamil (D600), and the calmodulin inhibitor, calmidazolium. In contrast, contractions induced by arachidonic acid-filled liposomes were not affected by these compounds. Indomethacin did not affect the contractions induced by either extra- or intracellular arachidonic acid, whereas nordihydroguaiaretic acid relaxed contractions induced by extracellular arachidonic acid but not those induced by arachidonic acid-filled liposomes. Apart from a relaxing effect on contractions induced by extracellular arachidonic acid or by phenylephrine, protein kinase C inhibition with 1-(5-isoquinolinesulphonyl-2-methylpiperazine (H7)) had an even more prominent relaxing effect on contractions induced by arachidonic acid-filled liposomes. Therefore, arachidonic acid exerts a contractile effect on rat aorta, and this effect is regulated differently depending on the site of application.
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Affiliation(s)
- C M Filipeanu
- Groningen Institute for Drug Studies, Department of Clinical Pharmacology, University of Groningen, Netherlands
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Zygmunt PM, Högestätt ED, Waldeck K, Edwards G, Kirkup AJ, Weston AH. Studies on the effects of anandamide in rat hepatic artery. Br J Pharmacol 1997; 122:1679-86. [PMID: 9422814 PMCID: PMC1565127 DOI: 10.1038/sj.bjp.0701601] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. The effects of anandamide on K+ currents and membrane potential have been examined in freshly-isolated smooth muscle cells from rat hepatic artery and the results compared with the effects of this arachidonic acid derivative on tension and membrane potential changes in segments of whole artery. 2. In the presence of 0.3 mM L-NOARG and 10 microM indomethacin, anandamide (0.1-100 microM) and endothelium-derived hyperpolarizing factor (EDHF; liberated by acetylcholine, 0.01-10 microM) each relaxed endothelium-intact segments of hepatic artery precontracted with phenylephrine. These effects of anandamide, but not those of EDHF, were antagonized by the cannabinoid receptor antagonist, SR141716A (3 microM). 3. The relaxant effects of anandamide were unaffected by a toxin combination (apamin plus charybdotoxin, each 0.3 microM) which abolishes EDHF relaxations and were essentially unchanged in endothelium-denuded arteries. The relaxant effects of anandamide in endothelium-intact arteries were significantly reduced in a physiological salt solution containing 30 mM KCl and abolished when the K+ concentration was raised to 60 mM. 4. Anandamide (10 microM), acetylcholine (1 microM, via release of EDHF) and levcromakalim (10 microM) each markedly hyperpolarized the membrane potential of the smooth muscle cells of endothelium-intact arteries. However, when the endothelium was removed, the hyperpolarizing effects of both anandamide (10 microM) and acetylcholine were essentially abolished whereas those of levcromakalim (10 microM) were unaffected. 5. Under voltage-clamp conditions, anandamide (10 microM) abolished spontaneous transient outward currents (STOCs) in freshly-isolated single hepatic artery cells held at 0 mV but had no effect on the holding current at this potential. In current-clamp mode, the spontaneous hyperpolarizing potentials which corresponded to the STOCs were abolished with no significant change in basal membrane potential. 6. Anandamide (10 microM) abolished the iberiotoxin-sensitive K+ current (IBK(Ca)) produced by caffeine and the corresponding hyperpolarizations generated by this xanthine derivative in current-clamp mode. In contrast, anandamide had no effect on IBK(Ca) generated on exposure to NS1619 (30 microM). 7. It was concluded that anandamide is not EDHF in the rat hepatic artery. Anandamide-induced hyperpolarization is exerted indirectly and requires the presence of the endothelium. Anandamide also acts on the smooth muscle cells to inhibit processes which require functional intracellular calcium stores. This direct action seems more important than membrane hyperpolarization in relaxing phenylephrine-contracted vessels.
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Affiliation(s)
- P M Zygmunt
- School of Biological Sciences, University of Manchester
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