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Scuri R, Mozzachiodi R, Brunelli M. Role for calcium signaling and arachidonic acid metabolites in the activity-dependent increase of AHP amplitude in leech T sensory neurons. J Neurophysiol 2005; 94:1066-73. [PMID: 15872070 DOI: 10.1152/jn.00075.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have revealed a new form of activity-dependent modulation of the afterhyperpolarization (AHP) in tactile (T) neurons of the leech Hirudo medicinalis. The firing of T cells is characterized by an AHP, which is mainly due to the activity of the Na+/K+ ATPase. Low-frequency repetitive stimulation of T neurons leads to a robust increment of the AHP amplitude, which is correlated with a synaptic depression between T neuron and follower cells. In the present study, we explored the molecular cascades underlying the AHP increase. We tested the hypothesis that this activity-dependent phenomenon was triggered by calcium influx during neural activity by applying blockers of voltage-dependent Ca2+ channels. We report that AHP increase requires calcium influx that, in turn, induces release of calcium from intracellular stores so sustaining the enhancement of AHP. An elevation of the intracellular calcium can activate the cytosolic isoforms of the phosholipase A2 (PLA2). Therefore we analyzed the role of PLA2 in the increase of the AHP, and we provide evidence that not only PLA2 but also the recruitment of arachidonic acid metabolites generated by the 5-lipoxygenase pathway are necessary for the induction of AHP increase. These data indicate that a sophisticated cascade of intracellular signals links the repetitive discharge of T neurons to the activation of molecular pathways, which finally may alter the activity of critical enzymes such as the Na+/K+ ATPase, that sustains the generation of the AHP and its increase during repetitive stimulation. These results also suggest the potential importance of the poorly studied 5-lipoxygenase pathway in forms of neuronal plasticity.
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Affiliation(s)
- Rossana Scuri
- Department of Physiology and Biochemistry G. Moruzzi, University of Pisa, Pisa, Italy.
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Sekiguchi F, Miyake Y, Kashimoto T, Sunano S. Unaltered caffeine-induced relaxation in the aorta of stroke-prone spontaneously hypertensive rats (SHRSP). J Smooth Muscle Res 2002; 38:11-22. [PMID: 12199529 DOI: 10.1540/jsmr.38.11] [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: 11/13/2022] Open
Abstract
Caffeine-induced relaxation was studied in aortic segments from Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). Although acetylcholine-induced endothelium-dependent relaxation was impaired in preparations from SHRSP, the relaxation induced by caffeine was identical in both groups. In addition, caffeine-induced relaxation was not affected by removal of the endothelium in either group. The relaxation induced by N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (db-cAMP), a membrane-permeable analog of adenosine 3':5'-cyclic monophosphate (cAMP), was identical in both groups. No significant difference was observed in the increase in cAMP content induced by caffeine in the aortic smooth muscle between the groups, although the basal content was significantly higher in preparations from SHRSP. These results suggest that the relaxation induced by caffeine in these preparations is brought about by its direct effect on smooth muscle and that the response of the smooth muscle to caffeine, including cAMP production, is not altered in preparations from SHRSP compared with those from WKY.
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Affiliation(s)
- Fumiko Sekiguchi
- Department of Anatomy and Physiology, School of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan.
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Frieden M, Graier WF. Subplasmalemmal ryanodine-sensitive Ca2+ release contributes to Ca2+-dependent K+ channel activation in a human umbilical vein endothelial cell line. J Physiol 2000; 524 Pt 3:715-24. [PMID: 10790153 PMCID: PMC2269913 DOI: 10.1111/j.1469-7793.2000.00715.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The whole-cell configuration of the patch clamp technique was used to assess the involvement of ryanodine-sensitive Ca2+ release (RsCR) in histamine-activated Ca2+-dependent K+ (KCa) channels in the human umbilical vein endothelial cell line EA.hy926. Histamine (10 microM) induced a transient outward current that reached 18.9 +/- 5.5 pA pF-1 at +20 mV. This current was diminished by 1 mM tetraethylammonium or 50 nM iberiotoxin, by 90 % and 80 %, respectively, suggesting that this current results from the stimulation of large-conductance KCa (BKCa) channels. In about 50 % of the cells tested, stimulation of RsCR with 200 nM ryanodine initiated a small outward current that was also sensitive to iberiotoxin. Following the ryanodine-mediated RsCR, the potency of 10 microM histamine to activate KCa channels was reduced by about 60 %. In agreement, an inhibition of RsCR with 25 microM ryanodine diminished KCacurrent in response to histamine by about 70 %. The effect of 100 microM histamine on KCa channel activity was not reduced by previous RsCR with 200 nM ryanodine, or by an inhibition of RsCR by 25 microM ryanodine. Histamine (10 microM)-induced Ca2+ elevation was reduced by 30 % following ryanodine-mediated RsCR, whereas no inhibition occurred in the case of 100 microM histamine stimulation. In cells treated with 10 microM nocodazole for 16 h to collapse the superficial endoplasmic reticulum, 200 nM ryanodine failed to initiate any KCa current. Furthermore, the inhibitory effect of previous RsCR on 10 microM histamine-induced KCa current was not obtained in nocodazole-treated cells. Our data suggest that during moderate cell stimulation (10 microM histamine), subplasmalemmal RsCR greatly contributes to the activation of KCa channels in endothelial cells. Thus, the function of the subplasmalemmal Ca2+ control unit (SCCU) described previously must be extended as a regulator for KCa channels.
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Affiliation(s)
- M Frieden
- Department of Medical Biochemistry and Medical Molecular Biology, Karl-Franzens University of Graz, Harrachgasse 21/III, A-8010 Graz, Austria
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Quignard JF, Félétou M, Edwards G, Duhault J, Weston AH, Vanhoutte PM. Role of endothelial cell hyperpolarization in EDHF-mediated responses in the guinea-pig carotid artery. Br J Pharmacol 2000; 129:1103-12. [PMID: 10725258 PMCID: PMC1571951 DOI: 10.1038/sj.bjp.0703175] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Experiments were performed to identify the potassium channels involved in the acetylcholine-induced endothelium-dependent hyperpolarization of the guinea-pig internal carotid artery. Smooth muscle and endothelial cell membrane potentials were recorded in isolated arteries with intracellular microelectrodes. Potassium currents were recorded in freshly-dissociated smooth muscle cells using patch clamp techniques. 2. In single myocytes, iberiotoxin (0.1 microM)-, charybdotoxin (0.1 microM)-, apamin (0.5 microM)- and 4-aminopyridine (5 mM)-sensitive potassium currents were identified indicating the presence of large- and small-conductance calcium-sensitive potassium channels (BK(Ca) and SK(Ca)) as well as voltage-dependent potassium channels (K(V)). Charybdotoxin and iberiotoxin inhibited the same population of BK(Ca) but a conductance specifically sensitive to the combination of charybdotoxin plus apamin could not be detected. 4-aminopyridine (0. 1 - 25 mM) induced a concentration-dependent inhibition of K(V) without affecting the iberiotoxin- or the apamin-sensitive currents. 3. In isolated arteries, both the endothelium-dependent hyperpolarization of smooth muscle and the hyperpolarization of endothelial cells induced by acetylcholine or by substance P were inhibited by 5 mM 4-aminopyridine. 4. These results indicate that in the vascular smooth muscle cells of the guinea-pig carotid artery, a conductance specifically sensitive to the combination of charybdotoxin plus apamin could not be detected, comforting the hypothesis that the combination of these two toxins should act on the endothelial cells. Furthermore, the inhibition by 4-aminopyridine of both smooth muscle and endothelial hyperpolarizations, suggests that in order to observe an endothelium-dependent hyperpolarization of the vascular smooth muscle cells, the activation of endothelial potassium channels is likely to be required.
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Affiliation(s)
- J -F Quignard
- Département de Diabétologie, Institut de Recherches Servier, 92150 Suresnes, France
| | - M Félétou
- Département de Diabétologie, Institut de Recherches Servier, 92150 Suresnes, France
- Author for correspondence:
| | - G Edwards
- Division of Physiology, Pharmacology & Toxicology, School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - J Duhault
- Département de Diabétologie, Institut de Recherches Servier, 92150 Suresnes, France
| | - A H Weston
- Division of Physiology, Pharmacology & Toxicology, School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - P M Vanhoutte
- Institut de Recherches Internationales Servier, 92410 Courbevoie, France
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Wang X, van Breemen C. Depolarization-mediated inhibition of Ca(2+) entry in endothelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H1498-504. [PMID: 10516188 DOI: 10.1152/ajpheart.1999.277.4.h1498] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of extracellular Cl(-) in regulating ACh-induced Ca(2+) entry into freshly isolated rabbit aortic endothelial cells was studied using Ca(2+)-sensitive fluorescence microscopy and patch-clamp electrophysiology. After ACh caused transient Ca(2+) release in Ca(2+)-free medium, readdition of 3 mM Ca(2+) to the bath maintained Ca(2+) entry. Removal of extracellular Cl(-) abolished the plateau phase in Ca(2+) signal and inhibited divalent cation entry. However, in the presence of the K(+) ionophore valinomycin, removal of Cl(-) had no effect on the Ca(2+) plateau. Under current-clamp conditions, substitution of gluconate for Cl(-) induced membrane depolarization. Under voltage clamp, with CsCl in the pipette, ACh activated a slowly developing Cl(-) current, which was blocked by SITS and 5-nitro-2-(3-phenylpropylamino)benzoic acid. Varying the membrane potential by utilizing different extracellular K(+) concentrations in the presence of 5 microM valinomycin demonstrated that depolarization blocked ACh-stimulated Mn(2+) entry. These data suggest that ACh-induced Ca(2+) entry in freshly isolated endothelial cells requires the presence of extracellular Cl(-) to maintain a polarized membrane potential.
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Affiliation(s)
- X Wang
- Vancouver Vascular Biology Research Center, Department of Pharmacology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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Fransen P, Katnik C, Adams DJ. ACh- and caffeine-induced Ca2+ mobilization and current activation in rabbit arterial endothelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H1748-58. [PMID: 9815082 DOI: 10.1152/ajpheart.1998.275.5.h1748] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fura 2 microfluorometry and perforated-patch whole cell recording were carried out simultaneously to investigate the relationship between intracellular free Ca2+ concentration ([Ca2+]i) and membrane current activation in response to ACh and caffeine in freshly dissociated arterial endothelial cells. ACh and caffeine evoked transient increases in [Ca2+]i. The initial increase in [Ca2+]i was accompanied by a transient outward current, which caused membrane hyperpolarization. The amplitudes of the [Ca2+]i transient and outward current were dependent on caffeine concentration (EC50 approximately 1 mM). Cyclopiazonic acid raised resting [Ca2+]i levels by >/=50 nM and failed to completely block caffeine- or ACh-induced [Ca2+]i transients but slowed [Ca2+]i recovery fourfold. The reversal potential of caffeine-induced currents was dependent on external K+ and Cl- concentrations. Caffeine-induced current amplitudes, but not [Ca2+]i responses, were attenuated by external tetraethylammonium, Zn2+, and La3+. A consistent temporal relationship between agonist-activated membrane current and [Ca2+]i increases was not observed, and, in some cases, time differences were greater than expected for simple diffusion of Ca2+ throughout the cell. These results suggest that Ca2+-dependent current activation monitors local [Ca2+]i changes adjacent to the plasmalemma, whereas single-cell photometry provides a measure of global changes in [Ca2+]i.
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Affiliation(s)
- P Fransen
- Department of Physiology and Pharmacology, University of Queensland, Brisbane, Queensland 4072, Australia
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Fukao M, Hattori Y, Kanno M, Sakuma I, Kitabatake A. Sources of Ca2+ in relation to generation of acetylcholine-induced endothelium-dependent hyperpolarization in rat mesenteric artery. Br J Pharmacol 1997; 120:1328-34. [PMID: 9105709 PMCID: PMC1564591 DOI: 10.1038/sj.bjp.0701027] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. The aim of the present study was to identify the sources of Ca2+ contributing to acetylcholine (ACh)-induced release of endothelium-derived hyperpolarizing factor (EDHF) from endothelial cells of rat mesenteric artery and to assess the pathway involved. The changes in membrane potentials of smooth muscles by ACh measured with the microelectrode technique were evaluated as a marker for EDHF release. 2. ACh elicited membrane hyperpolarization of smooth muscle cells in an endothelium-dependent manner. The hyperpolarizing response was not affected by treatment with 10 microM indomethacin, 300 microM NG-nitro-L-arginine or 10 microM oxyhaemoglobin, thereby indicating that the hyperpolarization is not mediated by prostanoids or nitric oxide but is presumably by EDHF. 3. In the presence of extracellular Ca2+, 1 microM ACh generated a hyperpolarization composed of the transient and sustained components. By contrast, in Ca(2+)-free medium, ACh produced only transient hyperpolarization. 4. Pretreatment with 100 nM thapsigargin and 3 microM cyclopiazonic acid, endoplasmic reticulum Ca(2+)-ATPase inhibitors, completely abolished ACh-induced hyperpolarization. Pretreatment with 20 mM caffeine also markedly attenuated ACh-induced hyperpolarization. However, the overall pattern and peak amplitude of hyperpolarization were unaffected by pretreatment with 1 microM ryanodine. 5. In the presence of 5 mM Ni2+ or 3 mM Mn2+, the hyperpolarizing response to ACh was transient, and the sustained component of hyperpolarization was not observed. On the other hand, 1 microM nifedipine had no effect on ACh-induced hyperpolarization. 6. ACh-induced hyperpolarization was nearly completely eliminated by 500 nM U-73122 or 200 microM 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate, inhibitors of phospholipase C, but was unchanged by 500 nM U-73343, an inactive form of U-73122. Pretreatment with 20 nM staurosporine, an inhibitor of protein kinase C, did not modify ACh-induced hyperpolarization. 7. These results indicate that the ACh-induced release of EDHF from endothelial cells of rat mesenteric artery is possibly initiated by Ca2+ release from inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pool as a consequence of stimulation of phospholipid hydrolysis due to phospholipase C activation, and maintained by Ca2+ influx via a Ni(2+)- and Mn(2+)-sensitive pathway distinct from L-type Ca2+ channels. The Ca(2+)-influx mechanism seems to be activated following IP3-induced depletion of the pool.
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Affiliation(s)
- M Fukao
- Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan
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Corda S, Spurgeon HA, Lakatta EG, Capogrossi MC, Ziegelstein RC. Endoplasmic reticulum Ca2+ depletion unmasks a caffeine-induced Ca2+ influx in human aortic endothelial cells. Circ Res 1995; 77:927-35. [PMID: 7554146 DOI: 10.1161/01.res.77.5.927] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Intracellular Ca2+ pools contribute to changes in cytosolic [Ca2+] ([Ca2+]i), which play an important role in endothelial cell signaling. Recently, endothelial ryanodine-sensitive Ca2+ stores were shown to regulate agonist-sensitive intracellular Ca2+ pools. Since caffeine binds the ryanodine Ca2+ release channel on the endoplasmic reticulum in a variety of cell types, we examined the effect of caffeine on [Ca2+]i in human aortic endothelial cell monolayers loaded with the fluorescent probe indo 1. Under baseline conditions, 10 mmol/L caffeine induced a small increase in [Ca2+]i from 86 +/- 10 to 115 +/- 17 nmol/L (mean +/- SEM); this effect was similar to that of 5 mumol/L ryanodine and was unaffected by buffer Ca2+ removal. After depletion of an intracellular Ca2+ store by the irreversible endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (1 mumol/L), ryanodine did not affect [Ca2+]i. In contrast, caffeine induced a large rapid increase in [Ca2+]i (176 +/- 19 to 338 +/- 35 nmol/L, P < .001) after thapsigargin exposure; this effect of caffeine was only observed when extracellular Ca2+ was present. A similar increase in [Ca2+]i was induced by caffeine after depletion of ryanodine- and histamine-sensitive Ca2+ stores or after pretreatment with the endoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 mumol/L). Thus, under baseline conditions the effect of caffeine on [Ca2+]i is similar to that of ryanodine and appears to be due to the release of an intracellular store. However, after depletion of an endoplasmic reticulum Ca2+ store, caffeine, but not ryanodine, stimulates Ca2+ influx, resulting in a large increase in [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Corda
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Md., USA
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Rusko J, Wang X, van Breemen C. Regenerative caffeine-induced responses in native rabbit aortic endothelial cells. Br J Pharmacol 1995; 115:811-21. [PMID: 8548181 PMCID: PMC1908507 DOI: 10.1111/j.1476-5381.1995.tb15005.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
1. Single native aortic endothelial cells obtained by enzymatic dispersion of the rabbit aortic endothelium were held under voltage clamp using patch pipette and whole-cell membrane currents were measured. In parallel experiments performed on cells from the same batches, the free internal calcium concentration, [Ca2+]i, in the cell was estimated by use of the Ca(2+)-sensitive fluorescent dye, fura-2. 2. Caffeine (20 mM) applied to the cell evoked an outward current and an initial peak in [Ca2+]i followed by a lower sustained rise (plateau). Ca(2+)-free, EGTA-containing solution applied outside the cells did not reduce these responses. 3. Following caffeine stimulation there was a biphasic rising phase of outward current both in the presence and absence of extracellular Ca2+. 4. Application of graded doses of caffeine revealed all-or-none type responses of both the outward current and the rise in [Ca2+]i. 5. Preincubation with lower doses of caffeine reduced the magnitude of both the outward current and the [Ca2+]i transient evoked by 20 mM caffeine. 6. Tetraethylammonium (3 mM) applied to the bathing solution blocked unitary and spontaneous transient outward currents (STOCs) stimulated by Ca(2+)-free solution, but only reduced the outward current evoked by caffeine (20 mM). 7. In conclusion, our results reveal the all-or-none nature of Ca2+ release from the endoplasmic reticulum (ER) in native aortic endothelial cells. Lower concentrations of caffeine (0.4-0.5 mM) may deplete intracellular Ca2+ stores. Extracellular Ca2+ is not necessary for maintaining the activity of spontaneous and caffeine-induced outward currents in native aortic endothelial cells. Spontaneous outward currents are believed to represent the sporadic release of calcium from store sites independent of both extracellular Ca2+ and the caffeine-sensitive Ca2+ stores which stimulate the outward current.
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Affiliation(s)
- J Rusko
- Department of Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada
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Graier WF, Simecek S, Bowles DK, Sturek M. Heterogeneity of caffeine- and bradykinin-sensitive Ca2+ stores in vascular endothelial cells. Biochem J 1994; 300 ( Pt 3):637-41. [PMID: 8010945 PMCID: PMC1138215 DOI: 10.1042/bj3000637] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The filling state of Ca2+ stores in endothelial cells regulates Ca2+ entry. The functional relationship between the major Ca2+ stores [i.e. Ins(1,4,5)P3-sensitive (= bradykinin-sensitive stores, 'BsS') and caffeine-sensitive stores] is unknown. In pig right-coronary-artery endothelial cells, caffeine failed to release Ca2+ in 68% of the cells (quiet-responders), but increased bradykinin (Bk)-induced Ca2+ release 2.5-fold. In Bk-pre-stimulated cells, caffeine increased Ca2+ release upon a second stimulation with Bk 3.2-fold. In quiet-responders caffeine alone did not affect net Ca2+ storage, whereas Bk or caffeine followed by Bk decreased the intracellular Ca2+ pool to 45% and 15%, respectively. Blockade of the endoplasmic-reticulum Ca2+ pump by thapsigargin unmasked the effect of caffeine in quiet-responders, resulting in a transient increase in intracellular free Ca2+ concentration ([Ca2+]i). In 37% of the cells caffeine alone transiently increased [Ca2+]i and depleted BsS. This study suggests a heterogeneity in functional organization of endothelial Ca2+ stores. In quiet-responders, caffeine translocates Ca2+ towards the BsS, whereas in overt-responders caffeine empties the BsS.
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Affiliation(s)
- W F Graier
- Vascular Cell Biophysics Laboratory, Dalton Cardiovascular Research Center, University of Missouri, Columbia 65211
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