scholarly journals Effects of platelet-activating factor on the release of arachidonic acid and prostaglandins by rabbit iris smooth muscle. Inhibition by calcium channel antagonists

1985 ◽  
Vol 228 (3) ◽  
pp. 697-706 ◽  
Author(s):  
S Y Yousufzai ◽  
A A Abdel-Latif
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Inositol Phosphates ◽  
Platelet Activating Factor ◽  
Time Dependent ◽  
Dependent Manner ◽  
Rapid Release ◽  
Muscle Inhibition ◽  
Arachidonate Release ◽  
Rabbit Iris

Addition of physiological concentrations (10(-12)-10(-8)M) of platelet-activating factor (PAF) to rabbit iris muscle induced a rapid release (in 15s) of prostaglandin (PG)E2 and 6-oxo-PGF1 alpha, measured by radioimmunoassay and rapid release of 14C-labelled arachidonate and PGE2 in muscle prelabelled with [14C]arachidonic acid, measured by radiochromatography. These PAF actions are concentration- and time-dependent. The effect of PAF on PG release is not mediated through the cyclo-oxygenase pathway. The studies on the properties and mechanism of arachidonate release from phosphatidylinositol and other phospholipids in prelabelled irides by PAF suggest the involvement of a phospholipase A2. This conclusion is supported by the findings: (a) that both the removal of arachidonate and formation of lysophosphatidylinositol, from phosphatidylinositol, by PAF occur concomitantly in a time-dependent manner, (b) that Ca2+ is required for the agonist-induced release of arachidonate and PGE2, and (c) that in contrast to the rapid release of [3H]myo-inositol phosphates by carbachol and other Ca2+-mobilizing agonists previously reported in the iris muscle [Akhtar & Abdel-Latif (1984) Biochem. J. 224, 291-300], PAF (10(-12)-10(-8)M) did not appreciably enhance the release of [14C]myo-inositol phosphates and 32P labelling of phosphatidate and phosphatidylinositol in this tissue. Ca2+-channel antagonists, such as nifedipine, verapamil, diltiazem and manganese inhibited PAF-induced arachidonate and PGE2 release in a dose-dependent manner. K+ depolarization, which causes influx of extracellular Ca2+ in smooth muscle, did not increase the release of arachidonate and PGE2. The ability of Ca2+ antagonists to inhibit arachidonate release by PAF in this tissue probably reflects interference with PAF binding to its receptor. The PAF-induced release of arachidonate and PGE2 occur independently of the cyclo-oxygenase and lipoxygenase pathways. Whether the PAF-induced release of arachidonate and PG in the iris muscle is involved in the pathogenesis of inflammatory and/or physiological reactions in the eye, and how much the inhibitory effects of Ca2+-entry blockers on the PAF actions contribute to the therapeutic use of these drugs, remain to be established.

Mechanism of angiotensin II-induced arachidonic acid metabolite release in aortic smooth muscle cells: involvement of phospholipase D

1997 ◽  
Vol 136 (2) ◽  
pp. 207-212 ◽  
Author(s):  
Junji Shinoda ◽  
Osamu Kozawa ◽  
Atsushi Suzuki ◽  
Yasuko Watanabe-Tomita ◽  
Yutaka Oiso ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Smooth Muscle Cells ◽  
Phospholipase D ◽  
Muscle Cells ◽  
Dependent Manner ◽  
Ang Ii ◽  
Aortic Smooth Muscle Cells ◽  
Aortic Smooth Muscle

Abstract In a previous study, we have shown that angiotensin II (Ang II) activates phosphatidylcholinehydrolyzing phospholipase D due to Ang II-induced Ca2+ influx from extracellular space in subcultured rat aortic smooth muscle cells. In the present study, we have investigated the role of phospholipase D in Ang II-induced arachidonic acid (AA) metabolite release and prostacyclin synthesis in subcultured rat aortic smooth muscle cells. Ang II significantly stimulated AA metabolite release in a concentration-dependent manner in the range between 1 nmol/l and 0·1 μmol/l. d,l-Propranolol hydrochloride (propranolol), an inhibitor of phosphatidic acid phosphohydrolase, significantly inhibited the Ang II-induced release of AA metabolites. The Ang II-induced AA metabolite release was reduced by chelating extracellular Ca2+ with EGTA. Genistein, an inhibitor of protein tyrosine kinases, significantly suppressed the Ang II-induced AA metabolite release. 1,6-Bis-(cyclohexyloximinocarbonylamino)-hexane (RHC-80267), a potent and selective inhibitor of diacylglycerol lipase, significantly inhibited the Ang II-induced AA metabolite release. Both propranolol and RHC-80267 inhibited the Ang II-induced synthesis of 6-keto-prostaglandin F1α, a stable metabolite of prostacyclin. The synthesis was suppressed by genistein. These results strongly suggest that the AA metabolite release induced by Ang II is mediated, at least in part, through phosphatidylcholine hydrolysis by phospholipase D activation in aortic smooth muscle cells. European Journal of Endocrinology 136 207–212

Norepinephrine stimulates arachidonic acid release from vascular smooth muscle via activation of cPLA2

1998 ◽  
Vol 274 (4) ◽  
pp. C1129-C1137 ◽  
Author(s):  
Edward F. LaBelle ◽  
Erzsebet Polyak
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Adrenergic Receptors ◽  
Phospholipase A ◽  
Maximal Effect ◽  
Arachidonic Acid Release ◽  
Tail Artery ◽  
Acid Release ◽  
Arachidonate Release

The mechanism of agonist-activated arachidonate release was studied in segments of rat tail artery. Tail artery segments were prelabeled with [3H]arachidonate and then stimulated with norepinephrine (NE), and the radioactivity of the extracellular medium was determined. NE stimulated arachidonate release from the tissue without increasing arachidonic acid levels within cellular cytosol or crude membranes. About 90% of the extracellular radioactivity was shown to be unmetabolized arachidonate by TLC. Arachidonic acid release was not inhibited by the removal of the endothelium from the artery. NE exerted a half-maximal effect at a concentration of 0.2 μM. NE-stimulated arachidonate release was not inhibited by blockers of phospholipase C (U-73122), diacylglycerol lipase (RHC-80267), secretory phospholipase A2 (manoalide), calcium-insensitive phospholipase A2 (HELSS), or β-adrenergic receptors (propranolol). NE-stimulated arachidonic acid release was inhibited by blockers of cytosolic phospholipase A2(cPLA2) (AACOCF3), α1-adrenergic receptors (prazosin), and specific G proteins (pertussis toxin). This indicated that NE stimulated arachidonate release from vascular smooth muscle via activation of α-adrenergic receptors, either Gi or Go, and cPLA2. NE-activated arachidonic acid release from vascular smooth muscle may play a role in force generation by the tissue. Perhaps arachidonic acid extends the effect of NE on one specific smooth muscle cell to its nearby neighbor cells.

scholarly journals Colon distention induces persistent visceral hypersensitivity by mechanotranscription of pain mediators in colonic smooth muscle cells

2015 ◽  
Vol 308 (5) ◽  
pp. G434-G441 ◽  
Author(s):  
You-Min Lin ◽  
Yu Fu ◽  
Chester C. Wu ◽  
Guang-Yin Xu ◽  
Li-Yen Huang ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Abdominal Pain ◽  
Smooth Muscle Cells ◽  
Mechanical Stress ◽  
Muscle Cells ◽  
Visceral Hypersensitivity ◽  
Time Dependent ◽  
Rat Colon ◽  
Dependent Manner ◽  
Cox 2

Abdominal pain and distention are major complaints in irritable bowel syndrome. Abdominal distention is mainly attributed to intraluminal retention of gas or solid contents, which may cause mechanical stress to the gut wall. Visceral hypersensitivity (VHS) may account for abdominal pain. We sought to determine whether tonic colon distention causes persistent VHS and if so whether mechanical stress-induced expression (mechanotranscription) of pain mediators in colonic smooth muscle cells (SMCs) plays a role in VHS. Human colonic SMCs were isolated and stretched in vitro to investigate whether mechanical stress upregulates expression of the pain mediator cyclooxygenase-2 (COX-2). Rat colon was distended with a 5-cm-long balloon, and gene expression of COX-2, visceromotor response (VMR), and sensory neuron excitability were determined. Static stretch of colonic SMCs induced marked expression of COX-2 mRNA and protein in a force- and time-dependent manner. Subnoxious tonic distention of the distal colon at ∼30–40 mmHg for 20 or 40 min induced COX-2 expression and PGE2 production in colonic smooth muscle, but not in the mucosa layer. Lumen distention also increased VMR in a force- and time-dependent manner. The increase of VMR persisted for at least 3 days. Patch-clamp experiments showed that the excitability of colon projecting sensory neurons in the dorsal root ganglia was markedly augmented, 24 h after lumen distention. Administration of COX-2 inhibitor NS-398 partially but significantly attenuated distention-induced VHS. In conclusion, tonic lumen distention upregulates expression of COX-2 in colonic SMC, and COX-2 contributes to persistent VHS.

Capsazepine, a vanilloid antagonist, abolishes tonic responses induced by 20-HETE on guinea pig airway smooth muscle

2005 ◽  
Vol 288 (3) ◽  
pp. L460-L470 ◽  
Author(s):  
É Rousseau ◽  
Martin Cloutier ◽  
Caroline Morin ◽  
Sonia Proteau
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Eicosatetraenoic Acid ◽  
Dependent Manner ◽  
Release Process ◽  
Concentration Dependent Manner ◽  
Intracellular Ca ◽  
Inotropic Responses ◽  
Enzymatic Pathways

The aim of this study was to delineate the mode of action of 20-hydroxy-eicosatetraenoic acid (20-HETE) in airway smooth muscle (ASM) cells. ASM metabolizes arachidonic acid by various enzymatic pathways, including the cytochrome P-450 (CYP-450) ω-hydroxylase, which leads to the production of 20-HETE, a bronchoconstrictive eicosanoid. The present study demonstrated that 20-HETE induced concentration-dependent tonic responses in ASM, whereas transient responses were recorded in Ca2+-free solution, suggesting an intracellular Ca2+ release process. 20-HETE inotropic responses were abolished by 36 μM 2-aminoethoxydiphenyl borate or 1 μM thapsigargin but were insensitive to 10 μM ryanodine, indicating that inositol triphosphate receptors likely control the release of intracellular Ca2+. Sustained tension, which required Ca2+ entry, was partially blocked by 1 μM nifedipine (an L-type) and 100 μM Gd3+ (a nonselective cationic channel blocker). Moreover, in the absence of selective 20-HETE receptor antagonists, 20-HETE tonic responses were inhibited in a concentration-dependent manner (0.1–10 μM) by capsazepine, a well-characterized vanilloid receptor antagonist. Capsazepine was also observed to reverse cumulative responses to 20-HETE and capsaicin, a TRPV1 agonist. In addition, capsazepine pretreatment largely modified the sustained inotropic responses to 20-HETE, suggesting that 20-HETE cross-reacted with TRPV1 receptors with a low affinity (μM) or that its specific receptor was inhibited by the vanilloid antagonist. Data obtained using RHC-80267, ONO-RS-082, and eicosatetraynoic acid, respective inhibitors of diacylglycerol-lipase, phospholipase A2, and CYP-450 ω-hydroxylase, reveal that intracellular arachidonic acid production and its 20-HETE metabolite may be responsible for the activation of nonselective cationic channels and tonic responses.

scholarly journals Biosynthesis of platelet-activating factor (PAF) in human polymorphonuclear leucocytes. The role of lyso-PAF disposal and free arachidonic acid

1990 ◽  
Vol 268 (1) ◽  
pp. 91-98 ◽  
Author(s):  
M D C Garcia ◽  
S Fernandez-Gallardo ◽  
M A Gijon ◽  
C Garcia ◽  
M L Nieto ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Eicosatetraenoic Acid ◽  
Polymorphonuclear Leucocytes ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Dose Dependent

Theophylline and 1-methyl-3-isobutylxanthine (MIX), compounds that block eicosanoid formation and modulate phospholipase A2 activity, inhibited in a dose-dependent manner the formation of both leukotriene B4 (LTB4) and platelet-activating factor (PAF) by human polymorphonuclear leucocytes (PMN) in response to ionophore A23187. Theophylline and MIX lacked any inhibitory effect on acetyl-CoA: lyso-PAF acetyltransferase activity, which is the rate-limiting step for PAF biosynthesis in PMN. The effect of theophylline and MIX on PAF formation could be reversed by incubating the cells in the presence of 1-10 microM exogenous lyso-PAF. Incubation of PMN homogenates in the presence of unsaturated non-esterified fatty acids resulted in dose-dependent inhibition of the acetyltransferase. This effect was linked to the presence of a free carboxyl group, since both arachidonic acid methyl ester and palmitoyl-arachidonoyl phosphatidylcholine lacked inhibitory activity. This inhibitory effect was also dependent on the number of double bonds, since arachidonic acid (C20:4) and eicosapentaenoic acid (C20:5) displayed maximal effect. Kinetic analysis showed that the effect of arachidonic acid was consistent with competitive inhibition, with a Ki value of about 19 microM. Oxidative metabolites of arachidonic acid showed a lesser inhibitory effect with the following order of potency: arachidonic acid greater than 15-HETE (15-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than LTB4 greater than 5-HETE (5-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than lipoxin A4. Examination of enzymes involved in CoA-dependent acylation revealed a low activity of both arachidonoyl-CoA synthetase and arachidonoyl-CoA: lyso-PAF arachidonoyltransferase. These data indicate a strong influence on PAF biosynthesis of the products of the phospholipase A2 reaction, with lyso-PAF disposal being a critical event for PAF formation, and unsaturated fatty acids acting as feed-back inhibitors. The conversion of arachidonic acid via oxidative metabolism into less active inhibitors of acetyl-CoA:lyso-PAF acetyltransferase seems to be an additional mechanism of modulation of this enzyme activity, linked to the function of lipoxygenases. Finally, the enzyme activities involved in arachidonoyl-CoA-dependent acylation of lyso-PAF show a low efficiency in capturing arachidonic acid.

Abstract 523: Acetylation of Cyclophilin A in Response to Oxidative Stress Enhances Its Expression and Secretion

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Nwe Nwe Soe ◽  
Mark Sowden ◽  
Bradford C Berk
Keyword(s):  
Oxidative Stress ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Time Dependent ◽  
Dependent Manner ◽  
Ang Ii ◽  
Aortic Smooth Muscle ◽  
Dose Dependent ◽  
Cypa Expression

Objective: Cyclophilin A (CyPA) is a Secreted OXidative stress-induced Factor (SOXF) secreted by cardiovascular cells in response to Angiotensin II (Ang II) and reactive oxygen species (ROS). Extracellular CyPA is a proinflammatory mediator that regulates vascular remodeling, abdominal aortic aneurysm, atherosclerosis and cardiac hypertrophy. Post-translational modification of CyPA by acetylation in response to ROS has been described. Moreover, acetylation of CyPA is important in HIV pathogenesis. The mechanism and regulation of CyPA acetylation as well as its role in cardiovascular diseases are currently unknown. We hypothesized that Ang II regulates oxidative stress-induced CyPA acetylation that alters its expression and/or secretion in vascular smooth muscle cells. Methods and results: Ang II (1μM) increased acetylation of CyPA (Acyl-CyPA) in a time dependent manner, with a peak at 8hr (3.5±0.6 fold increase) in rat aortic smooth muscle cells (RASMC) as shown by Western blot. Mouse aortic smooth muscle cells from mice lacking CyPA (CyPA-/-) and wild type controls (WT) confirmed that Ang II induced acetylation reactivity coincided exactly with CyPA reactivity. In AT1R and CyPA cotransfected HeLa cells, Ang II increased Acyl-CyPA in a time dependent manner consistent with that in RASMC. The ROS scavengers Tiron or N-acetylcysteine significantly inhibited Ang II induced Acyl-CyPA in a dose dependent manner in RASMC. Ang II-induced CyPA acetylation was enhanced by 2 hr pretreatment with histone deacetylase inhibitor trichostatin (TSA) or sirtinol in a dose dependent manner. Similarly, Ang II-induced CyPA secretion was enhanced by pretreatment with TSA (1μM) in a time dependent manner. Moreover, acetyltransferase p300 and PCAF (p300/CBP-asociated factor) inhibitor anacardic acid (6-nonadecyl salicylic acid) dramatically inhibited CyPA expression, and Ang II induced Acyl-CyPA in a dose dependent manner. Conclusion: These results suggest that Ang II-induced CyPA acetylation is oxidative stress dependent, and that acetylation enhanced CyPA expression and secretion. Detailed mechanistic studies of the regulation of CyPA acetylation will help to identify a future therapeutic target for CyPA regulated cardiovascular diseases.

Leukotriene D4 and platelet-activating factor – acether antagonists on allergic and arachidonic acid-induced reactions in guinea pig airways

1989 ◽  
Vol 67 (5) ◽  
pp. 483-490 ◽  
Author(s):  
John F. Burka ◽  
Heather Briand ◽  
Peter Scott-Savage ◽  
Franco M. Pasutto
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Guinea Pig ◽  
Receptor Antagonist ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Leukotriene D4 ◽  
Total Inhibition ◽  
Low Concentrations ◽  
Lung Parenchymal Strip

Arachidonic acid (AA) and ovalbumin (OA) were used to induce contractions of sensitized guinea pig tracheal spiral (indomethacin-pretreated) and lung parenchymal strip preparations. This model was used to examine the properties of three leukotriene (LT) D4 antagonists and a platelet-activating factor (PAF)–acether receptor antagonist. The three LTD4 antagonists, L-649,923, FPL 57231, and LY163443, inhibited AA-induced contractions of indomethacin-pretreated tracheal spirals selectively. The PAF–acether antagonist, L-652,731, did not inhibit AA-induced contractions of either trachea or parenchyma. This confirmed that AA-induced contractions of trachea involved release and activity of LTD4. The LTD4 antagonists and L-652,731 partially inhibited OA-induced contractions of both trachea and parenchyma. When L-649,923 and L-652,731 or FPL 57231 and L-652,731 were combined, an additive inhibitory effect on OA-induced contractions was observed. When LY163443 and L-652,731 were combined, the inhibitory effect was synergistic. This may be due to the additional effect of LY163443 to inhibit phosphodiesterase. Total inhibition of OA-induced contractions was obtainable with relatively low concentrations when a LTD4 and PAF–acether antagonist were combined. These results suggested that LTD4 and PAF–acether may be the two major mediators in our model of allergic bronchospasm. The LTD4 and PAF–acether antagonists had the capacity to decrease baseline tone, even on tissues that were already relaxed with indomethacin, suggesting that LTD4 and PAF–acether may contribute to intrinsic tone in airway smooth muscle.Key words: leukotriene D4, platelet-activating factor, airway smooth muscle, antagonists, allergic bronchospasm.

scholarly journals Angiotensin II stimulates phosphorylation of high-molecular-mass cytosolic phospholipase A2 in vascular smooth-muscle cells

1994 ◽  
Vol 299 (1) ◽  
pp. 197-201 ◽  
Author(s):  
G N Rao ◽  
B Lassègue ◽  
R W Alexander ◽  
K K Griendling
Keyword(s):  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Time Dependent ◽  
Arachidonic Acid Release ◽  
Acid Release

Phospholipase A2 (PLA2) may be one of the major components involved in cell signalling and proliferation, as suggested by recent studies. In this paper we show that the potent vasoconstrictor and hypertrophic agent angiotensin II (AngII) activates cytosolic PLA2 (cPLA2) in vascular smooth-muscle cells. AngII induced a rapid time-dependent release of [3H]arachidonic acid from prelabelled cells that was inhibited by mepacrine, a PLA2 inhibitor. AngII treatment of intact cells also activated a cPLA2, as measured in cell-free extracts by the release of radiolabelled arachidonic acid from exogenously added 1-stearoyl-2-[1-14C]arachidonoyl phosphatidylcholine. This AngII-stimulated cPLA2 activity was also significantly inhibited by mepacrine. AngII induced a rapid and time-dependent increase in cPLA2 phosphorylation. Protein kinase C (PKC) depletion inhibited both AngII-induced [3H]arachidonic acid release and cPLA2 phosphorylation. Together, these results suggest strongly that (1) AngII phosphorylates and activates cPLA2 in a PKC-dependent manner, and that (2) cPLA2 mediates the AngII-induced [3H]arachidonic acid release in vascular smooth-muscle cells.

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