Cultured bovine coronary arterial endothelial cells synthesize HETEs and prostacyclin

GPR40 is a low-affinity epoxyeicosatrienoic acid receptor in vascular cells

Endothelium-derived epoxyeicosatrienoic acids (EETs) have numerous vascular activities mediated by G protein-coupled receptors. Long-chain free fatty acids and EETs activate GPR40, prompting us to investigate the role of GPR40 in some vascular EET activities. 14,15-EET, 11,12-EET, arachidonic acid, and the GPR40 agonist GW9508 increase intracellular calcium concentrations in human GPR40-overexpressing HEK293 cells (EC₅₀ = 0.58 ± 0.08 μm, 0.91 ± 0.08 μm, 3.9 ± 0.06 μm, and 19 ± 0.37 nm, respectively). EETs with cis- and trans-epoxides had similar activities, whereas substitution of a thiirane sulfur for the epoxide oxygen decreased the activities. 8,9-EET, 5,6-EET, and the epoxide hydrolysis products 11,12- and 14,15-dihydroxyeicosatrienoic acids were less active than 11,12-EET. The GPR40 antagonist GW1100 and siRNA-mediated GPR40 silencing blocked the EET- and GW9508-induced calcium increases. EETs are weak GPR120 agonists. GPR40 expression was detected in human and bovine endothelial cells (ECs), smooth muscle cells, and arteries. 11,12-EET concentration-dependently relaxed preconstricted coronary arteries; however, these relaxations were not altered by GW1100. In human ECs, 11,12-EET increased MAP kinase (MAPK)-mediated ERK phosphorylation, phosphorylation and levels of connexin-43 (Cx43), and expression of cyclooxygenase-2 (COX-2), all of which were inhibited by GW1100 and the MAPK inhibitor U0126. Moreover, siRNA-mediated GPR40 silencing decreased 11,12-EET-induced ERK phosphorylation. These results indicated that GPR40 is a low-affinity EET receptor in vascular cells and arteries. We conclude that epoxidation of arachidonic acid to EETs enhances GPR40 agonist activity and that 11,12-EET stimulation of GPR40 increases Cx43 and COX-2 expression in ECs via ERK phosphorylation.

Design, Synthesis and Cellular Characterization of a Dual Inhibitor of 5-Lipoxygenase and Soluble Epoxide Hydrolase

The arachidonic acid cascade is a key player in inflammation, and numerous well-established drugs interfere with this pathway. Previous studies have suggested that simultaneous inhibition of 5-lipoxygenase (5-LO) and soluble epoxide hydrolase (sEH) results in synergistic anti-inflammatory effects. In this study, a novel prototype of a dual 5-LO/sEH inhibitor KM55 was rationally designed and synthesized. KM55 was evaluated in enzyme activity assays with recombinant enzymes. Furthermore, activity of KM55 in human whole blood and endothelial cells was investigated. KM55 potently inhibited both enzymes in vitro and attenuated the formation of leukotrienes in human whole blood. KM55 was also tested in a cell function-based assay. The compound significantly inhibited the LPS-induced adhesion of leukocytes to endothelial cells by blocking leukocyte activation.

Influence of intraluminal acidification on esophageal secondary peristalsis in humans

BACKGROUND

Secondary peristalsis contributes to clearance of retained refluxate or material from the esophagus.

AIM

The goal of our study was to investigate the effects of hydrochloric acid (HCl) on physiological characteristics of esophageal secondary peristalsis in healthy adults.

METHODS

After recording esophageal motility baseline for primary peristalsis, secondary peristalsis was stimulated with slow and rapid air injections in the mid-esophageal in 16 healthy subjects. Normal saline and HCl (0.1 N) were separately infused into the esophagus to test whether they had effects on secondary peristalsis.

RESULTS

After infusion of HCl, the threshold volume to generate secondary peristalsis was significantly decreased during rapid and slow air infusions (both P < 0.05). The frequency of secondary peristalsis was increased after HCl infusion (90 % [72.5-100 %] versus 85 % [72.5-90 %], P = 0.002). Infusion of HCl significantly increased pressure wave amplitude during rapid and slow air infusions (both P < 0.05). Infusion of saline did not affect any parameters of secondary peristalsis. The occurrence of heartburn was generated in 7 of 16 subjects after infusion of HCl with an increase in visual analogue scale score (12.5).

CONCLUSIONS

Our data show that acute esophageal acid infusion enhances sensitivity of distension-induced secondary peristalsis and enhances secondary peristaltic activity. The study supports the evidence of the presence of acid-sensitive afferents in the modulation of distension-induced secondary peristalsis in humans.

Patients with esophageal motility disorders show distinct patterns based on axial force measurements

BACKGROUND

Using manometry, the classification of motility-related disorders in the esophagus is vague and overlapping. We present a new method, which combines manometry and axial force measurements in a single catheter.

AIM

The aim was to examine the manometric and axial force recordings during swallows.

METHODS

Recordings from 20 patients suffering from diffuse esophageal spasms (DES) (8), achalasia (5) and other diseases including gastro-oesophageal reflux (7) were compared to recordings made in ten healthy subjects. The probe was capable of measuring axial force 6.5-cm proximal to the lower esophageal sphincter (LES) and pressures 8-, 10- and 12-cm proximal to the LES. After insertion, five dry and five wet swallows were made. Swallows were repeated with 0, 2, 4 and 6 ml of water in a bag mounted distal to the axial force recording site. Each contraction was analysed for duration and amplitude, and was categorised according to its configuration.

RESULTS

The number of failed contractions measured with axial force was lower for the achalasia (P < 0.001) and DES groups (P < 0.001) compared to the healthy volunteers. The number of multi-peaked contractions was unchanged for the achalasia and DES groups while it increased for the group of healthy volunteers. On several occasions a negative traction force was encountered though the manometric pattern appeared normal.

CONCLUSIONS

Measurements of axial force generated by primary peristalsis provide additional information about esophageal neuromuscular function in different diseases that is not demonstrable with manometry alone.

ZLJ-6, a novel COX/5-LOX inhibitor, attenuates TNF-α-induced endothelial E-selectin, ICAM-1 and VCAM-1 expression and monocyte-endothelial interactions via a COX/5-LOX-independent mechanism

Nonsteroidal anti-inflammatory drugs (NSAIDs) are previously found to possess prostaglandin and leukotriene-independent anti-inflammatory effect. The aim of the present study was to investigate the prostaglandin and leukotriene-independent anti-inflammatory effect of an imidazolone COX/5-LOX inhibitor ZLJ-6 and the underlying mechanism. Pretreatment human umbilical vein endothelial cells (HUVECs) with ZLJ-6 (3, 10 and 30 μM) concentration-dependently decreased TNF-α-induced monocyte-endothelial interactions in both static and dynamic conditions whereas no effect was found after pretreatment with the COX-2 inhibitor celecoxib (30 μM), 5-LOX inhibitor zileuton (30 μM) and the combination of them. ZLJ-6 also attenuated expression of E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cytoadhesion molecule-1 (VCAM-1) on TNF-α-induced HUVECs. A further analysis indicated that ZLJ-6 attenuated TNF-α-induced nuclear translocation of NF-κB, IκB phosphorylation, IκB kinase β (IKKβ) activity, and subsequent NF-κB-DNA complex formation, suggesting that NF-κB pathway was involved in TNF-α-induced inflammation. However, ZLJ-6 did not affect TNF-α-induced extracellular signal-regulated kinases (ERK1/2), c-Jun N-terminal kinases (JNK) and p38 phosphorylation. Taken together, our results indicated that ZLJ-6 potently inhibited TNF-α-induced monocyte-endothelial interactions and adhesion molecule (E-selectin, ICAM-1 and VCAM-1) expression and these effects were mediated by NF-κB signaling pathway rather than its primary pharmacological target COX-2 or 5-LOX.

20-Iodo-14,15-epoxyeicosa-8(Z)-enoyl-3-azidophenylsulfonamide: photoaffinity labeling of a 14,15-epoxyeicosatrienoic acid receptor

Endothelium-derived epoxyeicosatrienoic acids (EETs) relax vascular smooth muscle by activating potassium channels and causing membrane hyperpolarization. Recent evidence suggests that EETs act via a membrane binding site or receptor. To further characterize this binding site or receptor, we synthesized 20-iodo-14,15-epoxyeicosa-8(Z)-enoyl-3-azidophenylsulfonamide (20-I-14,15-EE8ZE-APSA), an EET analogue with a photoactive azido group. 20-I-14,15-EE8ZE-APSA and 14,15-EET displaced 20-(125)I-14,15-epoxyeicosa-5(Z)-enoic acid binding to U937 cell membranes with K(i) values of 3.60 and 2.73 nM, respectively. The EET analogue relaxed preconstricted bovine coronary arteries with an ED(50) comparable to that of 14,15-EET. Using electrophoresis, 20-(125)I-14,15-EE8ZE-APSA labeled a single 47 kDa band in U937 cell membranes, smooth muscle and endothelial cells, and bovine coronary arteries. In U937 cell membranes, the 47 kDa radiolabeling was inhibited in a concentration-dependent manner by 8,9-EET, 11,12-EET, and 14,15-EET (IC(50) values of 444, 11.7, and 8.28 nM, respectively). The structurally unrelated EET ligands miconazole, MS-PPOH, and ketoconazole also inhibited the 47 kDa labeling. In contrast, radiolabeling was not inhibited by 8,9-dihydroxyeicosatrienoic acid, 5-oxoeicosatetraenoic acid, a biologically inactive thiirane analogue of 14,15-EET, the opioid antagonist naloxone, the thromboxane mimetic U46619, or the cannabinoid antagonist AM251. Radiolabeling was not detected in membranes from HEK293T cells expressing 79 orphan receptors. These studies indicate that vascular smooth muscle, endothelial cells, and U937 cell membranes contain a high-affinity EET binding protein that may represent an EET receptor. This EET photoaffinity labeling method with a high signal-to-noise ratio may lead to new insights into the expression and regulation of the EET receptor.

Normal values for manometry performed with swallows of viscous test material

OBJECTIVE

Esophageal function testing with combined multichannel intraluminal impedance and manometry (MII-EM) is performed using ten 5-ml liquid and viscous swallows. Diagnosis of bolus transit abnormalities identified by impedance is based on both liquid and viscous swallows. Manometric diagnosis is based solely on liquid swallows. The aim of this study was to establish the normal values for manometry performed with a viscous bolus.

MATERIAL AND METHODS

MII-EM studies performed in 80 healthy volunteers were analyzed. The analyzed manometric parameters included contraction amplitude and duration, distal onset velocity and lower esophageal sphincter (LES) residual pressure.

RESULTS

Mean distal esophageal amplitude (DEA) (mmHg) for liquid swallows was 104 (+/-44) and for viscous swallows 102 (+/-51). Viscous versus liquid swallows were characterized by higher contraction amplitudes at 10 cm above the LES, slower distal onset velocities and higher LES residual pressures. Duration of contractions was similar between liquid and viscous swallows. Upper normal limits for viscous swallows were: 204 mmHg for DEA (mean+/-2 SDs); 6 ineffective and 1 simultaneous swallows and 11.7 mmHg for LES residual pressure (95th percentile).

CONCLUSIONS

Based on our results, the following values should be considered normal for manometry performed with viscous swallows: <or= 60% ineffective contractions, <or= 10% simultaneous contractions and DEA <204 mmHg, LES residual pressure <or= 11.7 mmHg.

Impedance manometry with viscous test solution increases detection of esophageal function defects compared to liquid swallows

OBJECTIVE

Multichannel intraluminal impedance and manometry (MII-EM) is performed using ten 5-ml swallows each of a liquid and a viscous solution. However, the manometric diagnosis is based solely on results from the 10 liquid swallows. The aim of this study was to compare esophageal function evaluated with 10 liquid versus 10 viscous swallows using combined MII-EM in patients with various symptoms.

MATERIAL AND METHODS

Consecutive studies performed in 300 patients (211F, mean age 54.5 years) were analyzed. The manometric diagnoses were separated into normal and abnormal manometry. MII findings included the number of complete and incomplete transits and total bolus transit time.

RESULTS

Manometric diagnosis for liquid and viscous solutions was consistent in 231 (77%) and inconsistent in 69 (23%) patients (p<0.0001). Overall, the number of manometric abnormalities detected with the viscous solution (n=91, 30.3%) was significantly higher (p=0.03) than that detected with the liquid solution (n=60, 20%). Impedance diagnosis for the viscous and liquid solutions was consistent in 238 (79.3%) patients and inconsistent in 62 (20.7%) patients (p<0.0001). Among those 62 patients, 36 (58.1%) had complete bolus transit with the liquid solution and incomplete bolus transit with the viscous solution, and 26 (41.9%) had incomplete bolus transit with the liquid solution and complete transit with the viscous solution (p=0.46). Overall, there was no significant difference between the number of bolus transit abnormalities for the liquid (n=75, 25%) and viscous solutions (n=85, 28.3%, p=0.47).

CONCLUSIONS

Our results indicate that a viscous solution detects significantly more manometric abnormalities than a liquid solution. Impedance diagnosis has greater similarity for both the liquid and viscous solutions.

Arachidonic acid metabolites as endothelium-derived hyperpolarizing factors

The endothelium regulates vascular tone through the release of a number of soluble mediators, including NO, prostaglandin I2, and endothelium-derived hyperpolarizing factor. Epoxyeicosatrienoic acids are cytochrome P450 epoxygenase metabolites of arachidonic acid. They are synthesized by the vascular endothelium and open calcium-activated potassium channels, hyperpolarize the membrane, and relax vascular smooth muscle. Endothelium-dependent relaxations to acetylcholine, bradykinin, and shear stress that are not inhibited by cyclooxygenase and NO synthase inhibitors are mediated by the endothelium-derived hyperpolarizing factor. In arteries from experimental animals and humans, the non-NO, non-prostaglandin-mediated relaxations and endothelium-dependent hyperpolarizations are blocked by cytochrome P450 inhibitors, calcium-activated potassium channel blockers, and epoxyeicosatrienoic acid antagonists. Acetylcholine and bradykinin stimulate epoxyeicosatrienoic acid release from endothelial cells and arteries. These findings indicate that epoxyeicosatrienoic acids act as endothelium-derived hyperpolarizing factors and regulate arterial tone.

Relationship between pressure wave amplitude and esophageal bolus clearance assessed by combined manometry and multichannel intraluminal impedance measurement

OBJECTIVES

Esophageal wave amplitude is an important determinant of esophageal clearance. A threshold of 30 mmHg is widely accepted as the threshold for effective clearance in the distal esophagus. However, the precise relationship between wave amplitude and clearance has received relatively little attention. The aim of this study was to assess the impact of peristaltic wave amplitude on esophageal volume clearance using multiple intraluminal impedance (MII) measurement.

METHODS

Concurrent manometry and MII were performed on 42 healthy asymptomatic volunteers and 13 patients with ineffective esophageal motility. Esophageal motility was measured at four sites 5-cm apart, starting 2 cm above the lower esophageal sphincter. MII was measured at corresponding sites with electrodes incorporated into the manometric assembly. Ten 5-mL liquid (saline) boluses and ten 5-mL low impedance viscous boluses were tested in each subject. Pressure wave amplitude was determined at each site as well as peristaltic success of the responses. Bolus clearance was measured from individual recording segment and from the esophagus as a whole.

RESULTS

The proportion of liquid boluses cleared at each site was directly related to wave amplitude and did not increase significantly above a threshold of 25 mmHg in the proximal esophagus, 22 mmHg in the mid-esophagus, and 30 mmHg in the distal esophagus. Corresponding wave amplitudes for total esophageal clearance were 35-40 mmHg. There was a good correlation between the wave amplitude at one site of the esophagus and those of the rest of the esophagus. For both liquid and viscous boluses, the likelihood of impaired clearance was directly related to the number of segments with hypotensive pressure waves.

CONCLUSION

The findings confirm the validity of the wave amplitude threshold required for effective liquid bolus clearance and have established the amplitude threshold for clearance of viscous boluses. However, the number of hypotensive pressure waves required for the definition of ineffective motility may be too low.

Licofelone, a novel 5-LOX/COX-inhibitor, attenuates leukocyte rolling and adhesion on endothelium under flow

The main mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs) is the inhibition of cycloxygenases COX-1 and COX-2. During recent years, combined 5-LOX/COX-inhibition, interfering with the biosynthesis of both prostaglandins and leukotrienes (LTs), has emerged as a possibility to avoid side effects related to COX-inhibition. The aim of the present study was to investigate if there is a contribution of mechanisms other than the reduction of inflammatory prostaglandins and leukotrienes to the anti-inflammatory effect of the LOX/COX inhibitor licofelone. In a flow chamber assay, licofelone (10-30 microM) dose-dependently decreased both the rolling and adhesion of leukocytes on endothelial cells (EC). In contrast, no effects were found after treatment of EC with the unselective COX-1/COX-2 inhibitor indomethacin (30 microM), the potent and selective 5-LOX inhibitor, ZD-2138 (30 microM), the mainly COX-2 inhibitor aceclofenac (30 microM), the selective COX-2 inhibitor celecoxib (30 microM) and the combination of ZD-2138 with the selective COX-2 inhibitor celecoxib (30 microM). In the presence of licofelone (30 microM) the expression of E-selectin mRNA in cytokine-stimulated EC was attenuated, whereas no NSAID (30 microM) tested showed any effect on E-selectin expression. Moreover, licofelone treatment (30 microM) attenuated expression of VCAM-1 and ICAM-1 on inflammatory EC. The effect of licofelone on leukocyte recruitment was also evaluated in vivo. Using a mouse peritonitis model it was found that leukocyte accumulation was markedly reduced in licofelone treated animals (100mg/kg) compared to untreated mice. Thus, the novel 5-LOX/COX inhibitor licofelone possesses anti-inflammatory activity that, in addition to COX/LOX inhibition, involves effects on leukocyte-endothelial interactions.

Assessment of oesophageal motor function using combined perfusion manometry and multi-channel intra-luminal impedance measurement in normal subjects

Multichannel intraluminal impedance (MII) is being used increasingly to assess oesophageal bolus clearance. However, there is no good standardization of the impedance parameters that define 'effective bolus clearance'. The aim of this study was to define these important impedance parameters and to determine their normal values. Concurrent perfusion manometry and MII were performed in 42 healthy volunteers. Ten, 5-mL liquid (saline) boluses and then, 10x5-mL low impedance viscous boluses were tested in each subject in the right-lateral position. Normal values for bolus presence time (BPT) at each site and total bolus transit time (TBTT) were determined from either 'normal' peristaltic responses (amplitude>or=30 mmHg in distal oesophagus) or 'super-normal' peristaltic responses (amplitudes>or=50 mmHg at all sites). The relationship between BPT and TBTT within a response and per-individual performance was determined. A total of 840 swallows of liquids and viscous responses were analysed. BPT and TBTT of viscous swallows were longer than those for liquids. Non-peristaltic responses were significantly more likely not to clear a viscous than a liquid bolus. Within a response, the number of sites with prolonged BPT strongly predicted the incidence of prolonged TBTT. Using impedance criteria, normal oesophageal bolus clearance is defined when an individual completely clears at least 70% of liquid responses and at least 60% of viscous responses. This study provides normal values for impedance measurement of bolus clearance when combined with perfusion manometry. These values will allow standardization of impedance application in oesophageal function testing, in both research and clinical setting.

Low-density lipoprotein inhibits receptor-mediated prostaglandin synthesis without affecting calcium and arachidonic acid mobilization in human endothelial cells

Vascular serotonin 5-HT1 receptors have quiescent constrictor activity that is activated by other vasoactive agents such as histamine. Previously, we observed that the 5-HT1-selective agonist 5-carboxamidotryptamine (5-CT) potentiated histamine-stimulated arachidonic acid (AA) mobilization and prostaglandin production in human aortic endothelial cells (HAEC). In the present study, 5-CT was found to potentiate histamine-stimulated calcium mobilization but had no effect on intracellular calcium when added alone. Treatment of HAEC with human low-density lipoprotein (LDL) for 20 hours inhibited the histamine- plus 5-CT-stimulated production of prostaglandin F2alpha (PGF2alpha) and the prostacyclin metabolite 6-keto-PGF1alpha. However, the effects of histamine and histamine potentiation by 5-CT on intracellular Ca mobilization and AA release were resistant to LDL treatment. Conversely, the subsequent receptor-independent conversion of AA to prostaglandins was inhibited by LDL. These results demonstrate that histamine and serotonin receptor activity, measured as the stimulation of Ca and AA mobilization, is resistant to LDL exposure under mild oxidizing conditions, whereas the receptor-independent synthesis of prostaglandins is inhibited by LDL. The results also suggest that the LDL-stimulated mobilization of cellular AA is responsible for the LDL-mediated inhibition of prostaglandin synthesis. These findings suggest a mechanism by which LDL and/or atherosclerosis could promote the vascular liberation of AA that is not converted to endothelium-derived prostaglandins and is therefore available as substrate for the production of other eicosanoids.

Stable 5,6-epoxyeicosatrienoic acid analog relaxes coronary arteries through potassium channel activation

5,6-epoxyeicosatrienoic acid (5,6-EET) is a cytochrome P450 epoxygenase metabolite of arachidonic acid that causes vasorelaxation. However, investigations of its role in biological systems have been limited by its chemical instability. We developed a stable agonist of 5,6-EET, 5-(pentadeca-3(Z),6(Z),9(Z)-trienyloxy)pentanoic acid (PTPA), in which the 5,6-epoxide was replaced with a 5-ether. PTPA obviates chemical and enzymatic hydrolysis. In bovine coronary artery rings precontracted with U46619, PTPA (1 nmol/L to 10 micromol/L) induced concentration-dependent relaxations, with maximal relaxation of 86+/-5% and EC50 of 1 micromol/L. The relaxations were inhibited by the cyclooxygenase inhibitor indomethacin (10 micromol/L; max relaxation 43+/-9%); the ATP-sensitive K+ channel inhibitor glybenclamide (10 micromol/L; max relaxation 49+/-6%); and the large conductance calcium-activated K+ channel inhibitor iberiotoxin (100 nmol/L; max relaxation 38+/-6%) and abolished by the combination of iberiotoxin with indomethacin or glybenclamide or increasing extracellular K+ to 20 mmol/L. Whole-cell outward K+ current was increased nearly 6-fold by PTPA (10 micromol/L), which was also blocked by iberiotoxin. Additionally, we synthesized 5-(pentadeca-6(Z),9(Z)-dienyloxy)pentanoic acid and 5-(pentadeca-3(Z),9(Z)-dienyloxy)pentanoic acid (PDPA), PTPA analogs that lack the 8,9 or 11,12 double bonds of arachidonic acid and therefore are not substrates for cyclooxygenase. The PDPAs caused concentration-dependent relaxations (max relaxations 46+/-13% and 52+/-7%, respectively; EC50 1micromol/L), which were not altered by glybenclamide but blocked by iberiotoxin. These studies suggested that PTPA induces relaxation through 2 mechanisms: (1) cyclooxygenase-dependent metabolism to 5-ether-containing prostaglandins that activate ATP-sensitive K+ channels and (2) activation of smooth muscle large conductance calcium-activated K+ channels. PDPAs only activate large conductance calcium-activated K+ channels.

Free radicals and lipid signaling in endothelial cells

Lipid mediators generated by oxidative pathways play essential roles in vascular homeostasis and disease through activating signal transduction pathways that control a variety of cellular functions, including vascular tone, gene expression, and leukocyte and platelet activation. Several enzyme families generate oxidized lipids, and a number of these are either constitutively expressed or inducible in the endothelium, including prostaglandin H synthases, lipoxygenases, and cytochrome P450 isoforms. Mediators generated by these enzymes are predominantly arachidonate-derived and include lipid hydroxides, epoxides, hydroperoxides, and prostanoids. These enzymes may also generate low levels of lipid-derived radicals in the vasculature following escape of substrate radicals from the active site. Lipid oxidation enzymes are often up-regulated in atherosclerosis and hypertension, with several lines of evidence suggesting that they play a central role in the pathogenesis of the disease process itself. This review will describe the isoforms of lipid oxidation enzymes present in endothelial cells focusing on their physiological functions and proposed roles in initiation and progression of vascular disease.

Effects of position on oesophageal function: studies using combined manometry and multichannel intraluminal impedance

Multichannel intraluminal impedance (MII) allows assessment of intraoesophageal bolus transit. In the supine position, bolus transit is produced almost exclusively by peristaltic contractions; in the upright position, gravity also contributes to bolus transit. MII and peristaltic pressures were measured in four positions (0, 30, 60 and 90 degrees ) using ten swallows (5 cc each) of both water and viscous liquid with body position determined by random choice. Tracings were analysed for total bolus transit time: time interval between bolus entry at 20 cm above and bolus exit at 5 cm above the lower oesophageal sphincter (LOS) and contraction amplitudes at 5 and 10 cm above the LOS. Statistical comparison of mean values of all four body positions was done using anova and Bonnferoni post-test. Ten normal subjects (five females and five males, age 24-45 years) completed the study. At each body position, liquid material transited faster (P < 0.001) than viscous material. Both liquid and viscous materials transited at lower inclinations (0 and 30 degrees ) significantly slower than at higher inclinations (60 and 90 degrees ). There was an almost perfect inverse linear correlation between angle of inclination and bolus transit time for both liquid (r = -0.99) and viscous (r = -1.00) boluses (Spearman correlation r > 0.99 and P < 0.02 for both substances). Contraction amplitudes for liquid vs viscous material were not significantly different at a given degree of inclination. Mean distal oesophageal amplitude declined with increasing inclination. Combined MII-OM identifies and quantifies the effects of gravity on the dichotomy between specific pressures measured by OM and function assessed as transit measured by MII.

Effects of epoxyeicosatrienoic acids on polymorphonuclear leukocyte function

During periods of ischemia and vascular injury, factors are released which recruit monocytes and polymorphonuclear leukocytes (PMNs) to the site of injury by promoting adherence to the endothelium and transmigration across the endothelial cell (EC) layer. During coronary artery stenosis, we have shown that the endothelium-derived, cytochrome P450 metabolites of arachidonic acid, the epoxyeicosatrienoic acids (EETs), are elevated. Therefore, we examined if the EETs could stimulate PMN adherence to cultured ECs. Pretreatment of ECs with EETs for either 30 min or 4 hr did not alter the adherence of 51Cr-labelled PMNs to ECs while phorbol myristate acetate (PMA) produced a 4-fold increase in PMN adherence. The combination of EETs and PMA did not significantly augment or diminish PMA-induced PMN adherence to ECs. When ECs and 51Cr-labelled PMNs were coincubated, treatment with EETs alone did not alter PMN adherence. However, when EETs and PMA were added together during the coincubation of ECs and 51Cr-labelled PMNs, the EETs produced a concentration-related decrease in PMN adherence. Microscopic analysis of the culture media bathing the cells revealed aggregates of the labeled PMNs. We examined the effects of the EETs on PMN aggregation. 8,9-EET (10, 50, and 100 microM) increased PMN aggregation (7 +/- 3, 35 +/- 10, and 65 +/- 11%) and intracellular calcium by 1.7 +/- 0.5, 4.7 +/- 1.4, and 6.8 +/- 2.3-fold above basal. 5,6-, 11,2- and 14,15-EETs also stimulated aggregation. FMLP stimulated the production of superoxide; however, 8,9-EET did not. These observations indicate that the decrease in PMN adherence observed in the coincubation experiment is the result of EET-induced PMN aggregation. Given the increase in EET production during coronary artery stenosis, these data may provide insight into their potential biological significance during myocardial ischemia and vascular injury.

A natural protective mechanism against hyperglycaemia in vascular endothelial and smooth-muscle cells: role of glucose and 12-hydroxyeicosatetraenoic acid

Bovine aortic endothelial and smooth-muscle cells down-regulate the rate of glucose transport in the face of hyperglycaemia, thus providing protection against deleterious effects of increased intracellular glucose levels. When exposed to high glucose concentrations these cells reduced the mRNA and protein content of their typical glucose transporter, GLUT-1, as well as its plasma-membrane abundance. Inhibition of the lipoxygenase (LO) pathway, and particularly 12-LO, reversed this glucose-induced down-regulatory process and restored the rate of hexose transport to the level seen in vascular cells exposed to normal glucose levels. This reversal was accompanied by increased levels of GLUT-1 mRNA and protein, as well as of its plasma-membrane content. Exposure of the vascular cells to elevated glucose concentrations increased by 2-3-fold the levels of cell-associated and secreted 12-hydroxyeicosatetraenoic acid (12-HETE), the product of 12-LO. Inhibition of 15- and 5-LO, cyclo-oxygenases 1 and 2, and eicosanoid-producing cytochrome P450 did not modify the hexose-transport system in vascular cells. These results suggest a role for HETEs in the autoregulation of hexose transport in vascular cells. 8-Iso prostaglandin F(2alpha), a non-enzymic oxidation product of arachidonic acid, had no effect on the hexose-transport system in vascular cells exposed to hyperglycaemic conditions. Taken together, these findings show that hyperglycaemia increases the production rate of 12-HETE, which in turn mediates the down-regulation of GLUT-1 expression and the glucose-transport system in vascular endothelial and smooth-muscle cells.

Liquid chromatographic-electrospray ionization-mass spectrometric analysis of cytochrome P450 metabolites of arachidonic acid

Arachidonic acid (AA) can be metabolized by cytochrome P450 (CYP) enzymes to many biologically active compounds including 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs), their corresponding dihydroxyeicosatrienoic acids (DHETs), and 20-hydroxyeicosatetraenoic acid (20-HETE). These eicosanoids are potent regulators of vascular tone. We developed a liquid chromatography-electrospray ionization-mass spectrometry method to simultaneously determine 5,6-, 8,9-, 11,12-, and 14,15-EETs; 5,6-, 8,9-, 11,12-, and 14,15-DHETs; and 20-HETE. [2H8]EETs, [2H8]DHETs, and [2H2]20-HETE were used as internal standards. These compounds are readily separated on a C18 reverse-phase column using water:acetonitrile with 0.005% acetic acid as a mobile phase. The internal standards, [2H8]EETs, [2H8]DHETs, and [2H2]20-HETE, eluted slightly faster than the natural eicosanoids. The samples were ionized by electrospray with fragmentor voltage of 120 V and detected in a negative mode. The negative ion detection gave a lower background than the positive ion detection for these compounds. These eicosanoids exhibited high abundance of the ions corresponding to [M - 1]-. The m/z = 319, 337, and 319 ions were used for quantitation of EETs, DHETs, and 20-HETE, respectively. The detection limits using selected ion monitoring of these compounds are about 1 pg per injection. The position of functional groups and water content of mobile phase had a significant effect on the sensitivity of detection. Water content of 40% was found to give maximal sensitivity. The method was used to determine EETs, DHETs, and 20-HETE in bovine coronary artery endothelial cells, dog plasma, rat astrocytes, and rat kidney microsome samples.

Determination of EETs using microbore liquid chromatography with fluorescence detection

Epoxyeicosatrienoic acids (EETs) are cytochrome P-450 metabolites of arachidonic acid involved in the regulation of vascular tone. The method of microbore column high-performance liquid chromatography with fluorescence detection was developed to determine 14,15-EET, 11, 12-EET, and the mixture of 8,9-EET and 5,6-EET. Tridecanoic acid (TA) was used as an internal standard. EETs were reacted with 2-(2, 3-naphthalimino)ethyl trifluoromethanesulfonate (NT) to form highly fluorescent derivatives. A C(18) microbore column and a water-acetonitrile mobile phase were used for separation. Samples were excited at 259 nm, and the fluorescence was detected at 395 nm. The overall recoveries were 88% for EETs and 40% for TA. EETs were detected in concentrations as low as 2 pg (signal-to-noise ratio = 3). The method was used to determine the EET production from endothelial cells (ECs). Bradykinin and methacholine (10(-6) M) stimulated an increase in the production of EETs by ECs two- and fivefold, respectively. This sensitive method may be used for determination of EETs at low concentrations normally detected in complex biological samples.

25-hydroxycholesterol increases eicosanoids and alters morphology in cultured pulmonary artery smooth muscle and endothelial cells

25-hydroxycholesterol (25-OHC) is an oxidized derivative of cholesterol that has been implicated in the early development of arteriosclerosis. Changes in arterial smooth muscle cell (SMC) migration and proliferation have also been linked to the pathophysiology of arteriosclerosis. SMCs undergo "activation" in response to vascular injury by changing phenotypically and by increasing prostaglandin G/H synthase-2 (PGHS-2) protein levels and eicosanoid release. Activation is thought to be important in atheroma formation and arteriosclerosis progression. 25-OHC induces SMCs to change morphologically, increase PGHS-2, and increase eicosanoid release. Confluent monolayers were treated with 25-OHC (10 microg/mL) or the PGHS-2 inducer interleukin-1beta (1 ng/mL) for 18 hours at 37 degrees C. The 18-hour treatment resulted in morphological changes. After uptake of [(14)C]arachidonic acid, released radiolabeled arachidonic acid products were extracted and chromatographed by both normal and reverse-phase high-performance liquid chromatography systems. 25-OHC-treated cells increased their prostaglandin production, with the major component comigrating with a prostaglandin-E(2) standard. HETEs and epoxyeicosatrienoic acids were not affected. Immunoprecipitation analysis of treated and control cell lysates using anti-PGHS-1 and -2 and anti-alpha-actin primary antibodies indicated PGHS-2 induction over control and no change in contractile proteins. These changes are consistent with SMC activation, which occurs in vascular injury models. The notion that oxysterols can activate vascular SMCs may be important in ultimately understanding the pathophysiology of atheroma formation.

11,12-Epoxyeicosatrienoic acid stimulates endogenous mono-ADP-ribosylation in bovine coronary arterial smooth muscle

The role of endogenous ADP-ribosylation in mediating the activation of the Ca(2+)-activated K(+) channels was determined in bovine coronary arteries. Endogenous ADP-ribosylation was examined by incubating coronary arterial homogenates or lysates of cultured coronary arterial smooth muscle cells with [adenylate-(32)P]NAD. Four (32)P-labeled proteins were observed at 51, 52, 80, and 124 kDa in the homogenates and lysates. This reaction was enhanced by the addition of 11,12-epoxyeicosatrienoic acid (11,12-EET), a cytochrome P450-derived eicosanoid, and GTP to the incubation. By Western blot analysis, 42- and 70-kDa proteins were recognized by specific antibodies against ADP-ribosyltransferase in the coronary arterial homogenates and smooth muscle cell lysate but not in the lysate of endothelial cells. The 52-kDa acceptor protein of endogenous ADP-ribosylation comigrated with a protein ADP-ribosylated by cholera toxin and was recognized and immunoprecipitated by an anti-G(S)alpha antibody. These results suggest that G(S)alpha is one of several acceptors of the ADP-ribose moiety. As shown by the patch-clamp technique, 11,12-EET stimulated the activation of the K(+) channels in the smooth muscle cells, and this activation was completely blocked by novobiocin, vitamin K(1), 3-aminobenzamide, and m-iodobenzylguanidine, inhibitors of endogenous mono-ADP-ribosyltransferases. We conclude that endogenous mono-ADP-ribosyltransferases are present in smooth muscle from bovine coronary arteries. These enzymes transfer ADP-ribose to the cellular proteins such as G(S)alpha and may mediate intracellular signal transduction in coronary vascular smooth muscle. In the coronary circulation, the ADP-ribosylation signaling pathway may play an important role in mediating the activation of the K(+) channels induced by 11,12-EET.

Endothelium-derived hyperpolarizing factor--a critical appraisal

Endothelium-derived hyperpolarizing factor is defined as that substance which produces vascular smooth muscle hyperpolarization which cannot be explained by nitric oxide or by a cyclo-oxygenase product such as prostacyclin. The possibility that the factor is an epoxyeicosatrienoic acid or a cannabinoid agonist such as anandamide continues to be investigated, but definitive evidence in favour of either is lacking. The sensitivity of EDHF-mediated responses to charybdotoxin, to apamin or to mixtures of these two toxins may indicate the opening of more than one smooth muscle K-channel, but the possibility that these are located on the vascular endothelium is discussed.

Endothelium-dependent relaxation and hyperpolarization in guinea-pig coronary artery: role of epoxyeicosatrienoic acid

1. Acetylcholine (ACh) elicits an endothelium-dependent relaxation and hyperpolarization in the absence of nitric oxide (NO) and prostaglandin synthesis in the guinea-pig coronary artery (GPCA). This response has been attributed to a factor termed endothelial-derived hyperpolarizing factor (EDHF). Recently it has been suggested that EDHF may be a cytochrome P450 product of arachidonic acid (AA) i.e., an epoxyeicosatrienoic acid (EET). The present study investigated whether this pathway could account for the response to ACh observed in the GPCA in the presence of 100 microM N(omega)-nitro-L-arginine and 10 microM indomethacin. 2. ACh, AA and 11,12-EET each produced concentration-dependent relaxations in arteries contracted with the H1-receptor agonist AEP (2,2-aminoethylpyridine). The AA-induced relaxation was significantly enhanced in the presence of the cyclo-oxygenase/lipoxygenase inhibitor, eicosatetranynoic acid (30 microM). 3. The cytochrome P450 inhibitors proadifen (10 microM) and clotrimazole (10 microM) inhibited ACh, lemakalim (LEM) and AA-induced relaxation, whereas 17-octadecynoic acid (100 microM) and 7-ethoxyresorufin (10 microM) were without effect on all three vasodilators. Proadifen and clotrimazole also inhibited ACh (1 microM) and LEM (1 microM)-induced hyperpolarization. 4. The ability of various potassium channel blockers to inhibit relaxation responses elicited with ACh, AA and 11,12-EET was also determined. Iberiotoxin (IBTX; 100 nM) was without effect on responses to ACh but significantly reduced responses to both AA and 11,12-EET. In contrast, 4-aminopyridine (4-AP; 5 mM) significantly reduced response to ACh but not responses to AA and 11,12-EET. Combined IBTX plus (4-AP) inhibited the ACh-induced relaxation to a greater extent than 4-AP alone. Apamin (1 microM), glibenclamide (10 microM) and BaCl2 (50 microM) had no significant effect on responses to ACh, AA and 11,12-EET. 5. IBTX (100 nM) significantly reduced both 11,12-EET (33 microM) and AA (30 microM) hyperpolarization without affecting the ACh (1 microM)-induced hyperpolarization. In contrast, 4-AP significantly reduced the ACh-induced hyperpolarization without affecting either AA or 11,12-EET-induced hyperpolarizations. 6. In summary, our results suggest that the coronary endothelium releases a factor upon application of AA which hyperpolarizes the smooth muscle. The similarity of pharmacology between AA and 11,12-EET suggests that this factor is an EET. However, the disparity of pharmacology between responses to ACh versus responses to 11,12-EET do not support the hypothesis that EETs represent the predominant factor which ACh releases from the endothelium that leads to NO- and prostaglandin-independent hyperpolarization and relaxation in the GPCA.

Normal esophageal body function: a study using ambulatory esophageal manometry

OBJECTIVE

The objective of this study was to establish normative ambulatory manometric data for contractions and contraction propagation in three levels of the esophagus.

METHODS

Twenty-five healthy volunteers underwent simultaneous ambulatory 24 h manometry. Concomitant 24 h pH studies were performed to exclude the presence of increased esophageal acid exposure. Pressures were recorded over a complete circadian cycle while patients continued with their normal lifestyles including eating and sleeping. Data were analyzed with a software program that was previously modified and validated and that enables quantitation of contractions in terms of efficacy.

RESULTS

The frequency of contractions was lowest during sleep, was increased when awake, and was highest during meals. Contraction amplitude increased during meals, providing a greater propulsive force for bolus transport. Similarly, the prevalence of peristaltic waves varied according to different physiologic states, ie., while eating, upright, awake, and sleeping. An increased amplitude and prevalence of peristalsis resulted in an increase in manometric efficacy during meals.

CONCLUSIONS

This study provides normative data for ambulatory manometry for comparison when studying patients with disease.

Methacholine-induced contraction of rabbit pulmonary artery: role of platelet-endothelial transcellular thromboxane synthesis

Arachidonic acid- and methacholine-induced contractions of rabbit pulmonary arteries are mediated by thromboxane (TX) A2. Although removal of the endothelium abolishes the contractions, endothelial cells isolated from pulmonary arteries do not synthesize TXA2. Further studies described here showed that the expression of TX synthase was evident in platelets and intact pulmonary artery but not in endothelial cells. These studies examined the role of platelet TXA2 production in the vasoconstrictor response to methacholine. Endothelial cells were incubated with platelets in the presence or absence of methacholine. Methacholine caused an increase in TXB2 production. Pretreatment of endothelial cells with aspirin (100 micromol/L) before the addition of platelets did not impair the ability of methacholine to increase TXB2 synthesis. Conversely, if platelets were pretreated with aspirin, methacholine failed to stimulate TXB2. Using endothelial cells with their cellular lipids labeled with [3H]arachidonic acid, methacholine did not stimulate the production of [3H]TXB2. When the endothelial cells were incubated with methacholine and control platelets, [3H]TXB2 was detected. If aspirin-treated platelets were incubated with endothelial cells, methacholine did not increase the production of [3H]TXB2. However, pretreatment of the endothelial cells with aspirin did not affect the ability of methacholine to induce [3H]TXB2 release. This suggests that methacholine stimulated the endothelial cell to release arachidonic acid, which was transferred to the platelets and metabolized to TXA2. To test whether this cell-cell interaction is necessary for methacholine-induced contractions, rabbits were administered aspirin (20 mg/kg) for 2 days. On day 4, methacholine-induced contractions of pulmonary arteries were depressed in aspirin-treated compared with control subjects. Control arteries synthesized 6-keto-prostaglandin F1alpha and TXB2. Aspirin treatment inhibited both pulmonary artery and platelet TXB2 production but had no effect on vessel 6-keto-prostaglandin F1alpha. These studies implicate platelets as a vascular source of TXA2 and indicate that both endothelial cells and platelets may be required for methacholine-induced TXA2 synthesis and vasoconstriction.

20-HETE relaxes bovine coronary arteries through the release of prostacyclin

Neutrophils respond to ischemic injury by infiltrating the myocardium via the vascular wall. During this process, neutrophils are activated and release inflammatory mediators. Some of these mediators are metabolites of arachidonic acid. We have reported that neutrophils metabolize arachidonic acid to 20-HETE, a cytochrome P450 metabolite. We investigated the effects of 20-HETE on coronary vascular tone by examining 20-HETE-induced changes in isometric tension in bovine coronary artery rings precontracted with the thromboxane-mimetic, U46619. 20-HETE relaxed precontracted coronary rings in a concentration-dependent manner (EC50 of 3 x 10(-7) mol/L). Pretreatment with indomethacin, a cyclooxygenase inhibitor, shifted the concentration-response curve to the right (EC50 of 1 x 10(-6) mol/L); maximal relaxations were not affected. This suggested that 20-HETE-induced relaxations were, in part, dependent on the cyclooxygenase pathway. Relaxations to 20-HETE were not significantly changed in endothelium-denuded rings. To determine whether metabolism of 20-HETE to a vasoactive compound might explain the relaxations caused by 20-HETE, rings of coronary artery were incubated with [3H] 20-HETE. The incubation buffer was extracted and the [3H] products resolved on reverse-phase HPLC. Both denuded and intact arteries failed to metabolize [3H] 20-HETE. To investigate whether 20-HETE-induced relaxations were related to release of prostacyclin, we measured the release of 6-keto PGF1alpha, the stable metabolite of prostacyclin, from bovine coronary arteries. 20-HETE (1 x 10(-6) mol/L) stimulated an increase in 6-keto PGF1alpha in intact vessels (908 +/- 138 pg/mL versus 1402 +/- 157 pg/mL, basal versus stimulated). Thus, 20-HETE-induced relaxations are due, in part, to the stimulation of the release of the dilatory prostanoid, prostacyclin.

N-arachidonylethanolamide relaxation of bovine coronary artery is not mediated by CB1 cannabinoid receptor

It has been reported that the endogenous cannabinoid N-arachidonylethanolamide (AEA), commonly referred to as anandamide, has the characteristics of an endothelium-derived hyperpolarizing factor in rat mesenteric artery. We have carried out studies to determine whether AEA affects coronary vascular tone. The vasorelaxant effects of AEA were determined in isolated bovine coronary artery rings precontracted with U-46619 (3 x 10(-9) M). AEA decreased isometric tension, producing a maximal relaxation of 51 +/- 9% at a concentration of 10(-5) M. Endothelium-denuded coronary arteries were not significantly affected by AEA. The CB1 receptor antagonist SR-141716A (10(-6)M) failed to reduce the vasodilatory effects of AEA, suggesting that the CB1 receptor is not involved in this action of AEA. Because AEA is rapidly converted to arachidonic acid and ethanolamine in brain and liver by a fatty acid amide hydrolase (FAAH), we hypothesized that the vasodilatory effect of AEA results from its hydrolysis to arachidonic acid followed by enzymatic conversion to vasodilatory eicosanoids. In support of this hypothesis, bovine coronary arteries incubated with [3H]AEA for 30 min hydrolyzed 15% of added substrate; approximately 9% of the radiolabeled product was free arachidonic acid, and 6% comigrated with the prostaglandins (PGs) and epoxyeicosatrienoic acids (EETs). A similar result was obtained in cultured bovine coronary endothelial cells. Inhibition of the FAAH with diazomethylarachidonyl ketone blocked both the metabolism of [3H]AEA and the relaxations to AEA. Whole vessel and cultured endothelial cells prelabeled with [3H]arachidonic acid synthesized [3H]PGs and [3H]EETs, but not [3H]AEA, in response to A-23187. Furthermore, SR-141716A attenuated A-23187-stimulated release of [3H]arachidonic acid, suggesting that it may have actions other than inhibition of CB1 receptor. These experiments suggest that AEA produces endothelium-dependent vasorelaxation as a result of its catabolism to arachidonic acid followed by conversion to vasodilatory eicosanoids such as prostacyclin or the EETs.

Double-blind placebo-controlled study of cisapride in patients with nonspecific esophageal motility disorder accompanied by delayed esophageal transit

BACKGROUND

Nonspecific esophageal motility disorder (NEMD) represents a difficult therapeutic challenge because of the heterogeneous nature of the esophageal motor functions. We studied the effects of cisapride on the esophageal symptoms and esophageal motor function in a group of patients with NEMD showing delayed esophageal transit.

METHODS

Seventy eligible patients were entered into a 4-week, double-blind randomized comparison of 10 mg of cisapride or placebo, four times daily. Symptom assessment, esophageal manometry after wet swallows, and esophageal scintigraphy after intake of a liquid and solid bolus were performed in each patient before and after treatment.

RESULTS

After 4 weeks of treatment cisapride significantly increased the prevalence of esophageal peristaltic contractions (percentage of total contractions, P < 0.05 versus base line and placebo) and significantly improved esophageal emptying of the solid bolus (P < 0.05 versus placebo) but not of the liquid bolus. Placebo did not have any significant effects versus base line on these variables. Both placebo and cisapride improved the distal esophageal amplitude versus base line (no significant intergroup differences). Symptom scores were significantly reduced after 4 weeks of treatment versus base line in both groups (no significant intergroup differences except for heartburn and regurgitation, P < 0.05). On global evaluation of treatment, significantly more patients in the cisapride group were rated as markedly or moderately improved, when compared with placebo.

CONCLUSIONS

The results of the present study showed that cisapride is effective and well tolerated in patients with NEMD accompanied by delayed esophageal transit. Symptomatic improvement may possibly be related to its beneficial action on the esophageal body by increasing the number of peristaltic contractions and esophageal emptying of solids.

Determination of 14,15-epoxyeicosatrienoic acid and 14,15-dihydroxyeicosatrienoic acid by fluoroimmunoassay

A fluoroimmunoassay (FIA) for 14,15-epoxyeicosatrienoic acid (14,15-EET) and 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), cytochrome P450 epoxygenase products of arachidonic acid, was developed using fluorescence polarization. 14-15-EET was hydrolyzed and analyzed as 14,15-DHET. 14,15-DHET was conjugated to thyroglobulin and a specific antibody was raised in rabbits. Both [3H8]14,15-DHET in radioimmunoassay or fluorescein-labeled 14,15-DHET (14, 15-DHET*) in FIA bound to this antibody and were competitively displaced by 14,15-DHET. The binding activity and cross-reactivity of 14,15-DHET antibody were also studied by RIA compared to FIA. The antibody cross-reacted < or = 1% with 11,12-DHET and 14,15-EET and < 0.1% with other regioisomeric DHETs and arachidonic acid metabolites. The detection limit of 14,15-DHET was 2 pg/0.6 ml by FIA. Using this method, we found that A23187 stimulated the production of 14,15-EET by endothelial cells by angiotensin II stimulated 14,15-EET release from zona glomerulosa cells. The production of 14,15-EET in these samples was confirmed by gas chromatography/mass spectrometry. These studies demonstrate a sensitive and specific FIA for 14,15-EET and 14,15-DHET and that agonists stimulate the release of these eicosanoids in two cell types, bovine coronary artery endothelial cells and bovine zona glomerulosa cells.

Effects of polyunsaturated fatty acids and some of their metabolites on mitotic activity of vascular smooth muscle explants from the coronary artery of rainbow trout (Oncorhynchus mykiss)

This study is the first to examine the effects of polyunsaturated fatty acids and some of their metabolites on [3H]thymidine incorporation into vascular smooth muscle explants from the coronary artery of rainbow trout (Oncorhynchus mykiss). At a concentration of 120 μM, eicosapentaenoic acid (EPA; 20:5ω3), arachidonic acid (AA; 20:4ω6), and eicosatrienoic acid (ETA; 20:3ω6) all approximately doubled [3H]thymidine incorporation relative to controls. At a concentration of 20 μM, EPA had no significant effect, while ETA inhibited and AA caused an almost 5-fold increase in [3H]thymidine incorporation. The large mitogenic effect of 20 μM AA was completely inhibited by simultaneous addition of EPA to the culture medium. ETA only partially inhibited the mitogenic effect of 20 μM AA. Four AA-derived eicosanoids (or their stable analogues) were also tested. [3H]Thymidine incorporation was at least doubled with 1000 ng/mL carbacyclin (a prostacyclin analogue), 120 ng/mL prostaglandin F2α, and U-46619 (a thromboxane A2 analogue), but did not reach the level of stimulation produced by 20 μM AA. Leukotriene C4 had no significant effect. We conclude that dietary modulation of polyunsaturated fatty acids (PUFAs) in salmonids could have significant effects on coronary vascular smooth muscle mitosis through the incorporation of PUFAs into cell membranes and the production of eicosanoids.

Mediators of arachidonic acid-induced relaxation of bovine coronary artery

Bovine coronary arteries relax in response to bradykinin, methacholine, sodium nitroprusside, isoproterenol, and arachidonic acid in a concentration-dependent manner. The relaxations to methacholine, bradykinin, and arachidonic acid are lost when endothelium is removed. Indomethacin, a cyclooxygenase inhibitor, attenuated the relaxations to methacholine, bradykinin, and arachidonic acid and shifted the EC50 (control versus indomethacin) to each (1 x 10(-7) versus 3 x 10(-7) mo1/L, 3 x 10(-10) versus 2 x 10(-9) mo1/L, and 3 x 10(-7) versus 2 x 10(-6) mo1/L, respectively). Nitro-L-arginine, a nitric oxide synthase inhibitor, also attenuated the relaxations to methacholine, bradykinin, and arachidonic acid and shifted the EC50 (control versus nitro-L-arginine) to each (1 x 10(-7) versus 3 x 10(-7) mo1/L, 3 x 10(-10) versus > 10(-9) mo1/L, and 3 x 10(-7) versus > 10(-6) mo1/L, respectively). The combination of indomethacin and nitro-L-arginine blunted the relaxations to these agents and also shifted the EC50 values (control versus indomethacin plus nitro-L-arginine) to each (1 x 10(-7) versus 5 x 10(-7) mo1/L, 3 x 10(-10) versus > 10(-9) mo1/L, and 3 x 10(-7) versus > 10(-6) mo1/L, respectively). Methacholine, bradykinin, and arachidonic acid stimulated the release of prostaglandin I2, measured as 6-keto-PGF1 alpha. Indomethacin, but not nitro-L-arginine, inhibited arachidonic acid-induced release of 6-keto-PGF1 alpha. Vascular cGMP content was unchanged by arachidonic acid but was significantly elevated by bradykinin. Relaxations to prostaglandin I2 and sodium nitroprusside, but not 8,9-epoxyeicosatrienoic acid or isoproterenol, were inhibited by nitro-L-arginine. We conclude that the endothelium-dependent relaxations to methacholine, bradykinin, and arachidonic acid are partly due to prostaglandin I2 release. The remainder of the responses to these agents is due to the release of other relaxing factor or factors. Since bradykinin increased cGMP and nitro-L-arginine partially inhibited its relaxant effects, nitric oxide also appears to participate in the bradykinin-induced effect. Since the combination of indomethacin and nitro-L-arginine failed to completely block the relaxations to methacholine, bradykinin, and arachidonic acid, another endothelial factor must contribute to their vascular effects. Surprisingly, nitro-L-arginine attenuated the relaxations to arachidonic acid; however, L-arginine failed to reverse the effects of nitro-L-arginine on arachidonic acid-induced relaxations. In addition, arachidonic acid failed to increase cGMP. Nitro-L-arginine also reduced the responses to prostaglandin I2 and sodium nitroprusside. These data indicate that these arginine analogues may have effects other than competitive inhibition of nitric oxide synthase.

Metabolism of arachidonic acid by canine polymorphonuclear leukocytes synthesis of lipoxygenase and omega-oxidized metabolites

Both polymorphonuclear (PMN) leukocytes and metabolites of arachidonic acid, especially lipoxygenase products, have been reported to contribute to myocardial damage after coronary artery occlusion and reperfusion. While canine models of myocardial ischemia were used in many of these studies, very little is known about arachidonic acid metabolism by canine PMNs. Moreover, it is unclear whether arachidonic acid metabolites released by canine PMNs affect vascular tone. Therefore, we characterized arachidonic acid metabolism by canine PMNs and determined the effect of these metabolites on vascular tone of isolated canine coronary arteries. Suspensions of canine PMNs were incubated with [14C]arachidonic acid and the calcium ionophore A23187. The incubation media was extracted, and the metabolites resolved by HPLC. 20-Hydroxy-leukotriene B4 (LTB4), 12,20-dihydroxyeicosatetraenoic acid (diHETE), LTB4, 12-hydroxyheptadeclatrienoic acid (HHT), and 12-(S)-hydroxyeicosatetraenoic acid (HETE) were isolated, and their structures confirmed by gas chromatography/mass spectrometry. There was also evidence for the formation of 20-HETE, thromboxane B2 (TXB2), 5-HETE, and several isomers of LTB4. None of the arachidonic acid metabolites that were isolated from incubates of canine PMNs augmented vascular tone, but material migrating with 12,20-diHETE relaxed canine coronary arteries. Authentic 12(S),20-diHETE also produced a concentration-related relaxation of canine coronary artery. 12(R), 20-diHETE was inactive. 20-HETE inhibited A23187-induced PMN aggregation. Thus, arachidonic acid is metabolized in canine PMNs through the cyclooxygenase, lipoxygenases and cytochrome P-450 pathways. Whether these metabolites contribute to myocardial injury remains to be determined.

Nitro-L-arginine inteferes with the cadmium reduction of nitrate/griess reaction method of measuring nitric oxide production

Nitro-L-arginine is used as an inhibitor of nitric oxide synthase in many biological Systems. Nitric oxide (NO) is unstable and degrades to nitrite NO(2)- and nitrate NO(3)-. The colorimetric reaction of N0(2)- with Griess reagent is commonly used to measure NO(2)-. NO(3)- may be measured as NO(2)- following reduction by cadmium or cadmium/copper. We found that bradykinin increased the formation of NO(2)- by bovine coronary endothelial cells. Nitro-L-arginine further increased the formation of NO(2)-. This increase is due to the interference of nitro-L-arginine in determination of NO(3)- by the cadmium reduction to NO(2)- and Griess reagent reaction. Incubation of nitro-L-arginine with cadmium or cadmium/copper produced a product that reacts with Griess reagent to form a compound that has an absorption spectrum identical to the product formed by NO(2)- and Griess reagent. Caution must be exercised when using the NO(2)-/NO(3)- measurement by the Griess reaction to assess inhibition of nitric oxide synthase by nitro-L-arginine.

Synthesis of hydroxyeicosatetraenoic (HETEs) and epoxyeicosatrienoic acids (EETs) by cultured bovine coronary artery endothelial cells

Endothelial cells release several factors which influence vascular tone, leukocyte function and platelet aggregation. Some of these factors are metabolites of arachidonic acid, most notably prostacyclin. However, many of the endothelial metabolites of arachidonic acid have not been positively identified. The purpose of these studies is to identify the arachidonic acid metabolites synthesized by bovine coronary endothelial cells. Cultured bovine coronary artery endothelial cells were incubated with [14C]arachidonic acid. The incubation media was extracted and the radioactive metabolites resolved by a combination of reverse phase- and normal phase-high pressure liquid chromatography (HPLC). The cells synthesized 6-keto prostaglandin (PG)F1 alpha, PGE2, 12-hydroxyheptadecatrienoic acid (HHT), 12-, 15-, and 11-hydroxyeicosatetraenoic acids (HETE), and 14,15-, 11,12-, 8,9-, and 5,6-epoxyeicosatrienoic acids (EET). Several of the HETEs were further analyzed by chiral-phase HPLC. The cells synthesized predominately 12(S)-, 15(S)-, and 11(R)-HETE. The synthesis of the S optical isomers of 12- and 15-HETE suggested that the 12- and 15-lipoxygenases were present in these cells. 11(R)-HETE is probably derived from cyclooxygenase. They also synthesized smaller amounts of 9-, 8- and 5-HETEs. The structures of the HETEs and EETs were confirmed by mass spectrometry. The release of 6-keto PGF1 alpha and 15-HETE was measured by specific radioimmunoassays. Melittin, thrombin, arachidonic acid and A23187 stimulated the release of both eicosanoids in a concentration-related matter. Under all conditions, the release of 6-keto PGF1 alpha exceed the release of 15-HETE. Therefore, cultured bovine coronary artery endothelial cells synthesize cyclooxygenase, lipoxygenase and cytochrome P-450 metabolites of arachidonic acid.

Proliferation-dependent changes in release of arachidonic acid from endothelial cells

Stimulation of endothelial cells resulted in release of arachidonic acid from phospholipids. The magnitude of this response decreased as the cells became confluent and the change coincided with a decrease in the percentage of cells in growth phases (G2+M); this was not a consequence of time in culture or a factor in the growth medium. Preconfluent cells released approximately 30% of arachidonic acid; confluent cells released only 6%. The decreasing release of arachidonic acid was demonstrated using metabolic labeling, mass measurements of arachidonic acid, and measurement of PGI2. The decrease was not due to a changing pool of arachidonic acid, and mass measurements showed no depletion of arachidonic acid. Release from each phospholipid and from each phospholipid class decreased with confluence. Conversion of confluent cells to the proliferative phenotype by mechanical wounding of the monolayer caused increased release of arachidonic acid. Potential mechanisms for these changes were investigated using assays of phospholipase activity. Phospholipase A2 activity changed in concert with the alteration in release, a consequence of changes in phosphorylation of the enzyme. The increased release of arachidonic acid from preconfluent, actively dividing cells may have important physiologic implications and may help elucidate mechanisms regulating release of arachidonic acid.

Effect of viscosity on oropharyngeal and esophageal emptying in man

The effect of bolus viscosity on oropharyngeal and esophageal emptying is not known. We investigated this question in 38 healthy volunteers by measuring the transit of five semisolid boluses of varying viscosities across the oropharynx and the esophagus with the aid of scintigraphy. The studies were performed twice on consecutive days. The results show that oropharyngeal and esophageal emptying are reliably reproduced from day to day. Esophageal emptying was inversely related to bolus viscosity; however, oropharyngeal emptying was not influenced by bolus viscosity. We conclude that bolus viscosity has significant, but selective, effect on oropharyngoesophageal emptying.

Involvement of protein kinase C in the control of microvascular permeability to colloidal carbon

The vasculature of the rat small intestine and attached mesentery was perfused in vitro with a gelatin-containing physiological salt solution (GPSS). The inclusion of colloidal carbon (CC) in the perfusate towards the end of the experimental period enabled the "leakiness" of microvessels in the villi to be determined, since "leaky" vessels trap CC in their walls. Addition to the perfusate of the inflammatory agonists platelet-activating factor (PAF, 5 x 10(-6) M) or 5-hydroxytryptamine (5-HT, 1 x 10(-4) M), or the microtubule-disrupting agents podophyllotoxin (5 x 10(-5) M), or colcemid (5 x 10(-5) M), or the protein kinase C (PKC) activator phorbol 12, 13-dibutyrate (PDB, 1 x 10(-6) M), caused significantly increased microvascular "blackening" as assessed by image analysis. 4 alpha-phorbol 12, 13-didecanoate (PDD, 1 x 10(-6) M) had no effect. Pretreatment with the PKC inhibitor Ro 31-8220 [corrected] (1 x 10(-6) M) significantly reduced the effects of PAF, 5-HT and PDB, but not those of podophyllotoxin or colcemid. These results suggest, therefore, that PKC is involved in the permeability-enhancing effects of PAF, 5-HT and PDB. Pretreatment with indomethacin (1 x 10(-6) M) as a cyclooxygenase inhibitor did not reduce the response to PDB, indicating that prostaglandin release is of minor importance in the PDB-induced increase in microvascular permeability.

Effect of elevated glucose on cyclic GMP and eicosanoids produced by porcine aortic endothelium

The short-term effects of elevated glucose on cyclic GMP (cGMP) and eicosanoid production in pig aortic endothelial cell monolayers was determined by incubating cells in 5.5 mM or 44 mM glucose for 6 hours. Bradykinin- or A23187-stimulated cGMP production was significantly reduced in cells incubated in 44 mM glucose compared with 5.5 mM glucose. Stimulation of cGMP levels with exogenously added nitric oxide (NO) was also decreased to a similar extent in cells exposed to 44 mM glucose. These data suggest that NO production stimulated by bradykinin or A23187 was unchanged by elevated glucose. Assayed eicosanoids, including 6-ketoprostaglandin (PG) F1 alpha, PGE2 alpha, and 15(S)-hydroxy-(5Z, 8Z, 11Z, 13E)-eicosatetraenoic acid, stimulated by bradykinin or A23187, were increased in cells exposed to 44 mM glucose. These eicosanoid products formed from exogenously added arachidonic acid did not differ between cells incubated in 5.5 mM or 44 mM glucose. Hyperosmolar concentrations of mannose or sucrose had no effect on cGMP levels but did mimic the effect of elevated glucose on eicosanoid production. These data suggest that hyperglycemia in diabetes may interfere with NO-induced guanylate cyclase activation but not NO production in the endothelium and that increased phospholipase activity, secondary to hyperosmolarity, may account for elevated eicosanoid levels.

Endothelium-dependent contractions in rabbit pulmonary artery are mediated by thromboxane A2

This study was designed to characterize the endothelium-dependent contracting factor (EDCF) released by arachidonic acid (AA) and methacholine (MeCH) in the rabbit pulmonary artery. AA and MeCH contract the rabbit pulmonary artery; however, the effects of both are blocked by denuding the vessels and by administration of indomethacin (a cyclooxygenase inhibitor), dazoxiben (a thromboxane [TX] synthase inhibitor), and SQ29548 (a TXA2/prostaglandin [PG] H2 receptor antagonist). When segments of rabbit pulmonary artery were incubated with [14C]AA and the [14C] metabolites were resolved by reverse-phase high-performance liquid chromatography (HPLC), radioactive products were observed that comigrated with 6-keto-PGF1 alpha and TXB2, the stable metabolites of prostacyclin and TXA2. The TXB2 radioactive peak was rechromatographed on normal-phase HPLC and again migrated with TXB2. Finally, the structures of derivatized [14C]6-keto-PGF1 alpha and [14C]TXB2 peaks were confirmed by gas chromatography/mass spectrometry. The synthesis of [14C]6-keto-PGF1 alpha and [14C]TXB2 was inhibited by removal of the endothelium and by indomethacin. Dazoxiben inhibited the synthesis of [14C]TXB2 but not [14C]6-keto-PGF1 alpha. Using specific radioimmunoassays, AA and MeCH stimulated 6-keto-PGF1 alpha and TXB2 release. Indomethacin blocked the production of both 6-keto-PGF1 alpha and TXB2, whereas dazoxiben only blocked TXB2. In a superfusion/bioassay system, AA stimulated an endothelium-intact donor vessel to release a labile substance that contracted an indomethacin-treated endothelium-denuded recipient vessel. The EDCF released by AA had an approximate half-life of 30 seconds. Cultured rabbit pulmonary arterial endothelial cells synthesized 6-keto-PGF1 alpha but not TXB2. Immunohistochemical studies indicated the presence of cyclooxygenase, but not TX synthase, in pulmonary artery endothelial cells. TXA2 appears to be the EDCF released by AA and MeCH in rabbit pulmonary artery; however, TXA2 is not produced by endothelial cells but may arise from cells that adhere to the luminal surfaces, such as platelets or macrophages.

Solid swallowing versus water swallowing: manometric study of dysphagia

The aim of the study was to investigate whether a soft solid bolus can induce abnormal manometric patterns in patients with dysphagia and normal standard manometry. The study group comprised 12 normal volunteers and 22 patients with dysphagia. Manometry was performed using 10 wet swallows followed by 10 swallows of marshmallow. The results show: (1) in normal subjects the mean contraction amplitude is significantly greater (P less than 0.035) and the velocity of propagation significantly slower (P less than 0.003) for soft solid swallows compared with wet swallows; (2) in normal subjects there are fewer abnormal contractions after soft solid swallows than after wet swallows; (3) in 15 patients, soft solid swallows induced non-peristaltic contractions and/or contractions of extreme amplitude and/or duration that were not observed after wet swallows; (4) in patients, the probability of inducing abnormal contractions after soft solid swallows is significantly greater than after wet swallows (P less than 0.0001). We conclude that soft solid swallowing is useful in the study of patients with dysphagia.