5-Lipoxygenase inhibitors in the treatment of inflammatory bowel disease.
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Amino Acid Sequence↗
Biomedical subjects
K Bukhave
Publications and source records attributed to K Bukhave.
Bicarbonate transport by rabbit duodenum in vitro: effect of vasoactive intestinal polypeptide, prostaglandin E2, and cyclic adenosine monophosphate.
BACKGROUND: Duodenal surface cells secrete bicarbonate that provides a barrier against injury. The current experiments were performed to identify duodenal bicarbonate regulatory and transport pathways. METHODS: Rabbit proximal duodenal mucosa were mounted in chambers under short-circuited conditions. Bicarbonate transport, short-circuit current (Isc), and potential difference (PD) were quantitated in response to prostaglandin E2 (PGE2), vasoactive intestinal polypeptide (VIP), and dibutyryl cyclic adenosine monophosphate (db-cAMP). Anoxia (N2), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and Cl(-)-free solutions, ouabain, and Na-free solutions were also studied, as was the effect of VIP and PGE2 on duodenocyte cAMP. RESULTS: PGE2, VIP, db-cAMP, and theophylline significantly increased bicarbonate secretion, Isc, and PD. Ouabain, Na(+)-free bathing solutions, and anoxia (N2) inhibited the responses. DIDS and Cl(-)-free solutions abolished the PGE2-induced response, reduced the response to VIP by about 50%, and had no effect on the response to db-cAMP. After PGE2 and VIP, cAMP concentration increased, yet was likely independent of bicarbonate secretion. CONCLUSIONS: Mammalian duodenal HCO3- transport requires Na+, Na+/K(+)-adenosine triphosphatase and O2-dependent metabolic pathways and is stimulated by PGE2, VIP, and cAMP, acting by distinct pathways.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
Percentage distribution of fatty acids in subcutaneous adipose tissue of patients with peptic ulcer disease.
Dietary linoleic acid has been implicated in the pathogenesis of peptic ulcer disease because its metabolite arachidonic acid may be converted to cytoprotective prostaglandins. In addition, it has been suggested that the falling incidence and virulence of duodenal ulcer disease is related to increased dietary polyunsaturated essential fatty acid intake. In the present study the percentage content of linoleic acid in subcutaneous adipose tissue microbiopsies were used to see whether changes in percentage of fatty acids correlate with the presence or absence of an ulcer in individual patients. No significant difference in the adipose tissue content of linoleic acid was found, ie, 11.2 +/- 0.7% (n = 15) vs 10.9 +/- 0.5% (n = 15) in patients with peptic ulcer disease and matched control subjects, respectively.
Adipose Tissue↗
Acute effects of smoking during modified sham feeding in duodenal ulcer patients. An analysis of nicotine, acid secretion, gastrin, catecholamines, epidermal growth factor, prostaglandin E2, and bile acids.
Smoking is associated with an increased incidence of duodenal ulcer with a high relapse rate, and smokers tend to be slow healers. The etiology responsible for this remains unknown, and there is general disagreement as to whether smoking affects gastric secretion. The aim of the present study was to investigate both aggressive and protective factors in response to vagal stimulation induced by modified sham feeding (MSF) in duodenal ulcer patients when smoking versus not smoking. On smoking days, nicotine concentrations in plasma averaged about 15 ng/ml and were extremely high in saliva and gastric juice (> 1300 and > 800 ng/ml, respectively). MSF induced a significant decrease in intragastric pH during non-smoking (p = 0.01) but not during smoking. Acid output 1 h after MSF was lower on smoking than on non-smoking days (p = 0.02), as was volume secretion (p = 0.02). Plasma gastrin concentrations were significantly increased during MSF on non-smoking days (p = 0.04) but not on smoking days, the concentrations during the whole day being lower on smoking days (p = 0.002). Plasma catecholamine levels were unaffected by MSF, whether smoking or not. However, plasma concentrations of noradrenaline decreased during the smoking of a single cigarette (p = 0.03), whereas those of adrenaline were increased on smoking days (p = 0.02). Epidermal growth factor concentrations were decreased in gastric juice after MSF during non-smoking (p = 0.01) but not during smoking. Although prostaglandin E2 (PGE2) concentrations in gastric juice were unaffected by MSF, PGE2 output increased after MSF whether smoking or not, the increment being non-significantly less during smoking (p = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)
Bile Acids and Salts↗
Effect of combined prednisolone, epidural analgesia, and indomethacin on the systemic response after colonic surgery.
Twenty patients undergoing colonic resection were randomized to either conventional postoperative pain treatment with morphine chloride and acetaminophen (group 1, n = 9) or methylprednisolone sodium succinate 90 minutes before surgery plus intraoperative neural blockade, with a postoperative analgesic regimen with combined bupivacaine hydrochloride-morphine and indomethacin sodium for systemic effect (group 2, n = 11). Assessments of pain, pulmonary function, convalescence, and various injury factors were done several times until 8 days after surgery. Postoperative pain and hyperthermic response were eliminated in group 2. Conventional reduction in pulmonary function measures was improved in group 2, and fatigue and mobility were less pronounced. Prostaglandin E2, interleukin 6, and C-reactive protein levels increased in both groups, but significantly less in group 2. These results suggest that a combined neural and humoral blockade may more effectively inhibit the global stress response to elective surgery than previously observed with neural blockade with or without indomethacin.
Acetaminophen↗
Indomethacin decreases jejunal fluid secretion in addition to luminal release of prostaglandin E2 in patients with acute cholera.
Human cholera is associated with an increased luminal release of prostaglandin E2 (PGE2), but whether inhibition of increased PGE2 synthesis will reduce or control intestinal secretion is uncertain. 'Steady state' perfusions (10 ml/minute) in 12 patients with acute cholera, and repeat perfusions in nine of these patients during the convalescent phase were therefore performed using the triple lumen technique. The proximal jejunum was perfused with isotonic saline containing sodium-sulphobromophthalein as a non-absorbable marker. After intravenous administration of indomethacin (1.0 mg/kg) the jejunal net transfer of fluid and the jejunal flow rate of PGE2 were determined in 30 minute periods for 120 minutes after a 120 minute control period. Indomethacin decreased net fluid secretion (2.1 (0.3-4.2) v 4.5 (2.5-8.4) ml/hour x cm; medians, Q50 ranges, p less than 0.01) and the jejunal flow rate of PGE2 (1.5 (1.2-2.7) v 2.2 (1.4-4.9) ng/minute, p less than 0.05). The results of similar perfusion studies in 22 patients with acute cholera, used to establish the spontaneous time related change in fluid secretion, showed no significant change in net fluid transfer (3.5 (2.2-6.2) to 3.5 (2.6-11.6) ml/hour x cm, p greater than 0.25) over 240 minutes. These data provide further evidence in favour of the hypothesis that prostaglandins have a role in the cholera toxin induced intestinal fluid secretion in man.
Adult↗
5-Lipoxygenase inhibitors for the treatment of inflammatory bowel disease.
The unique role of the enzyme 5-lipoxygenase (5-LO) in the production of leukotrienes (LTs) makes it a likely target for biochemical manipulation. The rationale for using 5-LO inhibitors for the treatment of inflammatory bowel disease (IBD) is based on the increased generation of LTs in the inflamed mucosa, LTB4 being the most potent chemotactic and chemokinetic metabolite of arachidonic acid. Furthermore, conventional drugs, such as corticosteroids, sulphasalazine, and 5-aminosalicylic acid, inhibit LT production and specific 5-LO inhibition accelerates healing in animal models of acute colitis. The compounds identified as 5-LO inhibitors can be divided into antioxidants, substrate-analogous, and a large miscellaneous group of inhibitors, where hydroxamic acids are potent and more selective inhibitors of 5-LO. The benzothiophene hydroxyurea, zileuton, is the first selective 5-LO inhibitor evaluated for the treatment of patients with IBD. An 800-mg oral dose of zileuton was shown to reduce LTB4, but not prostaglandin E2, concentrations by 75-85% in rectal dialysates from patients with active ulcerative colitis. The clinical efficacy of zileuton 800 mg b.i.d. has also been tested in a randomized, double-blind, placebo-controlled trial in similar patients. Zileuton significantly improved the symptom scores and the histology score, but not the sigmoidoscopy score, compared to pretreatment conditions and with response to placebo, the beneficial effects being most pronounced in patients not receiving concomitant sulphasalazine treatment. The mean inhibition of LTB4 in the target tissue of inflammation was 70%. The proof that any putative 5-LO inhibitor is blocking LT production is an important stage in assessing any such drug. The main disadvantage of existing new LT inhibitors relates to the high potency of LTs, and unless a higher level of inhibition can be achieved, endogenous LTs may still be present in sufficient amounts to produce their effects.
Adrenal Cortex Hormones↗
Prostaglandin E2 in intestinal secretion with special reference to methodological problems in vivo and in vitro.
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Adenoma↗
Colloidal bismuth subcitrate causes sustained release of gastric mucosal prostaglandin E2.
Gastric application of high doses of colloidal bismuth subcitrate (CBS) stimulates mucosal prostaglandin E2 (PGE2) production, which is considered part of the mechanism by which the drug accelerates peptic ulcer healing. Whether therapeutic, orally administered, doses of CBS cause a sustained stimulation of prostaglandin production is not known. We have, therefore, determined gastric luminal release of PGE2 during 'steady-state' perfusion of the stomach with CBS (10 mg/ml; isotonic mannitol 5 ml/min) and 4 h after the last oral dose of the drug (240 mg b.d.) for 2 weeks (isotonic mannitol 5 ml/min) in 8 healthy volunteers. A significant increase in PGE2 concentrations (712 (409-1076) vs. control 334 (252-655) pg/ml; medians with Q50 ranges; P less than 0.02) and PGE2 output (12.5 (7.3-14.3) vs. control 4.8 (4.1-7.3) ng/15 min; P less than 0.02) occurred during gastric perfusion with CBS. A similar increase in PGE2 concentrations (630 (297-1429) pg/ml; P less than 0.02) and PGE2 output (12.6 (6.4-22.2) ng/15 min; P less than 0.02) was observed following treatment with CBS for 2 weeks. These results suggest that therapeutic doses of CBS cause a sustained stimulation of gastric mucosal PGE2 formation.
Adult↗
Selective 5-lipoxygenase inhibition in ulcerative colitis.
Leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) concentrations were measured in rectal dialysis fluid from ten patients with active ulcerative colitis before and after oral administration of 800 mg of the 5-lipoxygenase inhibitor A-64077. The median LTB4 level fell significantly, from 4.9 (range 0.6-20.4) ng/ml before treatment to 1.6 (0.3-5.7) ng/ml after 4 h and 0.7 (0.1-8.0) ng/ml after 8 h; it had returned to pretreatment levels by 28 h. The concentration of PGE2 did not change significantly. The increased generation of 5-lipoxygenase products, such as LTB4, in ulcerative colitis and the potent proinflammatory actions of these products suggest that they have an important role in the amplification of the inflammatory response. A controlled trial to assess the clinical efficacy of A-64077 seems worth while.
Administration, Oral↗
Proximal duodenal prostaglandin E2 release and mucosal bicarbonate secretion are altered in patients with duodenal ulcer.
Proximal duodenal mucosal bicarbonate production is impaired in patients with duodenal ulcer disease. Because prostaglandins of the E class increase human proximal duodenal bicarbonate secretion, this study tested the hypothesis that endogenous prostaglandin E2 production is defective in patients with duodenal ulcer. Ten patients, five with active and five with inactive duodenal ulcer disease, were studied along with 10 normal volunteers. The proximal 4 cm of duodenum, the bulb, was isolated and continuously perfused with 154 mmol/L NaCl. Basal bicarbonate secretion was measured for 30 minutes. The test segment was then acidified with a physiological amount of HCl (2 mmol over 5 minutes), and acid-stimulated bicarbonate secretion was measured by pH/PCO2 and back-titration for 55 more minutes. Prostaglandin E2 was measured in the effluents by a radioimmunologic assay validated by gas chromatography-mass spectrometry. Compared with the normal subjects after luminal acidification, the duodenal ulcer patients had significantly greater PGE2 release and decreased total 1-hour bicarbonate output. The peak 5-minute acid-stimulated bicarbonate responses were not significantly different between the duodenal ulcer patients and normal subjects. After luminal acidification, PGE2 output remained elevated in the duodenal ulcer patients but returned promptly to basal in the normal subjects. Furthermore, the ratio of bicarbonate secreted to the amount of PGE2 released was significantly less in the ulcer patients. These findings suggest that patients with duodenal ulcer disease have an impaired mucosal bicarbonate response to endogenous PGE2. The increased acid-stimulated PGE2 response in duodenal ulcer patients suggests a compensatory phenomenon in response to the diminished mucosal bicarbonate production.
Bicarbonates↗
Influence on intestinal secretion of eicosanoids.
Eicosanoids have been shown to be important modulators of intestinal secretion. In cholera, cAMP is often regarded as the sole mediator, but recent data suggest that 5-hydroxytryptamine (5-HT) and prostaglandin (PG) E2 also play important roles. Thus cholera toxin (CT) increases their release from the rat jejunum in vivo, and human cholera is associated with an increased luminal 'overflow' of PGE2. In vitro evidence of secretion can be obtained with PG concentrations 100- to 1000-fold lower than those required for activation of the adenylate cyclase. Furthermore, 5-HT induces secretion associated with increased 'overflow' of PGE2, but without a change in mucosal cAMP. CT-induced release of PGE2 and fluid secretion can be decreased by indomethacin or by the 5-HT2-receptor antagonist, ketanserin, whereas the release of 5-HT and cAMP is not affected by either substance. Secretion caused by vasoactive intestinal polypeptide (VIP) is associated with increased mucosal cAMP levels, without a change in PGE2 release, and is unaffected by indomethacin and ketanserin. These results suggest that CT stimulates the release of 5-HT, which in turn causes the release of PGE2. The latter substances probably act via a local intramural reflex and contribute to secretion by mechanisms that are independent of cAMP.
Animals↗
Disposition of 5-aminosalicylic acid by olsalazine and three mesalazine preparations in patients with ulcerative colitis: comparison of intraluminal colonic concentrations, serum values, and urinary excretion.
To compare the disposition of 5-aminosalicylic acid (5-ASA) and its acetylated metabolite during treatment with olsalazine and mesalazine, 14 patients with inactive ulcerative colitis were randomly assigned to olsalazine (1 g twice daily) and the mesalazines, Asacol (800 + 400 + 800 mg daily), Pentasa (750 + 500 + 750 mg daily), and Salofalk (750 + 500 + 750 mg daily) in a crossover design trial so that all received each drug for seven days. Intraluminal colonic concentrations of 5-ASA were estimated after five days by the method of equilibrium in vivo dialysis of faeces. A predose serum sample and a 24 hour urine collection were obtained on day seven. The 5-ASA and acetyl-5-aminosalicylic acid (Ac-5-ASA) values were determined by high performance liquid chromatography. Olsalazine almost doubled the colonic concentrations (mean 23.7 (SEM) (1.9) mmol/l) of its therapeutically active ingredient (5-ASA) compared with equimolar doses of Pentasa (12.6 (2.2) mmol/l; p less than 0.0003) and Salofalk (15.0 (2.0) mmol/l; p less than 0.003). At the same time, olsalazine treatment was associated with lower serum concentrations and urinary excretions (p less than 0.05) of 5-ASA and Ac-5-ASA compared with the mesalazine preparations. The low systemic load of 5-ASA provided by olsalazine reduces the potential risk of nephrotoxicity during long term treatment.
Adult↗
A natural flavonoid, IdB 1027, increases gastric luminal release of prostaglandin E2 in healthy subjects.
IdB 1027 is an anthocyanidin pigment occurring in bilberries. In laboratory animals this compound shows gastric protective effects without influencing acid secretion. To study how IdB 1027 would affect gastric luminal release of prostaglandin (PG) E2 and basal fluid and acid secretion, we have carried out 'steady state' perfusions of the stomach in 10 healthy males before and after oral administration of IdB 1027 (600 mg b.i.d.) for 10 days. Two subjects were excluded from the study due to a low recovery of perfusates. Gastric fluid secretion, acidity, and acid output were unaffected during IdB 1027 administration, while a significant rise in luminal concentration (403 (124-910) vs 216 (49-506) pg/ml: median and range; p less than 0.05; n = 8 and luminal release 6.5 (2.2-14.6) vs 1.9 (1.0-8.1) ng/15 min; p less than 0.02; n = 8) of PGE2 occurred. The marked increase in gastric mucosal release of PGE2 may explain the antiulcer and gastroprotective effects of IdB 1027 observed in animal experiments.
Adult↗
[Prostaglandins and the resistance of the gastroduodenal mucosa].
The mechanisms responsible for maintaining the integrity of the gastroduodenal mucosa have been explored intensively in recent years. Prostaglandins seem to play a central role in mucosal defence. Important mechanisms by which prostaglandins may produce cytoprotection include regulation of the thickness and the composition of the mucus layer at the epithelial surface; modulation of active bicarbonate secretion by the surface epithelial cells; hydrophobicity of the surface epithelium; rapid cell proliferation and differentiation after mucosal damage; maintenance of interstitial bicarbonate; and the integrity of the microcirculation--in addition to synthesis of mucosal sulphhydryl groups. A defect mucosal defence is considered the most important pathogenetic factor in the majority of patients with peptic ulcer disease, but it is still unclear whether this is due to a deficiency in endogenous prostaglandins. Important risk factors for developing peptic ulcer disease, such as nonsteroidal antiinflammatory drugs and smoking, depress the formation of endogenous prostaglandins. The question of whether the use of direct cytoprotection may be relevant in ulcer therapy has yet not been solved and the rationale for substitution with prostaglandin analogues is to date empirical.
Animals↗
Inflammatory intermediaries in inflammatory bowel disease.
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Humans↗
Involvement of 5-hydroxytryptamine, prostaglandin E2, and cyclic adenosine monophosphate in cholera toxin-induced fluid secretion in the small intestine of the rat in vivo.
The diarrhea of cholera is considered to rely solely on a cyclic adenosine monophosphate-mediated secretory mechanism. However, both 5-hydroxytryptamine and prostaglandin E2 have been proposed to be involved in the pathogenesis of cholera. In vivo experiments were performed, therefore, in the rat jejunum to investigate the influence of purified cholera toxin on fluid secretion, luminal release of 5-hydroxytryptamine and prostaglandin E2, and formation of mucosal cyclic adenosine monophosphate. Also the effects of ketanserin, indomethacin, verapamil, and nifedipine on the named parameters were studied. Cholera toxin dose-dependently (0.1-0.5 microgram/ml) and time-dependently (1-5 h) increased mean net fluid secretion with a maximum response at 4 h. It also caused a significant (p less than 0.01) rise in release of 5-hydroxytryptamine and prostaglandin E2, in addition to formation of cyclic adenosine monophosphate. The dose-response curve for cholera toxin-induced fluid secretion was shifted to the right by indomethacin (10 mg/kg s.c.) and ketanserin (200 micrograms/kg s.c.), none of which caused a change in cholera toxin-induced release of 5-hydroxytryptamine. However, both agents significantly decreased the release of prostaglandin E2. Verapamil (0.2-9.5 micrograms/min i.a.) and nifedipine (0.05-0.5 microgram/min i.a.) dose-dependently reduced cholera toxin-induced fluid secretion. The estimated local concentrations at half-maximal inhibition were 5 x 10(-7) M verapamil and 5 x 10(-8) M nifedipine, respectively. The cholera toxin-induced increase in release of 5-hydroxytryptamine and prostaglandin E2 and formation of cyclic adenosine monophosphate was unaffected by verapamil. These results support the concept that cholera toxin-induced fluid secretion in vivo is caused, in part, by release of 5-hydroxytryptamine, which in turn stimulates formation of prostaglandin E2.
Animals↗
In vivo profiles of eicosanoids in ulcerative colitis, Crohn's colitis, and Clostridium difficile colitis.
To compare the local release of arachidonic acid metabolites in inflammatory diarrheal disease, in vivo equilibrium dialysis of the rectum was done in consecutive untreated patients with ulcerative colitis (n = 20), Crohn's colitis (n = 10), and Clostridium difficile colitis (n = 7). All patients had endoscopically proven rectal inflammation. Eicosanoid profiles were determined in rectal dialysates by radioimmunoassay after preliminary purification. Concentrations of prostaglandin E2, prostaglandin F2 alpha, and thromboxane B2, but not 6-keto-prostaglandin F1 alpha, were raised in all groups and compared with healthy controls. The highest levels within each group were obtained in patients with widespread epithelial damage, as judged by endoscopy. In patients with ulcerative colitis, an extreme rise in prostaglandin E2 and thromboxane B2 were observed. Similarly, concentrations of leukotriene B4 were substantially increased in ulcerative colitis, but in Crohn's colitis and Clostridium difficile colitis only those patients with rectal ulcerations showed elevations. These findings probably reflect more severe tissue damages in ulcerative colitis, but differences between disease groups in cell-to-cell interaction may also contribute. The data suggest, therefore, that therapeutic inhibition of lipoxygenase pathways may prove more effective in ulcerative colitis than in Crohn's disease.
Adolescent↗