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The Possible Role of Mucosal Endogenous Prostacyclin in Human Peptic Ulcer Disease
Gabor A. Balint*†
*Laboratory of Clinical Pharmacology, Department of Psychiatry, New Clinics
Faculty of Medicine, University of Szeged, Szeged, Hungary
†Formerly First Department of Medicine, Szeged University Medical School, Szeged, Hungary
‡Department of Internal Medicine; Second Municipal Hospital, Szeged, Hungary.
Key words: peptic ulcer disease, smoking, endogenous (mucosal) prostacyclin
Smoking is damaging to the gastric and duodenal mucosa. The target of this action is (among other things) the endogenous (mucosal) prostacyclin content.
Objectives: Because smoking is often associated with peptic ulcer disease, we investigated the possible connection of endogenous prostacyclin to smoking in the pathology of peptic ulceration
Methods: Investigations were performed using gastroduodenal mucosal biopsy specimens in which the endogenous prostacyclin levels were determined by radioimmunoassay.
Results: In healthy adults, the gastroduodenal mucosal specimens from women showed a trend for a higher endogenous prostacyclin content than those from men. The possible physiological relevance of this phenomenon is not understood. This difference is also present in peptic ulcer disease. Conversely, in both gastric and duodenal ulceration, there is a trend for a lower endogenous prostacyclin levels. However, moderate smoking seems to increase the endogenous prostacyclin levels.
In an earlier pilot-study, it was reported that a tendency toward decreased endogenous PGI-2 (prostacyclin, 6,9?-epoxy-11?,15S-dihydroxy-prosta-5Z,13E,17Z-trien-1-oic acid) production in human gastric and duodenal mucosa in peptic ulcer disease (PUD).1 Moreover, Endoh and Leung2 found that smoking cigarettes had an unwanted effect on the gastric mucosa in humans. Recently, Ma et al.3 reported similar results. One of the possible targets is the endogenous PG1-2 content, which was decreased significantly by smoking. Similar observations were made earlier by Balint.4 Because smoking has a positive correlation with PUD,5 it is interesting to investigate the possible role of endogenous PGI-2 in ulcer pathogenesis.
PATIENTS AND METHODS
Investigations were performed using gastroduodenal mucosal biopsy specimens from patients with gastrointestinal complaints in whom careful retrospective clinical check-up failed to show peptic ulceration, inflammatory gastric diseases, or tumor. The presence of PUD was also formally excluded using endoscopy. This group of patients served as the control group.
The presence of active PUD (either gastric or duodenal) was proved by gastroduodenoscopy with consecutive histologic investigation to exclude malignancy. (Ethical Commission’s Agreement No. 75/1987/SZOTE.) Before gastroduodenoscopy (using a gastroduodeno fiberoscope, Olympus GIF-Q), the biopsy donors fasted overnight, with no systemic premedication. Nonsteroidal anti-inflammatory drug therapy (including aspirin) and alcohol consumption were excluded for a week before gastroduodenoscopy.
The patients were aged 21 to 66 years (men) and 25 to 60 years (women). They were divided into groups on the basis of their illness, gender, and smoking habits:
—Healthy nonsmoking men and women;
—Healthy smoking men and women;
—Nonsmoking (men and women) with gastric ulcer;
—Nonsmoking (men and women) with duodenal ulcer,
—Smokers (men and women) with gastric ulcer; and
—Smokers (men and women) with duodenal ulcer.
—Smokers were defined as those who had smoked 20 or more cigarettes daily for at least the past year.
No endoscopic differences were found between the healthy smokers and nonsmokers and the proportion of Helicobacter pylori-positive versus H pylori-negative patients in each group was not significantly different using a routine rapid urea breath test.6,7 The endogenous PG-I-2 level was determined throughout using radioimmunoassay. 6-ketoPGF1a is the stable degradation product of PG-I-2, and indicates PG-I-2 formation.8 6-ketoPGF1a was measured using RK-16M” kits (manufactured by the Institute of Isotopes of the Hungarian Academy of Sciences, Izinta, Budapest; lot No. 90508A).
The cross-reactivities of the kits used at 50% B/Bo values were 6-ketoPGF1a 100.0%; 6-ketoPGF1a, 2.0%, PGE-1, 1.2%; 6-ketoPGF2a 0.8% 6-ketoPGE1, 3.5%; PGD2, 0.1%; PGE2, 1.4%; PGA2, 0.01%; PGB2 < 0.01%.
The assay parameters according to the manufacturer (mean ± SD, n = 10 in all points measured) were NSB/TC (%), < 5; B0/TC (%), 44 ± 8; ED-80, 2.65 ± 0.32 (pg/tube); ED-50, 10.40 ± 1.50 (pg/tube); ED-20 50.90 ± 3.49 (pg/tube); detection limit, 1.13 ± 0.297 (pg/tube).
The extraction of 6-ketoPGF1a from the mucosal biopsy specimens was performed using acetone-petroleum-ether-ethylacetate.9 Emphasis was given to rapid processing, and the procedure was performed in an ice bath. Samples (from the biopsy specimens) were also sent for protein determination.10 The recovery of the extraction procedure was at least 90%, while the detection limit (sensitivity) was 5 pg 6ketoPGF1a/mg protein. All results are given in pg 6-ketoPGF-1a/mg protein.
Intra- and interassay coefficients of variation were less than 5%. The “procedure blank” (buffer sample subjected to exactly the same treatment as samples) showed no detectable PGI-2-like activity, that is, it was below the detection limit. Within each group, mean ± SEM was calculated and analyzed statistically by analysis of variance. Significant differences were assumed when P was less than 0.05.
The results of the investigation are presented in Tables 1 and 2. Healthy women patients seem to show a trend for more endogenous PGI-2 than men, both nonsmokers and smokers. Moreover, it is also evident that smoking generally decreases the endogenous PGI-2 levels in patients of either gender. Women but not men smokers with gastric ulceration have less antral endogenous PGI-2.
The endogenous PGI-2 levels in the fundic mucosa of men with PUD were not significantly different in smokers and nonsmokers. However, female smokers with gastric ulcer and nonsmoking women with duodenal ulcer showed lower endogenous PGI-2 levels. In the duodenal mucosa, the most important changes were seen in women. In duodenal ulceration, the endogenous PGI-2 levels were higher in smokers, and lower in nonsmokers compared with healthy controls.
The pathogenesis of PUD is complex, and a single abnormality is unlikely to explain why ulcers develop. An imbalance among protective and ulcerogenic processes is probably one of the several factors that may lead to gastrointestinal ulceration. Endogenous PGI-2 is one of the most important natural protective substances in the gastrointestinal mucosa.11 In healthy people, there is a trend toward a higher endogenous PGI-2 content in women compared with in men, similar to our previous data12 in colonic mucosa. These gender differences are not clearly understood.13
Smoking exerts an unfavorable effect on the gastrointestinal tract.14,15 One of the targets of this action seems to be the endogenous PGI-2 content of the mucosa.16-18 Results in the literature are scarce regarding the possible relationship of human gastroduodenal enddogenous PGI-2 levels to smoking in PUD.4
On the basis of the present investigation, it seems that smoking has a damaging effect on the endogenous PG1-2 levels in women smokers with gastric ulceration. In this group, mucosa from the different regions had less endogenous PGI-2 than in healthy controls. A similar picture was obtained, also regarding gastric ulcers, in nonsmoking men. In the other groups, smaller antral or duodenal changes were seen. There were also numerous statistically significant differences in results that may be of no clinical relevance.
The noticeable trend for more endogenous PGI-2 in smokers with duodenal ulceration raises an interesting problem. According to our previous data, it seems that under certain circumstances smoking, as repeated pathologic stimulus, can elicit the phenomenon. An elevation of the endogenous PGI-2 level might be part of the general defensive mechanism against noxious stimuli. It was also established earlier that in the gastroduodenal mucosa, the damaging and reparative processes run simultaneously.11 Moreover, Mine et al.19 state that the healing of gastric ulcers depends on gastric endogenous PG-synthesis. However, there are marked differences in the mechanisms of gastric and duodenal ulceration.20 We believe that the findings draw attention once again to the role of smoking in the development and healing of PUD. The difference between PGI-2 levels in the antral mucosa of nonsmoking men and women with gastric ulcers is interesting but not understood. However, perhaps it relates to the fact that PUD is more common in men than in women. Therefore, perhaps the higher endogenous PGI-2 content provides better protection.
1. Balint GA, Nafradi J: Changes of mucosal endogenous prostacyclin level in human peptic ulcer disease. Acta Med Hung 48:189–195, 1991.
2. Endoh K, Leung FW: Effects of smoking and nicotine on the gastric mucosa. Gastroenterology 107:864–878, 1994.
3. Ma L, Chow JY, Cho CH: Cigarette smoking delays ulcer healing: Role of constitutive nitric oxide synthase in rat stomach. Am J Physiol 276:G238–G248, 1999.
4. Balint GA: Smoking exerts unfavourable effect on human gastrduodenal mucosal endogenous prostacyclin level. East Afr Med J 66:535–537, 1989.
5. Grossmann MT: Peptic ulcer: Pathogenesis and pathophysiology. In: Beeson PB, McDermott W, Wyngaarden JB, Eds: Cecil Textbook of Medicine, 15 Ed. Philadelphia: WB Saunders; 1985:1502–1507.
6. Graham DY, Klein PD, Evans DJ, et al: Campylobacter pylori detected noninvasively by the 13C-urea test. Lancet 1174–1177, 1987.
7. Dill S, Payne-James JJ, Misiewicz JJ, et al: Evaluation of 13C-urea breath test in the detection of Helicobacter pylori and in monitoring the effect of tripotassium dicitratobismuthate in non-ulcer dyspepsia. Gut 31:1237–1241, 1990.
8. Myatt L, Jagee M, Lewis PJ, O’Grady J, Eds: Clinical pharmacology of prostacyclin. New York: Raven Press; 1981:25–35.
9. Gréen K, Hamber M, Samuelsson B, Frölich JC: Extraction and chromatographic procedures for purification of prostaglandins, thromboxanes, prostacyclin and their metabolites. In: Frölich JC, Ed: Advances in prostaglandin and thromboxane research. Vol 5. Methods in prostaglandin research. New York: Raven Press; 1978:1–38.
10. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ: Protein measurement with the Folin phenol reagent. J Biol Chem 193:265–275, 1951.
11. Balint GA: Experimental and clinical observations on the role of endogenous and on the effect of exogenous prostacyclin in gastric mucosa. Exp Toxic Pathol 46:37–40, 1994.
12. Balint GA, Nagy F: In healthy humans the colonic mucosal endogenous prostacyclin content shows a sex difference. J Clin Gastroenterol 15:174, 1992.
13. Balint GA, Nagy F, Nafradi J: Gastrointestinal mucosa: a new place for sexual dimorphism in humans? Annual Conference of the Hungarian Society of Gastroenterology, Balatonaliga, June 9–13, 1998.
14. Miller G: Smoking delays gastric emptying of solids. Gut 30:50–53, 1989.
15. Müller-Lissner SA: Bile reflux is increased in cigarette smokers. Gastroenterology 90:1205–1209, 1986.
16. McCready DR: Cigarette smoking reduces human gastric luminal prostaglandin E–2. Gut 26:1192–1196, 1985.
17. Fedi P: Cigarette smoking increases gastric luminal prostaglandin-F-2alpha and thromboxane-B-2 in healthy smokers. Digestion 46:27–34, 1990.
18. Balint GA: On a possible interrelationship among smoking, gastric ulceration and endogenous prostacyclin. Exp Toxic Pathol 54:39–41, 2002.
19. Mine T, Kataoka J, Fujisaki E, et al: Healing of chronic gastric ulcer depends on gastric mucosal prostaglandin synthesis. Hepatogastroenterology 41:111–115, 1994.
20. Balint GA: On the biochemical background of cysteamine-induced duodenal ulceration in the rat. Scand J Gastroenterol 28:423–426, 1993.
Table 1. The Effect of Smoking on Mucosal Endogenous Prostacyclin Levels in Healthy Humans
n 6ketoPGF1a pg/mg protein (x) Fundus Duodenum
Non–smokers 21 476 ± 85 512 ± 88 494 ± 97
Smokers 23 349 ± 71 336 ± 64* 373 ± 77
Nonsmokers 23 683 ± 96† 680 ± 110 649 ± 103‡
Smokers 20 605 ± 102§ 589 ± 93¶ 460 ± 94
xProstacyclin has been estimated in 6ketoPGF1a form.
*P < 0.05 vs 1.
†P < 0.05 vs 1.
‡P < 0.05 vs 1.
§P < 0.05 vs 2.
¶P < 0.05 vs 2.
Analysis of variances; mean values ± SEM.
Table 2. Changes of Mucosal Endogenous Prostacyclin Levels in Human Peptic Ulcer Disease
n 6ketoPGF1a pg/mg protein (x) Fundus Duodenum
Control 21 476.4 ± 84.6 512.4 ± 88.4 493.7 ± 97.2
Gastric 19 360.2 ± 79.1† 319.9 ± 82.4 410.4 ± 91.6
Duodenal 23 605.4 ± 101.5 587.4 ± 104.7 332.4 ± 72.8
Control 23 349.1 ± 70.6‡ 336.1 ± 64.3§ 372.6 ± 77.4
Gastric 20 351.9 ± 82.7 369.0 ± 77.1 442.9 ± 96.2
Duodenal 25 410.4 ± 81.5 407.9 ± 81.6 300.7 ± 72.7
Control 23 682.5 ± 96.2 680.2 ± 109.9 649.2 ± 103.3
Gastric 18 671.6 ± 107.5 594.7 ± 100.4 672.6 ± 110.8
Duodenal 19 343.6 ± 53.2¶** 348.8 ± 79.9¶** 379.0 ± 81.1**
Control 20 604.8 ± 101.5 588.5 ± 93.3 460.3 ± 94.2**††
Gastric 15 284.1 ± 68.8†¶ 296.4 ± 64.3†¶ 391.2 ± 82.9†
Duodenal 17 760.4 ± 112.3 667.7 ± 101.7 663.1 ± 103.5
Analysis of variances; mean values ± SEM.
*Prostacyclin has been estimated in 6ketoPGF1a form.
†P < 0.05 vs 8.
‡P < 0.05 vs 3.
§P < 0.05 vs 1.
¶P < 0.05 vs 10.
**P < 0.05 vs 12.
§§P < 0.05 vs 7.
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