The effect of cigarette smoke on gastroduodenal mucosal endogenous prostacyclin level (experimental and clinical observations)

On a possible interrelationship among smoking, gastric ulceration and endogenous prostacyclin

Investigating either in animals or in humans it seems that smoking exerts an unfavourable effect on the gastric mucosa. The target of this action (among others) is the endogenous prostacyclin content. In gastric ulceration there is a tendency toward decreased endogenous prostacyclin activity even in non-smoker patients, the decrease of which is more pronounced in smokers. The results of animal and human investigations draw attention once again to a possible role of smoking in the development and healing of peptic ulcer disease. Therefore it is always useful for sufferers to give up smoking.

Gastric mucosal endogenous prostacyclin levels are different in Brattleboro rats compared with Wistar strain

Homozygous Brattleboro rats were investigated and compared to normal (physiological) Wistar strain rats regarding their gastric mucosal endogenous prostacyclin (PG-I(2)) level. It seems that the Brattleboro animals have a significantly lower level of this important protective material. Wistar rats having an artificial pituitary stalk lesion (which is the artificial equivalent of homozygous Brattleboro animals) showed no differences in endogenous mucosal prostacyclin level compared to normal Wistar rats. Therefore, we concluded that this hitherto unknown property of the homozygous Brattleboro rats is genetically determined.

Possible role of endogenous prostacyclin in the maintenance of hepatic integrity in rat

Exogenously administered prostaglandins are reported to be involved in hepatic regeneration, i.e. they hinder liver cell injury and cell-death induced by different toxic noxae. In the pertinent literature no data are available regarding the role of endogenous (tissue) prostaglandins in hepatotoxic processes. In subchronic carbon-tetrachloride intoxication (800 mg/kg twice a week, s.c., for 12 weeks) the endogenous prostacyclin level showed a transient and significant elevation signalling (similarly to the gastrointestinal tract) the process of protective mechanisms. This tenet was further strengthened by the concomitant decrease of serum ALT and AST levels. Continuing the carbon-tetrachloride treatment, finally not only the endogenous prostacyclin synthesising capacity of the liver but the hepatic cells themselves were also destroyed. According to the author's best knowledge these are the first data in the literature which try to enlighten the protective role of endogenous prostacyclin in hepatotoxic processes.

Mechanistic study of adverse actions of cigarette smoke exposure on acetic acid-induced gastric ulceration in rats

Cigarette smoking is associated with peptic ulceration in humans. A mechanistic study of the potentiating effects of cigarette smoking on acetic acid-induced gastric ulceration in rats was hence performed. Rats were exposed to 0, 2 or 4% of cigarette smoke for three 1-hr periods during the 24 hr starvation before ulcer induction. Cigarette smoke exposure potentiated ulcer formation which was accompanied by a reduction of gastric blood flow at the ulcer base and ulcer margin. Further studies showed that cigarette smoke exposure alone did not cause any macroscopic injury in the stomach but significantly decreased the basal gastric blood flow in a concentration-dependent manner, which was coupled with an increase in mucosal xanthine oxidase (XO) activity. Pretreatment with allopurinol (Allo, 5 mg/kg, i.v.), a XO inhibitor, partially prevented the potentiating effect of cigarette smoke exposure on ulcer formation and also significantly improved the gastric blood flow. Ulcer induction itself dramatically increased constitutive nitric oxide synthase (cNOS) activity and prostaglandin E2 (PGE2) level in the gastric mucosa. However, the increment of cNOS activity but not PGE2 level was markedly attenuated by cigarette smoke exposure. Sodium nitroprusside (SNP, 25 or 50 microg/kg, i.v.), a nitric oxide (NO) donor, completely abolished the potentiating effect of cigarette smoke exposure on ulcer formation and also reversed the adverse effect on gastric blood flow. Thus, XO activation and cNOS reduction in the gastric mucosa are closely associated with the potentiating action of cigarette smoke exposure on ulcer formation in rats.

Effects of smoking and nicotine on the gastric mucosa: a review of clinical and experimental evidence

Epidemiological and experimental evidence have shown that nicotine has harmful effects on the gastric mucosa. The mechanisms by which cigarette smoking or nicotine adversely affect the gastric mucosa have not been fully elucidated. In this report, clinical and experimental data are reviewed. The effects of nicotine from smoking on gastric aggressive or defensive factors are discussed. Nicotine potentiates gastric aggressive factors and attenuates defensive factors; it also increases acid and pepsin secretions, gastric motility, duodenogastric reflux of bile salts, the risk of Helicobacter pylori infection, levels of free radicals, and platelet-activating factor, endothelin generation, and vasopressin secretion. Additionally, nicotine impairs the therapeutic effect of H2-receptor antagonists and decreases prostaglandin synthesis, gastric mucosal blood flow, mucus secretion, and epidermal growth factor secretion. Although many of the studies provide conflicting results, the bulk of the evidence supports the hypothesis that nicotine is harmful to the gastric mucosa.

Experimental and clinical observations on the role of endogenous and on the effect of exogenous prostacyclin in gastric mucosa. A personal view

In the gastric mucosa the exogenously administered prostacyclin seems to have a polyphasic effect which contains the following consecutive steps: 1. Binding to the cell surface; 2. Effect on the intracellular "second messenger system", i.e. on the cyclic nucleotide (cAMP, cGMP) turnover; 3. Activation of the calmodulin-system; 4. cAMP-dependent protein kinase activation; Nucleic acid,--DNA,RNA,--changes; 6. Influence on protein synthesis and finally; 7. New cell formation. On the other hand, the endogenous (mucosal) prostacyclin exerts a natural protection against different damaging noxae.

Gastric mucosal calmodulin changes in different experimental ulcer models of rat

It seems that the mucosal CaM content does not play a significant role in the pathomechanism or the regeneration of (experimental) gastric ulcers of rat.