Corticosteroid pretreatment prevents small intestinal mucosal lesion induced by acetic acid-perfusion model in rats

Inhibition of Adenosine Deaminase Attenuates Inflammation in Experimental Colitis

Adenosine modulates the immune system and inhibits inflammation via reduction of cytokine biosynthesis and neutrophil functions. Drugs able to prevent adenosine catabolism could represent an innovative strategy to treat inflammatory bowel disorders. In this study, the effects of 4-amino-2-(2-hydroxy-1-decyl)pyrazole[3,4-d]pyrimidine (APP; novel adenosine deaminase inhibitor), erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA; standard adenosine deaminase inhibitor), and dexamethasone were tested in rats with colitis induced by 2,4-dinitrobenzenesulfonic acid (DNBS). DNBS-treated animals received APP (5, 15, or 45 micromol/kg), EHNA (10, 30, or 90 micromol/kg), or dexamethasone (0.25 micromol/kg) i.p. for 7 days starting 1 day before colitis induction. DNBS caused bowel inflammation associated with decrease in food intake and body weight. Animals treated with APP or EHNA, but not dexamethasone, displayed greater food intake and weight gain than inflamed rats. Colitis induced increment in spleen weight, which was counteracted by all test drugs. DNBS administration was followed by macroscopic and microscopic inflammatory colonic alterations, which were ameliorated by APP, EHNA, or dexamethasone. In DNBS-treated rats, colonic myeloperoxidase, malondialdehyde, and tumor necrosis factor (TNF)-alpha levels as well as plasma TNF-alpha and interleukin-6 were increased. All test drugs lowered these phlogistic indexes. Inflamed colonic tissues displayed an increment of inducible nitric-oxide synthase mRNA, which was unaffected by APP or EHNA, but reduced by dexamethasone. Cyclooxygenase-2 expression was unaffected by DNBS or test drugs. These findings indicate that 1) inhibition of adenosine deaminase results in a significant attenuation of intestinal inflammation and 2) the novel compound APP is more effective than EHNA in reducing systemic and intestinal inflammatory alterations.

Dexamethasone mediates protection against acute pancreatitis via upregulation of pancreatitis-associated proteins

AIM

To examine the influence of dexamethasone on pancreatitis-associated protein (PAP) gene expression using both in vitro and in vivo models of acute pancreatitis and to study how PAP gene expression correlates with severity of pancreatitis.

METHODS

In vitro, IL-6 stimulated pancreas acinar AR42J cells were cultured with increasing concentrations of dexamethasone and assayed for PAP expression (RT-PCR). In vivo, pancreatitis was induced in rats by retrograde injection of 40 g/L taurocholate into the pancreatic duct. Animals were pretreated with dexamethasone (2 mg/kg) daily or saline for 4 d. Pancreata and serum were harvested after 24 h and gene expression levels of PAP I, II and III were measured by RT-PCR. Severity of pancreatitis was based on serum amylase, pancreatic wet weight, and histopathological score.

RESULTS

In vitro, dexamethasone and IL-6 induced a marked transcription of PAP I, II and III genes in AR42J cells at 24 h (P < 0.05 for all comparisons). In vivo, pancreas mRNA levels of PAP I, II or III increased by 2.6-fold, 1.9-fold, and 1.3-fold respectively after dexamethasone treatment, compared with saline treated animals. Serum amylase levels and edema were significantly lower in the dexamethasone group compared with the saline group. Histopathologic evaluation revealed less inflammation and necrosis in pancreata obtained from dexamethasone treated animals (P < 0.05).

CONCLUSION

Dexamethasone significantly decreases the severity of pancreatitis. The protective mechanism of dexamethasone may be via upregulating PAP gene expression during injury.

Mechanisms of protection by pantoprazole against NSAID-induced gastric mucosal damage

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) can be associated with severe adverse digestive effects. In clinical settings, proton pump inhibitors have proven to be effective in preventing and healing NSAID-induced gastroduodenal lesions. The present study investigates the mechanisms of protection afforded by pantoprazole against gastric injury induced by different NSAIDs in rats. Animals were orally treated with indomethacin (100 micromol/kg), diclofenac (60 micromol/kg), piroxicam (150 micromol/kg) or ketoprofen (150 micromol/kg). Thirty minutes before NSAIDs, animals received pantoprazole 6 or 60 micromol/kg orally. Four hours after NSAIDs, the following parameters were assessed: histomorphometric evaluation of gastric mucosal damage; gastric mucosal levels of myeloperoxidase (MPO), malondialdehyde (MDA), reduced glutathione as an index of non-proteic sulfhydryl compounds (GSH), and prostaglandin E2 (PGE2); mucosal cyclooxygenase-1 and -2 (COX-1, COX-2) mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR). Separate experiments were carried out to assay the effects of pantoprazole on gastric acid secretion in pylorus-ligated rats. The in vitro influence of pantoprazole (1-10 microM) on the oxidation of low density lipoproteins (LDLs) induced by copper sulphate was also examined. All NSAIDs elicited mucosal necrotic lesions associated with neutrophil infiltration and reduction of PGE2 levels. Increments of MPO and MDA contents, as well as a decrease in GSH levels, were detected in the gastric mucosa of indomethacin-, piroxicam- or ketoprofen-treated animals. Indomethacin enhanced mucosal COX-2 expression, while not affecting COX-1. At the oral dose of 6 micromol/kg pantoprazole did not affect NSAID-induced mucosal damage, whereas at 60 micromol/kg it markedly reduced injuries provoked by all test NSAIDs. Pantoprazole 60 micromol/kg also reversed the effects of NSAIDs on MPO, MDA, and GSH mucosal contents, without interfering with the decrease in PGE2 levels or indomethacin-induced COX-2 expression. However, at both doses, pantoprazole inhibited acid secretion in pylorus-ligated rats. Furthermore, pantoprazole concentration dependently reduced the in vitro oxidation of LDLs. Our results suggest that besides inhibiting acid secretion, the protection afforded by pantoprazole against NSAID-induced gastric damage depends on a reduction in mucosal oxidative injury, which may also account for an increment of sulfhydryl radical mucosal bioavailability. It is also suggested that pantoprazole does not influence the down-regulation of gastric prostaglandin production associated with NSAID treatment.

Lansoprazole prevents experimental gastric injury induced by non-steroidal anti-inflammatory drugs through a reduction of mucosal oxidative damage

AIM: This study investigated the mechanisms of protection afforded by the proton pump inhibitor lansoprazole against gastric injury induced by different non-steroidal anti-inflammatory drugs (NSAIDs) in rats.

METHODS: Male Sprague-Dawley rats were orally treated with indomethacin (100 µmol/kg), diclofenac (60 µmol/kg), piroxicam (150 µmol/kg) or ketoprofen (150 µmol/kg). Thirty minutes before NSAIDs, animals were orally treated with lansoprazole 18 or 90 µmol/kg. Four hours after the end of treatments, the following parameters were assessed: gastric mucosal PGE2, malondialdehyde (MDA), myeloperoxidase (MPO) or non-proteic sulfhydryl compounds (GSH) levels; reverse transcription-polymerase chain reaction (RT-PCR) of mucosal COX-2 mRNA; gastric acid secretion in pylorus-ligated animals; in vitro effects of lansoprazole (1-300 µmol/L) on the oxidation of low density lipoproteins (LDLs) induced by copper sulphate.

RESULTS: All NSAIDs elicited mucosal necrotic lesions which were associated with neutrophil infiltration and reduction of PGE2 levels. Increments of MPO and MDA contents, as well as a decrease in GSH levels were detected in the gastric mucosa of indomethacin- or piroxicam-treated animals. Indomethacin enhanced mucosal cyclooxygenase-2 expression, while not affecting cyclooxygenase-1. At the oral dose of 18 µmol/kg lansoprazole partly counteracted diclofenac-induced mucosal damage, whereas at 90 µmol/kg it markedly prevented injuries evoked by all test NSAIDs. Lansoprazole at 90 µmol/kg reversed also the effects of NSAIDs on MPO, MDA and GSH mucosal contents, without interfering with the decrease in PGE2 levels or indomethacin-induced cyclooxygenase-2 expression. However, both lansoprazole doses markedly inhibited acid secretion in pylorus-ligated rats. Lansoprazole concentration-dependently reduced the oxidation of LDLs in vitro.

CONCLUSION: These results suggest that, besides the inhibition of acid secretion, lansoprazole protection against NSAID-induced gastric damage depends on a reduction in mucosal oxidative injury, which is also responsible for an increment of sulfhydryl radical bioavailability. It is also suggested that lansoprazole does not influence the down-regulation of gastric prostaglandin production associated with NSAID treatment.

Indomethacin-induced ileitis is associated with tensiometric, vascular and oxidative changes in the experimental rat model

BACKGROUND

Indomethacin-induced enteritis is a model of inflammatory bowel disease.

MATERIALS AND METHODS

To further characterize this model, rats received two injections of indomethacin (7.5 mg kg(-1)) 24 h apart and histological damage of intestinal mucosa, oxidative stress, alterations of intestinal motility and mesenteric vascular bed (MVB) reactivity were investigated after 5 days.

RESULTS

The results show that indomethacin caused several histological and functional changes at the ileal level. In particular, response to carbachol as well as the nonadrenergic-noncholinergic inhibitory response to electrical field stimulation (EFS) was lower in the treated than control rats. Moreover, nitric oxide (NO)-component of the inhibitory response was higher in the treated than control rats. Mesenteric vessels preparations from the treated rats showed increased noradrenaline (NA)-induced perfusion pressure, whereas relaxant responses to acetylcholine, although not significantly reduced in the treated rats, had a higher nitrergic component. This finding suggests that vascular dysfunction may contribute to chronic inflammation. Indomethacin injection also determined acute and severe oxidative stress in ileum mucosa.

CONCLUSIONS

In conclusion, our study contributes to further characterize the rat model of indomethacin-induced enteritis and suggests that it is suitable for drug screening in rats, as this model can be obtained in a very short period and is simple and reproducible.

Effects of in vivo treatment with interleukins 1beta and 6 on rat mesenteric vascular bed reactivity

1. Inflammatory bowel disease (IBD) is a condition that involves proinflammatory cytokines such as interleukins 1beta and 6 (ILs). In this disease, it has been shown that an abnormal microcirculatory system is implicated. 2. Therefore, the effects of in vivo treatment for three days with interleukins 1beta and 6 were investigated on rat isolated mesenteric vascular bed (MVB). 3. A significant concentration-dependent increase in vascular response to noradrenaline (NA) was found, with a significant difference in Emax between control (93.01 +/- 16.78 mmHg) and treated preparations (137.91 +/- 5.20 mmHg). Endothelin-1(ET-1) induced a significantly greater increase of perfusion pressure in treated rats in comparison with control rats at the highest concentration used (0.1 microm). 4. The concentration-dependent decrease of perfusion pressure induced by acetylcholine (ACh) in MVB precontracted with NA was significantly reduced in specimens from treated rats in comparison with control rats, with a significant difference in Emax between control and treated preparations. 5. Perivascular nerve stimulation (PNS) evoked contractions with no difference between treatments. Similarly, no difference in relaxant effect was found after PNS in specimens precontracted with NA, in the presence of guanethidine. 6. These findings indicate that the precocious inflammation acts only at postsynaptic level, facilitating vascular contraction. These data seem to support the hypothesis that vascular dysfunction caused by overproduction of ILs may contribute, among other immunological factors, to vasculitis in IBD that leads to intestinal ischaemia through vasoconstriction.