Effect of the COX-2 Selective Inhibitor L-745,337 on Inflammation and Organ Prostaglandin E2 (PGE2) Levels in Adjuvant Arthritic Rats

The anti-inflammatory activity of the cyclooxygenase-2 inhibitor, L745,337, was assessed in adjuvant arthritic rats (AA). The relationship between PGE₂ organ levels and drug activity or adverse effects was determined. Arthritic rats were orally treated for two weeks with L-745,337 (0.1, 1 and 5 mg/kg/day), indomethacin (1 mg/kg/day) or vehicle and paw swelling was determined. At the end of the study, samples from paw, stomach (wall and mucosa) and kidney were obtained from rats with or without treatment at high doses of L-745,337 or indomethacin and PGE₂ levels were determined. The L-745,337 anti-inflammatory effective-dose-50 was 0.4 mg/kg. Maximal anti-inflammation was obtained with L-745,337 or indomethacin at doses of 5 and 1 mg/kg respectively. L-745,337 showed anti-arthritic activity. No stomach ulcers appeared in either untreated or treated arthritic and healthy control rats. In AA rats, PGE₂ increased in paw, stomach wall, gastric mucosa and kidney. These levels were lower in all organs after both drugs but not below PGE₂ control levels.     

Role of nitric oxide in indomethacin-induced gastric mucosal dysfunction in the rat

The present study was undertaken to explore the role of nitric oxide (NO) in the pathogenesis of experimental non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy. We assessed the role of NO inhibition and donation in indomethacin-induced gastric mucosal dysfunction. The stomach was perfused with vehicle (control) for 20 min, followed by indomethacin (10 mg ml-1 in 1 25 % sodium bicarbonate, pH 8 4) for 120 min. NG-nitro-L-arginine methyl ester (L-NAME, 5 and 10 mg kg-1, I.V. bolus), L-arginine, D-arginine (100 mg kg-1 I.V. bolus, 10 mg kg-1 h-1, 2 h infusion) and the NO donor glyceryl trinitrate (GTN) were given at the same time (20, 40 and 80 microg kg-1 min-1, 15 min infusion) as perfusion with indomethacin was started. Epithelial permeability was quantified by measuring blood-to-lumen clearance of 51Cr-labelled EDTA. Indomethacin caused a 20-fold increase in 51Cr-EDTA leakage compared with that of the control group. Treatment with L-NAME or L-arginine did not affect the indomethacin-induced alterations in mucosal permeability. Administration of GTN (20 microg kg-1 min-1) significantly reduced the indomethacin-induced mucosal dysfunction. By contrast, higher doses of GTN (80 microg kg-1 min-1) exacerbated epithelial dysfunction induced by indomethacin. Elevated levels of carbonyls and myeloperoxidase (MPO) observed after indomethacin administration were significantly reduced, to the control values, when GTN (20 microg kg-1 min-1) was administered along with indomethacin. These data suggest that NO from exogenous sources can exert a dual action on the integrity of the gastric mucosa challenged by indomethacin. Low doses of GTN can prevent mucosal dysfunction induced by indomethacin, while higher doses of GTN may exacerbate the increases in epithelial permeability.     

Sulphasalazine and experimental stress ulcers

The effects of sulphasalazine on gastric ulceration induced by restraint at 4°C (stress) for 2 h were studied in rats. Doses of 63 or 125 mg/kg s.c., which had no effect on stomach wall prostaglandin E₂ (PGE₂) levels, prevented stress ulceration but not the lesions produced by indomethacin. Stress significantly increased gastric glandular mucosal PGE₂ levels. Indomethacin pretreatment (20 mg/kg, p.o.) markedly reduced PGE₂ levels in the same region of the stomachs, and worsened stress-induced lesion formation. Pretreatment with sulphasalazine of animals given indomethacin and then subjected to stress did not appear to affect the indomethacin component of indomethacin-stress ulceration. Oral administration of PGE₂ 200 g/kg significantly elevated gastric PGE₂ levels, but had no effect on stress ulceration.It appears that neither the antiulcer activity of sulphasalazine nor stress-induced ulceration is associated with gastric tissue PGE₂ increase or decrease, respectively. The protective mechanism may result from the ability of sulphasalazine to inhibit lipoxygenase activity.     

Comparison of the ulcerogenic properties of tepoxalin with those of non-steroidal anti-inflammatory drugs (NSAIDs)

The ability of tepoxalin to render the gastric mucosa susceptible to injury by a topically applied irritant was compared to that of indomethacin, naproxen and diclofenac. While the three NSAIDs significantly increased the extent of mucosal damage at doses in the 1–30 mg/kg range, tepoxalin failed to significantly augment damage at doses of up to 300 mg/kg. Daily treatment with tepoxalin (10–100 mg/kg) for 4 days also did not significantly affect the susceptibility of the gastric mucosa to damage. The absence of ulcerogenic properties of tepoxalin at doses previously shown to be anti-inflammatory may be related to its relative lack of activity as an inhibitor of gastric prostaglandin synthesis, or to its 5-lipoxygenase inhibitory activity.     

消炎痛对醋氨酚所致小鼠肝脏损伤的保护作用

消炎痛预处理对醋氨酚所致小鼠肝损伤有明显的保护作用。300mg/kg剂量的醋氨酚引起严重的肝损伤,如果在给醋氨酚前24小时皮下一次注射消炎痛(10mg/kg),则损伤明显减轻。经消炎痛预处理动物的SGPT由对照的组1666±43下降到554±153 u/100ml,组织学检查也明显减轻,500mg/kg剂量的醋氨酚引起的死亡率由90％降到45％。小鼠经苯巴比妥钠(80mg/kg)处理三天,以增加细胞色素P_(450)含量,此时醋氨酚引起的肝损伤加重,且由消炎痛诱导的肝保护作用被消除。     

In vitro and in vivo antioxidant activity of ambroxol

Abstract In addition to a mucolytic action, ambroxol has antioxidant and anti-inflammatory properties. The antioxidant effects of ambroxol were studied both in vitro and in vivo. In vitro methods, such as (1) inhibition of hyaluronic acid degradation induced by hydroxy radicals and (2) standard lipid peroxidation assay in rat liver mitochondria and gastric mucosa, induced by tert-butyl hydroperoxide, were used. The in vivo approach was based on the study of the protective effect of pretreatment with ambroxol in a rat model of gastric corpus and antral lesions, induced by indomethacin. The inhibition of the degradation of hyaluronic acid was measured as a change of its viscosity; ambroxol (1,000 µl/l) reduced the degradation by 93%. Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Ambroxol (10 mmol/l) inhibited lipid peroxidation by 96% in the rat liver mitochondria, and by 74% in the gastric mucosa. In vivo, ambroxol was administered p.o. at a dose of 10, 30, and 50 mg/kg, at 5, 30, and 60 min prior to indomethacin administration. The highest inhibition of the number of corpus gastric lesions and lowering of the lesion index (38% and 62%, respectively) was shown after the administration of 50 mg/kg, 30 min before indomethacin administration. Antral lesions were inhibited to a lesser extent by the same dose of ambroxol, administered 30 min before indomethacin treatment. Inhibition of the number of antral lesions reached 27% and the total area of the gastric damage was even larger (the ulcer index reached -5%).     

In vitro and in vivo antioxidant activity of ambroxol

In addition to a mucolytic action, ambroxol has antioxidant and anti-inflammatory properties. The antioxidant effects of ambroxol were studied both in vitro and in vivo. In vitro methods, such as (1) inhibition of hyaluronic acid degradation induced by hydroxy radicals and (2) standard lipid peroxidation assay in rat liver mitochondria and gastric mucosa, induced by tert-butyl hydroperoxide, were used. The in vivo approach was based on the study of the protective effect of pretreatment with ambroxol in a rat model of gastric corpus and antral lesions, induced by indomethacin. The inhibition of the degradation of hyaluronic acid was measured as a change of its viscosity; ambroxol (1,000 microl/l) reduced the degradation by 93%. Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Ambroxol (10 mmol/l) inhibited lipid peroxidation by 96% in the rat liver mitochondria, and by 74% in the gastric mucosa. In vivo, ambroxol was administered p.o. at a dose of 10, 30, and 50 mg/kg, at 5, 30, and 60 min prior to indomethacin administration. The highest inhibition of the number of corpus gastric lesions and lowering of the lesion index (38% and 62%, respectively) was shown after the administration of 50 mg/kg, 30 min before indomethacin administration. Antral lesions were inhibited to a lesser extent by the same dose of ambroxol, administered 30 min before indomethacin treatment. Inhibition of the number of antral lesions reached 27% and the total area of the gastric damage was even larger (the ulcer index reached -5%).     

大黄对胃粘膜保护作用与胃粘膜屏障和前列腺素E_2的关系

本工作研究大黄对胃粘膜的保护作用与粘膜屏障和粘膜前列腺素E_2的关系。实验结果表明;(1)胃饲大黄(0.5g/100g体重)能显著抑制乙醇造成的大量K~ 离子外流;(2)胃饲大黄能有效提高胃粘膜前列腺素E_2含量,还可明显减弱消炎痛对胃粘膜前列腺素E_2合成的抑制作用。(3)预先注射消炎痛(5mg/kg)能抑制大黄对前列腺素E_2合成的促进作用,但不能阻断大黄对胃粘膜的保护作用。结果提示:大黄保护胃粘膜作用与促进粘膜前列腺素E_2合成和加强胃粘膜屏障有关。     

Role of neutrophils in indomethacin-induced gastric mucosal lesions in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) cause clinically important gastric damage by several mechanisms. In order to evaluate the role of neutrophil infiltration in lesion formation, tissue myeloperoxidase activities were assessed in different gastric layers of the stomach both in rats with normal neutrophil levels and in neutropenic rats. Sprague-Dawley rats were treated either with indomethacin (Indo; 25 mg/kg, s.c.) or the vehicle. A group of rats were made neutropenic by administration of methotrexate (MTX; 2.5 mg/kg i.p.) once a day for 3 days. The stomachs were removed for the determination of lesion index, glutathione, lipid peroxide levels, protein oxidation and tissue myeloperoxidase activities. MTX treatment appeared to reduce neutrophil infiltration significantly while producing insignificant effects on eosinophils and macrophages. Indo administration caused multiple gastric lesions and treatment with MTX significantly reduced lesion index. In rats treated with Indo, neither glutathione nor LP levels showed any significant changes but the protein oxidation was significantly higher than that of other groups. The MPO level of gastric mucosa was increased in Indo-treated rats and reversed by MTX pretreatment. The results of the present study indicate that neutrophil infiltration in the gastric mucosa of rats may be involved in the pathogenesis of NSAID-induced gastric mucosal injury, but no correlation was found between lesion formation and protein oxidation in the gastric mucosa.     

Protective effect of a cysteine prodrug and antioxidant,L-2-oxothiazolidine-4-carboxylate,against ethanol-induced gastric lesions in rats

Earlier studies have suggested an important role of glutathione (GSH) in cytoprotection against free radicals induced oxidative damage. This study reports gastroprotective effects of a cysteine precursor, L-2-oxothiazolidine-4-carboxylate (OTC), in experimental models of gastric secretion and ulceration. Acid secretion studies (volume and acidity) were undertaken in pylorus-ligated rats whereas the gastric lesions were induced by ethanol. Different groups of animals were treated with OTC (0, 100, 200 and 400 mg/kg). The levels of gastric wall mucus, nonprotein sulfhydryls (NP-SH) and myeloperoxidase (MPO) were measured in the glandular stomach of rats following ethanol-induced gastric lesions. Both medium and high doses of OTC significantly reduced the volume and acidity of gastric secretion in pylorus-ligated rats. Pretreatment with OTC significantly and dose-dependently attenuated the formation of ethanol-induced gastric lesion. OTC significantly protected the gastric mucosa against ethanol-induced depletion of gastric wall mucus, NP-SH and MPO. The gastroprotective effects of OTC may be attributed to its ability to inhibit neutrophils activity and replenish GSH demand.     

Role of lipid peroxidation in protection of rats by rebamipide against gastric mucosal lesions induced by stress plus indomethacin

The roles of lipid peroxidation and prostaglandins (PGs) in the protective effect of rebamipide against gastric lesions in rats induced by stress plus indomethacin were investigated. Lesions of the gastric mucosa were induced within 3 h by restraint in water (23°C) plus intraperitoneal injection of indomethacin (20 mg/kg) but not by either of these treatments alone. Lipid peroxidation, measured as TBA reactive substances, was increased by stress + indomethacin treatment and the increase in TBA reactive substances was closely related to the lesion score (P < 0.01). This treatment also reduced the release of PGE₂ from the gastric mucosa, the reduction being related with the lesion score (P < 0.01). Teprenone, an inducer of endogenous PGE₂, did not inhibit the induction of gastric lesions by stress + indomethacin. Rebamipide injected subcutaneously dose-dependently inhibited the induction of lesions at doses of 3–30 mg/kg. At a dose of 30 mg/kg, it inhibited the increase of TBA reactants in the gastric mucosa, but did not completely restore PGE₂ release. In the rebamipide-treated group, a significant correlation (P < 0.01) was found between the lesion score and the changes in TBA reactants, but not the PG levels. These results indicate that inhibition of lipid peroxidation may be an important factor in the protective effect of rebamipide against gastric lesions in rats induced by stress + indomethacin.     

REV 5901 and Ly 171,883 protect rat gastric mucosa against ethanol-induced damage

The effect of the leukotriene antagonist, Ly 171,883, or the 5-lipoxygenase inhibitor, REV 5901, on ethanol-induced gastric lesion formation in the rat was investigated. Pretreatment with REV 5901 resulted in a dose dependent decrease in lesion length. Doses of 32 and 64 mg/kg induced nearly complete protection against ethanol, while doses of 1 and 8 mg/kg were much less effective. With Ly 171,883, 32 and 64 mg/kg doses less dramatically reduced lesion length. These findings implicate products of the 5-lipoxygenase pathway in the production of ethanol-induced gastric lesions.     

Serotonin and histamine mediate gastroprotective effect of fluoxetine against experimentally-induced ulcers in rats

Research in the treatment of gastric ulcer has involved the investigation of new alternatives, such as anti-depressant drugs. The present study was designed to investigate the gastroprotective effects of fluoxetine against indomethacin and alcohol induced gastric ulcers in rats and the potential mechanisms of that effect. Fluoxetine (20?mg/kg) was administered IP for 14 days. For comparative purposes, other rats were treated with ranitidine (30?mg/kg). Thereafter, after 24?h of fasting, INDO (100?mg/kg) or absolute alcohol (5?ml/kg) was administered to all rats (saline was administered to naïve controls) and rats in each group were sacrificed 5?h (for INDO rats) or 1 h (for alcohol rats) later. Macroscopic examination revealed that both fluoxetine and ranitidine decreased ulcer scores in variable ratios, which was supported by microscopic histopathological examination. Biochemical analysis of fluoxetine- or ranitidine-pre-treated host tissues demonstrated reductions in tumor necrosis factor (TNF)-α and myeloperoxidase (MPO) levels and concomitant increases in gastric pH, nitric oxide (NO) and reduced glutathione (GSH) contents. Fluoxetine, more than ranitidine, also resulted in serotonin and histamine levels nearest to control values. Moreover, immuno-histochemical analysis showed that fluoxetine markedly enhanced expression of cyclo-oxygenases COX-1 and COX-2 in both models; in comparison, ranitidine did not affect COX-1 expression in either ulcer model but caused moderate increases in COX-2 expression in INDO-induced hosts and high expression in alcohol-induced hosts. The results here indicated fluoxetine exhibited better gastroprotective effects than ranitidine and this could be due to anti-secretory, anti-oxidant, anti-inflammatory and anti-histaminic effects of the drug, as well as a stabilization of gastric serotonin levels.     

Effect of etodolac,a new nonsteroidal anti-inflammatory drug,in MRL/lpr mice with articular lesions

Etodolac, a new nonsteroidal anti-inflammatory drug, was administered orally at doses of 1 and 5 mg/kg to MRL/MpJ-lpr/lpr (MRL/lpr) mice, and its effect on articular lesions was compared with that of indomethacin. Both etodolac and indomethacin significantly reduced swelling of the hind paw. Histopathological examination showed that etodolac significantly reduced cartilage and bone damage, whereas indomethacin treatment did not achieve a statistically significant effect. Rheumatoid factors were not affected by either etodolac or indomethacin. These results indicate that etodolac delays the development of arthritis in MRL/lpr mice, and reduces cartilage and bone damage.     

Acute Effects of the Anti-Inflammatory Cyclooxygenase-2 Selective Inhibitor, Flosulide, on Renal Plasma Flow and Glomerular Filtration Rate in Rats

Nephrotoxicity of nonsteroidal anti-inflammatory drugs is associated with other risk factors (volume-depletion) and may be secondary to functional changes mediated by the inhibition of renal cyclooxygenases. Acute anti-inflammatory doses of flosulide and indomethacin were determined on carrageenan paw edema and its effects on renal plasma flow (RPF) and glomerular filtration rate (GFR) were studied in normovolemic and hypovolemic rats. In normovolemic rats, flosulide increased RPF and GFR (25 mg/kg) and indomethacin (5–10 mg/kg) was without effect. Volume-depleted rats were obtained by oral furosemide (32 mg/kg), urinary eicosanoids were determined. After furosemide, plasma volume, RPF and GFR and PGE₂ decreased. Treatment of hypovolemic rats with flosulide (5–25 mg/kg) or indomethacin 10 mg/kg reduced RPF and GFR. Flosulide at 5 mg/kg reduced 6-keto-PGF₁ whereas at 25 mg/kg and after indomethacin at 10 mg/kg a fall in 6-keto-PGF₁ and TXB₂ appeared. Our data suggest that acute COX-2 selective inhibition may alter renal function.     

A study of the antiulcer mechanisms of propanolol in rats

Although propranolol has been shown to protect against enthanol and stress ulceration, the antiulcer mechanisms are still unclear. The present study examined the antiulcer mechanisms of propranolol in three different types of ulceration induced respectively by ethanol (60%), indomethacin (30 mg/kg) and stress (cold-restraint). Propranolol pretreatment in the highest dose (10 mg/kg) given either intraperitoneally (i.p.) or orally (p.o.) prevented gastric mucosal damage in these three ulcer models. The three doses of the drug (2.5, 5 or 10 mg/kg) dose-dependently decreased systemic blood pressure which was accompanied by a reduction of gastric mucosal blood flow. These findings suggest that the protection was unrelated to an improvement of local circulation in the stomach. However, propranolol preserved the mucus levels in the three types of ulcer models. The -adrenoceptor blocker also increased the basal gastric mucosal potential difference. These findings indicate that propranolol strengthens the mucosal barrier by the preservation of mucosal mucus and enhancement of the mucosal integrity in the stomach.accepted by R. O. Day     

Differential sensitivity of in vivo TNF and IL-6 production to modulation by anti-inflammatory drugs in mice.

The effect of dexamethasone and two non-steroidal anti-inflammatory agents ibuprofen and indomethacin on the production of serum interleukin 6(IL-6) and tumor necrosis factor (TNF) levels in mice treated with endotoxin (2.5 micrograms/mouse, i.p.) was investigated. Pretreatment of mice with dexamethasone (0.3-30.0 mg/kg, i.p., 30 min before endotoxin) completely blocked TNF production but did not affect that of IL-6. Conversely, pretreatment with indomethacin (5 mg/kg, i.p.) or ibuprofen (30 mg/kg, i.p.) potentiated the production of both IL-6 (+ 80% with INDO; + 100% with IBU) and TNF (+ 500% with INDO; + 50% with IBU). In the case of IL-6, the two anti-inflammatory drugs were able per se to induce significant levels of this cytokine even in the absence of LPS. These data indicate that IL-6 and TNF production are differently susceptible to glucocorticoids, and that prostaglandins can physiologically provide a negative feedback regulation of IL-6 and TNF synthesis.     

Effect of an endogenous satiety substance, 2-buten-4-olide, on gastric acid secretion and experimental ulceration in rats

The involvement of a feeding-related endogenous sugar acid, 2-buten-4-olide (2-B4O) on central regulation of gastric acid secretion, and its antiulcer effects on several gastric and duodenal experimental ulcer models were investigated in rats. Spontaneous gastric acid secretion was not affected by 2-B4O at doses below 10 mg/kg. The peripheral secretagogue-stimulated gastric secretions were significantly increased by pretreatment with 2-B4O. Gastric acid secretion induced by 2-deoxy-D-glucose (2-DG) was significantly suppressed by pretreatment with 2-B4O at doses between 0.1 and 100 mg/kg. Gastric and duodenal ulcerations induced by cold stress plus indomethacin, restraint and water immersion stress, pylorus ligation or cysteamine were also inhibited by pretreatment with 2-B4O. The results suggest that antiulcer effects of 2-B4O are due to suppression of gastric acid secretion via reduction of activity of the vagus nerve and gastric-related hypothalamic neurons. Thus, 2-B4O may be useful for treatment of gastroduodenal ulcer.     

Gabapentin,a Synthetic Analogue of Gamma Aminobutyric Acid,Reverses Systemic Acute Inflammation and Oxidative Stress in Mice

The aim of this study was to investigate the potential anti-inflammatory and anti-oxidant effects of gabapentin (GBP) in mice. The anti-inflammatory and anti-oxidant effects were evaluated using various mediators that induce paw edema, peritonitis model, myeloperoxidase (MPO) activity, proinflammatory cytokine levels, glutathione (GSH) consumption, and malondialdehyde (MDA) production in mice. Pretreatment of mice with GBP (1 mg/kg) significantly reduced carrageenan or dextran-induced paw edema (P?2. In the carrageenan-induced peritonitis model, GBP significantly decreased total and differential leukocyte counts and reduced the levels of MPO activity in the plantar tissue and IL-1β and TNF-α concentrations in the peritoneal exudate. The same dose of GBP also decreased the MDA concentration and increased the levels of GSH into the peritoneal fluid. In summary, our results demonstrated that GBP exhibited anti-inflammatory activity in mice by reducing the action of inflammatory mediators, neutrophil migration and proinflammatory cytokine levels, and anti-oxidant properties by decreasing the concentration of MDA and increasing the GSH content. These observations raise the possibility that GBP could be used to improve tissue resistance to damage during inflammatory conditions.     

Gastric damage induced by different doses of indomethacin in rats is variably affected by inhibiting iNOS or leukocyte infiltration

Aim: To evaluate the effect of inhibiting inducible nitric oxide synthase (iNOS), by aminoguanidine, or leukocyte infiltration, by fucoidin, on gastropathy induced by two different doses of indomethacin in rats. Methods: Rats were treated with saline, aminoguanidine (50 or 100 mg.kg^-1, i. p.) or fucoidin (25 mg.kg^-1, i. v.). Indomethacin was then given at a dose of 5 or 20 mg.kg^-1. At the end of 3 h, macroscopic gastric damage and myeloperoxidase (MPO) activity were assessed. Results: Aminoguanidine reduced the gastric damage induced by indomethacin at 20 mg.kg^-1, but increased gastric MPO activity. However, aminoguanidine did not influence the gastric damage induced by indomethacin at 5 mg.kg^-1. Fucoidin prevented both the gastric damage and the increase in gastric MPO activity induced by indomethacin at 20 mg. kg^-1, but not at 5 mg.kg^-1. Conclusion: Indomethacin at a dose of 20 mg.kg^-1, but not at 5 mg.kg^-1, induced gastropathy dependent on neutrophil infiltration and iNOS-generated NO. Received 17 February 2007; returned for revision 11 April 2007; returned for final revision 2 July 2007; accepted by M. Parnham 9 August 2007