Interactive roles of superoxide and inducible nitric oxide synthase in rat intestinal injury provoked by non-steroidal anti-inflammatory drugs

Potential therapeutic targets and molecular details of anthocyan-treated inflammatory bowel disease: a systematic bioinformatics analysis of network pharmacology

Anthocyans, containing anthocyanins and anthocyanidins, play a crucial role in preventing and treating inflammatory bowel disease (IBD). Most anthocyanins and their basic elements, namely anthocyanidins have been recognized for the effective treatment of IBD, but the key biomarkers of anthocyan-treated IBD remain unclear. In this study, a bioinformatics analysis based on network pharmacology was performed to demonstrate the core-targets, biological functions, and signaling pathways of most common anthocyanidins that existed in anthocyans to reveal their potential or major mechanisms. The network pharmacology of the multi-target drug molecular design with specific signal nodes was selected, which was used to analyse core targets and complete the bioinformatics analysis of core targets. The network assays indicated 44 common targeted genes, 5 of which were core targets of both six most common anthocyanidins and IBD. These 44 common targets related to major signaling mechanisms of the six most common anthocyanidins in IBD may involve following processes: promotion of intracellular metabolism and proliferation, inhibition of cell necrosis, anti-inflammation and regulation of intestinal epithelial survival mainly via pathways such as, the EGFR tyrosine kinase inhibitor resistance pathway, platelet activation, microRNAs in cancer, arachidonic acid metabolism and the cGMP-PKG signaling pathway. Thus, our findings may provide other molecular details about anthocyans in the treatment of IBD and contribute towards the use of anthocyanidins, which will be meaningful shedding light on the action mechanisms of anthocyanidins in treating IBD.

Celecoxib-induced gastrointestinal, liver and brain lesions in rats, counteraction by BPC 157 or L-arginine, aggravation by L-NAME

AIM

To counteract/reveal celecoxib-induced toxicity and NO system involvement.

METHODS

Celecoxib (1 g/kg b.w. ip) was combined with therapy with stable gastric pentadecapeptide BPC 157 (known to inhibit these lesions, 10 μg/kg, 10 ng/kg, or 1 ng/kg ip) and L-arginine (100 mg/kg ip), as well as NOS blockade [N(G)-nitro-L-arginine methyl ester (L-NAME)] (5 mg/kg ip) given alone and/or combined immediately after celecoxib. Gastrointestinal, liver, and brain lesions and liver enzyme serum values in rats were assessed at 24 h and 48 h thereafter.

RESULTS

This high-dose celecoxib administration, as a result of NO system dysfunction, led to gastric, liver, and brain lesions and increased liver enzyme serum values. The L-NAME-induced aggravation of the lesions was notable for gastric lesions, while in liver and brain lesions the beneficial effect of L-arginine was blunted. L-arginine counteracted gastric, liver and brain lesions. These findings support the NO system mechanism(s), both NO system agonization (L-arginine) and NO system antagonization (L-NAME), that on the whole are behind all of these COX phenomena. An even more complete antagonization was identified with BPC 157 (at both 24 h and 48 h). A beneficial effect was evident on all the increasingly negative effects of celecoxib and L-NAME application and in all the BPC 157 groups (L-arginine + BPC 157; L-NAME + BPC 157; L-NAME + L-arginine + BPC 157). Thus, these findings demonstrated that BPC 157 may equally counteract both COX-2 inhibition (counteracting the noxious effects of celecoxib on all lesions) and additional NOS blockade (equally counteracting the noxious effects of celecoxib + L-NAME).

CONCLUSION

BPC 157 and L-arginine alleviate gastrointestinal, liver and brain lesions, redressing NSAIDs' post-surgery application and NO system involvement.

Indomethacin injury to the rat small intestine is dependent upon biliary secretion and is associated with overgrowth of enterococci

NSAIDuse is limited due to the drugs' toxicity to the gastrointestinal mucosa, an action incompletely understood. Lower gut injury induced byNSAIDs is dependent on bile secretion and is reported to increase the growth of a number of bacterial species, including an enterococcal species,Enterococcus faecalis This study examined the relationships between indomethacin (INDO)-induced intestinal injury/bleeding, small bowel overgrowth (SBO) and dissemination of enterococci, and the contribution of bile secretion to these pathological responses. Rats received either a sham operation (SO) or bile duct ligation (BDL) prior to administration of two daily subcutaneous doses of saline orINDO, and 24 h later, biopsies of ileum and liver were collected for plating on selective bacterial media. Fecal hemoglobin (Hb) and blood hematocrit (Hct) were measured to assess intestinal bleeding. Of the four treatment groups, onlySO/INDOrats experienced a significant 10- to 30-fold increase in fecal Hb and reduction in Hct, indicating thatBDLattenuatedINDO-induced intestinal injury/bleeding. Ileal enterococcal colony-forming units were significantly increased (500- to 1000-fold) inSO/INDOrats. Of all groups, only theSO/INDOrats demonstrated gut injury, and this was associated with enterococcal overgrowth of the gut and dissemination to the liver. We also demonstrated thatINDO-induced intestinal injury andE. faecalisovergrowth was independent of the route of administration of the drug, as similar findings were observed in rats orally dosed with theNSAID Bile secretion plays an important role inINDO-induced gut injury and appears to support enterococcal overgrowth of the intestine.NSAID-induced enterococcalSBOmay be involved either as a compensatory response to gut injury or with the pathogenic process itself and the subsequent development of sepsis.

Geranylgeranylacetone, a gastromucoprotective drug, protects against NSAID-induced esophageal, gastroduodenal and small intestinal mucosal injury in healthy subjects: A prospective randomized study involving a comparison with famotidine

OBJECTIVE

A treatment strategy to inhibit nonsteroidal anti-inflammatory drug (NSAID)-induced small intestinal lesions has not yet been established. To clarify whether monotherapy with a gastromucoprotective drug, geranylgeranylacetone (GGA), inhibits NSAID-induced acute mucosal injury of the upper digestive tract and small intestine.

METHODS

A prospective, randomized, comparative study. All procedures were performed at Osaka Medical College. The subjects, thirty healthy adult volunteers, were randomly divided into two groups. In the NSAID-GGA group, 75 mg/day of diclofenac sodium and 150 mg/day of GGA were orally administered for two weeks. In the NSAID-FAM group, 75 mg/day of diclofenac sodium and 20 mg/day of famotidine (FAM) were orally administered for two weeks. esophagogastroduodenoscopy (EGD) and video capsule endoscopy (VCE) were performed before and two weeks after drug administration. In addition, we measured fecal occult blood reactions and the fecal calprotectin levels.

RESULTS

No significant differences were observed between the groups in the mean increase in esophageal/gastroduodenal lesions. The mean increases in the scores in the NSAID-FAM group (NSAID-GGA group) of small bowel lesions were as follows: erythema: 1.93 ± 0.67 (0.30 ± 0.60), erosions: 1.13 ± 0.54 (0.38 ± 0.35), ulcers: 0.73 ± 0.33 (0.07 ± 0.07) and edema: 0.53 ± 0.44 (0.07 ± 0.07). The scores for erythema and ulcers were significantly lower in the NSAID-GGA group than in the NSAID-FAM group (p=0.032 and 0.0165, respectively).

CONCLUSION

We compared the prophylactic effects of a mucoprotective drug, GGA, and an H2RA, famotidine, on mucosal injury involving the esophagus to the small intestine related to the two-week oral administration of diclofenac sodium in healthy volunteers. In the upper digestive tract, the prophylactic effects were similar between the two drugs. However, in the small intestine, GGA more markedly inhibited the development of lesions compared to famotidine.

The mechanism of the down-regulation of hepatic transporters in rats with indomethacin-induced intestinal injury

BACKGROUND

Previously, we reported that hepatic transporters were down-regulated consistent with intestinal injury in indomethacin (IDM)-treated rats.

AIM

The purpose of this study was to characterize this mechanism of the down-regulation of hepatic transporters in IDM-treated rats.

METHODS

Hepatic nuclear receptor expressions, oxidative stress condition and the expression of hepatic transporters were evaluated in rats with IDM-induced intestinal injury with or without the administration of mucosal protectant ornoprostil, a prostaglandin E1 analogue, or aminoguanidine (AG), an iNOS inhibitor.

RESULTS

All the nuclear receptors examined in the present study, which regulates hepatic transporters, were decreased by the administration of IDM. Hepatic glutathione, an indicator of oxidative stress, was significantly reduced compared with control. We then determined the expression of hepatic transporters by semi-quantitative real-time RT-PCR and Western blot analysis in IDM-treated rats with or without the administration of ornoprostil or AG. Ornoprostil recovered the gene expression of Oatp1a1, Oatp1b2 and Mrp2 and protein expression of Mrp2 while it had no effect on Oatp1a1 and Oatp1b2 proteins. These results indicated that the gene expression of hepatic transporters was down-regulated in association with the intestinal injury. On the other hand, there is no effect of AG on the reduced gene expression of hepatic Oatp1a1, Oatp1b2 and Mrp2. In protein expression, AG slightly recovered Mrp2 expression accompanied by a partial decrease in portal NO levels.

CONCLUSIONS

We suggest that the transcriptional process influenced by a dysfunction of hepatic nuclear receptors as well as the effect of NO on the post-transcriptional process due to intestinal injury are partially involved in the down-regulation of hepatic transporters.

Pentadecapeptide BPC 157 and its effects on a NSAID toxicity model: diclofenac-induced gastrointestinal, liver, and encephalopathy lesions

AIMS

We attempted to fully antagonize the extensive toxicity caused by NSAIDs (using diclofenac as a prototype).

MAIN METHODS

Herein, we used the stable gastric pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, MW 1419), an anti-ulcer peptide shown to be efficient in inflammatory bowel disease clinical trials (PL 14736) and various wound treatments with no toxicity reported. This peptide was given to antagonize combined gastrointestinal, liver, and brain toxicity induced by diclofenac (12.5mg/kg intraperitoneally, once daily for 3 days) in rats.

KEY FINDINGS

Already considered a drug that can reverse the toxic side effects of NSAIDs, BPC 157 (10 μg/kg, 10 ng/kg) was strongly effective throughout the entire experiment when given (i) intraperitoneally immediately after diclofenac or (ii) per-orally in drinking water (0.16 μg/mL, 0.16 ng/mL). Without BPC 157 treatment, at 3h following the last diclofenac challenge, we encountered a complex deleterious circuit of diclofenac toxicity characterized by severe gastric, intestinal and liver lesions, increased bilirubin, aspartate transaminase (AST), alanine transaminase (ALT) serum values, increased liver weight, prolonged sedation/unconsciousness (after any diclofenac challenge) and finally hepatic encephalopathy (brain edema particularly located in the cerebral cortex and cerebellum, more in white than in gray matter, damaged red neurons, particularly in the cerebral cortex and cerebellar nuclei, Purkinje cells and less commonly in the hippocampal neurons).

SIGNIFICANCE

The very extensive antagonization of diclofenac toxicity achieved with BPC 157 (μg-/ng-regimen, intraperitoneally, per-orally) may encourage its further use as a therapy to counteract diclofenac- and other NSAID-induced toxicity.

Distribution of small intestinal mucosal injuries as a result of NSAID administration

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce small intestinal mucosal injuries. The concentrations of NSAIDs, bile acids and intestinal flora may differ in the proximal and distal parts of the small intestine. This study aimed to analyse types and distributions of NSAID-induced small intestinal injuries.

SUBJECTS AND METHODS

In total 55 healthy male volunteers were examined using baseline capsule endoscopy (CE). Subjects then undertook a 14-day regimen of NSAID medication (diclofenac sodium, 75 mg day(-1)) with proton-pump inhibitors (omeprazole 20 mg day(-1)) as gastroprotection. After 14 days, subjects underwent post-treatment CE and were assessed for three types of small intestinal injuries: denuded areas, erosions and ulcers. The proximal and distal parts of the small intestine were arbitrarily classified according to CE transit time from the duodenal bulb.

RESULTS

Baseline CE revealed six mucosal lesions in 6 of 55 subjects (11%), consisting of three denuded areas and three erosions. Post-treatment CE identified 636 lesions in 32 of 53 subjects (60%); including 115 denuded areas in 16 subjects, 498 erosions in 22 subjects and 23 ulcers in 8 subjects. The distribution of small intestinal injuries differed according to type; denuded areas (90%: 103/115) were predominantly located in the proximal part, erosions throughout the small intestine and all ulcers in the distal part. The location of ulcers and denuded areas differed statistically (P < 0.0001).

CONCLUSIONS

The impact of short-term NSAID medication on the small intestine differed according to intestinal site, with most denuded areas identified in the proximal part and all ulcers in the distal part.

Protocols to assess the gastrointestinal side effects resulting from inhibition of cyclo-oxygenase isoforms

A prevalent unwanted action of cyclo-oxygenase (COX) inhibitors, as exemplified by the non-steroidal anti-inflammatory drugs (NSAIDs), is their potential to produce gastrointestinal side effects in clinical use. The injury provoked by such agents includes rapid superficial disruption to the surface layer of the gastric mucosa, the production of acute gastric erosions in the corpus region and the formation of ulcers in the antral region of the stomach. The small intestine is also adversely affected, with a developing enteropathy over a more protracted period that causes lesions and inflammation in the gut. From experimental work, the interactive mechanisms of such damage in the stomach differ distinctly from those that underlie the intestinal injury, yet the damage in both regions involves the inhibition of both COX-1 and COX-2 isoforms. This chapter outlines the in vivo methods that can be used to identify the potential for novel NSAIDs and selective COX-inhibitors to produce acute gastric corpus lesions and more-chronic antral ulcers in the rat, as well as causing small intestinal enteropathy. Such methods can also be utilized to evaluate the ability of novel agents to prevent the gastrointestinal injury provoked by NSAIDs or COX-inhibitors.

Role of coxibs in the strategies for gastrointestinal protection in patients requiring chronic non-steroidal anti-inflammatory therapy

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed drugs due to their high efficacy in the treatment of pain, fever, inflammation and rheumatic disorders. However, their use is associated with the occurrence of adverse effects at the level of digestive tract, ranging from dyspeptic symptoms, gastrointestinal erosions and peptic ulcers to more serious complications, such as overt bleeding or perforation. To overcome problems related to NSAID-induced digestive toxicity, different therapeutic strategies can presently be considered, including the co-administration of drugs endowed with protective activity on the upper gastrointestinal tract, such as the proton pump inhibitors, or the prescription of coxibs, which have been clinically developed as anti-inflammatory/analgesic drugs characterized by reduced damaging activity on gastrointestinal mucosa. The availability of different treatment options, to reduce the risk of NSAID-induced adverse digestive effects, has fostered intensive preclinical and clinical research aimed at addressing a number of unresolved issues and to establish rational criteria for an appropriate use of coxibs in the medical practice. Particular attention is being paid to the management of patients with high degrees of digestive risk, resulting by concomitant treatment with low-dose aspirin for anti-thrombotic prophylaxis or ongoing symptomatic gastroduodenal ulcers. The present review discusses the most relevant lines of evidence concerning the position of coxibs in the therapeutic strategies for gastrointestinal protection in patients who require NSAID therapy and hold different levels of risk of developing adverse effects at the level of digestive tract.

Anti-inflammatory effects of flavonoids: genistein, kaempferol, quercetin, and daidzein inhibit STAT-1 and NF-kappaB activations, whereas flavone, isorhamnetin, naringenin, and pelargonidin inhibit only NF-kappaB activation along with their inhibitory effect on iNOS expression and NO production in activated macrophages

In inflammation, bacterial products and proinflammatory cytokines induce the formation of large amounts of nitric oxide (NO) by inducible nitric oxide synthase (iNOS), and compounds that inhibit NO production have anti-inflammatory effects. In the present study, we systematically investigated the effects of 36 naturally occurring flavonoids and related compounds on NO production in macrophages exposed to an inflammatory stimulus (lipopolysaccharide, LPS), and evaluated the mechanisms of action of the effective compounds. Flavone, the isoflavones daidzein and genistein, the flavonols isorhamnetin, kaempferol and quercetin, the flavanone naringenin, and the anthocyanin pelargonidin inhibited iNOS protein and mRNA expression and also NO production in a dose-dependent manner. All eight active compounds inhibited the activation of nuclear factor-κB (NF-κB), which is a significant transcription factor for iNOS. Genistein, kaempferol, quercetin, and daidzein also inhibited the activation of the signal transducer and activator of transcription 1 (STAT-1), another important transcription factor for iNOS. The present study characterises the effects and mechanisms of naturally occurring phenolic compounds on iNOS expression and NO production in activated macrophages. The results partially explain the pharmacological efficacy of flavonoids as anti-inflammatory compounds.

Endotoxemia-mediated induction of cardiac inducible nitric-oxide synthase expression accounts for the hypotensive effect of ethanol in female rats

We have recently shown that intragastric (i.g.) ethanol lowers blood pressure (BP) in conscious female rats via a reduction in cardiac output (CO). However, the mechanisms implicated in these hemodynamic effects of ethanol are not known. Therefore, we tested the hypothesis that ethanol-evoked endotoxemia mediates the reduction in CO via enhanced myocardial inducible nitric-oxide synthase (iNOS) expression. Immunoblot (myocardial iNOS), biochemical (plasma endotoxin and nitrite/nitrate), and integrative [BP, heart rate, CO, stroke volume (SV), and total peripheral resistance (TPR)] studies were conducted in conscious female rats that received i.g. ethanol (1 g/kg) in the absence or presence of 1400W (N-(3-[aminomethyl]benzyl) acetamidine) or ampicillin to selectively inhibit iNOS and to eliminate endogenous endotoxin, respectively. Ethanol-evoked hypotension coincided with reductions in CO and SV and increases in: 1) TPR, 2) plasma endotoxin and nitrite/nitrate, and 3) myocardial iNOS expression. These effects of ethanol were virtually abolished in rats pretreated with ampicillin (200 mg/kg/day for 2 days by gavage) or with 1400W (5 mg/kg i.p.) except for the increase in plasma endotoxin, which persisted in 1400W-pretreated rats. These findings yield insight into the mechanistic role of endotoxin-myocardial iNOS signaling in the cardiodepressant action of ethanol, which accounts for its hypotensive effect in conscious female rats.

Multiple Indomethacin-Induced Jejunal Ulcerations with Perforation: A Case Report with Histology

Gastric and duodenal inflammation and ulceration are well-known complications of nonsteroidal anti-inflammatory (NSAID) usage. However, small bowel ulceration and perforation secondary to NSAID use is uncommon and has rarely been reported in the literature. We describe a perforated jejunal ulcer that developed in a patient using indomethacin for treatment of ankylosing spondylitis. We performed a literature review of NSAID-induced small bowel injury and compared the histology of NSAID-related injury with more familiar causes of small bowel perforation.

Down-Regulation of Hepatic Transporters for BSP in Rats with Indomethacin-Induced Intestinal Injury

Previous reports have demonstrated that an intestinal injury causes hypofunctions of the liver associated with down-regulations of cytochrome P450, but an influence on hepatic transporters remains unclear. Here, we tested hepatic transporter functions in a rat model of bowel injury using indomethacin (IDM). After administration of IDM (8.5 mg/kg, i.p., 3 d), the rats suffered the intestinal impairment indicated by a reduction of alkaline phosphatase activity in mucosa. In vivo pharmacokinetic experiments of bromosulfophthalein (BSP) showed that there was a reduction in its plasma elimination rate and cumulative biliary excretion in IDM-treated rats and systemic and biliary clearances reduced to nearly 50% of the control group. Protein expressions in plasma membrane and mRNA levels of organic anion transporting polypeptide 1b2 (Oatp1b2) and multidrug resistance-associated protein 2 (Mrp2), which play hepatic BSP uptake and biliary excretion, respectively, in the liver were significantly reduced following the IDM treatment. In portal plasma, the levels of proinflammatory cytokines were unchanged, while the level of nitric oxide metabolites (NO2- + NO3-) increased to 6.5-fold that of the control. The time-course on IDM treatment indicated that, firstly, intestinal injury was induced, the NO level increased, and the hepatic Oatp1b2 and Mrp2 expression began to fall followed by an increase in plasma ALT. In conclusion, IDM-induced injury to the small intestine causes the hypofunction of hepatic Oatp1b2 and Mrp2 independently on the hepatic impairment, and NO arising from bowel injury may be one of key factors for it through the remote effect.

Superoxide, peroxynitrite and oxidative/nitrative stress in inflammation

A considerable body of evidence suggests that formation of potent reactive oxygen species and resulting oxidative/nitrative stress play a major role in acute and chronic inflammation and pain. Much of the knowledge in this field has been gathered by the use of pharmacological and genetic approaches. In this mini review, we will evaluate recent advances made towards understanding the roles of reactive oxygen species in inflammation, focusing in particular on superoxide and peroxynitrite. Given the limited space to cover this broad topic, here we will refer the reader to comprehensive review articles whenever possible.

Factors involved in upregulation of inducible nitric oxide synthase in rat small intestine following administration of nonsteroidal anti-inflammatory drugs

We investigated the functional mechanisms underlying the expression of inducible nitric oxide (NO) synthase (iNOS) in the rat small intestine following the administration of nonsteroidal anti-inflammatory drugs (NSAIDs) and found a correlation with the intestinal ulcerogenic properties of NSAIDs. Conventional NSAIDs (indomethacin, diclofenac, naproxen, and flurbiprofen), a selective cyclooxygenase (COX)-1 inhibitor (SC-560) and a selective COX-2 inhibitor (rofecoxib) were administered p.o., and the intestinal mucosa was examined 24 hours later. Indomethacin decreased prostaglandin E2 (PGE2) production in the intestinal mucosa and caused intestinal hypermotility and bacterial invasion as well as the upregulation of iNOS expression and NO production, resulting in hemorrhagic lesions. Other NSAIDs similarly inhibited PGE2 production and caused hemorrhagic lesions with intestinal hypermotility as well as iNOS expression. Hypermotility in response to indomethacin was prevented by both PGE2 and atropine but not ampicillin, yet all these agents inhibited not only bacterial invasion but also expression of iNOS as well, resulting in prevention of intestinal lesions. SC-560, but not rofecoxib, caused a decrease in PGE2 production, intestinal hypermotility, bacterial invasion, and iNOS expression, yet this agent neither increased iNOS activity nor provoked intestinal damage because of the recovery of PGE2 production owing to COX-2 expression. Food deprivation totally attenuated both iNOS expression and lesion formation in response to indomethacin. In conclusion, the expression of iNOS in the small intestine following administration of NSAIDs results from COX-1 inhibition and is functionally associated with intestinal hypermotility and bacterial invasion. This process plays a major pathogenic role in the intestinal ulcerogenic response to NSAIDs.

[NSAID-colonopathy]

The pain-relief properties of NSAID/ASA preparations have been known for a long time. In particular, the gastrointestinal tract shows side effects such as: erosion, ulceration, and even perforation. In the upper gastrointestinal tract, our group has shown that a correct histological diagnosis of NSAID/ASA induced lesions can be made in a high percentage of cases on the basis of recognition of ischemic necrosis. NSAID/ASA induced lesions are less commonly found in the lower gastrointestinal tract. We could also demonstrate a correct histological diagnosis of NSAID-colonopathy on the basis of finding ischemic necrosis. Besides the known complications, another typical complication is diaphragm-like stenosis, which must not be mistaken for tumor stenosis. The differential diagnosis of NSAID-colonopathy includes ischemic colitis, which cannot be distinguished histologically if the exact endoscopic description is not available. Sometimes NSAID/ASA induced lesions are misdiagnosed as Crohn's disease due to the focal character of the lesions. Since all of our analyses are retrospective, the criteria developed by our group should be checked prospectively.

Strictures, diaphragms, erosions or ulcerations of ischemic type in the colon should always prompt consideration of nonsteroidal anti-inflammatory drug-induced lesions

AIM: To investigate whether NSAIDs/ASA lesions in the colon can histologically be diagnosed on the basis of ischemic necrosis similar to biopsy-based diagnosis of NSAIDs/ASA-induced erosions and ulcers of the stomach.

METHODS: In the period between 1997 and 2002, we investigated biopsy materials obtained from 611 patients (415 women, 196 men, average age 60.5 years) with endoscopic focal erosions, ulcerations, strictures or diaphr-agms in the colon. In the biopsies obtained from these lesions, we always established the suspected diagnosis of NSAID-induced lesions whenever necroses of the ischemic type were found. Together with the histological report, we enclosed a questionnaire to investigate the use of medication. The data provided by the questionnaire were then correlated with the endoscopic findings, the location, number and nature of the lesions, and the histological findings.

RESULTS: At the time of their colonoscopy, 86.1% of the patients had indeed been taking NSAID/ASA medication for years (43.9%) or months (29.5%). The most common indication for the use of these drugs was pain (64.3%), and the most common indication for colonoscopy was bleeding (55.5%). Endoscopic inspection revealed multiple erosions and/or ulcers in 60.6%, strictures in 15.8%, and diaphragms in 3.0% of the patients. The lesions were located mainly in the right colon including the transverse colon (79.9%). A separate analysis of age and sex distribution, endoscopic and histological findings for NSAIDs alone, ASA alone, combined NSAID/ASA, and for patients denying the use of such drugs, revealed no significant differences among the groups.

CONCLUSION: This uncontrolled retrospective study based on the histological finding of an ischemic necrosis shows that the histologically suspected diagnosis of NSAID-induced lesions in the colon is often correct. The true diagnostic validity of this finding and the differentiation from ischemic colitis should, however, be investigated in a prospective controlled study.

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.

Toxic effects of nonsteroidal antiinflammatory drugs on the small bowel, colon, and rectum

The gastrointestinal toxicity of conventional nonsteroidal antiinflammatory drugs (NSAIDs) is not confined to the stomach and proximal duodenum but extends also to the rest of the small bowel, colon, and rectum. Long-term NSAID therapy usually induces clinically silent enteropathy characterized by increased intestinal permeability and inflammation. Chronic occult bleeding and protein loss may result in iron-deficiency anemia and hypoalbuminemia. NSAIDs can also induce small bowel ulcers that infrequently lead to acute bleeding, perforation, or chronic scarring responsible for diaphragm-like strictures. At the colon and rectum, NSAID use can result in de novo lesions such as nonspecific colitis and rectitis, ulcers, and diaphragm-like strictures. NSAIDs have been implicated in the development of segmental ischemic colitis. In patients with diverticular disease, NSAID use increases the risk of severe diverticular infection and perforation. NSAIDs can trigger exacerbations of ulcerative colitis or Crohn's disease. With selective COX-2 inhibitors, the risk of gastrointestinal toxicity is reduced as compared to conventional NSAIDs but is not completely eliminated. Experimental studies suggest that long-term COX-2 inhibitor therapy may cause damage to the previously healthy small bowel. Similar to conventional NSAIDs, COX-2 inhibitors may be capable of triggering exacerbations of inflammatory bowel disease.

Nitric oxide and the gut injury induced by non-steroidal anti-inflammatory drugs

Nitric oxide (NO) can protect the gastrointestinal tract from injury, including that provoked by non-steroidal anti-inflammatory drugs (NSAIDs). This protective profile of NO, which predominantly reflects actions on the microcirculation, is mimicked by NO donors. Moreover, the NO-donating agents know as the NO-NSAIDs or CINODs (cyclo-oxygenase-inhibiting nitric oxide-donating drugs) exhibit reduced gut injury in experimental models, which is considered to reflect these local beneficial actions of NO. NSAIDs cause chronic inflammatory lesions in the small intestine in experimental models. This injury results from initial COX inhibition and other local events, with translocation of indigenous luminal bacteria, leading to induction of NO synthase isoform, iNOS, and subsequent production of the cytotoxic moiety, peroxynitrite from NO and superoxide. Agents that inhibit iNOS or superoxide production can attenuate such intestinal injury. In the absence of reactive oxygen moieties, NO may play a beneficial role in the resolution of inflammatory damage to the gut, thus reconciling the potential opposing properties of NO in tissue inflammation and injury.

Mechanisms underlying intestinal injury induced by anti-inflammatory COX inhibitors

By far the most attention has been paid to the deleterious actions of nonsteroidal anti-inflammatory drugs (NSAIDs), including isoform selective agents that inhibit cyclooxygenase (COX), on the upper gastrointestinal tract, particularly the gastric and duodenal mucosa. However, recent studies confirm a relatively high incidence of serious clinical events, especially with the more-established drugs of this class, involving the small intestine. Pathogenic factors that have been proposed from early studies in such enteropathy have included the enterohepatic circulation of the nonsteroidal anti-inflammatory drugs, inhibition of cyclooxygenase, surface epithelial changes and focal microvascular events. More recent work has concerned the role of infiltrating inflammatory cells, the relative roles of cyclooxygenase isoforms, COX-1 and COX-2 and the key involvement of inducible nitric oxide (NO) synthase and its product in combination with superoxide, peroxynitrite. In the present review, evidence for the underlying involvement of each these processes, and their sequential integration in the development of the intestinal injury and ulceration promoted by nonsteroidal anti-inflammatory drugs has been considered.

Biology and chemistry of the inhibition of nitric oxide synthases by pteridine-derivatives as therapeutic agents

Inhibitors of the family of nitric oxide synthases (NOS-I-III; EC 1.14.13.39) are of interest as pharmacological agents to modulate pathologically high nitric oxide (NO) levels in inflammation, sepsis, and stroke. In this article, we discuss the approach for targeting the unique (6R)-5,6,7,8-tetrahydro-L-biopterin (H4Bip) binding site of NOS by appropriate inhibitors. This binding site maximally increases enzyme activity and NO production from the substrate L-arginine upon cofactor binding. The first generation of H4Bip-based NOS inhibitors was based on 4-amino H4Bip derivatives in analogy to anti-folates such as methotrexate. In addition, we discuss the structure-activity relationship of a related series of 4-oxo-pteridine derivatives. Furthermore, molecular modeling studies provide an understanding of pterin antagonism on a structural level based on favorable and unfavorable interactions between protein binding site and ligands. These techniques include 3D-QSAR (CoMFA, CoMSIA) to understand ligand affinity and GRID/consensus principal component analysis (CPCA) to learn about selectivity requirements. Collectively these approaches, in combination with the presented SAR and structural data, provide useful information for the design of novel NOS inhibitors with increased isoform selectivity.

Nitric oxide synthase inhibition: therapeutic potential in asthma

Nitric oxide (NO) is synthesized from L-arginine in the human respiratory tract by enzymes of the NO synthase (NOS) family. Levels of NO in exhaled air are increased in asthma, and measurement of exhaled NO has been advocated as a noninvasive tool to monitor the underlying inflammatory process. However, the relation of NO to disease pathophysiology is uncertain, and in particular the fundamental question of whether it should be viewed primarily as beneficial or harmful remains unanswered. Exogenously administered NO has both bronchodilator and bronchoprotective properties. Although it is unlikely that NO is an important regulator of basal airway tone, there is good evidence that endogenous NO release exerts a protective effect against various bronchoconstrictor stimuli. This response is thought to involve one or both of the constitutive NOS isoforms, endothelial NOS (eNOS) and neuronal NOS (nNOS). Therefore, inhibition of these enzymes is unlikely to be therapeutically useful in asthma and indeed may worsen disease control. On the other hand, the high concentrations of NO in asthma, which are believed to reflect upregulation of inducible NOS (iNOS) by proinflammatory cytokines, may produce various deleterious effects. These include increased vascular permeability, damage to the airway epithelium, and promotion of inflammatory cell infiltration. However, the possible effects of iNOS inhibition on allergic inflammation in asthma have not yet been described and studies in animal models have yielded inconsistent findings. Thus, the evidence to suggest that inhibition of iNOS would be a useful therapeutic strategy in asthma is limited at present. More definitive information will require studies combining agents that potently and specifically target individual NOS isoforms with direct measurement of inflammatory markers.

On the selectivity of superoxide dismutase mimetics and its importance in pharmacological studies

The list of pathophysiological conditions associated with the overproduction of superoxide expands every day. Much of the knowledge compiled on the role of this radical in disease has been gathered using the native superoxide dismutase enzyme and, more recently, by the use of superoxide dismutase knockout models or transgenic models that overexpress the various isoforms of the enzyme. Although the native enzyme has shown promising anti-inflammatory properties in both preclinical and clinical studies, there were drawbacks and issues associated with its use as a therapeutic agent and pharmacological tool. Based on the concept that removal of superoxide modulates the course of inflammation, synthetic, low-molecular-weight mimetics of the superoxide dismutase enzymes that could overcome some of the limitations associated with the use of the native enzyme have been designed. In this review, we will discuss the advances made using various superoxide dismutase mimetics that led to the proposal that superoxide (and/or the product of its interaction with nitric oxide, peroxynitrite) is an important mediator of inflammation, and to the conclusion that superoxide dismutase mimetics can be utilized as therapeutic agents in diseases of various etiologies. The importance of the selectivity of such compounds in pharmacological studies will be discussed.

Therapy for chronic obstructive pulmonary disease in the 21st century

Chronic obstructive pulmonary disease (COPD) is a common, smoking-related, severe respiratory condition characterised by progressive, irreversible airflow limitation. Current treatment of COPD is symptomatic, with no drugs capable of halting the relentless progression of airflow obstruction. Better understanding of the airway inflammation, oxidative stress and alveolar destruction that characterise COPD has delineated new disease targets, with consequent identification of novel compounds with therapeutic potential. These new drugs include aids to smoking cessation (e.g. bupropion) and improvements to existing therapies, for example long-acting rather than short-acting bronchodilators, as well as combination therapy. New antiproteases include acyl-enzyme and transition state inhibitors of neutrophil elastase (e.g. sivelestat and ONO-6818), matrix metalloprotease inhibitors (e.g. batimastat), cathepsin inhibitors and peptide protease inhibitors (e.g. DX-890 [EPI-HNE-4] and trappin-2). New antioxidants include superoxide dismutase mimetics (e.g. AEOL-10113) and spin trap compounds (e.g. N-tert-butyl-alpha-phenylnitrone). New anti-inflammatory interventions include phosphodiesterase-4 inhibitors (e.g. cilomilast), inhibitors of tumour necrosis factor-alpha (e.g. humanised monoclonal antibodies), adenosine A(2a) receptor agonists (e.g. CGS-21680), adhesion molecule inhibitors (e.g. bimosiamose [TBC1269]), inhibitors of nuclear factor-kappaB (e.g. the naturally occurring compounds hypoestoxide and (-)-epigallocatechin-3-gallate) and activators of histone deacetylase (e.g. theophylline). There are also selective inhibitors of specific extracellular mediators such as chemokines (e.g. CXCR2 and CCR2 antagonists) and leukotriene B(4) (e.g. SB201146), and of intracellular signal transduction molecules such as p38 mitogen activated protein kinase (e.g. RWJ67657) and phosphoinositide 3-kinase. Retinoids may be one of the few potential treatments capable of reversing alveolar destruction in COPD, and a number of compounds are in clinical trial (e.g. all-trans-retinoic acid). Talniflumate (MSI-1995), an inhibitor of human calcium-activated chloride channels, has been developed to treat mucous hypersecretion. In addition, the purinoceptor P2Y(2) receptor agonist diquafosol (INS365) is undergoing clinical trials to increase mucus clearance. The challenge to transferral of these new compounds from preclinical research to disease management is the design of effective clinical trials. The current scarcity of well characterised surrogate markers predicts that long-term studies in large numbers of patients will be needed to monitor changes in disease progression.

Effects of aminoguanidine and cyclooxygenase inhibitors on nitric oxide and prostaglandin production, and nitric oxide synthase and cyclooxygenase expression induced by lipopolysaccharide in the estrogenized rat uterus

BACKGROUND/OBJECTIVE

The aim of our study was first to investigate if there exists an interaction between nitric oxide (NO) and prostaglandin (PG) generation in the estrogenized rat uterus challenged by lipopolysaccharide (LPS), and, secondly, which isoforms of nitric oxide synthase (NOS) and cyclooxygenase (COX) participate in this process.

METHODS

To study the effect of LPS and to characterize the isoenzymes involved in the process, specific inhibitors of iNOS (aminoguanidine) and COX-II (meloxicam, nimesulide) and non-specific of COX (indomethacin) were injected intraperitoneally to determine their effect on NO and PG production, and on NOS and COX expression induced by LPS in estrogenized rat uterus. NO production was measured by arginine-citrulline conversion assay and PGE(2)/PGF(2alpha,)by radioconversion. Enzyme expression was evaluated by Western blot analysis.

RESULTS

The present work shows that iNOS inhibitor, aminoguanidine, reduced NO and PGE(2)/PGF(2alpha) production induced by LPS injection. Aminoguanidine exerts its effect over the PG metabolism by inhibiting COX-II activity and expression. On the other hand, both indomethacin, a non-selective PG inhibitor, and meloxicam, a COX-II inhibitor, stimulated NO production and reduced PGE(2)/PGF(2alpha) generation. Indomethacin also reduced COX-II and iNOS expression.

CONCLUSION

These results indicate that in the estrogenized rat uterus challenged with LPS, PG and NO interact affecting each other's metabolic pathways. The above findings indicate that the interaction between NOS and COX might be important in the regulation of physiopathologic events during pregnancy.

Gastrointestinal effects of nonsteroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) causes extensive damage to the gastrointestinal (GI) tract. The underlying mechanisms of gastric injury include topical irritant actions that disrupt the epithelial barrier, as well as the inhibition of cyclo-oxygenase (COX), which is predominantly the COX-1 isoform in the mucosa. This damage can be attenuated by antisecretory agents or by mucosal protective agents such as the synthetic prostanoids or nitric oxide (NO) donors. Compounds designed to attenuate topical irritancy, or have protective agents incorporated, such as NO-containing NSAIDs, the CINODs (cyclo-oxygenase-inhibiting NO-donating drugs) show reduced mucosal injury. NSAIDs also cause injury in the small intestine, which appears to result from initial COX inhibition, with subsequent translocation of indigenous bacteria, induction of NO synthase and production of the cytotoxic moiety, peroxynitrite. The COX-2 selective agents, the coxibs, which inhibit prostanoid biosynthesis at inflammatory sites, but not the endogenous protective prostanoids in the gut formed by COX-1, have proved so far to be a successful therapeutic approach to reducing NSAIDs GI damage. The clinical outcome of the use of the second generation of coxibs, and the newer NO NSAIDs is now awaited.

Inhibition of NO production by highly-oxygenated diterpenes of Orthosiphon stamineus and their structure-activity relationship

Nitric oxide (NO) has been implemented in various pathological processes. In the present study, 47 highly-oxygenated isopimarane-type and novel carbon framework staminane-type diterpenes isolated from Orthosiphon stamineus of Indonesia, Okinawa, Myanmar and Vietnam were evaluated for their inhibitory activity in NO production by lipopolysaccharide (LPS)-activated macrophage-like J774.1 cells. All the isolated diterpenes showed concentration-dependent inhibition of NO production in LPS-activated macrophage-like J774.1 cells, and based on the results, their structure-activity relationship were established.

Role of bacteria and inducible nitric oxide synthase activity in the systemic inflammatory microvascular response provoked by indomethacin in the rat

The role of bacteria and nitric oxide (NO), formed by the inducible isoform of NO synthase (iNOS), in a widespread systemic inflammatory microvascular response that follows indomethacin administration, has been investigated in the rat. Subcutaneous administration of indomethacin (10 mg kg(-1)) daily for 2 days produced an increase in microvascular leakage of radiolabelled albumin accompanied by expression of iNOS activity in the lung, liver, spleen and kidney, as well as in the jejunum, caecum, colon and ileum. Pretreatment with dexamethasone (1 mg kg(-1) day(-1), s.c.) reduced indomethacin-provoked microvascular leakage and the expression of iNOS activity in all the tissues studied. The widespread microvascular leakage and iNOS activity was also inhibited by pretreatment with ampicillin (200 mg kg(-1) day(-1), p.o.), metronidazole (200 mg kg(-1) day(-1), p.o.) or by polymyxin B (15 mg kg(-1) day(-1), s.c.). Administration of the highly selective iNOS inhibitor GW 273629 (3-[[2-(ethanimidoylamino)ethyl]sulphonyl]-L-alanine; five doses of 5 mg kg(-1), s.c. over 48 h) substantially inhibited the microvascular leakage in the affected organs. Such findings suggest the involvement of indigenous gut bacteria, lipopolysaccharide and iNOS expression following indomethacin-induced enteropathy in this widespread systemic inflammatory microvascular response.

Blocking NO synthesis: how, where and why?

Nitric oxide (NO) is a key physiological mediator, and the association of disordered NO generation with many pathological conditions has led to much interest in pharmacologically modulating NO levels. However, the wide range of processes in which NO has been implicated, and the fact that increases or decreases in NO levels might be therapeutically desirable depending on the condition or even at different stages of the same condition, pose considerable challenges for drug development. Here, we focus on the rationale and potential for approaches that reduce NO synthesis, which have led to the development of several compounds that will shortly be entering clinical trials.

SOD mimetics are coming of age

The list of pathophysiological conditions that are associated with the overproduction of superoxide anions expands every day. The most exciting realization is that there seems to be a similarity between the tissue injury that is observed in various disease states, as superoxide anions produce tissue injury and associated inflammation in all tissues in similar ways. Tissue injury and inflammation form the basis of many disease pathologies, including ischaemia and reperfusion injuries, radiation injury, hyperoxic lung damage and atherosclerosis. This commonality provides a unique opportunity to manipulate numerous disease states with an agent that removes superoxide anions.