Physiological healing of chronic gastric ulcer is not impaired by the hydrogen sulphide (H2S)-releasing derivative of acetylsalicylic acid (ATB-340): functional and proteomic approaches.

Gastric ulcers affect approx. 10% of population. Non-steroidal anti-inflammatory drugs (NSAIDs), including acetylsalicylic acid (ASA) predispose to or impair the physiologically complex healing of pre-existing ulcers. Since H2S is an endogenous cytoprotective molecule, we hypothesized that new H2S-releasing ASA-derivative (ATB-340) could overcome pathological impact of NSAIDs on GI regeneration.Clinically translational gastric ulcers were induced in Wistar rats using state-of-the-art microsurgical model employing serosal application of acetic acid. This was followed by 9 days long i.g. daily treatment with vehicle, ATB-340 (6-24 mg/kg) or equimolar ASA doses (4-14 mg/kg). Ulcer area was assessed macro- and microscopically. Prostaglandin (PG)E2  levels, indicating pharmacological activity of NSAIDs and 8-hydroxyguanozine content, reflecting nucleic acids oxidation in serum/gastric mucosa, were determined by ELISA. Qualitative and/or quantitative pathway-specific alterations at the ulcer margin were evaluated using real-time PCR and mass spectrometry-based proteomics.ASA, unlike ATB-340, dose-dependently delayed/impaired gastric tissue recovery, deregulating 310 proteins at the ulcer margin, including Ras signalling, wound healing or apoptosis regulators. ATB-340 maintained NSAIDs-specific cyclooxygenase-inhibiting capacity on systemic and GI level but in time-dependent manner. High dose of ATB-340 (24 mg/kg daily), but not ASA, decreased nucleic acids oxidation and upregulated anti-oxidative/anti-inflammatory heme oxygenase-1, 24-dehydrocholesterol reductase or suppressor of cytokine signalling (SOCS3) at the ulcer margin.Thus, ASA impairs the physiological healing of pre-existing gastric ulcers, inducing the extensive molecularly functional and proteomic alterations at the wound margin. H2S-releasing ATB-340 maintains the target activity of NSAIDs with limited impact on gastric PGE2 signalling and physiological GI regeneration, enhancing anti-inflammatory and anti-oxidative response, and providing the pharmacological advantage.

Hydrogen Sulfide-Releasing Indomethacin-Derivative (ATB-344) Prevents the Development of Oxidative Gastric Mucosal Injuries.

Hydrogen sulfide (H2S) emerged recently as an anti-oxidative signaling molecule that contributes to gastrointestinal (GI) mucosal defense and repair. Indomethacin belongs to the class of non-steroidal anti-inflammatory drugs (NSAIDs) and is used as an effective intervention in the treatment of gout- or osteoarthritis-related inflammation. However, its clinical use is strongly limited since indomethacin inhibits gastric mucosal prostaglandin (PG) biosynthesis, predisposing to or even inducing ulcerogenesis. The H2S moiety was shown to decrease the GI toxicity of some NSAIDs. However, the GI safety and anti-oxidative effect of a novel H2S-releasing indomethacin derivative (ATB-344) remain unexplored. Thus, we aimed here to compare the impact of ATB-344 and classic indomethacin on gastric mucosal integrity and their ability to counteract the development of oxidative gastric mucosal injuries. Wistar rats were pretreated intragastrically (i.g.) with vehicle, ATB-344 (7-28 mg/kg i.g.), or indomethacin (5-20 mg/kg i.g.). Next, animals were exposed to microsurgical gastric ischemia-reperfusion (I/R). Gastric damage was assessed micro- and macroscopically. The volatile H2S level was assessed in the gastric mucosa using the modified methylene blue method. Serum and gastric mucosal PGE2 and 8-hydroxyguanozine (8-OHG) concentrations were evaluated by ELISA. Molecular alterations for gastric mucosal barrier-specific targets such as cyclooxygenase-1 (COX)-1, COX-2, heme oxygenase-1 (HMOX)-1, HMOX-2, superoxide dismutase-1 (SOD)-1, SOD-2, hypoxia inducible factor (HIF)-1α, xanthine oxidase (XDH), suppressor of cytokine signaling 3 (SOCS3), CCAAT enhancer binding protein (C/EBP), annexin A1 (ANXA1), interleukin 1 beta (IL-1ß), interleukin 1 receptor type I (IL-1R1), interleukin 1 receptor type II (IL-1R2), inducible nitric oxide synthase (iNOS), tumor necrosis factor receptor 2 (TNFR2), or H2S-producing enzymes, cystathionine γ-lyase (CTH), cystathionine ß-synthase (CBS), or 3-mercaptopyruvate sulfur transferase (MPST), were assessed at the mRNA level by real-time PCR. ATB-344 (7 mg/kg i.g.) reduced the area of gastric I/R injuries in contrast to an equimolar dose of indomethacin. ATB-344 increased gastric H2S production, did not affect gastric mucosal PGE2 content, prevented RNA oxidation, and maintained or enhanced the expression of oxidation-sensitive HMOX-1 and SOD-2 in line with decreased IL-1ß and XDH. We conclude that due to the H2S-releasing ability, i.g., treatment with ATB-344 not only exerts dose-dependent GI safety but even enhances gastric mucosal barrier capacity to counteract acute oxidative injury development when applied at a low dose of 7 mg/kg, in contrast to classic indomethacin. ATB-344 (7 mg/kg) inhibited COX activity on a systemic level but did not affect cytoprotective PGE2 content in the gastric mucosa and, as a result, evoked gastroprotection against oxidative damage.

Microbiome Profile and Molecular Pathways Alterations in Gastrointestinal Tract by Hydrogen Sulfide-Releasing Nonsteroidal Anti-Inflammatory Drug (ATB-352): Insight into Possible Safer Polypharmacy.

Aims: Nonsteroidal anti-inflammatory drugs, including ketoprofen, induce adverse effects within the gastrointestinal (GI)-tract. Hydrogen sulfide (H2S) is an antioxidative gaseous mediator contributing to GI-protection. We aimed to evaluate the GI safety of a novel H2S-releasing derivative of ketoprofen (ATB-352) versus classic ketoprofen and the molecular mechanisms of their activity after chronic treatment in experimental animal models. Results: Ketoprofen (10 mg/kg/day) administered intragastrically for 7 days in contrast with ATB-352 (14 mg/kg/day) reduced mucosal H2S content inducing GI damage with significantly increased injury score, altered intestinal microbiome profile, and modulation of more than 50% of 36 investigated molecular sensors (e.g., mammalian target of rapamycin or suppressor of cytokine signaling 3 [SOCS3]). Polypharmacy with aspirin (10 mg/kg/day) enhanced ketoprofen toxicity not affecting GI safety of ATB-352. Omeprazole (20 mg/kg/day) decreased ketoprofen-induced injury to the level of ATB-352 alone. Both compounds combined or not with aspirin or omeprazole maintained the ability to inhibit cyclooxygenase (COX) activity manifested by decreased prostaglandin production. Innovation and Conclusions: Ketoprofen-induced H2S-production decrease and intestinal microbiome profile alterations lead to GI toxicity observed on macro-/microscopic and molecular levels. Ketoprofen but not ATB-352 requires concomitant treatment with omeprazole to eliminate GI adverse effects. ATB-352 applied alone or in a polypharmacy setting with aspirin effectively inhibited COX and maintained GI safety due to H2S-release. Neither compound affected DNA oxidation in the GI mucosa, but ATB-352 had lower impact on molecular oxidative/inflammatory response pathways and intestinal microbiome. The GI safety of ATB-352 could be due to the involvement of heme oxygenase 1 and SOCS3 pathway activation. Antioxid. Redox Signal. 36, 189-210.

Effects of Hydrogen Sulfide on the Microbiome: From Toxicity to Therapy.

Significance: Hydrogen sulfide (H2S), an important regulator of physiology and health, helps resolve inflammation and promotes tissue repair in the gastrointestinal tract. Recent Advances: Gut microbiota live as a multispecies biofilm in close interaction with the upper mucus layer lining the epithelium. The relative abundance, spatial organization, and function of these microorganisms affect a broad range of health outcomes. This article provides a state-of-the-art review of our understanding of the cross talk between H2S, the gut microbiota, and health. H2S can have toxic or therapeutic effects, depending on its concentration and source. When produced at excessive concentrations by local microbiota, H2S may cause mucus disruption and inflammation and contribute to development of cancer. In contrast, low levels of endogenous or exogenous H2S directly stabilize mucus layers, prevent fragmentation and adherence of the microbiota biofilm to the epithelium, inhibit the release of invasive pathobionts, and help resolve inflammation and tissue injury. Although scarce, research findings suggest that dietary H2S obtained from plants or ingestion of the H2S precursor, L-cysteine, may also modulate the abundance and function of microbiota. Critical Issues: A critical issue is the lack of understanding of the metagenomic, transcriptomic, and proteomic alterations that characterize the interactions between H2S and gut microbiota to shape health outcomes. Future Directions: The ambivalent roles of H2S in the gut offer a fertile ground for research on such critical issues. The findings will improve our understanding of how H2S modulates the microbiota to affect body function and will help identify novel therapeutic strategies. Antioxid. Redox Signal. 36, 211-219.

Potent anti-inflammatory effects of an H2 S-releasing naproxen (ATB-346) in a human model of inflammation.

ATB-346 is a hydrogen sulfide-releasing non-steroidal anti-inflammatory drug (H2 S-NSAID) derived from naproxen, which in preclinical studies has been shown to have markedly reduced gastrointestinal adverse effects. However, its anti-inflammatory properties in humans compared to naproxen are yet to be confirmed. To test this, we used a dermal model of acute inflammation in healthy, human volunteers, triggered by ultraviolet-killed Escherichia coli. This robust model allows quantification of the cardinal signs of inflammation along with cellular and humoral factors accumulating within the inflamed skin. ATB-346 was non-inferior to naproxen in terms of its inhibition of cyclooxygenase activity as well as pain and tenderness. ATB-346 significantly inhibited neutrophil infiltration at the site of inflammation at 4 h, compared to untreated controls. Subjects treated with ATB-346 also experienced significantly reduced pain and tenderness compared to healthy controls. Furthermore, both classical and intermediate monocyte subsets infiltrating the site of inflammation at 48 h expressed significantly lower levels of CD14 compared to untreated controls, demonstrating a shift toward an anti-inflammatory phenotype. Collectively, we have shown for the first time in humans that ATB-346 is potently anti-inflammatory and propose that ATB-346 represents the next generation of H2 S-NSAIDs, as a viable alternative to conventional NSAIDs, with reduced adverse effects profile.

Gaseous Mediators as a Key Molecular Targets for the Development of Gastrointestinal-Safe Anti-Inflammatory Pharmacology.

Non-steroidal anti-inflammatory drugs (NSAIDs) represent one of the most widely used classes of drugs and play a pivotal role in the therapy of numerous inflammatory diseases. However, the adverse effects of these drugs, especially when applied chronically, frequently affect gastrointestinal (GI) tract, resulting in ulceration and bleeding, which constitutes a significant limitation in clinical practice. On the other hand, it has been recently discovered that gaseous mediators nitric oxide (NO), hydrogen sulfide (H2S) and carbon monoxide (CO) contribute to many physiological processes in the GI tract, including the maintenance of GI mucosal barrier integrity. Therefore, based on the possible therapeutic properties of NO, H2S and CO, a novel NSAIDs with ability to release one or more of those gaseous messengers have been synthesized. Until now, both preclinical and clinical studies have shown promising effects with respect to the anti-inflammatory potency as well as GI-safety of these novel NSAIDs. This review provides an overview of the gaseous mediators-based NSAIDs along with their mechanisms of action, with special emphasis on possible implications for GI mucosal defense mechanisms.

Comment on "Evidence that the ProPerDP method is inadequate for protein persulfidation detection due to lack of specificity".

The recent report by Fan et al alleged that the ProPerDP method is inadequate for the detection of protein persulfidation. Upon careful evaluation of their work, we conclude that the claim made by Fan et al is not supported by their data, rather founded in methodological shortcomings. It is understood that the ProPerDP method generates a mixture of cysteine-containing and non-cysteine-containing peptides. Instead, Fan et al suggested that the detection of non-cysteine-containing peptides indicates nonspecific alkylation at noncysteine residues. However, if true, then such peptides would not be released by reduction and therefore not appear as products in the reported workflow. Moreover, the authors' biological assessment of ProPerDP using Escherichia coli mutants was based on assumptions that have not been confirmed by other methods. We conclude that Fan et al did not rigorously assess the method and that ProPerDP remains a reliable approach for analyses of protein per/polysulfidation.

Gastrointestinal biofilms in health and disease.

Microorganisms colonize various ecological niches in the human habitat, as they do in nature. Predominant forms of multicellular communities called biofilms colonize human tissue surfaces. The gastrointestinal tract is home to a profusion of microorganisms with intertwined, but not identical, lifestyles: as isolated planktonic cells, as biofilms and in biofilm-dispersed form. It is therefore of major importance in understanding homeostatic and altered host-microorganism interactions to consider not only the planktonic lifestyle, but also biofilms and biofilm-dispersed forms. In this Review, we discuss the natural organization of microorganisms at gastrointestinal surfaces, stratification of microbiota taxonomy, biogeographical localization and trans-kingdom interactions occurring within the biofilm habitat. We also discuss existing models used to study biofilms. We assess the contribution of the host-mucosa biofilm relationship to gut homeostasis and to diseases. In addition, we describe how host factors can shape the organization, structure and composition of mucosal biofilms, and how biofilms themselves are implicated in a variety of homeostatic and pathological processes in the gut. Future studies characterizing biofilm nature, physical properties, composition and intrinsic communication could shed new light on gut physiology and lead to potential novel therapeutic options for gastrointestinal diseases.

Increased Mucosal Thrombin is Associated with Crohn's Disease and Causes Inflammatory Damage through Protease-activated Receptors Activation.

BACKGROUND AND AIMS: Thrombin levels in the colon of Crohn's disease patients have recently been found to be elevated 100-fold compared with healthy controls. Our aim was to determine whether and how dysregulated thrombin activity could contribute to local tissue malfunctions associated with Crohn's disease. METHODS: Thrombin activity was studied in tissues from Crohn's disease patients and healthy controls. Intracolonic administration of thrombin to wild-type or protease-activated receptor-deficient mice was used to assess the effects and mechanisms of local thrombin upregulation. Colitis was induced in rats and mice by the intracolonic administration of trinitrobenzene sulphonic acid. RESULTS: Active forms of thrombin were increased in Crohn's disease patient tissues. Elevated thrombin expression and activity were associated with intestinal epithelial cells. Increased thrombin activity and expression were also a feature of experimental colitis in rats. Colonic exposure to doses of active thrombin comparable to what is found in inflammatory bowel disease tissues caused mucosal damage and tissue dysfunctions in mice, through a mechanism involving both protease-activated receptors -1 and -4. Intracolonic administration of the thrombin inhibitor dabigatran, as well as inhibition of protease-activated receptor-1, prevented trinitrobenzene sulphonic acid-induced colitis in rodent models. CONCLUSIONS: Our data demonstrated that increased local thrombin activity, as it occurs in the colon of patients with inflammatory bowel disease, causes mucosal damage and inflammation. Colonic thrombin and protease-activated receptor-1 appear as possible mechanisms involved in mucosal damage and loss of function and therefore represent potential therapeutic targets for treating inflammatory bowel disease.

Giardia spp. promote the production of antimicrobial peptides and attenuate disease severity induced by attaching and effacing enteropathogens via the induction of the NLRP3 inflammasome.

Polymicrobial infections of the gastro-intestinal tract are common in areas with poor sanitation. Disease outcome is the result of complex interactions between the host and pathogens. Such interactions lie at the core of future management strategies of enteric diseases. In developed countries of the world, Giardia duodenalis is a common cause of diarrheal disease. In contrast, giardiasis appears to protect children against diarrhea in countries with poor sanitation, via obscure mechanisms. We hypothesized that Giardia may protect its host from disease induced by a co-infecting pathogen such as attaching and effacing Escherichia coli. This enteropathogen is commonly implicated in pediatric diarrhea in developing countries. The findings indicate that co-infection with Giardia attenuates the severity of disease induced by Citrobacter rodentium, an equivalent of A/E E. coli in mice. Co-infection with Giardia reduced colitis, blood in stools, fecal softening, bacterial invasion, and weight loss; the protective effects were lost when co-infection occurred in Nod-like receptor pyrin-containing 3 knockout mice. In co-infected mice, elevated levels of antimicrobial peptides Murine ß defensin 3 and Trefoil Factor 3, and enhanced bacterial killing, were NLRP3-dependent. Inhibition of the NLRP3 inflammasome in human enterocytes blocked the activation of AMPs and bacterial killing. The findings uncover novel NLRP3-dependent modulatory mechanisms during co-infections with Giardia spp. and A/E enteropathogens, and demonstrate how these interactions may regulate the severity of enteric disease.

Enhanced Analgesic Effects and Gastrointestinal Safety of a Novel, Hydrogen Sulfide-Releasing Anti-Inflammatory Drug (ATB-352): A Role for Endogenous Cannabinoids.

Aims: The covalent linking of nonsteroidal anti-inflammatory drugs to a hydrogen sulfide (H2S)-releasing moiety has been shown to dramatically reduce gastrointestinal (GI) damage and bleeding, as well as increase anti-inflammatory and analgesic potency. We have tested the hypothesis that an H2S-releasing derivative of ketoprofen (ATB-352) would exhibit enhanced efficacy without significant GI damage in a mouse model of allodynia/hyperalgesia. Results: ATB-352 was significantly more potent and effective as an analgesic than ketoprofen and did not elicit GI damage. Pretreatment with an antagonist of the CB1 cannabinoid receptor (AM251) significantly reduced the analgesic effects of ATB-352. The CB1 antagonist exacerbated GI damage when coadministered with ketoprofen, but GI damage was not induced by the combination of ATB-352 and the CB1 antagonist. In vitro, ATB-352 was substantially more potent than ketoprofen as an inhibitor of fatty acid amide hydrolase, consistent with a contribution of endogenous cannabinoids to the analgesic effects of this drug. Blood anandamide levels were significantly depressed by ketoprofen, but remained unchanged after treatment with ATB-352. Innovation: Ketoprofen is a potent analgesic, but its clinical use, even in the short term, is significantly limited by its propensity to cause significant ulceration and bleeding in the GI tract. Covalently linking an H2S-releasing moiety to ketoprofen profoundly reduces the GI toxicity of the drug, while boosting analgesic effectiveness. Conclusion: This study demonstrates a marked enhancement of the potency and effectiveness of ATB-352, an H2S-releasing derivative of ketoprofen, in part, through the involvement of the endogenous cannabinoid system. This may have significant advantages for the control and management of pain, such as in a postoperative setting.

A proof-of-concept, Phase 2 clinical trial of the gastrointestinal safety of a hydrogen sulfide-releasing anti-inflammatory drug.

BACKGROUND AND PURPOSE: ATB-346 is a hydrogen sulfide (H2 S)-releasing anti-inflammatory and analgesic drug. Animal studies demonstrated negligible gastrointestinal (GI) damage despite marked inhibition of COX activity and significant analgesic and anti-inflammatory effects. In humans, ATB-346 (250 mg once daily) was found to inhibit COX to the same extent as naproxen (550 mg twice daily). EXPERIMENTAL APPROACH: Two hundred forty-four healthy volunteers completed a 2-week, double-blind study, taking either ATB-346 (250 mg once daily) or naproxen (550 mg twice daily), with upper GI ulceration being examined endoscopically. KEY RESULTS: Forty-two per cent of the subjects taking naproxen developed at least one ulcer (≥3-mm diameter), while only 3% of the subjects taking ATB-346 developed at least one ulcer. The two drugs produced comparable and substantial (>94%) suppression of COX activity. Subjects in the naproxen group developed more ulcers per subject than ATB-346-treated subjects and a greater incidence of larger ulcers (≥5-mm diameter). The incidence of dyspepsia, abdominal pain, gastro-oesophageal reflux, and nausea was lower with ATB-346 than with naproxen. Subjects treated with ATB-346 had significantly higher plasma levels of H2 S than those treated with naproxen. CONCLUSIONS AND IMPLICATIONS: This Phase 2B study provides unequivocal evidence for a marked reduction of GI toxicity of the H2 S-releasing analgesic/anti-inflammatory drug, ATB-346, as compared to the conventional dose of naproxen that produced equivalent suppression of COX. LINKED ARTICLES: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

From primordial gas to the medicine cabinet.

LINKED ARTICLES: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

Efficacy of a Peruvian Botanical Remedy (Sabell A4+) for Treating Liver Disease and Protecting Gastric Mucosal Integrity.

The purpose of this study was to determine the efficacy of a Peruvian botanical formulation for treating disorders of hepatic function and gastric mucosal integrity. The formulation A4+ (Sabell Corporation) contains extracts of Curcuma longa rhizome, Cordia lutea flower, and Annona muricata leaf. Individually these plants have been used as traditional remedies for liver disease. We report the efficacy of A4+ and its components using a variety of in vitro and in vivo disease models. The methods used included tests for antioxidant, anti-inflammatory, and antiviral activity as well as mouse models of liver disease, including Concanavalin A-induced immune-mediated hepatitis and a bile duct ligation model for evaluating sickness behaviour associated with liver disease. Rat models were used to evaluate the gastric mucosal protective property of A4+ following indomethacin challenge and to evaluate its anti-inflammatory action in an "air pouch" model. In all tests, A4+ proved to be more effective than placebo. A4+ was antioxidant and anti-inflammatory and diminished Hepatitis C virus replication in vitro. In animal models, A4+ was shown to protect the liver from immune-mediated hepatitis, improve behavioural function in animals with late stage liver disease, and protect the rat gastric mucosa from ulceration following NSAID exposure. We conclude that A4+ ameliorated many aspects of liver injury, inhibited hepatitis C virus replication, and protected the gastric mucosa from NSAIDs. These varied beneficial properties appear to result from positive interactions between the three constituent herbs.

Active thrombin produced by the intestinal epithelium controls mucosal biofilms.

Proteolytic homeostasis is important at mucosal surfaces, but its actors and their precise role in physiology are poorly understood. Here we report that healthy human and mouse colon epithelia are a major source of active thrombin. We show that mucosal thrombin is directly regulated by the presence of commensal microbiota. Specific inhibition of luminal thrombin activity causes macroscopic and microscopic damage as well as transcriptomic alterations of genes involved in host-microbiota interactions. Further, luminal thrombin inhibition impairs the spatial segregation of microbiota biofilms, allowing bacteria to invade the mucus layer and to translocate across the epithelium. Thrombin cleaves the biofilm matrix of reconstituted mucosa-associated human microbiota. Our results indicate that thrombin constrains biofilms at the intestinal mucosa. Further work is needed to test whether thrombin plays similar roles in other mucosal surfaces, given that lung, bladder and skin epithelia also express thrombin.

Effect of Ketoprofen and ATB-352 on the Immature Human Intestine: Identification of Responders and Non-responders.

BACKGROUND AND OBJECTIVE: The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a broad spectrum of life-threatening adverse effects on the immature gastrointestinal tract. NSAID derivatives exploiting the beneficial effects of biologically active gases, such as hydrogen sulfide (H2S), have been developed. Herein, we determined the effects of ketoprofen and ATB-352, a H2S-releasing ketoprofen derivative, on selected metabolic pathways previously identified to be significantly altered by indomethacin in the human immature intestine. METHODS: Ketoprofen and ATB-352 were tested on human mid-gestation small intestinal explants maintained in a serum-free organ culture system for 48 hours. The expression levels of the representative genes involved in selected metabolic pathways were measured by real-time PCR after a treatment of 48 hours. RESULTS: Tested at a concentration that allows more than 80% inhibition of PGE2 production, ketoprofen was found to be less damaging than indomethacin at an equivalent dosage. However, based on the inducibility of cyclooxygenase-2 transcript expression, we were able to discriminate between responder individuals in which the deleterious effects observed with indomethacin were attenuated, and non-responder specimens in which the effects were similar to those observed with indomethacin. ATB-352 did not induce significant changes compared to ketoprofen on these metabolic pathways. CONCLUSIONS: These results show less damaging effects of ketoprofen compared to indomethacin on the immature intestine and indicate that the intestinal response to this NSAID significantly varies between individuals. However, the results did not allow us to demonstrate a specific beneficial effect of H2S release in organ culture.

Eicosanoids in the gastrointestinal tract.

Eicosanoids play important roles in modulating inflammation throughout the body. The gastrointestinal (GI) tract, in part because of its intimate relationship with the gut microbiota, is in a constant state of low-grade inflammation. Eicosanoids like PGs, lipoxins and leukotrienes play essential roles in maintenance of mucosal integrity. On the other hand, in some circumstances, these mediators can become major drivers of inflammatory processes when the lining of the GI tract is breached. Drugs such as nonsteroidal anti-inflammatories, by altering the production of various eicosanoids, can dramatically impact the ability of the GI tract to respond appropriately to injury. Disorders such as inflammatory bowel disease appear to be driven in part by altered production of eicosanoids. Several classes of drugs have been developed that target eicosanoids. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Nitric oxide in the gastrointestinal tract: opportunities for drug development.

Nitric oxide (NO) plays important roles in gastrointestinal mucosal defence, as well as in the pathogenesis of several gastrointestinal diseases (e.g. irritable bowel syndrome and inflammatory bowel disease). The potent cytoprotective effects of NO have been demonstrated in a range of animal models. However, in some disease states, inhibition of NO synthesis is beneficial. Several attempts have been made to develop drugs for ulcerative and/or inflammatory disorders of the gastrointestinal tract, with varying degrees of success. Covalently linking a NO-releasing group to non-steroidal anti-inflammatory drugs or to drugs used in the treatment of inflammatory bowel disease and irritable bowel syndrome has shown some benefit, although no drug of this type has yet been fully developed. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Iron Sequestration in Microbiota Biofilms As A Novel Strategy for Treating Inflammatory Bowel Disease.

Significant alterations of intestinal microbiota and anemia are hallmarks of inflammatory bowel disease (IBD). It is widely accepted that iron is a key nutrient for pathogenic bacteria, but little is known about its impact on microbiota associated with IBD. We used a model device to grow human mucosa-associated microbiota in its physiological anaerobic biofilm phenotype. Compared to microbiota from healthy donors, microbiota from IBD patients generate biofilms ex vivo that were larger in size and cell numbers, contained higher intracellular iron concentrations, and exhibited heightened virulence in a model of human intestinal epithelia in vitro and in the nematode Caenorhabditis elegans. We also describe an unexpected iron-scavenging property for an experimental hydrogen sulfide-releasing derivative of mesalamine. The findings demonstrate that this new drug reduces the virulence of IBD microbiota biofilms through a direct reduction of microbial iron intake and without affecting bacteria survival or species composition within the microbiota. Metabolomic analyses indicate that this drug reduces the intake of purine nucleosides (guanosine), increases the secretion of metabolite markers of purine catabolism (urate and hypoxanthine), and reduces the secretion of uracil (a pyrimidine nucleobase) in complex multispecies human biofilms. These findings demonstrate a new pathogenic mechanism for dysbiotic microbiota in IBD and characterize a novel mode of action for a class of mesalamine derivatives. Together, these observations pave the way towards a new therapeutic strategy for treatment of patients with IBD.