NSAID-induced Small Intestinal Damage Research Articles

Neutrophil extracellular trap formation and its implications in nonsteroidal anti-inflammatory drug-induced small intestinal injury.

Nonsteroidal anti-inflammatory drugs (NSAIDs) damage the small intestine via neutrophil infiltration driven by the mucosal invasion of enterobacteria. The antimicrobial function of neutrophils is partially dependent on neutrophil extracellular traps (NETs). Excessive NET formation has been associated with several inflammatory diseases. Here, we aimed to investigate the role of NETs in NSAID-induced small intestinal damage using human samples and an experimental mouse model. Human small intestine specimens were obtained from NSAID users during double-balloon enteroscopy. Wild-type, protein arginine deiminase 4 (PAD4) knockout, and antibiotic-treated mice were administered indomethacin to induce small intestinal injury. The expression of NET-associated proteins, including PAD4, citrullinated histone H3 (CitH3), cell-free DNA, and myeloperoxidase (MPO), was evaluated. The double-positive stained area with CitH3 and MPO, which is specific for neutrophil-derived extracellular traps, was significantly high in the injured small intestinal mucosa of NSAID users. In a mouse model, small intestinal damage developed at 6h after indomethacin administration, accompanied by increased mRNA levels of interleukin-1β and keratinocyte chemoattractant and elevated NET-associated protein levels of PAD4, CitH3, and MPO in small intestine and serum levels of cell-free DNA. Both genetic deletion and pharmacological inhibition of PAD4 attenuated this damage by reducing the mRNA expression of inflammatory cytokines and NET-associated proteins. Furthermore, mice pretreated with antibiotics showed resistance to indomethacin-induced small intestinal damage, with less NET formation. These results suggest that NETs aggravate NSAID-induced small intestinal injury. Therefore, NET inhibition could be a potential treatment for NSAID-induced small intestinal injury.

Protective role of resolvin D1, a pro-resolving lipid mediator, in nonsteroidal anti-inflammatory drug-induced small intestinal damage.

Resolvin D1, a specialized pro-resolving lipid mediator produced from docosahexaenoic acid by 15- and 5-lipoxygenase, exerts anti-inflammatory effects driving to the resolution of inflammation. The present study aimed to elucidate its role in small intestinal damage induced by nonsteroidal anti-inflammatory drug (NSAID). Indomethacin was administered orally to C57BL/6J male mice, which were sacrificed 24 h later to collect small intestine specimens. Before administration of indomethacin, mice were subjected to intraperitoneal treatment with resolvin D1 or oral administration of baicalein, a 15-lipoxygenase inhibitor. Small intestinal damage induced by indomethacin was attenuated by pretreatment with resolvin D1. Furthermore, resolvin D1 reduced the gene expression levels of interleukin-1β, tumor necrosis factor-α, and CXCL1/keratinocyte chemoattractant. Conversely, the inhibition of 15-lipoxygenase activity by baicalein increased the expression of genes coding for these inflammatory cytokines and chemokine, leading to exacerbated small intestinal damage, and reduced the concentration of resolvin D1 in the small intestinal tissue. Exogenous treatment with resolvin D1 negated the deleterious effect of baicalein. 15-lipoxygenase was mainly expressed in the epithelium and inflammatory cells of the small intestine, and its gene and protein expression was not affected by the administration of indomethacin. Inhibition of the resolvin D1 receptor, lipoxin A4 receptor /formyl peptide receptor 2, by its specific inhibitors Boc-1 and WRW4 aggravated indomethacin-induced small intestinal damage. Collectively, these results indicate that resolvin D1 produced by 15-lipoxygenase contributes to mucoprotection against NSAID-induced small intestinal damage through its anti-inflammatory effect.

Rebamipide ameliorates indomethacin-induced small intestinal damage and proton pump inhibitor-induced exacerbation of this damage by modulation of small intestinal microbiota.

Non-steroidal anti-inflammatory drugs (NSAIDs) induce small intestinal damage. It has been reported that rebamipide, a mucoprotective drug, exerts a protective effect against NSAID-induced small intestinal damage; however, the underlying mechanism remains unknown. In this study, we investigated the significance of the small intestinal microbiota in the protective effect of rebamipide against indomethacin-induced small intestinal damage in mice. A comprehensive analysis of the 16S rRNA gene sequencing revealed an alteration in the composition of the small intestinal microbiota at the species level, modulated by the administration of rebamipide and omeprazole. The transplantation of the small intestinal microbiota of the mice treated with rebamipide suppressed the indomethacin-induced small intestinal damage. Omeprazole, a proton pump inhibitor, exacerbated the indomethacin-induced small intestinal damage, which was accompanied by the alteration of the small intestinal microbiota. We found that the transplantation of the small intestinal microbiota of the rebamipide-treated mice ameliorated indomethacin-induced small intestinal damage and the omeprazole-induced exacerbation of the damage. These results suggest that rebamipide exerts a protective effect against NSAID-induced small intestinal damage via the modulation of the small intestinal microbiota, and that its ameliorating effect extends also to the exacerbation of NSAID-induced small intestinal damage by proton pump inhibitors.

High-fat diet-mediated dysbiosis exacerbates NSAID-induced small intestinal damage through the induction of interleukin-17A

Non-steroidal anti-inflammatory drugs (NSAIDs) cause damage in the small intestine in a bacteria-dependent manner. As high-fat diet (HFD) is a potent inducer of gut dysbiosis, we investigated the effects of HFD on bacterial flora in the small intestine and NSAID-induced enteropathy. 16S rRNA gene analysis revealed that the population of Bifidobacterium spp. significantly decreased by fold change of individual operational taxonomic units in the small intestine of mice fed HFD for 8 weeks. HFD increased intestinal permeability, as indicated by fluorescein isothiocyanate-dextran absorption and serum lipopolysaccharide levels, accompanied by a decrease in the protein expressions of ZO-1 and occludin and elevated mRNA expression of interleukin (IL)-17A in the small intestine. HFD-fed mice exhibited increased susceptibility to indomethacin-induced damage in the small intestine; this phenotype was observed in normal diet-fed mice that received small intestinal microbiota from HFD-fed mice. Administration of neutralizing antibodies against IL-17A to HFD-fed mice reduced intestinal permeability and prevented exacerbation of indomethacin-induced damage. Thus, HFD-induced microbial dysbiosis in small intestine caused microinflammation through the induction of IL-17A and increase in intestinal permeability, resulting in the aggravation of NSAID-induced small intestinal damage.

Involvement of gliadin, a component of wheat gluten, in increased intestinal permeability leading to non-steroidal anti-inflammatory drug-induced small-intestinal damage.

Gliadin, a component of wheat gluten known to be an important factor in the etiology of celiac disease, is related to several other diseases through its enhancing effect on intestinal paracellular permeability. We investigated the significance of gliadin in non-steroidal anti-inflammatory drug (NSAID)-induced small-intestinal damage in mice. 7-week-old C57BL/6 male mice were divided into the following groups: standard diet group, in which mice were fed with wheat-containing standard rodent diet (CE-2); gluten-free diet group, in which mice were fed with gluten-free diet (AIN-76A); and gliadin-administered group, in which mice fed with gluten-free diet were administered with gliadin (~250 mg/kg BW). Each group was subdivided into negative, healthy control group and NSAID-treated group. To some mice fed with gluten-free diet and administered with gliadin, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor was administered for clarification of the significance of EGFR in NSAID-induced small intestinal damage and intestinal permeability. In mice fed with a gluten-free diet, indomethacin or diclofenac induced very mild mucosal damage in the small intestine compared with that in mice fed with a wheat-containing standard diet. Gliadin exacerbated the NSAID-induced small-intestinal damage in mice fed with a gluten-free diet. With the administration of indomethacin, MPO activity, a marker of neutrophil infiltration into the mucosa and mRNA expression level of tumor necrosis factor α and interleukin-1β in the small intestine were higher in the gliadin-administered mice. Gliadin increased the intestinal paracellular permeability without indomethacin administration (4.3-fold) and further increased the permeability after indomethacin administration (2.1-fold). Gliadin induced phosphorylation of epidermal growth factor receptor (EGFR) in small-intestinal tissues, and erlotinib (an EGFR tyrosine kinase inhibitor) attenuated the indomethacin-induced intestinal damage and permeability exacerbated by gliadin, accompanied by inhibition of EGFR phosphorylation. These results suggest that gliadin plays an important role in the induction and exacerbation of NSAID-induced small-intestinal damage, and that increase in intestinal permeability via the EGFR signalling pathway is involved in its mechanism.

Isoliquiritigenin Ameliorates Indomethacin-Induced Small Intestinal Damage by Inhibiting NOD-Like Receptor Family, Pyrin Domain-Containing 3 Inflammasome Activation

Activation of the NOD-Like Receptor Family, Pyrin Domain-Containing 3 (NLRP3) inflammasome, which consists of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and pro-caspase-1, triggers pro-caspase-1 cleavage promoting the processing of pro-interleukin (IL)-1β into mature IL-1β, which is critical for the development of non-steroidal anti-inflammatory drug (NSAID)-induced enteropathy. We investigated the effects of isoliquiritigenin, a flavonoid derived from the roots of Glycyrrhiza species, on NSAID-induced small intestinal damage and the inflammasome activation. To induce enteropathy, mice were administered indomethacin by gavage with or without isoliquiritigenin pretreatment. Some mice received an intraperitoneal injection of recombinant murine IL-1β in addition to isoliquiritigenin and indomethacin. Indomethacin induced small intestinal damage and increased protein levels of cleaved caspase-1 and mature IL-1β in the small intestine. Treatment with 7.5 and 75 mg/kg isoliquiritigenin inhibited indomethacin-induced small intestinal damage by 40 and 56%, respectively. Isoliquiritigenin also inhibited the indomethacin-induced increase in cleaved caspase-1 and mature IL-1β protein levels, whereas it did not affect the mRNA expression of NLRP3, ASC, caspase-1, and IL-1β. Protection against intestinal damage in isoliquiritigenin-treated mice was completely abolished with exogenous IL-1β. NLRP3^–/– and caspase-1^–/– mice exhibited resistance to intestinal damage, and isoliquiritigenin treatment failed to inhibit the damage in NLRP3^–/– and caspase-1^–/– mice. Isoliquiritigenin prevents NSAID-induced small intestinal damage by inhibiting NLRP3 inflammasome activation.

Trends in development of gi-safe anti-inflammatory drugs

Despite the introduction of anti-inflammatory drugs that selectively inhibit cyclo-oxygenase-2 (COX-2), and potent inhibitors of gastric acid secretion, the gastrointestinal adverse effects of non-steroidal anti-inflammatory drugs (NSAIDs) remain a significant clinical problem. Combined use of antisecretory drugs and COX-2 inhibitors is helpful to limit the damage in the proximal gastrointestinal tract (stomach and duodenum), but it increases the risk of injury of small intestine and colon. It was proven that proton pump inhibitors and H2 receptor antagonists significantly worsen NSAID-induced small intestinal damage and microbiota balance. Nowadays, there is no proven effective preventative or curative treatment for NSAID-induced enteropathy. The new strategy of gastrointestinal protection is based on the discovery of endogenous cytoprotective molecules such as hydrogen sulfide (H₂S). H2S is a gaseous mediator that produces strong cytoprotective and antioxidant effect on the gastrointestinal tract. The role of H₂S in promoting mucosal integrity, healing of tissue injury and resolution of inflammation has been well documented. In addition, H₂S stimulates productions of other cytoprotective molecules including prostaglandins, carbon monoxide and nitric oxide. Nowadays, the new generation of H₂S-releasing non-steroidal anti-inflammatory drugs is developed and tested in clinical trials. H₂S-NSAIDs possess enhanced anti-inflammatory activity and high gastrointestinal safety.

Present issues and measures for NSAID-induced small intestinal damage

Present issues and measures for NSAID-induced small intestinal damage

Influence of Adrenalectomy on Protective Effects of Urocortin I, a Corticotropin-Releasing Factor, Against Indomethacin-Induced Enteropathy in Rats.

We examined the influence of adrenalectomy on NSAID-induced small intestinal damage in rats and investigated the possible involvement of adrenal glucocorticoids in the protective effects of urocortin I, a corticotropin-releasing factor (CRF) agonist. Male SD rats without fasting were administered indomethacin s.c. and killed 24 h later in order to examine the hemorrhagic lesions that developed in the small intestine. Urocortin I (20 µg/kg) was given i.v. 10 min before the administration of indomethacin. Bilateral adrenalectomy was performed a week before the experiment. Indomethacin (10 mg/kg) caused multiple hemorrhagic lesions in the small intestine, which were accompanied by a decrease in mucus secretion and increases in intestinal motility, enterobacterial invasion, and iNOS expression. Adrenalectomy markedly increased the ulcerogenic and motility responses caused by indomethacin, with further enhancements in bacterial invasion and iNOS expression; severe lesions occurred at 3 mg/kg, a dose that did not induce any damage in sham-operated rats. This worsening effect was also observed by the pretreatment with mifepristone (a glucocorticoid receptor antagonist). Urocortin I prevented indomethacin-induced enteropathy, and this effect was completely abrogated by the pretreatment with astressin 2B, a CRF2 receptor antagonist, but was not significantly affected by either adrenalectomy or the mifepristone pretreatment. These results suggested that adrenalectomy aggravated the intestinal ulcerogenic response to indomethacin, the intestinal hypermotility response may be a key element in the mechanism for this aggravation, and endogenous glucocorticoids played a role in intestinal mucosal defense against indomethacin-induced enteropathy, but did not account for the protective effects of urocortin I, which were mediated by the activation of peripheral CRF2 receptors

Tu1841 Investigation of Indomethacin-Induced Small Intestinal Mucosal Damage in Atg5-Knock-out Mice, and the Molecular Mechanisms of Autophagy and Apoptosis

Background: In recent years, it has been shown that nonsteroidal anti-inflammatory drugs (NSAIDs) damage the mucosa of both the stomach and the small intestine. Various points are still unclear with respect to the pathology of NSAID-induced small intestinal mucosal damage, but attention has been given to the type of pathology that involves autophagy and cell death. For the present study, mice were prepared in which the Atg5 gene, essential for autophagy induction, was knocked out, in the small intestine only[w1] . Small intestinal mucosal damage induced by oral administration of indomethacin, an NSAID, was then compared between knock-out and normal mice. In addition, in order to elucidate the molecular mechanism, a study was carried out with IEC-6 cells, which are normal rat epithelial cells. Methods: Indomethacin was administered to normal mice and knock-out mice in the non-fasted state, and after 24 hours the entire damaged area of the small intestine was measured. In addition, Atg5-knock-out IEC-6 cells were administered indomethacin, and cell viability was determined. Furthermore, LC3, PARP1, Erk1/2, Nrf2, and HO-1 expression was investigated by the Western blot method. Results: The mean surface areas of small intestinal damage in normal mice and Atg5-knock-out mice were 16.26 ± 3.24 mm2 and 7.09 ± 2.24 mm2, respectively. Indomethacin-induced damage was also lower in Atg5-knock-out IEC-6 cells than in normal IEC-6 cells, and ERK, Nrf2, and HO-1 expression was higher in the former. Conclusions: It was confirmed that loss of autophagy results in reduction of indomethacin-induced small intestinal mucosal damage both in vivo and in vitro. It is known that HO-1 is induced by Nrf2, and Nrf2 is induced via the Erk pathway, suggesting the possibility that increased HO-1 expression mediated by the Erk-Nrf2 pathway, due to inhibition of autophagy, is the mechanism by which cytotoxicity is inhibited.

Beneficial effect of an omega-6 PUFA-rich diet in non-steroidal anti-inflammatory drug-induced mucosal damage in the murine small intestine

To investigate the effect of a fat rich diet on non-steroidal anti-inflammatory drug (NSAID)-induced mucosal damage in the murine small intestine. C57BL6 mice were fed 4 types of diets with or without indomethacin. One group was fed standard laboratory chow. The other groups were fed a fat diet consisting of 8% w/w fat, beef tallow (rich in SFA), fish oil, (rich in omega-3 PUFA), or safflower oil (rich in omega-6 PUFA). Indomethacin (3 mg/kg) was injected intraperitoneally from day 8 to day 10. On day 11, intestines and adhesions to submucosal microvessels were examined. In the indomethacin-treated groups, mucosal damage was exacerbated by diets containing beef tallow and fish oil, and was accompanied by leukocyte infiltration (P < 0.05). The mucosal damage induced by indomethacin was significantly lower in mice fed the safflower oil diet than in mice fed the beef tallow or fish oil diet (P < 0.05). Indomethacin increased monocyte and platelet migration to the intestinal mucosa, whereas safflower oil significantly decreased monocyte and platelet recruitment (P < 0.05). A diet rich in SFA and omega-3 PUFA exacerbated NSAID-induced small intestinal damage via increased leukocyte infiltration. Importantly, a diet rich in omega-6-PUFA did not aggravate inflammation as monocyte migration was blocked.

Protective Effect of Wheat Peptides Against Small Intestinal Damage Induced by Non-Steroidal Anti-Inflammatory Drugs in Rats

Non-steroidal anti-inflammatory drugs (NSAIDs) were able to produce tissue damage and oxidative stress in animal models of small intestinal damage. In this study, the putative protective effect of wheat peptides was evaluated in a NSAID-induced small intestinal damage model in rats, different doses of wheat peptides or distilled water were administered daily by intragastric administration for 30 d until small intestinal damage was caused. Before sacrificing, NSAIDs (aspirin and indomethacin) or physiological saline were infused into the digestive tract twice. Wheat peptides administration reduced edema and small intestinal damage, and significantly decreased the level of tumor necrosis factor (TNF)-α in mucous membrane of small intestine. Oxidative stress was significantly increased after NSAID infusion and was reduced by wheat peptides. Wheat peptides increased glutathione peroxidase (GSH-Px) activity in mucous membrane of small intestine. μ-Opioid receptor mRNA expression decreased more significantly in wheat peptides treated rats than in the model control group. Overall, the results suggest that non-steroidal anti-inflammatory drugs induced small intestinal damage in rats and wheat peptides administration may be an effective tool for protecting small intestinal tissue against NSAID-induced small intestinal damage and oxidative stress.

SAT0117 Reduction of Nsaid-Induced Small Intestinal Damage in Rheumatoid Arthritis Patients Receiving Sulfasalazine

BackgroundRecent studies have demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs) often cause damage to the small intestine, and NSAID-induced enteropathy is mediated by different inflammatory cytokines. Sulfasalazine is being widely used...

Prophylactic Effect of Monosodium Glutamate on NSAID-Induced Enteropathy in Rats

We reviewed the prophylactic effect of monosodium glutamate (MSG), a substance known as the "umami", on NSAID-induced small intestinal damage in rats. Loxoprofen, one of the NSAIDs frequently used in Asian countries, given orally at 60 mg/kg, caused hemorrhagic damage in the small intestine, mainly jejunum and ileum, concomitant with a down-regulation of Muc2 expression/ mucus secretion and an up-regulation of enterobacterial invasion and neutrophil migration as well as inducible nitric oxide synthase (iNOS) expression. The severity of these lesions was reduced by pretreatment with MSG (0.1~5%) given as a mixture of powder food (10 g/rat/day) for 5 days before administration of loxoprofen. The effect of MSG was accompanied by an up-regulation of Muc2 expression/ mucus secretion as well as a suppression of bacterial invasion, iNOS expression and myeloperoxidase activity. On the other hand, these lesions spontaneously healed within 7 days, but this process was hampered by loxoprofen at low doses (>10 mg/kg) given repeatedly for 5 days after ulceration. The healing-impairment effect of loxoprofen was accompanied by the down-regulation of vascular endothelium- derived growth factor (VEGF) expression and angiogenic response, and these responses were all antagonized by feeding diet containing 5% MSG for 5 days after ulceration. It is suggested that MSG exhibits a prophylactic effect against loxoprofen-induced small intestinal lesions, this effect is functionally associated with the up-regulation of Muc2 expression/mucus secretion, resulting in suppression of enterobacterial invasion and iNOS expression, the major pathogenic events in NSAID-induced enteropathy, and MSG also has the healing promoting effect on these lesions through enhancement of VEGF expression and angiogenesis.

Role of small intestinal bacterial overgrowth in severe small intestinal damage in chronic non-steroidal anti-inflammatory drug users

Objective. Enteric bacteria play a significant role in the pathogenesis of non-steroidal anti-inflammatory drug (NSAID)-induced small intestinal damage. However, the association between small intestinal bacterial overgrowth (SIBO) and NSAID-induced small intestinal damage remains unclear. The aim of the study was to examine the association between SIBO and the presence of NSAID-induced severe small intestinal damage or its symptoms in chronic NSAID users. Materials and methods. Forty-three patients who had been using NSAIDs for over 3 months were enrolled. They were examined by capsule endoscopy and a lactulose hydrogen breath test (LHBT). We defined severe small intestinal damage as the presence of more than four small erosions or large erosions/ulcers. The LHBT result was considered positive if there was an increase in the level of breath hydrogen gas of >20 ppm above baseline. Results. Out of 43 patients, 22 (51%) had severe small intestinal damage. The LHBT was positive in 5 of 21 patients (24%) without severe small intestinal damage and in 13 of 21 patients (59%) with severe small intestinal damage. Multiple logistic regression analysis showed that an LHBT-positive result was significantly associated with increased odds ratio for severe small intestinal damage (OR, 6.54; 95% CI, 1.40–30.50). There was no significant difference in the presence of symptoms between the LHBT-positive and LHBT-negative patients with severe small intestinal damage. Conclusion. SIBO might have a role in the development of severe small intestinal damage in chronic NSAID users.

Anti-tumour necrosis factor agents reduce non-steroidal anti-inflammatory drug-induced small bowel injury in rheumatoid arthritis patients

ObjectiveThe role of tumour necrosis factor α (TNFα) in the pathogenesis of non-steroidal anti-inflammatory drug (NSAID)-induced small intestinal damage remains unclear. We evaluated the preventive effect of anti-TNF therapy against...

Mo1819 Reduction of NSAID-Induced Small Intestinal Damage in Rheumatoid Arthritis Patients Receiving Anti-Tumor Necrosis Factor Therapy: A Cohort Study and Propensity-Matched Analysis

perilipin2, whose expression correlates with LD status, was found inmouse inflamed intestinal epithelia with a remarkably higher perilipin2 associated with FOXO3 deficiency (Fig 1A). This supports an increase and FOXO3 dependent LD density in mouse inflamed intestinal epithelia. Pro-inflammatory TNF strikingly increases LD density in IC; a 2-fold increase in LD positive IC and a 2-fold increase of LDs per IC (Fig 1B). Moreover, since, here, we found that human recombinant IL-8 binds to the lipids (Fig 2A), we assessed if intracellular IL-8 is stored in LDs. In IC, TNF-induced intracellular IL-8 is co-localized within LDs while C75 attenuates this co-localization (Fig 2B). Also, TNF-induced released IL-8 was significantly attenuated by C75 (Con: 13±2 pg/ml, TNF: 1,336±70 pg/ml vs C75: 34±17 pg/ml, C75/ TNF: 9±1 pg/ml) (Fig 2C). These data suggest that in IC, LDs play a critical role in the regulation of IL-8 in both intracellular storage and release. Conclusion: These findings reveal a critical role of LDs in intestinal inflammation and present a novel characteristic of intracellular lipids in the disease. These findings provide the opportunity to pursue new therapeutic strategies that target LDs in order to treat intestinal inflammation.

High Mobility Group Box 1 Promotes Small Intestinal Damage Induced by Nonsteroidal Anti-Inflammatory Drugs through Toll-Like Receptor 4

Release of high mobility group box 1 (HMGB1) from damaged cells, which is involved in many types of tissue injuries, activates inflammatory pathways by stimulating multiple receptors, including Toll-like receptor 2 (TLR2), TLR4, and receptor for advanced glycation end-products (RAGE). Our objective was to determine the role of HMGB1 in nonsteroidal anti-inflammatory drug (NSAID)-induced damage of the small intestine. Oral indomethacin (10 mg/kg) induced damage to the small intestine and was associated with increases in intestinal HMGB1 expression and serum HMGB1 levels. In wild-type mice, recombinant human HMGB1 aggravated indomethacin-induced small intestinal damage; enhanced the mRNA expression levels of tumor necrosis factor α (TNF-α), monocyte chemotactic protein 1, and KC; activated nuclear factor kappa B; and stimulated phosphorylation of the mitogen-activated protein kinases p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). In contrast, blocking HMGB1 action with neutralizing antibodies prevented damage and inhibited both inflammatory cytokine overexpression and activation of these intracellular signaling pathways. TLR2-knockout (KO) and RAGE-KO mice exhibited high sensitivities to indomethacin-induced damage, similar to wild-type mice, whereas TLR4-KO mice exhibited less severe intestinal damage and lower levels of TNF-α mRNA expression. Exogenous HMGB1 aggravated the damage in TLR2- and RAGE-KO mice but did not affect the damage in TLR4-KO mice. Thus, our results suggest that HMGB1 promotes NSAID-induced small intestinal damage through TLR4-dependent signaling pathways.

PPIs shown to exacerbate NSAID injury in rats through dysbiosis

PPIs significantly exacerbate NSAID-induced small intestinal damage, and such exacerbation is linked to marked shifts in the intestinal microbiota, so reports a study published in Gastroenterology.

Lubiprostone Prevents NSAID-Induced Small Intestinal Damage by Suppression of Inflammatory Mediators' Expression via EP4 Receptors

Background: Previously, we have reported that inflammatory mediators such as lipopolysaccharide promote indomethacin (Indo)-induced small intestinal damage via Toll-like receptor (TLR) 4 (Watanabe T et al, GUT 2008 ). High-mobility group box-1 (HMGB1), originally identified as a DNA binding protein, also has potent proinflammatory properties as an alarmin. HMGB1 exerts proinflammatory effect via the receptor for advanced glycation endproducts (RAGE) and Toll-like receptors (TLRs). AIM: To investigate the role of HMGB1 and the receptor responsible for HMGB1 in Indo-induced small intestinal damage.Methods: Indo (10 mg/kg body weight) was administered orally to C57BL/6J mice, and the small intestines were removed at 3, 6, 12, and 24 h after the administration of Indo.The mRNA expression of tumor necrosis factor-α (TNF-α), keratinocyte chemoattractant (KC), monocyte chemotactic protein-1 (MCP1), TLR4, RAGE, and HMGB1 were assessed by real-time reverse transcription-polymerase chain reaction. Localization of TLR4, RAGE, and HMGB1 in the small intestine was determined by immunohistochemical examination. To clarify the role of HMGB1 in Indo-induced small intestinal damage, mouse recombinant HMGB1 (rHMGB1), anti-HMGB1 neutralizing antibodies, ethyl pyruvate, which inhibits secretion of HMGB1, or nonspecific chicken IgY were intraperitoneally administered to the mice after administration of Indo and the small intestinal damage was evaluated. To investigate the involvement of RAGE and TLR4 in HMGB-1-mediated Indo-induced small intestinal damage, RAGE knockout (KO) or TLR4 KO or wild-type mice were intraperitoneally administered rHMGB1 accompanied by Indo administration and the damage was evaluated. Results: Indo-induced small intestinal damage occurred 3 h after the administration of Indo and the damage was accompanied by an increase in the expression of TNF-α and KCmRNAs in the small intestine. HMGB-1, TLR4, and RAGE mRNAs were constitutively expressed. Immunoreactivity for HMGB1 was mainly observed in the nuclei of the intestinal epithelial cells and inflammatory cells. Immunoreactivity for RAGE and TLR4 was mainly observed in macrophage cells. Inhibition of HMGB1 by neutralizing antibodies and ethyl pyruvate reduced the small intestinal damage, accompanied by reduction in the expression of TNF-α, KC, and MCP1 mRNAs, while rHMGB1 further increased the Indo-induced small intestinal damage. The Indo-induced small intestinal damage observed in RAGE KO mice was almost of the same level as that observed in wild-type mice, while gene disruption of TLR4 resulted in decrease in Indo-induced small intestinal damage. Conclusion: These results suggest that HMGB1 acts as a factor promoting the Indo-induced small intestinal damage by upregulating the proinflammatory cytokines through TLR4.