Dopamine D₂-receptor antagonists ameliorate indomethacin-induced small intestinal ulceration in mice by activating α7 nicotinic acetylcholine receptors

Traditional Chinese medicine for functional gastrointestinal disorders and inflammatory bowel disease: narrative review of the evidence and potential mechanisms involving the brain-gut axis

Functional gastrointestinal disorders (FGIDs) and inflammatory bowel disease (IBD) are common clinical disorders characterized by recurrent diarrhea and abdominal pain. Although their pathogenesis has not been fully clarified, disruptions in intestinal motility and immune function are widely accepted as contributing factors to both conditions, and the brain-gut axis plays a key role in these processes. Traditional Chinese Medicine (TCM) employs a holistic approach to treatment, considers spleen and stomach impairments and liver abnormality the main pathogenesis of these two diseases, and offers a unique therapeutic strategy that targets these interconnected pathways. Clinical evidence shows the great potential of TCM in treating FGIDs and IBD. This study presents a systematic description of the pathological mechanisms of FGIDs and IBD in the context of the brain-gut axis, discusses clinical and preclinical studies on TCM and acupuncture for the treatment of these diseases, and summarizes TCM targets and pathways for the treatment of FGIDs and IBD, integrating ancient wisdom with contemporary biomedical insights. The alleviating effects of TCM on FGID and IBD symptoms are mainly mediated through the modulation of intestinal immunity and inflammation, sensory transmission, neuroendocrine-immune network, and microbiota and their metabolism through brain-gut axis mechanisms. TCM may be a promising treatment option in controlling FGIDs and IBD; however, further high-quality research is required. This review provides a reference for an in-depth exploration of the interventional effects and mechanisms of TCM in FGIDs and IBD, underscoring TCM's potential to recalibrate the dysregulated brain-gut axis in FGIDs and IBD.

Deficiency of leukotriene B4 receptor type 1 ameliorates ovalbumin-induced allergic enteritis in mice

Leukotriene B4 receptor type 1 (BLT1), a high-affinity receptor for leukotriene B4 (LTB4), plays an important role in inflammatory responses, including allergic airway inflammation. In this study, we examined the effect of genetic BLT1 deletion (BLT1KO) on ovalbumin (OVA)-induced allergic enteritis in mice to determine the pathogenic role of LTB4/BLT1 in allergic enteritis, a gastrointestinal form of food allergy. Repeated oral OVA challenges after sensitization with OVA and aluminium potassium sulphate induced allergic enteritis, characterized by systemic allergic symptoms (scratching, immobility and swelling), diarrhoea, colonic oedema and colonic goblet cell hyperplasia, accompanied by increased colonic peroxidase activity, colonic inflammatory cytokine expression and increased serum OVA-specific IgE levels. The severity of enteritis was significantly attenuated in BLT1KO mice compared with wild-type (WT) mice, without an increase in serum OVA-specific IgE levels. The accumulation of neutrophils, eosinophils, M2-macrophages, dendritic cells, CD4+ T cells and mast cells was observed in the colonic mucosa of allergic enteritis, and such accumulation was significantly lower in BLT1KO mice than in WT mice. BLT1 expression was upregulated and colocalized mostly in neutrophils and partly in eosinophils and dendritic cells in the colonic mucosa of allergic enteritis. These findings indicate that BLT1 deficiency ameliorates OVA-induced allergic enteritis in mice and that LTB4/BLT1 contributes to neutrophil and eosinophil accumulation in the allergic colonic mucosa. Therefore, BLT1 is a promising drug target for treating food allergies.

Capsaicin inhibits intestinal Cl- secretion and promotes Na+ absorption by blocking TRPV4 channels in healthy and colitic mice

Although capsaicin has been studied extensively as an activator of the transient receptor potential vanilloid cation channel subtype 1 (TRPV1) channels in sensory neurons, little is known about its TRPV1-independent actions in gastrointestinal health and disease. Here, we aimed to investigate the pharmacological actions of capsaicin as a food additive and medication on intestinal ion transporters in mouse models of ulcerative colitis (UC). The short-circuit current (Isc) of the intestine from WT, TRPV1-, and TRPV4-KO mice were measured in Ussing chambers, and Ca2+ imaging was performed on small intestinal epithelial cells. We also performed Western blots, immunohistochemistry, and immunofluorescence on intestinal epithelial cells and on intestinal tissues following UC induction with dextran sodium sulfate. We found that capsaicin did not affect basal intestinal Isc but significantly inhibited carbachol- and caffeine-induced intestinal Isc in WT mice. Capsaicin similarly inhibited the intestinal Isc in TRPV1 KO mice, but this inhibition was absent in TRPV4 KO mice. We also determined that Ca2+ influx via TRPV4 was required for cholinergic signaling-mediated intestinal anion secretion, which was inhibited by capsaicin. Moreover, the glucose-induced jejunal Iscvia Na+/glucose cotransporter was suppressed by TRPV4 activation, which could be relieved by capsaicin. Capsaicin also stimulated ouabain- and amiloride-sensitive colonic Isc. Finally, we found that dietary capsaicin ameliorated the UC phenotype, suppressed hyperaction of TRPV4 channels, and rescued the reduced ouabain- and amiloride-sensitive Isc. We therefore conclude that capsaicin inhibits intestinal Cl- secretion and promotes Na+ absorption predominantly by blocking TRPV4 channels to exert its beneficial anti-colitic action.

A quinazoline-based bromodomain inhibitor, CN210, ameliorates indomethacin-induced ileitis in mice by inhibiting inflammatory cytokine expression

Inhibitors of bromodomain and extra-terminal motif (BET) proteins are emerging epigenetic therapeutics that suppress gene expressions that drive cancer and inflammation. The present study examined anti-inflammatory effects of a quinazoline-based BET inhibitor, CN210, in a murine ileitis model. CN210 was given orally 30 min before and 24 h after a subcutaneous administration of indomethacin. Macroscopic and histological evidences of ileitis, mucosal myeloperoxidase (MPO) activity and cytokine expressions were evaluated 48 h after the indomethacin administration. To further characterize the anti-inflammatory pathways modulated by CN210, its effects on RAW264 cells treated with lipopolysaccharide (LPS) were investigated. Competitive ligand binding and docking studies of CN210 to CREB-binding protein (CBP) and p300 were also performed. Oral administration of CN210 significantly reduced the severity of ileitis, normalized both proinflammatory MPO activity and concomitant cytokine expressions induced by indomethacin administration. Furthermore, CN210 attenuated the expression of cytokines and reversed the activation of nuclear factor κB (NF-κB) and mitogen-activated protein kinases (MAPK) induced by LPS. Competitive ligand binding assays showed that CN210 bound to the bromodomains of two paralogous histone acetyltransferases, CBP and p300, in addition to the bromodomains of BET proteins. Docking studies of CN210 to the bromodomains of CBP and p300 showed a similarity to the binding mode of SGC-CBP30, a specific CBP/p300 inhibitor. CN210 ameliorates indomethacin-induced ileitis by inhibiting the expression of inflammatory cytokines through the attenuation of NF-κB and MAPK pathways. CN210 thus represents a new mode of therapy for non-steroidal anti-inflammatory drug-induced ileitis and inflammatory bowel disease.

Source of dopamine in gastric juice and luminal dopamine-induced duodenal bicarbonate secretion via apical dopamine D2 receptors

BACKGROUND AND PURPOSE

Dopamine protects the duodenal mucosa. Here we have investigated the source of dopamine in gastric juice and the mechanism underlying the effects of luminal dopamine on duodenal bicarbonate secretion (DBS) in rodents.

EXPERIMENTAL APPROACH

Immunofluorescence, UPLC-MS/MS, gastric incubation and perfusion were used to detect gastric-derived dopamine. Immunofluorescence and RT-PCR were used to examine the expression of dopamine receptors in the duodenal mucosa. Real-time pH titration and pHi measurement were performed to investigate DBS.

KEY RESULTS

H+ -K+ -ATPase was co-localized with tyrosine hydroxylase and dopamine transporters in gastric parietal cells. Dopamine was increased in in vivo gastric perfusate after intravenous infusion of histamine and in gastric mucosa incubated, in vitro, with bethanechol chloride or tyrosine. D2 receptors were the most abundant dopamine receptors in rat duodenum, mainly distributed on the apical membrane of epithelial cells. Luminal dopamine increased DBS in a concentration-dependent manner, an effect mimicked by a D2 receptor agonist quinpirole and inhibited by the D2 receptor antagonist L741,626, in vivo D2 receptor siRNA and in D2 receptor -/- mice. Dopamine and quinpirole raised the duodenal enterocyte pHi . Quinpirole-evoked DBS and PI3K/Akt activity were inhibited by calcium chelator BAPTA-AM or in D2 receptor-/- mice.

CONCLUSION AND IMPLICATIONS

Dopamine in the gastric juice is derived from parietal cells and is secreted along with gastric acid. On arrival in the duodenal lumen, dopamine increased DBS via an apical D2 receptor- and calcium-dependent pathway. Our data provide novel insights into the protective effects of dopamine on the duodenal mucosa.

Perphenazine Attenuates the Pro-Inflammatory Responses in Mouse Models of Th2-Type Allergic Dermatitis

Developing dermatitis therapeutics has been faced with challenges including adverse effects of topical steroid and high cost of new developing drugs. Here, we found the expression levels of dopamine receptor D2 is higher in skin biopsies of dermatitis patients and an oxazolone-induced animal model of dermatitis. We used perphenazine, an FDA-approved dopamine receptor antagonist to determine the therapeutic effect. Two different animal models including 12-o-tetradecanoylphorbol-13-acetate (TPA) and oxazolone (OXA)-induced dermatitis were employed. TPA and OXA-mediated ear swelling was attenuated by perphenazine. Moreover, perphenazine inhibited infiltrated mast cells into lesion area. We found levels of serum IgE, histamine and cytokines are decreased in mice cotreated with perphenazine and OXA compared to OXA-treated mice. Overall, this is a first study showing that the FDA-approved, anti-psychotic drug, perphenazine, alleviates animal models of dermatitis.

Leukotriene B4 Receptor Type 2 Accelerates the Healing of Intestinal Lesions by Promoting Epithelial Cell Proliferation

Leukotriene B4 receptor type 2 (BLT2) is a low-affinity leukotriene B4 receptor that is highly expressed in intestinal epithelial cells. Previous studies demonstrated the protective role of BLT2 in experimentally induced colitis. However, its role in intestinal lesion repair is not fully understood. We investigated the role of BLT2 in the healing of indomethacin-induced intestinal lesions in mice. There was no significant different between wild-type (WT) and BLT2-deficient (BLT2KO) mice in terms of the development of indomethacin-induced intestinal lesions. However, healing of these lesions was significantly impaired in BLT2KO mice compared with WT mice. In contrast, transgenic mice with intestinal epithelium-specific BLT2 overexpression presented with superior ileal lesion healing relative to WT mice. An immunohistochemical study showed that the number of Ki-67-proliferative cells was markedly increased during the healing of intestinal lesions in WT mice but significantly attenuated in BLT2KO mice. Exposure of cultured mouse intestinal epithelial cells to CAY10583, a BLT2 agonist, promoted wound healing and cell proliferation in a concentration-dependent manner. Nevertheless, these responses were abolished under serum-free conditions. The CAY10583-induced proliferative effect was also negated by Go6983, a protein kinase C (PKC) inhibitor, U-73122, a phospholipase C (PLC) inhibitor, LY255283, a BLT2 antagonist, and pertussis toxin that inhibits G protein-coupled receptor signaling via Gi/o proteins. Thus, BLT2 plays an important role in intestinal wound repair. Moreover, this effect is mediated by the promotion of epithelial cell proliferation via the Gi/o protein-dependent and PLC/PKC signaling pathways. The BLT2 agonists are potential therapeutic agents for the treatment of intestinal lesions. SIGNIFICANCE STATEMENT: The healing of indomethacin-induced Crohn's disease-like intestinal lesions was impaired in mice deficient in low-affinity leukotriene B4 receptor type 2 (BLT2). They presented with reduced epithelial cell proliferation during the healing. In contrast, healing was promoted in mice overexpressing intestinal epithelial BLT2. In cultured intestinal epithelial cells, the BLT2 agonist CAY10583 substantially accelerated wound repair by enhancing cell proliferation rather than migration. Thus, BLT2 plays an important role in the intestinal lesions via acceleration of epithelial cell proliferation.

Energy-Dependent Endocytosis is Involved in the Absorption of Indomethacin Nanoparticles in the Small Intestine

We previously reported that oral formulations containing indomethacin nanoparticles (IND-NPs) showed high bioavailability, and, consequently, improved therapeutic effects and reduced injury to the small intestine. However, the pathway for the transintestinal penetration of nanoparticles remained unclear. Thus, in this study, we investigated whether endocytosis was related to the penetration of IND-NPs (72.1 nm) using a transcell set with Caco-2 cells or rat intestine. Four inhibitors of various endocytosis pathways were used [nystatin, caveolae-dependent endocytosis (CavME); dynasore, clathrin-dependent endocytosis (CME); rottlerin, macropinocytosis; and cytochalasin D, phagocytosis inhibitor], and all energy-dependent endocytosis was inhibited at temperatures under 4 °C in this study. Although IND-NPs showed high transintestinal penetration, no particles were detected in the basolateral side. IND-NPs penetration was strongly prevented at temperatures under 4 °C. In experiments using pharmacological inhibitors, only CME inhibited penetration in the jejunum, while in the ileum, both CavME and CME significantly attenuated penetration. In conclusion, we found a novel pathway for the transintestinal penetration of drug nanoparticles. Our hypothesis was that nanoparticles would be taken up into the intestinal epithelium by endocytosis (CME in jejunum, CavME and CME in ileum), and dissolved and diffused in the intestine. Our findings are likely to be of significant use for the development of nanomedicines.

Transient receptor potential vanilloid 4 channel regulates vascular endothelial permeability during colonic inflammation in dextran sulphate sodium-induced murine colitis

BACKGROUND AND PURPOSE

The transient receptor potential vanilloid 4 (TRPV4) channel is a non-selective cation channel involved in physical sensing in various tissue types. The present study aimed to elucidate the function and expression of TRPV4 channels in colonic vascular endothelial cells during dextran sulphate sodium (DSS)-induced colitis.

EXPERIMENTAL APPROACH

The role of TRPV4 channels in the progression of colonic inflammation was examined in a murine DSS-induced colitis model using immunohistochemical analysis, Western blotting and Evans blue dye extrusion assay.

KEY RESULTS

DSS-induced colitis was significantly attenuated in TRPV4-deficient (TRPV4 KO) as compared to wild-type mice. Repeated intrarectal administration of GSK1016790A, a TRPV4 agonist, exacerbated the severity of DSS-induced colitis. Bone marrow transfer experiments demonstrated the important role of TRPV4 in non-haematopoietic cells for DSS-induced colitis. DSS treatment up-regulated TRPV4 expression in the vascular endothelia of colonic mucosa and submucosa. DSS treatment increased vascular permeability, which was abolished in TRPV4 KO mice. This DSS-induced increase in vascular permeability was further enhanced by i.v. administration of GSK1016790A, and this effect was abolished by the TRPV4 antagonist RN1734. TRPV4 was co-localized with vascular endothelial (VE)-cadherin, and VE-cadherin expression was decreased by repeated i.v. administration of GSK1016790A during colitis. Furthermore, GSK106790A decreased VE-cadherin expression in mouse aortic endothelial cells exposed to TNF-α.

CONCLUSION AND IMPLICATIONS

These findings indicate that an up-regulation of TRPV4 channels in vascular endothelial cells contributes to the progression of colonic inflammation by increasing vascular permeability. Thus, TRPV4 is an attractive target for the treatment of inflammatory bowel diseases.

Apoptosis, Dysbiosis and Expression of Inflammatory Cytokines are Sequential Events in the Development of 5-Fluorouracil-Induced Intestinal Mucositis in Mice

The chemotherapeutic agent 5-fluorouracil (5-FU) causes intestinal mucositis with severe diarrhoea, but the pathogenesis is not fully understood. In this study, we investigated the pathogenic effects of 5-FU in mice, focusing on apoptosis, enterobacteria and inflammatory cytokines. Repeated administration of 5-FU caused severe intestinal mucositis on day 6, accompanied by diarrhoea and body-weight loss. TNF-α expression increased 1 day after exposure to the drug, and spiked a second time on day 4, at which point myeloperoxidase activity and IL-1β expression also increased. Apoptotic cells were observed in intestinal crypts only on day 1. 5-FU also induced dysbiosis, notably decreasing the abundance of intestinal Firmicutes while increasing the abundance of Bacteroidetes and Verrucomicrobia. Twice-daily co-administration of oral antibiotics significantly reduced the severity of intestinal mucositis and dysbiosis, and blocked the increase in myeloperoxidase activity and cytokine expression on day 6, without affecting apoptosis and TNF-α up-regulation on day 1. In cultured colonic epithelial cells, exposure to 5-FU also up-regulated TNF-α expression. Collectively, the data suggest that crypt apoptosis, dysbiosis and expression of inflammatory cytokines are sequential events in the development of intestinal mucositis after exposure to 5-FU. In particular, 5-FU appears to directly induce apoptosis via TNF-α and to suppress intestinal cell proliferation, thereby resulting in degradation of the epithelial barrier, as well as in secondary inflammation mediated by inflammatory cytokines.

NOX1/NADPH Oxidase Expressed in Colonic Macrophages Contributes to the Pathogenesis of Colonic Inflammation in Trinitrobenzene Sulfonic Acid-Induced Murine Colitis

NOX1/NADPH oxidase, a nonphagocytic isoform of reactive oxygen species-producing enzymes, is highly expressed in the colon, but the physiologic and pathophysiologic roles of this isoform are not fully understood. The present study investigated the role of NOX1 in the development of colonic inflammation in a trinitrobenzene sulfonic acid (TNBS)-induced murine colitis model. Intrarectal injection of TNBS caused severe colitis accompanied by body weight loss, diarrhea, and increased myeloperoxidase (MPO) activity in wild-type (WT) mice. In contrast, the severity of colitis was significantly attenuated in NOX1-deficient (NOX1KO) mice (the inhibitions of macroscopic damage score, body weight loss, diarrhea score, and MPO activity were 73.1%, 36.8%, 83.3%, and 98.4%, respectively). TNBS-induced upregulation of inflammatory cytokines (tumor necrosis factor (TNF)-α and interleukin (IL)-1β), chemokines (CXCL1 and CXLC2), and inducible nitric oxide synthase (iNOS) was also significantly less in NOX1KO than in WT mice (the inhibitions were 100.8%, 89.0%, 63.5%, 96.7%, and 97.1%, respectively). Expression of NOX1 mRNA was detected not only in the lamina propria but also in peritoneal macrophages isolated from WT mice. Increased expression of TNF-α, IL-1β, and iNOS in peritoneal macrophages exposed to lipopolysaccharide was significantly attenuated in macrophages isolated from NOX1KO mice (68.1%, 67.0%, and 79.3% inhibition, respectively). These findings suggest that NOX1/NADPH oxidase plays an important role in the pathogenesis of TNBS-induced colonic inflammation via upregulation of inflammatory cytokines, chemokines, and iNOS. NOX1 in colonic macrophages may become a potential target in pharmacologic intervention for inflammatory bowel disease.

5-HT3 receptors promote colonic inflammation via activation of substance P/neurokinin-1 receptors in dextran sulphate sodium-induced murine colitis

BACKGROUND AND PURPOSE

5-HT (serotonin) regulates various physiological functions, both directly and via enteric neurons. The present study investigated the role of endogenous 5-HT and 5-HT3 receptors in the pathogenic mechanisms involved in colonic inflammation, especially in relation to substance P (SP) and the neurokinin-1 (NK1 ) receptor.

EXPERIMENTAL APPROACH

The effects of 5-HT3 and NK1 receptor antagonists were examined in dextran sulphate sodium (DSS)-induced colitis in mice. Inflammatory mediator expression and the distribution of 5-HT3 and NK1 receptors were also determined.

KEY RESULTS

Daily administration of ramosetron and ondansetron (5-HT3 antagonists) dose-dependently attenuated the severity of DSS-induced colitis and up-regulation of inflammatory mediator expression. Immunohistochemical analysis showed 5-HT3 receptors are mainly expressed in vesicular ACh transporter-positive cholinergic nerve fibres in normal colon. DSS increased the number of colonic nerve fibres that were double positive for 5-HT3 receptors and SP but not of those that were double positive for 5-HT3 receptors and vesicular ACh transporter. DSS increased colonic SP levels and SP-positive nerve fibres; these responses were attenuated by ramosetron. DSS-induced colitis and up-regulation of inflammatory mediators were attenuated by aprepitant, an NK1 antagonist. Immunohistochemical studies further revealed that DSS treatment markedly increased NK1 receptor expression in CD11b-positive cells.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that the 5-HT/5-HT3 receptor and SP/NK1 receptor pathways play pathogenic roles in colonic inflammation. 5-HT acts via 5-HT3 receptors to up-regulate inflammatory mediators and promote colonic inflammation. These effects may be further mediated by activation of macrophage NK1 receptors via SP released from 5-HT3 receptor-positive nerve fibres.

Water avoidance stress induces visceral hyposensitivity through peripheral corticotropin releasing factor receptor type 2 and central dopamine D2 receptor in rats

BACKGROUND

Water avoidance stress (WAS) is reported to induce functional changes in visceral sensory function in rodents, but the results which have been demonstrated so far are not consistent, i.e., hypersensitivity or hyposensitivity. We determined the effect of WAS on visceral sensation and evaluated the mechanisms of the action.

METHODS

Visceral sensation was assessed by abdominal muscle contractions induced by colonic balloon distention, i.e., visceromotor response (VMR), measured electrophysiologically in conscious rats. The electromyogram electrodes were acutely implanted under anesthesia on the day of the experiment. The threshold of VMR was measured before and after WAS for 1 h. To explore the mechanisms of WAS-induced response, drugs were administered 10 min prior to the initiation of WAS.

KEY RESULTS

WAS significantly increased the threshold of VMR, and this effect was no longer detected at 24 h after. Intraperitoneal injection of astressin2 -B (200 μg/kg), a corticotropin releasing factor (CRF) receptor type 2 antagonist abolished the response by WAS. Subcutaneous (sc) injection of sulpiride (200 mg/kg), a dopamine D2 receptor antagonist blocked the response, while sc domperidone (10 mg/kg), a peripheral dopamine D2 receptor antagonist did not alter it. Naloxone (1 mg/kg, sc), an opioid antagonist did not modify it either.

CONCLUSIONS & INFERENCES

WAS induced visceral hyposensitivity through peripheral CRF receptor type 2 and central dopamine D2 receptor, but not through opioid pathways. As altered pain inhibitory system was reported to be observed in the patients with irritable bowel syndrome, CRF and dopamine signaling might contribute to the pathophysiology.

Preventative Effects of Sodium Alginate on Indomethacin-induced Small-intestinal Injury in Mice

Recent advances in diagnostic technologies have revealed that nonsteroidal anti-inflammatory drugs (NSAIDs) can cause serious mucosal injury in the upper and lower gastrointestinal tract (including the small intestine). A drug to treat NSAID-induced small-intestinal injury (SII) is lacking. Sodium alginate is a soluble dietary fiber extracted from brown seaweed and its solution has been used as a hemostatic agent to treat gastrointestinal bleeding due to gastric ulcers. Whether sodium alginate has therapeutic effects on NSAID-induced SII and its mechanism of action are not known. Here, we investigated if administration of two forms (high-molecular-weight (HMW) and low-molecular-weight (LMW)) of sodium alginate could ameliorate indomethacin-induced SII. Pretreatment with HMW sodium alginate or LMW sodium alginate before indomethacin administration improved ulceration and the resultant intestinal shortening was associated with reduced histological severity of mucosal injury and ameliorated mRNA expression of inflammation-related molecules in the small intestine. We found that mRNAs of secretory Muc2 and membrane-associated Muc1, Muc3 and Muc4 were expressed in the small intestine. mRNA expression of Muc1-4 was increased in indomethacin-induced SII, and these increases were prevented by sodium alginate. Thus, administration of sodium alginate could be a therapeutic approach to prevent indomethacin-induced SII.

Effect of 18β-glycyrrhetinic acid and hydroxypropyl γcyclodextrin complex on indomethacin-induced small intestinal injury in mice

Non-steroidal anti-inflammatory drugs (NSAIDs)-induced small intestinal injury is a serious clinical event with recent advances of diagnostic technologies, but a successful therapeutic method to treat such injuries is still lacking. Licorice, a traditional herbal medicine, and its derivatives have been widely used for the treatment of a variety of diseases due to their extensive biological actions. However, it is unknown whether these derivatives have an effect on NSAIDs-induced small intestinal damage. Previously, the anti-inflammatory effects of three compounds extracted from the licorice root, glycyrrhizin, 18β-glycyrrhetinic acid, and dipotassium glycyrrhizinate, were compared in vitro cell culture. The most prominent inhibitory effect on the tumor necrosis factor-α (TNF-α) production was observed with the administration of 18β-glycyrrhetinic acid as an active metabolite of glycyrrhizin. In this study, a complex compound of 18β-glycyrrhetinic acid and hydroxypropyl γcyclodextrin was examined to improve the oral bioavailability. After administration of this complex to indomethacin treated mice, a significantly high plasma concentration of 18β-glycyrrhetinic acid was detected using the tandem mass spectrometry coupled with the HPLC. Furthermore, the complex form of 18β-glycyrrhetinic acid and hydroxypropyl γcyclodextrin reduced mRNA expressions of TNF-α, interleukin (IL)-1β, and IL-6, which was histologically confirmed in the improvement of indomethacin-induced small intestinal damage. These results suggest that the complex of 18β-glycyrrhetinic acid and hydroxypropyl γcyclodextrin has the potential therapeutic value for preventing the adverse effects of indomethacin-induced small intestinal injury.

Mechanisms, prevention and clinical implications of nonsteroidal anti-inflammatory drug-enteropathy

This article reviews the latest developments in understanding the pathogenesis, detection and treatment of small intestinal damage and bleeding caused by nonsteroidal anti-inflammatory drugs (NSAIDs). With improvements in the detection of NSAID-induced damage in the small intestine, it is now clear that this injury and the associated bleeding occurs more frequently than that occurring in the stomach and duodenum, and can also be regarded as more dangerous. However, there are no proven-effective therapies for NSAID-enteropathy, and detection remains a challenge, particularly because of the poor correlation between tissue injury and symptoms. Moreover, recent studies suggest that commonly used drugs for protecting the upper gastrointestinal tract (i.e., proton pump inhibitors) can significantly worsen NSAID-induced damage in the small intestine. The pathogenesis of NSAID-enteropathy is complex, but studies in animal models are shedding light on the key factors that contribute to ulceration and bleeding, and are providing clues to the development of effective therapies and prevention strategies. Novel NSAIDs that do not cause small intestinal damage in animal models offer hope for a solution to this serious adverse effect of one of the most widely used classes of drugs.

Dual role of serotonin in the pathogenesis of indomethacin-induced small intestinal ulceration: pro-ulcerogenic action via 5-HT3 receptors and anti-ulcerogenic action via 5-HT4 receptors

Serotonin (5-HT) exerts multiple physiological functions not only in the central and peripheral nervous systems but also in the gastrointestinal tract, and these multiple functions are accounted for by a variety of 5-HT receptor subtypes. We investigated the role of 5-HT in the pathogenesis of indomethacin-induced intestinal lesions in mice, in relation to 5-HT receptor subtypes. A single oral administration of indomethacin (10 mg/kg) provoked damage in the small intestine of mice 24 h later, and this response was prevented by pretreatment with p-chlorophenylalanine (a 5-HT synthesis inhibitor). The administration of 5-HT3 receptor antagonists, such as ondansetron and ramosetron, dose-dependently reduced the severity of the intestinal lesions, whereas a high dose of GR113808 (a 5-HT4 receptor antagonist) significantly aggravated these lesions. In contrast, NAN-190 (a 5-HT1 receptor antagonist), ketanserin (a 5-HT2 receptor antagonist), and SB269970 (a 5-HT7 receptor antagonist) had no effect on these lesions. Mosapride (a 5-HT4 receptor agonist) significantly reduced the severity of indomethacin-induced intestinal lesions, and this protective effect was totally prevented by either GR113808 or methyllycaconitine (an α7-nicotinic acetylcholine receptor antagonist). Indomethacin increased the activity of myeloperoxidase and the expression of inducible nitric oxide synthase, inflammatory cytokines, and chemokines in the small intestine; these responses were significantly attenuated by ondansetron and mosapride. These findings suggest that endogenous 5-HT exerts a dual role in the pathogenesis of indomethacin-induced intestinal lesions: pro-ulcerogenic action via 5-HT3 receptors and anti-ulcerogenic action via 5-HT4 receptors, and the latter effect via 5-HT4 receptors may be mediated by activation of α7-nicotinic acetylcholine receptors.

Effect of mosapride on prednisolone-induced gastric mucosal injury and gastric-emptying disorder in dog

Previous report demonstrated that prokinetic agent mosapride has anti-ulcerogenic action in rat-indomethacin gastric mucosal injury model. Here, we assessed the prophylactic effect of mosapride on gastric mucosal injury and emptying disorder induced by prednisolone in dogs. Crossover study design was employed. Six healthy beagles were administered prednisolone alone (2 mg/kg, twice a day [BID] subcutaneously) and prednisolone with mosapride (1 mg/kg, BID, orally), followed by an interval of at least 6 weeks. In each treatment, gastric mucosal injury was scored endoscopically according to the modified Lanza scale, and gastric emptying was assessed with (13)C-octanoic acid breath test. The incidence of gastrointestinal adverse events was also investigated. Coadministration of mosapride with prednisolone significantly (P<0.05) reduced the gastric mucosal injury score (mean ± SD, 17.67 ± 6.96), compared with that of prednisolone treatment alone (25.50 ± 13.03). Prednisolone treatment delayed the half-emptying time (184 ± 45 min) compared with that of controls (137 ± 19 min), and coadministration of mosapride improved this gastric-emptying delay (143 ± 29 min). Furthermore, the incidence of the gastrointestinal adverse event vomiting became less frequent upon coadministration with mosapride. In addition to its prokinetic action, our study suggests that mosapride has an anti-ulcerogenic action in dogs. The use of mosapride in combination with prednisolone is effective for attenuating prednisolone-induced gastrointestinal adverse events.