Hapten-induced model of chronic inflammation and ulceration in the rat colon

Homocysteine promotes intestinal fibrosis in rats with trinitrobenzene sulfonic acid-induced colitis

BACKGROUND AND AIM

Previous studies have revealed significantly increased levels of plasma and mucosal homocysteine (Hcy) in patients with Crohn's disease (CD); however, whether Hcy is involved in intestinal fibrosis of CD remains unclear. This study aimed to investigate the effects of Hcy on intestinal fibrosis in TNBS/ethanol-induced colitis and to elucidate its potential mechanisms.

METHODS

Sprague-Dawley rats were divided into 4 groups: normal control, normal + Hcy injection, TNBS model and TNBS model + Hcy injection. Hyperhomocysteinemia was induced by subcutaneous injection of Hcy. DAI, CMDI and HI were calculated to evaluate the severity of colitis. Masson trichrome staining was performed to assess the severity of fibrosis. The plasma and mucosal levels of Hcy were measured by HPLC-FD. The levels of IL-1β, IL-6, TNF-α, TGF-β1, CTGF, MMP-2,9 and collagen I, III in the colon were determined by ELISA, and the mRNA expressions of TGF-β1, MMP-2,9 and TIMP-1 were detected by RT-PCR.

RESULTS

Hcy was found to increase the scores of DAI, CMDI and HI; levels of IL-1β, Il-6, TNF-α, TGF-β1, CTGF, MMP-2,9 and collagen I, III; and mRNA expressions of TGF-β1, MMP-2,9 and TIMP-1 in colonic tissue of rats with TNBS/ethanol-induced colitis.

CONCLUSIONS

Hcy promotes intestinal fibrosis in rats with TNBS/ethanol-induced colitis, the underlying mechanisms of which may be attributed to its effects of increasing inflammatory damage, promoting the expression of profibrogenic cytokines and influencing MMPs/TIMPs balance.

Comparison of selective and non selective cyclo-oxygenase 2 inhibitors in experimental colitis exacerbation: role of leukotriene B4 and superoxide dismutase

CONTEXT

Nonsteroidal anti-inflammatory drugs are considered one of the most important causes of reactivation of inflammatory bowel disease. With regard to selective cyclo-oxygenase 2 inhibitors, the results are controversial in experimental colitis as well as in human studies.

OBJECTIVES

The aim this study is to compare nonsteroidal anti-inflammatory drugs effects, selective and non selective cyclo-oxygenase 2 inhibitors, in experimental colitis and contribute to the understanding of the mechanisms which nonsteroidal anti-inflammatory drugs provoke colitis exacerbation.

METHODS

Six groups of rats: without colitis, with colitis, and colitis treated with celecoxib, ketoprofen, indometacin or diclofenac. Survival rates, hemoglobin, plasmatic albumin, colonic tissue of interleukin-1ß, interleukin-6, tumor necrosis factor alpha, prostaglandin E2, catalase, superoxide dismutase, thiobarbituric acid-reactive substances, chemiluminescence induced by tert-butil hydroperoxides, and tissue and plasmatic leukotriene B4 were determined.

RESULTS

The groups treated with diclofenac or indometacin presented lower survival rates, hemoglobin and albumin, higher tissue and plasmatic leukotriene B4 and tissue superoxide dismutase than the group treated with celecoxib. Ketoprofen presented an intermediary behavior between diclofenac/indometacin and celecoxib, concerning to survival rate and albumin. The groups without colitis, with colitis and with colitis treated with celecoxib showed leukotriene B4 and superoxide dismutase lower levels than the groups treated with nonselective cyclo-oxygenase 2 inhibitors.

CONCLUSIONS

Diclofenac and indometacin presented the highest degree of induced colitis exacerbation with nonsteroidal anti-inflammatory drugs, celecoxib did not show colitis exacerbation, and ketoprofen presented an intermediary behavior between diclofenac/indometacin and celecoxib. These results suggest that leukotriene B4 and superoxide dismutase can be involved in the exacerbation of experimental colitis by nonselective nonsteroidal anti-inflammatory drugs.

Lipophilic modification enhances anti-colitic properties of rosmarinic acid by potentiating its HIF-prolyl hydroxylases inhibitory activity

Inhibition of hypoxia inducible factor-prolyl hydroxylase-2 (HPH), leading to activation of hypoxia inducible factor (HIF)-1 is a potential therapeutic strategy for the treatment of colitis. Rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid is a naturally occurring polyphenolic compound with two catechols, a or inhibition of HPH. To improve accessibility of highly hydrophilic RA to HPH, an intracellular target, RA was chemically modified to decrease hydrophilicity. Of the less-hydrophilic derivatives, rosmarinic acid methyl ester (RAME) most potently inhibited HPH. Accordingly, RAME prevented hydroxylation of HIF-1α and consequently stabilized HIF-1α protein in cells. RAME inhibition of HPH and induction of HIF-1α were diminished by elevated doses of the required factors of HPH, 2-ketoglutarate and ascorbate. RAME induction of HIF-1α led to activation of an ulcer healing pathway, HIF-1-vascular endothelial growth factor (VEGF), in human colon carcinoma cells. RAME administered rectally ameliorated TNBS-induced rat colitis and substantially decreased the levels of pro-inflammatory mediators in the inflamed colonic tissue. In parallel with the cellular effects of RAME, RAME up-regulated HIF-1α and VEGF in the inflamed colonic tissue. Thus, lipophilic modification of RA improves its ability to inhibit HPH, leading to activation of the HIF-1-VEGF pathway. RAME, a lipophilic RA derivative, may exert anti-colitic effects via activation of the ulcer healing pathway.

Alterations of colonic contractility in an interleukin-10 knockout mouse model of inflammatory bowel disease

Background/Aims

Inflammatory bowel disease is commonly accompanied by colonic dysmotility and causes changes in intestinal smooth muscle contractility. In this study, colonic smooth muscle contractility in a chronic inflammatory condition was investigated using smooth muscle tissues prepared from interleukin-10 knockout (IL-10^−/−) mice.

Methods

Prepared smooth muscle sections were placed in an organ bath system. Cholinergic and nitrergic neuronal responses were observed using carbachol and electrical field stimulation with L-NG-nitroarginine methyl ester (L-NAME). The expression of interstitial cells of Cajal (ICC) networks, muscarinic receptors, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) was observed via immunofluorescent staining.

Results

The spontaneous contractility and expression of ICC networks in the proximal and distal colon was significantly decreased in IL-10^−/− mice compared to IL-10^+/+ mice. The contractility in response to carbachol was significantly decreased in the proximal colon of IL-10^−/− mice compared to IL-10^+/+ mice, but no significant difference was found in the distal colon. In addition, the expression of muscarinic receptor type 2 was reduced in the proximal colon of IL-10^−/− mice. The nictric oxide-mediated relaxation after electrical field stimulation was significantly decreased in the proximal and distal colon of IL-10^−/− mice. In inflamed colon, the expression of nNOS decreased, whereas the expression of iNOS increased.

Conclusions

These results suggest that damage to the ICC network and NOS system in the proximal and distal colon, as well as damage to the smooth muscle cholinergic receptor in the proximal colon may play an important role in the dysmotility of the inflamed colon.

Anti-inflammatory Effects of Flavonoids on TNBS-induced Colitis of Rats

It has been shown that the extracts including eupatilin and quercetin-3-β-D-glucuronopyranoside had mucoprotective effects on the esophagus and stomach through their antioxidant activities. This study was designed to investigate the anti-inflammatory effect of these flavonoid compounds in an animal model of inflammatory bowel disease induced by 2,4,6-trinitrobenzene sulfonic acid. Experimental colitis was induced by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid. Extracts including eupatilin or quercetin-3-β-D-glucuronopyranoside were orally administered to animals 48, 24, and 1 h prior to the induction of colitis and then again 24 h later. The animals were sacrificed 48 h after by 2,4,6-trinitrobenzene sulfonic acid treatment and the macroscopic appearance of the colonic lesions was scored in a blinded manner on a scale of 1 to 10. The inflammatory response to colitis induction was assessed by measuring myeloperoxidase activity, nitric oxide production, tumor necrosis factor-α expression, total glutathione levels, and malondialdehyde concentrations in the colon. The results indicated that extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside dose-dependently improved the morphology of the lesions induced by 2,4,6-trinitrobenzene sulfonic acid and reduced the ulcer index accordingly. In addition, rats receiving extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside showed significantly decreased levels of mucosal myeloperoxidase activity, nitric oxide production, tumor necrosis factor-α expression, and malondialdehyde levels, and increased total glutathione levels. Extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside ameliorated the inflammatory response and colonic injury in acute colitis by decreasing oxidative stress and neutrophil activation. Extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside may inhibit acute colitis.

An integrated assessment of histopathological changes of the enteric neuromuscular compartment in experimental colitis

Bowel inflammatory fibrosis has been largely investigated, but an integrated assessment of remodelling in inflamed colon is lacking. This study evaluated tissue and cellular changes occurring in colonic wall upon induction of colitis, with a focus on neuromuscular compartment. Colitis was elicited in rats by 2,4-dinitrobenzenesulfonic acid (DNBS). After 6 and 21 days, the following parameters were assessed on paraffin sections from colonic samples: tissue injury and inflammatory infiltration by histology; collagen and elastic fibres by histochemistry; HuC/D, glial fibrillar acidic protein (GFAP), proliferating cell nuclear antigen (PCNA), nestin, substance P (SP), von Willebrand factor, c-Kit and transmembrane 16A/Anoctamin1 (TMEM16A/ANO1) by immunohistochemistry. TMEM16A/ANO1 was also examined in isolated colonic smooth muscle cells (ICSMCs). On day 6, inflammatory alterations and fibrosis were present in DNBS-treated rats; colonic wall thickening and fibrotic remodelling were evident on day 21. Colitis was associated with both an increase in collagen fibres and a decrease in elastic fibres. Moreover, the neuromuscular compartment of inflamed colon displayed a significant decrease in neuron density and increase in GFAP/PCNA-positive glia of myenteric ganglia, enhanced expression of neural SP, blood vessel remodelling, reduced c-Kit- and TMEM16A/ANO1-positive interstitial cells of Cajal (ICCs), as well as an increase in TMEM16A/ANO1 expression in muscle tissues and ICSMCs. The present findings provide an integrated view of the inflammatory and fibrotic processes occurring in the colonic neuromuscular compartment of rats with DNBS-induced colitis. These morphological alterations may represent a suitable basis for understanding early pathophysiological events related to bowel inflammatory fibrosis.

Comparison of noncontrast MRI magnetization transfer and T2 -Weighted signal intensity ratios for detection of bowel wall fibrosis in a Crohn's disease animal model

PURPOSE

To compare the abilities of magnetization transfer magnetic resonance imaging (MT-MRI) and T2 -weighted signal intensity (T2 WSI) ratios to detect intestinal fibrosis in a Crohn's disease animal model.

MATERIALS AND METHODS

Ten rats ("Group 1") received one trinitrobenzenesulfonic acid enema to induce acute colonic inflammation, while 10 additional animals ("Group 2") received multiple enemas to induce colonic inflammation and fibrosis. Gradient recalled-echo MT-MRI (5 and 10 kHz off-resonance) and T2 -weighted spin-echo imaging were performed 2 days after the last enema. MT ratios (MTR) and T2 WSI ratios were calculated in the area of greatest colonic thickening. Bowel wall MTR, bowel wall MTR normalized to paraspinous muscle MTR ("normalized MTR"), and T2 WSI ratios were compared between animal groups using Student's t-test.

RESULTS

At 10 kHz off-resonance, mean bowel wall MTR for Group 1 was 24.8 ± 3.1% vs. 30.3 ± 3.2% for Group 2 (P = 0.001). Mean normalized MTR was 0.45 ± 0.05 for Group 1 and 0.58 ± 0.08 for Group 2 (P = 0.0003). At 5 kHz off-resonance, mean bowel wall MTR for Group 1 was 34.7 ± 5.2% vs. 40.3 ± 3.6% for Group 2 (P = 0.015). Mean normalized MTR was 0.53 ± 0.08 for Group 1 and 0.64 ± 0.07 for Group 2 (P = 0.003). Mean T2 WSI ratio was 5.32 ± 0.98 for Group 1 and 3.01 ± 0.66 for group 2 (P < 0.0001). Mean T2 WSI ratio/MTR (10 kHz off-resonance) was 12.06 ± 2.70 for Group 1 and 5.22 ± 1.29 for Group 2 (P < 0.0001), with an ROC c-statistic of 0.98.

CONCLUSION

MTR and T2 WSI ratios detect bowel wall fibrosis in a Crohn's disease animal model.

Modulation of nuclear factor-κB-mediated pro-inflammatory response is associated with exogenous administration of bone marrow-derived mesenchymal stem cells for treatment of experimental colitis

Mesenchymal stem cells (MSCs) inhibit the immune response in vitro and prevent the induction of disease in certain experimental models. As a result, MSC‑mediated therapy is a rapidly growing field of research. However, the efficacy of MSCs in the treatment of inflammatory bowel disease (IBD) has remained to be determined. In the present study, rats with 2,4,6‑trinitrobenzene sulfonic acid (TNBS)‑induced colitis were injected with prepared MSCs (1x106) into the tail vein. Two weeks following intravenous MSC administration, the concentration of tumor necrosis factor‑α (TNF‑α) in the serum was measured by an ELISA. The protein expression of nuclear factor‑κB (NF‑κBp65) in the colonic mucosa was assessed by western blot analysis. mRNA expression of TNF‑α and NF‑κBp65 was determined by reverse‑transcription quantitative polymerase chain reaction. MSCs were shown to exert an immunomodulatory effect on TNBS‑induced colitis and may be of use in the treatment of IBD. In addition, modulation of the NF‑κB‑mediated pro‑inflammatory response may contribute to the underlying mechanism by which MSCs ameliorate the clinical and histological changes associated with IBD.

Pelvic organ cross-sensitization to enhance bladder and urethral pain behaviors in rats with experimental colitis

Neural cross-sensitization has been postulated as a mechanism underlying overlaps of chronic pelvic pain disorders such as bladder pain syndrome/interstitial cystitis (BPS/IC) and irritable bowel syndrome (IBS). Animals with experimental colitis have been used to study the underlying mechanisms for overlapped pelvic pain symptoms, and shown to exhibit bladder overactivity evidenced by frequent voiding; however, it has not directly been evaluated whether pain sensation derived from the lower urinary tract is enhanced in colitis models. Also, the cross-sensitization between the colon and urethra has not been studied previously. In the present study, we therefore investigated pain behaviors induced by nociceptive stimuli in the lower urinary tract and the involvement of C-fiber afferent pathways using rats with colitis induced by intracolonic application of 2,4,6-trinitrobenzenesulfonic acid (TNBS). In TNBS-induced colitis rats at 10 days, intravesical application of resiniferatoxin (RTx) induced a significantly greater number of episodes of both licking and freezing behaviors, which were reduced by capsaicin-sensitive C-fiber afferent desensitization. Histochemical studies using fluorescent dye tracers injected into the colon, bladder or urethra showed that dichotomized afferent neurons comprised 6.9-14.5% of L1, L6 and S1 dorsal root ganglion (DRG) neurons innervating the colon or the lower urinary tract. Transient receptor potential vanilloid 1 (TRPV1) mRNA expression was significantly increased in, the bladder, urethra and S1 DRG in colitis rats. An increase in myeloperoxidase (MPO) activity was found in the colon, but not in the bladder or urethra after intracolonic TNBS treatment. These results indicate that TNBS-induced colitis increased pain sensitivity in the bladder and urethra via activation of C-fiber afferent pathways due to colon-to-bladder and colon-to-urethral cross-sensitization, suggesting the contribution of pelvic organ cross-sensitization mechanisms to overlapped pain symptoms in BPS/IC and IBS.

Baicalin attenuates TNBS-induced colitis in rats by modulating the Th17/Treg paradigm

Baicalin, a flavonoid, has a wide range of pharmacological properties, including immunomodulation. The objective of this study was to investigate the effect of baicalin on the balance of T helper 17 (Th17) and regulatory T (Treg) cells in a colitis model. The rat colitis model was induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). Baicalin (10 ml/kg, each) or mesalazine (positive control) was then administered orally for 7 days. Inflammatory and immunological responses were evaluated by pathology, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, western blot analysis, and flow cytometry. Our study showed that baicalin not only significantly attenuated TNBS-induced colitis by reducing the disease activity index as well as macroscopic and microscopic scores, but it also improved the weight loss and shortening of the colon. Baicalin treatment also induced a significant decrease in the levels of inflammatory mediators, including the myeloperoxidase activity, the levels of tumor necrosis factor α, IL-1β, and Th1-related cytokines IL-12 and IFN-γ. Furthermore, the beneficial effects of baicalin seem to be associated with regulation of the Th17 and Treg paradigm. We found that administration of baicalin significantly downregulated the number of Th17 cells and the levels of Th17-related cytokines (IL-17 and IL-6) and retinoic acid receptor-related orphan receptor γt. In contrast, there was an increase in Treg cells numbers, Treg-related cytokines transforming growth factor-β and IL-10, and forkhead box P3. Our results suggest that the anti-inflammatory effect of baicalin may be linked to modulation of the balance between Th17 and Treg cells in TNBS-induced ulcerative colitis.

Total glucosides of peony attenuates 2,4,6-trinitrobenzene sulfonic acid/ethanol-induced colitis in rats through adjustment of TH1/TH2 cytokines polarization

The present study is to investigate effects of total glucosides of peony (TGP) on 2,4,6-trinitrobenzene sulfonic acid (TNBS)/ethanol-induced colitis in rats and to explore potential clinical use of TGP for treatment of inflammatory bowel disease. Sixty Sprague-Dawley rats were randomly grouped into normal controls, model controls, sulfasalazine (SASP) controls (100 mg/kg/day), and low, medium, and high-dose TGP groups (25, 50, and 100 mg/kg/day, respectively). 24 h following colonic instillation of TNBS, TGP, and SASP were given by gastric gavage three times a day for 7 days. Disease activity index (DAI), colon macroscopic damage index (CMDI), histopathological score (HPS), and myeloperoxidase (MPO) activity were evaluated. Levels of serum TNF-α, IL-1β, and IL-10 were measured by ELISA, and expression of TNF-α, IL-1β, and IL-10 mRNA and protein in colonic tissues was detected by RT-PCR and western blot, respectively. Compared with rats in the model controls, TGP (50 or 100 mg/kg/day)-treated rats with TNBS/ethanol-induced colitis showed significant improvements of DAI, CMDI, HPS, and MPO activity. Moreover, administration of TGP (50 or 100 mg/kg/day) decreased the up-regulated levels of serum TNF-α and IL-1β, and expression of TNF-α and IL-1β mRNA and protein in colonic tissues, and increased the serum IL-10 and colonic IL-10 mRNA and protein level. And there was no significant difference compared with administration of SASP (P > 0.05). TGP attenuates TNBS/ethanol-induced colitis in rats and its efficacy is similar to SASP, the potential mechanism might be related to the adjustment of Th1/Th2 cytokines polarization by decreasing pro-inflammatory cytokine TNF-α and IL-1β, and increasing anti-inflammatory cytokine IL-10.

Enzyme/pH dual sensitive polymeric nanoparticles for targeted drug delivery to the inflamed colon

Novel nanoparticles whose drug release profiles are controlled by both enzyme and pH were prepared for the colon-specific drug delivery using a polymeric mixture of enzyme-sensitive azo-polyurethane and pH-sensitive Eudragit S100 (ES-Azo.pu). The enzyme/pH dual sensitive nanoparticles were designed to release a drug based on a two-fold approach which specifically aimed to target drug delivery to the inflamed colon while preventing the burst release of drugs in the stomach and small intestine. Single pH-sensitive (ES) and dual sensitive (ES-Azo.pu) nanoparticles were prepared using an oil-in-water emulsion solvent evaporation method and coumarin-6 (C-6) was used as a model drug. The successful formation of ES and ES-azo.pu nanoparticles that have 214 nm and 244 nm in mean particle size, respectively, was confirmed by scanning electron microscopy and qNano. ES nanoparticles showed almost 100% of burst drug release at pH 7.4, whereas ES-Azo.pu nanoparticles prevented the burst drug release at pH 7.4, followed by a sustained release phase thereafter. Furthermore, ES-Azo.pu nanoparticles exhibited enzyme-triggered drug release in the presence of rat cecal contents obtained from a rat model of colitis. An in vivo localization study in rat gastrointestinal tract demonstrated that ES-Azo.pu nanoparticles were selectively distributed in the inflamed colon, showing 5.5-fold higher C-6 than ES nanoparticles. In conclusion, the enzyme/pH dual sensitive nanoparticles presented in this study can serve as a promising strategy for colon-specific drug delivery against inflammatory bowel disease and other colon disorders.

The anti-inflammation effect of baicalin on experimental colitis through inhibiting TLR4/NF-κB pathway activation

BACKGROUND

Baicalin holds a protective effect on inflammatory responses in several diseases. However, its molecular mechanism of anti-inflammatory activity on ulcerative colitis (UC) remains unknown. The present study was conducted to verify whether the anti-inflammation effect of baicalin on experimental colitis is via inhibiting TLR4/NF-κB pathway activation.

METHODS

The inflammatory response in RAW264.7 cells was induced by LPS and in rats by intrarectal administration of TNBS. Western blot analysis was carried out to examine toll-like receptor 4 (TLR4), NF-κB, p-NF-κB p65, IκB and p-IκB protein expressions in cells. Furthermore, intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), cyclo-oxygenase-2 (Cox-2), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 levels in cell supernatant and rat serum were detected by appropriate kits. An immunohistochemical assay was applied to examine TNF-α and IL-1β protein expression in colon tissues and TLR4 and p-NF-κB p65 protein expressions in RAW264.7 cells.

RESULTS

Baicalin ameliorates the considered inflammatory symptoms of induced colitis. It could also down-regulate pro-inflammatory mediators in the colon mucosa. The decline in the production of pro-inflammatory cytokines was correlated with the decrease in mucosal TLR4 protein expression. The expression of p-NF-κB p65 protein was significantly decreased, which correlated with a similar decrease in p-IκB protein. Consistent with the in vivo results, baicalin blocked LPS-stimulated nuclear translocation of p-NF-κB p65 in mouse macrophage RAW264.7 cells.

CONCLUSIONS

The present study indicates for the first time that the mechanism for baicalin on abrogating experimental colitis was targeted inhibition of the TLR4/NF-κB pathway activation.

Effectiveness of sildenafil and U-74389G in a rat model of colitis

BACKGROUND

Crohn disease is still incurable. Compounds with anti-inflammatory and/or antioxidative effects are tested in various preclinical models of the disease. Our aim was to investigate the effects of sildenafil and lazaroid U-74389G in an experimental rat model of trinitrobenzenesulfonic acid-induced colitis.

MATERIALS AND METHODS

Trinitrobenzenesulfonic acid was instilled into the colon of all male Wistar rats except for the rats belonging to the first group. For 6 days, the animals in group 3 were administered daily sildenafil orally, the rats in group 4 were administered daily U-74389G intravenously, and the rats in group 5 were coadministered daily sildenafil orally and intravenous U-74389G. The rats in groups 1 and 2 were not administered any treatment. During the study, the weights were recorded as a marker of clinical condition. The colon damage was evaluated using macroscopic colon mucosal damage index (CMDI), microscopic (Geboes score), and biochemical methods (tissue tumor necrosis factor [TNF]-α and malondialdehyde [MDA]).

RESULTS

Sildenafil reduced TNF-α tissue levels and increased body weight. U-74389G reduced TNF-α, the macroscopic index of mucosal damage score (CMDI) and increased body weight. The combined treatment with sildenafil and U-74389G reduced tissue levels of both TNF-α and MDA, lowered CMDI and microscopic Geboes score, and increased body weight.

CONCLUSIONS

U-74389G demonstrated a significant anti-inflammatory activity related to its ability to reduce colonic TNF-α, CMDI score, and improve weight change. We confirmed that sildenafil has anti-inflammatory capacity by reducing colonic TNF-α and by improving body weight. Finally, the combined treatment showed superior effects by reducing colonic TNF-α, colonic MDA, CMDI score, Geboes score, and by improving weight.

Preventive effect of the microalga Chlamydomonas debaryana on the acute phase of experimental colitis in rats

Inflammatory bowel diseases (IBD) are characterised by chronic uncontrolled inflammation of intestinal mucosa. Diet and nutritional factors have emerged as possible interventions for IBD. Microalgae are rich sources of n-3 PUFA and derived oxylipins. Oxylipins are lipid mediators involved in the resolution of many inflammatory disorders. The aim of the present study was to investigate the effects of the oxylipin-containing biomass of the microalga Chlamydomonas debaryana and its major oxylipin constituent, (9Z,11E,13S,15Z)-13-hydroxyoctadeca-9,11,15-trienoic acid ((13S)-HOTE), on acute 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats. Lyophilised microalgal biomass and (13S)-HOTE were administered by oral route 48, 24 and 1 h before the induction of colitis and 24 h later, and the rats were killed after 48 h. The treatment with the lyophilised microalga and (13S)-HOTE improved body-weight loss and colon shortening, as well as attenuated the extent of colonic damage and increased mucus production. Cellular neutrophil infiltration, with the subsequent increase in myeloperoxidase levels induced by TNBS, were also reduced after the administration of the lyophilised microalga or (13S)-HOTE. The anti-inflammatory effects of these treatments were confirmed by the inhibition of colonic TNF-α production. Moreover, lyophilised microalga or (13S)-HOTE down-regulated cyclo-oxygenase-2 and inducible nitric oxide synthase expression. The present study was the first to show the prophylactic effects of a lyophilised biomass sample of the microalga C. debaryana and the oxylipin (13S)-HOTE on TNBS-induced acute colitis in rats. Our findings suggest that the microalga C. debaryana or derived oxylipins could be used as nutraceuticals in the treatment of the active phase of IBD.

A review on chemical-induced inflammatory bowel disease models in rodents

Ulcerative colitis and Crohn's disease are a set of chronic, idiopathic, immunological and relapsing inflammatory disorders of the gastrointestinal tract referred to as inflammatory bowel disorder (IBD). Although the etiological factors involved in the perpetuation of IBD remain uncertain, development of various animal models provides new insights to unveil the onset and the progression of IBD. Various chemical-induced colitis models are widely used on laboratory scale. Furthermore, these models closely mimic morphological, histopathological and symptomatical features of human IBD. Among the chemical-induced colitis models, trinitrobenzene sulfonic acid (TNBS)-induced colitis, oxazolone induced-colitis and dextran sulphate sodium (DSS)-induced colitis models are most widely used. TNBS elicits Th-1 driven immune response, whereas oxazolone predominantly exhibits immune response of Th-2 phenotype. DSS-induced colitis model also induces changes in Th-1/Th-2 cytokine profile. The present review discusses the methodology and rationale of using various chemical-induced colitis models for evaluating the pathogenesis of IBD.

Inhibition of the interleukin-23/interleukin-17 pathway by anti-interleukin-23p19 monoclonal antibody attenuates 2,4,6-trinitrobenzene sulfonic acid-induced Crohn's disease in rats

The interleukin (IL)-23/IL-17 pathway is considered to be important in the pathogenesis of Crohn's disease (CD). The present study aimed to evaluate the effects of targeting the IL‑23/IL‑17 pathway using the anti-IL-23p19 monoclonal antibody (mAb) on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced CD rats. A total of 60 Sprague-Dawley rats were randomly divided into a control group, model group and an anti-IL-23p19 mAb treatment group (administered intramuscularly every week at a dose of 1 ml/mg). Disease activity index (DAI), colon macroscopic damage index (CMDI) and tissue damage index (TDI) were then evaluated. The mRNA expression of IL-23p19, p40 (IL-23/12), retinoic acid-related orphan receptor-γt (ROR‑γt) and IL‑17 in colonic tissues were detected by reverse transcription‑polymerase chain reaction and levels of serum IL-23p19, p40, ROR-γt and IL-17 were measured using an enzyme‑linked immunosorbent assay. Anti‑IL‑23p19 mAb was found to effectively attenuate colonic inflammation demonstrated by reduced DAI, CMDI and TDI scores, improvement in pathological evaluation and downregulation of expression levels of IL‑23p19, p40 (IL-23/12), ROR-γt and the downstream proinflammatory cytokine, IL-17. Anti-IL-23p19 mAb attenuated TNBS-induced CD in model rats. The possible underlying mechanisms may be associated with inhibition of the IL-23/IL-17 pathway by inhibiting the expression of IL‑23p19 and downregulating the downstream proinflammatory cytokine IL‑17. Targeting the IL-23/IL-17 pathway may be a relevant and realistic therapeutic approach for the development of additive and alternative treatments to the biologics currently available in the treatment of CD.

Magnetic resonance colonography for fibrosis assessment in rats with chronic colitis

Background

Magnetic resonance colonography (MRC) has been developed to assess inflammatory bowel diseases. We aimed to assess the feasibility of MRC in rats with TNBS-induced chronic colitis and to confront imaging results with fibrosis and stenosing features of the model.

Materials and Methods

Chronic colitis was induced in 12 rats by weekly intra-rectal injection of increasing doses of TNBS for 6 weeks, while 8 control rats received the vehicle. At week 7, MRC was performed. Fibrosis scores were assessed and fibrosis mediators measured.

Results

Chronic colitis was associated with significant body weight loss (p<0.0001) and higher colon weight/length compared to controls (p = 0.0004). Fibrosis mediators and histological scores were significantly higher in rats with TNBS than in controls: α-SMA expression (0.9 versus 0.61, p = 0.0311) and fibrosis score (p = 0.0308). Colon wall thickness was higher in rats with TNBS than in controls: maximal thickness (2.38 versus 0.74 mm, p<0.0001) and minimal thickness (1.33 versus 0.48 mm, p<0.0001). Wall signal intensity on T2w images was higher in rats with TNBS than in controls (9040 versus 6192, p = 0.0101) and correlated with fibrosis score (r = 0.5214; p = 0.04). Luminal narrowing was higher in rats with TNBS (50.08 versus 10.33%, p<0.0001) and correlated with α-SMA expression (r = 0.5618; p = 0.01). Stenosis was observed in 7/9 rats with TNBS and in no controls (p = 0.0053).

Conclusions

MRC is feasible and easily distinguishes rats with colitis from controls. MRC signs correlated with fibrosis parameters. MRC evaluation may be part of a new anti-fibrosis drug assessment in experimental models of chronic colitis.

Preclinical gastrointestinal prokinetic efficacy and endocrine effects of the ghrelin mimetic RM-131

AIMS

The 28 amino acid hormone ghrelin, the natural ligand for the growth hormone secretagogue, or ghrelin receptor (GHR), has diverse physiological functions, including a possible role as a gastrointestinal prokinetic. The synthetic ghrelin mimetic RM-131 is in Phase II clinical trials for treatment of diabetic gastroparesis and other gastrointestinal (GI) disorders. We aimed to determine the relative potency of RM-131, when compared to other GI ghrelin mimetics, to predict efficacy and determine the role of RM-131 in models of inflammatory bowel disease.

MAIN METHODS

We evaluated and compared ghrelin, RM-131 and other synthetic ghrelin mimetics for their prokinetic potency in models of gastrointestinal disorders in the rat and we evaluated the endocrine (rats and dogs) and anti-inflammatory effects (mice) of the ghrelin mimetic RM-131.

KEY FINDINGS

The pentapeptide RM-131 increased gastric emptying in rodent models of ileus. RM-131 is about 100-fold more potent than human ghrelin and is 600 to 1800-fold more potent, when compared to several investigational ghrelin mimetics tested in clinical trials. RM-131 has anti-inflammatory effects and significantly increases survival and reduces macroscopic markers of tissue damage in a TNBS model of inflammatory bowel disease. RM-131 treatment shows a transient increase in growth hormone levels in Beagle dogs and rats, returning to baseline upon chronic treatment. Significant effects on glucose and insulin are not observed in chronic studies.

SIGNIFICANCE

RM-131's potency, efficacy and endocrine profile, are promising attributes for the treatment of diverse functional gastrointestinal disorders in humans.

Telmisartan attenuates colon inflammation, oxidative perturbations and apoptosis in a rat model of experimental inflammatory bowel disease

Accumulating evidence has indicated the implication of angiotensin II in the pathogenesis of inflammatory bowel diseases (IBD) via its proinflammatory features. Telmisartan (TLM) is an angiotensin II receptor antagonist with marked anti-inflammatory and antioxidant actions that mediated its cardio-, reno- and hepatoprotective actions. However, its impact on IBD has not been previously explored. Thus, we aimed to investigate the potential alleviating effects of TLM in tri-nitrobenezene sulphonic acid (TNBS)-induced colitis in rats. Pretreatment with TLM (10 mg/kg p.o.) attenuated the severity of colitis as evidenced by decrease of disease activity index (DAI), colon weight/length ratio, macroscopic damage, histopathological findings and leukocyte migration. TLM suppressed the inflammatory response via attenuation of tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂) and myeloperoxidase (MPO) activity as a marker of neutrophil infiltration besides restoration of interleukin-10 (IL-10). TLM also suppressed mRNA and protein expression of nuclear factor kappa B (NF-κB) p65 and mRNA of cyclo-oxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proinflammatory genes with concomitant upregulation of PPAR-γ. The alleviation of TLM to colon injury was also associated with inhibition of oxidative stress as evidenced by suppression of lipid peroxides and nitric oxide (NO) besides boosting glutathione (GSH), total anti-oxidant capacity (TAC) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). With respect to apoptosis, TLM downregulated the increased mRNA, protein expression and activity of caspase-3. It also suppressed the elevation of cytochrome c and Bax mRNA besides the upregulation of Bcl-2. Together, these findings highlight evidences for the beneficial effects of TLM in IBD which are mediated through modulation of colonic inflammation, oxidative stress and apoptosis.

Camel's milk ameliorates TNBS-induced colitis in rats via downregulation of inflammatory cytokines and oxidative stress

Current treatment strategies for inflammatory bowel diseases (IBD) are associated with several adverse effects, and thus, the search for effective agents with minimal side effects merits attention. Camel's milk (CM) is endowed with antioxidant/anti-inflammatory features and has been reported to protect against diabetes and hepatic injury, however, its effects on IBD have not been previously explored. In the current study, we aimed to investigate the potential alleviating effects of CM against TNBS-induced colitis in rats. CM (10 ml/kg b.i.d. by oral gavage) effectively suppressed the severity of colon injury as evidenced by amelioration of macroscopic damage, colon weight/length ratio, histopathological alterations, leukocyte influx and myeloperoxidase activity. Administration of CM mitigated the colonic levels of TNF-α and IL-10 cytokines. The attenuation of CM to colon injury was also associated with suppression of oxidative stress via reduction of lipid peroxides and nitric oxide along with boosting the antioxidant defenses through restoration of colon glutathione and total anti-oxidant capacity. In addition, caspases-3 activity, an apoptotic marker, was inhibited. Together, our study highlights evidences for the promising alleviating effects of CM in colitis. Thus, CM may be an interesting complementary approach for the management of IBD.

Urocortin 3 expression at baseline and during inflammation in the colon: corticotropin releasing factor receptors cross-talk

Urocortins (Ucn1-3), members of the corticotropin-releasing factor (CRF) family of neuropeptides, are emerging as potent immunomodulators. Localized, cellular expression of Ucn1 and Ucn2, but not Ucn3, has been demonstrated during inflammation. Here, we investigated the role of Ucn3 in a rat model of Crohn's colitis and the relative contribution of CRF receptors (CRF1 and CRF2) in regulating Ucn3 expression at baseline and during inflammation. Ucn3 mRNA and peptide were ubiquitously expressed throughout the GI tract in naïve rats. Ucn3 immunoreactivity was seen in epithelial cells and myenteric neurons. On day 1 of colitis, Ucn3 mRNA levels decreased by 80% and did not recover to baseline even by day 9. Next, we ascertained pro- or anti-inflammatory actions of Ucn3 during colitis. Surprisingly, unlike observed anti-inflammatory actions of Ucn1, exogenous Ucn3 did not alter histopathological outcomes during colitis and neither did it alter levels of pro-inflammatory cytokines IL-6 and TNF-α. At baseline, colon-specific knockdown of CRF1, but not CRF2 decreased Ucn3 mRNA by 78%, whereas during colitis, Ucn3 mRNA levels increased after CRF1 knockdown. In cultured cells, co-expression of CRF1+CRF2 attenuated Ucn3-stimulated intracellular Ca(2+) peak by 48% as compared to cells expressing CRF2 alone. Phosphorylation of p38 kinase increased by 250% during colitis and was significantly attenuated after Ucn3 administration. Thus, our results suggest that a balanced and coordinated expression of CRF receptors is required for proper regulation of Ucn3 at baseline and during inflammation.

Passiflora edulis peel intake and ulcerative colitis: approaches for prevention and treatment

Inflammatory bowel disease is a chronic relapsing disease that affects millions of people worldwide; its pathogenesis is influenced by genetic, environmental, microbiological, and immunological factors. The aim of this study was to evaluate the effects of short- and long-term Passiflora edulis peel intake on the antioxidant status, microbiota, and short-chain fatty acids formation in rats with 2,4,6-trinitrobenzenesulphonic acid-induced colitis using two "in vivo" experiments: chronic (prevention) and acute (treatment). The colitis damage score was determined using macroscopic and microscopic analyses. In addition, the antioxidant activity in serum and other tissues (liver and colon) was evaluated. Bifidobacteria, lactobacilli, aerobic bacteria and enterobacteria, and the amount of short-chain fatty acids (acetic, butyric, and propionic acids) in cecum content were counted. Differences in the colon damage scores were observed; P. edulis peel intake improved serum antioxidant status. In the treatment protocol, decreased colon lipid peroxidation, a decreased number of aerobic bacteria and enterobacteria, and an improvement in acetic and butyric acid levels in the feces were observed. An improvement in the bifidobacteria and lactobacilli was observed in the prevention protocol. These results suggested that P. edulis peel can modulate microbiota and could be used as source of fiber and polyphenols in the prevention of oxidative stress through the improvement of serum and tissue antioxidant status.

Boswellia serrata has beneficial anti-inflammatory and antioxidant properties in a model of experimental colitis

Ulcerative colitis is an inflammatory disease that involves only the colon and rectum, being characterized by leukocyte infiltrate and superficial ulcers in the intestinal mucosa. To evaluate the anti-inflammatory and antioxidant effects of extract from the Boswellia serrata plant in an experimental rat model of acute ulcerative colitis induced by the administration of acetic acid (AA). An extract of B. serrata (34.2 mg/kg/day) was administered by oral gavage for 2 days before and after the induction of colitis with 4 mL of 4% AA. The anal sphincter pressure in the colitis group showed a significant decrease compared to that of the control groups (p < 0.001). The analysis of the values of lipid peroxidation (LPO) obtained by substances that react with thiobarbituric acid (TBARS) showed a significantly increased LPO in the colitis group compared to the control groups (p < 0.001). The nitric oxide levels and the expression of inducible nitric oxide synthase (iNOS) showed a significant increase in the colitis group compared to control groups (p < 0.01). Both pretreatment and treatment with B. serrata exhibited significantly reduced lipid peroxidation, nitric oxide and iNOS and showed improvements in tissue injury and anal sphincter pressure in animals with ulcerative colitis. The B. serrata extract has protective anti-inflammatory and antioxidant effects that inhibit inflammatory mediators in acute experimental colitis.

Protective effect of hydroalcoholic olive leaf extract on experimental model of colitis in rat: involvement of nitrergic and opioidergic systems

The aim of the present study is to investigate the possible protective effect of dry olive leaf extract (OLE) against acetic acid-induced ulcerative colitis in rats, as well as the probable modulatory effect of nitrergic and opioidergic systems on this protective impact. Olive leaf extract was administered (250, 500 and 750 mg/kg) orally for two successive days, starting from the colitis induction. To assess the involvement of nitrergic and opioidergic systems in the possible protective effect of OLE, L-NG-Nitroarginine Methyl Ester (10 mg/kg) and naltrexone (5 mg/kg) intraperitoneal (i.p.) were applied 30 min before administration of the extract for two successive days, respectively. Colonic status was investigated 48 h following induction through macroscopic, histological and biochemical analyses. Olive leaf extract dose-dependently attenuated acetic acid-provoked chronic intestinal inflammation. The extract significantly reduces the severity of the ulcerative lesions and ameliorated macroscopic and microscopic scores. These observations were accompanied by a significant reduction in the elevated amounts of TNF-α and interlukin-2 markers. Moreover, both systems blockage reversed protective effects of OLE in the rat inflammatory bowel disease model. These finding demonstrated, for the first time, a possible role for nitrergic and opioidergic systems in the aforementioned protective effect, and the extract probably exerted its impact increasing nitric oxide and opioid tones.

Antioxidant and intestinal anti-inflammatory effects of plant-derived coumarin derivatives

BACKGROUND

Coumarins, also known as benzopyrones, are plant-derived products with several pharmacological properties, including antioxidant and anti-inflammatory activities. Based on the wide distribution of coumarin derivatives in plant-based foods and beverages in the human diet, our objective was to evaluate both the antioxidant and intestinal anti-inflammatory activities of six coumarin derivatives of plant origin (scopoletin, scoparone, fraxetin, 4-methyl-umbeliferone, esculin and daphnetin) to verify if potential intestinal anti-inflammatory activity was related to antioxidant properties.

METHODS

Intestinal inflammation was induced by intracolonic instillation of TNBS in rats. The animals were treated with coumarins by oral route. The animals were killed 48 h after colitis induction. The colonic segments were obtained after laparotomy and macroscopic and biochemical parameters (determination of glutathione level and myeloperoxidase and alkaline phosphatase activities) were evaluated. The antioxidant properties of these coumarins were examined by lipid peroxidation and DPPH assays.

RESULTS

Treatment with esculin, scoparone and daphnetin produced the best protective effects. All coumarin derivatives showed antioxidant activity in the DPPH assay, while daphnetin and fraxetin also showed antioxidant activity by inhibiting lipid peroxidation. Coumarins, except 4-methyl-umbeliferone, also showed antioxidant activity through the counteraction of glutathione levels or through the inhibition of myeloperoxidase activity.

DISCUSSION

The intestinal anti-inflammatory activity of coumarin derivatives were related to their antioxidant properties, suggesting that consumption of coumarins and/or foods rich in coumarin derivatives, particularly daphnetin, esculin and scoparone, could prevent intestinal inflammatory disease.

Analgesic effect of minocycline in rat model of inflammation-induced visceral pain

The present study investigates the analgesic effect of minocycline, a semi-synthetic tetracycline antibiotic, in a rat model of inflammation-induced visceral pain. Inflammation was induced in male rats by intracolonic administration of tri-nitrobenzenesulphonic acid (TNBS). Visceral hyperalgesia was assessed by comparing the viscero-motor response (VMR) to graded colorectal distension (CRD) prior and post 7 days after TNBS treatment. Electrophysiology recordings from CRD-sensitive pelvic nerve afferents (PNA) and lumbo-sacral (LS) spinal neurons were performed in naïve and inflamed rats. Colonic inflammation produced visceral hyperalgesia characterized by increase in the VMRs to CRD accompanied with simultaneous activation of microglia in the spinal cord and satellite glial cells (SGCs) in the dorsal root ganglions (DRGs). Selectively inhibiting the glial activation following inflammation by araC (Arabinofuranosyl Cytidine) prevented the development of visceral hyperalgesia. Intrathecal minocycline significantly attenuated the VMR to CRD in inflamed rats, whereas systemic minocycline produced a delayed effect. In electrophysiology experiments, minocycline significantly attenuated the mechanotransduction of CRD-sensitive PNAs and the responses of CRD-sensitive LS spinal neurons in TNBS-treated rats. While the spinal effect of minocycline was observed within 5min of administration, systemic injection of the drug produced a delayed effect (60min) in inflamed rats. Interestingly, minocycline did not exhibit analgesic effect in naïve, non-inflamed rats. The results demonstrate that intrathecal injection of minocycline can effectively attenuate inflammation-induced visceral hyperalgesia. Minocycline might as well act on neuronal targets in the spinal cord of inflamed rats, in addition to the widely reported glial inhibitory action to produce analgesia.

Role of neurokinin 1 receptors in dextran sulfate-induced colitis: studies with gene-deleted mice and the selective receptor antagonist netupitant

OBJECTIVE AND DESIGN

The function of the neurokinin 1 (NK1) receptor was investigated in the DSS-induced mouse colitis model using NK1 receptor-deficient mice and the selective antagonist netupitant.

SUBJECTS

Colitis was induced by oral administration of 20 mg/ml DSS solution for 7 days in C57BL/6 and Tacr1 KO animals (n = 5-7).

TREATMENT

During the induction, one-half of the C57BL/6 and Tacr1 KO group received one daily dose of 6 mg/kg netupitant, administered intraperitoneally, the other half of the group received saline, respectively.

METHODS

Disease activity index (DAI), on the basis of stool consistency, blood and weight loss, was determined over 7 days. Histological evaluation, myeloperoxidase (MPO) measurement, cytokine concentrations and receptor expression analysis were performed on the colon samples.

RESULTS

NK1 receptors are up-regulated in the colon in response to DSS treatment. DSS increased DAI, histopathological scores, BLC, sICAM-1, IFN-γ, IL-16 and JE in wildtype mice, which were significantly reduced in NK1 receptor-deficient ones. NK1 receptor antagonism with netupitant significantly diminished DAI, inflammatory histopathological alterations, BLC, IFN-γ, IL-13 and IL-16 in wildtype mice, but not in the NK1-deficient ones. MPO was similarly elevated and netupitant significantly decreased its activity in both groups.

CONCLUSIONS

NK1 receptor antagonism could be beneficial for colitis via inhibiting different inflammatory mechanisms.

Antidiarrheal and intestinal antiinflammatory activities of a methanolic extract of Qualea parviflora Mart. in experimental models

ETHNOPHARMACOLOGICAL RELEVANCE

An ethnopharmacological survey indicated that the bark from Qualea parviflora Mart. (Vochysiaceae) could be used to treat gastrointestinal disorders, such as diarrhea and intestinal inflammation. The objective of this study was to evaluate the effects of a methanolic extract from the bark of Qualea parviflora (QP) in an experimental model of diarrhea and intestinal inflammation induced in rodents.

MATERIAL AND METHODS

The antidiarrheal and antispasmodic effects of QP were investigated by measuring intestinal motility, diarrhea, and intestinal fluid accumulation in rodents after challenging with a cathartic agent. In addition, the effects of QP on the contractility of the isolated mice-ileum preparation were determined. Acute intestinal inflammation was induced in male Wistar rats by the rectal administration of trinitrobenzenesulfonic acid (TNBS) in 50% ethanol (0.25 mL). QP was administered orally (for 5 days) prior to the induction of inflammation. The colonic injury and extent of inflammation were assessed by macroscopic damage scores and lesion length. The enhanced colonic mucosal injury, inflammatory response, and oxidative stress were evaluated by myeloperoxidase (MPO) activity; the tumor necrosis factor alpha (TNF-α), interleukin 1β (IL1-β), and malondialdehyde (MDA) levels; and the glutathione (GSH) content.

RESULTS

Oral treatment with QP (500 mg/kg) delayed the onset of diarrhea, reduced the amount of liquid stool, and decreased the severity of the diarrhea and the evacuation index in rodents challenged with castor oil (p<0.01). Additionally, QP (150-500 µg/mL) demonstrated effective antispasmodic activity against carbachol-induced contractions of mouse ileum in vitro. Oral treatment (25 and 50 mg/kg/day) with QP significantly reduced the intestinal inflammation induced by TNBS in rats (52% and 45%, respectively). Improvement of colonic mucosal injury by treatment with QP was demonstrated by a decrease in MDA levels and an increase in GSH content in colonic tissue. QP also prevented intestinal inflammation as evidenced by reduced cytokine levels (TNF-α and IL1-β) and low MPO activity.

CONCLUSIONS

The ethnopharmacological usefulness of the bark from Qualea parviflora against diarrhea containing blood and mucus was supported by the observed antidiarrheal, antispasmodic, and intestinal antiinflammatory properties of this medicinal plant.

Inhibition of tumor necrosis factor-alpha and cyclooxigenase-2 by Isatin: a molecular mechanism of protection against TNBS-induced colitis in rats

Isatin, an indole alkaloid has been shown to have anti-microbial, anti-tumor and anti-inflammatory effects. Due to its findings, we evaluated whether this alkaloid would have any effect on TNBS-induced colitis. Animals (male Unib:WH rats, aged 8 weeks old) were induced colitis through a rectal administration of 2,4,6-trinitrobenzene sulphonic acid using a catheter inserted 8 cm into the rectum of the animals. The rats were divided into two major groups: non-colitic and colitic. The colitic group was sub-divided into 6 groups (10 animals per group): colitic non-treated, Isatin 3; 6; 12.5; 18.75 and 25 mg/kg. Our main results showed that the oral treatment with Isatin 6 and 25 mg/kg were capable of avoiding the increase in TNF-α, COX-2 and PGE₂ levels when compared to the colitic non-treated group. Interestingly, the same doses (6 and 25 mg/kg) were also capable of preventing the decrease in IL-10 levels comparing with the colitic non-treated group. The levels of MPO, (an indirect indicator of neutrophil presence), were also maintained lower than those of the colitic non-treated group. Isatin also prevented the decrease of SOD activity and increase of GSH-Px and GSH-Rd activity as well as the depletion of GSH levels. In conclusion, both pre-treatments (6 and 25 mg/kg) were capable of protecting the gut mucosa against the injury caused by TNBS, through the combination of antioxidant and anti-inflammatory properties, which, together, showed a protective activity of the indole alkaloid Isatin.

Comparison of experimental mouse models of inflammatory bowel disease

Inflammatory bowel disease (IBD) is multifactorial and involves immunological, environmental and genetic factors. Although there are no animal models that effectively mimic human IBD, experimental models allow us to analyze the mechanisms of chronic intestinal inflammation. IBD can be induced in mice by dextran sulfate sodium (DSS) or by a 2,4,6-trinitrobenzene sulfonic acid (TNBS)‑ethanol enema, which evoke immune responses and colitis. In this study, in order to compare the mechanisms of inflammatory response in mice, 3 distinct models of IBD were established: 2% TNBS-induced acute colitis, 4% DSS-induced acute colitis and 2% DSS-induced chronic colitis. In addition, to evaluate the effects of TNBS on inflammasome activation, we used caspase-1 knockout (KO) mice. Changes in both body weight and survival became prominent after day 1 in the 2% TNBS‑induced colitis model, and after day 5 in the 4% DSS-induced colitis model. The TNBS- and DSS-treated mice, but not the caspase-1 KO mice, showed a massive bowel edema and disruption of epithelial cells. The level of CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs) was increased in all tested tissues of the TNBS- and DSS-treated groups, apart from the basal membrane (BM) in the DSS-induced colitis groups and the lamina propria (LP) in the DSS-induced chronic colitis group. We further analyzed different subsets of CD4(+) T cells in LP and found that the levels of interferon (IFN)γ‑secreting (IFNγ(+)), IL-17‑secreting (IL-17(+)), but not those of IL-4-secreting (IL-4(+)) T cells increased upon treatment with TNBS or DSS. In addition, discrepancies between the histopathologies of wild-type and caspase-1 KO mice indicated that the pathogenesis of IBD may be associated with the inflammasome pathway responses mediated by caspase‑1 in TNBS‑induced colitis.

Validation of bovine glycomacropeptide as an intestinal anti-inflammatory nutraceutical in the lymphocyte-transfer model of colitis

Milk κ-casein-derived bovine glycomacropeptide (GMP) exerts immunomodulatory effects. It exhibits intestinal anti-inflammatory activity in chemically induced models of colitis. However, to validate its clinical usefulness as a nutraceutical, it is important to assess its effects in a model with a closer pathophysiological connection with human inflammatory bowel disease. Therefore, in the present study, we used the lymphocyte-transfer model of colitis in mice and compared the effects of GMP in this model with those obtained in the dextran sulphate sodium (DSS) model. GMP (15 mg/d) resulted in higher body-weight gain and a reduction of the colonic damage score and myeloperoxidase (MPO) activity in Rag1(-/-) mice with colitis induced by the transfer of naïve T cells. The colonic and ileal weight:length ratio was decreased by approximately 25%, albeit non-significantly. GMP treatment reduced the percentage of CD4⁺ interferon (IFN)-γ⁺ cells in mesenteric lymph nodes (MLN). The basal production of IL-6 by MLN obtained from the GMP-treated mice ex vivo was augmented. However, concanavalin A-evoked production was similar. The colonic expression of regenerating islet-derived protein 3γ, S100A8, chemokine (C-X-C motif) ligand 1 and IL-1β was unaffected by GMP, while that of TNF-α and especially IFN-γ was paradoxically increased. In the DSS model, GMP also reduced the activity of colonic MPO, but it failed to alter weight gain or intestinal weight:length ratio. GMP augmented the production of IL-10 by MLN cells and was neutral towards other cytokines, except exhibiting a trend towards increasing the production of IL-6. The lower effect was attributed to the lack of the effect of GMP on epithelial cells. In conclusion, GMP exerts intestinal anti-inflammatory effects in lymphocyte-driven colitis.

Anti-inflammatory effect of elemental diets with different fat composition in experimental colitis

The aim of the present study was to evaluate the effectiveness of two isoenergetic elemental formulae with different fat content in the rat model of trinitrobenzene sulphonic acid (TNBS) colitis that mimics human inflammatory bowel disease. A total of forty-five male Wistar rats were assigned to five groups: (1) control group; (2) TNBS-induced colitis group; (3) TNBS-induced colitis group fed a long-chain TAG (LCT)-rich diet; (4) TNBS-induced colitis group fed a medium-chain TAG (MCT)-rich diet; (5) TNBS-induced colitis group fed a baseline diet and administered infliximab. Nutritional management lasted 12 d before and 4 d after rectal administration of TNBS. Subsequently, the rats were killed, and colonic tissue samples were collected for the assessment of histology, inflammation and oxidative stress. The MCT-rich diet decreased IL-6, IL-8 and intercellular adhesion molecule-1 (ICAM-1) levels and glutathione S-transferase (GST) activity, while the LCT-rich diet reduced only ICAM-1 levels and GST activity (P< 0·05). Neither elemental formula affected IL-10 levels. Infliximab reduced IL-8 and ICAM-1 levels and GST activity and increased IL-10 levels (P< 0·05). No significant differences were detected in oxidative stress. Histological damage scores differed significantly only between the control and the TNBS-induced colitis group. A MCT-rich formula seems to exert stronger anti-inflammatory effects than a LCT-rich formula in TNBS colitis.

Advances in therapeutic interventions targeting the vascular and lymphatic endothelium in inflammatory bowel disease

PURPOSE OF REVIEW

The review summarizes the current knowledge of the roles played by the vascular and lymphatic endothelium throughout the gut in the pathogenesis of inflammatory bowel disease (IBD) and gives an update on emerging strategies targeting both vasculatures.

RECENT FINDINGS

Enormous efforts have been made to understand the mechanisms underlining the origin, development and maintenance of intestinal chronic inflammation. In particular, new studies focused their attention on the role played by the microvascular and lymphatic endothelium in the pathogenesis of IBD. During inflammation, whereas the microvasculature is responsible for the entry and distribution of immune cells in the mucosa, the lymphatic system controls leukocyte exit, bacterial clearance and edema absorption. The study of these events, which are aberrant during chronic inflammation, has resulted in the identification and validation of several targets for the treatment of experimental colitis, some of which have translated into effective treatments for patients with IBD.

SUMMARY

Although much attention has been paid to the microvascular endothelium and to antiangiogenic therapies, specific studies on the lymphatic vasculature and its functions in IBD are still at the initial stage, and other molecular mechanisms, genes, molecules and new pathways must definitely be explored.

The effect of melatonin on plasma markers of inflammation and on expression of nuclear factor-kappa beta in acetic acid-induced colitis in the rat

BACKGROUND AND AIMS

Melatonin may be involved in gastrointestinal tract physiology and could affect inflammation-related gastrointestinal disorders. Rat models of ulcerative colitis imply melatonin is beneficial. To determine potential pathophysiological mechanisms, we assessed colonic nuclear factor-kappa beta expression and measured serum levels of pentraxin-3, lipid peroxides, and total thiols in an acetic acid model of this disease.

MATERIALS AND METHODS

Thirty rats were divided into five groups: a control group, an acetic acid-induced colitis group, a group treated with melatonin before colitis induction, a group treated short-term after colitis induction, and a group treated long-term after colitis induction. After four weeks, blood samples were taken for measurement of pentraxin-3, lipid peroxide, and total thiols. Sections of the colon were taken for histopathological examination and immunohistochemical detection of nuclear factor-kappa beta expression.

RESULTS

Melatonin administration reduced nuclear factor-kappa beta immunohistochemical expression, reduced serum levels of lipid peroxide and pentraxin-3, and maintained serum levels of total thiols. However, in long-term treatment the protective effect of melatonin was not as marked.

CONCLUSION

Melatonin is effective in prevention and short-term treatment of the inflammatory process in acetic-acid induced colitis whereas the benefit of long-term treatment is unclear. Benefit may be linked to protection mechanisms against inflammatory processes by inhibiting the nuclear factor-kappa beta and conserving endogenous antioxidant reserves of total thiols, thus reducing the level of colonic damage possibly caused by lipid peroxides.

Study on the interactions between transplanted bone marrow-derived mesenchymal stem cells and regulatory T cells for the treatment of experimental colitis

Accumulating evidence has established the use of mesenchymal stem cells (MSCs) as candidate cells for immunosuppressive therapy. Experimental studies have suggested that MSCs exert their immunomodulatory effects through the induction of regulatory T cells (Tregs) in vitro and in vivo. However, the interactions between MSCs and Tregs in inflammatory bowel disease (IBD) and whether MSCs can be used for the treatment of IBD remains to be elucidated. In this study, we aimed to investigate whether MSCs can be used for the treatment of IBD through the induction of Tregs. MSCs were isolated and identified by flow cytometry. The MSCs were transduced with a replication-defective recombinant lentiviral vector carrying GFP in order to be able to trace the injected cells in vivo. Prepared MSCs (1x106) were injected into rats with 2,4,6-trinitrobenzene sulfonic acid (TNBS)‑induced colitis via the tail vein; the control rats received phosphate-buffered saline (PBS) alone. Two weeks after the intravenous infusion, the frequency of CD4+CD25+Foxp3 cells in the peripheral blood was examined by flow cytometry. The colon was sectioned and analyzed for histopathological changes. Foxp3 mRNA expression was determined by real-time reverse-transcription polymerase chain reaction (qRT-PCR). In our study, the systemic infusion of MSCs significantly ameliorated the clinical and histopathologic severity of TNBS-induced colitis in contrast to the controls. There was an inverse regulation of mucosal and peripheral Foxp3 expression, suggesting that the MSCs redistributed the Tregs from the mucosa to the blood. Thus, MSCs exhibit immunomodulatory functions and may be used to ameliorate or treat IBD by redistributing regulatory T cells. Therefore, the interactions between transplanted bone marrow-derived MSCs and Tregs should be further investigated; MSCs have tremendous potential for use in the treatment of IBD.

A new heterotopic transplant animal model of intestinal fibrosis

BACKGROUND

Severe mucosal tissue damage requiring efficient wound healing is a main feature of inflammatory bowel disease but excessive tissue repair promotes fibrosis. The clinical investigation of fibrosis is confined to the limited amount of biological material available from patients. This makes the establishment of a new animal model, a highly desirable goal. We investigated whether intestinal fibrosis occurs after heterotopic transplantation of small bowel resections in rats.

METHODS

Donor (Brown Norway or Lewis rats) small bowel resections were transplanted subcutaneously into the neck of recipients (Lewis rats). Grafts were explanted 2, 7, 14, and 21 days after transplantation.

RESULTS

Heterotopic intestinal transplants remained viable for 21 days. Rapid loss of crypt structures at day 2 after intestinal transplantation was followed by lymphocyte infiltration and obliteration of the intestinal lumen by fibrous tissue at day 21. Loss of the intestinal epithelium was confirmed by the lack of cytokeratin staining in immunohistochemistry. Collagen expression was increased with time after transplantation as confirmed by real-time PCRs, Elastica van Gieson, and Sirius Red staining. Lumen obliteration was connected with increased expression of potent mediators of fibrosis such as α5β6 integrin, interleukin (IL)-13, and transforming growth factor β. Myofibroblast phenotype was demonstrated by the presence of both α-smooth muscle actin and vimentin in the obliterated lumen.

CONCLUSIONS

We established a method for heterotopic transplantation of small bowel resections. A variety of histologic and molecular features of fibrosis were observed in the heterotopic intestinal grafts which suggests, that this new in vivo model will be instrumental in studying pathogenesis and treatment of intestinal fibrosis.

Effects of curcumin on apoptosis and oxidoinflammatory regulation in a rat model of acetic acid-induced colitis: the roles of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase

The present study evaluated the effects of curcumin on epithelial cell apoptosis, the immunoreactivity of the phospho-c-Jun N-terminal kinase (JNK) and phospho-p38 mitogen-activated protein kinases (MAPKs) in inflamed colon mucosa, and oxidative stress in a rat model of ulcerative colitis induced by acetic acid. Rats were randomly divided into three groups: control, acetic acid, and acetic acid+curcumin. Curcumin (100 mg/kg per day, intragastrically) was administered 10 days before the induction of colitis and was continued for two additional days. Acetic acid-induced colitis caused a significant increase in the macroscopic and microscopic tissue ranking scores as well as an elevation in colonic myeloperoxidase (MPO) activity, malondialdehyde (MDA) levels, and the number of apoptotic epithelial cells in colon tissue compared to controls. In the rat colon, immunoreactivity of phospho-p38 MAPK was increased, whereas the phospho-JNK activity was decreased following the induction of colitis. Curcumin treatment was associated with amelioration of macroscopic and microscopic colitis sores, decreased MPO activity, and decreased MDA levels in acetic acid-induced colitis. Furthermore, oral curcumin supplementation clearly prevented programmed cell death and restored immunreactivity of MAPKs in the colons of colitic rats. The results of this study suggest that oral curcumin treatment decreases colon injury and is associated with decreased inflammatory reactions, lipid peroxidation, apoptotic cell death, and modulating p38- and JNK-MAPK pathways.

Effects of sinomenine on the expression of microRNA-155 in 2,4,6-trinitrobenzenesulfonic acid-induced colitis in mice

Background

Sinomenine, a pure alkaloid isolated in Chinese medicine from the root of Sinomenium acutum, has been demonstrated to have anti-inflammatory and immunosuppressive effects. MicroRNAs (miRNAs) are gradually being recognized as critical mediators of disease pathogenesis via coordinated regulation of molecular effector pathways.

Methodology/Findings

After colitis was induced in mice by instillation of 5% (w/v) 2,4,6-trinitrobenzenesulfonic acid (TNBS), sinomenine at a dose of 100 or 200 mg/kg was orally administered once daily for 7 days. We evaluated body weight, survival rate, diarrhea score, histological score and myeloperoxidase (MPO) activity. The mRNA and protein expression levels of miR-155, c-Maf, TNF-α and IFN-γ were determined by quantitative RT-PCR and immunohistochemistry, respectively. Sinomenine (100 or 200 mg/kg)-treated mice with TNBS-induced colitis were significantly improved in terms of body weight, survival rate, diarrhea score, histological score and MPO activity compared with untreated mice. Both dosages of sinomenine significantly decreased the mRNA and protein expression levels of c-Maf, TNF-α and IFN-γ, which elevated in TNBS-induced colitis. Furthermore, sinomenine at a dose of 200 mg/kg significantly decreased the level of miR-155 expression by 71% (p = 0.025) compared with untreated TNBS-induced colitis in mice.

Conclusions/Significance

Our study evaluated the effects and potential mechanisms of sinomenine in the anti-inflammatory response via miRNA-155 in mice with TNBS-induced colitis. Our findings suggest that sinomenine has anti-inflammatory effects on TNBS-induced colitis by down-regulating the levels of miR-155 and several related inflammatory cytokines.

Enhanced synthesis and diminished degradation of hydrogen sulfide in experimental colitis: a site-specific, pro-resolution mechanism

Hydrogen sulfide (H₂S) is produced throughout the gastrointestinal tract, and it contributes to maintenance of mucosal integrity, resolution of inflammation, and repair of damaged tissue. H₂S synthesis is elevated in inflamed and damaged colonic tissue, but the enzymatic sources of that synthesis are not completely understood. In the present study, the contributions of three enzymatic pathways to colonic H₂S synthesis were determined, with tissues taken from healthy rats and rats with colitis. The ability of the colonic tissue to inactivate H₂S was also determined. Colonic tissue from rats with hapten-induced colitis produced significantly more H₂S than tissue from healthy controls. The largest source of the H₂S synthesis was the pathway involving cysteine amino transferase and 3-mercaptopyruvate sulfurtransferase (an α-ketoglutarate-dependent pathway). Elevated H₂S synthesis occurred specifically at sites of mucosal ulceration, and was not related to the extent of granulocyte infiltration into the tissue. Inactivation of H₂S by colonic tissue occurred rapidly, and was significantly reduced at sites of mucosal ulceration. This correlated with a marked decrease in the expression of sulfide quinone reductase in these regions. Together, the increased production and decreased inactivation of H₂S at sites of mucosal ulceration would result in higher H₂S levels at these sites, which promotes of resolution of inflammation and repair of damaged tissue.

Involvement of MAPK/NF-κB signaling in the activation of the cholinergic anti-inflammatory pathway in experimental colitis by chronic vagus nerve stimulation

BACKGROUND

Autonomic nervous system dysfunction is implicated in the etiopathogenesis of inflammatory bowel diseases (IBD). Therapies that increase cardiovagal activity, such as Mind-Body interventions, are currently confirmed to be effective in clinical trials in IBD. However, a poor understanding of pathophysiological mechanisms limits the popularization of therapies in clinical practice. The aim of the present study was to explore the mechanisms of these therapies against 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats using a chronic vagus nerve stimulation model in vivo, as well as the lipopolysaccharide (LPS)-induced inflammatory response in human epithelial colorectal adenocarcinoma cells (Caco-2) by acetylcholine in vitro.

METHODS AND RESULTS

Colitis was induced in rats with rectal instillation of TNBS, and the effect of chronic VNS (0.25 mA, 20 Hz, 500 ms) on colonic inflammation was evaluated. Inflammatory responses were assessed by disease activity index (DAI), histological scores, myeloperoxidase (MPO) activity, inducible nitric oxide synthase (iNOS), TNF-α and IL-6 production. The expression of Mitogen-activated protein kinases (MAPK) family members, IκB-α, and nuclear NF-κB p65 were studied by immunoblotting. Heart rate variability (HRV) analysis was also applied to assess the sympathetic-vagal balance. DAI, histological scores, MPO activity, iNOS, TNF-α and IL-6 levels were significantly decreased by chronic VNS. Moreover, both VNS and acetylcholine reduced the phosphorylation of MAPKs and prevented the nuclear translocation of NF-κB p65. Methyllycaconitine (MLA) only reversed the inhibitory effect on p-ERK and intranuclear NF-κB p65 expression by ACh in vitro, no significant change was observed in the expression of p-p38 MAPK or p-JNK by MLA.

CONCLUSION

Vagal activity modification contributes to the beneficial effects of the cholinergic anti-inflammatory pathway in IBD-related inflamed colonic mucosa based on the activation of MAPKs and nuclear translocation of NF-κB. Our work may provide key pathophysiological mechanistic evidence for novel therapeutic strategies that increase the cardiovagal activity in IBD patients.

Alteration of neuromuscular transmissions in the hamster colon following the resolution of TNBS-induced colitis

The aim of this study was to determine whether trinitrobenzene sulfonic acid-induced colitis leads to alterations in enteric neuronal transmission in hamsters. We assessed the mechanical responses induced by the application of electrical field stimulation (EFS) in isolated segments of the distal colon. The EFS-induced relaxation and contraction were blocked by a nitric oxide synthase inhibitor and by the combination of antagonists for tachykinin NK1 and NK2 receptors and muscarinic acetylcholine receptors, respectively. The mechanical responses to EFS were attenuated in the inflamed colon at 7 days and were recovered by 30 days after inflammation treatment. In addition, we found that purinergic and opioidergic excitatory neural components are expressed following the resolution of colitis. These results suggest that colonic inflammation causes indiscriminate damage to enteric neurons but that neuronal components are restored and that new excitatory neural components, compensating for the contractile responses in smooth muscle after colitis, are expressed.

Novel effects of ectoine, a bacteria-derived natural tetrahydropyrimidine, in experimental colitis

Evidence suggests an important role of intestinal barrier dysfunction in the etiology of inflammatory bowel disease (IBD). Therefore stabilizing mucosal barrier function constitutes a new therapeutic approach in its management. Ectoine is a compatible solute produced by aerobic chemoheterotrophic and halophilic/halotolerant bacteria, where it acts as osmoprotectant and effective biomembrane stabilizer, protecting the producing cells from extreme environmental stress. Since this natural compound was also shown to prevent inflammatory responses associated with IBD, its potential usefulness was studied in a model of colitis. Groups of rats were treated orally with different doses of ectoine (30-300 mg/kg) or sulfasalazine (reference drug) daily for 11 days. On day 8 colitis was induced by intracolonic instillation of 2,4,6-trinitrobenzenesulfonic acid, when overt signs of lesions develop within the next 3 days. On day 12, blood was withdrawn from the retro-orbital plexus of the rats and the animals were sacrificed. The colon was excised and examined macroscopically and microscopically. Relevant parameters of oxidative stress and inflammation were measured in serum and colon homogenates. Induction of colitis led to marked weight loss, significant histopathological changes of the colon, and variable changes in levels of myeloperoxidase, reduced glutathione, malondialdehyde, and all inflammatory markers tested. Treatment with ectoine ameliorated the inflammatory changes in TNBS-induced colitis. This effect was associated with reduction in the levels of TNF-α, IL-1β, ICAM-1, PGE2 and LTB4. The findings suggest that intestinal barrier stabilizers from natural sources could offer new therapeutic measures for the management of IBD.

A sulfated-polysaccharide fraction from seaweed Gracilaria birdiae prevents naproxen-induced gastrointestinal damage in rats

Red seaweeds synthesize a great variety of sulfated galactans. Sulfated polysaccharides (PLSs) from seaweed are comprised of substances with pharmaceutical and biomedical potential. The aim of the present study was to evaluate the protective effect of the PLS fraction extracted from the seaweed Gracilaria birdiae in rats with naproxen-induced gastrointestinal damage. Male Wistar rats were pretreated with 0.5% carboxymethylcellulose (control group—vehicle) or PLS (10, 30, and 90 mg/kg, p.o.) twice daily (at 09:00 and 21:00) for 2 days. After 1 h, naproxen (80 mg/kg, p.o.) was administered. The rats were killed on day two, 4 h after naproxen treatment. The stomachs were promptly excised, opened along the greater curvature, and measured using digital calipers. Furthermore, the guts of the animals were removed, and a 5-cm portion of the small intestine (jejunum and ileum) was used for the evaluation of macroscopic scores. Samples of the stomach and the small intestine were used for histological evaluation, morphometric analysis and in assays for glutathione (GSH) levels, malonyldialdehyde (MDA) concentration, and myeloperoxidase (MPO) activity. PLS treatment reduced the macroscopic and microscopic naproxen-induced gastrointestinal damage in a dose-dependent manner. Our results suggest that the PLS fraction has a protective effect against gastrointestinal damage through mechanisms that involve the inhibition of inflammatory cell infiltration and lipid peroxidation.