Cyclical upregulated iNOS and long-term downregulated nNOS are the bases for relapse and quiescent phases in a rat model of IBD

Connecting the Dots Between Inflammatory Bowel Disease and Metabolic Syndrome: A Focus on Gut-Derived Metabolites

The role of the microbiome in health and disease has gained considerable attention and shed light on the etiology of complex diseases like inflammatory bowel disease (IBD) and metabolic syndrome (MetS). Since the microorganisms inhabiting the gut can confer either protective or harmful signals, understanding the functional network between the gut microbes and the host provides a comprehensive picture of health and disease status. In IBD, disruption of the gut barrier enhances microbe infiltration into the submucosae, which enhances the probability that gut-derived metabolites are translocated from the gut to the liver and pancreas. Considering inflammation and the gut microbiome can trigger intestinal barrier dysfunction, risk factors of metabolic diseases such as insulin resistance may have common roots with IBD. In this review, we focus on the overlap between IBD and MetS, and we explore the role of common metabolites in each disease in an attempt to connect a common origin, the gut microbiome and derived metabolites that affect the gut, liver and pancreas.

Process Design of the Antioxidant Shuidouchi and Its Effect on Preventing Dextran Sulfate Sodium (DSS)-Induced Colitis in Mice via Antioxidant Activity

Shuidouchi is a traditionally fermented soybean product in China. Shuidouchi production requires a variety of processes; however, the production process has not been standardized. It can be developed into high-quality products with enhanced health effects by improving the design of its fermentation process and increasing the content of its active ingredients. In this study, a single-factor experiment was conducted that established different process conditions to determine the fermentation conditions that achieve the highest content of active ingredients and the best in vitro antioxidant effect. The effect of Shuidouchi on the prevention of dextran sulfate sodium-induced colitis in mice was also observed. The obtained results indicated that the optimal process conditions involved soaking for 12 h, placement in a glass container, and fermentation at 35 °C for 48 h. Shuidouchi that was fermented under such conditions had the highest level of soybean isoflavones and exerted greater antioxidant effects than if fermented under other conditions. The Shuidouchi extract (soaking twice the quantity of water for 12 h, placing in a glass container, and fermenting at 35 °C for 48 h) obtained by using the optimal fermentation process can prevent the shortening of the colon and increase the weight-to-length ratio of the colon that is caused by colitis. Shuidouchi extraction not only effectively reduces the disease activity index and the levels of serum endothelin (ET), substance P (SP), and interleukin-10 (IL-10), it also increases the levels of somatostatin (SS), vasoactive intestinal peptide (VIP), and interleukin-2 (IL-2) of mice with colitis. In addition, Shuidouchi extraction increased the levels of glutathione (GSH) and superoxide dismutase (SOD) in colitis mice; in contrast, Shuidouchi decreased the levels of myeloperoxidase (MPO) and malondialdehyde (MDA) in the colon of mice with colitis. Further detection of mRNA in colon tissues showed that Shuidouchi extraction can upregulate the expression of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), c-Kit, and the stem cell factor (SCF). Furthermore, it can downregulate the expression of inducible nitric oxide synthase (iNOS), interleukin-8 (IL-8), and C-X-C chemokine receptor type 2 (CXCR2) in the colon of mice with colitis. Further experimental results showed that Shuidouchi could reduce the protein expression of interleukin 6 (IL-6), IL-12, and tumor necrosis factor-α (TNF-α) in colitic mice. Therefore, the improved processing of Shuidouchi inhibits colitis, which is directly related to the high content of soybean isoflavones.

Oridonin derivative ameliorates experimental colitis by inhibiting activated T-cells and translocation of nuclear factor-kappa B

OBJECTIVE

To confirm the potential therapeutic efficacy of HAO472 against inflammatory bowel disease (IBD), we investigated the modulatory functions of HAO472 in a mouse model of trinitrobenzene sulfonic acid (TNBS)-induced colitis.

METHODS

Colitis was induced via an intrarectal injection of TNBS in mice. HAO472 (5.0 mg/kg or 7.5 mg/kg) or 1 mg/kg dexamethasone (DX) was injected intraperitoneally into the mice after the TNBS administration. Behavioral and weight changes, macroscopic and histological assessments of colon, the expressions of tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-17A, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-κB) in the colonic tissues were evaluated. The effect of HAO472 on NF-κB signaling pathway in lymphocytes was also invesigated.

RESULTS

HAO472 significantly ameliorated the clinical symptoms, reduced the severity of the inflammation and decreased mortality in the mouse model. HAO472 also reduced TNF-α, IFN-γ, IL-17A, iNOS/COX-2 and lymphocyte proliferation. These changes were associated with a significant decrease in NF-κB p65 expression and activity.

CONCLUSION

HAO472 has positive effects on TNBS-induced colitis by modulating the subsets and functions of lymphocytes, suppressing inflammation and inhibiting the nuclear translocation of NF-κB p65 subunits.

The anti-inflammatory effect and potential mechanism of cardamonin in DSS-induced colitis

Cardamonin is a naturally occurring chalcone with strong anti-inflammatory activity. However, the direct effect of cardamonin on intestinal inflammation remains elusive. In the present study, we found that cardamonin markedly ameliorated dextran sulfate sodium-induced mouse body weight loss, diarrhea, colon shortening, spleen swelling, and histological damage, which correlated with a decline in the activity of myeloperoxidase and the production of nitric oxide, tumor necrosis factor-α and interleukin-6 in the colon. The upregulation of toll-like receptor 4 after dextran sulfate sodium treatment was associated with an increase in the activation of myeloid differentiation factor 88, interleukin-1 receptor-associated kinase-1, nuclear factor-κB (NF-κB) p65, inhibitor κBα, and inhibitor κB kinase-α/β, as well as the mitogen-activated protein kinase molecules of extracellular signal-regulated kinase and c-Jun NH2-terminal kinase, and this upregulation was reversed by cardamonin administration. Moreover, cardamonin blocked the nuclear translocation of NF-κB p65, inhibited NF-κB-luciferase activity, and downregulated NF-κB target genes expression. The present study clearly demonstrates a beneficial effect of cardamonin on experimental inflammatory bowel disease via a mechanism associated with suppression of toll-like receptor 4 expression and inactivation of NF-κB and mitogen-activated protein kinase pathways. This study may give insight into the further evaluation of the therapeutic potential of cardamonin or its derivatives for human inflammatory bowel disease.

NOS1-derived nitric oxide promotes NF-κB transcriptional activity through inhibition of suppressor of cytokine signaling-1

The NF-κB pathway is central to the regulation of inflammation. Here, we demonstrate that the low-output nitric oxide (NO) synthase 1 (NOS1 or nNOS) plays a critical role in the inflammatory response by promoting the activity of NF-κB. Specifically, NOS1-derived NO production in macrophages leads to proteolysis of suppressor of cytokine signaling 1 (SOCS1), alleviating its repression of NF-κB transcriptional activity. As a result, NOS1(-/-) mice demonstrate reduced cytokine production, lung injury, and mortality when subjected to two different models of sepsis. Isolated NOS1(-/-) macrophages demonstrate similar defects in proinflammatory transcription on challenge with Gram-negative bacterial LPS. Consistently, we found that activated NOS1(-/-) macrophages contain increased SOCS1 protein and decreased levels of p65 protein compared with wild-type cells. NOS1-dependent S-nitrosation of SOCS1 impairs its binding to p65 and targets SOCS1 for proteolysis. Treatment of NOS1(-/-) cells with exogenous NO rescues both SOCS1 degradation and stabilization of p65 protein. Point mutation analysis demonstrated that both Cys147 and Cys179 on SOCS1 are required for its NO-dependent degradation. These findings demonstrate a fundamental role for NOS1-derived NO in regulating TLR4-mediated inflammatory gene transcription, as well as the intensity and duration of the resulting host immune response.

Transplantation of bone marrow-derived mesenchymal stem cells facilitates epithelial repair and relieves the impairment of gastrointestinal function in a rat model of enteritis

BACKGROUND

To examine whether the bone marrow-derived MSCs (BM-MSCs) could facilitate epithelial repair and thereby reduce impairment of gastrointestinal structure and function in chronic murine enteritis induced by indomethacin (IDM).

METHODS

MSCs were isolated from young Sprague-Dawley rats. After in vitro expansion and characterization, BM-MSCs were labelled with the fluorescent dye PKH26 and transfused, via the tail veins, into rats with enteritis induced by IDM. The controls were infused with sterile saline. The homing and differentiation of the transplanted BM-MSCs were tracked by means of fluorescent staining. The clinical symptoms of the IDM-treated rats were assessed, and the macroscopic and microscopic histological evaluations of the intestines were performed.

RESULTS

Compared to controls that received saline infusion, BM-MSCs treated rats showed lower scores of weight loss, stool consistency, and stool blood. The PKH26-labelled cells resided at the injured intestine, where they co-localize with the proliferating cell nuclear antigen (PCNA), Lgr-5, and Msi-1. The BM-MSCs treated rats showed significantly higher intestinal villi with larger areas relative to the saline-treated rats.

CONCLUSION

The transplanted BM-MSCs are able to recognize the injured intestine, where they proliferate and transdifferentiate into intestinal stem cells which repair the injured intestinal tissues. Therefore, BM-MSCs are able to relieve the impairment of gastrointestinal function in IMD-treated rats.

Nitrergic neuro-muscular transmission is up-regulated in patients with diverticulosis

BACKGROUND

Neuro-transmission impairment could be associated to motility changes observed in patients with diverticular disease. Therefore, the objective was to characterize the inhibitory neuro-muscular transmission and gene expression changes of the enteric inhibitory pathways in patients with diverticulosis (DS).

METHODS

Circular muscle strips from sigmoid colon of patients with DS and controls were studied using the organ bath technique to evaluate spontaneous contractility and enteric motor neurons stimulated by electrical field and qRT-PCR to assess the expression of nNOS, iNOS, P2Y1 R and PGP9.5.

KEY RESULTS

Patients with DS presented decreased spontaneous rhythmic contractions (SRC) that were significantly enhanced after incubation with L-NNA (1 mM) and TTX (1 μM), and unaffected by the P2Y1 antagonist MRS2500 (1 μM). Stimulation on enteric motor neurons caused an increased duration of the latency of OFF-contractions in DS group (p < 0.001), antagonized by L-NNA and slightly affected by MRS2500 (1 μM). No differences in the IC50 between controls and DS patients were observed on inhibition of SRC for the NO-donor sodium nitroprusside (SNP) and the preferential P2Y agonist ADPβS. Moreover, nNOS relative expression was also up-regulated 2.3-fold in the DS group (p < 0.05) whereas there was no significant difference in relative expression of iNOS, P2Y1 R and the neuronal marker PGP9.5 between groups.

CONCLUSIONS & INFERENCES

Patients with DS presented an over-expression of nNOS with increased endogenously NO-mediated responses suggesting enhanced NO-release. Up-regulation in the nitrergic pathway in early stages of the disease might play a role in colonic motor disorders associated to diverticular disease.

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.

Roles of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal transplantation of rats

OBJECTIVE

The study was designed to evaluate the role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in ischemia-reperfusion injury (IRI) and acute rejection (AR) in rat intestinal transplantation, by administration of nitric oxide inhibitor N(G)-nitro-L-arginine methyl ester (LNAME).

MATERIALS AND METHODS

Rats that underwent orthotopic intestinal transplantation were assigned to 2 sets of groups: (1) iso-geneic group (Lewis-Lewis), L-NAME 0 mg/kg/d group (1-1), 4 mg/kg/d (group 1-2), or 8 mg/kg/d (group 1-3) injected intraperitoneally or (2) allogeneic group (Dark Agouti-Lewis), L-NAME 0 mg/kg/d (group 2-1) or 8 mg/kg/d (group 2-2) injected intraperitoneally. We examined survival times, light microscopy as well as maltose absorption tests. The nNOS and iNOS activities were measured by immunohistochemical methods.

RESULTS

Histologic examination showed inhibited iNOS activity compared with group l-l, and Park scores decreased significantly in group 1-2 at 30 minutes after reperfusion (1.42 ± 0.38 vs 2.58 ± 0.49, P < .01). Both iNOS and nNOS activities were inhibited and Park scores increased significantly in group 1-3 from 30 minutes to day 3 after reperfusion (P < .0l). nNOS activity decreased and iNOS activity increased among group 2-1 during AR. Compared with group 2-1, iNOS activity was inhibited, progression of AR delayed, and survival significantly prolonged in group 2-2 (10.17 ± 0.98 vs 6.83 ± 0.75, P < .01).

CONCLUSION

This study suggested that decreased nNOS and increased iNOS activity both contributed to IRI and AR. More importantly, nNOS more importantly than iNOS activity was closely related to graft structure and function.

Anti-inflammatory effect of recreational exercise in TNBS-induced colitis in rats: role of NOS/HO/MPO system

There are opposite views in the available literature: Whether physical exercise has a protective effect or not on the onset of inflammatory bowel disease (IBD). Therefore, we investigated the effects of recreational physical exercise before the induction of colitis. After 6 weeks of voluntary physical activity (running wheel), male Wistar rats were treated with TNBS (10 mg). 72 hrs after trinitrobenzene sulphonic acid (TNBS) challenge we measured colonic gene (TNF-α, IL-1β, CXCL1 and IL-10) and protein (TNF-α) expressions of various inflammatory mediators and enzyme activities of heme oxygenase (HO), nitric oxide synthase (NOS), and myeloperoxidase (MPO) enzymes. Wheel running significantly increased the activities of HO, constitutive NOS (cNOS) isoform. Furthermore, 6 weeks of running significantly decreased TNBS-induced inflammatory markers, including extent of lesions, severity of mucosal damage, and gene expression of IL-1β, CXCL1, and MPO activity, while IL-10 gene expression and cNOS activity were increased. iNOS activity decreased and the activity of HO enzyme increased, but not significantly, compared to the sedentary TNBS-treated group. In conclusion, recreational physical exercise can play an anti-inflammatory role by downregulating the gene expression of proinflammatory mediators, inducing anti-inflammatory mediators, and modulating the activities of HO and NOS enzymes in a rat model of colitis.

Long-term dietary L-arginine supplementation increases endothelial nitric oxide synthase and vasoactive intestinal peptide immunoexpression in rat small intestine

BACKGROUND AND AIMS

Nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) are important intestinal neurotransmitters that coexist in the gut enteric nervous system and play an important role in intestinal physiology (e.g., absorption, motility, fluid secretion and smooth muscle relaxation). It is also known that cold exposure alters several aspects of gastrointestinal physiology and induces hyperphagia to meet increased metabolic demands, but there are no data regarding NO and VIP involvement in intestinal response during acclimation to cold. The objective of this study was to determine the influence of long-term L-arginine supplementation on the expression of the three isoforms of nitric oxide synthase (NOS) and VIP in small intestine of rats acclimated to room temperature or cold.

METHODS

Animals (six per group) acclimated to room temperature (22 ± 1 °C) and cold (4 ± 1 °C), respectively, were treated with 2.25% L-arginine, a substrate for NOSs, or with 0.01% N(ω)-nitro-L-arginine methyl ester, an inhibitor of NOSs, for 45 days. The topographical distribution of VIP and NOSs expression in small intestine was studied by immunohistochemistry, and ImageJ software was used for semiquantitative densitometric analysis of their immunoexpression.

RESULTS

Long-term dietary L-arginine supplementation increases VIP and NOSs immunoexpression at room temperature while at cold increases the endothelial NOS, inducible NOS and VIP but decrease neuronal NOS in rat small intestine.

CONCLUSION

Our results demonstrate that long-term dietary L-arginine supplementation modulates NOSs and VIP immunoexpression in rat small intestine with respect to ambient temperature, pointing out the eNOS as a predominant NOS isoform with an immunoexpression pattern similar to VIP.

In vivo, in vitro, and in silico studies suggest a conserved immune module that regulates malaria parasite transmission from mammals to mosquitoes

Human malaria can be caused by the parasite Plasmodium falciparum that is transmitted by female Anopheles mosquitoes. "Immunological crosstalk" between the mammalian and anopheline hosts for Plasmodium functions to control parasite numbers. Key to this process is the mammalian cytokine transforming growth factor-β1 (TGF-β1). In mammals, TGF-β1 regulates inducible nitric oxide (NO) synthase (iNOS) both positively and negatively. In some settings, high levels of NO activate latent TGF-β1, which in turn suppresses iNOS expression. In the mosquito, ingested TGF-β1 induces A. stephensi NOS (AsNOS), which limits parasite development and which in turn is suppressed by activation of the mosquito homolog of the mitogen-activated protein kinases MEK and ERK. Computational models linking TGF-β1, AsNOS, and MEK/ERK were developed to provide insights into this complex biology. An initial Boolean model suggested that, as occurs in mammalian cells, MEK/ERK and AsNOS would oscillate upon ingestion of TGF-β1. An ordinary differential equation (ODE) model further supported the hypothesis of TGF-β1-induced multiphasic behavior of MEK/ERK and AsNOS. To achieve this multiphasic behavior, the ODE model was predicated on the presence of constant levels of TGF-β1 in the mosquito midgut. Ingested TGF-β1, however, did not exhibit this behavior. Accordingly, we hypothesized and experimentally verified that ingested TGF-β1 induces the expression of the endogenous mosquito TGF-β superfamily ligand As60A. Computational simulation of these complex, cross-species interactions suggested that TGF-β1 and NO-mediated induction of As60A expression together may act to maintain multiphasic AsNOS expression via MEK/ERK-dependent signaling. We hypothesize that multiphasic behavior as represented in this model allows the mosquito to balance the conflicting demands of parasite killing and metabolic homeostasis in the face of damaging inflammation.

Effective treatment of mouse experimental colitis by alpha 2 integrin antibody: comparison with alpha 4 antibody and conventional therapy

AIM

To compare the therapeutic effect of α(2) and α(4) integrin-blocking antibodies to conventional inflammatory bowel disease drugs methotrexate, 5-aminosalicylic acid and azathioprine in the dextran sulphate sodium mouse colitis model.

METHODS

Colitis was induced in balb/c mice with 2.5-3.0% dextran sulphate sodium. Treatment was given daily for 7 days after the onset of colitis, by rectal installation. Clinical signs of disease were assessed daily using a disease activity index. After 19 days, all animals were killed and colon samples collected for histological grading and mRNA/protein analysis. All treatment groups were compared with an untreated control group and a treatment group receiving dextran sulphate sodium alone to monitor the potential degree of clinical remission.

RESULTS

Treatment with anti-α(2) antibodies and methotrexate reduced the body weight loss. At the end of treatment, anti-α(2) antibodies reduced rectal bleeding, while methotrexate reduced the disease activity index score. Histological evaluation showed that anti-α(2) antibodies, methotrexate, 5-aminosalicylic acid and azathioprine treatment reduced the acute inflammation; methotrexate was the only treatment with effect on the crypt score. Compared with the dextran sulphate sodium alone group, the methotrexate group showed down-regulation of IL-1β at the mRNA level, while the anti-α(2) antibody group displayed decreased protein expression of iNOS and IL-1β.

CONCLUSIONS

Specific blocking of extravascular trafficking of leucocytes with α(2)-antibodies could be a new beneficial drug target in inflammatory bowel disease.

S-nitrosylated protein disulfide isomerase contributes to mutant SOD1 aggregates in amyotrophic lateral sclerosis

A major hallmark of mutant superoxide dismutase (SOD1)-linked familial amyotrophic lateral sclerosis is SOD1-immunopositive inclusions found within motor neurons. The mechanism by which SOD1 becomes aggregated, however, remains unclear. In this study, we aimed to investigate the role of nitrosative stress and S-nitrosylation of protein disulfide isomerase (PDI) in the formation of SOD1 aggregates. Our data show that with disease progression inducible nitric oxide synthase (iNOS) was up-regulated, which generated high levels of nitric oxide (NO) and subsequently induced S-nitrosylation of PDI in the spinal cord of mutant SOD1 transgenic mice. This was further confirmed by in vitro observation that treating SH-SY5Y cells with NO donor S-nitrosocysteine triggered a dose-dependent formation of S-nitrosylated PDI. When mutant SOD1 was over-expressed in SH-SY5Y cells, the iNOS expression was up-regulated, and NO generation was consequently increased. Furthermore, both S-nitrosylation of PDI and the formation of mutant SOD1 aggregates were detected in the cells expressing mutant SOD1(G93A). Blocking NO generation with the NOS inhibitor N-nitro-L-arginine attenuated the S-nitrosylation of PDI and inhibited the formation of mutant SOD1 aggregates. We conclude that NO-mediated S-nitrosylation of PDI is a contributing factor to the accumulation of mutant SOD1 aggregates in amyotrophic lateral sclerosis.

Increased proportion of nitric oxide synthase immunoreactive neurons in rat ileal myenteric ganglia after severe acute pancreatitis

BACKGROUND

Severe acute pancreatitis (SAP) remains a potentially life-threatening disease. Gastrointestinal motility disturbance such as intestinal ileus is seen in every case. By now, the mechanisms of pancreatitis-induced ileus are largely unknown. The main purpose of the present study was to observe changes of nitric oxide synthase-immunoreactive (NOS-IR) neurons in ileal myenteric ganglia in SAP rats with gastrointestinal dysmotility, trying to explore underlying nervous mechanisms of pancreatitis-induced ileus.

METHODS

Twenty Sprague Dawley rats were randomly divided into sham operated group and SAP group. SAP was induced by retrograde cholangiopancreatic duct injection of 5% sodium taurocholate. Abdominal X-ray and intestinal transit were performed to detect the existence of paralytic ileus and intestinal dysmotility. Pathological damage of pancreas was evaluated. Double-immunolabeling was employed for the whole-mount preparations of ileal myenteric ganglia. The morphology of NOS-IR neurons were observed and the percentage of NOS-IR neurons was calculated based on the total Hu-immunoreactive neurons. Total RNA of ileum was extracted according to Trizol reagent protocol. Neuronal NOS (nNOS) mRNA expression was evaluated by RT-PCR.

RESULTS

The small intestinal transit index in the SAP group was significantly lower compared with the sham operated group (29.21±3.68% vs 52.48±6.76%, P<0.01). The percentage of NOS-IR neurons in ileal myenteric ganglia in the SAP group was significantly higher than that in the sham operated group (37.5±12.28% vs 26.32±16.15%, P<0.01). nNOS mRNA expression in ileum of SAP group was significantly higher than that in the sham operated group (1.02±0.10 vs 0.70±0.06, P<0.01).

CONCLUSIONS

The increased quantity of NOS-IR neurons in ileal myenteric ganglia and increased nNOS mRNA expression may suggest nNOS over expression as one of the nervous mechanisms of gastrointestinal dysmotility in SAP rat.

Nitric oxide-releasing aspirin but not conventional aspirin improves healing of experimental colitis

AIM: To determine the effect of non-selective cyclooxygenase (COX) inhibitors, selective COX-2 inhibitors and nitric oxide (NO)-releasing aspirin in the healing of ulcerative colitis.

METHODS: Rats with 2,4,6 trinitrobenzenesulfon-ic acid (TNBS)-induced colitis received intragastric (ig) treatment with vehicle, aspirin (ASA) (a non-selective COX inhibitor), celecoxib (a selective COX-2 inhibitor) or NO-releasing ASA for a period of ten days. The area of colonic lesions, colonic blood flow (CBF), myeloperoxidase (MPO) activity and expression of proinflammatory markers COX-2, inducible form of nitric oxide synthase (iNOS), IL-1β and tumor necrosis factor (TNF)-α were assessed. The effects of glyceryl trinitrate (GTN), a NO donor, and 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-​tetramethyl-1H-imidazolyl-1-oxy-3-oxide, onopotassium salt (carboxy-PTIO), a NO scavenger, administered without and with ASA or NO-ASA, and the involvement of capsaicin-sensitive afferent nerves in the mechanism of healing the experimental colitis was also determined.

RESULTS: Rats with colitis developed macroscopic and microscopic colonic lesions accompanied by a significant decrease in the CBF, a significant rise in colonic weight, MPO activity and plasma IL-1β and TNF-α levels. These effects were aggravated by ASA and 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (SC-560), but not celecoxib and counteracted by concurrent treatment with a synthetic prostaglandin E₂ (PGE₂) analog. Treatment with NO-ASA dose-dependently accelerated colonic healing followed by a rise in plasma NO_x content and CBF, suppression of MPO and downregulation of COX-2, iNOS, IL-1β and TNF-α mRNAs. Treatment with GTN, the NO donor, significantly inhibited the ASA-induced colonic lesions and increased CBF, while carboxy-PTIO or capsaicin-denervation counteracted the NO-ASA-induced improvement of colonic healing and the accompanying increase in the CBF. These effects were restored by co-treatment with calcitonin gene related peptide (CGRP) and NO-ASA in capsaicin-denervated animals.

CONCLUSION: NO-releasing ASA, in contrast to ASA, COX-1 inhibitors, and SC-560, accelerated the healing of colitis via a mechanism involving NO mediated improvement of microcirculation and activation of sensory nerves releasing CGRP.

Bacterial translocation to mesenteric lymph nodes increases in chronic portal hypertensive rats

PURPOSE

Bacterial translocation is a frequent complication in portal hypertension related to cirrhosis in the human clinical area. The aim of this study was to verify the existence of intestinal bacterial translocation to mesenteric lymph nodes in male Wistar rats with triple partial portal vein ligation during short- (48 h) and long-term (1 month) postoperative evolution.

RESULTS

At 48 h, ileal total aerobes bacteria (p < 0.001) and Lactobacillus decrease in sham-operated (SO) and portal hypertensive (PH) rats. At 1 month, ileal Enterococci and Streptococcus sp. show a statistically significant decrease in SO- and PH-rats. Lactobacillus decreases in the colon in SO- (p < 0.01) and in PH-rats (p < 0.001). At 1 month, colonic Enterococci decreases compared to control (p < 0.001) and SO-rats (p < 0.01). These intestinal microfloral changes are associated with bacterial translocation to mesenteric lymph nodes at 48 h (50%; p = 0.004) and 1 month (100%; p < 0.001) of postoperative evolution in PH-rats.

CONCLUSIONS

The enlargement of the stenosed portal tract related to triple partial portal vein ligation in the rat, since it increases the resistance to the portal blood flow, may be a key factor involved in one of the pathological consequences of portal hypertension, as is bacterial translocation to mesenteric lymph nodes.

Neuronal nitric oxide inhibits intestinal smooth muscle growth

Hyperplasia of smooth muscle contributes to the thickening of the intestinal wall that is characteristic of inflammation, but the mechanisms of growth control are unknown. Nitric oxide (NO) from enteric neurons expressing neuronal NO synthase (nNOS) might normally inhibit intestinal smooth muscle cell (ISMC) growth, and this was tested in vitro. In ISMC from the circular smooth muscle of the adult rat colon, chemical NO donors inhibited [(3)H]thymidine uptake in response to FCS, reducing this to baseline without toxicity. This effect was inhibited by the guanylyl cyclase inhibitor ODQ and potentiated by the phosphodiesterase-5 inhibitor zaprinast. Inhibition was mimicked by 8-bromo (8-Br)-cGMP, and ELISA measurements showed increased levels of cGMP but not cAMP in response to sodium nitroprusside. However, 8-Br-cAMP and cilostamide also showed inhibitory actions, suggesting an additional role for cAMP. Via a coculture model of ISMC and myenteric neurons, immunocytochemistry and image analysis showed that innervation reduced bromodeoxyuridine uptake by ISMC. Specific blockers of nNOS (7-NI, NAAN) significantly increased [(3)H]thymidine uptake in response to a standard stimulus, showing that nNOS activity normally inhibits ISMC growth. In vivo, nNOS axon number was reduced threefold by day 1 of trinitrobenzene sulfonic acid-induced rat colitis, preceding the hyperplasia of ISMC described earlier in this model. We conclude that NO can inhibit ISMC growth primarily via a cGMP-dependent mechanism. Functional evidence that NO derived from nNOS causes inhibition of ISMC growth in vitro predicts that the loss of nNOS expression in colitis contributes to ISMC hyperplasia in vivo.

iNOS activity is necessary for the cytotoxic and immunogenic effects of doxorubicin in human colon cancer cells

BACKGROUND

Doxorubicin is one of the few chemotherapeutic drugs able to exert both cytotoxic and pro-immunogenic effects against cancer cells. Following the drug administration, the intracellular protein calreticulin is translocated with an unknown mechanism onto the plasma membrane, where it triggers the phagocytosis of tumour cells by dendritic cells. Moreover doxorubicin up-regulates the inducible nitric oxide (NO) synthase (iNOS) gene in cancer cells, leading to huge amounts of NO, which in turn acts as a mediator of the drug toxicity and as a chemosensitizer agent in colon cancer. Indeed by nitrating tyrosine on the multidrug resistance related protein 3, NO decreases the doxorubicin efflux from tumour cells and enhances the drug toxicity. It is not clear if NO, beside playing a role in chemosensitivity, may also play a role in doxorubicin pro-immunogenic effects. To clarify this issue, we compared the doxorubicin-sensitive human colon cancer HT29 cells with the drug-resistant HT29-dx cells and the HT29 cells silenced for iNOS (HT29 iNOS-).

RESULTS

In both HT29-dx and HT29 iNOS- cells, doxorubicin did not induce NO synthesis, had a lower intracellular accumulation and a lower toxicity. Moreover the drug failed to promote the translocation of calreticulin and the phagocytosis of HT29-dx and HT29 iNOS-cells, which resulted both chemoresistant and immunoresistant. However, if NO levels were exogenously increased by sodium nitroprusside, the chemosensitivity to doxorubicin was restored in HT29 iNOS-cells. In parallel the NO donor per se was sufficient to induce the exposure of calreticulin and to increase the phagocytosis of HT29 iNOS- cells by DCs and their functional maturation, thus mimicking the pro-immunogenic effects exerted by doxorubicin in the parental drug-sensitive HT29 cells.

CONCLUSION

Our data suggest that chemo- and immuno-resistance to anthracyclines are associated in colon cancer cells and rely on a common mechanism, that is the inability of doxorubicin to induce iNOS. Therefore NO donors might represent a promising strategy to restore both chemosensitivity and immunosensitivity to doxorubicin in resistant cells.

Wnt pathway-related gene expression in inflammatory bowel disease

The purpose of this study was to examine the expression of Wnt pathway-related genes in patients with ulcerative colitis (UC). RNA from colonoscopic biopsies from noninflammatory bowel disease (non-IBD) subjects and UC patients were obtained and examined with a Wnt-specific microarray for the expression of Wnt pathway-related genes. Paired samples from uninflamed and inflamed areas of the colon were obtained for the UC patients. WNT2B, WNT3A, WNT5B, WNT6, WNT7A, WNT9A, and WNT11 exhibited significantly increased expression in UC compared to non-IBD patients. Frizzled 3 (FZD3) and FZD4 exhibited significantly increased expression, and FZD1 and FZD5 exhibited significantly decreased expression in UC patients. Genes with increased expression in inflamed mucosa included DKK4, DVL2, SOX17, and COL1A1. There was no difference in the expression of a panel of Wnt target genes. The expression of inducible nitric oxide synthase (INOS) was variably influenced by inflammation. Significant differences in extracellular and cell-surface components of the Wnt pathway exist in the colonic mucosa of patients with UC compared with non-IBD patients, which may influence the strength or specificity of Wnt signaling. In inflammation, inhibitory components of the Wnt pathway exhibit increased expression, but no changes in Wnt pathway target gene expression are seen. The role and complex regulation of Sox17 and iNOS in IBD warrant further investigation.

The nitric oxide donor LA-419 [S-(6-Nitro-oxi-hexahydro-furo[3,2-b]furan-3-1-il)thioacetate] prevents intestinal dysmotility, bacterial translocation, and inflammation in a rat model of enteritis

Indomethacin induces a chronic model of inflammatory bowel disease (IBD) characterized by spontaneous relapses of inflammation, bacterial translocation, and long-lasting motor disturbances derived from cyclical up-regulated inducible nitric-oxide synthase (iNOS) and sustained down-regulated neuronal NOS (nNOS). The aims of this study were to evaluate whether LA-419 [S-(6-nitro-oxi-hexahydro-furo[3,2-b]furan-3-1-il)thioacetate], a NO-donor drug, could re-establish the normal expression of NOS and, hence, prevent the development of intestinal dysmotility, bacterial translocation, and relapses of inflammation associated to this model. Enteritis was induced in rats by administration of indomethacin with and without treatment with a novel NO-donor: LA-419 (0.5 mg/ml in the drinking water). Inflammatory reaction was evaluated by measuring blood leukocytes, serum tumor necrosis factor, and tissue myeloperoxidase. Intestinal motor activity was evaluated using strain-gauges. Ileal expression of iNOS and nNOS mRNA was determined by reverse transcription-polymerase chain reaction. Bacterial translocation was evaluated in cultures from mesenteric lymph nodes. The indomethacin-induced acute inflammatory reaction was associated with a rise in blood leukocytes and tumor necrosis factor. In the chronic stage, blood leukocyte monitoring allowed the selection of animals in active and inactive phases. Active phase was associated with iNOS up-regulation, high myeloperoxidase levels, hypomotility, and bacterial translocation. In contrast, inactive phase was associated with hypermotility and absence of bacterial translocation. LA-419 treatment restored nitric-oxide synthase isoenzyme expression and prevented the oscillation of both inflammatory and motor parameters that could be cyclically observed in inflamed rats. LA-419 also prevented intestinal dysmotility, bacterial translocation, and relapses of intestinal inflammation. LA-419 might be a novel therapeutic approach to prevent acute inflammatory relapses in patients with IBD.

Influence of the inducible nitric oxide synthase gene (NOS2A) on inflammatory bowel disease susceptibility

The great amount of nitric oxide (NO) produced by the inducible isoform of NO synthase (iNOS) exerts deleterious effects, and iNOS expression is raised in the colonic mucosa of inflammatory bowel disease (IBD) patients. This is the first association analysis of polymorphisms within the NOS2A extended gene with IBD susceptibility. We analyzed 336 patients of Crohn's disease (CD), 355 of ulcerative colitis (UC), and 536 healthy controls from a Spanish population. We tested a (CCTTT)n microsatellite, a (-/TAAA) insertion, and two single nucleotide polymorphisms (SNPs) flanking them (rs2779251 and rs2779248) in the NOS2A promoter, together with two SNPs in the coding region: one within exon 10, D385D (rs1137933), and another mapping to exon 16, S608L (rs2297518). Analysis of these markers evidenced differences among IBD patients and healthy controls. Allele (CCTTT) 13 is related to higher UC risk (p = 0.001; odds ratio [OR] [95% confidence interval, CI] = 1.64 [1.20-2.23]). Carriers of minor alleles of the two promoter SNPs analyzed showed an association with UC predisposition, and common allele homozygotes of the two exonic SNPs were more frequent among CD patients than among controls. Concordantly, one out of the three haplotypes carrying both exonic risk alleles was found to increase CD susceptibility (p = 0.007; OR [95%CI] = 1.74 [1.13-2.67]). Therefore, the NOS2A gene seems to be involved in IBD aetiology.

Stimulation of voltage-dependent Ca2+ channels by NO at rat myenteric neurons

The aim of the present study was to characterize the action of the neurotransmitter NO on rat myenteric neurons. A NO donor such as GEA 3162 (10(-4) mol/l) induced an increase in the intracellular Ca2+ concentration as indicated by an increase in the fura 2 ratio in ganglia loaded with this Ca2+-sensitive fluorescent dye. The effect of GEA 3162 was strongly reduced in the absence of extracellular Ca2+, suggesting an influx of Ca2+ from the extracellular space evoked by NO. A similar nearly complete inhibition was observed in the presence of Ca2+ channel blockers such as Ni2+ (5 x 10(-4) mol/l) or nifedipine (10(-6) mol/l). Whole cell patch-clamp recordings confirmed the activation of voltage-dependent Ca2+ channels, measured as inward current carried by Ba2+, by the NO donor. The peak Ba2+-carried inward current increased from -100 +/- 19 to -185 +/- 34 pA in the presence of sodium nitroprusside (10(-4) mol/l). The consequence was a hyperpolarization of the membrane, which was blocked by intracellular Cs+ and thus most probably reflects the activation of Ca2+-dependent K+ channels. Furthermore, at least two subtypes of NO synthases, NOS-1 (neuronal form) and NOS-3 (endothelial form), were found as transcripts in mRNA isolated from the rat myenteric ganglia. The expression of these NO synthases was confirmed immunohistochemically. These observations suggest that NO, released from nitrergic neurons within the enteric nervous system, not only affects target organs such as smooth muscle cells in the gut but has in addition profound effects on the enteric neurons themselves, the key players in the regulation of many gastrointestinal functions.

Bile synthesis in rat models of inflammatory bowel diseases

BACKGROUND

A broad spectrum of hepatobiliary disorders are found in patients with inflammatory bowel diseases. The aim of the present work was to study interactions between gut and liver in experimental rat models of colitis and small bowel inflammation.

MATERIALS AND METHODS

Colitis was induced either by trinitrobenzene sulphonic acid or dextran sodium sulphate. Small-bowel inflammation was induced by indomethacin. Bile acid secretion, bile acid pool, and cholesterol 7-alpha hydroxylase were studied. Cholesterol 7-alpha hydroxylase protein expression was analysed in the microsomal liver fraction. As portal mediators released form the inflamed gut we measured lipopolysaccharide, tumour necrosis factor-alpha and interleukin-1beta in portal serum. The hepatic inflammatory response was evaluated by binding activity of nuclear factor-kappaB, activator protein-1 and alpha-2-macroglobulin.

RESULTS

Increased bile acid secretion, total bile acid content in gut and liver (bile acid pool size), and hepatic cholesterol 7-alpha hydroxylase protein and mRNA levels were found in the two colitis models associated with only a minor hepatic acute phase and cytokine response. In contrast, during indomethacin-induced small-bowel inflammation bile acid secretion, pool size, and cholesterol 7-alpha hydroxylase decreased in parallel to a strong hepatic cytokine and acute phase response.

CONCLUSIONS

Colitis without portal cytokine release and acute phase reaction shows an induction of bile acid secretion, pool size, and cholesterol 7-alpha hydroxylase. In contrast, intestinal inflammation after indomethacin treatment is associated with an acute phase response and a repression of bile acid synthesis.

Correlation between cyclical epithelial barrier dysfunction and bacterial translocation in the relapses of intestinal inflammation

BACKGROUND

Although several factors have been implicated in the pathogenesis of inflammatory bowel disease (IBD), the mechanisms underlying the recurrent relapses have not yet been clarified. We hypothesized that epithelial barrier dysfunction, associated with intestinal motor disturbances, could play a key role in exacerbation of inflammatory illness due to an increased uptake of luminal antigen and bacterial translocation.

METHODS

Indomethacin administration to rats induced a long-lasting oscillation of active and quiescent phases of inflammation associated with phases of hypo and hypermotility. Rats selected at either active or quiescent phase and from 2 to 60 days after indomethacin treatment were used. Short-circuit current; conductance and HRP flux were evaluated in small intestinal segments mounted in Ussing Chambers. Enterocyte endosomes containing HRP and ultrastructural damage were assessed by electron microscopy. Bacterial translocation was determined by cultures from mesenteric lymph nodes.

RESULTS

Rats with induced enteritis in both phases demonstrated a long-lasting increase of epithelial paracellular permeability. In contrast, transcellular permeability was only disturbed during the active phases, coinciding with bacterial translocation and the increase in inflammatory parameters. Furthermore, although mithochondrial damage was observed throughout the inflammatory state, alterations were worse during the active phase.

CONCLUSIONS

The sustained enhancement of paracellular permeability could facilitate the constant passage of luminal antigens through the mucosa, and hence, be the basis for chronicity. By contrast, transcellular permeability only increases during the active phases, when hypomotility and bacterial translocation are also present, suggesting this factor may play a critical role in the course of acute relapses in IBD.

Characterization of ileal dendritic cell distribution in a rat model of acute and chronic inflammation

We examined ileal dendritic cell (DC) subpopulations in a rat model of indomethacin-induced enteritis to determine changes in phenotype and distribution associated with increased mucosal permeability during acute and chronic stages of inflammation. Sprague-Dawley rats were treated with indomethacin (7.5 mg/kg subcutaneously, 2 injections 48 h apart). Animals were killed at day 4 (acute stage) or at day 15 or 30 (chronic stages); control rats were injected with saline. DC distribution was evaluated by immunohistochemistry for CD103, CD11b, CD83, and CD163; inflammation was assessed by light microscopy; and permeability was determined by flux of horseradish peroxidase in Ussing chambers. In controls, both immature DC subpopulations, CD103+CD11b+CD163-CD83- and CD103+CD11b-CD163-CD83-, were observed in the lamina propria, and the CD11b- population also was present in Peyer's patches. In acute inflammation, permeability was increased (P<0.01), and inflamed areas with or without ulcers were observed. CD103+ and CD11b+ (CD83-) DCs were absent from inflamed areas, reduced in noninflamed tissues, but present in Peyer's patches. In the chronic stage at day 15, CD103+ and CD11b+ cells were located in inflamed and noninflamed areas and in Peyer's patches. In addition, CD83+ DCs were detected in inflamed areas. At day 30, when we observed a complete microscopic resolution of inflammation, numbers of CD103+ and CD11b+ DCs were increased, and there were CD83+ DCs beneath the epithelial cell layer. We conclude that antigen uptake in acute inflammation may activate resident immature DCs, inducing their migration to lymphoid tissue where they mature and then return to the intestine to play a role in the local inflammatory response.