alpha-Phenyl-N-tert-butylnitrone provides protection from dextran sulfate sodium-induced colitis in mice

Antioxidants as Protection against Reactive Oxidative Stress in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) belongs to a group of chronic diseases characterised by periods of exacerbation and remission. Despite many studies and observations, its aetiopathogenesis is still not fully understood. The interactions of genetic, immunological, microbiological, and environmental factors can induce disease development and progression, but there is still a lack of information on these mechanisms. One of the components that can increase the risk of occurrence of IBD, as well as disease progression, is oxidative stress. Oxidative stress occurs when there is an imbalance between reactive oxygen species (ROS) and antioxidants. The endogenous and exogenous components that make up the body's antioxidant defence can significantly affect IBD prophylaxis and reduce the risk of exacerbation by neutralising and removing ROS, as well as influencing the inflammatory state.

Pathomechanisms of Oxidative Stress in Inflammatory Bowel Disease and Potential Antioxidant Therapies

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease whose incidence has risen worldwide in recent years. Accumulating evidence shows that oxidative stress plays an essential role in the pathogenesis and progression of IBD. This review highlights the generation of reactive oxygen species (ROS) and antioxidant defense mechanisms in the gastrointestinal (GI) tract, the involvement of oxidative stress signaling in the initiation and progression of IBD and its relationships with genetic susceptibility and the mucosal immune response. In addition, potential therapeutic strategies for IBD that target oxidative stress signaling are reviewed and discussed. Though substantial progress has been made in understanding the role of oxidative stress in IBD in humans and experimental animals, the underlying mechanisms are still not well defined. Thus, further studies are needed to validate how oxidative stress signaling is involved in and contributes to the development of IBD.

Lipid hydroperoxide-derived modification of proteins in gastrointestinal tract

Role of lipid peroxidation in the pathogenesis of gastrointestinal diseases has been evaluated by measuring the tissue levels of lipid peroxides as thiobarbituric acid-reactive substances in the animal models as well as human. Recently, N (ε)-(hexanoyl)lysine (HEL) and 4-hydroxy-2-nonenal (HNE) are recognized as reliable and sensitive biomarkers for the early phase and the late phase of lipid peroxidation, respectively. The presence of HNE- and HEL-modified proteins has been demonstrated in in vivo models of several gastrointestinal diseases. In the present review, we introduced HNE-modification of TRPV1 channel in esophageal epithelial cells, HEL-modification of tropomyosin 1 (TMP1) in gastric cancer cells, and HEL-modification of gastrokine 1 in the healing of gastric ulcer.

Inflammatory bowel disease: mechanisms, redox considerations, and therapeutic targets

Oxidative stress is thought to play a key role in the development of intestinal damage in inflammatory bowel disease (IBD), because of its primary involvement in intestinal cells' aberrant immune and inflammatory responses to dietary antigens and to the commensal bacteria. During the active disease phase, activated leukocytes generate not only a wide spectrum of pro-inflammatory cytokines, but also excess oxidative reactions, which markedly alter the redox equilibrium within the gut mucosa, and maintain inflammation by inducing redox-sensitive signaling pathways and transcription factors. Moreover, several inflammatory molecules generate further oxidation products, leading to a self-sustaining and auto-amplifying vicious circle, which eventually impairs the gut barrier. The current treatment of IBD consists of long-term conventional anti-inflammatory therapy and often leads to drug refractoriness or intolerance, limiting patients' quality of life. Immune modulators or anti-tumor necrosis factor α antibodies have recently been used, but all carry the risk of significant side effects and a poor treatment response. Recent developments in molecular medicine point to the possibility of treating the oxidative stress associated with IBD, by designing a proper supplementation of specific lipids to induce local production of anti-inflammatory derivatives, as well as by developing biological therapies that target selective molecules (i.e., nuclear factor-κB, NADPH oxidase, prohibitins, or inflammasomes) involved in redox signaling. The clinical significance of oxidative stress in IBD is now becoming clear, and may soon lead to important new therapeutic options to lessen intestinal damage in this disease.

Identification of inflammation-related proteins in a murine colitis model by 2D fluorescence difference gel electrophoresis and mass spectrometry

BACKGROUND AND AIMS

The aim of this study was to identify new intestinal proteins potentially associated with acute inflammation using proteomic profiling of an in vivo mice model of ulcerative colitis.

METHODS

2D fluorescence difference gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization time-of-flight spectrometer (MALDI-TOF) peptide mass fingerprinting were used to determine differentially expressed proteins between normal and inflamed intestinal mucosa. Acute colitis was induced by 8.0% dextran sodium sulfate (DSS) given p.o. for 7 days.

RESULTS

Among a total of seven protein spots showing differential expression, we identified five different proteins, of which two were upregulated and three downregulated in colitis in comparison to normal mucosa, using the MASCOT search engine. 3-Hydroxy-3-methylglutaryl-coenzyme A synthase 2 and serpin b1a were upregulated proteins, and protein disulfide-isomerase A3, peroxiredoxin-6 and vimentin were identified as downregulated proteins.

CONCLUSION

These identified proteins may be responsible for the development of the intestinal inflammation. 2D-DIGE and MALDI-TOF mass spectrometry are useful in the search for the differentially expressed proteins.

Alpha-phenyl-N-tert-butylnitrone attenuates hyperoxia-induced lung injury by down-modulating inflammation in neonatal rats

This study was done to determine whether alpha -phenyl-N-tert-butylnitrone (PBN), a spin-trapping agent possessing significant anti-inflammatory capabilities, could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague-Dawley rat pups were subjected to 14 days of hyperoxia (> 90% oxygen) within 10 hours after birth. PBN treatment, given 100 mg/kg intraperitoneally daily throughout the experiment, significantly attenuated hyperoxia-induced lung pathology, such as decreased radial alveolar count, increased mean linear intercept, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling-positive cells. Hyperoxia-induced activation of nicotinamide adenine dinucleotide phosphate oxidase that is responsible for superoxide anion production, as evidenced by up-regulation and membrane translocation of p67phox, and the inflammatory responses, such as increased mRNA expression of tumor necrosis factor-alpha, interleukin-6, and transforming growth factor-beta, were also significantly attenuated with PBN treatment. In summary, a spin-trapping agent PBN significantly attenuated hyperoxia-induced lung injury by down-regulating the inflammatory responses in neonatal rats.

Effects of N-acetylcysteine plus mesalamine on prostaglandin synthesis and nitric oxide generation in TNBS-induced colitis in rats

The aim of the present studies was to examine mechanisms by which the rectally administered combination of N-acetylcysteine (NAC) plus mesalamine (5-ASA) affects inducers of inflammation to promote mucosal healing and reduce tissue inflammation in chemically (trinitrobenzene sulfonic acid, TNBS) induced colitis in rats. Experimental findings demonstrate that dual therapy with NAC plus 5-ASA was superior to individual agents in reducing histological measures of colitis. NAC alone and in combination with 5-ASA suppressed COX2 gene expression and prostaglandin E(2) (PGE(2)) levels to control values. Furthermore, NAC plus 5-ASA reduced nitrate generation, an expression of inducible nitric oxide synthase (iNOS) activity, to basal levels and these results were significantly lower than those observed with either NAC or 5-ASA alone. In conclusion, these results indicate that NAC plus 5-ASA exerts therapeutic benefit, in part by countering the actions of PGE(2) and the deleterious effects of oxidative and nitrosative stress induced by TNBS colitis.

Luminal antioxidants enhance the effects of mesalamine in the treatment of chemically induced colitis in rats

Previous experiments in rats with chemically induced colitis have shown that the antioxidant N-acetylcysteine plus mesalamine (5-ASA) exerted a significantly greater therapeutic effect in promoting mucosal healing when compared to either agent alone. The aims of the present study were to compare the effects of three antioxidants plus mesalamine vs. 5-ASA alone in treatment of colitis induced by trinitrobenzene sulfonic acid (TNBS) in rats.

METHODS

Three days following induction of TNBS colitis, rats received 8 days of rectal therapy with 5-ASA, or 5-ASA plus vitamin C (ascorbic acid), 5-ASA plus phenyl butylnitrone (PBN) and 5-ASA plus vitamin E (alpha-tocopherol). Distal colonic tissues were examined for microscopic colitis and myeloperoxidase (MPO) activity.

RESULTS

Global assessments of microscopic colitis induced by TNBS indicated that 5-ASA alone significantly changed colonic injury by -31%. Combination therapy with ascorbic acid plus 5-ASA or alpha-tocopherol plus 5-ASA caused further significant change in TNBS colitis by -65 and -82%, respectively. Each of these values was significantly below scores observed with 5-ASA as monotherapy. Reduction in colitis with PBN plus 5-ASA was not different from 5-ASA alone. MPO activity was decreased significantly in response to monotherapy with 5-ASA and each of the antioxidants plus 5-ASA when compared to TNBS. alpha-Tocopherol plus 5-ASA, however, was the only treatment strategy that reduced significantly MPO activity below that recorded for 5-ASA alone. In conclusion, our results indicate that antioxidants other than N-acetylcysteine significantly enhance the therapeutic effectiveness of 5-ASA in the treatment of TNBS colitis. alpha-Tocopherol plus 5-ASA exerted profound anti-inflammatory and reparative effects upon colitis induced by TNBS.

Neuroprotection of α-phenyl-n-tert-butyl-nitrone on the neonatal white matter is associated with anti-inflammation

Our previous study has demonstrated that alpha-phenyl-tert-butyl-nitrone (PBN) provided neuroprotection to the neonatal white matter following cerebral hypoxia-ischemia (HI). Free radical scavenging was involved in the neuroprotection of PBN. To investigate if other mechanisms contribute to the neuroprotection of PBN, postnatal day 4 SD rats were subjected to bilateral common carotid artery ligation, followed by 8% oxygen exposure for 20min. A single dose of PBN (100mg/kg, i.p.) was given prior to the hypoxic exposure. Expression of inflammatory cytokines: interleukin-1beta (IL-1beta), inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) was determined by RT-PCR, ELISA and immunohistochemistry. Activation of transcriptional factor nuclear factor-kappa B (NF-kappaB) was measured by ELISA. PBN significantly inhibited HI-induced up-regulation of IL-1beta, TNF-alpha and iNOS mRNA expression at 4h following HI. PBN treatment also reduced the brain concentration of IL-1beta significantly and decreased the number of IL-1beta- or iNOS-expressing cells in the white matter area at 12h following HI. Moreover, PBN suppressed the HI-induced NF-kappaB activation at 1h after HI. The overall results indicate that besides free radical scavenging, anti-inflammation might partly contribute to the neuroprotection afforded by PBN on neonatal white matter following cerebral HI.

Reduced neuronal injury after treatment with NG-nitro-L-arginine methyl ester (L-NAME) or 2-sulfo-phenyl-N-tert-butyl nitrone (S-PBN) following experimental brain contusion

OBJECTIVE

Nitric oxide (NO) and oxygen free radicals are implicated in the pathophysiology of traumatic brain injury (TBI). Peroxynitrite formation from NO and superoxide contributes to secondary neuronal injury but the neuroprotective effects of nitric oxide synthase (NOS)-inhibitors have been contradictory. This study was undertaken to examine whether PTtic administration of the (NOS)-inhibitor N-nitro-l-arginine methyl ester (L-NAME), and a combination of L-NAME and the nitrone radical scavenger 2-sulfo-phenyl-N-tert-butyl nitrone (S-PBN) favorable affects neuronal injury in a model of TBI.

METHODS

A weight-drop model of TBI was used. The animals received L-NAME, S-PBN or a combination of the drugs 15 minutes prothrombin time (PT) and sacrificed after 24 hours or six days. NOS activity was measured by the conversion of L-[U-C]arginine to L-[U-C]citrulline. Peroxynitrite formation, cellular apoptosis, neuronal degeneration and survival were assessed by nitrotyrosine-, TUNEL-, Fluoro-Jade- and NeuN-stainings.

RESULTS

eNOS and nNOS activity was significantly reduced in animals that received L-NAME alone or the combination with S-PBN. iNOS activity or iNOS immunoreactivity was not affected. All treatments significantly reduced neuronal degeneration and nitrotyrosine immunoreactivity at 24 hours and increased neuronal survival at six days PT. No differences were detected between L-NAME and L-NAME + S-PBN groups.

CONCLUSION

NO from NOS contributes to secondary neuronal injury in this TBI-model. PTtic treatment does not inhibit early beneficial NO-related effects. L-NAME and S-PBN limit peroxynitrite formation, promoting neuronal survival. The combination of L-NAME and S-PBN was neuroprotective; surprisingly no additive effects were found on nitrotyrosine formation, apoptosis or neuronal survival.

Antioxidant therapy with N-acetylcysteine plus mesalamine accelerates mucosal healing in a rodent model of colitis

The aims of this study were to examine the ability of the antioxidant N-acetylcysteine (NAC) and mesalamine (5-ASA) alone and in combination to affect TNBS-induced colitis in rat. Three days following induction of TNBS colitis rats were randomized to receive daily intracolonic treatment with NAC, 5-ASA, and NAC plus 5-ASA for 5 or 8 days. At the end of the treatment period macroscopic and microscopic colonic injuries were scored. Myeloperoxidase (MPO) activity and cytokine gene expression were measured in colonic tissues. Results indicated that treatment with NAC plus 5-ASA caused a significantly greater reduction in colonic injury than either agent alone. Furthermore, combination therapy inhibited significantly MPO activity and inflammatory cytokine gene expression in the distal colon of TNBS-treated animals. The beneficial effects of NAC plus 5-ASA on reduction of colonic injury and promotion of healing were most evident after 8 days of treatment.

Partially hydrolyzed guar gum down-regulates colonic inflammatory response in dextran sulfate sodium-induced colitis in mice

Partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber produced by a controlled partial enzymatic hydrolysis of guar gum beans, has various physiological actions. The aim of the present study was to elucidate the beneficial effects of PHGG on colonic mucosal damage and on the inflammatory response in a dextran sulfate sodium (DSS) colitis model. After 2 weeks of prefeeding of PHGG, acute colitis was induced with 8% DSS in female BALB/c mice. Colonic mucosal inflammation was evaluated clinically, biochemically and histologically. Mucosal protein contents and mRNA levels of tumor necrosis factor-alpha (TNF-alpha) were determined by immunoassay and reverse transcription polymerase chain reaction. Disease activity scores determined by weight loss, stool consistency and blood in stool in DSS-treated mice were significantly lower in the PHGG-treated mice compared with the control mice. Shortening of the colon was significantly reversed by PHGG. Histological study also showed a reduced infiltration of inflammatory cells, especially neutrophils, and mucosal cell disruption in PHGG-treated mice compared with the control mice. The increases in tissue-associated myeloperoxidase activity and thiobarbituric acid-reactive substances after DSS administration were both significantly inhibited by pretreatment with PHGG. Partially hydrolyzed guar gum also inhibited increases in intestinal TNF-alpha protein and mRNA expression after DSS administration, respectively. These results suggest that chronic ingestion of PHGG prevents the development of DSS-induced colitis in mice via the inhibition of mucosal inflammatory response.

Alpha phenyl-tert-butyl nitrone (PBN) protects syngeneic marrow transplant recipients from the lethal cytokine syndrome occurring after agonistic CD40 antibody administration

Administration of agonistic monoclonal antibodies or recombinant cytokines is a potential approach to enhance antitumor immunity in bone marrow (BM) transplant recipients, but is complicated by toxicity due to proinflammatory cytokine-mediated vital organ damage. We used a murine syngeneic bone marrow transplant (BMT) model, in which administration of anti-CD40 antibody early after BMT results in overproduction of interleukin-12 (IL-12) and interferon-γ (IFN-γ), and lethal gut toxicity to examine the protective effect of the spin trap inhibitor, alpha phenyl-tert-butyl nitrone (PBN). Administration of PBN protected transplant recipients from mortality by significantly attenuating gut toxicity, but did not effect a reduction in the levels of proinflammatory cytokines (IL-12, IFN-γ, tumor necrosis factor α [TNF-α], or nitrate/nitrite). Moreover, PBN did not compromise anti-CD40 antibody-mediated antitumor effects in a nontransplantation lymphoma model. Collectively, these data suggest that PBN administration may represent a novel approach for reduction of toxicity without compromise of antitumor effects resulting from administration of therapeutic antibodies in both transplantation and nontransplantation settings. (Blood. 2005;105:428-431)

Oxidative stress and delayed-onset muscle damage after exercise

Reactive oxygen species (ROS) produced during exercise may be involved in delayed-onset muscle damage related to inflammation. To investigate this hypothesis, we studied whether oxidative stress increases nuclear translocation of nuclear factor-kappaB and chemokine expression in skeletal muscle using myotube L6 cells. We also assessed whether prolonged acute exercise could increase these parameters in rats. In L6 cells, H(2)O(2) induced nuclear translocation of p65 and increased the expression of cytokine-induced neutrophil chemoattractant-1 (CINC-1) and monocyte chemoattractant protein-1 (MCP-1), whereas preincubation with alpha-tocopherol limited the increase in these proteins. Sprague Dawley rats were divided into the following groups: rested control, exercised, rested with a high alpha-tocopherol diet, and exercised with a high alpha-tocopherol diet. After 3 weeks of acclimation, both exercise groups ran on a treadmill at 25 m/min for 60 min. Exercise increased nuclear p65, CINC-1, and MCP-1 in gastrocnemius muscle cells, but these changes were ameliorated by the high alpha-tocopherol diet. Increases in myeloperoxidase and thiobarbituric acid-reactive substrates were ameliorated by a high alpha-tocopherol diet, as were the histological changes. Neutrophil activity was not altered by either exercise or a high alpha-tocopherol diet. These results indicate that delayed-onset muscle damage induced by prolonged exercise is partly related to inflammation via phagocyte infiltration caused by ROS and that alpha-tocopherol (an antioxidant) can attenuate such inflammatory changes.

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Pioglitazone, a PPAR-gamma ligand, provides protection from dextran sulfate sodium-induced colitis in mice in association with inhibition of the NF-kappaB-cytokine cascade

Nuclear factor-kappaB-dependent up-regulation of inflammatory cytokines occurs in inflammatory bowel disease. We investigated the effect of pioglitazone, a peroxisome proliferator-activated receptor-gamma ligand, on dextran sulfate sodium-induced colonic mucosal injury and inflammation in mice. Acute colitis was induced in female mice receiving 0, 1, 3, and 10 mg/kg i.p. of pioglitazone daily. Colonic mucosal inflammation was evaluated chemically and histologically. Thiobarbituric acid-reactive substances and tissue-associated myeloperoxidase activity were measured in intestinal mucosa as indices of lipid peroxidation and neutrophil infiltration, respectively. Colonic mRNA expression of pro-inflammatory cytokines and inducible nitric oxide synthase was measured by reverse transcription-PCR and nuclear factor-kappaB activation was evaluated by electrophoretic mobility shift assay. Dextran sulfate sodium administration resulted in decreases in body weight and colon length and increases in lipid peroxide and neutrophil accumulation of the intestine. In contrast, co-administration with pioglitazone prevented these changes. Transcripts coding for pro-inflammatory cytokines and inducible nitric oxide were expressed in high levels after the development of colitis, and pioglitazone markedly reduced mRNA expression of these genes. DNA binding activity of nuclear factor-kappaB was markedly increased, whereas in pioglitazone co-treated intestines the effect was significantly reduced. These data suggest that peroxisome proliferator-activated receptor-gamma may be a novel therapeutic target for the therapy of inflammatory bowel disease.

Enhanced intestinal inflammation induced by dextran sulfate sodium in tumor necrosis factor-alpha deficient mice

BACKGROUND AND AIMS

Tumor necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory cytokine thought to be involved in the pathogenesis of inflammatory bowel disease. To further define the role of TNF-alpha in intestinal inflammation, we studied the effects of dextran sulfate sodium (DSS) administration in mice with targeted deletions of TNF-alpha gene.

METHODS

Acute colitis was induced in female TNF-alpha-/- and TNF-alpha+/+ mice by administering 4.5% DSS orally in drinking water for seven days. The colonic mucosal injury and inflammation was evaluated based on body weight changes, total colon length, luminal hemoglobin, and histological findings. Colonic mRNA expression for inducible nitric oxide synthase (iNOS), TNF-alpha, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were measured by reverse transcription polymerase chain reaction (RT-PCR), and nuclear factor kappaB (NF-kappaB) activation was evaluated by electrophoretic mobility shift assay.

RESULTS

In each assessment, colonic injury was significantly aggravated in DSS-treated TNF-alpha-/- mice compared with DSS-treated TNF-alpha+/+ mice. The survival rate of TNF-alpha-/- mice on day seven was 40%; in contrast, all TNF-alpha+/+ mice were alive. Histological study also showed an enhanced infiltration of inflammatory cells, especially neutrophils, and mucosal cell disruption in DSS-treated TNF-alpha-/- mice compared with DSS-treated TNF-alpha+/+ mice. On day seven, mRNA levels of IFN-gamma and IL-4 in the colons of TNF-alpha-/- mice were faint or not detected; in contrast, those of TNF-alpha+/+ mice were detected. Although the expression of iNOS mRNA and luminal nitrite levels were similarly increased in both mice on day seven, this induction was delayed in TNF-alpha-/- mice during the early phase. The degree of NF-kappaB binding activity seemed to be similar between the two types of mice on day seven.

CONCLUSION

DSS-induced inflammation is significantly enhanced in TNF-alpha-/- mice compared to TNF-alpha+/+ mice. These data suggest that persistent and marked blockage of TNF-alpha bioactivity may provide a detrimental effect on acute intestinal inflammation.