Antioxidant properties of aminosalicylates

Effect of the combined administration of vitamin-E and 5-aminosalicylic acid on acrylamide-induced testicular toxicity

Objectives

This study aimed to evaluate the comparative protective antioxidant effect of 5-aminosalicylic acid (5-ASA) and vitamin-E against acrylamide (ACR)-induced testicular toxicity in rats.

Methods

This study was performed at King Fahad Medical Research Centre, Jeddah, KSA. A total of 49 adult Wistar rats (250 ± 20 gm) that were 60 days old were divided into seven groups (control, ACR alone, ACR + 5-ASA, ACR + Vitamin-E, ACR + 5-ASA + Vitamin-E, Vitamin-E alone, 5-ASA alone). Acrylamide [45 mg/kg (bw)/day] and vitamin-E [200 mg/kg (bw)/day] were gavaged orally, and 5-ASA [25 mg/kg (bw)/day] were injected intra-peritoneally for five consecutive days after one day of observation. Rats were sacrificed by cervical dislocation. Histopathology of the testis, enzyme linked immunosorbent assay (ELISA) of testosterone, the lactate dehydrogenase (LDH) assay and a caudal sperm count were performed.

Results

Rats treated with ACR showed signs of aggression and rough coats, with reduced food and water intake. ACR treated rats showed histopathological changes in the form of a sloughed seminiferous epithelium in the tubular lumen with no multinucleated giant cells. Shrinkage of seminiferous tubules with widening of the interstitial space was also observed with atrophy and the shedding of normal mucosa. Our results indicated that maximum protection was conveyed by the combined antioxidant effect of vitamin-E and 5-ASA on testicular histopathology.

Conclusion

We conclude that acrylamide-induced degeneration of seminiferous tubules can be partially reversed by the administration of 5-ASA and vitamin-E and suggests restricting exposure to ACR.

The implications of oxidative stress and antioxidant therapies in Inflammatory Bowel Disease: Clinical aspects and animal models

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disorder characterized by alternating phases of clinical relapse and remission. The etiology of IBD remains largely unknown, although a combination of patient's immune response, genetics, microbiome, and environment plays an important role in disturbing intestinal homeostasis, leading to development and perpetuation of the inflammatory cascade in IBD. As chronic intestinal inflammation is associated with the formation of reactive oxygen and reactive nitrogen species (ROS and RNS), oxidative and nitrosative stress has been proposed as one of the major contributing factor in the IBD development. Substantial evidence suggests that IBD is associated with an imbalance between increased ROS and decreased antioxidant activity, which may explain, at least in part, many of the clinical pathophysiological features of both CD and UC patients. Hereby, we review the presently known oxidant and antioxidant mechanisms involved in IBD-specific events, the animal models used to determine these specific features, and also the antioxidant therapies proposed in IBD patients.

Comparison between 5-aminosalicylic acid (5-ASA) and para-aminosalicylic acid (4-PAS) as potential protectors against Mn-induced neurotoxicity

Manganese (Mn) is an essential metal for biological systems; however, occupational or clinical exposure to high levels of Mn can produce a neurological disorder called manganism. Oxidative stress and neuroinflammation play major roles in the Mn-induced neurodegeneration leading to dysfunction of the basal ganglia. We investigated the toxic effects of MnCl2 in an immortalized rat brain endothelial cell line (RBE4) and the protective effects of the radical scavenging aminosalicylic acids, 5-aminosalicylic acid (5-ASA) and 4-aminosalicylic acid (4-PAS). Mn cytotoxicity was determined with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) activity. A significant decrease in MTT reduction concomitant with increased LDH release was noted in RBE4 cells exposed for 24 h to MnCl2 (600 and 800 μM; p < 0.0001). Our results establish that compared to 4-PAS, 5-ASA has greater efficacy in protecting RBE4 cells from Mn-induced neurotoxicity after preexposure to MnCl2 800 μM (p < 0.0001).

Chronic inflammatory disorders and their redox control: from molecular mechanisms to therapeutic opportunities

A chronic inflammatory disease is a condition characterized by persistent inflammation. A number of human pathologies fall into this category, and a great deal of research has been conducted to learn more about their characteristics and underlying mechanisms. In many cases, a genetic component has been identified, but also external factors like food, smoke, or environmental pollutants can significantly contribute to worsen their symptoms. Accumulated evidence clearly shows that chronic inflammatory diseases are subjected to a redox control. Here, we shall review the identity, source, regulation, and biological activity of redox molecules, to put in a better perspective their key-role in cancer, diabetes, cardiovascular diseases, atherosclerosis, chronic obstructive pulmonary diseases, and inflammatory bowel diseases. In addition, the impact of redox species on autoimmune disorders (rheumatoid arthritis, systemic lupus erythematosus, psoriasis, and celiac disease) and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis) will be discussed, along with their potential therapeutic implications as novel drugs to combat chronic inflammatory disorders.

Effect of fruit extract of Fragaria vesca L. on experimentally induced inflammatory bowel disease in albino rats

Aim:

Ulcerative colitis and Crohn’s disease are chronic recurrent inflammatory bowel disease (IBD) of unknown origin. Oxidative stress is believed to be a key factor in the pathogenesis and perpetuation of the mucosal damage in IBD.

Materials and Methods:

Ethanolic extract of Fragaria vesca (EFFV) fruits was prepared by percolation method and subjected to oral toxicity testing using OECD guidelines. Albino rats were pretreated orally for 5 days with 3% gum acacia in control, EFFV 500 mg/kg in test and 5-aminosalisylic acid (5-ASA) 100 mg/kg in standard groups. Colitis was induced by transrectal administration of 4% acetic acid on 5^th day. All the animals were sacrificed with ether overdose 48 hours after colitis induction, and 10 cm colon segment was resected from proximal end. Colon was weighed (for disease activity index) and scored macroscopically and microscopically after histological staining. Biochemical assessments included myeloperoxidase (MPO) and tissue catalase (CAT), glutathione (GSH) and superoxide dismutase (SOD) measurements. Statistical analysis was done using one-way analysis of variance (ANOVA) followed by Dunnett’s “t” test.

Results:

EFFV showed significant (P < 0.05) prevention of increase in colon weight and disease activity index along with decrease in macroscopic and microscopic lesion score as compared to control group. Significant improvement was observed in the levels of MPO, CAT and SOD, except GSH (P < 0.05). However, the effect of EFFV was significantly less than 5-ASA (P < 0.05).

Conclusions:

EFFV at 500 mg/kg showed significant amelioration of experimentally induced IBD, which may be attributed to its antioxidant and anti-inflammatory properties.

Rectal gel application of Withania somnifera root extract expounds anti-inflammatory and muco-restorative activity in TNBS-induced inflammatory bowel disease

Background

Inflammatory Bowel Disease (IBD) is marked with chronic inflammation of intestinal epithelium driven by oxidative stress. Traditional treatments with plant extracts gained renewed interest due to their ability to ameliorate the multi factorial conditions like inflammation. We investigated the beneficial effects of Withania somnifera in Trinitro Benzyl Sulfonic Acid (TNBS) induced experimental IBD through a rectally applicable formulation.

Methods

The study included (i) preparation of gel formulation from aqueous Withania somnifera root extract (WSRE), (ii) biochemical assays to determine its performance potential, (iii) testing of formulation efficacy in TNBS-induced IBD rat model, and (iv) histo-patholgical studies to assess its healing and muco-regenerative effect in IBD-induced rats. For this purpose, concentration dependant antioxidant activity of the extracts were evaluated using biochemical assays like (a) inhibition of lipid peroxidation, (b) NO scavenging, (c) H₂O₂ scavenging, and (d) ferric reducing power assay.

Results

The extract, at 500 μg/ml, the highest concentration tested, showed 95.6% inhibition of lipid peroxidation, 14.8% NO scavenging, 81.79% H₂O₂ scavenging and a reducing capacity of 0.80. The results were comparable with standard antioxidants, ascorbic acid and curcumin. WSRE treatment positively scored on histopathological parameters like necrosis, edema, neutrophil infiltration. The post treatment intestinal features showed restoration at par with the healthy intestine. In view of these results, gel formulation containing an aqueous extract of W. somnifera, prepared for rectal application was tested for its anti-inflammatory activity in TNBS-induced rat models for IBD. Commercially available anti-inflammatory drug Mesalamine was used as the standard in this assay.

Conclusions

Dose of the rectal gel applied at 1000 mg of WSRE per kg rat weight showed significant muco-restorative efficacy in the IBD-induced rats, validated by histo-pathological studies.

The role and therapeutic potential of prohibitin in disease

Prohibitin 1 (PHB1), a pleiotropic protein in the cell, has been implicated in the regulation of proliferation, apoptosis, transcription, mitochondrial protein folding, and as a cell-surface receptor. This diverse array of functions of PHB1 is attributed to the cell type studied and its subcellular localization. This review discusses recent data that indicate a diverse role of PHB1 in disease pathogenesis and suggest that targeting PHB1 may be a potential therapeutic option for treatment of diseases including cancer, inflammatory bowel disease, insulin resistance/type 2 diabetes, and obesity. These diseases are associated with increased oxidative stress and mitochondrial dysfunction and therefore, the role of PHB1 in both responses will also be discussed.

Differential immune and genetic responses in rat models of Crohn's colitis and ulcerative colitis

Crohn's disease and ulcerative colitis are clinically, immunologically, and morphologically distinct forms of inflammatory bowel disease (IBD). However, smooth muscle function is impaired similarly in both diseases, resulting in diarrhea. We tested the hypothesis that differential cellular, genetic, and immunological mechanisms mediate smooth muscle dysfunction in two animal models believed to represent the two diseases. We used the rat models of trinitrobenzene sulfonic acid (TNBS)- and dextran sodium sulfate (DSS)-induced colonic inflammations, which closely mimic the clinical and morphological features of Crohn's disease and ulcerative colitis, respectively. DSS inflammation induced oxidative stress initially in mucosa/submucosa, which then propagated to the muscularis externa to impair smooth muscle function. The muscularis externa showed no increase of cytokines/chemokines. On the other hand, TNBS inflammation almost simultaneously induced oxidative stress, recruited or activated immune cells, and generated cytokines/chemokines in both mucosa/submucosa and muscularis externa. The generation of cytokines/chemokines did not correlate with the recruitment and activation of immune cells. Consequently, the impairment of smooth muscle function in DSS inflammation was primarily due to oxidative stress, whereas that in TNBS inflammation was due to both oxidative stress and proinflammatory cytokines. The impairment of smooth muscle function in DSS inflammation was due to suppression of Gα(q) protein of the excitation-contraction coupling. In TNBS inflammation, it was due to suppression of the α(1C)1b subunit of Ca(v)1.2b channels, CPI-17 and Gα(q). TNBS inflammation increased IGF-1 and TGF-β time dependently in the muscularis externa. IGF-1 induced smooth muscle hyperplasia; both IGF-1 and TGF-β induced hypertrophy. In conclusion, both TNBS and DSS induce transmural inflammation, albeit with different types of inflammatory mediators. The recruitment or activation of immune cells does not correlate directly with the intensity of generation of inflammatory mediators. The inflammatory mediators in TNBS and DSS inflammations target different genes to impair smooth muscle function.

Ion channel remodeling in gastrointestinal inflammation

BACKGROUND

 Gastrointestinal inflammation significantly affects the electrical excitability of smooth muscle cells. Considerable progress over the last few years have been made to establish the mechanisms by which ion channel function is altered in the setting of gastrointestinal inflammation. Details have begun to emerge on the molecular basis by which ion channel function may be regulated in smooth muscle following inflammation. These include changes in protein and gene expression of the smooth muscle isoform of L-type Ca(2+) channels and ATP-sensitive K(+) channels. Recent attention has also focused on post-translational modifications as a primary means of altering ion channel function in the absence of changes in protein/gene expression. Protein phosphorylation of serine/theronine or tyrosine residues, cysteine thiol modifications, and tyrosine nitration are potential mechanisms affected by oxidative/nitrosative stress that alter the gating kinetics of ion channels. Collectively, these findings suggest that inflammation results in electrical remodeling of smooth muscle cells in addition to structural remodeling.

PURPOSE

The purpose of this review is to synthesize our current understanding regarding molecular mechanisms that result in altered ion channel function during gastrointestinal inflammation and to address potential areas that can lead to targeted new therapies.

Neuroinflammation in inflammatory bowel disease

Inflammatory bowel disease is a chronic intestinal inflammatory condition, the pathology of which is incompletely understood. Gut inflammation causes significant changes in neurally controlled gut functions including cramping, abdominal pain, fecal urgency, and explosive diarrhea. These symptoms are caused, at least in part, by prolonged hyperexcitability of enteric neurons that can occur following the resolution of colitis. Mast, enterochromaffin and other immune cells are increased in the colonic mucosa in inflammatory bowel disease and signal the presence of inflammation to the enteric nervous system. Inflammatory mediators include 5-hydroxytryptamine and cytokines, as well as reactive oxygen species and the production of oxidative stress. This review will discuss the effects of inflammation on enteric neural activity and potential therapeutic strategies that target neuroinflammation in the enteric nervous system.

Oxidative stress and pathogenesis of inflammatory bowel disease: an epiphenomenon or the cause?

Crohn's disease (CD) and ulcerative colitis (UC), known as inflammatory bowel disease (IBD), are fairly common chronic inflammatory conditions of the gastrointestinal tract. Although the exact etiology of IBD remains uncertain, dysfunctional immunoregulation of the gut is believed to be the main culprit. Amongst the immunoregulatory factors, reactive oxygen species are produced in abnormally high levels in IBD. Their destructive effects may contribute to the initiation and/or propagation of the disease. We provided an extensive overview on the evidences from animal and human literature linking oxidative stress to IBD and its activity. Moreover, the effects of antioxidant therapy on IBD patients in randomized, controlled trials were reviewed and the need for further studies elaborated. We also summarized the evidence in support for causality of oxidative stress in IBD.

Alterations in Salivary Antioxidants, Nitric Oxide, and Transforming Growth Factor-β1in Relation to Disease Activity in Crohn's Disease Patients

It has been postulated that oxidative stress, nitric oxide (NO), and transforming growth factor beta(1) (TGF- beta(1)) have major roles in the pathophysiology of Crohn's disease (CD). The aim of this study was to determine the salivary levels of total antioxidant capacity (TAC), specific antioxidants (i.e., uric acid, albumin, transferrin, and thiol molecules), lipid peroxidation (LPO), NO, and TGF- beta(1) in CD patients and control subjects and to also investigate their correlation with activity of the disease. Twenty-eight patients with confirmed diagnosis of CD were enrolled and whole saliva samples were obtained. Smokers, diabetics, those who suffered from periodontitis, and those who were consuming antioxidant supplements were excluded from the study. The Crohn's Disease Activity Index (CDAI) was used to determine the severity of the disease. Twenty healthy subjects were also recruited. In CD patients significant reductions in salivary levels of TAC (0.248 +/- 0.145 vs. 0.342 +/- 0.110 mmol/L), albumin (1.79 +/- 0.42 vs. 2.3 +/- 0.2 microg/mL), and uric acid (3.1 +/- 1.4 vs. 4.1 +/- 2.0 mg/dL) were found. TGF-beta(1) was significantly increased in CD patients compared to healthy subjects (3.02 +/- 1.54 vs. 2.36 +/- 0.52 ng/mL). A fourfold increase in NO levels (198.8 +/- 39.9 vs. 50.2 +/- 21.3 micromol/L) along with a fivefold increase in LPO concentration (0.146 +/- 0.064 vs. 0.027 +/- 0.019 micromol/L) was documented in CD patients in comparison to the control group. CDAI significantly correlated with the TAC, LPO, and the interaction between TAC and LPO (r(2) = 0.625, r(2) = 0.8, F-test's P < 0.00005). Saliva of CD patients exhibits an abnormal feature with respect to oxidative stress, NO, and TGF-beta(1). TAC and LPO modify the effect of each other in determination of CD severity, which underlines the importance of oxidative stress in the pathogenesis of CD.

Amelioration of experimental colitis by Astragalus membranaceus through anti-oxidation and inhibition of adhesion molecule synthesis

AIM: To investigate the protective effects of Astragalus membranaceus (Am) against hapten-induced colitis in male Sprague-Dawley rats as well as its underlying mechanism.

METHODS: Experimental colitis was induced in rats by enema administration of 2,4-dinitrobenzene sulfonic acid (DNBS). Rats were either pretreated with Am extract (2 or 4 g/kg, p.o. once daily) starting from 10 d before DNBS enema, or received Am post-treatment (2 or 4 g/kg, p.o. twice daily) on the three consecutive days following DNBS administration. Colonic lesion area and histological damage were determined, while the activities of myeloperoxidase (MPO) and xanthine oxidase, as well as reduced glutathione (GSH) content were measured in the excised colonic tissues. Besides, protein expression of inducible nitrite oxide synthase (iNOS), intercellular adhesion molecule-1 (ICAM-1) and P-selectin was also detected by Western blot analysis.

RESULTS: Our findings had shown that both macroscopic lesion area and histological colonic damage induced by DNBS were significantly reduced by both Am pre- and post-treatments. These were accompanied by attenuation of the elevated colonic MPO activity and downregulation of the iNOS, P-selectin, and ICAM-1 protein expression. Besides, deprivation of colonic GSH level under colitis condition was also preserved.

CONCLUSION: These results demonstrate that Am possesses both preventive and therapeutic potential in experimental colitis. The anti-inflammatory actions involve anti-oxidation along with inhibition of adhesion molecule synthesis in the colonic tissues.

Monochloramine induces acute and protracted colitis in the rat: response to pharmacological treatment

Monochloramine is a powerful oxidative molecule that is produced in inflammatory sites. We investigated the effect of intrarectally administered monochloramine (3.2 mg) in the rat. A single enema induced after 24 h an intense inflammatory reaction characterized by mucosal necrosis, submucosal edema, hemorrhage and colonic thickening, as well as induction of nitric oxide synthase and tumor necrosis factor and an increase in the interferon gamma/interleukin 4 ratio. The inflammatory response peaked 3-5 days after monochloramine administration and then followed a extended recovery phase. At 1 week there was substantial but incomplete mucosal repair, submucosal edema, neutrophil/macrophage infiltration and increased myeloperoxydase and alkaline phosphatase activities. Oxidative stress, as determined by malonyldialdehyde levels, was prominent only in the acute phase (3-5 days). Monochloramine colitis was amenable to pharmacological treatment with sulphasalazine or prednisolone, suggesting that it may be used as an experimental model of inflammatory bowel disease. In conclusion, monochloramine induces acute and protracted colonic inflammation in the rat. Locally produced monochloramine might contribute to the perpetuation of inflammatory bowel disease.

Interferon-gamma and tumor necrosis factor-alpha synergize to induce intestinal epithelial barrier dysfunction by up-regulating myosin light chain kinase expression

Numerous intestinal diseases are characterized by immune cell activation and compromised epithelial barrier function. We have shown that cytokine treatment of epithelial monolayers increases myosin II regulatory light chain (MLC) phosphorylation and decreases barrier function and that these are both reversed by MLC kinase (MLCK) inhibition. The aim of this study was to determine the mechanisms by which interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha regulate MLC phosphorylation and disrupt epithelial barrier function. We developed a model in which both cytokines were required for barrier dysfunction. Barrier dysfunction was also induced by TNF-alpha addition to IFN-gamma-primed, but not control, Caco-2 monolayers. TNF-alpha treatment of IFN-gamma-primed monolayers caused increases in both MLCK expression and MLC phosphorylation, suggesting that MLCK is a TNF-alpha-inducible protein. These effects of TNF-alpha were not mediated by nuclear factor-kappaB. However, at doses below those needed for nuclear factor-kappaB inhibition, sulfasalazine was able to prevent TNF-alpha-induced barrier dysfunction, MLCK up-regulation, and MLC phosphorylation. Low-dose sulfasalazine also prevented morphologically evident tight junction disruption induced by TNF-alpha. These data show that IFN-gamma can prime intestinal epithelial monolayers to respond to TNF-alpha by disrupting tight junction morphology and barrier function via MLCK up-regulation and MLC phosphorylation. These TNF-alpha-induced events can be prevented by the clinically relevant drug sulfasalazine.

Interferon-gamma and tumor necrosis factor-alpha synergize to induce intestinal epithelial barrier dysfunction by up-regulating myosin light chain kinase expression

Numerous intestinal diseases are characterized by immune cell activation and compromised epithelial barrier function. We have shown that cytokine treatment of epithelial monolayers increases myosin II regulatory light chain (MLC) phosphorylation and decreases barrier function and that these are both reversed by MLC kinase (MLCK) inhibition. The aim of this study was to determine the mechanisms by which interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha regulate MLC phosphorylation and disrupt epithelial barrier function. We developed a model in which both cytokines were required for barrier dysfunction. Barrier dysfunction was also induced by TNF-alpha addition to IFN-gamma-primed, but not control, Caco-2 monolayers. TNF-alpha treatment of IFN-gamma-primed monolayers caused increases in both MLCK expression and MLC phosphorylation, suggesting that MLCK is a TNF-alpha-inducible protein. These effects of TNF-alpha were not mediated by nuclear factor-kappaB. However, at doses below those needed for nuclear factor-kappaB inhibition, sulfasalazine was able to prevent TNF-alpha-induced barrier dysfunction, MLCK up-regulation, and MLC phosphorylation. Low-dose sulfasalazine also prevented morphologically evident tight junction disruption induced by TNF-alpha. These data show that IFN-gamma can prime intestinal epithelial monolayers to respond to TNF-alpha by disrupting tight junction morphology and barrier function via MLCK up-regulation and MLC phosphorylation. These TNF-alpha-induced events can be prevented by the clinically relevant drug sulfasalazine.

In vitro comparative assessment of the scavenging activity against three reactive oxygen species of non-steroidal anti-inflammatory drugs from the oxicam and sulfoanilide families

The study of the interaction of non-steroidal anti-inflammatory drugs (NSAIDs) with several reactive oxygen species is of great interest in inflammatory conditions where an uncontrolled release of these potentially damaging intermediates has been documented. This study focused on the scavenging of three species (hydroxyl radical, hydrogen peroxide and hypochlorous acid) with several members of the oxicam family and with the sulfoanilide nimesulide. Reaction with hydroxyl radical was assessed by the modified deoxyribose assay, and rate constants were calculated showing values between 0.8 and 1.1 x 10(10) M(-1) s(-1) for oxicams and of about 0.9 x 10(10) M(-1) s(-1) for nimesulide and ibuprofen. These were consistent with those of the literature but in the same range as those for other NSAIDs and for several thiol-containing molecules. The study of hydrogen peroxide scavenging by the horseradish peroxidase (HRP) assay lacked specificity but no interaction could be evidenced by the glutathione peroxidase assay. The scavenging of hypochlorous acid was finally investigated by the recently developed para-aminobenzoic acid assay which demonstrated better performances for meloxicam (1.7 x 10(4) M(-1) s(-1)) as compared to the other oxicams (tenoxicam: 4.0 x 10(4) M(-1) s(-1), piroxicam: 3.6 x 10(4) M(-1) s(-1), lornoxicam: 4.3 x 10(4) M(-1) s(-1)) and nimesulide (2.3 x 10(3) M(-1) s(-1)). These rate constants were, however, lower than those for thiol-containing molecules and ascorbate. These results suggest that the antioxidant properties of NSAIDs could be influenced by a proper pharmacomodulation as far as the scavenging of hypochlorous acid is concerned while the interest is quite limited for the scavenging of hydroxyl radical.

Effect of 5-aminosalicylic acid on radiation-induced micronuclei in mouse bone marrow

5-Aminosalicylic acid (5ASA), a prescribed drug for ulcerative colitis, is a potent scavenger of oxygen-derived free radicals. The present study was undertaken to ascertain its ability to protect against radiation-induced damage. The drug dose-dependent effect, optimum time of drug administration and radiation dose-dependent effect (0-4 Gy) on in vivo radiation protection against micronuclei induction in polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) were studied in the bone marrow of mice. Intraperitoneal injection of 10-125 mg/kg of the drug 30 min before whole body irradiation with 3 Gy produced a significant reduction in the frequency of micronucleated erythrocytes at 24 h after exposure. The optimum dose for protection without drug toxicity was 25 mg/kg body weight. Injection of 25 mg/kg of the drug 60 or 30 min before or within 15 min after 3 Gy whole body gamma-irradiation resulted in a significant decrease in the radiation-induced PCE and NCE with micronuclei (MPCE and MNCE) and an increase in the ratio of PCE to NCE (P/N), at 24 h post-irradiation. Maximum effect was seen when the drug was administered 30 min before irradiation. Therefore, to study the radiation dose-response, mice were pre-treated with 25 mg/kg of 5ASA 30 min before 1-4 Gy of gamma-irradiation. Radiation increased the MN frequency linearly (r(2)=0.99) with dose. Pre-treatment with 5ASA significantly reduced the MN counts to 40-50% of the radiation (RT) alone values, giving a dose modification factor (DMF) of 2.02 (MPCE) and 2.53 (MNCE). Irradiation resulted in a dose-dependent decline in the P/N ratio at all the doses of radiation studied. 5ASA produced a significant increase in the P/N ratio from that of irradiated controls, at all doses of radiations tested. These results show that 5ASA protect mice against radiation-induced MN formation and mitotic arrest.

Review article: oxidative stress as a pathogenic factor in inflammatory bowel disease--radicals or ridiculous?

Virtually all inflammatory mediators investigated to date seem to be dysregulated in the inflamed intestinal mucosa of patients with inflammatory bowel disease. However, which of these are actually involved in the initiation and perpetuation of intestinal tissue damage is still not fully understood. Amongst these mediators are the reactive oxygen metabolites, produced in large amounts by the massively infiltrating leucocytes. These reactive oxygen metabolites are believed to constitute a major tissue-destructive force and may contribute significantly to the pathogenesis of inflammatory bowel disease. This paper provides a concise overview of reactive oxygen metabolite biochemistry, the types of cell and tissue damage potentially inflicted by them, and the endogenous antioxidants which should prevent these harmful effects. An up-to-date summary of the available human experimental data suggests that reactive oxygen metabolite-mediated injury is important in both the primary and downstream secondary pathophysiological mechanisms underlying intestinal inflammation. Nonetheless, how the individual components of the mucosal antioxidant enzymatic cascade respond to inflammatory conditions is a neglected area of research. This particular aspect of intestinal mucosal oxidative stress therefore merits further study, in order to provide a sound, scientific basis for the design of antioxidant-directed treatment strategies for inflammatory bowel disease patients.

Role of reactive metabolites of oxygen and nitrogen in inflammatory bowel disease

The inflammatory bowel diseases (IBD; Crohn's disease, ulcerative colitis) are a collection of chronic idiopathic inflammatory disorders of the intestine and/or colon. Although the pathophysiology of IBD is not known with certainty, a growing body of experimental and clinical data suggests that chronic gut inflammation may result from a dysregulated immune response to normal bacterial antigens. This uncontrolled immune system activation results in the sustained overproduction of reactive metabolites of oxygen and nitrogen. It is thought that some of the intestinal and/or colonic injury and dysfunction observed in IBD is due to elaboration of these reactive species. This review summarizes the current state-of-knowledge of the role of reactive oxygen species and nitric oxide in the pathophysiology of IBD.

5-Aminosalicylic acid protection against oxidative damage to synaptosomal membranes by alkoxyl radicals in vitro

The antioxidant properties of 5-aminosalicylic acid in vitro were evaluated in a synaptosomal membrane system prepared from gerbil cortical synaptosomes using EPR spin labeling and spectroscopic techniques. MAL-6 (2,2,6,6-tetramethyl-4-maleimidopiperidin-1-oxyl) and 5-NS (5-nitroxide stearate) spin labels were used to assess changes in protein oxidation and membrane lipid fluidity, respectively. Synaptosomal membranes were subjected to oxidative stress by incubation with 1 mM azo-bis(isobutyronitrile) (AIBN) or 1 mM 2,2'-azobis(amidino propane) dihydrochloride (AAPH) at 37 degrees C for 30 minutes. The EPR analyses of the samples showed significant oxidation of synaptosomal proteins and a decrease in membrane fluidity. 5-Aminosalicylic acid also was evaluated by means of FRAP (the ferric reducing ability of plasma) test as a potential antioxidant. 5-Aminosalicylic acid also showed protection against the oxidation in gerbil cortical synaptosomes system caused by AIBN and AAPH. These results are consistent with the notion of antioxidant protection against free radical induced oxidative stress in synaptosomal membrane system by this agent.

Antioxidant activity of 5-aminosalicylic acid against peroxidation of phosphatidylcholine liposomes in the presence of alpha-tocopherol: a synergistic interaction?

Oxidative damage has been implicated in the pathogenesis of inflammatory bowel diseases. 5-Aminosalicylic acid (5-ASA), the anti-inflammatory drug commonly used in the treatment of this condition, has been shown to possess antioxidant properties considered to be of particular importance in the pathologic context of these diseases. However, its action mechanisms are far from being completely elucidated, especially regarding its antioxidant properties in the presence of endogenous antioxidants such as alpha-tocopherol (alpha-T), the major defence system of biomembranes against lipid peroxidation. In this study we investigated the scavenging activity of 5-ASA toward peroxyl radicals generated at different sites of soybean PC liposomes, used as model membranes, either alone or in combination with alpha-T. 5-ASA, separately, shows strong scavenging activity toward peroxyl radicals generated in the aqueous phase by thermal decomposition of 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), inducing a clear concentration-dependent inhibition period, either of oxygen consumption or of conjugated diene hydroperoxides production. HPLC analysis indicates that 5-ASA is consumed, at a constant rate, throughout the reaction, and when the inhibition period is over, the oxidation rate is resumed. On the other hand, apart from a slight decrease in the rate of oxidation, 5-ASA is unable to suppress efficiently lipid peroxidation, when the reaction starts inside the lipid membranes, by thermal decomposition of 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). When 5-ASA is combined with alpha-T, and the oxidation starts in the aqueous phase, an additive inhibitory effect occurs between both compounds. 5-ASA protects efficiently alpha-T against initial attack from AAPH-peroxyl radicals, delaying its consumption. On the other hand, if the reaction starts inside the lipid bilayer, 5-ASA prolongs significantly the inhibitory period produced by alpha-T on the initial rate of oxidation, as measured by oxygen consumption and conjugated diene hydroperoxides. This inhibitory effect points to a synergistic interaction between 5-ASA and alpha-T, since 5-ASA, by itself, is unable to suppress the oxidation reaction. Therefore, 5-ASA reveals an important cooperative effect with alpha-T, either affording an efficient protection to this antioxidant compound, when free radicals are generated in the aqueous site, or potentiating its activity when oxidation is initiated inside the lipid bilayer. Taking into account that the ascorbic acid content decreases significantly in the inflamed mucosa of patients with inflammatory bowel diseases, our data are, certainly, a very important contribution to the knowledge of the anti-inflammatory action of 5-ASA.

Peroxynitrite-induced apoptosis in epithelial (T84) and macrophage (RAW 264.7) cell lines: effect of legume-derived polyphenols (phytolens)

Peroxynitrite (ONOO-) has been proposed as a mediator of gut inflammation and as an inducer of cell death by apoptosis. Phytolens (PHY), a water-soluble extract of polyphenolic antioxidants from nonsoy legumes (Biotics Research Corp, patent pending), was evaluated as a cytoprotective agent in human colonic (T84) and murine macrophage (RAW 264.7) cell lines. In the antioxidant testing, PHY showed a significant free radical scavenging ability against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and superoxide (O2.) radicals with an IC50 of 4.44 and 5.87 microg/ml against DPPH and O2., respectively. Apoptosis (DNA fragmentation) was measured by an ELISA technique. Cells were exposed to oxidative stress by treating them with peroxynitrite (100-300 microM) for 4 h in the presence and absence of PHY. Peroxynitrite elicited a dose-dependent increase in DNA fragmentation in both cell lines compared to the control group receiving decomposed ONOO-. PHY (10, 30, or 50 microg/ml) significantly attenuated the degree of apoptosis in T84 cells induced by ONOO- (P < 0.05). PHY (10-100 microg/ml) did not directly affect T84 cell viability or induce apoptosis after 4 h or overnight exposure. RAW 264.7 cells exposed to PHY alone (>30 microg/ml) for 4 h displayed decreased cell viability (P < 0.05) and increased apoptosis (P < 0.05). Phytolens may have beneficial effects on inflammation by attenuating peroxynitrite-induced apoptosis. The sparing of epithelial cells while compromising the viability of macrophages suggests that PHY may be beneficial in autoimmune disorders.

Anti-inflammatory action of Pluchea sagittalis: involvement of an antioxidant mechanism

Pluchea sagittalis, (Lam.) Cabr., a popular medicinal herb grown in South America, was studied for anti-inflammatory and antioxidant activities. The anti-edema action of P. sagittalis aqueous extract was assayed in different models of inflammation: 1) the mouse ear edema test induced by arachidonic acid and croton oil; 2) the rat hind-paw edema test produced by several inflammatory inductors: carrageenan, dextran, zymosan, platelet-activating factor (PAF) and arachidonic acid; 3) a subacute model based on the rat carrageenan air-pouch granuloma test. Blood leukocyte free radical production was measured by flow cytometry with 2',7'-dichlorofluorescin diacetate (DCFH-DA) in vivo, in rats with induced air-pouch granuloma, and in a model in vitro. stimulating leukocytes with hydrogen peroxide. The aqueous extract of P. sagittalis showed a marked anti-inflammatory effect in both ear edema tests, dextran and carrageenan hind-paw edemas and carrageenan air-pouch model. It also had a potent antioxidant activity in blood leukocytes, both in vivo and in vitro. Our results correlate the reduction of free radical production with the anti-inflammatory effect of this plant.

Nonsteroidal antiinflammatory drugs interact with horseradish peroxidase in an in vitro assay system for hydrogen peroxide scavenging

The established horseradish peroxidase/guaiacol in an in vitro assay system was used for investigation of the reactivity of nonsteroidal antiinflammatory drugs with hydrogen peroxide. Although the drugs rapidly seemed to react in the selected conditions, difficulties were encountered in attempts to quantify the reaction and an interaction with horseradish peroxidase was suspected. A more specific assay system based on the absolute specificity of the enzyme glutathione peroxidase for glutathione was subsequently used which demonstrated that none of the investigated nonsteroidal antiinflammatory drugs was able to scavenge hydrogen peroxide. An original procedure to further evidence the interaction was developed thereafter, based on the reaction of 5-aminosalicylic acid with similar hemoproteins. This led to the demonstration that nonsteroidal antiinflammatory drugs were substrates for horseradish peroxidase and explained their reactivity in the horseradish peroxidase/guaiacol assay system. The compound 5-aminosalicylic acid showed an unusual behaviour that was attributed to its ability to both scavenge hydrogen peroxide and interact with horseradish peroxidase. It was concluded that the lack of specificity of horseradish peroxidase for its donor substrate may lead to erroneous results in assays for hydrogen peroxide scavenging of some drugs. An alternative method is however available and a simple spectroscopic assay can evidence the interaction with horseradish peroxidase.

The anti-oxidant properties of 5-aminosalicylic acid

Oxidative damage to biological membranes is an important cause of tissue injury in inflammatory bowel disease. 5-Aminosalicylic Acid (5ASA) has therapeutic efficacy in Ulcerative colitis, which may be based on its antioxidant properties. We used Parinaric acid as a fluorescent marker of oxidation in an intestinal microvillous brush border membrane preparation. Various concentrations of the antioxidants 5ASA, ascorbate, and tocopherol were added, and oxidation was initiated from within the membrane by 2,2' azobis (2.4-dimethylvaleronitrile) (AMVN) and from solution by 2,2' azobis (2-amidinopropane) hydrochloride (AAPH). Tocopherol was able to inhibit oxidation from either source. Ascorbate was only able to inhibit oxidation initiated from solution. 5ASA was able to inhibit oxidation initiated from either site, and was more effective than tocopherol against AAPH, but similarly effective against AMVN. We postulate that water soluble 5ASA preferentially associates with membrane surface, allowing chain-breaking antioxidant activity when peroxidation is initiated within the membrane. Likewise, it is effective against aqueous oxidants because its position allows it to interact with AAPH before lipid peroxidation can be initiated as well as breaking the lipid peroxidation chain once it is initiated. This dual capacity may be important for therapeutic effect of 5ASA and may suggest other candidate antioxidants for clinical trials.