In antioxidant competition assays, an antioxidant (A) and a detector compound (D) compete for a reactive species (R). In the evaluation of these assays, it is tacitly assumed that all of R is captured by either D or A. Due to the - by definition - high reactivity of R, unspecific reactions of R are likely to occur and neglecting these reactions will result in a systematic underestimation of antioxidant activity. It was shown that in the standard hydroxyl radical scavenging assay this was indeed the case; the inaccurate mathematical evaluation resulted in an underestimation of antioxidant activity of 25% in this competition assay. The systematic underestimation of antioxidant activity can be prevented by using an adjusted Stern-Volmer equation that takes into account that only part of R is captured by D or A.

The nuclear enzyme poly(ADP-ribose) polymerse-1 (PARP-1) has previously been reported to play an important role in lipopolysaccharide (LPS)-induced pulmonary inflammation and is highly activated in COPD patients. In the present study, the anti-inflammatory efficacy of a previously identified poly(ADP-ribose) polymerase-1 (PARP-1) inhibiting caffeine metabolite, 1,7-dimethylxanthine, was both in vivo as well as ex vivo evaluated. Orally administered 1,7-dimethylxanthine significantly attenuated lung myeloperoxidase-levels, transcription of IL-6, TNF-alpha, MIP1alpha and MIP2 genes as well as PAR-polymer formation in a mouse model of intratracheally LPS-induced acute pulmonary inflammation. Serum amyloid P component and plasma IL-6 were also lowered in 1,7-dimethylxanthine treated mice, indicating a reduced systemic inflammatory response. In addition, at 24h after LPS administration anti-inflammatory effects of 1,7-dimethylxanthine appeared more pronounced than those of the orally administered PARP-1 inhibitor 3-aminobenzamide. In the second model, in blood of COPD-patients and healthy controls ex vivo pre-incubated with a physiological concentration of 1,7-dimethylxanthine (10microM), LPS-induced production of the cytokines IL-6 and TNF-alpha was significantly suppressed. 1,7-Dimethylxanthine exerts anti-inflammatory effects, both in vivo mouse as well as ex vivo human. These results suggest that the PARP-1 inhibiting caffeine metabolite 1,7-dimethylxanthine may have therapeutic potential in pulmonary inflammatory diseases such as COPD.

Peroxiredoxin I (Prx I) belongs to a family of proteins with thiol-dependent peroxidase activity and is involved in the cellular protection against oxidative stress, the modulation of intracellular signalling cascades as well as the regulation of cell proliferation and apoptosis. In RAW 264.7 mouse macrophage cells Prx I was up-regulated on the mRNA and protein level by lipopolysaccharide (LPS). Treatment of cells with LPS increased the phosphorylation of c-Jun-NH(2)-terminal kinase (JNK) and protein kinase B (PKB). Both SP600125, an inhibitor of JNK, and LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), dose-dependently decreased LPS-induced Prx I mRNA expression. Furthermore, up-regulation of Prx I mRNA by LPS was diminished by the Src tyrosine kinase inhibitor PP2 and the iNOS inhibitor L-NMMA. LPS-dependent induction of Prx I is likely mediated by an activator protein-1 site within the Prx I promoter region binding JunB and c-Fos. In contrast, NFkappaB was not involved in the activation of Prx I transcription. Our results suggest that the up-regulation of Prx I gene expression by LPS is part of the cellular response to stress and may protect against oxidative stress-related injury in RAW 264.7 cells.

Medical students in the Netherlands have the opportunity to follow an internship abroad. However, this is often at the expense of developing their competence, for example in situations where they do not learn abroad what they would have learnt had they followed the Dutch programme. An international internship should, therefore, not be obliged for all medical students.

BACKGROUND: The aim of this study was to disentangle the contribution of muscular vs pulmonary oxidative stress during endurance exercise in patients with COPD. METHODS: Fifteen COPD patients and 10 healthy age-matched controls performed a continuously submaximal single leg ergometer test (40% of peak workload) for 20 min or until they stopped (Tlim). Venous blood, urine samples and exhaled breath condensate were sampled before, immediately and 2h after exercise. RESULTS: Tlim was lower in COPD than controls (p < 0.01). No exercise-induced systemic inflammation (IL-6, TNF-alpha) was found in the groups. Urinary malondialdehyde (MDA) and uric acid (p < 0.05) were increased in COPD whereas erythrocyte GSSG/GSH tended to be increased in COPD compared to controls after exercise (p = 0.08). Despite the relatively low cardioventilatory response to this localized muscle exercise, hydrogen peroxide (H(2)O(2)) in breath condensate significantly increased in COPD (p < 0.01). NF-kappaB DNA binding activity of p50 in peripheral blood monocytes was elevated after exercise in both COPD (p < 0.01) and controls (p < 0.05), whereas p65 protein was not altered. CONCLUSION: COPD patients showed increased pulmonary and systemic oxidative stress after localized leg muscle exercise compared to healthy controls without evidence of increased levels of systemic inflammation.

Ferulic acid (FA) is the most abundant phenolic compound in wheat grain, mainly located in the bran. However, its bioaccessibility from the bran matrix is extremely low. Different bioprocessing techniques involving fermentation or enzymatic and fermentation treatments of wheat bran were developed aiming at improving the bioaccessibility of phenolic compounds in bran-containing breads. The bioaccessibility of ferulic acid, p-coumaric acid, and sinapic acid was assessed with an in vitro model of upper gastrointestinal tract (TIM-1). Colonic metabolism of the phenolic compounds in the nonbioaccessible fraction of the breads was studied with an in vitro model of human colon (TIM-2). The most effective treatment was the combination of enzymes and fermentation that increased the bioaccessibility of FA from 1.1% to 5.5%. The major colonic metabolites were 3-(3-hydroxyphenyl)propionic acid and 3-phenylpropionic acid. Bran bioprocessing increases the bioaccessibility of phenolic compounds as well as the colonic end metabolite 3-phenylpropionic acid.

Activation of the NADPH oxidase homolog dual oxidase 1 (DUOX1) within the airway epithelium cells represents a key mechanism of innate airway host defense, through enhanced production of H2O2 mediating cellular signaling pathways that regulate the production of various inflammatory mediators. Production of the CXC chemokine interleukin (IL)-8/CXCL8 forms a common epithelial response to many diverse stimuli, including bacterial and viral triggers, environmental oxidants, and other biological mediators, suggesting the potential involvement of a common signaling pathway that may involve DUOX1-dependent H2O2 production. Following previous reports showing that DUOX1 is activated by extracellular ATP and purinergic receptor stimulation, the present studies demonstrate that airway epithelial IL-8 production in response to several bacterial stimuli involves ATP release and DUOX1 activation. ATP-mediated DUOX1 activation resulted in the activation of ERK1/2 and NF-B pathways, which was associated with epidermal growth factor (EGFR) ligand shedding by ADAM17 (a disintegrin and metalloproteinase-17). Although ATP-mediated ADAM17 activation and IL-8 release were not prevented by extracellular H2O2 scavenging by catalase, these responses were attenuated by intracellular scavengers of H2O2 or related oxidants, suggesting an intracellular redox signaling mechanism. Both ADAM17 activation and IL-8 release were suppressed by inhibitors of EGFR/ERK1/2 signaling, which can regulate ADAM17 activity by serine/threonine phosphorylation. Collectively, our results indicate that ATP-mediated DUOX1 activation represents a common response mechanism to several environmental stimuli, involving H2O2-dependent EGFR/ERK activation, ADAM17 activation and EGFR ligand shedding, leading to amplified epithelial EGFR activation and IL-8 production.

Some patients with sarcoidosis can have cardiac involvement. Impairment of the cardiac sympathetic nerve activity is seen in about 50% of the sarcoidosis patients with small fiber neuropathy. In this case we present a sarcoidosis patient with small fiber neuropathy and cardiac symptoms with a cardiac sympathetic dysfunction, assessed with I-123 MIBG SPECT. After 5 months of treatment with carvedilol, which has besides adrenergic receptor blocking effects also antioxidant action, we saw a clear improvement of the cardiac sympathetic function demonstrated on a repeated I-123 MIBG SPECT. Future studies should explore the clinical relevance of the relation of oxidative stress, antioxidant therapy and cardiac dysfunction in sarcoidosis.

The activity of antioxidants is frequently determined in competition assays. In these assays an antioxidant (A) and detector molecule (D) compete for the reactive species (R). The competitive inhibitory effect of A on the reaction of D with R is a measure of the antioxidant activity of A. In determining the activity of A, it is in general incorrectly assumed that the concentrations of A and D remain equal to the initial concentration. However, the principle of the assay is that some A and D is consumed assay and consequently the concentration of A and D will decrease during a competition assay, resulting in a deviation in the observed antioxidant activity. Computer modeling was used to obtain a graphical tool to estimate the extent of the deviation caused by the incorrect assumption that the concentrations of A and D do not decrease. Several competition assays are evaluated using this graphical tool, demonstrating that frequently inaccurate antioxidant activities have been reported. In general, differences between antioxidants are underestimated and the activity of all antioxidants shifts towards the antioxidant activity of D. A strategy is provided to improve the accuracy of a competition assay. To obtain accurate results in a competition assay, the reaction rate constant of the detector molecule with the reactive species should be comparable to that of the antioxidant. In addition, the concentration of reactive species should be as low as possible.