The effect of iron loading and iron chelation on the innate immune response and subclinical organ injury during human endotoxemia: a randomized trial.

In this double-blind randomized placebo-controlled trial involving 30 healthy male volunteers we investigated the acute effects of iron loading (single dose of 1.25 mg/kg iron sucrose) and iron chelation therapy (single dose of 30 mg/kg deferasirox) on iron parameters, oxidative stress, the innate immune response, and subclinical organ injury during experimental human endotoxemia. The administration of iron sucrose induced a profound increase in plasma malondialdehyde 1 h after administration (433±37% of baseline; P<0.0001), but did not potentiate the endotoxemia-induced increase in malondialdehyde, as was seen 3 h after endotoxin administration in the placebo group (P=0.34) and the iron chelation group (P=0.008). Endotoxemia resulted in an initial increase in serum iron levels and transferrin saturation that was accompanied by an increase in labile plasma iron, especially when transferrin saturation reached levels above 90%. Thereafter, serum iron decreased to 51.6±9.7% of baseline at T=8 h in the placebo group versus 84±15% and 60.4±8.9% of baseline at 24 h in the groups treated with iron sucrose and deferasirox, respectively. No significant differences in the endotoxemia-induced cytokine response (TNF-α, IL-6, IL-10 and IL-1RA), subclinical vascular injury and kidney injury were observed between groups. However, vascular reactivity to noradrenalin was impaired in the 6 subjects in whom labile plasma iron was elevated during endotoxemia as opposed to those in whom no labile plasma iron was detected (P=0.029). In conclusion, a single dose of iron sucrose does not affect the innate immune response in a model of experimental human endotoxemia, but may impair vascular reactivity when labile plasma iron is formed. (Clinicaltrials.gov identifier:01349699).

Proteomic inventory of "anchorless" proteins on the colon adenocarcinoma cell surface.

Surface proteins play important pathophysiological roles in health and disease, and accumulating proteomics-based studies suggest that several "non-membrane" proteins are sorted to the cell surface by unconventional mechanisms. Importantly, these proteins may comprise attractive therapeutic targets and novel disease markers for colon cancer. To perform a proteomics-based inventory of these so-called "anchorless" surface proteins, intact colon adenocarcinoma SW480 cells were labeled with membrane-impermeable biotin after which only soluble biotinylated proteins were isolated and identified by nanoLC-MS/MS. Computer-assisted analysis predicted that only 9 of the 97 identified surface-exposed proteins have predicted secretory signal peptides, whereas 2 other proteins have a putative transmembrane segment. Of the 9 proteins with putative signal peptides, 1 was predicted to be retained at the cell surface by a GPI-anchor, whereas 5 other proteins contained an ER-retention motif (KDEL) that should prevent them from being sorted to the cell surface. The remaining 86 soluble "surface" proteins lack known export signals and the possibility that these proteins are candidate substrates of non-classical transporters or exported by unconventional mechanisms is discussed. Alternatively, the large number of "intracellular" and ER-resident proteins may imply that biotinylation approaches are not only specific for surface proteins, but also biased against a certain subset of non-surface proteins. This underscores the importance of post-proteomic verification of proteomics-based inventories on surface-exposed proteins, which eventually should reveal to which extent non-classical export and retention mechanisms contribute to the sorting of "anchorless" proteins to the surface of colon tumor cells.

Effects of dietary anticarcinogens and nonsteroidal anti-inflammatory drugs on rat gastrointestinal UDP-glucuronosyltransferases.

BACKGROUND: Dietary compounds or nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce cancer rates. Elevation of phase II detoxification enzymes might be one of the mechanisms leading to cancer prevention. We investigated the effects of dietary anticarcinogens and NSAIDs on rat gastrointestinal UDP-glucuronosyltransferases (UGT). MATERIALS AND METHODS: Diets of Wistar rats were supplemented with oltipraz, alpha-tocopherol, beta-carotene, phenethylisothiocyanate (PEITC), sulforaphane analogue compound-30, indole-3-carbinol, D-limonene, relafen, indomethacin, ibuprofen, piroxicam, acetyl salicylic acid or sulindac. Hepatic and intestinal UGT enzyme activities were quantified by using 4-nitrophenol and 4-methylumbelliferone as substrates. RESULTS: Compound-30, D-limonene, indomethacin, ibuprofen or sulindac enhanced proximal small intestinal UGT activities. Only compound-30 was able to induce mid- and distal small intestinal UGT activities. Large intestinal UGT activities were increased by ibuprofen and sulindac, whereas oltipraz, PEITC and D-limonene gave enhanced hepatic UGT activities. CONCLUSION: Mainly rat proximal small intestinal and hepatic UGT enzyme activities were induced by dietary anticarcinogens or NSAIDs. Enhanced UGT activities might lead to a more efficient detoxification of carcinogenic compounds and thus could contribute to the prevention of gastrointestinal cancer.

N-Acetylcysteine improves the disturbed thiol redox balance after methionine loading.

Methionine loading seems to be accompanied by increased oxidative stress and damage. However, it is not known how this oxidative stress is generated. We performed the present crossover study to further elucidate the effects of methionine loading on oxidative stress in the blood of healthy volunteers, and to examine possible preventative effects of N -acetylcysteine (NAC) administration. A total of 18 healthy subjects were given two oral methionine loads of 100 mg/kg body weight, 4 weeks apart, one without NAC (Met group), and one in combination with supplementation with 2x900 mg doses of NAC (Met+NAC group). Blood samples were collected before and 2, 4, 8 and 24 h after methionine loading for measurements of thiol levels, protein carbonyls, lipid peroxidation, cellular fibronectin and ferric reducing ability of plasma (FRAP; i.e. antioxidant capacity). After methionine loading, whole-blood levels of free and oxidized cysteine and homocysteine were increased in both groups. Furthermore, the total plasma levels of homocysteine were higher, whereas those of cysteine were lower, after methionine loading in both groups. Lower levels of oxidized homocysteine and a higher free/oxidized ratio were found in the Met+NAC group compared with the Met group. Although the antioxidant capacity decreased after methionine loading, no major changes over time were found for protein carbonyls or cellular fibronectin in either group. Our results suggest that methionine loading may initiate the generation of reactive oxygen species by the (auto)-oxidation of homocysteine. In addition, supplementation with NAC seems to be able to partially prevent excessive increases in the levels of homocysteine in plasma and of oxidized homocysteine in whole blood, and might thereby contribute to the prevention of oxidative stress.

Effects of oral N-acetylcysteine on plasma homocysteine and whole blood glutathione levels in healthy, non-pregnant women.

Oral N-acetylcysteine supplementation in nine young healthy females induced a quick and highly significant decrease in plasma homocysteine levels and an increase in whole blood concentration of the antioxidant glutathione. N-acetylcysteine impresses as an efficient drug in lowering homocysteine concentration and might be beneficial for individuals with hyperhomocysteinemia who are at increased risk of cardiovascular disease.