Structure engineering of filled protein microbeads to tailor release of oil droplets in gastric digestion.

Oil-soluble components can be encapsulated in an O/W1/W2 microsystem, in which they are dissolved in oil droplets dispersed in a gelled microbead (W1), which forms a barrier between the oil droplets and the aqueous continuous phase (W2). We investigated the rate and mechanism of breakdown of protein microbeads in a simulated gastric system, and studied the influence of microbead protein concentration, gelling method (cold-set, slow and fast heat-set), and further processing (freeze-drying), on the breakdown process. Breakdown rate decreased with increasing protein content of the beads, for the same method of production. Due to the porosity of the slowly-heated heat-set beads, breakdown occurred evenly throughout the entire bead. Cold-set microbeads of 10% protein broke down slightly slower than the heat-set microbeads of 15%. The denser surface of the 10% beads slowed down the diffusion of the enzymes into the bead's interior, causing the beads to be broken down from the outside inward. All these beads broke down within one hour. Increasing the rate of temperature increase during the heating step dramatically slowed breakdown. There was no significant breakdown of rapidly heated beads within 138 minutes, even though no difference in microstructure between rapidly and slowly heated beads was visible with electron microscopy. Freeze-drying of the beads also slowed their breakdown. After 132 minutes more than half the measured particle volume of were intact beads. Freeze-drying changed the microstructure of the beads irreversibly: rehydrating the dried beads did not result in a breakdown behaviour similar to that of unprocessed beads.

Targeting of mitochondrial reactive oxygen species production does not avert lipid-induced insulin resistance in muscle tissue from mice.

AIMS/HYPOTHESIS: High-fat, high-sucrose diet (HF)-induced reactive oxygen species (ROS) levels are implicated in skeletal muscle insulin resistance and mitochondrial dysfunction. Here we investigated whether mitochondrial ROS sequestering can circumvent HF-induced oxidative stress; we also determined the impact of any reduced oxidative stress on muscle insulin sensitivity and mitochondrial function. METHODS: The Skulachev ion (plastoquinonyl decyltriphenylphosphonium) (SkQ), a mitochondria-specific antioxidant, was used to target ROS production in C2C12 muscle cells as well as in HF-fed (16 weeks old) male C57Bl/6 mice, compared with mice on low-fat chow diet (LF) or HF alone. Oxidative stress was measured as protein carbonylation levels. Glucose tolerance tests, glucose uptake assays and insulin-stimulated signalling were determined to assess muscle insulin sensitivity. Mitochondrial function was determined by high-resolution respirometry. RESULTS: SkQ treatment reduced oxidative stress in muscle cells (-23% p < 0.05), but did not improve insulin sensitivity and glucose uptake under insulin-resistant conditions. In HF mice, oxidative stress was elevated (56% vs LF p < 0.05), an effect completely blunted by SkQ. However, HF and HF+SkQ mice displayed impaired glucose tolerance (AUC HF up 33%, p < 0.001; HF+SkQ up 22%; p < 0.01 vs LF) and disrupted skeletal muscle insulin signalling. ROS sequestering did not improve mitochondrial function. CONCLUSIONS/INTERPRETATION: SkQ treatment reduced muscle mitochondrial ROS production and prevented HF-induced oxidative stress. Nonetheless, whole-body glucose tolerance, insulin-stimulated glucose uptake, muscle insulin signalling and mitochondrial function were not improved. These results suggest that HF-induced oxidative stress is not a prerequisite for the development of muscle insulin resistance.

Protectors against doxorubicin-induced cardiotoxicity: flavonoids.

Doxorubicin is a widely used anthracycline anticancer agent. Its use may cause cardiomyopathy: in fact, the development of cumulative dose-related cardiotoxicity forms the major limitation of clinical doxorubicin use. We therefore searched for protective agents that combine iron-chelating and oxygen radical-scavenging properties. Moreover, any novel protector should not interfere with the cytostatic activity of doxorubicin. After extensive in vitro screening we found that flavonoids could serve this purpose. In particular 7-monohydroxyethylrutoside almost completely protected against the negative inotropic action of doxorubicin in the electrically paced mouse left atrium model. In vivo it gave full protection at 500 mg/kg intraperitoneally against the doxorubicin-induced ST-interval lengthening in the ECG. Moreover, this protector did not influence the antitumor effect of doxorubicin either in vitro using the human ovarian cell lines A2780 and OVCAR-3 and the human breast cancer cell line MCF-7 or in vivo in A2780 and OVCAR-3 subcutaneous xenografts in nude mice. Comparison of various iron chelators suggest that iron, in contrast to the general assumption, might not play a crucial role in the oxidative stress-induced toxicity of doxorubicin. Moreover, incubation of vascular endothelial cells with doxorubicin produced overexpression of adhesion molecules, which could be inhibited by 7-monohydroxyethylrutoside. From a study in human volunteers, we conclude that an intravenous dose of 1500 mg/m(2) of 7-monohydroxyethylrutoside is feasible and is safe to be investigated as protection against doxorubicin-induced cardiotoxicity.

Iron is not involved in oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin.

BACKGROUND AND PURPOSE: The anticancer drugs doxorubicin and bleomycin are well-known for their oxidative stress-mediated side effects in heart and lung, respectively. It is frequently suggested that iron is involved in doxorubicin and bleomycin toxicity. We set out to elucidate whether iron chelation prevents the oxidative stress-mediated toxicity of doxorubicin and bleomycin and whether it affects their antiproliferative/proapoptotic effects. EXPERIMENTAL APPROACH: Cell culture experiments were performed in A549 cells. Formation of hydroxyl radicals was measured in vitro by electron paramagnetic resonance (EPR). We investigated interactions between five iron chelators and the oxidative stress-inducing agents (doxorubicin, bleomycin and H(2)O(2)) by quantifying oxidative stress and cellular damage as TBARS formation, glutathione (GSH) consumption and lactic dehydrogenase (LDH) leakage. The antitumour/proapoptotic effects of doxorubicin and bleomycin were assessed by cell proliferation and caspase-3 activity assay. KEY RESULTS: All the tested chelators, except for monohydroxyethylrutoside (monoHER), prevented hydroxyl radical formation induced by H(2)O(2)/Fe(2+) in EPR studies. However, only salicylaldehyde isonicotinoyl hydrazone and deferoxamine protected intact A549 cells against H(2)O(2)/Fe(2+). Conversely, the chelators that decreased doxorubicin and bleomycin-induced oxidative stress and cellular damage (dexrazoxane, monoHER) were not able to protect against H(2)O(2)/Fe(2+). CONCLUSIONS AND IMPLICATIONS: We have shown that the ability to chelate iron as such is not the sole determinant of a compound protecting against doxorubicin or bleomycin-induced cytotoxicity. Our data challenge the putative role of iron and hydroxyl radicals in the oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin and have implications for the development of new compounds to protects against this toxicity.

Lack of inhibition of endothelial nitric oxide synthase in the isolated rat aorta by doxorubicin.

Besides inducing cardiotoxicity, doxorubicin also affects the vasculature. Recent observations in cultured endothelial cells indicated that the endothelial form of nitric oxide synthase might be inhibited by doxorubicin thereby seriously interfering with vascular function. We have investigated the effect of doxorubicin on the relaxation induced by the muscarinic agonist carbachol in the isolated rat aorta. It was found that doxorubicin at concentrations up to 50 microM does not alter the relaxant response to carbachol. Direct measurement of nitrite, the metabolite of NO*, by the Griess assay confirmed our observation that NO*)production is not inhibited by doxorubicin.