Modulation of intracellular glutathione concentration alters dehydropyrimidine dehydrogenase activity in peripheral blood mononuclear cells

Comparison of three oral selenium compounds in cancer patients: Evaluation of differential pharmacodynamic effects in normal and malignant cells

BACKGROUND

Selenium (Se) compounds have demonstrated therapeutic synergism in combination with anticancer treatments whilst reducing normal tissue toxicities in a range of experimental models. While reduction in some toxicities of chemotherapy and radiation has been confirmed in randomised clinical trials, they have not been powered to evaluate improved anticancer efficacy. A lack of data on the clinical potencies of the main nutritionally-relevant forms of Se and the relationship between their pharmacokinetic (PK) profiles and pharmacodynamic (PD) effects in cancer patients has hampered progress to date. The primary objective of this study was to determine the dose and form of Se that can be most safely and effectively used in clinical trials in combination with anti-cancer therapies.

STUDY METHODS

In a phase I randomised double-blinded study, the PD profile of sodium selenite (SS), Se-methylselenocysteine (MSC) and seleno-l-methionine (SLM) were compared in two cohorts of 12 patients, one cohort with chronic lymphocytic leukaemia (CLL) and the other with solid malignancies. All 24 patients were randomised to receive 400 μg of elemental Se as either SS, MSC or SLM, taken orally daily for 8 weeks. PD parameters were assessed before, during and 4 weeks after Se compound exposure in plasma and peripheral blood mononuclear cells (PBMCs).

RESULTS

No significant sustained changes were observed in plasma concentrations of vascular endothelial growth factor-α (VEGF-α), expression of proteins associated with endoplasmic reticulum stress (the unfolded protein response) or in intracellular total glutathione in PBMCs, in either disease cohort or when grouped by Se compound.

CONCLUSIONS

At the 400 μg dose level no substantial changes in PD parameters were noted. Extrapolating from pre-clinical data, the dose examined in this cohort was too low to achieve the Se plasma concentration (≥ 5 μM) expected to elicit significant PD effects. Recruitment of a subsequent cohort at higher doses to exceed this PK threshold is planned.

Beyond branching: multiknot structured polymer for gene delivery

Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral vectors thanks to their safety and ease of production, but low transfection potency has limited their application. Many polycationic vectors show high efficiency in vitro, but their excessive charge density makes them toxic for in vivo applications. Herein, we demonstrate the synthesis of new and unique disulfide-reducible polymeric gene nanocarriers that exhibit significantly enhanced transfection potency and low cytotoxicity, particularly in skin cells, surpassing the efficiency of the well-known transfection reagents polyethylenimine (PEI) and Lipofectamine2000. The unique three-dimensional (3D) "multiknot" vectors were synthesized from in situ deactivation enhanced atom transfer radical (co)polymerization (DE-ATRP) of multivinyl monomers (MVMs). The high transfection levels and low toxicity of this multiknot structured polymer in vitro, combined with its ability to mediate collagen VII expression in 3D skin equivalents made from cells of recessive dystrophic epidermolysis bullosa patients, demonstrates its use as a platform nanotechnology which should be investigated further for dermatological disease therapies. Our findings suggest that the marked improvements stem from the dense multiknot architecture and degradable property, which facilitate both the binding and releasing process of the plasmid DNA.

Effect of green tea on pharmacokinetics of 5-fluorouracil in rats and pharmacodynamics in human cell lines in vitro

Tea drinking is widely practiced in the world and has recently increased among cancer patients. However, the effects of concurrent consumption of tea on the bioavailability and the net therapeutic potential of co-administered chemical drugs are not clear. In this study, the effects of green tea on the pharmacokinetics of 5-fluorouracil (5-FU) in rats and the pharmacodynamics in human cell lines in vitro were studied. The pharmacokinetic experiment indicated that there was an approximately 151% increase in the maximum plasma concentration (C(max)) and an approximately 425% increase in the area under the plasma concentration curve (AUC) of 5-FU in the green tea-treated group compared with the control group. Green tea consumption increased the plasma concentration of 5-FU. In addition, the pharmacodynamics experiment showed that at the moderate dose level (equivalent to <6 cups daily in human), neither fresh green tea extract nor (-)-epigallocatechin-3-gallate (EGCG) showed significant additive effects on the cytotoxicity of 5-FU in human cell lines. The results showed that it is crucial to perform therapeutic drug monitoring (TDM) when the cancer patients have a habit of drinking green tea.

An intracellular antioxidant determines the expression of a melanin-based signal in a bird

To understand how traits used in animal communication evolved and are maintained as honest signals, we need to understand the mechanisms that prevent cheating. It has been proposed that honest signaling is guaranteed by the costs associated with the signal expression. However, the nature of these costs is still under debate. Melanin-based signals are intriguing because their expression seems to be tightly controlled by genes and the resource involved (i.e. melanin) seems to be not limited. However, in vertebrates, low levels of a key intracellular antioxidant (i.e. glutathione) are needed to promote melanogenesis. We propose that melanin-based ornaments can signal the ability to cope with oxidative stress because those individuals with low enough levels of glutathione, such as those required for melanin production, should manage well the whole of the antioxidant machinery in order to maintain a certain oxidative status. We analysed the expression of a melanin-based signal: the well-known black stripe of the great tit (Parus major). Great tit nestlings were injected with a specific inhibitor of glutathione production (DL-buthionine-S,R-sulfoximine; BSO) throughout their development. BSO effectively decreased intracellular glutathione levels without apparent side effects on growth or body condition. Instead, treated nestlings developed black breast stripes 70-100% larger than controls. Moreover, treated nestlings also compensated the decrease in glutathione levels by increasing the levels of circulating antioxidants. Results indicate that melanin-based signals can be at least partially permeable to environmental influences such as those associated to oxidative stress. They also reveal a potential handicap associated to the expression of this kind of signals. Finally, although other contributing factors could have been present, our findings emphasize the role of oxidative stress in shaping the evolution of animal signals in general and, in particular, those produced by pigments.