Study of the effect of dose-rate on radiation-induced damage to human erythrocytes

Effects of Very Low Dose Fast Neutrons on Cell Membrane And Secondary Protein Structure in Rat Erythrocytes

The effects of ionizing radiation on biological cells have been reported in several literatures. Most of them were mainly concerned with doses greater than 0.01 Gy and were also concerned with gamma rays. On the other hand, the studies on very low dose fast neutrons (VLDFN) are rare. In this study, we have investigated the effects of VLDFN on cell membrane and protein secondary structure of rat erythrocytes. Twelve female Wistar rats were irradiated with neutrons of total dose 0.009 Gy (²⁴¹Am-Be, 0.2 mGy/h) and twelve others were used as control. Blood samples were taken at the 0, 4th, 8th, and 12th days postirradiation. Fourier transform infrared (FTIR) spectra of rat erythrocytes were recorded. Second derivative and curve fitting were used to analysis FTIR spectra. Hierarchical cluster analysis (HCA) was used to classify group spectra. The second derivative and curve fitting of FTIR spectra revealed that the most significant alterations in the cell membrane and protein secondary structure upon neutron irradiation were detected after 4 days postirradiation. The increase in membrane polarity, phospholipids chain length, packing, and unsaturation were noticed from the corresponding measured FTIR area ratios. This may be due to the membrane lipid peroxidation. The observed band shift in the CH₂ stretching bands toward the lower frequencies may be associated with the decrease in membrane fluidity. The curve fitting of the amide I revealed an increase in the percentage area of α-helix opposing a decrease in the β-structure protein secondary structure, which may be attributed to protein denaturation. The results provide detailed insights into the VLDFN effects on erythrocytes. VLDFN can cause an oxidative stress to the irradiated erythrocytes, which appears clearly after 4 days postirradiation.

Fullerenols as a new therapeutic approach in nanomedicine

Recently, much attention has been paid to the bioactive properties of water-soluble fullerene derivatives: fullerenols, with emphasis on their pro- and antioxidative properties. Due to their hydrophilic properties and the ability to scavenge free radicals, fullerenols may, in the future, provide a serious alternative to the currently used pharmacological methods in chemotherapy, treatment of neurodegenerative diseases, and radiobiology. Some of the most widely used drugs in chemotherapy are anthracycline antibiotics. Anthracycline therapy, in spite of its effective antitumor activity, induces systemic oxidative stress, which interferes with the effectiveness of the treatment and results in serious side effects. Fullerenols may counteract the harmful effects of anthracyclines by scavenging free radicals and thereby improve the effects of chemotherapy. Additionally, due to the hollow spherical shape, fullerenols may be used as drug carriers. Moreover, because of the existence of the currently ineffective ways for neurodegenerative diseases treatment, alternative compounds, which could prevent the negative effects of oxidative stress in the brain, are still sought. In the search of alternative methods of treatment and diagnosis, today's science is increasingly reaching for tools in the field of nanomedicine, for example, fullerenes and their water-soluble derivatives, which is addressed in the present paper.

Can melatonin delay oxidative damage of human erythrocytes during prolonged incubation?

PURPOSE

Melatonin (MEL) is an effective antioxidant in numerous experimental models, both in vitro and in vivo. However, it should be stressed that there are also papers reporting limited antioxidative activity of MEL or even giving evidence for its pro-oxidative properties. In the present paper we investigated the influence of MEL on the oxidative damage of human erythrocytes during prolonged incubation.

MATERIAL/METHODS

Human erythrocytes suspended in phosphate-buffered saline (PBS), pH 7.4 were incubated at 37ºC either in absence or presence of melatonin at concentration range 0.02 mM-3 mM for up to 96 hrs. The influence of MEL on erythrocyte damage was assessed on the basis of the intensity of intracellular oxidation processes (the oxidation of HbO₂, GSH, fluorescent label DCFH₂) as well as damage to the plasma membrane (lipid peroxidation, the potassium leakage) and the kinetics of hemolysis.

RESULTS

The prolonged incubation of erythrocytes induced a progressive destruction of erythrocytes. Melatonin prevented lipid peroxidation and hemolysis whereas the oxidation of HbO₂ and DCFH₂ was enhanced by melatonin at concentrations higher than 0.6 mM. In the case of erythrocytes incubated with 3 mM of MEL, the hemolysis rate constant (0.0498±0.0039 H%•h⁻¹) was 50% lower than that of the control while the HbO₂ oxidation rate constants were about 1.4 and 1.5 times higher for 1.5 and 3 mM of MEL, respectively. Melatonin had no influence on the oxidation of GSH and the potassium leakage.

CONCLUSIONS

Probably, MEL can stabilize the erythrocyte membrane due to interaction with lipids, thus prolonging the existence of cells. On the contrary, in the presence of MEL the accelerated oxidation of HbO₂ and generally, increased oxidative stress was observed in erythrocytes. Pro- and antioxidative properties of melatonin depend on the type of cells, redox state, as well as experimental conditions.