Excitatory amino acid-induced slow biphasic responses of free intracellular calcium in human neuroblastoma cells

AbstractEffects of an excitatory amino acid, glutamate, and of ionotropic and metabotropic glutamate receptor agonists on the levels of free intracellular calcium, and their specific receptor binding in human SH-SY5Y neuroblastoma cells were studied. The calcium response was always biphasic, except for AMPA, suggesting both stimulatory and inhibitory effects on free intracellular calcium upon glutamate receptor stimulation, both with ionotropic and metabotropic glutamate receptor agonists. Specific binding of glutamate and other glutamate receptor agonists, together with the biphasic calcium response, suggests that human SH-SY5Y neuroblastoma cells express both ionotropic and metabotropic glutamate receptors. These findings shed new light on the use of human SH-SY5Y neuroblastoma cells as a human neuronal tumor cell model

Genotoxicity of 50 Hz magnetic field in human SH-SY5Y neuroblastoma cells

ABSTRACT There have been discussions on the genotoxicity of extremely low frequency (ELF) magnetic field (MF) over the past two decades concerning appliances emitting electromagnetic field. The current study was designed to establish whether ELF MFs might cause genotoxic effect on human SH-SY5Y neuroblastoma cells. Numerous studies have suggested that there is a risk of cancer associated with exposure to ELF MFs. The results of the studies have been, however, inconsistent on mutagenicity and carcinogenicity of ELF MFs. In this study human SH-SY5Y neuroblastoma cells were exposed to 50 Hz MF (100 µT) for 24 h, after which they were co-exposed with menadione at different concentrations for the last 1 h. After the exposure, the samples were analyzed by alkaline comet assay to evaluate immediate DNA damage and repair, and micronucleus frequency was used to assess the persistent DNA damage. Mere menadione exposure and co-exposure to MF + menadione caused increased immediate DNA damage. Pre-exposure to MF decreased DNA repair rate as compared with menadione exposure alone. Pre-exposure to MF seems to decrease menadione-induced micronucleus frequency. In conclusion, pre-exposure to MF seems to affect menadioneinduced DNA damage responses

Transfer of elements into boreal forest ants at a former uranium mining site

Ants can influence ecological processes, such as the transfer of elements or radionuclides, in several ways. For example, they redistribute materials while foraging and maintaining their nests and have an important role in terrestrial food webs. Quantitative data of the transfer of elements into ants is needed, e.g., for developing improved radioecological models. In this study, samples of red wood ants (genus Formica), nest material, litter and soil were collected from a former uranium mining site in Eastern Finland. Concentrations of 33 elements were analyzed by Inductively Coupled Plasma-Mass Spectroscopy/Optical Emission Spectroscopy. Estimated element concentrations in spruce needles were used as a proxy for studying the transfer of elements into ants via aphids because spruces host the most important aphid farms in boreal forests. Empirically determined organism/medium concentration ratios (CRs) are commonly used in radioecological models. Ant/soil CRs were calculated and the validity of the fundamental assumption behind the of use of CRs (linear transfer) was evaluated. Elements that accumulated in ants in comparison to other compartments were cadmium, potassium, phosphorus, sulfur, and zinc. Ant uranium concentrations were low in comparison to soil, litter, or nest material but slightly elevated in comparison to spruce needles. Ant element concentrations were quite constant regardless of the soil concentrations. Non-linear transfer models could therefore describe the soil-to-ant transfer better than conventional CRs.</p

Transfer of elements relevant to radioactive waste into chironomids and fish in boreal freshwater bodies

Information on transfer of elements and their radionuclides is essential for radioecological modeling. In the present study, we investigated the transfer of Cl, Co, Mo, Ni, Se, Sr, U and Zn in a boreal freshwater food chain. These elements were selected on the basis that they have important radionuclides that might be released into the biosphere from various stages of the nuclear fuel cycle. Water, sediment, chironomid larvae (Chironomus sp.), roach (Rutilus rutilus) and perch (Perca fluviatilis) were sampled from two ponds near a former uranium mine and one reference pond located further away from the mining area. Concentrations measured in water, sediment and the three animal species indicated the importance of sediment as a source of uptake for most of the elements (but not Cl). This should be considered in radioecological models, which conventionally predict concentration in aquatic organisms from concentration in water. The results also show that the assumption of linear transfer (constant concentration ratio) may not be valid for elements into fish. The results of this study show that further basic research is needed to understand the fundamental processes involved in transfer of elements into freshwater organisms in order to develop radioecological models.</div

Pre-Exposure to 50 Hz Magnetic Fields Modifies Menadione-Induced Genotoxic Effects in Human SH-SY5Y Neuroblastoma Cells

BACKGROUND: Extremely low frequency (ELF) magnetic fields (MF) are generated by power lines and various electric appliances. They have been classified as possibly carcinogenic by the International Agency for Research on Cancer, but a mechanistic explanation for carcinogenic effects is lacking. A previous study in our laboratory showed that pre-exposure to ELF MF altered cancer-relevant cellular responses (cell cycle arrest, apoptosis) to menadione-induced DNA damage, but it did not include endpoints measuring actual genetic damage. In the present study, we examined whether pre-exposure to ELF MF affects chemically induced DNA damage level, DNA repair rate, or micronucleus frequency in human SH-SY5Y neuroblastoma cells. METHODOLOGY/PRINCIPAL FINDINGS: Exposure to 50 Hz MF was conducted at 100 µT for 24 hours, followed by chemical exposure for 3 hours. The chemicals used for inducing DNA damage and subsequent micronucleus formation were menadione and methyl methanesulphonate (MMS). Pre-treatment with MF enhanced menadione-induced DNA damage, DNA repair rate, and micronucleus formation in human SH-SY5Y neuroblastoma cells. Although the results with MMS indicated similar effects, the differences were not statistically significant. No effects were observed after MF exposure alone. CONCLUSIONS: The results confirm our previous findings showing that pre-exposure to MFs as low as 100 µT alters cellular responses to menadione, and show that increased genotoxicity results from such interaction. The present findings also indicate that complementary data at several chronological points may be critical for understanding the MF effects on DNA damage, repair, and post-repair integrity of the genome

Dioxin Induces Genomic Instability in Mouse Embryonic Fibroblasts

Ionizing radiation and certain other exposures have been shown to induce genomic instability (GI), i.e., delayed genetic damage observed many cell generations later in the progeny of the exposed cells. The aim of this study was to investigate induction of GI by a nongenotoxic carcinogen, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Mouse embryonic fibroblasts (C3H10T1/2) were exposed to 1, 10 or 100 nM TCDD for 2 days. Micronuclei (MN) and expression of selected cancer-related genes were assayed both immediately and at a delayed point in time (8 days). For comparison, similar experiments were done with cadmium, a known genotoxic agent. TCDD treatment induced an elevated frequency of MN at 8 days, but not directly after the exposure. TCDD-induced alterations in gene expression were also mostly delayed, with more changes observed at 8 days than at 2 days. Exposure to cadmium produced an opposite pattern of responses, with pronounced effects immediately after exposure but no increase in MN and few gene expression changes at 8 days. Although all responses to TCDD alone were delayed, menadione-induced DNA damage (measured by the Comet assay), was found to be increased directly after a 2-day TCDD exposure, indicating that the stability of the genome was compromised already at this time point. The results suggested a flat dose-response relationship consistent with dose-response data reported for radiation-induced GI. These findings indicate that TCDD, although not directly genotoxic, induces GI, which is associated with impaired DNA damage response

Studies on the mechanisms of lead neurotoxicity and oxidative stress in human neuroblastoma cells

Excitotoxicity and oxidative stress are two phenomena that have repeatedly been described as being involved in a wide range of disorders of the nervous system including epilepsy, ransient cerebral ischemia, Alzheimer's disease, Parkinson's disease and Huntington's disease. Glutamate, aspartate, and acetylcholine are the major excitatory neurotransmitters in the brain. The coexistence and co-release of neurotransmitters and their association in neuronal events, and coupling mechanisms have recently evoked considerable interest in the way these are related to excitatory neuronal damage and death. In the present study, oxidative stress evoked by glutaminergic and muscarinic receptors, and its modulation by an environmental toxin, lead, was studied in a human neuroblastoma cell line. The results of the present study show that human SH-SY5Y neuroblastoma cells express glutamate receptor subtypes. Activation of these receptors elicits functional intracellular calcium responses. Their stimulation by glutamate increases the production of reactive oxygen species although this is seen only after the impairment of the cellular glutathione defense system. Glutamate together with lead causes sustained production of reactive oxygen intermediates and subsequent oxidative stress. Protein kinase C may have an important role in the onset of oxidative stress because the production of reactive oxygen species by glutamate is completely inhibited by a protein kinase C inhibitor. Moreover, protein kinase C inhibition together with lead treatment causes oxidative stress. This may be due to modulation of the phosphorylation status of protein kinase C target proteins. The stimulation of cholinergic muscarinic receptors seems to increase the production of reactive oxygen intermediates in this cell line; cholinergic-induced oxidative stress seems to be protein kinase C-controlled and to be due to increased production of the superoxide anion. The principal route for phorbol ester-induced differentiation of SH-SY5Y cells may be down-regulation of protein kinase C. Also the differentiation of these cells promoted by lead seems to be under the partial control of protein kinase C. The present findings shed new light on the role of the glutaminergic and cholinergic neurotransmitter systems in oxidative stress. Also, the SH-SY5Y cell line proved to be an effective tool in investigating the effects of stimulation of different receptor systems and their modulation by lead. This study proposes a new mechanism for lead neurotoxicity through amplification of glutamate-mediated cellular activation

Radon transport to indoor air in groundwater plants as a by-effect of different water treatments

Radon released from groundwater into indoor air is the main radiation safety problem for water treatment plants. This study investigated the release of radon from different water treatment processes and the effect of ventilation on the indoor radon concentration at six waterworks. In addition to various aeration processes, groundwater pretreatments, such as activated carbon and pre-ozonation, were demonstrated to be associated with the indoor radon concentration. This study revealed that accurate assessment of radon exposure at water treatment plants is very difficult because of the large and sudden temporal variations in the radon concentration and smaller local variations that follow the steps of the water treatment process and ventilation. Based on the study, concrete proposals are also presented for improving radiation safety and the reliability of measurements

Can activated carbon filtration of groundwater cause radiation safety problems?

Activated carbon filtration is commonly used to remove groundwater contaminants in water utilities. During its use, also groundwater radonis adsorbed on activated carbon where it radioactively decays to Pb-210 within a few days. The intermediate stages of radioactive decayproduce gamma radiation outside the filter, which can be harmful to health. In addition, EU legislation sets a clearance level of 1 kBq/kgfor the Pb-210 concentration of waste, above which disposal of carbon waste can be complicated, depending on national legislation. Thisstudy focused on activated carbon filters from two groundwater plants. Measurements were made over the service lifetime of the activatedcarbon and included measurements of adsorption of radon from water to carbon, radiation dose rates outside the filters and Pb-210 concentrations in the carbon. The study observed a rapid decrease in the radon adsorption rate of activated carbon during the first year of use. This phenomenon has a significant effect on the concentration of Pb-210 in the activated carbon waste at the end of service life. The calculated forecast model clearly showed that the risk of exceeding the clearance level of Pb-210 increases if the radon concentration in the raw water exceeds 100 Bq/L

Relevance of radon progeny measurements for the assessment of inhalation doses in groundwater utilities

The high radon concentrations measured in the indoor air of groundwater facilities and the prevalence of the problem have been known for several years. Unlike in other workplaces, in groundwater plants, radon is released into the air from the water treatment processes. During the measurements of this study, the average radon concentrations varied from 500 to 8800 Bq m–³. In addition, the indoor air of the treatment plants is filtered and there are no significant internal aerosol sources. However, only a few published studies on groundwater plants have investigated the properties of the radon progeny aerosol, such as the equilibrium factor (F) or the size distribution of the aerosol, which are important for assessing the dose received by workers. Moreover, the International Commission on Radiological Protection has not provided generic aerosol parameter values for dose assessment in groundwater treatment facilities. In this study, radon and radon progeny measurements were carried out at three groundwater plants. The results indicate surprisingly high unattached fractions (fp = 0.27–0.58), suggesting a low aerosol concentration in indoor air. The corresponding F values were 0.09–0.42, well below those measured in previous studies. Based on a comparison of the effective dose rate calculations, either the determination of the fp or, with certain limitations, the measurement of radon is recommended. Dose rate calculation based on the potential alpha energy concentration alone proved unreliable