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Potential toxic effects of iron oxide nanoparticles in in vivo and in vitro experiments

The aim of this study was to determine the potential toxic effects of iron(II,III)oxide nanoparticles (IONPs). In in vivo experiments, the toxic effects of IONPs were monitored in adult male Wistar rats by morphological methods after a single intratracheal instillation. For the control group 1 ml of physiological saline per animal was given, and the treatment group received the same volume of a suspension containing 1 and 5 mg kg−1 body weight IONPs. Lungs and internal organs underwent histopathological examination after 1, 3, 7, 14 and 30 days. The mutagenic effect of these nanoparticles was evaluated by the bacterial reverse mutation assay on Salmonella typhimurium TA98, TA100, TA1535 and TA1537 strains, and on Escherichia coli WP2uvrA strain, in the presence and absence of the mammalian metabolic activation system S9. The in vitro cytotoxic effect of IONPs was also examined in Vero cells after short‐term (4 h) and long‐term (24 h) exposure. There were no pathological changes in examined internal organs, except a very weak pulmonary fibrosis developing by the end of the first month in the treated rats. While in vitro MTT assay showed a moderate cytotoxic effect, IONPs proved to be devoid of mutagenic effect in the bacterial systems tested. The results may be a useful extension of our knowledge on the safety of magnetite nanoparticles in view of their possible medical applications, such as in hyperthermia and magnetic resonance imaging. Copyright

Behavioral and neurotoxicological effects of subchronic manganese exposure in rats.

In male Wistar rats, behavioral and electrophysiological investigations, and blood and brain manganese level determinations, were performed; during 10 weeks treatment with low-dose manganese chloride and a 12 weeks post-treatment period. Three groups of 16 animals each received daily doses of 14.84 and 59.36mg/kg b.w. MnCl(2) (control: distilled water) via gavage. During treatment period, Mn accumulation was seen first in the blood, then in the brain samples of the high-dose animals. Short- and long-term spatial memory performance of the treated animals decreased, spontaneous open field activity (OF) was reduced. The number of acoustic startle responses (ASR), and the pre-pulse inhibition (PPI) of these, diminished. In the cortical and hippocampal spontaneous activity, power spectrum was shifted to higher frequencies. The latency of the sensory evoked potentials increased, and their duration, decreased. By the end of the post-treatment period, Mn levels returned to the control in all samples. The impairment of long-term spatial memory remained, as did the number of acoustic startle responses. Pre-pulse inhibition, however, returned to the pre-treatment levels. The changes of the open field activity disappeared but a residual effect could be revealed by administration of d-amphetamine. The electrophysiological effects were partially reversed. By applying a complex set of methods, it was possible to obtain new data for a better-based relationship between the known effects of Mn at neuronal level and the behavioral and electrophysiological outcomes of Mn exposure.

Nervous system effects in rats on subacute exposure by lead-containing nanoparticles via the airways

Context and objective: Lead (Pb) is a heavy metal harmful for human health and environment. From leaded gasoline (still used in certain countries), and in Pb processing and reprocessing industries, airborne particles are emitted which can be inhaled. In such exposure, the size of particles entering the airways is crucial. The nervous system is a primary target for Pb, and consequences like occupational neuropathy and delayed mental development of children are well-known. The aim of this work was to investigate the neurotoxicity of Pb nanoparticles (NPs) applied into the airways of rats. Methods: Nano-sized lead oxide particles (mean diameter ca. 20 nm) were suspended in distilled water and instilled into the trachea of adult male Wistar rats (in doses equivalent to 2 and 4 mg/kg Pb), 5 times a week for 3 and 6 weeks. At the end, open field motility was tested, then central and peripheral nervous activity was recorded in urethane anesthesia. Results and conclusion: The treated rats’ body weight gain was significantly lower than that of the controls from the 3rd week onwards, and the weight of their lungs was significantly increased. Horizontal motility increased while vertical motility decreased. Spontaneous cortical activity was shifted to higher frequencies. The somatosensory cortical evoked potential showed increased latency and decreased frequency-following ability, and similar alterations were seen in the tail nerve. Significant Pb deposition was measured in blood, brain, lung and liver samples of the treated rats. The experiments performed seem to constitute an adequate model of the human effects of inhaled Pb NPs.

Subacute intratracheal exposure of rats to manganese nanoparticles: Behavioral, electrophysiological, and general toxicological effects

The toxicity of manganese-containing airborne particles is an important occupational and environmental problem. In this work, adult male Wistar rats were treated with a nanosuspension of MnO2 of approximately 23 nm nominal particle diameter, instilled into the trachea for 3, 6, and 9 wk in doses of 2.63 and 5.26 mg Mn/kg. The animals’ body weight was checked weekly. At the end of treatment, the rats’ spontaneous motility was tested in an open field box. Then, spontaneous and stimulus-evoked cortical activity and action potential of the tail nerve were recorded in urethane anesthesia. The rats were finally dissected, organs weights were measured, and the presence of excess Mn in lung and brain samples was determined using scanning electron microscopy with energy-dispersive x-ray spectroscopy. While control rats had normal weight gain, the body weights of the treated rats ceased to grow from wk 6 on. The relative weight of the lungs increased in the treated rats, and that of the liver decreased, in a dose- and time-dependent manner; Mn was detected in their lung and brain samples. In the open field activity, the percentage of ambulation and rearing decreased while local activity and immobility increased. The latency of the evoked potentials was lengthened, and the conduction velocity of the tail nerve decreased. These results indicate that the Mn content of instilled nanoparticles had access from the airways to the brain, and the resulting damage could be investigated in animals using neuro-functional and general toxicological endpoints.

Behavioral and general effects of subacute oral arsenic exposure in rats with and without fluoride

Consequences of oral arsenic and fluoride exposure on motor behavior and general toxicity were modeled in young adult male rats which received sodium (meta)arsenite (10 mg/kg b.w.), sodium fluoride (5 mg/kg b.w.), and their combination by gavage, once daily, 5 days a week for 6 weeks. After 6 weeks, 6 animals per group were dissected, while the other 6 were kept for 6 more weeks untreated. Body weight, together with food and water consumption, was measured daily. Arsenic, alone or along with fluoride, caused significant decrease in rearing, and increase in immobility and local activity in the open field in the 3rd and 6th week. By the 12th week, these changes mostly diminished. Weight gain, and food and water consumption were significantly reduced by arsenic but normalized post treatment. Fluoride had no own effect and mostly no influence on effects of arsenic. Massive deposition of arsenic in the rats’ blood, cerebral cortex, and liver by the 6th week, and partial elimination by the 12th week, was seen. The results underline the risk of neuro-functional damage by arsenic and call for further investigations.

Functional neurotoxicity and tissue metal levels in rats exposed subacutely to titanium dioxide Nanoparticles via the airways

Background and purpose Nanoparticles of titanium dioxide are suspected neurotoxic agents and have numerous applications possibly resulting in human exposure by several ways including inhalation. In the present work, rats were exposed to spherical TiO2 nanoparticles of two different sizes by the intratracheal route. It was investigated how the neuro-functional alterations, detected by electrophysiological and behavioral methods, were related to the concentration of Ti in the tissue samples and what the influence of the size of the NPs was. Methods Rats (young adult Wistar males, 10/group) were exposed to TiO2 nanoparticles of ca. 10 and 100 nm diameter (suspension medium: neutral PBS with 1% hydroxyethyl cellulose) by intratracheal instillation in 5 and 18 mg/kg b.w. dose; 5 days per week for 6 weeks. Controls were instilled with saline, and vehicle controls, with the suspension medium. To see general toxicity, body weight was checked daily, and organ weights were measured at the end of experiment. Grip strength test, to assess motor function damage, was done before and after the 6-week treatment. Finally, the rats were anesthetized with urethane, spontaneous cortical activity and sensory evoked potentials were recorded, then the rats were dissected and tissue samples were taken for Ti level measurement. Results Body weight gain indicated no general toxicity, and no significant change in the relative organ weights, except that of the lungs, was seen. However, change of time-to-fall in the grip strength test, and latency of cortical evoked po-tentials, were altered in the treated groups, indicating functional damage. Correlation of these alterations with the cortical Ti level was dissimilar for the two sizes of nanoparticles. Conclusion The results provided further support to the functional neurotoxicity of TiO2 nanoparticles. The exact role of particle size, and the mechanisms involved, remain to be elucidated.

Effects of environmental xenobiotics on the nervous system in animal experiments

Introduction Food is a major route by which xenobiotics – mostly produced and emitted by man – can cause human exposure. Pesticides are deliberately brought into the environment in huge amounts in order to eliminate, by toxic action, insects, fungi, weeds etc. endangering agricultural production; but, due to incomplete selectivity and/or persistence, can expose field workers and food consumers (Conway and Pretty, 1991; Faheed, 2005). Modern insecticides were designed to attack the nervous system of insects and other arthropods. Some of them, however, turned out to be persistent and ecotoxic (WHO, 1989a,b) while others (e.g., organophosphates: WHO, 1986) have a high acute human toxicity. The use of heavy metals for centuries resulted in considerable levels of lead, mercury etc. in soil, water and sometimes food samples (ATSDR, 1999a,b; Jolánkai et al., 2006; Osztoics et al., 2005). The ill effects of heavy metals on the human nervous system, form peripheral nerves to behavioral and learning abnormalities, is well known. Neurotoxicity, seems to be an important aspect of environmental xenobiotics. Functional or structural damage of the nervous system can compromise an individual’s fitness for work and general quality of life. Neurotoxic influences during foetal and early postnatal development, an especially sensitive phase, can have lasting effect on the mental performance in the adulthood and so affect the most precious quality of human resources. At the Department of Public Health, University of Szeged Faculty of Medicine, the neurotoxicity of environmental xenobiotics has been investigated in animal experiments for ca. 20 years, applying electrophysiological and behavioral techniques. In this paper, examples of our results are given.