On the contribution of the phagocytosis and the solubilization to the iron oxide nanoparticles retention in and elimination from lungs under long-term inhalation exposure

The aim of our study was to test a hypothesis according to which the pulmonary clearance vs. retention of metal oxide nanoparticles (NPs) is controlled not only by physiological mechanisms but also by their solubilization which in some cases may even prevail. Airborne Fe2O3 NPs with the mean diameter of 14±4nm produced by sparking from 99.99% pure iron rods were fed into a nose-only exposure tower. Rats were exposed to these NPs for 4h a day, 5days a week during 3, 6 or 10 months at the mean concentration of 1.14±0.01mg/m(3). NPs collected from the air exhausted from the exposure tower proved insoluble in water but dissolved markedly in the cell free broncho-alveolar lavage fluid supernatant and in the sterile bovine blood serum. The Fe2O3 content of the lungs and lung-associated lymph nodes was measured by the Electron Paramagnetic Resonance (EPR) spectroscopy. We found a relatively low but significant pulmonary accumulation of Fe2O3, gradually increasing with time. Besides, we obtained TEM-images of nanoparticles within alveolocytes and the myelin sheaths of brain fibers associated with ultrastructural damage. We have developed a multicompartmental system model describing the toxicokinetics of inhaled nanoparticles after their deposition in the lower airways as a process controlled by their (a) high ability to penetrate through the alveolar membrane; (b) active endocytosis; (c) in vivo dissolution. To conclude, both experimental data and the identification of the system model confirmed our initial hypothesis and demonstrated that, as concerns iron oxide NPs of the dimensions used, the dissolution-depending mechanisms proved to be dominant.

[Combined subchronic toxicity of nickel and manganese oxides nanoparticles, and its decrease due to bioprotectors complex]

Stable suspensions of NiO and/or Mn304 nanoparticles with average diameter 16,7?8,2 nm and 18,4?5,4 nm respectively, obtained via laser ablation of the metals with 99,99% purification in deionized water, were injected intraperitoneally into rats in dose of 0,5 mg or 0,25 mg three times per week up to 18 times separately or in various dose combinations. A group of rats received combined injections of nanoparticles in the highest dose or merely water with oral <<bioprotector complex>> containing pectin, vitamins A, C and E, glutamate, glycine, N-acetylcysteine, selenium, iodine and polyunsaturated fatty acids of omega-3 class. Intoxication development was assessed through multiple functional parameters and histologic changes in liver, spleen, kidneys and brain. Nickel and manganese accumulation in these organs was measured-via various methods. Both types of metallic oxide nanoparticles appeared to be hazardous for body, but Mn304 caused more harm according to major nonspecific toxicity manifestations. Moreover, they caused more intense injury to caudate nucleus and hippocamp neurons - that can be considered as an experimental model of manganese parkinsonism. Mathematic analysis based on response pattern revealed ambiguity of the combined toxicity type, depending on the effects assessed and on its level. Due to the bioprotector complex, organic and systemic toxicity and genotoxicity of Mn304 and NiO nanoparticles combined were diminished.

[Increasing resistance against hazardous effects of metals-containing nanoparticles as a prospective approach to health risks management]

Extremely high toxicity of metal-containing nanoparticles necessitates search of methods to increase body resistance against its harmful effects. The authors' experiments summarized in the article demonstrated that some combinations of certain biologically active substances selected according to sound theoretic background and prescribed in harmless doses can significantly decrease integral and specific manifestations of organ and system toxicity and even genotoxicity of such nanoparticles. Further development of this research direction should be recommended for practical implementation.

[Health risks for residents of cities with developed copper industry]

The study results stressed considerable contribution of technogenic environmental pollution in cities with developed copper industry into individual health risk of Sverdlovsk region population.

Attenuation of Combined Nickel(II) Oxide and Manganese(II, III) Oxide Nanoparticles' Adverse Effects with a Complex of Bioprotectors

Stable suspensions of NiO and Mn₃O₄ nanoparticles (NPs) with a mean (±s.d.) diameter of 16.7±8.2 and 18.4±5.4 nm, respectively, purposefully prepared by laser ablation of 99.99% pure nickel or manganese in de-ionized water, were repeatedly injected intraperitoneally (IP) to rats at a dose of 2.5 mg/kg 3 times a week up to 18 injections, either alone or in combination. A group of rats was injected with this combination with the background oral administration of a "bio-protective complex" (BPC) comprising pectin, vitamins A, C, E, glutamate, glycine, N-acetylcysteine, selenium, iodide and omega-3 PUFA, this composition having been chosen based on mechanistic considerations and previous experience. After the termination of injections, many functional and biochemical indices and histopathological features (with morphometric assessment) of the liver, spleen, kidneys and brain were evaluated for signs of toxicity. The Ni and Mn content of these organs was measured with the help of the atomic emission and electron paramagnetic resonance spectroscopies. We obtained blood leukocytes for performing the RAPD (Random Amplified Polymorphic DNA) test. Although both metallic NPs proved adversely bio-active in many respects considered in this study, Mn₃O₄-NPs were somewhat more noxious than NiO-NPs as concerns most of the non-specific toxicity manifestations and they induced more marked damage to neurons in the striatum and the hippocampus, which may be considered an experimental correlate of the manganese-induced Parkinsonism. The comparative solubility of the Mn₃O₄-NPs and NiO-NPs in a biological medium is discussed as one of the factors underlying the difference in their toxicokinetics and toxicities. The BPC has attenuated both the organ-systemic toxicity and the genotoxicity of Mn₃O₄-NPs in combination with NiO-NPs.

Further development of the theory and mathematical description of combined toxicity: An approach to classifying types of action of three-factorial combinations (a case study of manganese-chromium-nickel subchronic intoxication)

For characterizing the three-factorial toxicity, we proposed a new health risk-oriented approach, the gist of which is a classification of effects depending on whether a binary combined toxicity's type remains virtually the same or appears to be either more or less adverse when modeled against the background of a third toxic. To explore possibilities of this approach, we used results of an experiment in which rats had been injected ip 3 times a week (up to 20 injections) with a water solution of either one of the toxics (Mn, Ni or Cr-VI salts) in a dose equivalent to 0.05 LD50, or any two of them, or all the three in the same doses, the controls receiving injections of the same volume of distilled water (4mL per rat). Judging by more than 30 indices for the organism's status, all exposures caused subchronic intoxication of mild to moderate strength. For each two-factorial exposure, we found by mathematical modeling based on the isobolograms that the binary combined subchronic toxicity either was of additive type or departed from it (predominantly toward subadditivity) depending on the effect assessed, dose, and effect level. For the three-factorial combination, different classes of effects were observed rather consistently: class A - those regarding which the third toxic's addition made the binary toxicity type more unfavorable for the organism, class B - those regarding which the result was opposite, and class C - those regarding which the type of binary combined toxicity on the background of a third toxic virtually remained the same as in its absence. We found a complicated reciprocal influence of combined metals on their retention in kidneys, liver, spleen and brain which might presumably be one of the possible mechanisms of combined toxicity, but the lack of an explicit correspondence between the above influence and the influence on toxicity effects suggests that this mechanism is not always the most important one. The relevance of the proposed classification to health risk analysis and management is briefly discussed.

Some inferences from in vivo experiments with metal and metal oxide nanoparticles: the pulmonary phagocytosis response, subchronic systemic toxicity and genotoxicity, regulatory proposals, searching for bioprotectors (a self-overview)

The purpose of this paper is to overview and summarize previously published results of our experiments on white rats exposed to either a single intratracheal instillation or repeated intraperitoneal injections of silver, gold, iron oxide, copper oxide, nickel oxide, and manganese oxide nanoparticles (NPs) in stable water suspensions without any chemical additives. Based on these results and some corroborating data of other researchers we maintain that these NPs are much more noxious on both cellular and systemic levels as compared with their 1 μm or even submicron counterparts. However, within the nanometer range the dependence of systemic toxicity on particle size is intricate and non-unique due to complex and often contra-directional relationships between the intrinsic biological aggressiveness of the specific NPs, on the one hand, and complex mechanisms that control their biokinetics, on the other. Our data testify to the high activity of the pulmonary phagocytosis of NPs deposited in airways. This fact suggests that safe levels of exposure to airborne NPs are possible in principle. However, there are no reliable foundations for establishing different permissible exposure levels for particles of different size within the nanometric range. For workroom air, such permissible exposure levels of metallic NP can be proposed at this stage, even if tentatively, based on a sufficiently conservative approach of decreasing approximately tenfold the exposure limits officially established for respective micro-scale industrial aerosols. It was shown that against the background of adequately composed combinations of some bioactive agents (comprising pectin, multivitamin-multimineral preparations, some amino acids, and omega-3 polyunsaturated fatty acid) the systemic toxicity and even genotoxicity of metallic NPs could be markedly attenuated. Therefore we believe that, along with decreasing NP-exposures, enhancing organisms’ resistance to their adverse action with the help of such bioprotectors can prove an efficient auxiliary tool of health risk management in occupations connected with them.

[MANAGEMENT OF THE MULTIPLE ENVIRONMENTAL RISK FOR THE HEALTH OF THE POPULATION OF INDUSTRIALIZED CITIES OF THE SVERDLOVSK REGION]

In the Sverdlovsk region for the assessment and management of environment and health of the population over more than 10 years there is used a methodology for the assessment of the multiple environmental risk, allowing to identify priority routes of toxicants entering the body, to evaluate the possible dose-response relationships and elaborate targeted measures for their correction. In the article there is shown how are effective management decisions, elaborated on the base of the results of the assessment of multiple environmental risk to public health in cities of Pervouralsk and Revda of the Sverdlovsk region and directed to the mitigation of the exposure to chemical factors of the environment.

[APPROACHES TO ENHANCING THE ORGANISM'S RESISTANCE TO THE ADVERSE EFFECTS OF NANOMATERIALS AS EXAMPLIFIED BY NANOSILVER AND NANOCOPPER OXIDE]

Subchronic intoxications in rats induced by repeated intraperitoneal injections of stable water suspensions of silver or copper oxide nanoparticles in low dosage were manifested by adverse shifts in some functional and biochemical indices, by development of histo-structural changes in different tissues and by poly-organ fragmentation of DNA. All these manifestations of toxicity were substantially attenuated against the background of parallel oral administration of bioprotective complexes comprising vitamins, trace elements, pectin, some amino acids and a fish oil preparation rich in omega-3 fee fatty acids, this composition has been adjusted to mechanisms of action of this or that nanomaterial.

Some characteristics of free cell population in the airways of rats after intratracheal instillation of copper-containing nano-scale particles

We used stable water suspensions of copper oxide particles with mean diameter 20 nm and of particles containing copper oxide and element copper with mean diameter 340 nm to assess the pulmonary phagocytosis response of rats to a single intratracheal instillation of these suspensions using optical, transmission electron, and semi-contact atomic force microscopy and biochemical indices measured in the bronchoalveolar lavage fluid. Although both nano and submicron ultrafine particles were adversely bioactive, the former were found to be more toxic for lungs as compared with the latter while evoking more pronounced defense recruitment of alveolar macrophages and especially of neutrophil leukocytes and more active phagocytosis. Based on our results and literature data, we consider both copper solubilization and direct contact with cellular organelles (mainly, mitochondria) of persistent particles internalized by phagocytes as probable mechanisms of their cytotoxicity.

Toxicodynamic and toxicokinetic descriptors of combined chromium (VI) and nickel toxicity

After repeated intraperitoneal injections of nickel and chromium (VI) salts to rats, we found, and confirmed by mathematical modeling, that their combined subchronic toxicity can either be of additive type or depart from it (predominantly toward subadditivity) depending on the effect assessed. Against the background of moderate systemic toxicity, the combination under study proved to possess a marked additive genotoxicity assessed by means of the random amplification of polymorphic DNA test. We also demonstrated that chromium and nickel reciprocally influenced the retention of these metals in some organs (especially in the spleen) but not their urinary excretion in this study.

Subchronic toxicity of copper oxide nanoparticles and its attenuation with the help of a combination of bioprotectors

In the copper metallurgy workplace air is polluted with condensation aerosols, which a significant fraction of is presented by copper oxide particles<100 nm. In the scientific literature, there is a lack of their in vivo toxicity characterization and virtually no attempts of enhancing organism's resistance to their impact. A stable suspension of copper oxide particles with mean (±SD) diameter 20±10 nm was prepared by laser ablation of pure copper in water. It was being injected intraperitoneally to rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week up to 19 injections. In parallel, another group of rats was so injected with the same suspension against the background of oral administration of a "bio-protective complex" (BPC) comprising pectin, a multivitamin-multimineral preparation, some amino acids and fish oil rich in ω-3 PUFA. After the termination of injections, many functional and biochemical indices for the organism's status, as well as pathological changes of liver, spleen, kidneys, and brain microscopic structure were evaluated for signs of toxicity. In the same organs we have measured accumulation of copper while their cells were used for performing the Random Amplification of Polymorphic DNA (RAPD) test for DNA fragmentation. The same features were assessed in control rats infected intraperitoneally with water with or without administration of the BPC. The copper oxide nanoparticles proved adversely bio-active in all respects considered in this study, their active in vivo solubilization in biological fluids playing presumably an important role in both toxicokinetics and toxicodynamics. The BPC proposed and tested by us attenuated systemic and target organs toxicity, as well as genotoxicity of this substance. Judging by experimental data obtained in this investigation, occupational exposures to nano-scale copper oxide particles can present a significant health risk while the further search for its management with the help of innocuous bioprotectors seems to be justified.

Does a concomitant exposure to lead influence unfavorably the naphthalene subchronic toxicity and toxicokinetics?

Rats were given 20 times during 40 d either naphthalene per gavage or the same and lead acetate intraperitoneally in single doses corresponding to 5% of the respective 50% lethal doses. The concomitant exposure to lead not only added some typical indicators of lead toxicity to the moderate naphthalene intoxication picture but also exaggerated some less specific indices for intoxication. However, a number of such indices testified to attenuation of naphthalene's adverse effects under the impact of lead. Lead also lowered urinary excretion of both total and conjugated naphthalene, while the free- to total naphthalene ratio in urine sharply increased. These results corroborate implicitly the initial hypothesis that lead, being an inhibitor of cytochrome P450, hinders phase I of the naphthalene biotransformation and, thus, the formation of derivates which can be more toxic but are capable of entering into reactions of conjugation with resulting detoxication and elimination of naphthalene from the body.

Attenuation of subchronic formaldehyde inhalation toxicity with oral administration of glutamate, glycine and methionine

Inhalation exposure of outbred female white rats (initial age about 4 months) to formaldehyde vapours (12.8 ± 0.69 mg/m(3)) 4h per day, 5 days per week during 10 weeks induced statistically significant changes in some indices characterizing differential WBC count, functional status of the central nervous system and liver, redox and porphyrin metabolisms, bone marrow micronuclei count as well as free amino acid spectrum of the blood serum. The development of intoxication was accompanied by increased urinary excretion of formaldehyde, formic acid and methanol. Daily oral administration of glutamate (150-180 mg), glycine (12 mg) and methionine (50mg) in combination rendered all of the formaldehyde's toxic effects reduced. This administration also caused a significant increase in the ratio between the rates of excretion of formic acid and non-metabolized formaldehyde. This shift supposedly reflects activation of oxidative detoxifying biotransformation of formaldehyde. Taking into consideration that the combination of amino acids used in this study proved innocuous in protectively effective doses, the administration in this combination may be recommended to humans exposed to high levels of formaldehyde in workplace or ambient air.

Interaction of iron oxide Fe3O4 nanoparticles and alveolar macrophages in vivo

Aqueous suspension of magnetite nanoparticles with primary diameter of 10 nm were intratracheally administered into rat lungs. In 24 h, cells were isolated from bronchoalveolar lavage and examined under a transmission electron microscope. Alveolar macrophages demonstrated ability to actively uptake single nanoparticles and small aggregates composed of such particles, which then formed larger conglomerates inside fused phagosomes. Some of these mature phagosomes shed the membrane and free nanoparticles closely interacted with nuclear membrane and with cristae and mitochondrial membranes thereby inflicting pronounced damage to these intracellular structures. The loss of primary lysosomes can be viewed as indirect evidence attesting to the role played by diffusion of lysosomal hydrolytic enzymes in the final destruction of the alveolar macrophages provoked by nanoparticles.

An Approach to Tentative Reference Levels Setting for Nanoparticles in the Workroom Air Based on Comparing Their Toxicity with That of Their Micrometric Counterparts: A Case Study of Iron Oxide Fe3O4

We overview the state of the art in the field of safe exposure levels setting for nanomaterials together with the previously published results of our experimental investigations characterizing comparative toxicity of the iron oxide (magnetite) in the form of microparticles and nanoparticles of different size and comparative activity of the defensive alveolar phagocytosis response to their pulmonary deposition. An approach to the substantiation of acceptable workplace exposure limits of metallic nanoparticles is discussed and, specifically, the tentative reference level for magnetite nanoparticles is recommended.

Combined subchronic fluoride-lead intoxication and its attenuation with the help of a complex of bioprotectors

BACKGROUND

Combined toxicity of lead and fluoride has been studied insufficiently, and there is no known information about attempts to inhibit it with any bioprotectors.

METHODS

Lead acetate and sodium fluoride, administered separately or in combination, were injected i.p. to rats at isoeffective sublethal doses 3 times a week for 6 weeks. Some of the rats were exposed to the same combination against the background of oral administration of a bioprotector complex (BPC) comprising pectin, glutamate, and multivitamin/multimineral preparations. Following exposure, functional and biochemical indices and histopathological examinations of the femur of exposed and control rats were evaluated for signs of toxicity.

RESULTS

We have shown that with regard to a number of effects on the organism level the combined toxicity of lead and fluoride may be evaluated as additive or even superadditive, but lead reduces fluoride accumulation in the bone, and pathological changes in the bone tissue proved to be less marked for combined exposure compared with separate exposures. The BPC has been demonstrated to attenuate a range of the combined harmful effects of lead and fluoride, including those on the bone tissue.

CONCLUSIONS

In spite of the fact that fluoride and lead may reciprocally attenuate their harmful effects on the bone tissue in case of combined exposure, they prove to be more toxic for soft tissues just in combination than when administered separately. The development of combined intoxication may be substantially inhibited by means of the tested set of innocuous biologically active agents.

[Comparative experimental assessment of the impact of gold and silver nanoparticles on the phagocyting cells of the lower airways]

Judging by the cytological characteristics of the free cell population of the lower airways obtained with assistance of the bronchoalveolar lavage in 24 hours after the intratracheal instillation of equal doses of equidimensional gold or silver nanoparticles, both metals result in active recruitment of phagocytes with domination of neutrophile leukocytes, especially marked after the instillation of the nanosilver. The higher ratio of these cells count to that of alveolar macrophages gives evidence for the significantly higher cytotoxicity of the nanosilver comparing with both nanogold and even the smallest silver particles in the micrometric range. Transmission electron microscopy demonstrates similar pictures of intracellular distribution and ultra-structural damages caused by internalized nanoparticles in both types of phagocytes, while there are significant differences between cells under impact of nanosilver vs. those under impact of nanogold. The highest importance is higher propensity of the nanosilver particles to aggregation and to ingression into mitochondria with damaging these organelles.

Subchronic systemic toxicity and bioaccumulation of Fe3O4 nano- and microparticles following repeated intraperitoneal administration to rats

Aqueous suspensions of 10 nm, 50 nm, or 1 μm Fe(3)O(4) particles were injected intraperitoneally (ip) to rats at a dose of 500 mg/kg in 4 mL of sterile deionized water 3 times a week for 5 weeks. Following exposure, functional and biochemical indices and histopathological examinations of spleen and liver tissues of exposed rats were evaluated for signs of toxicity. The iron content of the blood was measured photometrically, and that of the liver and the spleen by atomic adsorption spectroscopy (AAS) and electron paramagnetic resonance (EPR) methods. It was found that, given equal mass doses, Fe(3)O(4) nanoparticles possess considerably higher systemic toxicity than microparticles, but within the nanometric range the relationship between particle size and resorptive toxicity is intricate and nonunique. The latter fact may be attributed to differences in different nanoparticles' toxicokinetics, which are controlled by both more or less substantial direct penetration of nanoparticles through biological barriers and their unequal solubility.

[Comparative evaluation of alveolar phagocytosis response to intratracheally applied magnetite (Fe3O4) in nano- and micrometer ranges]

The authors compared cytotoxicity of magnetite (Fe3O4) particles in nanometric ranges (10 nm and 50 nm) and micrometer range (1 microm), analyzing changes in cellular subunits of bronchoalveolar lavage in 24 hours after intratracheal application of the particles. Findings are that the nanoparticles are more biologically aggressive than the micrometric particles, but induce more active and effective defensive reaction of alveolar fagocytosis.

[Analysis of time series to establish the relationship of respiratory symptomatology in children to ambient air pollution fluctuations]

Eighty-five junior schoolchildren from Nizhni Tagil were examined on the basis of daily recording of respiratory and allergic symptoms by parents and continuous monitoring of ambient air pollution with suspended matter and irritating gases. Regression analysis of the findings has ascertained the adverse impact of even relatively small daily pollution peaks (generally not greater that the established mean maximum daily permissible concentrations) on acute upper and deep airway responses in junior and middle schoolchildren. The principal results of the study agree with those of the studies in the West, although the latter concerned the concentrations of dust particles that are higher and vary in wider ranges than in this study. It is recommended that this methodology be widely introduced into practice in order to establish correlations between ambient air pollution and children's impaired health.