Effects of simulated downwind coal combustion emissions on pre-existing allergic airway responses in mice

Context: Coal-fired power plant emissions can contribute a significant portion of the ambient air pollution in many parts of the world.

Objective: We hypothesized that exposure to simulated downwind coal combustion emissions (SDCCE) may exacerbate pre-existing allergic airway responses.

Methods: Mice were sensitized and challenged with ovalbumin (OVA). Parallel groups were sham-sensitized with saline. Mice were exposed 6?h/day for 3 days to air (control, C) or SDCCE containing particulate matter (PM) at low (L; 100 μg/m³), medium (M; 300 μg/m³), or high (H; 1000 μg/m³) concentrations, or to the H level with PM removed by filtration (high-filtered, HF). Immediately after SDCCE exposure, mice received another OVA challenge (pre-OVA protocol). In a second (post-OVA) protocol, mice were similarly sensitized but only challenged to OVA before air/SDCCE. Measurement of airway hyperresponsiveness (AHR), bronchoalveolar lavage (BAL), and blood collection were performed ~24?h after the last exposure.

Results: SDCCE significantly increased BAL macrophages and eosinophils in OVA-sensitized mice from the post-OVA protocol. However, there was no effect of SDCCE on BAL macrophages or eosinophils in OVA-sensitized mice from the pre-OVA protocol. BAL neutrophils were elevated following SDCCE in both protocols in nonsensitized mice. These changes were not altered by filtering out the PM. In the post-OVA protocol, SDCCE decreased OVA-specific IgG₁ in OVA-sensitized mice but increased levels of total IgE, OVA-specific IgE and OVA-specific IgG₁ and IgG_2a in non-sensitized animals. In the pre-OVA protocol, SDCCE increased OVA-specific IgE in both sensitized and non-sensitized animals. Additionally, BAL IL-4, IL-13, and IFN-γ levels were elevated in sensitized mice.

Conclusion: These results suggest that acute exposure to either the particulate or gaseous phase of SDCCE can exacerbate various features of allergic airway responses depending on the timing of exposure in relation to allergen challenge.     

Inhalation exposure of nano-scaled titanium dioxide (TiO2) particles alters the inflammatory responses in asthmatic mice

Abstract

Context: Titanium dioxide (TiO₂) nanoparticles (NPs) are regarded as relatively non-toxic in concentrations occurring in occupational environments. Nevertheless, it is conceivable that adverse health effects may develop in sensitive populations such as individuals with respiratory diseases.

Objective: We investigated whether single or repeated exposure to TiO₂ could aggravate inflammatory responses in naïve mice and mice with ovalbumin (OVA)-induced airway inflammation.

Methods: Exposure to aerosolized TiO₂ was performed during OVA sensitization, before, or during the OVA challenge period. The effects on respiratory physiology, inflammatory cells in bronchoalveolar lavage (BAL) and inflammatory mediators in BAL and serum were assessed 24?h after the last OVA challenge or TiO₂ exposure.

Results: A single exposure of TiO₂ had a marked effect on responses in peripheral airways and increasing infiltration of neutrophils in airways of naïve animals. Marked aggravation of airway responses was also observed in animals with allergic disease provided that the single dose TiO₂ was given before allergen challenge. Repeated exposures to TiO₂ during sensitization diminished the OVA-induced airway eosinophilia and airway hyperresponsiveness but concomitant exposure to TiO₂ during the OVA challenge period resulted in neutrophilic airway inflammation and a decline in general health condition as indicated by the loss of body weight.

Conclusion: We conclude that inhalation of TiO₂ may aggravate respiratory diseases and that the adverse health effects are highly dependent on dose and timing of exposure. Our data imply that inhalation of NPs may increase the risk for individuals with allergic airway disease to develop symptoms of severe asthma.     

Effects of Gasoline Engine Emissions on Preexisting Allergic Airway Responses in Mice

Gasoline-powered vehicle emissions contribute significantly to ambient air pollution. We hypothesized that exposure to gasoline engine emissions (GEE) may exacerbate preexisting allergic airway responses. Male BALB/c mice were sensitized by injection with ovalbumin (OVA) and then received a 10-min aerosolized OVA challenge. Parallel groups were sham-sensitized with saline. Mice were exposed 6 h/day to air (control, C) or GEE containing particulate matter (PM) at low (L), medium (M), or high (H) concentrations, or to the H level with PM removed by filtration (high-filtered, HF). Immediately after GEE exposure mice received another 10-min aerosol OVA challenge (pre-OVA protocol). In a second (post-OVA) protocol, mice were similarly sensitized but only challenged to OVA before air or GEE exposure. Measurements of airway hyperresponsiveness (AHR), bronchoalveolar lavage (BAL), and blood collection were performed ～24 h after the last exposure. In both protocols, M, H, and HF GEE exposure significantly decreased BAL neutrophils from nonsensitized mice but had no significant effect on BAL cells from OVA-sensitized mice. In the pre-OVA protocol, GEE exposure increased OVA-specific IgG₁ but had no effect on BAL interleukin (IL)-2, IL-4, IL-13, or interferon (IFN)-γ in OVA-sensitized mice. Nonsensitized GEE-exposed mice had increased OVA-specific IgG_2a, IgE, and IL-2, but decreased total IgE. In the post-OVA protocol, GEE exposure reduced BAL IL-4, IL-5, and IFN-γ in nonsensitized mice but had no effect on sensitized mice. These results suggest acute exposure to the gas–vapor phase of GEE suppressed inflammatory cells and cytokines from nonsensitized mice but did not substantially exacerbate allergic responses.     

Nano Titanium Dioxide Particles Promote Allergic Sensitization and Lung Inflammation in Mice

Abstract: The purpose of this study was to investigate whether photocatalytic TiO₂ nanoparticles have adjuvant effect, when administered in combination with ovalbumin (OVA) in mice. Mice were immunized via intraperitoneal injections of OVA, OVA + TiO₂ or OVA + Al(OH)₃ and challenged with aerosols of OVA. At the end of the study, serum was analysed for content of OVA‐specific IgE, IgG1 and IgG2a antibodies, and the bronchoalveolar lavage fluid (BALF) was analysed for content of inflammatory cells and levels of interleukin (IL)‐4, IL‐5, IL‐10 and interferon‐γ. The TiO₂ particles promoted a Th2 dominant immune response with high levels of OVA‐specific IgE and IgG1 in serum and influx of eosinophils, neutrophils and lymphocytes in BALF. The TiO₂ particles induced a significantly higher level of OVA‐specific IgE than the standard adjuvant Al(OH)₃. However, the two substances were comparable regarding the level of eosinophilic inflammation and interleukins present in BALF.     

No evidence of the genotoxic potential of gold,silver, zinc oxide and titanium dioxide nanoparticles in the SOS chromotest

Gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO₂ NPs) are widely used in cosmetic products such as preservatives, colorants and sunscreens. This study investigated the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO₂ NPs using the SOS chromotest with Escherichia coli PQ37. The maximum exposure concentrations for each nanoparticle were 3.23 mg l^–1 for Au NPs, 32.3 mg l^–1 for Ag NPs and 100 mg l^–1 for ZnO NPs and TiO₂ NPs. Additionally, in order to compare the genotoxicity of nanoparticles and corresponding dissolved ions, the ions were assessed in the same way as nanoparticles. The genotoxicity of the titanium ion was not assessed because of the extremely low solubility of TiO₂ NPs. Au NPs, Ag NPs, ZnO NPs, TiO₂ NPs and ions of Au, Ag and Zn, in a range of tested concentrations, exerted no effects in the SOS chromotest, evidenced by maximum IF (IFmax) values of below 1.5 for all chemicals. Owing to the results, nanosized Au NPs, Ag NPs, ZnO NPs, TiO₂ NPs and ions of Au, Ag and Zn are classified as non‐genotoxic on the basis of the SOS chromotest used in this study. To the best of our knowledge, this is the first study to evaluate the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO₂ NPs using the SOS chromotest. Copyright © 2012 John Wiley & Sons, Ltd.     

Nitrogen dioxide: no influence on allergic sensitization in an intranasal mouse model with ovalbumin and diesel exhaust particles

The role of traffic-related air pollution in the development of allergic diseases is still unclear. We therefore investigated if NO₂, an important constituent of traffic-related air pollution, promotes allergic sensitization to the allergen ovalbumin (OVA). We also examined if NO₂ influenced the allergy adjuvant activity of diesel exhaust particles (DEP). For this purpose, mice were exposed intranasally to OVA with or without DEP present, immediately followed by exposure to NO₂ (5 or 25 parts per million [ppm]) or room air for 4?h in whole body exposure chambers. Eighteen hours after the last of three exposures, the lungs of half of the animals were lavaged with saline and markers of lung damage and lung inflammation in the bronchoalveolar lavage fluid (BALF) were measured. Three weeks later, after intranasal booster immunizations with OVA, the levels of OVA-specific IgE and IgG2a antibodies in serum were determined. Both NO₂ (25?ppm) and DEP gave lung damage, measured as increased total protein concentration in BALF, whereas only NO₂ seemed to stimulate release of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α). In contrast, only DEP significantly increased the number of neutrophils. Furthermore, DEP in combination with OVA stimulated the production of serum allergen-specific IgE antibodies. NO₂, however, neither increased the production of allergen-specific IgE antibodies, nor influenced the IgE adjuvant activity of DEP. Thus, based on our findings, NO₂ seems to be of less importance than combustion particles in the development of allergic diseases after exposure to traffic-related air pollution.     

Allergen immunotherapy with nanoparticles containing lipopolysaccharide from Brucella ovis

The adjuvant and protective capacity against anaphylactic shock of the association between rough lipopolysaccharide of Brucella ovis (LPS) coencapsulated with ovalbumin (OVA), as a model allergen, in Gantrez^® AN nanoparticles was investigated. Several strategies were performed in order to study the adjuvant effect of the LPS either encapsulated or coating the nanoparticles. OVA, as well as LPS, was incorporated either during the manufacturing process (OVA-encapsulated or LPS-encapsulated nanoparticles, respectively) or after the preparation (OVA-coated or LPS-coated nanoparticles, respectively). After the administration of 10 μg of OVA incorporated in the different formulations, all the nanoparticles, with or without LPS, were capable of amplifying the immune response (IgG₁ and IgG_2a). However, in a model of sensitized mice to OVA, the formulation with OVA and LPS-entrapped inside the nanoparticles administered intradermally in three doses of 3 μg of OVA each was the only treatment that totally protected the mice from death after a challenge with an intraperitoneal injection of OVA. In contrast, the control group administered with OVA adsorbed onto a commercial alhydrogel adjuvant showed 80% mortality. These results are highly suggestive for the valuable use of Gantrez^® nanoparticles combined with rough LPS of B. ovis in immunotherapy.     

Allergen immunotherapy with nanoparticles containing lipopolysaccharide from Brucella ovis

The adjuvant and protective capacity against anaphylactic shock of the association between rough lipopolysaccharide of Brucella ovis (LPS) coencapsulated with ovalbumin (OVA), as a model allergen, in Gantrez^® AN nanoparticles was investigated. Several strategies were performed in order to study the adjuvant effect of the LPS either encapsulated or coating the nanoparticles. OVA, as well as LPS, was incorporated either during the manufacturing process (OVA-encapsulated or LPS-encapsulated nanoparticles, respectively) or after the preparation (OVA-coated or LPS-coated nanoparticles, respectively). After the administration of 10 μg of OVA incorporated in the different formulations, all the nanoparticles, with or without LPS, were capable of amplifying the immune response (IgG₁ and IgG_2a). However, in a model of sensitized mice to OVA, the formulation with OVA and LPS-entrapped inside the nanoparticles administered intradermally in three doses of 3 μg of OVA each was the only treatment that totally protected the mice from death after a challenge with an intraperitoneal injection of OVA. In contrast, the control group administered with OVA adsorbed onto a commercial alhydrogel adjuvant showed 80% mortality. These results are highly suggestive for the valuable use of Gantrez^® nanoparticles combined with rough LPS of B. ovis in immunotherapy.     

Effects of subtoxic concentrations of TiO(2) and ZnO nanoparticles on human lymphocytes, dendritic cells and exosome production

Metal oxide nanoparticles are widely used in the paint and coating industry as well as in cosmetics, but the knowledge of their possible interactions with the immune system is very limited. Our aims were to investigate if commercially available TiO₂ and ZnO nanoparticles may affect different human immune cells and their production of exosomes, nano-sized vesicles that have a role in cell to cell communication. We found that the TiO₂ or ZnO nanoparticles at concentrations from 1 to 100 μg/mL did not affect the viability of primary human peripheral blood mononuclear cells (PBMC). In contrast, monocyte-derived dendritic cells (MDDC) reacted with a dose dependent increase in cell death and caspase activity to ZnO but not to TiO₂ nanoparticles. Non-toxic exposure, 10 μg/mL, to TiO₂ and ZnO nanoparticles did not significantly alter the phenotype of MDDC. Interestingly, ZnO but not TiO₂ nanoparticles induced a down regulation of FcγRIII (CD16) expression on NK-cells in the PBMC population, suggesting that subtoxic concentrations of ZnO nanoparticles might have an effect on FcγR-mediated immune responses. The phenotype and size of exosomes produced by PBMC or MDDC exposed to the nanoparticles were similar to that of exosomes harvested from control cultures. TiO₂ or ZnO nanoparticles could not be detected within or associated to exosomes as analyzed with TEM. We conclude that TiO₂ and ZnO nanoparticles differently affect immune cells and that evaluations of nanoparticles should be performed even at subtoxic concentrations on different primary human immune cells when investigating potential effects on immune functions.     

Airway irritation,inflammation, and toxicity in mice following inhalation of metal oxide nanoparticles

Metal oxide nanoparticles are used in a broad range of industrial processes and workers may be exposed to aerosols of the particles both during production and handling. Despite the widespread use of these particles, relatively few studies have been performed to investigate the toxicological effects in the airways following inhalation. In the present study, the acute (24?h) and persistent (13 weeks) effects in the airways after a single exposure to metal oxide nanoparticles were studied using a murine inhalation model. Mice were exposed 60?min to aerosols of either ZnO, TiO₂, Al₂O₃ or CeO₂ and the deposited doses in the upper and lower respiratory tracts were calculated. Endpoints were acute airway irritation, pulmonary inflammation based on analyses of bronchoalveolar lavage (BAL) cell composition, DNA damage assessed by the comet assay and pulmonary toxicity assessed by protein level in BAL fluid and histology. All studied particles reduced the tidal volume in a concentration-dependent manner accompanied with an increase in the respiratory rate. In addition, ZnO and TiO₂ induced nasal irritation. BAL cell analyses revealed both neutrophilic and lymphocytic inflammation 24-h post-exposure to all particles except TiO₂. The ranking of potency regarding induction of acute lung inflammation was Al₂O₃ = TiO_2?<_?CeO₂ ? ZnO. Exposure to CeO₂ gave rise to a more persistent inflammation; both neutrophilic and lymphocytic inflammation was seen 13 weeks after exposure. As the only particles, ZnO caused a significant toxic effect in the airways while TiO₂ gave rise to DNA-strand break as shown by the comet assay.     

Zerumbone enhances the Th1 response and ameliorates ovalbumin-induced Th2 responses and airway inflammation in mice

Zerumbone is a sesquiterpene compound isolated from the rhizome of wild ginger, Zingiber zerumbet Smith. The rhizomes of the plant are used as a spice and traditional medicine. Zerumbone was shown to possess anticarcinogenic, anti-inflammatory, and antioxidant properties. However, the antiallergic activity and the underlying mechanism of zerumbone have not been reported. Herein, we investigated the immunomodulatory effects of zerumbone on antigen-presenting dendritic cells (DCs) in vitro and its potential therapeutic effects against ovalbumin (OVA)-induced T helper 2 (Th2)-mediated asthma in mice. In the presence of zerumbone, lipopolysaccharide-activated bone marrow-derived DCs enhanced T cell proliferation and Th1 cell polarization in an allogeneic mixed lymphocyte reaction. In animal experiments, mice were sensitized and challenged with OVA, and were orally treated with different doses of zerumbone after sensitization. Circulating titers of OVA-specific antibodies, airway hyperresponsiveness to methacholine, histological changes in lung tissues, the cell composition and cytokine levels in bronchoalveolar lavage fluid, and cytokine profiles of spleen cells were assessed. Compared to OVA-induced hallmarks of asthma, oral administration of zerumbone induced lower OVA-specific immunoglobulin E (IgE) and higher IgG_2a antibody production, attenuated airway hyperresponsiveness, prevented eosinophilic pulmonary infiltration, and ameliorated mucus hypersecretion. Zerumbone treatment also reduced the production of eotaxin, keratinocyte-derived chemokine (KC), interleukin (IL)-4, IL-5, IL-10, and IL-13, and promoted Th1 cytokine interferon (IFN)-γ production in asthmatic mice. Taken together, these results suggest that zerumbone exhibits an antiallergic effect via modulation of Th1/Th2 cytokines in an asthmatic mouse model.     

Pinocembrin attenuates allergic airway inflammation via inhibition of NF-κB pathway in mice

Pinocembrin, one of the primary flavonoids in propolis, possesses many biological activities, including anti-inflammation, anti-oxidation and immunoregulation. This study aimed to evaluate whether pinocembrin could attenuate ovalbumin (OVA)-induced allergic airway inflammation in mice and to explore the possible mechanism. BALB/c mice sensitized and challenged with OVA were administered intraperitoneally with pinocembrin. Airway inflammation and airway hyperresponsiveness were examined. T-helper type (Th) 2 cytokines in bronchoalveolar lavage fluid (BALF) and OVA-specific immunoglobulin E (IgE) in serum were determined. The activation of nuclear factor kappa B (NF-κB) p65 were also measured. Our results showed that pinocembrin resulted in significant inhibition of pathophysiological signs of allergic asthma, including increased pulmonary eosinophilia infiltration, mucus hypersecretion and airway hyperresponsiveness (AHR). Treatment with pinocembrin significantly reduced Th2 cytokines interleukin (IL)-4, IL-5 and IL-13 in BALF, and OVA-specific IgE in serum. Moreover, pinocembrin treatment suppressed phosphorylation of inhibitor-κBα (IκBα) and NF-κB subunit p65 activation in lung tissue of OVA-sensitized mice. These data suggest that pinocembrin may inhibit allergic airway inflammation, and providing potential benefits in the treatment of inflammatory disease.     

Comparison of pulmonary inflammatory responses following intratracheal instillation and inhalation of nanoparticles

In order to examine whether intratracheal instillation studies can be useful for determining the harmful effect of nanoparticles, we performed inhalation and intratracheal instillation studies using samples of the same nanoparticles. Nickel oxide nanoparticles (NiO) and titanium dioxide nanoparticles (TiO₂) were used as chemicals with high and low toxicities, respectively. In the intratracheal instillation study, rats were exposed to 0.2 or 1?mg of NiO or TiO₂. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the single intratracheal instillation. In the inhalation study, rats were exposed to inhaled NiO or TiO₂ (1.65, 1.84?mg/m³, respectively) for 4 weeks. The same endpoints were examined from 3 days to 3 months after the end of exposure. Inhalation of NiO induced an increase in the number of neutrophils in BALF and concentrations of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2 and heme oxygenase (HO)-1. Intratracheal instillation of NiO induced persistent inflammation and upregulation of these cytokines was observed in the rats. However, inhalation of TiO₂ did not induce pulmonary inflammation, and intratracheal instillation of TiO₂ transiently induced an increase in the number of neutrophils in BALF and the concentrations of CINC-1, CINC-2 and HO-1. Taken together, a difference in pulmonary inflammation was observed between the high and low toxicity nanomaterials in the intratracheal instillation studies, as in the inhalation studies, suggesting that intratracheal instillation studies may be useful for ranking the harmful effects of nanoparticles.     

Toxicity of nanoparticles of ZnO, CuO and TiO2 to yeast Saccharomyces cerevisiae

The aim of this study was to evaluate the toxic effect of nanosized ZnO, CuO and TiO₂ to Saccharomyces cerevisiae – a widely used unicellular eukaryotic model organisms in molecular and cell biology. The effect of metal oxide nanoparticles, their bulk forms and respective ionic forms were compared. The bioavailable Zn²⁺ and Cu²⁺ ions in the growth medium were quantified by recombinant microbial sensors.Nano and bulk TiO₂ were not toxic even at 20000 mg/l. Both, nano and bulk ZnO were of comparable toxicity (8-h EC₅₀ 121–134 mg ZnO/l and 24-h EC₅₀ 131–158 mg/l). The toxicity was explained by soluble Zn-ions as proved by the microbial sensor. However, nano CuO was about 60-fold more toxic than bulk CuO: 8-h EC₅₀ were 20.7 and 1297 mg CuO/l and 24-h EC₅₀ were 13.4 and 873 mg/l, respectively. The increase in toxicity of both CuO formulations at 24th hour of growth was due to the increased dissolution of copper ions from CuO over time. Comparison of EC₅₀ values of nano CuO, bulk CuO and Cu²⁺ with bioavailable copper concentrations in the growth medium showed that the solubilized Cu-ions explained only about 50% of the toxicity of both, nano and bulk CuO. To our knowledge, this is the first study that evaluates the toxicity of ZnO, CuO and TiO₂ nanoparticles to S. cerevisiae.     

Dendritic cells treated with a prostaglandin I2 analog,iloprost, promote antigen-specific regulatory T cell differentiation in mice

Iloprost, a stable prostaglandin I₂ (PGI₂) analog, can inhibit allergic inflammation in an ovalbumin (OVA)-induced asthma model via inhibition of airway dendritic cell (DC) function. However, the underlying mechanism of PGI₂ signaling-mediated immunosuppression remains unclear. This study explored whether iloprost-treated DCs can suppress inflammation by promoting antigen-specific regulatory T cell (Treg) differentiation through PGI₂-G-protein-coupled receptor (IP). We established an allergic lung inflammation model using a hydrogel biomaterial delivery system and observed that iloprost significantly suppressed OVA-induced Th2 lung inflammation and increased the frequency of OVA-specific Tregs in vivo. We further observed that iloprost-treated DCs displayed tolerogenic characteristics, including low inflammatory cytokine (IL-12, TNF-α, IL-6, IL-23) expression levels, high anti-inflammatory cytokine (IL-10) production, and a semimature phenotype. In addition, iloprost-treated DCs increased OVA-specific CD4⁺Foxp3⁺ T cell differentiation from naïve T cells in an IP-dependent pathway in vitro and in vivo. Blocking experiments showed that iloprost-treated DCs promoted Treg differentiation, at least in part, through programmed death ligand 1 (PD-L1), whereas iloprost-induced PD-L1 expression in DCs was through the IP receptor. Furthermore, iloprost treatment suppressed DC-mediated airway inflammation and increased the frequency of OVA-specific Tregs through PD-L1 in vivo. Taken together, these results show that PGI₂-IP signaling mediated by iloprost in DCs may lead to immune tolerance, suggesting that the PGI₂ analog has the potential to be applied therapeutically for tolerogenic DC immunotherapy in autoimmune diseases or allergic asthma.     

Potential impact of metal oxide nanoparticles on the immune system: The role of integrins,L-selectin and the chemokine receptor CXCR4

The impact of metal oxide nanoparticles (NPs) on the immune system has been studied in vitro using human peripheral blood lymphocytes (PBLs). Metal oxide NPs (ZnO, CeO₂, TiO₂ and Al₂O₃) induced changes in the expression levels of adhesion molecules and the C-X-C chemokine receptor type 4 (CXCR4) in these cells. Proliferation studies were carried out with CFSE in response to PHA, finding an increase in T-cell proliferation upon cell exposure to TiO₂ and Al₂O₃ NPs. For ZnO NPs, a decrease in the chemotactic response to SDF-1α was observed. No changes were found in basophil activation and leukocyte oxidative burst after phagocytosis. Despite the absence of cytotoxicity, metal oxide NPs are not inert; they alter the expression levels of adhesion molecules and chemokine receptors, key actors in the immune response, and affect important cell functions such as T-cell proliferative response to mitogens and chemotaxis.From the Clinical EditorThis study demonstrates the immune-modulating effects of four different metal nanoparticles in a human peripheral blood lymphocyte model system. These effects were clearly present even though these nanoparticles did not display cytotocity in ex vivo experiments.     

Comparative effects of TiO2 and ZnO nanoparticles on growth and ultrastructure of ovarian antral follicles

Titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles (NP) have been demonstrated to reach the ovary. However, the potential detrimental effects of these metal-based NP on ovarian antral follicles and whether they can be directly taken up by follicular cells are unknown. The aim of this study was to evaluate whether TiO₂ and ZnO NP internalize into the antral follicle, and further compared any potential detrimental effects of either NP on growth, ultrastructure and viability of antral follicles. It has been described that TiO₂ and ZnO NP induce oxidative stress, thus this study indirectly assessed whether oxidative stress was involved. Antral follicles were cultured with TiO₂ (5, 25 and 50 μg/mL) or ZnO (5, 15 and 25 μg/mL) NP for 96 h. TiO₂ NP were internalized and agglomerated into cells, increased follicle diameter and disrupted the cytoskeleton arrangement, effects that were partially prevented by a co-exposure with trolox. Moreover, ZnO NP partially dissolved into culture media, decreased follicle diameter, and disrupted cytoskeletal arrangement, and these effects were not prevented by trolox. Ultrastructural alterations induced by exposure to both NP were evidenced by impaired transzonal projections and swelling mitochondria. Oxidative stress mediates TiO₂ NP-induced effects but not those from ZnO NP in antral follicle development. Our results suggest that both NP induced ovarian follicle toxicity through different toxic mechanisms, possibly due to a stimulation of ZnO NP solubility and agglomeration of TiO₂ NP into the follicular cells.     

Evaluation of cytogenotoxicity and oxidative stress parameters in male Swiss mice co-exposed to titanium dioxide and zinc oxide nanoparticles

A number of studies have investigated the adverse toxic effects of titanium dioxide (TiO₂) nanoparticles (NPs) or zinc oxide (ZnO) NPs. Information on the potential genotoxic effects of the interactions of TiO₂ NPs and ZnO NPs in vivo is lacking. Therefore, this study was designed to investigate the cytogenotoxicity of TiO₂ NPs or ZnO NPs alone or their mixtures using the bone marrow micronucleus assay, and mechanism of damage through the evaluation of oxidative stress parameters in the liver and kidney tissues of Swiss mice. Intraperitoneal administration of doses between 9.38 and 150.00 mg/kg of TiO₂ NPs or ZnO NPs or TiO₂ NPs + ZnO NPs was performed for 5 and 10 days, respectively. TiO₂ NPs alone induced a significant (P < 0.05) increase in micronucleated (Mn) polychromatic erythrocytes (PCEs) at the applied doses compared with the negative controls, with a significant difference between 5 and 10 days for TiO₂ NPs alone and TiO₂ NPs + ZnO NPs. Concurrently, TiO₂ NPs alone for 5 days and TiO₂ NPs and TiO₂ NPs + ZnO NPs for 10 days significantly (P < 0.05) decreased the percentage PCE: normochromatic erythrocyte (NCE) indicating cytotoxicity; with a significant difference between the two periods. Significant (P < 0.001) changes in the activities of superoxide dismutase (SOD) and catalase (CAT), and levels of reduced glutathione (GSH) and malondialdehyde (MDA) were observed in the liver and kidney of mice exposed to TiO₂ NPs or ZnO NPs alone or their mixtures. These results suggest that TiO₂ NPs alone was genotoxic; TiO₂ NPs and TiO₂ NPs + ZnO NPs were noticeably cytotoxic while ZnO NPs was not cytogenotoxic. The individual NPs or their mixtures induced oxidative stress.