Titanium dioxide nanoparticles oral exposure to pregnant rats and its distribution.

BACKGROUND: Titanium dioxide (TiO2) nanoparticles are among the most manufactured nanomaterials in the industry, and are used in food products, toothpastes, cosmetics and paints. Pregnant women as well as their conceptuses may be exposed to TiO2 nanoparticles; however, the potential effects of these nanoparticles during pregnancy are controversial, and their internal distribution has not been investigated. Therefore, in this study, we investigated the potential effects of oral exposure to TiO2 nanoparticles and their distribution during pregnancy. TiO2 nanoparticles were orally administered to pregnant Sprague-Dawley rats (12 females per group) from gestation days (GDs) 6 to 19 at dosage levels of 0, 100, 300 and 1000 mg/kg/day, and then cesarean sections were conducted on GD 20. RESULTS: In the maternal and embryo-fetal examinations, there were no marked toxicities in terms of general clinical signs, body weight, food consumption, organ weights, macroscopic findings, cesarean section parameters and fetal morphological examinations. In the distribution analysis, titanium contents were increased in the maternal liver, maternal brain and placenta after exposure to high doses of TiO2 nanoparticles. CONCLUSION: Oral exposure to TiO2 during pregnancy increased the titanium concentrations in the maternal liver, maternal brain and placenta, but these levels did not induce marked toxicities in maternal animals or affect embryo-fetal development. These results could be used to evaluate the human risk assessment of TiO2 nanoparticle oral exposure during pregnancy, and additional comprehensive toxicity studies are deemed necessary considering the possibility of complex exposure scenarios and the various sizes of TiO2 nanoparticles.

Toxicity of zinc oxide nanoparticles in rats treated by two different routes: single intravenous injection and single oral administration.

Toxicokinetics of zinc oxide nanoparticles (ZnONP) was studied in rats via a single intravenous (iv) injection and a single oral administration (3 mg/kg or 30 mg/kg), respectively. Blood concentrations of zinc (Zn) were monitored for 7 d and tissue distribution were determined in liver, kidneys, lung, spleen, thymus, brain, and testes. To ascertain the excretion of ZnONP, Zn levels in urine and feces were measured for 7 d. ZnONP were not readily absorbed from the gastrointestinal tract (GIT) after oral administration and were excreted mostly in feces. When the nanoparticles were injected iv to rats at a dose of 30 mg/kg, peak concentration appeared at 5 min but returned to normal range by d 2 (48 h after injection). ZnONP were distributed mainly to liver, kidneys, lung, and spleen, but not to thymus, brain, and testes. The distribution level was significantly decreased to normal by d 7. Feces excretion levels after iv injection supported biliary excretion of ZnONP. In rats injected iv with 30 mg/kg, mitotic figures in hepatocytes were significantly increased and multifocal acute injuries with dark brown pigment were noted in lungs, while no significant damage was observed in rats treated orally with the same dosage.

Integrated Assessment for the Estrogenic Effects of Pyrethroid Compounds: Defining the Molecular Initiating Events and Key Events for the Adverse Outcome Pathway.

Pyrethroids, which are derived from natural insecticides found in chrysanthemum flowers, are widely utilized in various sectors, including agriculture, forestry, horticulture, and personal insect protection. Due to their widespread use, concerns have arisen regarding their potential estrogenic effects on female reproductive health. This review aims to address data gaps and inconsistencies in previous studies by defining molecular initiating events and key events within the adverse outcome pathway associated with pyrethroid-induced estrogenic effects. To achieve this, we propose utilizing Integrated Approaches to Testing and Assessment (IATA), which incorporate in vitro assays and in vivo assessments to comprehensively investigate the estrogenic effects of pyrethroids. An initial search was conducted in the PubMed database to identify relevant articles. Subsequently, the findings were classified according to the IATA strategy. This review provides an overview of the current understanding of pyrethroids and their estrogenic effects, identifies data gaps, and highlights the use of IATA in existing studies on the estrogenic effects of various pyrethroids. It emphasizes the urgent need for comprehensive research on the estrogenic effects of pyrethroids and highlights the importance of standardized testing methods like IATA to accurately assess their impact on human and environmental health. By promoting the use of Integrated Testing Strategies (ITSs) and addressing data gaps, researchers and regulators can enhance the accuracy of assessments, ensuring better protection of human and environmental health from the potential estrogenic effects of pyrethroid exposure.

Toxicokinetic differences and toxicities of silver nanoparticles and silver ions in rats after single oral administration.

Blood levels, tissue distributions, and excretion of silver (Ag) were measured in male Sprague-Dawley rats (n = 5) up to 24 h after a single oral administration of silver nanoparticles (AgNP) and silver ions (Ag(+)), respectively. The AUC24hr of Ag(+) was 3.81 ± 0.57 µg/d/ml when rats were treated with a single dose of 20 mg/kg, whereas that of AgNP was 1.58 ± 0.25 µg/d/ml. Tissue distribution of Ag in liver, kidneys, and lungs was higher when Ag(+) was administered compared to AgNP. Orally administered AgNP were predominantly excreted through feces, suggesting low bioavailability. Death or body weight changes were not observed in the Ag(+)- or AgNP-treated groups. However, decreased red blood cell counts, hematocrit, and hemoglobin were found in the Ag(+)-treated groups, while increased platelet counts and mean platelet volume were noted in the AgNP-treated rats. A serum biochemical analysis showed that aspartate aminotransferase (AST) and alanine aminotransferase (ALT) rose significantly following Ag(+) treatment (20 mg/kg). AgNP treatment (2 or 20 mg/kg) also elevated AST, whereas infiltration of mononuclear cells with liver necrosis was found only in the 20 mg/kg Ag(+)-treated animals.

The stability of citrate-capped silver nanoparticles in isotonic glucose solution for intravenous injection.

Citrate-capped silver nanoparticles (AgNP) are widely used in industry, consumer products, and medical appliances. However, information on the environmental toxicity and human health is not comprehensive. Further, the physicochemical properties of AgNP make it difficult to test toxicity, as nanosized particles, due to their size, may increase by aggregation or agglomeration in some administration vehicles. In this study, stability of AgNP was investigated in different types of isotonic solutions, which is important for in vitro testing or toxicokinetic studies using intravenous (iv) injection. Size, morphology, zeta potential, and ion formation were investigated in isotonic solutions for the physicochemical characterization of AgNP. Aggregation and precipitation of AgNP were observed in phosphate-buffered saline or 0.9% NaCl, while AgNP were stable without aggregation or precipitation in 5% glucose in isotonic solution. The average size of AgNP in 5% glucose was approximately 10 nm at different temperatures of 10, 25, or 36°C and at varying concentrations from 10 to 1000 ppm. It is noteworthy that this is almost the same size distribution as that in the water-based suspension of AgNP supplied by the manufacturer. Zeta potential ranged from -40 to -60 mV, suggesting that the repulsion forces of AgNP are not disturbed to a sufficient degree to aggregate while osmolarity is in the isotonic range of 290 ± 10 mOsm/kg in 5% glucose solution. Data suggest that AgNP in a 5% glucose solution may be used in the toxicity test via iv injection without adverse consequences in blood.

Mixture Effects of Bisphenol A and Its Structural Analogs on Estrogen Receptor Transcriptional Activation.

Bisphenol A (BPA) exposure has been widely linked to endocrine-disrupting effects. Recently, many substitutes for BPA have been developed as safe structural analogs. However, they have still been reported to have similar adverse effects. The current study evaluated the effects of bisphenol A and eight structural analogs on the transcription of estrogen receptor alpha (ERα). The effects of binary and ternary mixtures prepared from different combinations of BPA analogs were also evaluated for transcription activity. The measured data of the mixtures were compared to the predicted data obtained by the full logistic model, and the model deviation ratio (MDR) was calculated to determine whether the effects were synergistic, antagonistic, or additive. Overall, the results suggest that the effect of bisphenol compound are additive in binary and ternary mixtures.

The mixture effect of propyl paraben and bisphenol A on the uterotrophic response in the ovariectomized rats after oral administration.

Recent studies reported bisphenol A (BPA) and propyl paraben (PrP) are found in human urine, blood, and breast milk samples as well as in food, packaging, socks, and clothes. This means that the two chemicals co-exist in consumer products, and humans are exposed simultaneously to the mixture chemicals. However, the studies on the mixture effects of the two chemicals on human health are not enough. This study was designed to elucidate the effects of orally administered PrP, BPA, and their mixture effects on the uterotrophic response using ovariectomized rats. In addition, the correlation between the uterotrophic response and tissue concentrations of the two chemicals was studied to investigate whether one chemical has any effect on the absorption, distribution, or excretion of the other chemical. Histopathology, hematology, and plasma biochemistry analysis were also performed to evaluate the chemicals' toxicological effects in the treated rats. Although a significant increase in uterus weight (absolute and relative) was observed in the positive chemical (17ß-estradiol) treated group, there were no statistical differences in the uterus weight between the vehicle control and the chemical-treated groups. However, a slight increase in the endometrial glands and a change in the cuboidal to columnar epithelium of the endometrial epithelium were observed in the mixture-treated group. There was no significant toxicity in all treated groups by the hematology and plasma biochemistry analysis results. The results of tissue distribution showed that BPA was mostly detected in the liver while PrP was not detected in most tissues, and the BPA level was higher when the rats were treated with PrP than without PrP, suggesting that PrP may increase the absorption of BPA after oral administration.

Potency classification of isothiazolinone compounds based on defined approaches of skin sensitization in OECD GL 497.

Regulatory decisions for skin sensitization are now based on adverse outcome pathway (AOP) and integrated approaches to testing and assessment (IATA). Based on these, Organisation for Economic Co-operation and Development (OECD) guidelines on defined approaches for skin sensitization were adopted with a fixed data interpretation procedure (DIP). In the guidelines, "Defined Approaches" (DA) on skin sensitization uses the results from multiple information sources of in chemico, in vitro, and in silico data to achieve an equivalent predictive capacity as those of the animal tests. In this review, we evaluated the skin sensitization of eleven isothiazolinone compounds including 4,5-Dichloro-2-octyl-3(2H)-isothiazolone (DCOIT), 2-n-Octyl-4-isothiazolin-3-one (OIT), 2-Methyl-4-isothiazolin-3-one (MIT), 1,2-Benzisothiazolin-3-one (BIT), 1,2-Benzisothiazolin-3-one, 2-butyl (BBIT), 5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4,5-trimethylene-4-isothiazolin-3-one (MTMIT), 2-methyl-1,2-benzothiazol-3-one (MBIT), 2-methyl-1,2-benzothiazole-3-thione (MBIT-S), 1,2-benzisothiazolin-3-one, 2-methyl-, 1,1-dioxide (BBIT-O), and a mixture of CMIT/MIT. Data from direct peptide reactivity assay (DPRA), human cell line activation (h-CLAT) test, and quantitative structure activity relationship (QSAR) Toolbox were evaluated and were applied to the DIP to derive a prediction of hazard identification and a potency classification. Among the evaluated chemicals, six isothiazolinone compounds were classified to be UN GHS 1A, one compound to be UN GHS 1, and four compounds could not be classified due to lack of data. The results of sensitizer chemicals were found to coincide well with those of in vivo test.

The impact of intratracheally instilled carbon black on the cardiovascular system of rats: elevation of blood homocysteine and hyperactivity of platelets.

Carbon black (CB) is an industrial chemical with high potential for human exposure. Although the relationship between exposure to particulate matter (PM) and cardiovascular disease is well documented, the risk of adverse cardiovascular effects attributed to CB particles has not been clearly characterized. This study was performed to (1) investigate the effects of CB on cardiovascular system and (2) identify the target tissue or potential biomarkers. Carbon black with a distinct particle size, N330 (ultrafine particle) and N990 (fine particle), was intratracheally instilled into rats at a doses of 1, 3, or 10 mg/kg. Measurements of thrombotic activity and determination of plasma homocysteine levels, cardiac functionality, and inflammatory responses were conducted at 24-h and 1-wk time points. Exposure to N330 accelerated platelet-dependent blood clotting at 10 mg/kg, the highest exposure tested. Unexpectedly, both N330 and N990 led to prolongation of activated partial thromboplastin time (aPTT), whereas these CB particles failed to affect prothrombin time (PT). N990 produced a significant elevation in the level of plasma homocysteine, a well-established etiological factor in cardiovascular diseases. Both N330 and N990 induced apparent inflammation in the lungs; however, both particles failed to initiate systemic inflammation. Neither CB particle produced observable cardiac symptoms as detected by electrocardiography. Taken together, data show CB exposure enhanced the cardiovascular risk by inducing hyperhomocysteinemia and platelet hyperactivity, although these effects may be variable depending on particle size and exposure duration. Homocysteine may be a potential biomarker for cardiovascular toxicity following CB exposure.

Effects of consumer products chemicals ingredients and their mixtures on the estrogen receptor/androgen receptor transcriptional activation.

Unlike the environmental pollutants or industrial chemicals, the chemicals in consumer products may pose higher levels of risks, depending on how the chemicals are used in the products and how humans interact with the products. Recently, endocrine disrupting chemicals in cosmetics, personal care products, cleaners, sunscreens, and vinyl products were analytically quantified and many active chemicals including phthalates, parabens and bisphenols were detected. This indicates a wide range of exposures from common products. In this study, 35 chemicals known to be ingredients of consumer products were selected and screened for the transactivation of estrogen receptors and androgen receptors. From the results of individual chemicals, the activity of binary/ternary mixture prepared from the agonists for the ER transcription activity was measured, and compared to the predicted values obtained by the full logistic model. The measured and the predicted values were found to be very similar. This study may suggest that prediction of mixture activity by proper models would be one of the supportive tools for the risk assessment and sound regulation of chemical mixtures which have potential endocrine disrupting effects in consumer products.

Assessment of agonistic and antagonistic properties of humidifier disinfectants to the estrogenic and androgenic receptors by transactivation assay.

Before being recalled and banned from the Korean market, humidifier disinfectants (HDs) were added to the humidifier water tank to prevent microbial growth. The known HDs active ingredients included the are oligo(2-(2-ethoxy)ethoxyethyl guanidine (PGH), polyhexamethylene guanidine (PHMG), a mixture of methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT), didecyldimethyl ammonium chloride (DDAC), Sodium dichloroisocyanurate (NaDCC), and alkyldimethylbenzyl ammonium chloride (BAC). Previous epidemiological studies have suggested that PHMG induces fatal lung disease in pregnant, post-partum women, and young children. In an animal study, a mixture of DDAC and BAC exhibited decreased fertility and fecundity; increased time to first litter, longer pregnancy intervals, fewer pups per litter, and fewer pregnancies. In this study, endocrine-disrupting effects of HDs were investigated using estrogen receptor (ER) and androgen receptor (AR) transactivation assay based on OECD Test guidelines. Unexpectedly, unlike the previously reported reproductive toxicity data, in the present study, HDs did not show ER and AR transcriptional activation agonist and/or antagonist effects. However, it is difficult to conclude that HDs has no endocrine disruption effects, and further research on the effects of HDs mixtures, and in vivo tests including Uterotrophic bioassay and Hershberger bioassay would be necessary.

PM 2.5 collected in a residential area induced Th1-type inflammatory responses with oxidative stress in mice.

Epidemiologists have tried to establish an association between human health and exposure to particulate matter (PM). In addition, many researchers have investigated the adverse effects of PM as a trigger of cardiovascular and pulmonary diseases. It is known that a number of environmental contaminants are attached to PM and the toxicity of PM may depend on the sources. We investigated the effects of PM collected in a residential area of Seoul on the immunotoxic responses including cytokine production in BAL fluid and in blood after a single intratracheal instillation in mice with the characterization of physico-chemical properties of PM 2.5 samples. As results, pro-inflammatory cytokines (IL-1, TNF-α, and IL-6), Th0-type cytokine (IL-2), and Th1-type cytokines (IL-12 and IFN-γ) were increased by a dose-dependent manner. Cell infiltration in the alveolar area and phagocytosis by macrophage was observed until day 28 after instillation. The expressions of oxidative stress-related genes (HSP 1a, HSP 8, and SOD) and tissue damage-related genes (MMP-15, -19, and Slpi) were time-dependently increased. PM 2.5 also induced an increase of T cell distribution in lymphocyte and decreased the CD4+/CD8+ ratio. Based on the results, we suggest that PM 2.5 collected in a residential area of Seoul may induce Th1 type-inflammatory responses with oxidative stress and trigger adverse effects in human health.

Fibrosis as a result of polyhexamethylene guanide exposure in cultured Statens Seruminstitut Rabbit Cornea (SIRC) cells.

Previous research studies on the toxicity of polyhexamethylene guanidine (PHMG) as a humidifier disinfectant majorly focused on lung fibrosis. Considering that disinfectants in humidifiers are released in aerosol form, the eyes are directly exposed and highly vulnerable to the detrimental effects of the PHMG. Therefore, in the present study we investigated the adverse effects of PHMG on the eyes; considering fibrosis as a manifestation of PHMG toxicity in the eye, we evaluated fibrosis-related biomarkers in cultured Statens Seruminstitut Rabbit Cornea (SIRC) cells. Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, fibrosis-related biomarkers were evaluated through polymerase chain reaction (PCR) and immunoblotting, and oxidative stress was evaluated using 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA). Polyhexamethylene guanidine showed cytotoxicity in a time and concentration-dependent manner. Fibrosis related biomarkers including transforming growth factor-ß (TGF-ß), α-smooth muscle actin (α-SMA), matrix metalloproteinase (MMP), tissue inhibitor of metalloproteinase (TIMP) and hemeoxygenase-1 (HO-1) increased in both gene and protein levels. Oxidative stress also increased in the PHMG-treated cultured cells. The findings of the present study suggest that PHMG could cause toxicity in the eye as manifested by fibrosis.

Gastrointestinal tract and skin permeability of chemicals in consumer products using parallel artificial membrane permeability assay (PAMPA).

Some chemicals commonly used in personal care products, household items, food vessels, cosmetics, and other consumer products are potentially harmful, and several reviews of epidemiological studies have suggested the associations between the chemical exposure from consumer products, and respiratory diseases, skin sensitization, and reproductive problems. Therefore, risk assessment is essential for management of consumer products safety. Necessarily, the estimation of human exposure is an essential step in risk assessment, and the absorption rate of those chemicals via the gastrointestinal tract, respiratory tract, and skin are very critical in determining the internal dose of the exposed chemicals. In this study, parallel artificial membrane permeability assays (PAMPA) for the gastrointestinal tract and skin were performed to evaluate the permeability of parabens (4-hydroxybenzoic acid, methyl-, propyl-, and butyl paraben), bisphenols (bisphenol A, bisphenol F, and bisphenol S), isothiazolinones (methyl-, chloromethyl-, benz-, octyl-, and dichlorooctyl isothiazolinone), and phthalates [diethyl-, dibutyl-, Di-isononyl-, and bis(2-ethylhexyl) phthalate]. Lipid solubility of test chemicals indicated by log P values was shown as the most critical factor and showed a positive association with the permeability of parabens, bisphenols, and isothiazolinones in PAMPA assay. However, phthalate showed a reverse-association between lipophilicity and permeability. The permeability of all the tested chemicals was higher in the gastrointestinal tract membrane than in the skin membrane. The pH in donor solution did not show significant effects on the permeability in all the chemicals, except the chemicals with a free hydrophilic moiety in their chemical structures.

Carbon fullerenes (C60s) can induce inflammatory responses in the lung of mice.

Fullerenes (C60s) occur in the environment due to natural and anthropogenic sources such as volcanic eruptions, forest fires, and the combustion of carbon-based materials. Recently, production and application of engineered C60s have also rapidly increased in diverse industrial fields and biomedicine due to C60' unique physico-chemical properties, so toxicity assessment on environmental and human health is being evaluated as a valuable work. However, data related to the toxicity of C60s have not been abundant up to now. In this study, we studied the immunotoxic mechanism and change of gene expression caused by the instillation of C60s. As a result, C60s induced an increase in sub G1 and G1 arrest in BAL cells, an increase in pro-inflammatory cytokines such as IL-1, TNF-alpha, and IL-6, and an increase of Th1 cytokines such as IL-12 and IFN-r in BAL fluid. In addition, IgE reached the maximum at 1 day after treatment in both BAL fluid and the blood, and decreased in a time-dependent manner. Gene expression of the MHC class II (H2-Eb1) molecule was stronger than that of the MHC class I (H2-T23), and an increase in T cell distribution was also observed during the experiment period. Furthermore, cell infiltration and expression of tissue damage related genes in lung tissue were constantly observed during the experiment period. Based on this, C60s may induce inflammatory responses in the lung of mice.

Safety assessment of cerium oxide nanoparticles: combined repeated-dose toxicity with reproductive/developmental toxicity screening and biodistribution in rats.

Cerium oxide nanoparticles (CeO2 NPs) are widely used in various commercial applications because of their characteristic properties. People can be easily exposed to CeO2 NPs in real life, but the safety assessment of CeO2 NPs has not been fully investigated. Therefore, in this study, we conducted a combined repeated-dose and reproductive/developmental toxicity screening study (OECD testing guideline 422) to investigate the potential hazards on human health, including reproductive/developmental functions, after repeated daily CeO2 NPs oral gavage administration to both males and females. In addition, tissues from parental animals and their pups were collected to analyze the internal accumulation of cerium. CeO2 NPs were orally administered to Sprague-Dawley rats at doses of 0, 100, 300 and 1000 mg/kg during their pre-mating, mating, gestation and early lactation periods. In the general systemic and reproductive/developmental examinations, no marked toxicities were observed in any in-life and terminal observation parameters in this study. In the biodistribution analysis, cerium was not detected in either parental or pup tissues (blood, liver, lungs and kidneys). Repeated oral exposure of CeO2 NPs did not induce marked toxicities affecting general systemic and reproductive/developmental functions up to the dose level of 1000 mg/kg and the CeO2 NPs were not systemically absorbed in parental animals or their pups. This result could be used in risk assessment for humans, and additional toxicity studies with CeO2 NPs will be necessary considering various physicochemical properties and exposure probabilities of these nanoparticles.

Pro-inflammatory and potential allergic responses resulting from B cell activation in mice treated with multi-walled carbon nanotubes by intratracheal instillation.

The increased application of engineered carbon nanotubes (CNTs) has also raised the level of public concern regarding possible toxicities caused by exposure to these nanostructures. In this study, pulmonary and systemic immune responses induced by intratracheal instillation of multi-walled carbon nanotubes (MWCNTs) were investigated in mice. Total numbers of immune cells in bronchoalveolar lavage (BAL) fluid were significantly increased in treated groups (5, 20, and 50mg/kg doses of MWCNTs) and the distribution of neutrophils was elevated at day 1 after instillation. Pro-inflammatory cytokines (IL-1, TNF-alpha, IL-6, IL-4, IL-5, IL-10, IL-12, and IFN-gamma) were also increased in a dose-dependent manner, both in BAL fluid and in blood. Most of the cytokines showed the highest levels at day 1 after instillation and then decreased. Th2-type cytokines (IL-4, IL-5, and IL-10) were elevated in the treated group to levels higher than those of the Th1-type cytokines (IL-12 and IFN-gamma). Furthermore, distributions of B cells in spleen and blood were significantly increased at day 1 after instillation, indicating that Th2-type cytokines had activated B cells, causing them to proliferate. Along with the additional numbers of B cells, granuloma formation in the lung tissue and IgE production were also observed, with an intensity dependent on the dose of MWCNTs instilled. Based on these observations, it is suggested that MWCNTs may induce allergic responses in mice through B cell activation and production of IgE.

Oxidative stress and pro-inflammatory responses induced by silica nanoparticles in vivo and in vitro.

Oxidative stress and inflammatory responses induced by silica nanoparticles were evaluated both in mice and in RAW264.7 cell line. Single treatment of silica nanoparticles (50mg/kg, i.p.) led to the activation of peritoneal macrophages, the increased blood level of IL-1beta and TNF-alpha, and the increased level of nitric oxide released from the peritoneal macrophages. mRNA expressions of inflammation-related genes such as IL-1, IL-6, TNF-alpha, iNOS, and COX-2 were also elevated in the cultured peritoneal macrophages harvested from the treated mice. When the viability of splenocytes from the mice treated with silica nanoparticles (50mg/kg, 100mg/kg, and 250mg/kg, i.p.) was measured, the viability of splenocytes was significantly decreased in the higher dose-treated groups (100mg/kg, 200mg/kg i.p.). However, cell proliferation without cytotoxicity was shown in group treated with relatively low dose of 50mg/kg i.p. When leukocyte subtypes of mouse spleen were evaluated using flow cytometry analysis, it was found that the distributions of NK cells and T cells were increased to 184.8% and 115.1% of control, respectively, while that of B cells was decreased to 87.7%. To elucidate the pro-inflammatory mechanism of silica nanoparticles in vivo, in vitro study using RAW 264.7 cell line which is derived from mouse peritoneal macrophage was done. Treatment of silica nanoparticles to the cultured RAW264.7 cells led to the reactive oxygen species (ROS) generation with a decreased intracellular GSH. In accordance with ROS generation, silica nanoparticles increased the level of nitric oxide released from the cultured macrophage cell line. These results suggested that silica nanoparticles generate ROS and the generated ROS may trigger the pro-inflammatory responses both in vivo and in vitro.

Induction of pro-inflammatory signals by 1-nitropyrene in cultured BEAS-2B cells.

Nitropyrene (1-NP) is classified as Group 2B carcinogen and is one of the main components of diesel exhaust particles (DEP), which are generated from incomplete combustion of automobile engines to cause human cancer or inflammatory diseases. Although many reports on the mutagenesis or carcinogenesis of 1-NP have been released, non-carcinogenic toxicities of 1-NP have not been widely studied. In this study, induction of pro-inflammatory signals by 1-NP was investigated using cultured human bronchial epithelial cells, BEAS-2B. By using microarray analysis and RT-PCR technique, it was found that 1-NP induced the expression of genes related to the pro-inflammatory responses such as pentaxin, IL-1beta, IL-6, IL-8, C-X-C motif ligand 2 (CXCL2), and TNF-alpha. 1-NP was also found to induce ROS generation and intracellular GSH decrease. It suggested that 1-NP may be a pivotal component of DEP to cause inflammatory diseases.

Acute toxicity of benzalkonium chloride in Balb/c mice following intratracheal instillation and oral administration.

Benzalkonium chloride is a cationic surfactant widely used as a disinfectant, preservative, and sanitizer in many public places as well as domestically. The purpose of this study is to compare the acute toxicity of lethal doses (LDx) and the target organs after intratracheal instillation and oral ingestion by mice, which is a preliminary test prior to the repeated dose toxicity test. When Balb/c mice were treated with a single dose of benzalkonium chloride via oral administration, LD50 was 241.7 mg/kg. However, it was comparatively decreased to 8.5 mg/kg following intratracheal treatment, which suggests that lung may be the main target of toxicity. Although the histopathology showed inflammatory responses in the lung after intratracheal instillation, it still did not confirm that the inflammatory responses were the key factors inducing death in the treated animal. Acute and fatal mechanisms such as bronchoconstriction or neurotoxicity associated with benzalkonium chloride exposure should be further investigated.