Takahiro Kobayashi

University of Tsukuba, Tsukuba, Ibaraki, Japan

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Publications (36)118.97 Total impact

  • Dulee Tamirei Munidasa, Eiko Koike, Takahiro Kobayashi
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    ABSTRACT: Previous studies have shown that inhaled particles exacerbate asthma and allergic rhinitis. Several factors related to the particle may play a role in immune-stimulating activity; however, the underlying mechanisms remain unclear. We carried out in vitro studies to investigate the effects of TiO(2) particle exposure on antigen presenting activity and expression of the associated cell-surface molecules (Ia, B7.1, B7.2) in rat derived monocytes and alveolar macrophages, in terms of two aspects of the particles: (1) size (59 nm (ST) and 350 nm (LT) particles), and (2) the timing of particle exposure (before antigen exposure or co-administered). Results indicated that particle exposure prior to antigen exposure led to decreased antigen presenting activity in both types of cell. This decrease was greater with ST particles. In monocytes, the expression of cell surface molecules decreased similarly with both particles. Conversely, alveolar macrophages showed greater expression of Ia with ST than with LT exposures. Ia expression was confirmed to be functionally active by a mixed lymphocyte reaction. It is possible that particle exposure might result in poor antigen processing, thereby leading to decreased antigen presenting activity. Co-exposure of particles and antigen induced an increase in antigen presenting activity with both types of particle; however, ST exposure induced greater antigen presenting activity. The expression of Ia also increased similarly with both particle sizes. This suggests that, in a co-exposure situation, antigen may be processed without intensive retardation by particles, and factors other than Ia may affect antigen presenting activity. In conclusion, both size and timing of exposure to TiO(2) particles affect antigen presenting activity of monocytes and alveolar macrophages.
    Inhalation Toxicology 09/2009; 21(10):849-56. · 1.89 Impact Factor
  • Seiichi Omura, Eiko Koike, Takahiro Kobayashi
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    ABSTRACT: Diesel exhaust particles (DEP) affect health adversely. Our previous studies revealed that DEP extracts up-regulated expression of genes related to drug metabolism, antioxidant enzymes, cell cycle/apoptosis and coagulation, and in addition, n-hexane soluble fraction (n-HSF) of DEP extracts contains aliphatic and polycyclic aromatic hydrocarbons, and n-hexane insoluble fraction (n-HISF) contains oxygenated compounds and has strong oxidative property. However, the relationship between the properties of chemicals in DEP extracts and the gene expression has not been fully elucidated. Here, we used a microarray analysis to identify and characterize genes whose expression is regulated by exposure to fractions of DEP extracts. A dichloromethane-soluble fraction (DMSF) of DEP was further fractionated into n-HSF and n-HISF. We exposed rat alveolar epithelial (SV40T2) cells to these fractions (30microg/ml) for 6h and identified regulated genes. DMSF predominantly up-regulated genes associated with drug metabolism (Cyp1a1, Gsta3), oxidative stress response (HO-1, Srxn1) and cell cycle/apoptosis (Okl38). Genes up-regulated by n-HSF were mainly associated with drug metabolism (Cyp1a1, Gsta3). The genes up-regulated by n-HISF included antioxidant enzymes (HO-1, Srxn1); genes response to cell damage, such as those functioning in cell cycle regulation or apoptosis (Okl38); and genes in coagulation pathways. Our present results suggested that n-HSF and n-HISF regulated characteristic genes which respond to chemical properties of each fraction.
    Toxicology 06/2009; 262(1):65-72. · 3.75 Impact Factor
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    ABSTRACT: Diesel exhaust nanoparticles easily coagulate during transportation from the engine to the inhalation chamber, depending on concentrations and residence times. Although dilution is effective in suppressing coagulation growth of nanoparticles, volatile organic carbon (OC) evaporates as a result of dilution. Thus, the design of an inhalation facility to investigate the health effects of nanoparticle-rich exhaust is important. In this study, we determined the optimum dilution conditions in consideration of coagulation growth and evaporation of OC for inhalation studies of nanoparticle-rich diesel exhaust. We found that a short residence time prevented coagulation growth in the primary dilution tunnel after the primary dilution or before the diluted exhaust reached the inhalation chamber after the secondary dilution. However, due to the longer residence time in the inhalation chamber, the coagulation growth occurred in the inhalation chamber depending on secondary dilution ratio which controlled exposure dose (particle concentration in the inhalation chamber). We determined that the secondary dilution ratio for the high-concentration chamber should be around 4.5 times to prevent coagulation growth and to obtain the desired exposure dose. We also found that the loss of OC was relatively independent of the secondary dilution ratio when the secondary dilution ratio was more than 10 times because it seemed to reach a gas-particle equilibrium in the inhalation chamber. We therefore set the secondary dilution ratios for the middle- and low-concentration chambers to 13.5 and 40.5 times, respectively.
    Inhalation Toxicology 12/2008; 21(3):200-9. · 1.89 Impact Factor
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    ABSTRACT: Translocation of inhaled ultrafine particles from the lungs into the blood may impair cardiovascular function. We administered ultrafine (20-nm) and fine (200-nm) gold colloid or fluorescein-labeled polystyrene particles to mice intratracheally and examined their localization in the lung and extrapulmonary organs. Fifteen minutes after instillation, dispersed and agglomerated 20-nm gold colloid particles were observed on the surface of endothelial cells, on the alveolar surface, in endocytotic vesicles of alveolar epithelial cells, and in the basement membrane of the lung. A small but noteworthy amount of gold was detected in the liver, kidney, spleen, and heart by inductively coupled plasma-mass spectrometry. After administration of 20- or 200-nm fluorescent particles, free particles were detected infrequently in blood vessels, on the endocardial surface, and in the kidney and liver only in the mice that received 20-nm particles, whereas phagocytes containing 20- or 200-nm particles were found in the extrapulmonary tissues. Fluorescent particle-laden alveolar macrophages administered intratracheally translocated from alveoli to extrapulmonary organs via the blood circulation. Thus, small amounts of ultrafine particles are transported across the alveolar wall into the blood circulation via endocytotic pathways, but particle-laden alveolar macrophages translocate both ultrafine and fine particles from the lungs to the extrapulmonary organs.
    Archives of Toxicology 11/2008; 83(5):429-37. · 5.08 Impact Factor
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    ABSTRACT: Particulate matter including carbon black (CB) nanoparticles can enhance antigen-related inflammation and immunoglobulin production in vivo. Dendritic cells (DC) as antigen-presenting cells (APC) are the most capable inducers of immune responses. The present study was designed to determine whether CB nanoparticles affect the maturation/activation and function of DC in vitro. DC were differentiated from bone marrow (BM) cells of BALB/c mice by culture with granulocyte macrophage colony stimulating factor (GM-CSF). At day 8 of culture, BM-derived DC (BMDC) were exposed to CB nanoparticles with a diameter of 14nm or 56nm for 24h. The expression of major histocompatibility complex (MHC) class II, DEC205, CD80, and CD86 (maturation/activation markers of BMDC) was measured by flow cytometry. BMDC function was evaluated by an allogeneic mixed lymphocyte reaction (MLR) assay. CB nanoparticles significantly increased the expression of DEC205 and CD86 in BMDC and tended to increase MHC class II and CD80 expression; however, a size-dependent effect was not observed. On the other hand, BMDC-mediated MLR was significantly enhanced by the CB nanoparticles and the enhancement was greater by 14nm CB nanoparticles than by 56nm CB nanoparticles. Taken together, CB nanoparticles can promote the maturation/activation and function of BMDC, which could be related to their effects on allergic diseases and/or responses. In addition, BMDC-mediated MLR might be useful assay for in vitro screening for adjuvant activity of environmental toxicants.
    Chemosphere 08/2008; 73(3):371-6. · 3.50 Impact Factor
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    ABSTRACT: Assessment of human exposure is important for the elucidation of potential health risks. However, there is little information available on particle number concentrations and number size distributions, including those of nanoparticles, in the working environments of factories producing engineered nanomaterials. The authors used a scanning mobility particle sizer and an optical particle counter to measure the particle number size distributions of particles ranging in diameter (D(p)) from 10 nm to >5000 nm in a fullerene factory and used scanning electron microscopy to examine the morphology of the particles. Comparisons of particle size distributions and morphology during non-work periods, during work periods, during an agitation process, and in the nearby outdoor air were conducted to identify the sources of the particles and to determine their physical properties. A modal diameter of 25 nm was found in the working area during the non-work period; this result was probably influenced by ingress of outdoor air. During the removal of fullerenes from a storage tank for bagging and/or weighing, the particle number concentration at D(p)<50 nm was no greater than that in the non-work period, but the concentration at D(p)>1000 nm was greater during the non-work period. When a vacuum cleaner was in use, the particle number concentration at D(p)<50 nm was greater than that during the non-work period, but the concentration at D(p)>1000 nm was no greater. Scanning electron microscopy revealed that the coarse particles emitted during bagging and/or weighing were aggregates/agglomerates of fullerenes; although origin of particles with D(p)<50 nm is unclear.
    Journal of Occupational and Environmental Hygiene 06/2008; 5(6):380-9. · 1.21 Impact Factor
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    ABSTRACT: Thymus atrophy is induced by a variety of chemicals, including environmental contaminants and is used as a sensitive index to detect their adverse effects on lymphocytes. In the present study we adopted a toxicogenomics approach to identify the pathways that mediate the atrophy induced by arsenite. We also analyzed gene expression changes observed in the course of thymus atrophy by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dexamethasone (DEX), and estradiol (E2), to determine whether arsenite induces atrophy by activating an arsenite-specific pathway or the same pathways as other chemicals. These compounds were intraperitoneally administered to C57BL/6 mice at doses that reduce thymus weight by approximately 30% within 3 days, and gene expression changes in the thymus 24 h after the administration were analyzed by using microarrays and real-time PCR. The microarray analysis showed that arsenite specifically downregulates a variety of E2F target genes that are involved in cell cycle progression. The same genes were also downregulated when mouse B-cell lymphoma A20 cells were exposed to arsenite. Arsenite exposure of the A20 cells was confirmed to induce cell cycle arrest, mainly in the G(1) phase, and reduce cell number. Cell cycle arrest in the G(1) phase was also confirmed to occur in the thymocytes of the arsenite-exposed mice. These results indicate that arsenite induces thymus atrophy through E2F-dependent cell cycle arrest. The results of this study also show that analysis of gene expression in thymuses is a useful method of obtaining clues to the pathways that mediate the effects of atrophy-inducing chemicals.
    Toxicological Sciences 03/2008; 101(2):226-38. · 4.48 Impact Factor
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    ABSTRACT: Epidemiological studies have suggested that fine particulate matter (f-PM) is associated with adverse effects on cardiovascular health. However, these effects on the cardiovascular system have not yet been fully elucidated. Using mRNA expression and correlation analyses, we designed the present study to elucidate (1) translocation of chemicals in inhaled f-PM to the heart, (2) induction of oxidative stress, one of the causes of cardiovascular diseases (CVDs), (3) mRNA expression related to CVDs, and (4) correlations among mRNA expression of various molecules and cardiovascular function. Wistar Kyoto male rats were exposed to concentrated ambient particles (CAPs, 0.6-1.5mg/m3) in Yokohama for 4 days (4.5h/day) or to filtered air for 3 days and CAPs for 1 day or to filtered air for 4 days. Messenger RNA expression and cardiovascular function were measured after the 4-day exposure. In samples of heart tissue, the mRNAs of cytochrome P450 (CYP) 1B1, a biomarker of exposure to chemicals; heme oxygenase-1 (HO-1), a marker of oxidative stress; and endothelin A (ET A) receptor, a receptor of vasoconstrictors, were up-regulated by CAPs; their levels were significantly correlated with the cumulative weight of CAPs in the exposure chamber. The up-regulation of ET A receptor mRNA was significantly correlated with the increase in HO-1 mRNA and weakly with the increase in mean blood pressure (Delta MBP). These results suggest the possibility that chemicals in CAPs might be translocated to the heart, where they induce oxidative stress and activate endothelin signaling, resulting in an increase in the blood pressure. The exposure to f-PM might thus affect cardiovascular function through activation of endothelin signaling.
    Toxicology 02/2008; 243(3):271-83. · 3.75 Impact Factor
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    ABSTRACT: Recently, there have been increasing reports that nano-sized component of particulate matter can reach the brain and may be associated with neurodegenerative diseases. Previously, our laboratory has studied the effect of intranasal instillation of nano-sized carbon black (CB) (14 nm and 95 nm) on brain cytokine and chemokine mRNA expressions and found that 14-nm CB increased IL-1 beta, TNF-alpha, CCL2 and CCL3 mRNA expressions in the olfactory bulb, not in the hippocampus of mice. To investigate the effect of a single administration of nanoparticles on neurotransmitters and proinflammatory cytokines in a mouse olfactory bulb, we performed in vivo microdialysis and real-time PCR methods. Ten-week-old male BALB/c mice were implanted with guide cannula in the right olfactory bulb and, 1 week later, were instilled vehicle or CB (14 nm, 250 microg) intranasally. Six hours after the nanoparticle instillation, the mice were intraperitoneally injected with normal saline or 50 mug of bacteria cell wall component lipoteichoic acid (LTA), which may potentiate CB-induced neurologic effect. Extracellular glutamate and glycine levels were significantly increased in the olfactory bulb of CB-instilled mice when compared with vehicle-instilled control mice. Moreover, we found that LTA further increased glutamate and glycine levels. However, no alteration of taurine and GABA levels was observed in the olfactory bulb of the same mice. We also detected immunological changes in the olfactory bulb 11 h after vehicle or CB instillation and found that IL-1 beta mRNA expression was significantly increased in CB- and LTA-treated mice when compared with control group. However, TNF-alpha mRNA expression was increased significantly in CB- and saline-treated mice when compared with control group. These findings suggest that nanoparticle CB may modulate the extracellular amino acid neurotransmitter levels and proinflammatory cytokine IL-1 beta mRNA expressions synergistically with LTA in the mice olfactory bulb.
    Toxicology and Applied Pharmacology 02/2008; 226(2):192-8. · 3.63 Impact Factor
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    ABSTRACT: The function of the N-methyl-d-aspartate (NMDA) subtype of glutamatergic receptors is known to be antagonized by toluene, a well-characterized neurotoxic chemical known to impair memory functions. Recently, peripheral T cells have been clearly shown to play an important role in cognitive and behavioral functions. In the present study, we investigated the role of peripheral T cells in the hippocampal mRNA expression of memory-related genes induced by low levels of toluene exposure in mice. BALB/c wild-type (WT) and nude mice were exposed to 9ppm of toluene or filtered air (0ppm toluene; control groups) in a nose-only exposure chamber for 30min on 3 consecutive days followed by weekly sessions for 4 weeks. Twenty-four hours after the last exposure, the hippocampi were collected and the inducibility of memory-related genes was examined using a real-time quantitative PCR method. NMDA NR2A, calcium/calmodulin-dependent protein kinase IV (CaMKIV), cyclic AMP-responsive element binding protein 1 (CREB1), and BDNF were significantly up-regulated in the hippocampi of WT mice exposed to 9ppm of toluene, compared to the expressions observed in WT mice exposed to filtered air, but similar results were not observed in nude mice. To investigate the possible involvement of peripheral T cells in the toluene-induced up-regulation of memory-related genes in WT mice, we examined the mRNA expression of Thy-1 (a pan T cell-specific marker) and quantified the number of cells that were immunoreactive to a T cell antigen receptor, CD3 (CD3-ir). Both the expression of Thy-1 mRNA and the number of CD3-ir cells were significantly higher in the hippocampi of the WT mice exposed to 9ppm of toluene, compared with that in WT mice exposed to filtered air; similar results were not observed in nude mice. We also examined the expression of chemokine genes like CCL2 and CCL3. The expression of CCL3 mRNA was significantly up-regulated only in the toluene-exposed WT mice. Although other differences unrelated to immune function may exist between WT and nude mice from the same background, the findings of the present study strongly suggest that the recruitment of peripheral T cells in the hippocampi of BALB/c WT mice exposed to low levels of toluene may be involved in the toluene-induced up-regulation of memory-related genes at the mRNA level.
    NeuroToxicology 10/2007; 28(5):957-64. · 3.05 Impact Factor
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    ABSTRACT: We have previously shown that intratracheal instillation of carbon nanoparticles exacerbates lung inflammation related to bacterial endotoxin (lipopolysaccharide, LPS) and subsequent systemic inflammation with coagulatory disturbance in mice [Inoue, K., Takano, H., Yanagisawa, R., Hirano, S., Sakurai, M., Shimada, A., Yoshikawa, T., 2006b. Effects of airway exposure to nanoparticles on lung inflammation induced by bacterial endotoxin in mice. Environ. Health Perspect. 114, 1325-1330]. The present study was performed to determine whether inhalation of diesel engine-derived nanoparticles also exacerbates the model. ICR mice were exposed for 5h to clean air or diesel engine-derived nanoparticles at a concentration of 15, 36, or 169 microg/m(3) after intratracheal challenge with 125 microg/kg of LPS or vehicle, and were sacrificed for evaluation 24h after the intratracheal challenge. Nanoparticles alone did not induce lung inflammation. Nanoparticle inhalation increased LPS-elicited inflammatory cell recruitment into the bronchoalveolar lavage fluid and lung parenchyma as compared with clean air inhalation in a concentration-dependent manner. Lung homogenates derived from the nanoparticle+LPS groups tended to have increased tumor necrosis factor-alpha level and chemotaxis activity for polymorphonuclear leukocytes as compared to those from the LPS group or the corresponding nanoparticle groups. Nanoparticle inhalation did not significantly increase lung expression of proinflammatory cytokines or facilitate systemic inflammation and coagulatory disturbance. Isolated alveolar macrophages (AMs) from nanoparticle-exposed mice showed greater production of interleukin-1beta and keratinocyte chemoattractant stimulated with ex vivo LPS challenge than those from clean air-exposed mice, although the differences did not reach statistical significance. These results suggest that acute exposure to diesel nanoparticles exacerbates lung inflammation induced by LPS.
    Toxicology 10/2007; 238(2-3):99-110. · 3.75 Impact Factor
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    ABSTRACT: Aerosol Science and Technology 41(1): 14–23
    Aerosol Science and Technology 02/2007; 41(3):342-342. · 3.16 Impact Factor
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    ABSTRACT: The effects of components of ambient particulate matter (PM) on individuals with predisposing respiratory disorders are not well defined. We have previously demonstrated that airway exposure to diesel exhaust particles (DEP) or organic chemicals (OC) extracted from DEP (DEP-OC) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide, LPS). The present study aimed to examine the effects of airway exposure to OC extracted from urban PM (PM-OC) on lung inflammation related to LPS. ICR mice were divided into four experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), PM-OC (4 mg/kg), or PM-OC + LPS. Lung inflammation, lung water content, and lung expression of cytokines were evaluated 24 h after intratracheal administration. LPS challenge elicited lung inflammation evidenced by cellular profiles of bronchoalveolar lavage fluid and lung histology, which was further aggravated by the combined challenge with PM-OC. The combination with PM-OC and LPS did not significantly exaggerate LPS-elicited pulmonary edema. LPS instillation induced elevated lung expression of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant, whereas the combined challenge with PM-OC did not influence these levels. All the results were consistent with our previous reports on DEP-OC. These results suggest that the extracted organic chemicals from PM exacerbate infectious lung inflammation. The mechanisms underlying the enhancing effects are not mediated via the enhanced local expression of proinflammatory cytokines.
    Archive für Toxikologie 01/2007; 80(12):833-8. · 5.08 Impact Factor
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    ABSTRACT: We analyzed the health risk of particulate matters in the air to humans using bioassay data and a mathematical model. We designed an original dosimetry model to estimate the particle concentration in human respiratory organs, and the concentration of the inhaled particles at the target organ was used for interspecies extrapolation from rat to human. Our model is based on the conventional dosimetry model and deposition model in the previous literature, but clearance parameters have been newly introduced for the simulation of long-term exposure. Lung cancer was set as the risk endpoint in our risk study, and the dose-response relationship at the target organ (lung) was quantitatively analyzed by the benchmark dose (BMD) method. For interspecies extrapolation based on target organ concentration, we assumed benchmark concentration (BMC) related to 1% excess cancer in rats and humans, and the human equivalent concentration (HEC) was searched by back-estimation using our model. The obtained HEC was 948 to 1098 mg/m3, and the unit risk to humans was 9.11 to 10.5 x 10(-9) per 1 microg/m3 of particulate matter. The estimated cancer risk for Japanese people in general was estimated as approximately 9-10 persons per 100,000,000 when the particle concentration in the air is 10 microg/m3.
    Inhalation Toxicology 01/2007; 18(13):1013-23. · 1.89 Impact Factor
  • Eiko Koike, Takahiro Kobayashi
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    ABSTRACT: Several studies show that ultrafine particles have a larger surface area than coarse particles, thus causing a greater inflammatory response. In this study, we investigated chemical and biological oxidative effects of nanoparticles in vitro. Carbon black (CB) nanoparticles with mean aerodynamic diameters of 14, 56, and 95nm were examined. The innate oxidative capacity of the CB nanoparticles was measured by consumption of dithiothreitol (DTT) in cell-free system. The expression of heme oxygenase-1 (HO-1) in rat alveolar type II epithelial cell line (SV40T2) and alveolar macrophages (AM) exposed to CB nanoparticles was measured by ELISA. DTT consumption of 14nm CB was higher than that of other CB nanoparticles having the same particle weight. However, DTT consumption was directly proportional to the particle surface area. HO-1 protein in SV40T2 cells was significantly increased by the 14nm and 56nm CB, however, 95nm CB did not affect. HO-1 protein in AM was significantly increased by the 14, 56, and 95nm CB. The increase in HO-1 expression was diminished by N-acetyl-l-cysteine (NAC) treatment of each CB nanoparticles before exposure although the difference between the effects of NAC-treated and untreated 14nm CB did not achieve significant. In conclusion, CB nanoparticles have innate oxidative capacity that may be dependent on the surface area. CB nanoparticles can induce oxidative stress in alveolar epithelial cells and AM that is more prominent with smaller particles. The oxidative stress may, at least partially, be mediated by surface function of particles.
    Chemosphere 12/2006; 65(6):946-51. · 3.50 Impact Factor
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    ABSTRACT: Epidemiological studies have shown that particulate matter (PM) is associated with adverse respiratory health effects. Although infection in the respiratory organ is one of the most important health risks the association of infection with PM is not fully understood. As we had hypothesized that diesel exhaust particles (DEP), one of the major component of PM, may induce the expression of receptors for viruses and bacteria at invasion sites, we studied the effect of DEP on the mRNA expression of intercellular adhesion molecule-1 (ICAM-1), low-density lipoprotein (LDL) and platelet-activating factor (PAF) receptors, which are invasion sites of virus and bacteria, on rat lung epithelial cells. The real-time quantitative polymerase chain reaction (PCR) method was used for the evaluation. All of these mRNAs were up-regulated by 3, 10, and 30 microg/ml of DEP in a concentration-dependent manner. The up-regulation of each was associated with the mRNA expression of heme oxygenase-1 (HO-1), a marker of oxidative stress. Our present results show that DEP up-regulated the mRNA expression of viral and bacterial receptors. This up-regulation might be associated with DEP-induced oxidative stress. These results thus suggest that DEP may enhance the risk of pneumonia by increasing the density of bacterial and viral invasion sites in the lungs.
    Toxicology Letters 09/2006; 165(1):66-70. · 3.36 Impact Factor
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    ABSTRACT: We studied the interaction effects of a single intratracheal instillation of ultrafine carbon black (CB) particles and staphylococcal lipoteichoic acid (LTA) on early pulmonary inflammation in male BALB/c mice. We examined the cellular profile, cytokine and chemokine levels in the bronchoalveolar lavage (BAL) fluid, and expression of chemokine and toll-like receptor (TLR) mRNAs in lungs. LTA produced a dose-related increase in early pulmonary inflammation, which was characterized by (1) influx of polymorphonuclear neutrophils (PMNs) and (2) induction of interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, macrophage inflammatory protein (MIP)-1alpha/CCL3, but no effect on monocyte chemoattractant protein (MCP)-1/CCL2 at 24 h after instillation. Levels of some proinflammatory indicators and TLR2-mRNA expression were significantly increased by 14 nm or 95 nm CB (125 microg) and low-dose LTA (10 microg) treatment compared to CB or LTA alone at 4 h after instillation. Notably, PMN levels and production of IL-6 and CCL2 in the 14 nm CB + LTA were significantly higher than that of 95 nm CB + LTA at 4 h after instillation. However, at 24 h after instillation, only PMN levels were significantly higher in the 14 nm CB + LTA than 95 nm CB + LTA but not the cytokines and chemokines. These data show additive as well as synergistic interaction effects of 14 nm or 95 nm ultrafine CB particles and LTA. We suggest that early pulmonary inflammatory responses in male BALB/c mice may be induced in a size-specific manner of the CB particles used in our study.
    Toxicology and Applied Pharmacology 07/2006; 213(3):256-66. · 3.63 Impact Factor
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    ABSTRACT: Ambient air ultrafine particles (UFPs) have gained enormous attention to many researchers with recent evidence showing them to have more hazardous effects on human health than larger ambient particles. Studies focusing the possibility of effects on brain are quite limited. To examine the effect of ultrafine carbon black (ufCB) on mice brain, we instilled 125 microg of 14 nm or 95 nm CB into the nostrils of 8-week-old male BALB/c mice, once a week for 4 weeks. Four hours after the last instillation, we collected olfactory bulb and hippocampus and detected the expression of cytokine and chemokine mRNA by quantitative real-time PCR method. In this study, we found the induction of proinflammatory cytokines (interleukin-1 beta and tumor necrosis factor-alpha and chemokines (monocyte chemoattractant protein-1/CCL2, macrophage inflammatory protein-1 alpha/CCL3), and monokine induced interferon-gamma/CXC chemokine ligand (CXCL9) mRNA in brain olfactory bulb, not in the hippocampus of mice instilled with 14 nm ufCB intranasally. We suggest that the intranasal instillation of ufCB may influence the brain immune function depending on their size. To our knowledge, this is the first study to demonstrate region-specific brain cytokine and chemokine mRNA-induction in mice triggered by intranasal instillation of specific-sized ufCB, in a physiologically relevant condition.
    Toxicology Letters 06/2006; 163(2):153-60. · 3.36 Impact Factor
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    ABSTRACT: Diesel exhaust particles (DEP) are known to induce adverse biological responses such as inflammation of the airway. However, the relationship between the chemical characteristics of organic compounds adsorbed on DEP and their biological effects is not yet fully understood. In this study, the dichloromethane-soluble fraction (DMSF) from DEP was fractionated into its n-hexane-soluble fraction (n-HSF) and n-hexane-insoluble fraction (n-HISF). Using these DEP fractions, we designed the present studies to elucidate (1) chemical characteristics, (2) biological characteristics, and (3) the relationship between the chemical and the biological characteristics of these DEP fractions. Dithiothreitol (DTT) assay, Fourier transform-infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H-NMR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS) were used to characterize their chemical properties. Heme oxygenase-1 (HO-1) protein expression, viability of rat alveolar type II epithelial cell line (SV40T2), and inflammatory cell infiltration into the peritoneal cavity of BALB/c mice were evaluated as markers of oxidative stress, cytotoxicity, and inflammatory response, respectively. The oxidative ability of the DEP fractions was n-HISF > DMSF > n-HSF. IR, 1H-NMR, and GC-MS spectra showed that n-HISF was mainly composed of compounds having many functional groups related to oxygenation, such as hydroxyl and carbonyl groups. The relative strength of HO-1 protein expression, cytotoxicity, and inflammatory responses was also n-HISF > DMSF > n-HSF. All of the n-HISF-induced biological activities were decreased by reduction with N-acetyl-L-cysteine (NAC). These results suggest that n-HISF has high oxidative ability and many functional groups related to oxygenation and that this ability strongly contributes to the induction of oxidative stress, cytotoxicity, and inflammatory response.
    Toxicological Sciences 05/2006; 91(1):218-26. · 4.48 Impact Factor
  • Akiko Furuyama, Seishiro Hirano, Eiko Koike, Takahiro Kobayashi
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    ABSTRACT: Endothelial cells play important roles in anticoagulant and fibrinolytic systems. Recent studies suggest that increases in ambient particulate matter (PM) levels have been associated with an increase in mortality rate from cardiovascular diseases. We examined the production of heme oxygenase-1 (HO-1) and factors related to the fibrinolytic function by rat heart microvessel endothelial cells exposed to organic extracts of diesel exhaust particles (OE-DEP) and urban fine particles (OE-UFP) to investigate the direct effects of these soluble organic fractions in these PM on the fibrinolytic function of endothelial cells. The cell monolayer exposed to 10 microg/ml OE-DEP produced a larger amount of HO-1 than cells exposed to 10 microg/ml OE-UFP. OE-DEP and OE-UFP exposure reduced plasminogen activator inhibitor-1 (PAI-1) production by the cells but did not affect the production of thrombomodulin, tissue-type plasminogen activator, or urokinase-type plasminogen activator. Increased PAI-1 synthesis in response to treatment with 1.0 ng/ml tumor necrosis factor-alpha or 0.5 ng/ml transforming growth factor-beta1 was reduced by OE-DEP exposure. Suppression of PAI-1 production by OE-DEP exposure was mediated through oxidative stress and was independent of HO-1 activity. These results suggest that exposure to the soluble organic fraction of PM and DEP induced oxidative stress and reduced the PAI-1 production of endothelial cells.
    Archive für Toxikologie 04/2006; 80(3):154-62. · 5.08 Impact Factor

Publication Stats

619 Citations
118.97 Total Impact Points


  • 2002–2009
    • University of Tsukuba
      • School of Medicine
      Tsukuba, Ibaraki, Japan
  • 1995–2009
    • National Institute for Environmental Studies
      • Center for Environmental Health Sciences
      Tsukuba, Ibaraki, Japan
  • 2008
    • Japan Automobile Research institute
      Ibaragi, Ōsaka, Japan
    • Tokyo Institute of Technology
      Edo, Tōkyō, Japan