Nanoparticle-rich Diesel Exhaust Research Articles

Nanoparticle-rich diesel exhaust-induced liver damage via inhibited transactivation of peroxisome proliferator-activated receptor alpha.

Diesel exhaust emission contains a high amount of nano-sized particles and is considered to be systemically distributed in the body. However, few studies about the effects of nanoparticle rich-diesel exhaust (NR-DE) on liver have been reported. The present investigation focuses on the effects of NR-DE on livers in rats, especially concerning inflammation and lipid metabolism. Male F344 rats were exposed to fresh air or low (24 ± 7 µg/m3 ), medium (39 ± 4 µg/m3 ) and high (138 ± 20 µg/m3 ) concentrations of NR-DE for 1, 2, or 3 months (5 hours/day, 5 days/week). Exposure to both medium and high concentrations of NR-DE for one month increased plasma asparate aminotransferase and alanine aminotransferase activities, while only high concentrations increased plasma interleukin-6 and hepatic nuclear factor kappa B (NFκB), suggesting that activation of hepatic inflammatory signaling took place. Although these exposures elevated peroxisome proliferator-activated receptor (PPAR) α levels or its binding activity to the response element, neither activated PPARα-target genes such as β-oxidative enzymes nor inhibited NFκB elevation. Thus, NR-DE may contain some materials that inhibit PPARα activation in relation to lipid metabolism and inflammation. Taken together, NR-DE exposure at one month may cause inflammation; however, this finding may not be observed after a longer exposure period. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1985-1995, 2016.

Effects of exposure to nanoparticle-rich diesel exhaust on 8-OHdG synthesis in the mouse asthmatic lung

It has been demonstrated that exposure to diesel exhaust (DE) is associated with the induction and exacerbation of respiratory disorders; however, the impacts of DE containing mainly nanoparticles have been less studied. We have previously demonstrated that inhalation exposure to nanoparticle-rich DE (NR-DE) exacerbated allergic pulmonary inflammation, in the context of enhanced local expression of proinflammatory molecules. However, the underlying mechanisms have not been fully elucidated. 8-Hydroxydeoxyguanosine (8-OHdG) is a marker of oxidative damage, particularly in DNA. This study examined the effects of NR-DE on 8-OHdG synthesis in the lung in the presence or absence of an allergen. Institute for Cancer Research (ICR) mice were exposed by inhalation to four different gas compositions (control air, low-concentration DE, high-concentration DE and high-concentration DE without particulate matter) for 8 weeks, in the presence or absence of repetitive intratracheal administration of ovalbumin (OVA). Thereafter, we assessed the levels of 8-OHdG synthesis and expression in the lungs by means of enzyme immunoassay (EIA) and immunohistochemistry. The EIA revealed that the level of 8-OHdG was significantly higher in the high-concentration NR-DE-exposed and allergen-sensitized/stimulated group compared with that in the control air-exposed and allergen-treated group. The immunohistochemistry results demonstrated that the level of immunoreactive 8-OHdG was higher in the NR-DE-exposed and allergen-treated lungs compared with that in the corresponding control air-exposed lungs. The results suggested that NR-DE exposure enhanced 8-OHdG formation in asthmatic lungs. This, at least in part, is involved in the NR-DE-mediated exacerbation of the allergic pathophysiology that was identified in our previous study.

Effects of exposure to nanoparticle-rich or -depleted diesel exhaust on allergic pathophysiology in the murine lung

Although it has been shown that exposure to diesel exhaust (DE) is linked to the induction or exacerbation of respiratory disorders, the major components responsible have not been fully identified. We examined the effects of airway exposure to nanoparticle-rich DE (NR-DE) or DE without particles on allergic pulmonary inflammation in mice. We also investigated the cellular responses to intratracheal instillation of NR-DE particles (NR-DEP). ICR mice inhaled one of four different mixtures (control air, low-concentration DE, high-concentration DE, and high-concentration DE without particles) for 8 weeks in the presence or absence of repeated intratracheal administration of ovalbumin (OVA). In a separate study, NR-DEP and/or OVA were repeatedly administrated intratracheally to mice. High-concentration NR-DE or DE without particles substantially exacerbated OVA-induced eosinophilic airway inflammation. This exacerbation was concomitant with increases in lung levels of Th2 cytokines such as interleukin (IL)-4, IL-5, and IL-13 and of chemokines such as monocyte chemotactic protein-1. Furthermore, in the presence of allergen, both DE without particles and high-concentration NR-DE strongly enhanced the production and release of myeloperoxidase into the alveolar spaces. Repeated administration of NR-DEP did not substantially affect the allergic asthma. These results strongly suggest that gaseous compounds in NR-DE aggravate murine allergic airway inflammation, mainly via amplification of the Th2 response.

Effects of Exposure to Nanoparticle-rich Diesel Exhaust on Pregnancy in Rats

Pollutants from burning of diesel fuel are hazardous to human health. Nanoparticles in diesel exhaust potentially have profound impact on fetal development and maternal endocrine function during pregnancy due to their ability to penetrate deeply into the body. To investigate the effects of nanoparticle-rich diesel exhaust (NR-DE) on pregnancy, pregnant rats were exposed to NR-DE, filtered diesel exhaust (F-DE) or clean air for 19 days of gestation. Relative weights of maternal liver and spleen to body weight were significantly lower in the NR-DE and F-DE groups than those in the control group. The serum concentration of maternal progesterone was significantly lower, while those of luteinizing hormone (LH) and corticosterone were significantly higher in the NR-DE and F-DE groups than those in the control group. The serum concentration of estradiol-17β was significantly higher in the F-DE group than that in the control group. The levels of cytochrome P450 side-chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase and LH receptor mRNA in the corpus luteum were significantly lower in the NR-DE and F-DE groups than those in the control. In fetuses, body weight and crown-rump length were significantly greater and shorter, respectively, in both males and females in the NR-DE and F-DE groups than those in the control group. These results demonstrate that exposure of pregnant rats to NR-DE and F-DE suppresses the function of corpora lutea and stimulates the function of the adrenal cortex, suggesting a risk of spontaneous abortion associated with maternal hormonal changes.

Effect of nanoparticle-rich diesel exhaust on testosterone biosynthesis in adult male mice

The effect of nanoparticle-rich diesel exhaust (NR-DE) on the testicular function and factors related with the biosynthesis of testosterone gene expression were investigated in mice. Male C57BL/Jcl mice were exposed to clean air, low-dose NR-DE (Low NR-DE), high-dose NR-DE (High NR-DE) or filtered diesel exhaust (F-DE) for 8 weeks. We found that the mice exposed to High NR-DE had significantly higher testosterone levels than those in the control and F-DE groups. To determine the effects of NR-DE on testicular testosterone production, interstitial cells dissected from the male mice which were exposed to NR-DE, F-DE, or clean air for 8 weeks were incubated with or without human chorionic gonadotropin (hCG; 0.1 IU/mL) for 4 h. The concentrations of testosterone in the culture media were measured. The testosterone production was significantly increased in with or without hCG of High NR-DE exposed group, and significantly decreased in both with or without hCG of F-DE exposed groups. Moreover, several genes, which is associated with testicular cholesterol synthesis, HMG-CoA, LDL-R, SR-B1, PBR, and P450scc, P450 17α, and 17β-HSD were determined in the testis of adult male mice. The results showed High NR-DE exposure significantly increased the expression of these genes. Whereas, the levels in the F-DE exposure group returned to those in the control group, implicating that the nanoparticles in DE contribute to the observed reproductive toxicity. We conclude that enhancement of testosterone biosynthesis by NR-DE exposure may be regulated by increasing testicular enzymes of testosterone biosynthesis.

Effect of nanoparticle-rich diesel exhaust on testicular and hippocampus steroidogenesis in male rats

Background: Nanoparticle-rich diesel exhaust (NR-DE) has potentially adverse effects on testicular steroidogenesis. However, it is unclear whether NR-DE influences steroidogenic systems in the brain.Objective: To investigate the effect of NR-DE on hippocampal steroidogenesis of adult male rats in comparison with its effect on the testis.Methods: F344 male rats (8-week-old) were randomly divided into four groups (n = 8 or 9 per group) and exposed to clean air with 4.6 ± 3.2 μg/m3 in mass concentration, NR-DE with 38 ± 3 μg/m3 (a level nearly equivalent to the environmental standard in Japan (low NR-DE)), NR-DE with 149 ± 8 μg/m3 (high NR-DE), or filtered diesel exhaust with 3.1 ± 1.9 μg/m3 (F-DE), for 5 hours/day, 5 days/week, for 1, 2 or 3 months. F-DE was prepared by removing only particulate matters from high NR-DE with an HEPA filter.Results: Exposures to the high NR-DE for 1 month, and low NR-DE for 2 months, significantly increased or tended to increase plasma and testicular testosterone levels compared to clean air exposure, which might have resulted from the increased expression of mRNA of steroidogenic acute regulatory protein and its protein in the testes of rats. In the hippocampus, high NR-DE exposure for 1 month significantly increased the androstendione level compared to the clean air exposure, while no significant difference was observed in the steroidogenesis between fresh air exposure and any exposure to NR-DE or F-DE.Conclusion: NR-DE may influence steroidogenic enzymes in the testis, but not those in the hippocampus.

Novel object recognition ability in female mice following exposure to nanoparticle-rich diesel exhaust

Recently, our laboratory reported that exposure to nanoparticle-rich diesel exhaust (NRDE) for 3months impaired hippocampus-dependent spatial learning ability and up-regulated the expressions of memory function-related genes in the hippocampus of female mice. However, whether NRDE affects the hippocampus-dependent non-spatial learning ability and the mechanism of NRDE-induced neurotoxicity was unknown. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE, 47μg/m3), high-dose NRDE (H-NRDE, 129μg/m3), or filtered H-NRDE (F-DE) for 3months. We then investigated the effect of NRDE exposure on non-spatial learning ability and the expression of genes related to glutamate neurotransmission using a novel object recognition test and a real-time RT-PCR analysis, respectively. We also examined microglia marker Iba1 immunoreactivity in the hippocampus using immunohistochemical analyses. Mice exposed to H-NRDE or F-DE could not discriminate between familiar and novel objects. The control and M-NRDE-exposed groups showed a significantly increased discrimination index, compared to the H-NRDE-exposed group. Although no significant changes in the expression levels of the NMDA receptor subunits were observed, the expression of glutamate transporter EAAT4 was decreased and that of glutamic acid decarboxylase GAD65 was increased in the hippocampus of H-NRDE-exposed mice, compared with the expression levels in control mice. We also found that microglia activation was prominent in the hippocampal area of the H-NRDE-exposed mice, compared with the other groups. These results indicated that exposure to NRDE for 3months impaired the novel object recognition ability. The present study suggests that genes related to glutamate metabolism may be involved in the NRDE-induced neurotoxicity observed in the present mouse model.

Effects of nanoparticle-rich diesel exhaust particles on IL-17 production in vitro

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupt immune systems, presenting as exacerbating effects on allergic manifestations (e.g., allergic asthma). To date, the impact of nano-level DEP on health has not been fully elucidated. Our institute (the National Institute for Environmental Studies) established an ‘environmental nanoparticle exposure system applied in animals’ in 2005 and, since then, the health effects of exposures to these types of agents have been explored. The present study was designed to investigate the in vitro effects of nanoparticle-rich DEP (NRDEP) on primary splenocytes from atopy-prone hosts. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0–50 µg/ml); thereafter, cell viability/proliferation was evaluated via a WST-1 assay, production/release of interleukin (IL)-17A in the culture supernatants by ELISA, and expression of RORγt (retinoic acid-related orphan receptor-γt) in cell lysates by Western blot analyses. The results indicated that NRDEP reduced cell viability/proliferation in a dose-related manner—significantly so at a level of 50 µg/ml NRDEP. In contrast, up to 10 µg NRDEP/ml increased RORγt expression in the splenocytes and subsequent IL-17A production/release by the cells in a dose-dependent manner with an overall trend (with significance vs 1 µg NRDEP/ml and 10 µg NRDEP/ml for IL-17A); 50 µg NRDEP/ml tended to inhibit the transcription factor expression and cytokine production/release. These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals in terms of RORγt and IL-17A induction (TH17 response).

Effects of exposure to nanoparticle-rich diesel exhaust on adrenocortical function in adult male mice

To investigate the effects of nanoparticle-rich diesel exhaust (NR-DE) on adrenocortical function, seven-week-old male mice were divided into four groups and exposed to either whole NR-DE at low (41.73μg/m3, 8.21×105particles/cm3), high (152.01μg/m3, 1.80×106particles/cm3) concentrations, filtered diesel exhaust (F-DE) or clean air for 8 weeks (5h/day, 5 days/week). After 8 weeks of exposure, the animals were euthanized under pentobarbital anesthesia and the blood samples were collected to detect serum progesterone and corticosterone. In addition, adrenal glands were excised, and adrenal cells were cultured in the absence or presence of rat adrenocorticotropic hormone (ACTH) (10−15 to 10−10M) for 4h. There were no significant differences in the body weight, absolute and relative adrenal gland weight among the groups. Serum concentration of corticosterone and progesterone was not changed significantly. Administration of ACTH resulted in a dose-dependent increase in corticosterone and progesterone release in mice-exposed to low-concentration NR-DE and clean air. Moreover, corticosterone and progesterone concentrations in adrenal cells increased significantly in mice-exposed to low-concentration NR-DE basal and administrated with ACTH (10−15 to 10−11M for corticosterone; 10−14 to 10−11M for progesterone) compared with the control mice. In contrast, the concentration of corticosterone and progesterone decreased significantly in mice-exposed to high-concentration NR-DE or F-DE basal and administrated with ACTH (10−12 to 10−10M for corticosterone; 10−15 to 10−10M for progesterone) compared with the control mice. These results suggest that exposure to NR-DE or F-DE may disrupt adrenocortical function in adult male mice.

Hippocampus-dependent spatial learning deficit in mice following sub-chronic exposure to nanoparticle-rich diesel exhaust

Hippocampus-dependent spatial learning deficit in mice following sub-chronic exposure to nanoparticle-rich diesel exhaust

Nanoparticle-rich diesel exhaust affects hippocampal-dependent spatial learning and NMDA receptor subunit expression in female mice

We investigated the effect of exposure to nanoparticle-rich diesel exhaust (NRDE) on hippocampal-dependent spatial learning and memory function-related gene expressions in female mice. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE), high-dose NRDE (H-NRDE) or filtered diesel exhaust (F-DE) for three months. A Morris water maze apparatus was used to examine spatial learning. The expression levels of the N-methyl-D-aspartate (NMDA) receptor subunit, proinflammatory cytokines and neurotrophin mRNAs in the hippocampus were then investigated using real-time RT-PCR. Mice exposed to H-NRDE required a longer time to reach the hidden platform and showed higher mRNA expression levels of the NMDA receptor subunit NR2A, the proinflammatory cytokine CCL3, and brain-derived neurotrophic factor (BDNF) in the hippocampus, compared with the findings in the control group. These results indicate that three months of exposure to NRDE affected spatial learning and memory function-related gene expressions in the female mouse hippocampus.

In vitro effects of nanoparticle-rich diesel exhaust particles on splenic mononuclear cells

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupt immune systems, presenting as exacerbating effects on allergic manifestations (i.e., allergic asthma). However, since inhalation system could not be developed, impact of nano-level DEP on health has not been satisfactorily elucidated. Our institute (National Institute for Environmental Studies) established the “environmental nanoparticle exposure system applied in animals” in 2005, and, since then, we have explored the health effects of the exposure. As part of our ongoing research, the present study was aimed to investigate the effects of nanoparticle-rich DEP (NRDEP) on the characterization of primary atopy-prone splenocytes in vitro. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0–50 µg/ml); thereafter, the surface expression of CD11c, CD80, CD86, CD69, and CD40L was evaluated by means of flow cytometry. NRDEP increased the surface expression of these molecules on the splenocytes in a dose-dependent manner with an overall trend (with significance vs. 50 µg/ml of NRDEP). These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals.

Effects of Nanoparticle-Rich-Diesel Exhaust on Steroidogenesis in Rats and the Mechanism Underlying Such Effects

Diesel exhaust (DE) is one of the major air pollutants in the world. DE disrupts steroid hormone levels, which may result from the disruption of spermatogenesis. Steroidogenesis occurs not only in the testis but also in the brain. Therefore, we investigated the effects of nanoparticle-rich DE (NR-DE) on steroidogenesis in both the testis and hippocampus. Exposure to NR-DE at concentrations comparable to the environmental standard for particulate matters 2.5 (PM(2.5)) in Japan increased plasma testosterone level. This exposure increased the expression levels of genes involved in steroidogenesis in the testis, but not in the hippocampus, suggesting that NR-DE disrupts steroid hormone balance. This finding suggests the need to reconsider the environmental limit of PM(2.5) in Japan.

Exposure to Nanoparticle-Rich Diesel Exhaust May Cause Liver Damage

Diesel exhaust (DE) is one of the air pollutants in the world, and exposure to DE is an environmental health concern. Most studies amongst the limited number of studies on hepatotoxicity have focused on genotoxicity or mutagenicity. However, DE exposure may cause liver damage because one prospective study suggests that DE exposure is associated with increased mortality due to arteriosclerosis and cirrhosis of the liver. Peroxisome proliferator-activated receptor (PPAR) α plays a role in the regulation of lipid homeostasis and inflammation and thereby may be involved in the progression of atherosclerosis. We investigated whether nanoparticle-rich diesel exhaust (NR-DE) affects the liver and how PPARα is involved in the NR-DE induced effects. We report these results briefly in this minireview. Our results suggest NR-DE-induced hepatic inflammation and dyslipidemia. PPARα may be involved in the development of these disorders.

Exposure to Nanoparticle-Rich Diesel Exhaust Affects Hippocampal Functions in Mice

Epidemiological studies have indicated associations between day-to-day particulate air pollution and increased risks of various adverse health outcomes. Although an association between exposure to diesel exhaust particles (DEPs) and the development of pulmonary inflammation has been reported, there are limited reports on the neurotoxic effects of DEPs, particularly those of nanoparticle-rich diesel exhaust (NRDE). In this minireview, we highlighted the effects of NRDE which was generated in the National Institute for Environmental Studies, on hippocampus-dependent spatial learning ability and the expression of memory-function-related genes, neurotrophins, and proinflammatory cytokines in a mouse model.

In vitro study of the effect of nanoparticle-rich diesel exhaust particles on IL-18 production in splenocytes

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupts the immune system, presenting as exacerbating effects on allergic manifestations (e.g., allergic asthma). However, since a model inhalation system has not been developed, the impact of nano-level DEP on health has not been satisfactorily investigated. Our institute (the National Institute for Environmental Studies) established an "environmental nanoparticle exposure system applied in animals" in 2005 and since then, we have explored the health effects of exposure to these types of agent. The present study was conducted to investigate the in vitro effects of nanoparticle-rich DEP (NRDEP) on primary splenocytes from atopy-prone hosts. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0-50 µg/ml); thereafter, the production/release of interleukin (IL)-18 in the culture supernatants was evaluated by means of ELISA. NRDEP increased IL-18 production/release by splenocytes in a dose-dependent manner with an overall trend (with significance vs. 10 µg/ml of NRDEP). In contrast, 50 µg/ml of NRDEP inhibited production/release. These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals in terms of IL-18 induction.

Nasal instillation of nanoparticle-rich diesel exhaust particles slightly affects emotional behavior and learning capability in rats

In the present study, in order to reveal novel adverse effects of ultrafine particles (UFP) on the central nervous system, the effects of nanoparticle-rich diesel exhaust particles (NRDEP; count mode diameter, 21.45 nm) on emotional behavior, learning capability and brain neurotransmitter levels were studied in rats by intranasal instillation (iNI). NRDEP (10 and 50 µg/rat) was instilled into 2-week old infant, male rats once a week for 4 weeks. Spontaneous motor activity measured was observed to be inverse to the dose level. In active avoidance tests using a shuttle box, NRDEP-treated animals showed a lower avoidance performance than control animals given air-instillation. The levels of dopamine and its metabolite (DOPAC) in the medial mammillary nucleus of the brain tended to be lower in the NRDEP-treated animals. From these results, although the effects of NRDEP by iNI on the emotionality and the brain neurotransmitter levels were not fully clear, the results obtained by avoidance testing suggested involvement of UFP in learning capability.

Mechanism analysis of nanoparticle-rich diesel exhaust induced liver damage in F344 rats

Mechanism analysis of nanoparticle-rich diesel exhaust induced liver damage in F344 rats

Does nanoparticle-rich diesel exhaust exposure affect learning performance in mice?

Responding in rats was maintained under a fixed-ratio 30 schedule of food presentation. When administered acutely buprenorphine (0.018–0.56 mg/kg) produced dose-related decreases in overall rate of responding. In addition to schedule-controlled behavior, the analgesic effects of buprenorphine were evaluated during chronic administration using the tail-flick method. Tolerance developed to the effects of buprenorphine on both measures. In general dose-effect curves for the rate-decreasing effects of buprenorphine were shifted to the right by approximately 2 log units. In one subject, however, tolerance did not develop to the rate-decreasing effects of 10 mg/kg, suggesting that behavioral tolerance to buprenorphine is dose limited. Finally, the data also suggested that tolerance may develop more slowly, yet more completely, to the analgesic than to the rate-decreasing effects of buprenorphine.

Nanoparticle-rich diesel exhaust may disrupt testosterone biosynthesis and metabolism via growth hormone

We previously reported that exposure to low (22.5±0.2nm in diameter, 15.4±1.0μg/m3 in mass weight, 2.27×105/cm3 in mean number concentration), and medium (26.1±0.5nm, 36.4±1.2μg/m3, 5.11×105/cm3) concentrations of nanoparticle-rich diesel exhaust (NR-DE) for 1 and 2 months (5h/day, 5 days/week) significantly increased plasma testosterone in male Fischer 344 rats, whereas exposure to a high concentration (27.1±0.5nm, 168.8±2.7μg/m3, 1.36×106/cm3) did not. The present study attempts to clarify the mechanism of this elevation. Low and medium exposures to NR-DE for 1 and 2 months significantly increased steroidogenic acute regulatory protein (StAR)- and cytochrome P450 side-chain cleavage (P450scc)-mRNA and their protein expressions in the testis of rats, in which the elevation pattern was very similar to that of plasma testosterone levels. Interestingly, both exposure levels for 1 month significantly increased growth hormone (GH) receptor expression in the testis, and low exposure also increased testicular insulin-like growth factor I-mRNA levels and hepatic microsomal cytochrome P450 2C11-mRNA and their protein levels in rats. These two factors are thought to be related to growth hormone secretion. Disruption of testosterone biosynthesis by NR-DE exposure may be a mode of action for reproductive toxicity, which may, in part, be regulated by increasing StAR and P450scc expressions via GH signalling.