Yuichi Miyabara

Involvement of superoxide and nitric oxide on airway inflammation and hyperresponsiveness induced by diesel exhaust particles in mice

We previously demonstrated that chronic intratracheal instillation of diesel exhaust particles (DEP) induces airway inflammation and hyperresponsiveness in the mouse, and that these effects were partially reversed by the administration of superoxide dismutase (SOD). In the present study, we have investigated the involvement of superoxide in DEP-induced airway response by analyzing the localization and activity of two enzymes: (1) a superoxide producer, NADPH cytochrome P-450 reductase (P-450 reductase), and (2) a superoxide scavenger, SOD, in the lungs of the exposed mice and controls. P-450 reductase was detected mainly in ciliated cells and clara cells: its activity was increased by the repeated intratracheal instillation of DEP. While CuZn-SOD and Mn-SOD were also present in the airway epithelium, their activity was significantly decreased following DEP instillation. Exposure to DEP doubled the level of nitric oxide (NO) in the exhaled air. DEP exposure also increased the level of constitutive NO synthase (cNOS) in the airway epithelium and inducible NO synthase (iNOS) in the macrophages. Pretreatment with N-G-monomethyl L-arginine, a nonspecific inhibitor of NO synthase, significantly reduced the airway hyperresponsiveness induced by DEP. These results indicate that superoxide and NO may each contribute to the airway inflammation and hyperresponsiveness induced by the repeated intratracheal instillation of DEP in mice.

Effects of diesel exhaust on allergic airway inflammation in mice.

BACKGROUND Eosinophilic infiltration and goblet cell hyperplasia were induced by the intratracheal instillation of diesel exhaust particles and ovalbumin in mice. However, it is unknown whether its results differ from the effects of the inhalation of diesel exhaust and allergen. OBJECTIVES The purpose of this study was to compare the effects of diesel exhaust inhalation and intratracheal instillation of diesel exhaust particles in a murine asthma model. METHODS ICR mice were exposed to 3 mg soot per cubic meter of diesel exhaust for 6 weeks. After the first week, animals were sensitized by intraperitoneal injection of ovalbumin and aluminum hydroxide gel. After 5 weeks of diesel exhaust exposure, the mice were challenged with ovalbumin. The animals were killed 1, 2, 3, and 7 days after the challenge and investigated for airway inflammation, hyperplasia of goblet cells, airway hyperresponsiveness, local cytokine expression, and antigen-specific IgE and IgG1 production. RESULTS Exposure to diesel exhaust enhanced infiltration of eosinophils and neutrophils in murine airways even 1 day after the challenge. An increment of goblet cells under the bronchial epithelium was followed by the recruitment of inflammatory cells. Furthermore, exposure to diesel exhaust combined with ovalbumin sensitization enhanced respiratory resistance and expression of IL-5 in lung tissue and IgG1 production but not IgE. However, diesel exhaust alone did not induce pathologic changes in mice. CONCLUSIONS Diesel exhaust enhanced allergic airway inflammation, hyperplasia of goblet cells, and airway hyperresponsiveness caused by ovalbumin sensitization.

Murine strain differences in allergic airway inflammation and immunoglobulin production by a combination of antigen and diesel exhaust particles.

To clarify the relationship between the manifestations of allergic airway inflammation modulated by diesel exhaust particles (DEP) and immunoglobulin production in response to an antigen, airway inflammation characterized by the infiltration of eosinophils, goblet cell proliferation, and antigen-specific immunoglobulin (Ig) production was investigated in five strains of mice after immunization with ovalbumin (OA). Mice were injected intratracheally with OA (1 microg) or OA (1 microg) + DEP (50 microg) four times at 3-week intervals. The order of antigen-specific IgG1 production in plasma of mouse strains treated with OA alone was CBA/2N <BDF/1 <C57BL/6 < ICR <C3H/He. The adjuvant effect of DEP on IgG1 production was observed in CBA/2N, BDF/1, ICR, and C57BL/6 mice. The immune activity in BDF/1 mice was significantly elevated (P < 0.01). The OA-specific IgE in plasma was unaffected by antigen challenge with or without DEP in any strain. The degree of eosinophilic inflammation and goblet cell proliferation in the airway induced by OA alone or OA + DEP corresponded well with the antigen-specific IgG1 production. These results suggest that the manifestations of allergic airway inflammation modulated by DEP were closely related to the immunoglobulin production response to OA, especially with regard to enhanced IgG1 production.

Diesel Exhaust Particles Enhance Airway Responsiveness Following Allergen Exposure in Mice

We have previously reported that intratracheal instillation of diesel exhaust particles (DEP) enhances allergen-induced eosinophilic airway inflammation, local expression of interleukin-5 and granulocyte macrophage-colony stimulating factor, and allergen-specific production of IgE and IgG in mice. The present study was undertaken to elucidate the effects of DEP on airway hyperresponsiveness as another characteristic feature of allergic asthma. The animals were randomized into four experimental groups that received intratracheal instillation with vehicle, ovalbumin (OVA), DEP, or the combination of OVA and DEP on a weekly basis for 6 weeks. Respiratory resistance (Rrs) was measured 24 h after the last instillation. An increase in Rrs in animals that inhaled acetylcholine was significantly greater in the combined treatment with OVA and DEP than in the other treatments. The present study indicates that DEP can enhance airway responsiveness associated with allergen exposure, and provides experimental evidence that DEP may deteriorate the pathophysiology of allergen-related respiratory disease such as allergic asthma.

Diesel Exhaust Inhalation Enhances Airway Hyperresponsiveness in Mice

Background: Repeated intratracheal instillation of diesel exhaust particles and ovalbumin-induced airway hyperresponsiveness and airway inflammation in mice. However, the effects of daily inhalation of diesel exhaust may differ from the effects of direct instillation. Methods: Therefore, mice were exposed to diesel exhaust by inhalation 12 h per day for 3 months. Before the diesel exhaust exposure, ovalbumin was injected intraperitoneally as a sensitization. After 3 weeks of diesel exhaust exposure, these mice were challenged with ovalbumin every 3 week thereafter. Results: Diesel exhaust exposure with antigen challenge induced airway hyperresponsiveness and airway inflammation which was characterized by increased numbers of eosinophils and mast cells in lung tissue. The recruitment of inflammatory cells was accompanied by an increment in goblet cells on bronchial epithelium. Diesel exhaust exposure alone also enhanced airway hyperresponsiveness, but did not induce eosinophilic infiltration and/or an increment in goblet cells. Conclusion: Diesel exhaust inhalation enhanced airway hyperresponsiveness and airway inflammation caused by ovalbumin sensitization in mice.

Comparison of PCDD/F and coplanar PCB concentrations in Japanese human adipose tissue collected in 1970-1971, 1994-1996 and 2000

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and coplanar biphenyls (Co-PCBs) were determined in Japanese human adipose tissues. Temporal trends were assessed by comparing data collected during 1970-1971, 1994-1996 and 2000. Mean TEQ levels of PCDD/Fs in human adipose tissue showed a significant decrease from 31.6 +/- 9.2 pg-TEQ/g fat wt in 1970-1971 to 11.9 +/- 7.4 pg-TEQ/g fat wt in 2000, and coplanar PCBs decreased from 35.4 +/- 21.9 pg-TEQ/g fat wt in 1970-1971 to 15.3 +/- 8.2 pg-TEQ/g fat wt in 2000. However, some PCB congener concentrations did not change during this time. A comparison of data using the latest PCB-TEQ showed no significant changes. Therefore, research on source characterization and monitoring of short-term temporal trends on these compounds should be carried out continuously.

PCDDs and PCDFs in vehicle exhaust particles in Japan

Vehicle exhaust particles from gasoline and diesel engine cars were analyzed for PCDDs and PCDFs. The congener patterns of PCDDs and PCDFs in exhaust particles were different between gasoline and diesel engine cars. Suspended particulate matter from electrostatic precipitator connected to a highway tunnel was also analyzed for PCDDs and PCDFs. The congener pattern of suspended particular matter was different from both of gasoline and diesel engine cars. Total amounts of PCDDs/PCDFs sum concentrations in gasoline, diesel and suspended particulate matter were 0.21, 0.87 and 26.0 ng/g, respectively. The I-TEQs levels in gasoline, diesel and suspended particulate matter were 4.2, 11 and 242 pg/g, respectively.

Immunohistochemical localization of thyroid stimulating hormone induced by a low oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Sprague-Dawley rats.

We have investigated how a low dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects thyroid hormone regulation, especially in relation to the localization of thyroid stimulating hormone (TSH) in the pituitary and that of thyroxin (T4) of the thyroid in the rat. Female Sprague-Dawley rats were given a single oral administration of TCDD ranging from 1.0 to 4.0 microg/kg body weight (bw), and then tissue specimens were removed on day 7 post-administration. Thyroid hormone concentrations were measured in serum, and the expression of the TCDD-responsive genes, UDP-glucuronosyltransferase-1 (UGT1) and cytochrome P4501A1 (CYP1A1) were examined in the liver. TCDD administration resulted in an increase in both immunostaining intensity and the number of TSH-positive cells in the anterior pituitary. T4 was found to localize only in the follicular lumen of the thyroid in vehicle-treated control rats, while TCDD administration caused a foamy change in the colloid of some follicles, an indication of accelerating the biosynthesis of T4 in the thyroid. By morphometrical analysis, the ratio of parenchymal/lumenal area of the thyroid was found to increase in response to TCDD. TCDD treatment as low as 2.0 microg TCDD/kg bw induced a significant decrease in both serum total T4 (TT4) and free T4 (FT4) concentrations in the rats, with a significant increase in serum TSH levels in the 4.0 microg TCDD/kg bw rats. Serum total triiodothyronine (TT3) level was unchanged in all groups. The UGT1 gene was significantly induced at a TCDD dose as low as 1.0 microg/kg bw in a dose-dependent manner. TCDD concentrations in the serum, liver and adipose tissues were detected in a dose-related fashion. The present immunohistochemical results clearly support the earlier biochemical findings on the perturbation of the thyroid-pituitary axis by TCDD and suggest that UGT1 is an immediate target of a low TCDD exposure that triggers the perturbation.

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin alters activity-dependent expression of BDNF mRNA in the neocortex and male rat sexual behavior in adulthood

Dioxin and its related compounds are suspected to cause neurological and nueroendocrinological disruption in human and laboratory animal offspring upon in utero and lactational exposure during growth and development. We tested the hypothesis by utilizing Long-Evans Hooded rats that perinatal exposure to dioxins affects the neocortical function and expression of sexual behavior in adulthood. In the sexual behavior test, perinatal exposure to TCDD significantly reduced the number of mounts and intromissions. The mRNA semi-quantification in in situ hybridization showed that the mating stimulus in control males induced c-fos mRNA expression in the preoptic area (POA) and the brain derived neurotrophic factor (BDNF) mRNA upregulation in the frontal cortex. In contrast, perinatal exposure to TCDD lowered the upregulation of BDNF mRNA in the frontal cortex but not that of c-fos mRNA in the POA. The volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) was not affected. The results suggest that perinatal TCDD affects the neocortical function independently from the brain sexual differentiation and alters the expression of sexual behavior.

Enhancement of antigen-induced eosinophilic inflammation in the airways of mast-cell deficient mice by diesel exhaust particles

The present study was conducted to clarify the involvement of mast cells in the exacerbating effect of diesel exhaust particles (DEP) toward allergic airway inflammation and airway hyperresponsiveness (AHR). Airway inflammation by the infiltration of cosinophils with goblet cell proliferation and AHR, as well as by the production of antigen-specific IgG1 and IgE, in plasma were examined using mast cell-deficient mice (W/W(v)) and normal mice (W/W(+)). Both groups of mice received ovalbumin (OVA) or OVA+DEP intratracheally. The eosinophilic airway inflammation and goblet cell proliferation promoted by OVA were significantly greater in W/W(+) than in W/W(v). A similar result was observed in AHR, but was not significant among both groups of mice. DEP enhanced OVA induced-allergic airway inflammation, goblet cell proliferation, and development of AHR in W/W(v), but not in W/W(+). DEP decreased production of antigen-specific IgG1 and IgE in both groups of mice. Mast cells were observed in the submucosal layer of the main bronchus in W/W(v). The number of mast cells was significantly decreased by OVA treatment. The results indicate that mast cells are not necessary to enhance airway damage and development of AHR in W/W(v) by DEP. However, mast cells may be required for the OVA-induced cosinophilic inflammation, airway damage with goblet cell proliferation, and AHR in W/W(+).