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M Sagai

Publications and source records attributed to M Sagai.

At least 55 records · Page 3Linked to original sources
PubMed1998

Murine strain differences in airway inflammation caused by diesel exhaust particles.

To elucidate whether immunoglobulin (Ig) E or IgG are involved in the murine asthma model, we compared the pathogenic features of mice that were high IgG responders (C3H/He) with mice that were high IgE responders (BALB/c) after intratracheal instillation of diesel exhaust particles (DEP) and ovalbumin sensitization. Both mouse strains received DEP intratracheally once a week for 5 weeks. After the second injection of DEP, ovalbumin and aluminium hydroxide were injected intraperitoneally. After the last DEP administration, the mice were challenged by exposure to an aerosol of ovalbumin. DEP caused increased IgG1 production and airway hyperresponsiveness after ovalbumin sensitization in C3H/He mice, although IgE production did not change in either strain. Furthermore, in C3H/He mice, the number of eosinophils and goblet cells in the bronchial epithelium, and the expression of interleukin-5 and interleukin-2 were increased by DEP and ovalbumin treatments. In contrast, the pathogenic changes in BALB/c mice were weak, even though the same protocol was used. In conclusion, murine strain differences in response to air pollutants and allergens seem to be related to antigen-specific immunoglobulin G1 production and cytokine expression in the lungs.

Aerosols↗
PubMed1998

Complement activation by diesel exhaust particles (DEP).

The effect of diesel exhaust particles (DEP) on the hemolytic activity of human serum complement was investigated. Previous treatment of human serum with DEP extracts at 37 degrees C decreased the hemolytic activity of human serum complement dose dependently, to 20% of its original value. This decrease in complement activity by DEP extracts was observed with previous incubation at 37 degrees C but not at 4 degrees C. A decrease in complement activity was observed after previous incubation at 37 degrees C in the presence of EGTA/Mg but not in the presence of EDTA, indicating that the alternative pathway of the complement system had been activated by DEP extracts. Activation of the complement system by DEP extracts was further demonstrated by observation of the cleavage of the third component of the complement (C3) in serum to C3b with immunoelectrophoresis using goat anti-human C3 antiserum. This cleavage of C3 was similarly observed in the presence of EGTA/Mg, indicating the activation of the alternative pathway of the complement system by DEP extracts. These results indicate that DEP can activate the alternative pathway of the complement system, resulting in a decrease in the hemolytic activity of complement and in the production of biologically active degradation products of complement proteins such as C3a. The biological significance of the activation of the complement by DEP in the alveolus is discussed in relation to the influx of neutrophiles.

Animals↗
PubMed1998

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.

Acetylcholine↗
PubMed1998

Oral administration of L-arginine potentiates allergen-induced airway inflammation and expression of interleukin-5 in mice.

The role of nitric oxide in the airway hyperresponsiveness and inflammation of bronchial asthma has not yet been established. However, L-arginine, the substrate for nitric oxide synthases, reportedly alleviates airway hyperresponsiveness caused by parainfluenza virus and reduces granulocytic inflammation induced by ischemia-reperfusion. We investigated the effects of L-arginine on a murine model of allergic asthma that included airway hyperresponsiveness, eosinophilic inflammation and expression of interleukin (IL)-5 in the lung. The mice received drinking water with or without L-arginine for 9 weeks. Histologic evaluation and cellular profiles in bronchoalveolar lavage fluid showed that p.o. administration of L-arginine (72 micromol/kg/day) significantly enhanced eosinophilic airway inflammation and goblet cell proliferation that were associated with intratracheal instillation of ovalbumin. L-Arginine also increased protein levels of IL-5 and IL-2 in supernatants from the lung exposed to ovalbumin. The number of eosinophils in bronchoalveolar lavage fluid correlated significantly with the expression of IL-5. L-Arginine did not reverse ovalbumin-associated airway hyperresponsiveness to inhaled ACh. These results suggest that p.o. administration of L-arginine aggravates allergen-induced eosinophilic airway inflammation via expression of IL-5, and in this model it does not show therapeutic efficacy against airway hyperresponsiveness associated with allergen exposure. Oral administration of L-arginine, the precursor of nitric oxide, may not be an effective intervention in allergic asthma.

Animals↗
PubMed1998

Diesel exhaust particles block induction of oral tolerance in mice.

We investigated the effect of diesel exhaust particles (DEP) on oral tolerance. Oral tolerance was induced by feeding mice with 10 mg of hen egg lysozyme (HEL) daily over a period of 5 days before immunization with the antigen. Varying doses of DEP were orally administered immediately before each feeding of HEL. The results showed that oral administration of HEL significantly suppressed production of anti-HEL IgG, IgG1 and IgG2a antibodies, delayed-type hypersensitivity and proliferative responses of lymph node cells to the antigen. The suppression of these immune responses to HEL by the oral antigen was associated with a marked decrease in secretion of interferon-gamma and interleukin-4 from the lymphoid cells. Administration of DEP dose-dependently blocked suppression by oral HEL of antigen-specific IgG, IgG1 and IgG2a antibody production, delayed-type hypersensitivity and lymphoid cell proliferation. The suppression by the fed antigen of secretion of interferon-gamma and interleukin-4 was also markedly diminished by the particles. Thus, DEP appear to be effective in blocking induction of oral tolerance.

Adjuvants, Immunologic↗
PubMed1997

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.

Animals↗
PubMed1997

Generation of reactive oxygen species during interaction of diesel exhaust particle components with NADPH-cytochrome P450 reductase and involvement of the bioactivation in the DNA damage.

Since the toxicity of diesel exhaust particles (DEP) after intratracheal injection, was suppressed by pretreatment with superoxide dismutase (SOD) modified with polyethylene glycol (Sagai et al. Free Rad. Biol. Med. 14: 37-47; 1993), the possibility that superoxide could be enzymatically and continuously generated from diesel exhaust particles (DEP), was examined. Nicotinamide-adenine dinucleotide phosphate, reduced (NADPH) oxidation was stimulated during interaction of a methanol extract of DEP with the Triton N-101 treated microsomal preparation of mouse lung whereas the cytosolic fraction was less active, suggesting that DEP contains substrates for NADPH-cytochrome P450 reductase (EC 1.6.2.4, P450 reductase) rather than DT-diaphorase. When purified P450 reductase was used as the enzyme source, the turnover value was enhanced approximately 260-fold. Quinones appeared to be served as substrate for P450 reductase because reaction was inhibited by addition of glutathione (GSH) to form those GSH adduct or pretreatment with NaBH4 to reduce those to the hydroxy compounds although a possibility of nitroarenes as the alternative substrates cannot be excluded. A methanol extract of DEP (37.5 micrograms) caused a significant formation of superoxide (3240 nmol/min/mg protein) in the presence of P450 reductase. Electron spin resonance (ESR) experiments revealed that hydroxyl radical was formed as well. The reactive species generated by DEP in the presence of P450 reductase caused DNA scission which was reduced in the presence of superoxide dismutase (SOD), catalase, or hydroxyl radical scavenging agents. Taken together, these results indicate that DEP components, probably quinoid or nitroaromatic structures, that appear to promote DNA damage through the redox cycling based generation of superoxide.

Animals↗
PubMed1997

Lung carcinogenesis and formation of 8-hydroxy-deoxyguanosine in mice by diesel exhaust particles.

In order to clarify the involvement of oxygen radicals in lung carcinogenesis induced by diesel exhaust particles (DEP), the relationship between lung tumour response and formation of 8-hydroxydeoxyguanosine (8-OHdG) in lung DNA was examined. The role of high dietary fat and beta-carotene on these responses was also studied. Mice were intratracheally injected with 0.05, 0.1 and 0.2 mg of DEP per animal once weekly for 10 weeks. After 12 months, the lung tumour incidence in mice treated with 0.05 mg and 0.1 mg showed similar increases (30% and 31%), but was decreased to 24% at 0.2 mg. High dietary fat enhanced the incidence of both benign and malignant tumours. beta-carotene partially prevented the tumour development. After the 10 weekly treatments of DEP, inflammatory reaction was observed in the respiratory tract and alveoli. The formation of 8-OHdG in lung DNA from mice treated with DEP showed a dose dependent increase. 8-OHdG formation was enhanced by high dietary fat and partially reduced by beta-carotene. Formation of 8-OHdG was significantly correlated with the lung tumour incidence except at 0.2 mg. These results suggest that the induction of oxidative DNA damage may be an important factor in the initiation of DEP-induced lung carcinogenesis, and that beta-carotene and high dietary fat may play a role in the regulation of tumour development via modulation of the formation of 8-OHdG.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1997

Diesel exhaust particles enhance antigen-induced airway inflammation and local cytokine expression in mice.

Previous experimental studies have suggested that nasal instillation of diesel exhaust particles (DEP) can enhance nasal IgE response and cytokine production. However, there is no experimental evidence for the relation of DEP to allergic asthma. We investigated the effects of DEP inoculated intratracheally on antigen-induced airway inflammation, local expression of cytokine proteins, and antigen-specific immunoglobulin production in mice. DEP aggravated ovalbumin-induced airway inflammation characterized by infiltration of eosinophils and lymphocytes and an increase in goblet cells in bronchial epithelium. DEP with antigen markedly increased interleukin-5 (IL-5) protein levels in lung tissue and bronchoalveolar lavage supernatants compared with either antigen or DEP alone. The combination of DEP and antigen induced significant increases in local expression of IL-4, granulocyte macrophage-colony stimulating factor (GM-CSF), and IL-2, whereas expression of interferon-gamma was not affected. In addition, DEP exhibited adjuvant activity for the antigen-specific production of IgG and IgE. These results provide the first experimental evidence that DEP can enhance the manifestations of allergic asthma. The enhancement may be mediated mainly by the increased local expression of IL-5, and also by the modulated expression of IL-4, GM-CSF, and IL-2.

Animals↗
PubMed1996

Inhibition of catalase activity in vitro by diesel exhaust particles.

The effect of diesel exhaust particles (DEP) on the activity of catalase, an intracellular antioxidant, was investigated because H2O2 is a cytotoxic oxidant, and catalase released from alveolar cells is an important antioxidant in the epithelial lining fluid in the lung. DEP inhibited the activity of bovine liver catalase dose-dependently, to 25-30% of its original value. The inhibition of catalase by DEP was observed only in the presence of anions such as Cl-,Br-, or thiocyanate. Other anions, such as CH3COO- or SO4-, and cations such as K+, Na+, Mg2+, or Fe2+, did not affect the activity of catalase, even in the presence of DEP extract. Catalase from guinea pig alveolar cells and catalase from red blood cells were also inhibited by DEP extracts, as was catalase from bovine liver. These results suggest that DEP taken up in the lung and located on alveolar spaces might cause cell injury by inhibiting the activity of catalase in epithelial lining fluid, enhancing the toxicity of H2O2 generated from cells in addition to that of O2- generated by the chemical reaction of DEP with oxygen.

Animals↗
PubMed1996

Endothelial-constitutive nitric oxide synthase exists in airways and diesel exhaust particles inhibit the effect of nitric oxide.

Diesel exhaust particles (DEP) are an important cause of air pollution and are thought to be responsible for some respiratory ailments, but the exact mechanism is not known. We evaluated whether DEP inhibit nitric oxide (NO) synthesis in bronchi as NO is present in the exhaled air and has a physiological role in the respiratory tract. Aortic rings were also examined for comparison. We observed that acetylcholine (ACh) induced contraction of the bronchi was partially attenuated by the simultaneous release of NO. When bronchial rings were incubated either with NG-methyl-L-arginine (L-NMA): an inhibitor of NO synthase (NOS) or with DEP, the contraction to ACh was abolished. The source of the NOS was the bronchial epithelium and this endothelial-constitutive NOS was demonstrated by immunohistochemistry. DEP like L-NMA inhibited the ACh induced endothelium dependent relaxation in the aortic rings. The inhibition of NO release by DEP and L-NMA from bronchial and aortic rings was also confirmed by a selective NO electrode. We conclude that inhibition of NO availability by DEP may in part be responsible for the adverse respiratory effects seen by inhalation of these particles in polluted air.

Acetylcholine↗
PubMed1996

Biological effects of diesel exhaust particles (DEP). III. Pathogenesis of asthma like symptoms in mice.

Chronic airway inflammation, mucus hypersecretion, reversible airway constriction, and bronchial hyperresponsiveness are important pathogenic features of asthma. We found that diesel exhaust particles (DEP) instilled intratracheally and repeatedly to mice (once/week for 16 weeks) caused marked infiltration of inflammatory cells, proliferation of goblet cells, increased mucus secretion, respiratory resistance, and airway constriction. Eosinophils in the submucosa of the proximal bronchi and medium bronchioles increased eightfold following instillation. Eosinophil infiltration was significantly suppressed by pretreatment with polyethyleneglycol-conjugated superoxide dismutase (PEG-SOD). Bound sialic acid concentrations in bronchial alveolar lavage fluids, an index of mucus secretion, increased with DEP, but were suppressed by pretreatment with PEG-SOD. Goblet cell hyperplasia, airway narrowing, and airway constriction also were observed with DEP. Respiratory resistance in the DEP-group to acetylcholine was 11 times higher than in controls, and the increased resistance was significantly suppressed by PEG-SOD pretreatment. These findings suggest that DEP and/or oxygen radicals derived from DEP cause bronchial asthma in mice.

Animals↗
PubMed1996

Immunohistochemical localization of surfactant protein A in N-bis (2-hydroxypropyl) nitrosamine-induced lung tumors in rats.

Surfactant protein A (SP-A) is most abundant protein associated with pulmonary surfactant which is synthesized by alveolar type II cells in the alveoli. In this study, we localized SP-A in experimentally induced pulmonary hyperplasias and tumors in rats, by immunohistochemistry. When rats were given a single intraperitoneal injection of N-bis (2-hydroxypropyl) nitrosamine (BHPN) followed by exposed to mixture gases of O3 and NO2, hyperplastic alveolar type II cells stained with the antibody against SP-A were located in the alveolar walls near the alveolar ducts. Adenomas and adenocarcinomas were stained with the anti-SP-A antibody in the lung parenchyma. These immunohistochemical findings suggested that the lung tumors induced in rats treated with BHPN and additionally exposed to mixture gases of O3 and NO2 are derived from mainly alveolar type II cells.

Animals↗
PubMed1995

Biological effects of diesel exhaust particles (DEP). II. Acute toxicity of DEP introduced into lung by intratracheal instillation.

Histopathological examination and cytological analyses in bronchial alveolar lavage fluids (BALF) were performed to clarify the acute toxicity of diesel exhaust particles (DEP) introduced into the lung of ICR mice by intratracheal instillation. Activated charcoal (Norit) was intratracheally administered as a control for non-oedemagenic carbon particles. After administration of two doses (0.4 mg or 0.8 mg per mouse) of DEP, lung water contents increased with instillation dose and with time and increased 1.9 and 2.7-fold, respectively, compared to control animals 24 h after the administration of DEP. In contrast, the instillation of Norit had no effect on the increase in water contents. An inflammatory response in lungs was observed by an increase of inflammatory cells in BALF from mice instilled with DEP. The degree of increase in neutrophils of BALF from mice treated with DEP was much greater than in mice treated with Norit. An intense color of MB-pigment, which showed the extent and degree of endothelial cell injury, was found up to 4 h after administration of DEP. Histopathologically, the disruption of capillary endothelial cells, the detachment from their basement membrane and necrosis, disruption and desquamation of type I pneumocytes were observed, 6 h after the injection of DEP, by electron microscopy. An influx of neutrophils into alveoli, intra-alveolar hemorrhage, perivascular oedema and bronchiolar cell hypertrophy were detected between 18 and 24 h after DEP administration. However, the magnitude of these appearances was greater in mice treated with 0.8 mg of DEP than in mice treated with 0.4 mg. The administration of Norit caused an increase of alveolar macrophages and slight infiltration of neutrophils into the alveolar air spaces and alveolar septa in the animals and had no effects on the bronchioles. These results may suggest that damage of capillary endothelial cells and type I pneumocytes are the earliest changes of lung toxicities by DEP and these cell injuries lead to alveolar oedema and the subsequent inflammatory response.

Analysis of Variance↗
PubMed1995

Apparent inhibition of superoxide dismutase activity in vitro by diesel exhaust particles.

The inhibitory effects of diesel exhaust particles (DEP) on superoxide dismutase (SOD) activity were examined in vitro because intratracheal administration of DEP to mice resulted in a suppression of the pulmonary enzyme activity (Sagai et al., Free Radic. Biol. Med. 14:37-47; 1993). Superoxide production, based on the reduction of cytochrome c, was suppressed considerably by the soluble fraction of mouse lung and by purified SOD from bovine erythrocytes, but the suppression was drastically diminished in the presence of methanol-extractable compounds of DEP. Inhibition of SOD by diethyldithiocarbamate was irreversible, but that by 1,2-naphthoquinone (1,2-NQ) and the methanol extract of DEP was removed by dialysis. Inhibition of superoxide mediated cytochrome c reduction by Tiron, a scavenging agent for superoxide, was blocked by the methanol extract and 1,2-NQ in a concentration-dependent manner. In contrast, addition of a large amount of SOD to the reaction mixture resulted in an almost complete disappearance of inhibitory action of not only 1,2-NQ but also the methanol extract. The existence of carbonyl compounds in the DEP was confirmed by thin-layer chromatography (TLC) with 2,4-dinitrophenylhydrazine reagent. Electron spin resonance (ESR) spectra of an incubation mixture of oxidized 1,2-dihydroxynaphthalene in the absence and presence of cytochrome c indicated a reaction between the semiquinone radical of 1,2-NQ and cytochrome c. These results indicate that the apparent reduction in SOD activity by DEP is due to the chemical reaction of superoxide with components like quinones, which reduce levels of superoxide.

Animals↗
PubMed1995

Formation of an oxidative DNA damage, 8-hydroxydeoxyguanosine, in mouse lung DNA after intratracheal instillation of diesel exhaust particles and effects of high dietary fat and beta-carotene on this process.

Diesel exhaust particles (DEP) cause tumors in the respiratory tracts of experimental animals. It was previously shown that DEP produced superoxide and hydroxyl radical. To examine whether oxygen radicals are involved in mouse lung tumorigenesis induced by DEP, formation of an oxidative DNA damage, 8-hydroxydeoxyguanosine (oh8dG), by DEP was investigated. Furthermore, the role of high dietary fat and beta-carotene on this process was studied. After intratracheal instillation of DEP, a significant increase of oh8dG in mouse lung DNA was observed. High dietary fat enhanced the formation of oh8dG in lung DNA. Intake of beta-carotene suppressed the formation of oh8dG in lung DNA, but the protective effect of beta-carotene against this process was not statistically significant. These results suggest that formation of oh8dG in lung DNA was induced by oxygen free radicals produced by DEP. Thus, it is possible that oh8dG is a promutagenic lesion in DEP-induced lung tumorigenesis in mice and high dietary fat enhances this process through the generation of oh8dG in mouse lung DNA.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1995

Oxidative modification of low density lipoprotein by diesel exhaust particles.

Oxidized low density lipoprotein (LDL) has a variety of hazardous influences on biological systems. Oxidative modification of LDL by diesel exhaust particles (DEP) was studied in vitro to assess its in vivo health effects. DEP suspensions (1, 10 and 100 micrograms/ml) were incubated for 1 h with LDL (1 mg protein/ml) at 37 degrees C. Conjugated diene formation and negative charges in LDL were increased by DEP-treatment in a dose-dependent manner. When native LDL and DEP-treated LDL (DEP-LDL) were incubated for 18 h with macrophage, J774A.1 cell at 37 degrees C, significantly more DEP-LDL was taken up into cells than native LDL. Accumulation of cholesterol ester in cells incubated with DEP-LDL was 4 to 8 times higher than that with native LDL while there was no significant difference between them in free cholesterol content. Incubation (18 h) of J774A.1 with DEP-LDL caused an increase in leakage of lactate dehydrogenase from cells in a DEP-concentration dependent manner, but the incubation with native LDL or DEP per se did not increase the leakage except at the highest concentration of DEP. These results suggest that DEP oxidatively modified LDL giving it cytotoxic, inflammatory and atherogenic properties characteristic of so-called oxidized LDL; these initial modifications of LDL may be one of the underlying mechanisms for diseases associated with DEP.

Animals↗