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二酸化窒素のラットにおよぼす影響 : 肺の過酸化脂質生成とコラーゲン代謝関連因子の変化
https://az.repo.nii.ac.jp/records/3190
https://az.repo.nii.ac.jp/records/3190f4327939-e6c7-451b-9181-bbb6635fc372
| 名前 / ファイル | ライセンス | アクション |
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diss_dv_otsu0226 (18.6 MB)
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diss_dv_otsu0226_jab&rev (266.3 kB)
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diss_dv_otsu0226_jab.pdf (161.6 kB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2013-01-29 | |||||
| タイトル | ||||||
| タイトル | 二酸化窒素のラットにおよぼす影響 : 肺の過酸化脂質生成とコラーゲン代謝関連因子の変化 | |||||
| タイトル | ||||||
| タイトル | A study on biochemical effects of nitrogen dioxide on the rats : alterations of lipid peroxidation and of related factors in collagen matabolism | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者 |
市瀬, 孝道
× 市瀬, 孝道 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 窒素酸化物には多くの種類があるが，環境大気中に存在して，人体影響の面から問題とされているのは，二酸化窒素(NO_2)と一酸化窒素(NO)である。 一酸化窒素は，主として物が高温で燃焼する際，空気中または燃料中の窒素と酸素の反応によって生じ，生成した一酸化窒素が大気中で酸化して二酸化窒素に変化していく。 かつて問題とされた硫黄酸化物は，燃料中の不純物である硫黄分が燃焼過程で酸化するため生成したが，窒素酸化物は，燃料由来というよりは，高温燃焼に伴う空気中の窒素の酸化が主であるため，硫黄酸化物のように工場ボイラー等の固定発生源だけでなく，内燃機関からも生成するため，移動発生源としての自動車，船舶，航空機等からの排ガスも問題とされ，特に，モータリゼーションの普及に伴なう自動車排ガスが大きな社会問題となっている。また，住宅構造の変化に伴って，家庭暖房や厨房，さらには喫煙等も問題とされる場合が生じてきている。 このため，硫黄酸化物をはじめ，他のガス汚染質による汚染は改善されてきているのに，窒素酸化物による汚染状況は，依然として改善されておらず横ばいの状況が続いており，特に自動車排ガスの影響の大きい幹線道路沿いの住民の健康に与える影響が問題となっている。したがって，窒素酸化物と健康影響の関係については，各分野において調査，研究が行われているが，著者は，ラットにNO_2を暴露して，肺において脂質過酸化反応が起こるかどうか，起こった場合の脂質過酸化反応と抗酸化性防禦機構との関係はどうなっているのか明らかにするとともに，肺の線維化に対する二酸化窒素の作用を，肺線維症のモデル実験を含めて脂質過酸化とコラーゲン代謝の面から検討を行った。以下その研究業績の概要について述べる。 1．過酸化脂質の生成と抗酸化性防禦機構との関係 NO_2の急性，亜急性および慢性暴露によるラット肺の過酸化脂質生成と酸化的障害から生体を防禦する肺の抗酸化性防禦機構の変化を経時的に検討し，両者の関連性を調べた。 その結果，高濃度および低濃度のNO_2暴露による過酸化脂質の増加を呼気中エタンと肺ホモジネート中のThiobarbituric acid(TBA)反応性物質量の測定によって明らかにすることができた。 また，その過酸化脂質生成量はNO_2の濃度と暴露期間に依存して増加することが明らかとなった。 つぎに，過酸化脂質の生成とGlutathione Peroxidase(GPx)，Glutathione reductase(GR)，Glucose-6-phosphate dehydrogenase(G6PD)および6-phosphogluconate dehydrogenase(6PGD)活性などの抗酸化性防禦系酵素活性の変化との関係はきわめて対称的であった。すなわち，NO_2暴露初期に過酸化脂質が増加し，その値が最大レベルに達する時期に抗酸化性防禦系が増加しはじめ，逆に抗酸化性防禦系が最大レベルに達する時期には過酸化脂質は対称レベルに戻り，その後，抗酸化性防禦系が徐々に低下すると過酸化脂質は再び増加してくることが判った。 2．パラコート投与による実験的肺線維症の作成 パラコートを投与して実験的に肺線維症を作成し，その発症過程における肺の過酸化脂質生成と抗酸化性防禦系の変化を調べ，NO_2暴露の場合と比較した。その結果，肺の過酸化脂質生成と抗酸化性防禦系の経時変化はNO_2暴露の場合と同様に対称的な変化を示し，パラコートを投与した場合でも，NO_2暴露の場合と同様に，抗酸化性防禦機構は初期の段階で過酸化脂質生成防禦に重要な役割を示すが，パラコート投与の延長に伴って，抗酸化性防禦能が徐々に低下し，逆に過酸化脂質が再びゆるやかに増加するものであることが明らかとなった。 また，パラコート投与による肺の線維化過程では，初期に肺のコラーゲン含量が低下し，その低下は肺の過酸化脂質生成に関与する活性酸素によって肺に存在するコラゲナーゼ阻害因子が不活性化されて肺のコラーゲン分解が促進されて起り，血清ヒドロキシプロリン(HOP)量や尿中HOP比が増加する。その後，過酸化脂質の増加に伴って肺が障害されると，血清中にコラゲナーゼ阻害因子活性が増加し，それに伴って肺でも増加し，結果的に肺でのコラーゲン分解を抑制して血清HOP量や尿中HOP比が低下し，その延長線上でコラーゲン合成とコラーゲン架橋の促進につれて肺の線維化が起こるものであることが明らかとなった。 3．肺の線維化に対するNO_2の作用 高濃度NO_2の急性暴露では，肺の過酸化脂質の増加に伴って肺のコラーゲン合成が促進され肺の線維化が起こり，また，肺胞道や肺胞壁は肥厚する。この時，肺のコラゲナーゼ活性も増加してコラーゲン分解が促進し，血清HOP量も増加する。その後，コラーゲン分解が進み最終的に肺の線維化が認められる時期には，肺胞道や肺胞壁の肥厚は軽度となり，また肺の過酸化脂質量，コラーゲン含量は低下する。しかし，肺のコラゲナーゼ阻害因子活性の急速な増加とコラゲナーゼ活性の低下によつてコラーゲン分解能が低下し，血清や尿中のHOP量が低下する。以上のような経過をへて，肺の線維化が起こるものであることが明らかとなった。また，肺および血清のコラゲナーゼ阻害因子活性の急速な増加が肺の過酸化脂質の増加した直後からみられることは，パラコート投与の場合と類似していた。 低濃度NO_2の長期暴露の場合には，過酸化脂質が一度増加した後減少し，ふたたび増加する時期にコラゲナーゼ阻害因子活性が増加し，コラゲナーゼ様活性が低下することによってコラーゲン分解能が低下し，尿HOP比も低下することが明らかとなった。これらの結果から，低濃度長期暴露の場合には，パラコートと同じようにコラーゲン分解能の低下も肺の線維化を起す要因の一つであることが示唆された。 また，肺の過酸化脂質の増加は肺に障害を引き起こし，それが肝臓でのコラゲナーゼ阻害因子合成を促進し，血清を介して肺にコラゲナーゼ阻害因子が増加するものと推測された。 |
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| Abstract | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Nitrogen dioxide (NO_2) is a common air pollutant from the reaction between nitrogen and oxygen in conbusting process such as boilers of factories and automobile engines. Especially, atmospheric NO_2 concentration in large cities is comparatively high level, most of persons has anxieties about it's health effects. Therefore, to clarify the biological effects of NO_2 on the living body is very important to establish the basis of preventive medicine in life environment. NO_2 is a high oxidizing substance and causes various pathological injury in lungs. Generally, it is considered that peroxidation of membrane lipids causes to effects on cell damages and on many toxic process, and the toxic action of NO_2 may be an result from lipid peroxidation. An evidence that NO_2 exposure causes lipid peroxidation in vivo was shown by Thomas et al. using new method of conjugated diene. Thereafter, many investigators have tried to measure the lipid peroxides in tissues, but, they have failed to measure the lipid peroxides following, exposure to NO_2. In this report the author has established the method to measure these lipid peroxides in tissues. On the other hand, many reports on lung fibrosis caused by exposure to high and low-level of NO_2 have been published. Recently, it has been clarified that active oxygen species concerning with lipids peroxidation causes to an abnormal changes in collagen metabolism. There is, however, no evidence that biochemical changes induced by NO_2 exposure occure to the lung fibrosis. As a step to clarify the biochemical effect of NO_2 exposure on the living body, this study was performed and this study contains of three parts, first is to determine whether lipid peroxidation is caused by exposure to NO_2 or not, second is to clarify the relationship between the changes of lipid peroxidation and the antioxidative protective systems in lungs of rats exposed to NO_2, and third is to examine an experiments on an model of lung fibrosis, and the effects of NO_2 on pulmonary fibrosis was investigated from aspects of lipid peroxidation and collagen metabolism. In the first chapter, lipid peroxides in rats lungs and in whole body were examined to clarify the relationship between the changes of lipid peroxidation and the antioxidative protective system, to which acute, subacute and chronical exposure to NO_2 were performed. Lipid peroxidation measured by ethane exhalation and thiobarbituric acid (TBA) reactive material increased after the exposure to NO_2, and the lipid peroxidation increased dose-dependently, and it changes dependent on the period of NO_2 exposure, but the changes of the antioxidative protective systems is very complex. Activities of antioxidative protective enzymes such as glutathione peroxidase(GPx), glutathione reductase(GR), glucose-6-phosphate dehydrogenase(G6PD), 6-phosphogluconate dehydrogenase(6PGD), disulfide reductase(DSR), and super oxide dismutase(SOD) in the 105,000xg supernatant of lung homogenates decreased slightly at the first days. Thereafter, they increased to their maximum levels from the 5th to 10th day, and their maximum levels were maintained until the 14th day. The time course of non-protein sulfhydryls (NPSH) was similar to that of the antioxidative protective enzymes. The patterns of change in these protective enzymes and NPSH were symmetric to that of lipid peroxidation after the 3rd day. In contrast, the amount of Vitamin E, that is a free-radical scavenger, increased to maximum at the 2nd day, and returned to the initial level. The change of Vitamin E was similar to that of lipid peroxidation. Therefore, vitamin E may be an initial factor to prevent from the peroxidation and it may be transported from other organs, mainly the liver. In subacute experiment, rats were exposed continuously to 0.4, 1.2 and 4 ppm NO_2 for one, two and four months respectively. Lipid peroxidation and the reaction of TBA values increased and are dependent on the NO_2 concentrations, but the increases of these values were slower than that of rats exposed to 10 ppm NO_2 and then these values returned to the initial level. Thereafter, they had a tendency to decrease dependent on the increase of lipid peroxidation. The activities of antioxidative protective enzymes and the contents of NPSH increased at the first week and reached to their maximum levels at the 4th week. And the activities of antioxidative protective enzymes decreased gradually until the 16th week, but the levels of NPSH were maintained until the four months. Changes of antioxidative protective enzymes showed an inverse relationship to that of lipid peroxidation. In chronic experiments, rats were exposed continuously to 0.04, 0.4 and 4 ppm NO_2 for 9, 18 and 27 months respectively. The formation of lipid peroxides increased with higher NO_2 concentrations and exposure period. The lipid peroxidation increased significantly in the 4 ppm NO_2 group of the 9-months and in the 0.4 and 4 ppm NO_2 groups of the 18-months exposure. The activities of antioxidative protective enzymes in lung of rats decreased gradually from 9 months to 18 months, changing inversely the formation of lipid peroxides. An ethane exhalation increased significantly-from the that of control in the 0.04, 0.4 and 4 ppm NO_2 exposure for 9 and 18 months, and a dose response relationship was clearly observed. Furthermore, ethane formation of rats exprosed to 0.04 and 0.4 ppm NO_2 for 27 months also increased to twice of the control level. But after the exposure to 4 ppm NO_2 27 month, the ethane level returned to the control level. In the meanwhile, in a pathological experiment projected at the same with this experiment, the lung fibrosis and the thickness of alveolar wall in lungs of rats exposed to 4 ppm NO_2 for 18 months were observed by Takenaka et all. Furthermore, they observed that the thickness of the alveolar wall decreased than that of rats exposed to 4 ppm NO_2 for 18 months, and the lung fibrosis progressed than that of rats for 18 months-exposure these facts show that, the lung fibrosis gradually progresses following the increase of lipid hydroperoxides and prolongation of the NO_2 exposure period, and, when lung fibrosis was formed finally, the amount of exhaled ethan of rats exposed to 4 ppm NO_2 27 months decrease, this shows that the decrease of lipid peroxides did not recovery signal to the normal state of lungs. Therefore, the lung fibrosis may relate to the formation of lipid peroxides. These results showed that the ability of the antioxidative protective systems to protect cell from oxidative damage increasing in the early time, and then they decreased gradually. On the other hand, lipid peroxides increased temporaly in the early time, but they returned to the control level. Thereafter, they increased gradually, again. It was confirmed that the forming process of cytotoxic lipid peroxides altered inversely with the protective system. This supposed that lung disease would be caused, as a balance of lipid peroxidation and the ability of the antioxidative protective systems exceeds a limit of homeostasis. In the second chapter, using paraquat(1, 1-dimethyl-4, -4'-dipyridylium dichloride, MV, PQ), a simulation experiment was performed to investigate the mechanism of lung fibrosis. PQ is widely used in agriculture and it has been well known to cause severe interstitial pneumonia and fibrosis in human and animal, and to forming lipid peroxides. An experimental model of lung fibrosis in rats was induced by following intra-peritoneal injection of PQ. The relationship between the changes of lipid peroxidation and the antioxidative protective system in lungs during the time course was investigated and the development of PQ-induced lung fibrosis was compared with the results obtained by exposure to NO_2. And the relationship between collagen metabolism related factors in the course of development of lung fibrosis and lipid peroxidation were examined. It was clarifed that the time-dipendent changes of lipid peroxidation and the antioxidative protective systems in lungs varied inversly as well as the changes observed by exposure to NO_2. It was found that the antioxidative protective enzymes such as G6PD, 6PGD and NPSH in lungs were inducted to protect cell from lipid peroxides increased in early time of PQ i.p. and when they increased to the maximum level, lipid peroxides returned to control level, thereafter the antioxidative protective enzymes and the NPSH decreased gradually with a time course of administration of PQ and the lipid peroxidation increased inversely to the antioxidative protective system. The antioxidative protective ability against lipid peroxide was temporary action. Furthermore, that lung fibrosis progressed by abnormal change of collagen metabolism related to lipid peroxidation in the developmental course of PQ-induced lung fibrosis. On the other hand, it have been known that superoxide anion radical (O^・-_2) participate with lipid peroxidation enhanced collagen synthesis. The transformation of superoxide radical was supported by the increase of superoxide dismutase activity in lungs PQ-treated rats. It suggests indirectly that collagen synthesis in lungs of rats administrated PQ, was enhanced. The activities of lung's and serum's collagenase inhibitor, which inactivate collagenase, decreased in the early time. At this time, a significant negative relationship between lipid peroxides and collagenase inhibitor activity in lungs was observed, but the decreasing-time of collagenase inhibitor activity in lungs was earlier than the increasing-time of lipid peroxides in an early time. These results suggests that the decline of collagenase inhibitor activity was inactivated by reactive oxygen species, which concerns with lipid peroxidation, and that the decline of collagenase inhibitor activity in serum was due to inactivation of collagenase injhibitor in lungs. The decline of collagenase inhibitor activity like this promotes to the collagen decomposition in lungs in an early time, at the same time the hydroxyproline excreted to serum by collagen decomposition and the urinary hydroxyproline:creatinine ratio (HOP ratio) increased. The fact that the decline of collagenase inhibitor activity in lungs promote collagen decomposition in lungs was supported by this result, that is a significant negative relationship between the collagenase inhibitor activity in lungs and the hydroxyproline content in serum, was observed. Thereafter the collagenase inhibitor activity in serum rapidly increased after the increase of lipid peroxides in lungs , but the increase of collagenase inhibitor activity in lungs was less than that in serum. As for the reason, it was supposed that the collagenase inhibitor was inactivated by reactive oxygen species or was neutralized by their proteases, causing increase of proteolytic enzymes at an inflammation. When the increment of collagenase inhibitor activities in lungs and serum was observed, the amount of hydroxyproline in serum and the urinary HOP ratio decreased inversely against the change observed in the early time, and the collagen content in lungs increased gradually. The activity of monoamine oxidase (MAO) concerning with formation of cross-link of collagen increased, and interstitial pneumonia and lung fibrosis were confirmed by morphological observation. These results suggested that PQ-induced lung fibrosis was caused by suppression of collagen decomposition on account of the increase of collagenase inhibitor actibity in lungs, associated with the rapid increase of collagenase inhibitor in serum, and by a promotion of collagenase synthesis and cross-link of collagen. The increase of collagenase inhibitor activity in serum after the increase of lipid peroxide in lungs was due to the promotion of synthesis of collagenase inhibitor in liver, becouse of that increment is due to nutralized collagenase and proteolytic enzymes increased by inflammation, that is coused by lipid peroxide-induced injury. As a result of the increase of lung collagenase inhibitor activity, a degradation in lung collagen is suppressed, and that cause to lung fibrosis. In the third chapter, to clarify the effects of NO_2 on the lung fibrosis and the alteration in related factors of collagen metabolism in rats exposed acutely and chronically to NO_2 was examined, comparing with the results of PQ administrated rats. In this experiment, lung fibrosis was observed at the 7th and 14th day by morphological observation, but thicking of the wall of the alveolar duct and adjacent alveoli at the 14th day was slightly thinner than at 7th day. This fact suggested that the lipid peroxide and the collagen in lungs increased in the wall of the alveolar duct and alveoli at the 7th day. On the other hand, when the collagen content in lungs increased, collagenolytic enzymes and serum HOP increased too. Thereafter the collagenolytic enzymes, the hydroxyproline content in serum and the urinary HOP ratio decreased than that of control level and a significant relationship between the collagenolytic enzymes activities in lungs and the hydroxyproline contents in serum was observed. These results suggest that the collagen synthesis and decomposition were promoted in lungs. The time-dependent changes of the collagenase inhibitor activities in lungs and in serum showed a similar pattern to that of the collagenase inhibitor activities observed in PQ administrated rats. This increment of the collagenase inhibitor activities was induced to protect lung tissue from decomposing confusely by collagenase and protease increasing by inflammation. When the collagenase inhibitor activity in lungs decreased, a significant negative relationship between the lipid peroxides and the collagenase inhibitor activity in lungs was observed as well as that observed in PQ administrated rats. But there was no evidence that the collagen decomposition was promoted by the decrease of the collagenase inhibitor activity in lungs. This result was different from that observed in PQ administrated rats. The activity of MAO in lungs participating with the formation of cross-link of collagen increased rapidly from the first day to the 4th day, at the same time, a siginificant relationship between the lipid peroxides and the MAO activity was observed. This results suggest that the formation of cross-link of collagen was promoted by MAO, that was activated by the lipid peroxidation. These changes in enzymes cause to the thickening of the wall of the alveolar duct and alveoli slightly. In chronic experiment, the collagen contents in lungs increased in 4 ppm NO_2 exposure group, and the urinary HOP ratio was decreased with NO_2 concentratons higher. The MAO and amounts of the lipid peroxides in lungs increased dose-dependently to the concentration of NO_2. These results show clearly that the collagen content in lungs increased in the 4 ppm NO_2 group, in which the ability of collagen decomposition decreased exceedingly, and this is in agreement with the results of the morphological observation, and lung fibrosis was observed in the 4 ppm NO_2 group. It suggests that decline of the ability of the collagen decomposition is also a factor to occur lung fibrosis in long-term exposure to NO_2 as well as PQ treated rats. We must pay attentions to the decrease of the urinary HOP ratio from an aspect of lung fibrosis. On the other hand, the increase of urinary HOP ratio may occur by the decrease of the collagenase inhibitor activity that continues for a long-term, that is a factor to induce pulmonary emphysema. Therfore, to investigate the changes of collagenase inhibitor activity is very important in epidemiological study. If we can show cleary and experimentally the causes of the increase and the decrease of the collagenase inhibitor activity by comparative long-term exposure to some air pollutants, we may be able to understand more exactly the meaning of the increase of the urinary HOP ratio. From these results, the author clarified the formation of lipid peroxides and a role of the antioxidative protective systems to lipid peroxide, that induces cell damage, and the effect of NO_2 on the lung fibrosis, from the aspects of lipid peroxidation and collagen metabolism. |
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| 学位名 | ||||||
| 学位名 | 獣医学博士 | |||||
| 学位授与機関 | ||||||
| 学位授与機関名 | 麻布大学 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 1985-06-12 | |||||
| 学位授与番号 | ||||||
| 学位授与番号 | 乙第226号 | |||||
| 著者版フラグ | ||||||
| 出版タイプ | AM | |||||
| 出版タイプResource | http://purl.org/coar/version/c_ab4af688f83e57aa | |||||
