Auswirkung der Nitrierung von Allergenen auf die Ausprägung des allergischen Asthmas unter Einbeziehung des Antioxidantien-Metabolismus
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Philipps-Universität Marburg
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Allergic diseases have increased in prevalence worldwide during the last few decades and are now a global burden that affects people of all ages and ethnic backgrounds. Due to growing medical, social and economic problems, it is becoming increasingly necessary to gain a better understanding of this subject. The search for explanations for the observed increase in allergic disorders has generated the ‘environmental hypothesis’, which suggests that inhaled air pollutants are responsible for the increase in prevalence. In addition to their inflammatory and sensitizing effects on the airway epithelia, air pollutants are also capable of modifying airborne proteins. Recent investigations have shown that tyrosine residues of various proteins are efficiently nitrated by polluted urban air, and that this post-translational modification can alter their immunogenicity and allergenicity.During respiration, the lung is directly exposed to atmospheric air pollutants that can reach the terminal lung tissue. Therefore, alterations of lung structure and function can be expected. Furthermore, other important targets for air pollutants are the pulmonary surfactant system as well as the respiratory tract antioxidant capacity.
This study analyzes the influence of protein nitration on different structural, biochemical and biomolecular parameters of asthma and allergic disease using nitrated and unmodified samples of the food allergen ovalbumin (OVA) and the metalloprotein keyhole limpet hemocyanin (KLH). All experiments were done on C57BL/6 mice, which were intra-peritoneally sensitized and inhalatively challenged with either PBS, (n)OVA or (n)KLH. Methacholine responsiveness was measured using the FlexiVent® system to assess AHR, subsequently followed by the histological analysis of the lung ex situ (hematoxylin and eosin stain, immunohistochemical analysis of CuZnSOD and MnSOD). Plasma and bronchoalveolar lavage fluid (BALF) were collected and type II pneumocytes isolated. The plasma was used for the detection of total SOD activity. The BALF was centrifuged, the supernatant used for the measurement of total protein and total phospholipid, and the cell pellet re-suspended for differential cell counts on cytospins (May-Grünwald/Giemsa stain). Using real time RT-PCR the isolated type II pneumocytes were analyzed regarding their mRNA levels of phospholipide-synthesizing enzymes (choline kinase α and β, CTP:Phosphocholine Cytidylyltransferase α) and antioxidative enzymes of the SOD-subunits (CuZnSOD, MnSOD, ECSOD). In addition, western immunoblots were performed for the detection of MnSOD protein within type II cells.
The comparison of the OVA/OVA and nOVA/nOVA groups have answered the question: “Do nitrated allergens induce a more pronounced inflammatory response in a whole individual than the unmodified proteins?” The results of this study showed that the histological changes in the form of structural lesions and cellular infiltrations were far more distinct in the nitrated group than in the unmodified group. Both demonstrated a significant influx of lymphocytes, eosinophils and neutrophils with higher numbers in the nOVA/nOVA group. Moreover, the latter showed a higher increase in total protein in the BALF, which can be interpreted as impaired integrity and permeability of the bronchial epithelia. No inter-group differences were seen in the investigations concerning pulmonary lung function, the amount of total phospholipid and phospholipid synthesizing enzymes, as well as the expression of superoxide dismutases.
To answer the second main question of this study: “Is an individual, after being sensitized against a well-defined nitrated allergen, also responsive to another nitrated allergen of different origin?” nOVA/nKLH was compared to nOVA/KLH and PBS/nKLH which served as control groups. The investigation of the nOVA/nKLH group revealed inflammatory alterations in both histology and cytology, whereas the lungs of control mice showed no pathological changes. More intergroup differences were seen in the amounts of total protein in the BALF and of MnSOD mRNA in type II pneumocytes. The nOVA/nKLH treated mice showed slightly elevated levels of total protein whereas their MnSOD mRNA was somewhat reduced. Apart from these insignificant differences the remaining results were consistent with the control animals.
This work has contributed to the understanding of some biochemical and molecular mechanisms in the immune response to nitrated and unmodified allergens. Collectively, these observations suggest that the environmental nitration of allergens enhances their allergenic potential and that an individual, after being sensitized against a well-defined nitrated allergen, develops a tendency to respond against another nitrated allergen of different origin. These findings could be an explanation for the increased prevalence of allergies and allergic asthma, especially in polluted urban environments.
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Created: 2012Issued: 2012-10-05Updated: 2012-10-05
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
ger
Data types
DoctoralThesis
Keywords
Surfactant factorAllergic asthmaProtein nitrationType II pneumocytesProteinnitrierungSuperoxide dimutaseTyp-II-Pneumozyten
DFG-subjects
Surfactant-FaktorAllergisches AsthmaSuperoxiddismutasen
DDC-Numbers
610
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Wege, Cordula: Auswirkung der Nitrierung von Allergenen auf die Ausprägung des allergischen Asthmas unter Einbeziehung des Antioxidantien-Metabolismus. : Philipps-Universität Marburg 2012-10-05. DOI: https://doi.org/10.17192/z2012.0848.
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This item has been published with the following license: In Copyright