Effects of carbon ion irradiation on inflammatory processes and normal tissue damage in the endothelium and the rat lung

Ionizing radiation is able to elicit an anti-inflammatory, as well as a pro-inflammatory response. The anti-inflammatory effect of low radiation doses is successfully used within the scope of radon therapy to treat chronic inflammatory conditions such as Morbus Bechterew. In contrast, high radiation doses elicit a pro-inflammatory response which plays a role in normal tissue injury occurring after tumor therapy. The mechanisms underlying those differential effects are not fully understood and were investigated in the present thesis. Carbon ions were used for this investigation because on the one hand, carbon ions have physical features similar to the alpha decay of radon, and on the other hand, normal tissue effects occurring after tumor therapy with carbon ions are still subject to investigation. The first part of this thesis addresses the anti-inflammatory response. An important process of the beginning inflammation is the adhesion of leucocytes to the blood vessel wall and their extravasation into the tissue. These processes are mediated by specialized membrane proteins, the adhesion molecules, which are presented on the surface of endothelial cells during inflammation. It was investigated whether E-selectin, ICAM-1 and VCAM-1---three very important adhesion molecules---are downregulated after low-dose carbon ion and X-irradiation of primary endothelial cells, which would point towards an anti-inflammatory effect. For the first time, multiplex flow cytometry was used for these experiments. Although previous experiments demonstrated a reduction of leucocyte adhesion after irradiation, no significant radiation effect on adhesion molecules was found. Accordingly, processes such as clustering of adhesion molecules on the cell surface could play a greater role as previously assumed, or additional factors and adhesion molecules participate in the radiation response. In the second part, the pro-inflammatory effect of ionizing radiation was investigated within the scope of normal tissue complications of the rat lung. Acute pneumonitis, by itself already a severe side effect after irradiation of lung carcinoma, is seen as an elicitor of chronic effects such as lung fibrosis, which can lead to the death of the patient. The study of the effect of new treatment techniques such as the heavy ion therapy on normal tissue damage in the lung shall compare how normal tissue damage is elicited in comparison to other radiation qualities. For this purpose, rats were irradiated with carbon ions under therapy conditions. The measurement of the breathing rate and the histological analysis of the radiation effects compared to the often used proton irradiation have demonstrated that carbon ions elicit the same effects as X-rays or protons, but at a lower physical dose. The relative biological effectiveness is 1.3 for most of the effects, which is in good agreement with studies on other organs. With the help of the herein established and in part refined automated image segmentation it was shown that the number of alveolar macrophages is still increased in the chronic phase of pneumonitis. Interestingly, the increased macrophage numbers are confined to irradiated and thus fibrotic areas, and similar patterns are found in the early phase of pneumonitis. This finding supports the notion that macrophages are contributing to the development of fibrosis directly within fibrotic areas. Profibrotic mechanisms such as epithelial-to-mesenchymal transition or the invasion of fibroblast progenitor cells do not play a role in the chronic phase after exposure to carbon ions.