Long-Term Alterations of Cytokines and Growth Factors Expression in Irradiated Tissues and Relation with Histological Severity Scoring

PURPOSE: Beside its efficacy in cancer treatment, radiotherapy induces degeneration of healthy tissues within the irradiated area. The aim of this study was to analyze the variations of proinflammatory (IL-1α, IL-2, IL-6, TNF-α, IFN-γ), profibrotic (TGF-β1), proangiogneic (VEGF) and stem cell mobilizing (GM-CSF) cytokines and growth factors in an animal model of radiation-induced tissue degeneration. MATERIALS AND METHODS: 24 rats were irradiated unilaterally on the hindlimb at a monodose of 30 Gy. Six weeks (n=8), 6 months (n=8) and 1 year (n=8) after irradiation the mediators expression in skin and muscle were analyzed using Western blot and the Bio-Plex® protein array (BPA) technology. Additional histological severity for fibrosis, inflammation, vascularity and cellularity alterations scoring was defined from histology and immnunohistochemistry analyses. RESULTS: A significant increase of histological severity scoring was found in irradiated tissue. Skin tissues were more radio-sensitive than muscle. A high level of TGF-β1 expression was found throughout the study and a significant relation was evidenced between TGF-β1 expression and fibrosis scoring. Irradiated tissue showed a chronic inflammation (IL-2 and TNF-α significantly increased). Moreover a persistent expression of GM-CSF and VEGF was found in all irradiated tissues. The vascular score was related to TGF-β1 expression and the cellular alterations score was significantly related with the level of IL-2, VEGF and GM-CSF. CONCLUSION: The results achieved in the present study underline the complexity and multiplicity of radio-induced alterations of cytokine network. It offers many perspectives of development, for the comprehension of the mechanisms of late injuries or for the histological and molecular evaluation of the mode of action and the efficacy of rehabilitation techniques

Time-Course of Hypothalamic-Pituitary-Adrenal Axis Activity and Inflammation in Juvenile Rat Brain After Cranial Irradiation

Recent studies reported that exposure of juvenile rats to cranial irradiation affects hypothalamic-pituitary-adrenal (HPA) axis stability, leading to its activation along with radiation-induced inflammation. In the present study, we hypothesized whether inflammatory reaction in the CNS could be a mediator of HPA axis response to cranial irradiation (CI). Therefore, we analyzed time-course changes of serum corticosterone level, as well IL-1 beta and TNF-alpha level in the serum and hypothalamus of juvenile rats after CI. Protein and gene expression of the glucocorticoid receptor (GR) and nuclear factor kappaB (NF kappa B) were examined in the hippocampus within 24 h postirradiation interval. Cranial irradiation led to rapid induction of both GR and NF kappa B mRNA and protein in the hippocampus at 1 h. The increment in NF kappa B protein persisted for 2 h, therefore NF kappa B/GR protein ratio was turned in favor of NF kappa B. Central inflammation was characterized by increased IL-1 beta in the hypothalamus, with maximum levels at 2 and 4 h after irradiation, while both IL-1 beta and TNF-alpha were undetectable in the serum. Enhanced hypothalamic IL-1 beta probably induced the relocation of hippocampal NF kappa B to the nucleus and decreased NF kappa B mRNA at 6 h, indicating promotion of inflammation in the key tissue for HPA axis regulation. Concomitant increase of corticosterone level and enhanced GR nuclear translocation in the hippocampus at 6 h might represent a compensatory mechanism for observed inflammation. Our results indicate that acute radiation response is characterized by increased central inflammation and concomitant HPA axis activation, most likely having a role in protection of the organism from overwhelming inflammatory reaction.Ministry of Education and Science of the Republic of Serbia [173044