3-nitrotyrosine and Radiation-Pneumonitis

Wholegrain flaxseed (FS), and its lignan component (FLC) consisting mainly of secoisolariciresinol diglucoside (SDG), have potent lung radioprotective properties while not abrogating the efficacy of radiotherapy. However, while the whole grain was recently shown to also have potent mitigating properties in a thoracic radiation pneumonopathy model, the bioactive component in the grain responsible for the mitigation of lung damage was never identified. Lungs may be exposed to radiation therapeutically for thoracic malignancies or incidentally following detonation of a radiological dispersion device. This could potentially lead to pulmonary inflammation, oxidative tissue injury, and fibrosis. This study aimed to evaluate the radiation mitigating effects of FLC in a mouse model of radiation pneumonopathy.. We evaluated FLC-supplemented diets containing SDG lignan levels comparable to those in 10% and 20% whole grain diets. 10% or 20% FLC diets as compared to an isocaloric control diet (0% FLC) were given to mice (C57/BL6) (n=15-30 mice/group) at 24, 48, or 72-hours after single-dose (13.5 Gy) thoracic x-ray treatment (XRT). Mice were evaluated 4 months post-XRT for blood oxygenation, lung inflammation, fibrosis, cytokine and oxidative damage levels, and survival.. FLC significantly mitigated radiation-related animal death. Specifically, mice fed 0% FLC demonstrated 36.7% survival 4 months post-XRT compared to 60-73.3% survival in mice fed 10%-20% FLC initiated 24-72 hours post-XRT. FLC also mitigated radiation-induced lung fibrosis whereby 10% FLC initiated 24-hours post-XRT significantly decreased fibrosis as compared to mice fed control diet while the corresponding TGF-beta1 levels detected immunohistochemically were also decreased. Additionally, 10-20% FLC initiated at any time point post radiation exposure, mitigated radiation-induced lung injury evidenced by decreased bronchoalveolar lavage (BAL) protein and inflammatory cytokine/chemokine release at 16 weeks post-XRT. Importantly, neutrophilic and overall inflammatory cell infiltrate in airways and levels of nitrotyrosine and malondialdehyde (protein and lipid oxidation, respectively) were also mitigated by the lignan diet.. Dietary FLC given early post-XRT mitigated radiation effects by decreasing inflammation, lung injury and eventual fibrosis while improving survival. FLC may be a useful agent, mitigating adverse effects of radiation in individuals exposed to incidental radiation, inhaled radioisotopes or even after the initiation of radiation therapy to treat malignancy.

Topics: Animal Feed; Animals; Bronchoalveolar Lavage Fluid; Butylene Glycols; Cytokines; Female; Fibrosis; Flax; Glucosides; Kaplan-Meier Estimate; Lignans; Lung; Lung Injury; Malondialdehyde; Mice; Mice, Inbred C57BL; Neutrophils; Oxygen; Phytotherapy; Radiation Injuries, Experimental; Radiation Pneumonitis; Radiation-Protective Agents; Seeds; Survival Rate; Time Factors; Transforming Growth Factor beta1; Tyrosine

The purpose of this study was to determine if radiation-induced lung damage is associated with induction of nitric oxide synthase (NOS) II and nitrotyrosine in an irradiated lung mouse model. The thorax of BALBc mice were exposed to 14 Gy radiation (experimental) or no radiation (control) and killed after at 1, 3, 6, 12, and 24 hours; 3, 15, and 30 days; and 3 and 6 months after treatment. Lung sections were processed for immunohistochemistry using NOS II and nitrotyrosine polyclonal antisera and in situ hybridization using 35S labeled probes for mouse NOS II. Quantitative analysis of experimental and control sections showed significant induction of NOS II and nitrotyrosine in alveolar macrophages from 6 hours to 30 days postirradiation, which was diminished by 3 months. The airway and alveolar epithelium and vascular endothelium showed strong NOS II expression at 15 to 30 days postirradiation. Nitrotyrosine immunostaining was also strongly evident in the alveolar epithelium and vascular endothelium during this period. There was little or no NOS II or nitrotyrosine in the sham control lungs throughout the study. These findings demonstrate increased formation of both NO and nitrotyrosine after radiation treatment and suggest a role for these molecules in the pathogenesis of radiation-induced lung damage.

Topics: Animals; Disease Models, Animal; Female; Immunohistochemistry; In Situ Hybridization; Mice; Mice, Inbred BALB C; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Radiation Injuries, Experimental; Radiation Pneumonitis; Tyrosine