DIETARY FLAXSEED PREVENTS RADIATION-INDUCED OXIDATIVE LUNG DAMAGE, INFLAMMATION AND FIBROSIS IN A MOUSE MODEL OF THORACIC RADIATION INJURY James C. Lee, M.D.,* Ryan Krochak, B.S.,* Aaron Blouin,* Stathis Kanterakis, B.S.,+ Shampa Chatterjee, Ph.D.,* Evguenia Arguiri, B.S.,* Anil Vachani, M.D.,* Charalambos C. Solomides, M.D.,† Keith A. Cengel, M.D., Ph.D.,‡ and Melpo Christofidou-Solomidou, PhD.**
Department of Medicine, Pulmonary Allergy and Critical Care Division, Philadelphia, PA 19104+ Department of Pharmacology, University of Pennsylvania Medical Center, Philadelphia, PA 19104‡ Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, PA 191044 †Department of Pathology, Temple University Hospital, Philadelphia, PA 19140
Abstract Flaxseed (FS) has high contents of omega-3 fatty acids and lignans with antioxidant properties. Its use in preventing thoracic X-ray radiation therapy (XRT)-induced pneumonopathy has never been evaluated. We evaluated FS supplementation given to mice given before and post-XRT. FS-derived lignans, known for their direct antioxidant properties, were evaluated in abrogating ROS generation in cultured endothelial cells following gamma radiation exposure. Mice were fed 10% FS or isocaloric control diet for three weeks and given 13.5 Gy thoracic XRT. Lungs were evaluated at 24 hours for markers of radiation-induced injury, three weeks for acute lung damage (lipid peroxidation, lung edema and inflammation), and at four months for late lung damage (inflammation and fibrosis). FS-Lignans blunted ROS generation in vitro, resulting from radiation in a dose-dependent manner. FS-fed mice had reduced expression of lung injury biomarkers (Bax, p21, and TGF-beta1) at 24 hours following XRT and reduced oxidative lung damage as measured by malondialdehyde (MDA) levels at 3 weeks following XRT. In addition, FS-fed mice had decreased lung fibrosis as determined by hydroxyproline content and decreased inflammatory cell influx into lungs at 4 months post XRT. Importantly, when Lewis Lung carcinoma cells were injected systemically in mice, FS dietary supplementation did not appear to protect lung tumors from responding to thoracic XRT. Dietary FS is protective against pulmonary fibrosis, inflammation and oxidative lung damage in a murine model. Moreover, in this model, tumor radioprotection was not observed. FS lignans exhibited potent radiation-induced ROS scavenging action. Taken together, these data suggest that dietary flaxseed may be clinically useful as an agent to increase the therapeutic index of thoracic XRT by increasing the radiation tolerance of lung tissues.
Dietary flaxseed administered post thoracic radiation treatment improves survival and mitigates radiation-induced pneumonopathy in mice
Melpo Christofidou-Solomidou, Sonia Tyagi, Kay-See Tan, Sarah Hagan, Ralph Pietrofesa, Floyd Dukes, Evguenia Arguiri, Daniel F Heitjan, Charalambos C Solomides, Keith A Cengel Departments of Medicine, Pulmonary, Allergy and Critical Care Division, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA Biostatistics & Epidemiology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA Department of Pathology, Jefferson University Hospital, Philadelphia, PA 19140, USA
Abstract Background: Flaxseed (FS) is a dietary supplement known for its antioxidant and anti-inflammatory properties. Radiation exposure of lung tissues occurs either when given therapeutically to treat intrathoracic malignancies or incidentally, such as in the case of exposure from inhaled radioisotopes released after the detonation of a radiological dispersion devise (RDD). Such exposure is associated with pulmonary inflammation, oxidative tissue damage and irreversible lung fibrosis. We previously reported that dietary FS prevents pneumonopathy in a rodent model of thoracic X-ray radiation therapy (XRT). However, flaxseed’s therapeutic usefulness in mitigating radiation effects post-exposure has never been evaluated.
Methods: We evaluated the effects of a 10%FS or isocaloric control diet given to mice (C57/BL6) in 2 separate experiments (n=15-25 mice/group) on 0, 2, 4, 6 weeks post a single dose 13.5 Gy thoracic XRT and compared it to an established radiation-protective diet given preventively, starting at 3 weeks prior to XRT. Lungs were evaluated four months post-XRT for blood oxygenation levels, inflammation and fibrosis.
Results: Irradiated mice fed a 0%FS diet had a 4-month survival rate of 40% as compared to 70-88% survival in irradiated FS-fed mouse groups. Additionally, all irradiated FS-fed mice had decreased fibrosis compared to those fed 0%FS. Lung OH-Proline content ranged from 96.5±7.1 to 110.2±7.7 μg/ml (Mean ± SEM) in all irradiated FS-fed mouse groups, as compared to 138±10.8 μg/ml for mice on 0%FS. Concomitantly, bronchoalveolar lavage (BAL) protein and weight loss associated with radiation cachexia was significantly decreased in all FS-fed groups. Inflammatory
cell influx to lungs also decreased significantly except when FS
diet was delayed by 4 and 6 weeks post XRT. All FS-fed mice (irradiated or not), maintained a higher blood oxygenation level as compared to mice on 0%FS. Similarly, multiplex cytokine analysis in the BAL fluid revealed a significant decrease of specific inflammatory cytokines in FS-fed mice.
Conclusions: Dietary FS given post-XRT mitigates radiation effects by decreasing pulmonary fibrosis, inflammation, cytokine secretion and lung damage while enhancing mouse survival. Dietary supplementation of FS may be a useful adjuvant treatment mitigating adverse effects of radiation in individuals exposed to inhaled radioisotopes or incidental radiation.