ROS Play a Role in Long‐term Gamma Radiation‐induced Heart Damage

Cardiovascular problems are common side effects of cancer therapy, and the heart is one of the major organs that are of concern for potential damage following radiation exposure. Radiation directly affects biological molecules. However, the most impact of radiation‐mediated cell death derives from the generated free radicals, which increase oxidative stress. Reactive oxygen species (ROS) are a hallmark in cardiovascular diseases (CVD), mainly because of its interplay with nitric oxide (NO). NO offers cardioprotection against ROS‐induced damage and ROS, in turn, limits the beneficial effects of NO. Furthermore, radiation induces adaptive alterations in the vasculature leading to vascular dysfunction. Although pathways triggering cardiovascular damage following radiation exposure involve vascular damage in humans, the long‐term mechanisms by which radiation‐induced oxidative stress affects the heart have not yet been clearly defined. We hypothesized that increased ROS contribute to long‐term heart damage following radiation exposure. Flash frozen heart (apex) samples from male C5BL/6J mice (5 months) sacrificed nine months' post radiation was provided by the Department of Surgery at Duke University. Briefly, live animals were subjected to whole body radiation (dose: 200 cGy) at the Brookhaven National Lab. Control animals received Sham treatment. Transverse sections (10 μm) of heart from irradiated and non‐irradiated mice were obtained in a cryostat. Representative images of cardiac fibers were revealed with H&E staining. Additionally, ROS and NO production were evaluated by confocal microscopy. Briefly, the fluorescent probes, Dihydroethidium (DHE) and DAF‐FM Diacetate, were diluted in PBS (5 μM) and the samples were incubated in a humidified chamber at 37° C for 30 minutes. Slides were imaged using a 20x objective and analyzed using ImageJ software (NIH, Bethesda, MD, USA). Protein expression for NOS isoforms was also assessed using a standard Western blotting technique. Our histological analysis indicates loss of cardiac tissue (heart ‐ apex) in irradiated animals compared to Sham animals, suggestive of anatomical remodeling. Confocal microscopy showed an increase in intracellular ROS in irradiated tissue (n=5; p≤0.05), but no significant difference was observed in NO production (n=5; p>0.05). Different NOS isoforms evaluation showed elevated iNOS protein expression levels in irradiated animals. In conclusion, gamma radiation stimulates sustained ROS production in heart tissue and activation of iNOS might be a mechanism for counterbalancing the disruption in the heart antioxidant response system. Support or Funding Information NASA Florida space Grant Consortium 2018 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .