Effects of Dose Rate on the Reproductive Cell Death and Early Mitochondrial Membrane Potential in Different Human Epithelium-Derived Cells Exposed to Gamma Rays

Abstract

Dose rate is one of the most varied experimental parameters in radiation biology research. In this study, effects of dose rates on the radiation responses of 2 different types of human epithelium-derived cells, immortalized keratinocytes (HaCaT), and colorectal cancer cells (HCT116 p53 þ/þ and HCT116 p53 À/À) were systematically studied. Cells were g-irradiated at one of the 4 dose rates (24.6, 109, 564, and 1168 mGy/min) to a total dose of 0.5 to 2 Gy. Clonogenic survival and mitochondrial membrane potential (MMP) were measured to assess the levels of reproductive cell death and damage to mitochondrial physiology, respectively. It was found that clonogenic survival was similar at all 4 tested dose rates in the 3 cell lines. The loss of MMP occurred at all tested dose rates in all 3 cell lines except for one case where the MMP increased in HCT116 p53 þ/þ cells after exposure to 0.5 Gy at 24.6 mGy/min. In HCT116 cells, the loss of MMP was the most severe at high dose/dose rate combination exposure and when p53 was expressed. In contrast, no effect in dose rate was observed with HaCaT cells as the reduction level of MMP was similar at the tested dose rates.

A Comprehensive Analysis of the Relationship Between Dose Rate and Biological Effects in Preclinical and Clinical Studies, From Brachytherapy to Flattening Filter Free Radiation Therapy and FLASH Irradiation

“…In Vo et al's study, 5 which used a low DR p (24-100 mGy/min, equal to the average DR because the irradiation was continuous), damage was not reported, but the surviving fraction at 2 Gy suggests rapid repair of the damages, probably less complex. In Sorensen et al's study, 21 increasing the DR p from 56.5 to 338 Gy/s did not appear to have consequences on clonogenic survival.…”

“…Data from 4 representative studies [5][6][7][8] have been selected to highlight the limitations inherent to the articles reviewed. These studies were those for which temporal and spatial microstructure parameters of the irradiation beams were reported (mean and instantaneous DR [DR pulse ] total dose, pulse frequency rate, and pulse width).…”

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

“…Noticeably, radiation-induced damage to the cell constituents occurs in a dose-dependent manner. Thus, the extent of the subsequent cell remodeling ultimately leads to either cell restoration or a complete cell loss (e.g., cell senescence or death) (64)(65)(66)(67). In this respect, considering the high energy of the penetrating radiation, the molecular damage to the cell and tissue structures from the direct radiation impact is not specific, although the consequent reactive responses to the radiation-produced injury are.…”

“…Therefore, the concept of amplification of the radiation-induced ''primary'' oxidative stress has been further refocused on the shift of metabolic and pro-inflammatory redox pathways in irradiated cells (62,63,66,77,(81)(82)(83)(84)(85). Indeed, numerous observations indicate that the radiation-induced radiolysis can affect crucial cellular constituents and tilt calcium homeostasis, and thus can activate a cascade of metabolic responses leading to a prolonged oxidative stress which propagates systemically (64,(80)(81)(82)(83)(84)(85)(86)(87). Moreover, there are several redox mechanisms, which have been proposed to drive the metabolic oxidative stress.…”

“…Notably, excessive generation of RLS implicated in the Michael addition/reaction can spread carbonyl (electrophilic) stress from the targeted cells to bystander cells via the gap junction network or the extracellular vesicle mechanisms, thus producing non-targeted effects including mitochondrial dysfunction, ER stress, disturbance of calcium homeostasis, and epigenetic and clastogenic dysregulations (86,100,102). Overall, while the ''radiolysis phase'' is short lived, it causes devastating systemic effects, i.e., radiation-induced damage to proteins and lipids, posttranslational modification of proteins, impairment of DNA, epigenetic alterations and formation of aberrant organelles generates an array of mediators of stress, danger and inflammation that interfere with cell communication systems and homeostatic control (55,64,87,108,109). In conjunction with these events, activation of free radical reactions, formation of ROS, RNS, RCS, RLS, the Schiff and etheno adducts, the products of protein sulfhydryl oxidation as well as depletion of antioxidants are major features of radiolysis in tissues and fluids, and therefore, are considered to be biomarkers of oxidative stress after radiation exposure.…”