Mild mitochondrial uncoupling protects from ionizing radiation induced cell death by attenuating oxidative stress and mitochondrial damage

Abstract

Ionizing radiation (IR) induced mitochondrial dysfunction is associated with enhanced radiation stimulated metabolic oxidative stress that interacts randomly with intracellular bio-macromolecules causing lethal cellular injury and cell death. Since mild mitochondrial uncoupling emerged as a valuable therapeutic approach by regulating oxidative stress in most prevalent human diseases including ageing, ischemic reperfusion injury, and neurodegeneration with comparable features of IR inflicted mitochondrial damage. Therefore, we explored whether mitochondrial uncoupling could also protect from IR induced cytotoxic insult. Our results showed that DNP, BHT, FCCP, and BAM15 are safe to cells at different concentrations range depending on their respective mitochondrial uncoupling potential. Pre-incubation of murine fibroblast (NIH/3T3) cells with the safe concentration of these uncouplers followed by gamma (γ)-radiation showed significant cell growth recovery, reduced ROS generation, and apoptosis, compared to IR treatment alone. We observed that DNP pre-treatment increased the surviving fraction of IR exposed HEK-293, Raw 264.7 and NIH/3T3 cells. Additionally, DNP pre-treatment followed by IR leads to reduced total and mitochondrial oxidative stress (mos), regulated calcium (Ca²⁺) homeostasis, and mitochondrial bioenergetics in NIH/3T3 cells. It also significantly reduced macromolecular oxidation, correlated with the regulated ROS generation and antioxidant defence system. Moreover, DNP facilitated DNA repair kinetics evidenced by reducing the number of γ-H2AX foci formation and fragmented nuclei with time. DNP pre-incubation restrained the radiation induced pro-apoptotic factors and inhibits apoptosis. Our findings raise the possibility that mild mitochondrial uncoupling with DNP could be a potential therapeutic approach for radiation induced cytotoxic insult associated with an altered mitochondrial function.

Keywords: DNP; Ionizing radiation; Mitochondrial uncoupler; Oxidative stress; ROS; Radioresistance.