Ionizing radiation induces mild and dose-independent damage to mitochondria in newt cells

In addition to remarkable regenerative abilities, newts demonstrate a heightened tolerance to radiation compared to mammals. Mitochondria play profound role in cell survival when cells undergo environmental stresses. Thus, our study sought to elucidate the impact of ionizing radiation (IR) on the mitochondria of a newt model Pleurodeles waltl. Primary cells derived from limb tissue of P. waltl were exposed to 0, 5, 10, or 15 Gy X-ray and analyzed at 24h post-irradiation (PIR). Analysis using MitoTracker Red labeling revealed a maximal (p < 0.001) in mitochondrial fission in cells exposed to 5 Gy IR, while mitochondrial fission in cells exposed to 10 and 15 Gy IR was comparable (p < 0.01). Mitochondrial superoxide levels increased in a reverse dose-dependent manner; notably, cells treated with 5 Gy IR produced significantly (p < 0.05) higher mitochondrial superoxide. Mitochondrial membrane potential (ΔΨm) decreased significantly (p < 0.01) with similar extent across all IR-treated groups. Though ΔΨm declined, the ATP content was not changed due to IR. Result from the MTT assay indicated no impairment in mitochondrial activity. Cell counting data suggest negligible impact of IR on viability of cells; however, the phase contrast imaging revealed senescent like morphology of cells. Taken together, cells of P. waltl show mild changes in morphology and function of the mitochondria in response to IR, but seem highly tolerant.