A combined γ-H2AX and 53BP1 approach to determine the DNA damage-repair response to exercise in hypoxia

This study examines the interplay between exercise and hypoxia in relation to the DNA damage-repair response; with specific interest to DNA double strand damage. Following two V̇ O2max tests, 14 healthy, male participants completed two exercise trials (hypoxia; 12% FiO2, normoxia; 20.9% FiO2) consisting of cycling for 30-minutes at 80-85% of V̇ O2max relative to the environmental condition. Blood was sampled pre-, immediately post-, 2-, and 4-hours post exercise with additional blood cultured in vitro for 24-, 48-, and 72-hours following the experimental trial. Samples were analysed for single- and double strand DNA damage, FPG-sensitive sites, lipid hydroperoxides, lipid soluble antioxidants, and the ascorbyl free radical quantified by EPR. Exercise caused an increase in single strand breaks and FPG-sensitive sites as a result of exercise (P < 0.05) which was exacerbated following hypoxia (P = 0.02), similar increases in DNA double strand breaks occurred as a result of hypoxia (P < 0.000). With respect to the DNA damage-repair response, single strand breaks, FPG-sensitive sites, and double strand lesions were fully repaired by the 4- (in vivo), 24-, and 48-hour (in vitro) time-points respectively. Changes in lipid hydroperoxides (P = 0.001), the ascorbyl free radical (P = 0.02), and lipid soluble antioxidants (P > 0.05), were also observed following exercise in hypoxia. These findings highlight significant single- and double strand DNA damage and oxidative stress as a function of high-intensity exercise, which is substantially exacerbated in hypoxia which may be attributed to multiple mechanisms of ROS generation. In addition, full repair of DNA damage (SSB, DSB, and FPG-sensitive sites) was observed within 24- and 48-hours of normoxic and hypoxic exercise, respectively.