Abstract
Exposure to oxygen-rich environments can lead to oxidative damage, increased body iron stores, and changes in status of some vitamins, including folate. Assessing the type of oxidative damage in these environments and determining its relationships with changes in folate status are important for defining nutrient requirements and designing countermeasures to mitigate these effects. Responses of humans to oxidative stressors were examined in participants undergoing a saturation dive in an environment with increased partial pressure of oxygen, a NASA Extreme Environment Mission Operations mission. Six participants completed a 13-d saturation dive in a habitat 19 m below the ocean surface near Key Largo, FL. Fasting blood samples were collected before, twice during, and twice after the dive and analyzed for biochemical markers of iron status, oxidative damage, and vitamin status. Body iron stores and ferritin increased during the dive (P<0.001), with a concomitant decrease in RBC folate (P<0.001) and superoxide dismutase activity (P<0.001). Folate status was correlated with serum ferritin (Pearson r = −0.34, P<0.05). Peripheral blood mononuclear cell poly(ADP-ribose) increased during the dive and the increase was significant by the end of the dive (P<0.001); γ-H2AX did not change during the mission. Together, the data provide evidence that when body iron stores were elevated in a hyperoxic environment, a DNA damage repair response occurred in peripheral blood mononuclear cells, but double-stranded DNA damage did not. In addition, folate status decreases quickly in this environment, and this study provides evidence that folate requirements may be greater when body iron stores and DNA damage repair responses are elevated.
Highlights
Saturation dives involve long-duration stays in a closed environment with an increased partial pressure of oxygen
Increased oxygen exposure in 10- to 30-d saturation dives can lead to increases in body iron stores [1,3,4,5,6], and evidence exists that the status of vitamins—in particular, B vitamins involved in 1-carbon metabolism—could be affected by the oxidative environment [5]
Plasma catalase activity was greater during the dive than at baseline (P,0.05, Table 1), and at the end of the dive (MD13), whole-blood superoxide dismutase (SOD) was decreased from baseline (P,0.001, Table 1)
Summary
Saturation dives involve long-duration (several days to weeks) stays in a closed environment with an increased partial pressure of oxygen. Increased oxygen exposure in 10- to 30-d saturation dives can lead to increases in body iron stores [1,3,4,5,6], and evidence exists that the status of vitamins—in particular, B vitamins involved in 1-carbon metabolism (for example, folate and vitamins B6 and B12)—could be affected by the oxidative environment [5]. In support of this concept, homocysteine was elevated during 10- to 12-d saturation dives [5]. An abundance of literature supports the notion that excess iron can be toxic, through the formation of oxygen free radicals or increased availability of iron to pathogens or cancer cells, both of which are usually limited by iron availability [8,9,10]
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