Induction of reactive oxygen species and algal growth inhibition by tritiated water with or without copper

Abstract

Tritium ((3) H) is a radioactive element of ecological concern because of its release into aquatic ecosystems from nuclear power plants. However, the acute and chronic effects of tritiated water (HTO) on aquatic organisms are poorly documented, as are its effects on oxidative stress. In addition, the effects of HTO in combination with other contaminants remain largely unexamined. Herein, we document the effect of HTO on a primary aquatic producer (Chlamydomonas reinhardtii) by measuring growth and oxidative stress using fluorimetric (H(2) DCF-DA) determination of Reactive Oxygen Species (ROS) production. The maximum cell density of the alga (1.65 × 10(6) cells mL(-1) ) was reduced by 23% (1.27 × 10(6) cells mL(-1) ) at the highest exposure tested (59 MBq mL(-1) HTO), whereas cells exposed to 0.9 MBq mL(-1) showed a significantly enhanced maximum cell density of 1.90 × 10(6) cells mL(-1) , an increase of 15%. With regard to oxidative stress, exposure to HTO (0.04, 0.16, and 2.8 MBq mL(-1) ) induced an early dose-dependent peak in ROS production after 14-15 min of exposure, followed by a slow decrease in ROS which stabilized after 60 min. Moreover, this study showed that the presence of HTO may influence the impact of other conventional, nonradioactive contaminants, such as copper, a well known oxidizing trace metal for aquatic organisms. A significant synergic effect of copper and HTO on ROS production was observed. This synergic effect on oxidative stress was shown to be linked to an enhanced copper uptake rate measured in the presence of HTO (> 4 times). We conclude that HTO should be considered as a sensitizer when in a mixture with other contaminants, especially through interactions on the antioxidant system of algae.

Tritiated Water Induces Toxicity in Human Umbilical Vein Vascular Endothelial Cells via IL8

“…10 However, consensus on the RBE of tritium has not yet been reached. [15][16][17][18] The UK Advisory Group on Ionizing Radiation released a report suggesting that given the large number of radiobiology studies that focus on tritium, its RBE should be classified as a minimum of 2 and that 3 should be considered for safety. 19 Although the biological effects of high doses of tritium have been defined and genetic and specific tumor effects have been identified in animal models after long-term exposure, epidemiological investigations into the health risks associated with exposure to tritium are not yet publicly available.…”

“… 10 However, consensus on the RBE of tritium has not yet been reached. 15 - 18 The UK Advisory Group on Ionizing Radiation released a report suggesting that given the large number of radiobiology studies that focus on tritium, its RBE should be classified as a minimum of 2 and that 3 should be considered for safety. 19 …”

Modifying action of tritium on the charophytes bioelectrical response to anthropogenic pollution

“…Possible explanation of HTO modifying action on the Al toxicity on Nitellopsis obtusa electrogenesis might also occur through the oxidative stress promotion. It was shown that HTO and copper have a synergetic effect on reactive oxygen species (ROS) production [6]. HTO toxicity can be expressed via local direct action on PM structures and also trough the water radiolysis resulting in induction of oxidative stress and ROS production in plant cell.…”

“…The cells in both groups were incubated for half an hour after the exogenous application of Al or Al and HTO mixture to provide sufficient time for Al to penetrate into the cell. HTO toxicity could be also expressed within the cell after this time-period [6]. Both groups were examined in control conditions (APW) before administration of Al or mixture of Al and HTO.…”

“…Furthermore, it is tending to show an effect at a very low dose even under the predictable effective dose rate threshold [4,5]. Tritium can damage the organism through direct ionization of the cell molecules or acting indirectly via production of reactive oxygen species (ROS), or sensitization of the organism to the impact of other contaminants [6]. Thus, the modifying interaction between HTO and Al may occur both in plants and animals.…”