Abstract

Ulva lactuca is a cosmopolite marine alga with high tolerance to the toxic polycyclic aromatic hydrocarbon Benzo[a]pyrene (BaP) present in crude oil spills in central Chile. With the aim to study its tolerance mechanism the alga was cultivated with 5 μM of BaP for 72 h. It was observed that BaP levels in the culture medium decreased rapidly reaching a minimal concentration at 12 h, on the other hand the levels of BaP in the alga tissues increased reaching a maximum at 6 h, remaining stable until 24 h, and then slowly decreasing until 72 h. BaP produced oxidative stress in the alga, hydrogen peroxide and superoxide anions production was observed, increasing gradually with a maximum at 24 h and then decreasing until 72 h. Lipoperoxides were also produced, with a maximum at 6 h and then decreasing until 72 h. The activities of the antioxidant enzymes and the transcript levels of superoxide dismutase, ascorbate peroxidase, glutathione reductase and glutathione peroxidase were increased, reaching maximum levels at 12 h, and catalase reached a maximum activity at 48 h. In addition, the activity and transcript levels of glutathione S-transferase (GST) were also increased with a maximum at 12 h of culture. Regarding the metabolization mechanism, it was observed that the inhibition of CYP450 monooxygenases and the inhibition of GST kept the BaP levels high in the alga. This indicates that BaP is incorporated rapidly into the alga, the compound induces oxidative stress and the activation of antioxidant enzymes, and then CYP450 monooxygenases and GST participate in the metabolization of the compound in U. lactuca. Financed by Fondecyt de Iniciación 11180189 and Programa de Inserción en la Academia PAI79170105, Agencia Nacional de Investigación y Desarrollo, Chile.