Resveratrol promotes an inhibitory effect on the turbot scuticociliate parasite Philasterides dicentrarchi by mechanisms related to cellular detoxification

The mechanisms involved in antiparasitic activity of the natural nonflavonoid polyphenol resveratrol (RESV) on the turbot (Psetta maxima) scuticoliate parasite Philasterides dicentarchi were investigated. At concentrations higher than 50 μM, RESV caused significant inhibition of the in vitro growth of the ciliates, which was apparent on the third day of culture and, at the same concentration, RESV caused significant inhibition of O2 consumption. RESV, at a concentration of 100 μM, produced a significant increase in the production of intracellular reactive oxygen species (ROS), which were inhibited by the addition of 1 mM of L (+) ascorbic acid. RESV (100 μM) also caused significant inhibition of peroxidase, catalase and superoxide dismutase activities, but stimulated the activity of the redox regulating enzyme glutathione S-transferase. Confocal microscopy with the mitochondria-sensitive dye MitoTracker Orange CMTMRos revealed that RESV at concentrations higher than 50 μM significantly increased the levels of fluorescence inside mitochondria and, at the same concentration, also caused an increase in the vacuolization of the trophozoites. The results obtained in the present study suggest that the inhibitory activity of RESV on the ciliate P. dicentrarchi is related to the induction of oxidative stress and to the inability of the parasite to eliminate ROS as a result of modified activity of antioxidant enzymes.