Oxidative Stress Markers in the Common Bream Abramis brama Parasitized with Ligula intestinalis

The present study investigated the effect of Ligula intestinalis L. infection on several components of the antioxidant system and on protein oxidation in the host fish, common bream Abramis brama L. In ligulosed bream, the hepatopancreatic antioxidant system response included a decrease in catalase (CAT) activity, an increase in glutathione S-transferase (GST) activity, and no change in superoxide dismutase (SOD) activity. The contents of molecular antioxidants in the organs of infected bream were inconsistent; for instance, hepatopancreatic α-tocopherol content was significantly lower, whereas retinol content was significantly higher than in uninfected individuals. In contrast, no significant differences were found in the α-tocopherol or retinol content in the skeletal muscles of infected and uninfected fish. The protein oxidation, estimated via protein carbonyl content, was unaffected by ligulosis, as was the activity of proteasomes. However, the activity of calpain, another protease, was significantly higher in the skeletal muscle of infected fish. Overall, the data reveal moderate and tissue-specific alterations in oxidative stress markers in A. brama infected with L. intestinalis, suggesting a complex host-parasite interaction that does not result in severe systemic oxidative damage under the studied conditions.