Possible role of seasonality and harmful algal blooms (HAB) on the oxidative and nitrosative metabolisms in hemocytes

Abstract

Bivalves survive to biotoxin consumption but their metabolism could be affected. The objective of this work was to study the oxidative and nitrosative changes in the hemocytes of the mussel Mytilus edulis platensis in different seasons, including spring, characterized by the appearance of harmful algal blooms (HAB). Reactive species generation rate (measured as the 2′,7′dichlorofluorescein diacetate oxidation rate) was increased by 2.5- and 8.3-fold in hemocytes from spring and summer, respectively, as compared to winter samples. Neither total Fe nor labile Fe pool content was changed in the three seasons. Superoxide anion generation rate was 3-fold higher in spring as compared to winter and summer samples. Catalase content in spring cells were significantly higher as compared to winter (60%) and summer (3-fold increase) but glutathione-S-transferase activity only increased compared to summer season (125% increase). Lipid radical content in spring samples was 140 and 50% higher as compared to cells from winter and summer, respectively. Nitric oxide and nitro-tyrosine content were significantly higher in samples from spring as compared to values obtained either in winter or summer cells. Considering the aspects that influence metabolism, changes in temperature seem to mainly affect the oxidative over the nitrosative condition of the hemocytes. Nevertheless, HAB biotoxins seem as a contributing factor to affect not only reactive oxygen species generation, antioxidant activity and protein/lipid damage, but also the nitrosative metabolism. In this regard, the changes in the nitric oxide content are new and critical evidence that HAB-related toxins could affect reactive nitrogen species metabolism.