Hemocytes of the bivalve Aulacomya atra atra from Bahia Nueva (Chubut) as Biomarkers of Oxidative Stress

Abstract

Bivalve mollusks exposed to a wide variety of natural and anthropogenic environmental changes are widely used as sentinels. These factors can cause an imbalance between the generation and elimination of reactive oxygen species (ROS) and reactive nitrogen species (RNS), leading to an oxidative stress that is manifested by alterations of the antioxidant defense system and/or oxidative damage. The hemocytes constitute the immune system in bivalves, and cell death processes have been recently described as part of the mechanism of defense against various pathogens and contaminants. Previous studies showed a higher content of trace metals Fe and Cd in the gills and digestive gland of the Aulacomya atra atra from Folías Wreck (impacted area) than from Punta Cuevas (control area). In order to compare oxidative stress conditions in bivalves obtained from both sites, we evaluated the production of ROS and oxidative stress biomarkers in hemocytes from the A. atra atra during the month of September of 2015. The results obtained by flow cytometry, using MitoSox as probe, showed that superoxide anion was 58% higher in bivalve’s hemocytes from Folías Wreck than in those from the reference place Punta Cuevas. The oxidation of the dye 2´7´dichlorofluorescein diacetate (DCFH-DA), as a general indicator of oxidative stress, showed a 14% increase in bivalve’s hemocytes from Folías Wreck, as compared to hemocytes from Punta Cuevas. Thiobarbituric acid reactive substances (TBARS) content showed no differences between hemocytes from animals isolated from both locations. In addition, the content of lipid radical measured by Electron Spin Resonance increased 2.1 fold in the hemocytes from Folías Wreck samples as compared to the level obtained in hemocytes from bivalves collected from Punta Cuevas. The oxidized/depleted cardiolipin was 16% higher in samples obtained from Folías Wreck than in Punta Cuevas. Based on these results, it can be concluded that hemocytes from the ribbed mussel A. atra atra could be used as a model to evaluate oxidative stress induced by pollutants or other environmental stressors.