ROS formation, mitochondrial potential and osmotic stability of the lamprey red blood cells: effect of adrenergic stimulation and hypoosmotic stress.

Semi-anadromous animals experience salinity fluctuations during their life-span period. Alterations of environmental conditions induce stress response where catecholamines (CA) play a central role. Physiological stress and changes in external and internal osmolarity are frequently associated with increased production of reactive oxygen species (ROS). In this work, we studied the involvement of the cAMP/PKA pathway in mediating catecholamine-dependent effects on osmoregulatory responses, intracellular production of ROS, and mitochondrial membrane potential of the river lamprey (Lampetra fluviatilis, Linnaeus, 1758) red blood cells (RBCs). We also investigated the role of hypoosmotic shock in the process of ROS production and mitochondrial respiration of RBCs. For this, osmotic stability and the dynamics of the regulatory volume decrease (RVD) following hypoosmotic swelling, intracellular ROS levels, and changes in mitochondrial membrane potential were assessed in RBCs treated with epinephrine (Epi, 25 µM) and forskolin (Forsk, 20 µM). Epi and Forsk markedly reduced the osmotic stability of the lamprey RBCs whereas did not affect the dynamics of the RVD response in a hypoosmotic environment. Activation of PKA with Epi and Forsk increased ROS levels and decreased mitochondrial membrane potential of the lamprey RBCs. In contrast, upon hypoosmotic shock enhanced ROS production in RBCs was accompanied by increased mitochondrial membrane potential. Overall, a decrease in RBC osmotic stability and the enhancement of ROS formation induced by ß-adrenergic stimulation raises concerns about stress-associated changes in RBC functions in agnathans. Increased ROS production in RBCs under hypoosmotic shock indicates that a decrease in blood osmolarity may be associated with oxidative damage of RBCs during lamprey migration.

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793).

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Shift in hemocyte immune parameters of marine bivalve Mytilus galloprovincialis (Lamarck, 1819) after exposure to methane.

Methane are widely used in industry as an emerge source may be released significantly higher aquatic ecosystems due to gas seepages. In this study, short-term (90 min) methane effects on bivalve hemocytes were investigated using flow cytometry. Hemocyte parameters including hemolymph cellular composition, phagocytosis activity, mitochondrial membrane potential and reactive oxygen species (ROS) content were evaluated in the mussel Mytilus galloprovincialis (Lamarck, 1819) exposed to hypoxia (control group), pure methane and industrial methane (industrial hydrocarbon mixture). Comparison of biomarkers showed that the mussel was more sensitive to methane than to low oxygen concentration, supporting the effects of methane on the mussel's immune system. After exposure to pure and industrial methane, the number of granulocytes decreased dramatically and the levels of reactive oxygen species, mitochondrial membrane potential and phagocytosis capacity increased significantly. It was shown that the methane type-dependent effect was pronounced, with industrial methane leading to more pronounced changes.