Effect of Adrenaline on Mitochondrial Membrane Potential and Hemocyte Immune Response in the Mediterranean Mussel (Mytilus galloprovincialis)

Bivalve mollusks, inhabitants of the littoral zone of the World Ocean, are exposed to sharp fluctuations in abiotic environmental factors, accompanied by the development of a physiological stress response, with changes in their functional state occurring due to the release of neurotransmitters into the hemolymph. Catecholamines are key signaling molecules in the system of neuroendocrine regulation in bivalves, which are also involved in immune response modulation during physiological stress. Hemocytes, the central effector cells in cell-mediated immunity of bivalve mollusks, express adrenoreceptors on the surface of their plasma membrane, suggesting a functional relationship between external stress and the cellular immune response. In the present work, the effect of adrenaline at concentrations of 1 and 10 µM on phagocytic, adhesive and aggregation capacity of hemocytes in the Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1819) was investigated in vitro. In addition, we studied the effect of adrenaline on the level of spontaneous reactive oxygen species (ROS) production and the dynamics of mitochondrial membrane potential (MMP) in hemocytes. Stimulation of mussel hemocytes with adrenaline at a concentration of 10 µM promoted a significant increase in their phagocytic capacity. A 30-min stimulation with adrenaline at 10 µM led to an increase in hemocyte MMP. At a concentration of 1 µM, adrenaline significantly increased the ability of hemocytes to adhere to a solid substrate. No significant changes in the level of adrenaline-induced ROS production in hemocytes were detected. The results of this work indicate that adrenaline has an immunomodulatory effect on mussel hemocytes and stimulates their aerobic metabolism.