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 theWorld Ocean, are exposed to sharp fluctuations in abiotic environmentalfactors, accompanied by the development of a physiological stressresponse, with changes in their functional state occurring due tothe release of neurotransmitters into the hemolymph. Catecholaminesare key signaling molecules in the system of neuroendocrine regulationin bivalves, which are also involved in immune response modulationduring physiological stress. Hemocytes, the central effector cellsin cell-mediated immunity of bivalve mollusks, express adrenoreceptorson the surface of their plasma membrane, suggesting a functionalrelationship between external stress and the cellular immune response.In the present work, the effect of adrenaline at concentrationsof 1 and 10 µM on phagocytic, adhesive and aggregation capacityof hemocytes in the Mediterranean mussel Mytilusgalloprovincialis (Lamarck, 1819) was investigated invitro. In addition, we studied the effect of adrenaline on the levelof spontaneous reactive oxygen species (ROS) production and thedynamics of mitochondrial membrane potential (MMP) in hemocytes.Stimulation of mussel hemocytes with adrenaline at a concentrationof 10 µM promoted a significant increase in their phagocytic capacity.A 30-min stimulation with adrenaline at 10 µM led to an increasein hemocyte MMP. At a concentration of 1 µM, adrenaline significantlyincreased the ability of hemocytes to adhere to a solid substrate.No significant changes in the level of adrenaline-induced ROS productionin hemocytes were detected. The results of this work indicate thatadrenaline has an immunomodulatory effect on mussel hemocytes andstimulates their aerobic metabolism.