Mitochondrial сomplex III contributes to LPS-induced ROS production in hemocytes of Anadarakagoshimensis.

Hemoglobin-containing bivalves are a unique object for studying the interaction between respiratory pigments and the immune response, but the sources for reactive oxygen species (ROS) production during immune activation in these species remain poorly understood. In this work, we investigated for the first time the mitochondrial source of ROS production in A. kagoshimensis hemocytes under non-specific immune system activation conditions by lipopolysaccharide (LPS). Stimulation by LPS for 1.5 h led to a significant twofold increase in the intracellular ROS level and hyperpolarization of the mitochondrial membrane. The use of specific electron-transport chain inhibitors (rotenone, S3QEL, azide) supports a contribution of the ubiquinone site (Qo) of mitochondrial complex III to ROS production in both unstimulated and during immune activation. Inhibition of complexes I and IV reduced the membrane potential, did not significantly alter basal or LPS-induced ROS production level. Despite a significant oxidative burst, short-term stimulation provided no evidence of DNA damage or impaired hemocyte adhesion over the period examined. These findings suggest that mitochondrial complex III contributes to ROS production in regulating the oxidative burst during immune responses in hemoglobin-containing mollusks.