Noradrenaline reduces the stimulatory effect of interleukin‐1α on reactive oxygen species production by oyster immunocytes

. A growing body of evidence suggests that interleukin-1α (IL-1α) is present in invertebrates. Both invertebrate and human IL-1α can bind to invertebrate receptors and stimulate invertebrate immune functions. The present study shows that IL-1α increases reactive oxygen species (ROS) production by oyster immunocytes. However, physiological doses of noradrenaline (NA) exert a suppressive effect on IL-1α stimulation in vitro. The β-adrenoceptor agonist isoproterenol mimicked the effects of NA and the β-adrenoceptor antagonist propanolol blocked the NA-induced suppression of hemocyte responsiveness to IL-1α. The type IV phosphodiesterase inhibitor rolipram acted in synergy with isoproterenol to reduce hemocyte response to IL-1α and the protein kinase A inhibitor H-89 suppressed the effects of isoproterenol. These results suggest that circulating NA impairs IL-1α-stimulation of oyster hemocyte via a β-adrenoceptor/cyclic AMP/protein kinase-A signaling pathway. Considering that mollusc immunocytes secrete NA, an autocrine regulatory loop may also modulate the ability of these cells to respond to IL-1α.