The modulation of catecholamines on immune response of scallop Chlamys farreri under heat stress

Catecholamines (CAs) play key roles in mediating the physiological responses to various stresses. In the present study, the expression of CA-related genes were examined in the hemocytes of scallop Chlamys farreri under heat stress, and several immune or metabolism-related parameters were investigated after heat stress and adrenoceptor antagonist stimulation. After the scallops were cultured at 28 °C, the mRNA expression level of dopa decarboxylase (CfDDC) and α-adrenoceptor (CfαAR) increased significantly (P < 0.01), whereas that of monoamine oxidase (CfMAO) was down-regulated in the first 6 h (P < 0.05), and then up-regulated to the maximum level at 24 h (P < 0.01). In the hemocytes of scallops injected with adrenoceptor antagonist, the expression levels of peptidoglycan-recognition protein (CfPGRP-S1) and C-type lectin (CfLec-1) began to increase significantly at 2 and 3 h post propranolol and high temperature treatment, respectively (P < 0.01). While the up-regulation of heat shock protein 70 (CfHSP70) post heat stress was significantly inhibited by prazosin injection (P < 0.01), and that of hexokinase (CfHK) was inhibited by both prazosin and propranolol injection (P < 0.01). Moreover, the remarkable increase of relative specific activity of SOD in the hemolymph post heat stress (P < 0.01) was further up-regulated early after prazosin or propranolol injection (P < 0.01), while that of the relative anti-bacterial ability was down-regulated by prazosin or propranolol treatment (P < 0.01). These results collectively indicated that the catecholaminergic neuroendocrine system in scallop could be activated by heat stress to release CAs, which subsequently modulated the immune response and energy metabolism via α- and β-adrenoceptors.