Pro-inflammatory functions of carp CXCL8-like and CXCb chemokines

Numerous CXC chemokines have been identified in fish, however, their role in inflammation is not well established. Here, CXC chemokines of the CXCL8-like (CXCa_L1 and CXCL8_L2) and CXCL9/10/11-like (CXCb) subset were investigated in carp. Recombinant CXCa_L1, CXCL8_L2 and CXCb all stimulated chemotaxis of macrophages and granulocytes in vitro. CXCb also attracted lymphocytes. Distinct effects on phagocyte activation were observed: the CXCL8-like chemokines increase respiratory burst activity, but not nitrite production. The three chemokines differentially induced a moderate increase in IL-1β, CXCa_L1 and CXCL8_L2 gene expression. Intracellular calcium mobilization in granulocytes upon CXCa_L1 stimulation implies signal transduction through G-protein coupled CXC receptors. Notably, upon intraperitoneal administration, carp CXCL8-like chemokines strongly induced in vivo leukocyte recruitment, including neutrophils and monocytes/macrophages, in contrast to CXCb, for which the number of recruited leukocytes was low. The results indicate functional homology for carp CXCL8-like and CXCb chemokines with mammalian CXCL8 and CXCL9-11, respectively.