Complement-Induced Expression of Chemokine Genes in Endothelium: Regulation by IL-1-Dependent and -Independent Mechanisms

Abstract

Activation of complement in the vicinity of endothelium is thought to contribute to the tissue manifestations of inflammatory and immune responses. Endothelial cells contribute to these processes in part by the elaboration of chemokines that activate various leukocytes and direct their migration into tissues. We investigated the mechanisms by which activation of complement on endothelial cell surfaces might influence the expression of chemokine genes in endothelial cells. In a model for the immune reaction occurring in a xenograft, human serum, as a source of xenoreactive anti-endothelial Abs and complement, induced expression of the monocyte chemotactic protein-1 (MCP-1), IL-8, and RANTES genes. The MCP-1 and IL-8 genes were expressed within 3 h as a first phase and at > 12 h as a second phase. The RANTES gene was expressed in porcine endothelial cells only 12 h after exposure to human serum. The expression of these genes required activation of complement and assembly of membrane attack complex, as it was inhibited by soluble CR1 and did not occur in the absence of C8. The early phase of MCP-1 and IL-8 gene expression did not require de novo protein synthesis. The late phase of MCP-1, IL-8, and RANTES gene expression predominantly required the production of IL-1alpha as an intermediate step. The results indicate that the expression of chemokine genes in endothelial cells occurs as a function of differential responses to complement and may in part be conditioned by the availability of IL-1alpha.