Release of chemoattractants for human monocytes from endothelial cells by interaction with neutrophils

Abstract

Objectives: The release of monocyte chemoattractant protein-1 (MCP-1) in the vessel wall may lead to accumulation of monocytes in the subendothelial space. The role of neutrophils (PMNL) in the initiation of this process is unknown. We tested whether PMNL are able to induce the production and release of MCP-1 in endothelial cells. Methods: PMNL were allowed to interact with human umbilical vein endothelial cell (HUVEC) monolayers in culture. Culture media were collected and assessed for chemotactic activity on mononuclear leukocytes (MNC) or purified monocytes in a modified Boyden chamber assay. Additionally, MCP-1 levels in supernatants were quantified by ELISA. Results: Media from unstimulated HUVEC culture supernatants induced a slight increase (1.2-fold) of MNC and purified monocyte chemotaxis, which was significantly augmented by addition of PMNL for I h (1.4-fold; P < 0.05). The increase in chemotaxis was time- and dose-dependent and could be blocked by an anti-MCP- 1 monoclonal antibody. Media obtained after coculture of PMNL and HUVEC for 1-5 h contained increased amounts of MCP-1 as measured by ELISA; addition of cycloheximide abolished this response. Conclusions: Interaction of PMNL with endothelium induces the release of functionally active MCP-1 suggesting that in the vascular wall, PMNL may play a role in the recruitment of MNC.