OxLDL-IgG immune complexes induce expression and secretion of proatherogenic cytokines by cultured human mast cells

Human atherosclerotic lesions contain mast cells and immunoglobulin G immune complexes containing oxidized low-density lipoproteins (oxLDL-IgG ICs). Here we studied whether such oxLDL-IgG ICs can activate human mast cells and induce them to express and secrete pro-inflammatory cytokines that are potentially capable of inducing and amplifying atherogenic processes.

Incubation of cultured human mast cells in the presence of oxLDL-IgG ICs led to a significant dose-dependent upregulation of the expression and secretion of tumor necrosis factor-alpha (TNF-a) and interleukin-8 (IL-8), and the chemotactic cytokine monocyte chemoattractant protein-1 (MCP-1). The secretory responses were dose-dependent and associated with moderate release of histamine and tryptase, which are preformed mast cell mediators contained in the cytoplasmic secretory granules of the cells. Also native LDL-IgG ICs induced similar pro-inflammatory cytokine response, suggesting that ICs per se are important for the IgG IC-induced mast cell activation.

Mast cells in atherosclerotic lesions which also contain oxLDL-IgG ICs may become activated by the ICs and secrete many pro-inflammatory cytokines. Our results suggest that intimal mast cells act as a cellular link between oxLDL-IgG ICs and the inflammatory response in atherosclerosis.