Myeloid IκBα Deficiency Promotes Atherogenesis by Enhancing Leukocyte Recruitment to the Plaques

Activation of the transcription factor NF-kappa B appears to be involved in different stages of atherogenesis. In this paper we investigate the role of NF-kappa B inhibitor I kappa B alpha in atherosclerosis. Myeloid-specific deletion of I kappa B alpha results in larger and more advanced lesions in LDL-R-deficient mice without affecting the compositional phenotype of the plaques or systemic inflammatory markers in the plasma. We show that I kappa B alpha-deleted macrophages display enhanced adhesion to an in vitro endothelial cell layer, coinciding with an increased expression of the chemokine CCL5. Also, in vivo we found that I kappa B alpha(del) mice had more leukocytes adhering to the luminal side of the endothelial cell layers that cover the atherosclerotic plaques. Moreover, we introduce ER-MP58 in this paper as a new immunohistochemical tool for quantifying newly recruited myeloid cells in the atherosclerotic lesion. This staining confirms that in I kappa B alpha(del) mice more leukocytes are attracted to the plaques. In conclusion, we show that I kappa B alpha deletion in myeloid cells promotes atherogenesis, probably through an induced leukocyte recruitment to plaques.