Interleukin-1 Receptor Antagonist Expression in Human Endothelial Cells and Atherosclerosis

Abstract

Abstract-The proinflammatory cytokine interleukin (IL)-1 is expressed mainly within the endothelium of atherosclerotic plaques and may be linked with inflammatory mechanisms of atherogenesis. IL-1 action is complex and regulated in part by its naturally occurring inhibitor, the IL-1 receptor antagonist (IL-1ra). Therefore, we studied differential and specific isoform expression of IL-1ra in the endothelium of diseased coronary arteries and in endothelial cells (ECs) stimulated under defined conditions. In view of an association with IL-1ra gene (IL-1RN) polymorphism, the influence of endothelial cell genotype at IL-1RN on IL-1ra protein production was also examined. Secreted IL-1ra and intracellular IL-1ra mRNAs were detected by semiquantitative reverse transcription-polymerase chain reaction in human atherosclerotic and dilated cardiomyopathic coronary arteries; protein expression appeared increased in atherosclerotic compared with dilated cardiomyopathic arteries, where IL-1ra appeared to be confined to the endothelium. Only intracellular IL-1ra type I mRNA was detected in human umbilical vein ECs (HUVECs) and human coronary artery ECs (HCAECs) when they were stimulated with bacterial lipopolysaccharide/phorbol myristate acetate and transforming growth factor-␤. IL-1␤ and IL-1␣ were without effect. IL-1ra protein was detected in HUVECs (intracellular IL-1ra), HCAECs (intracellular IL-1ra), and human coronary artery smooth muscle cells (intracellular IL-1ra) by immunoprecipitation and Western blot. IL-1ra was detected in HUVEC cell lysates by ELISA and appeared to be influenced by the genotype of the IL-1RN variable number tandem repeat, an 86-bp repeat polymorphism in intron 2 of the IL-1ra gene, with lower levels of IL-1ra produced by IL-1RN allele 2-containing cells (ratio of IL-1ra to total protein: for 1,1 homozygotes, . This is the first demonstration of IL-1ra in human diseased arteries, stimulated HUVECs, and HCAECs and indicates the endothelial cell as an important source. Endothelial IL-1ra production may be controlled by the endothelial IL-1RN genotype. These data further support the role of the IL-1 system of cytokines in the pathogenesis of atherosclerosis. (Arterioscler Thromb Vasc Biol.

Prevention of Inflammation-Induced Endothelial Dysfunction

“…6 IL-1ra may also derive from the vessel wall itself. 7 It is recognized that significant local cellular or tissue generation of cytokines can occur without a corresponding increase in circulating levels, but the cytokine measurements in this study confirm that a systemic response was generated, with a profile similar to that reported previously. 3 The lack of effect on CRP is expected because of the relatively short time course of this study.…”

Altered Interleukin-1 Receptor Antagonist and Interleukin-18 mRNA Expression in Myocardial Tissues of Patients with Dilatated Cardiomyopathy

“…In columnar epithelial cells, IL-1RN*2 has been shown to be associated with reduced protein content (69). In Dewberry et al (65), the association of IL-1RN*2 with decreased icIL-1ra protein production in HUVECs was also documented. Association of IL-1RN*2 with DCM could be one possible explanation of reduced IL-1ra gene expression in DCM myocardium.…”

“…The alteration of the IL-1/IL-1ra balance has been proposed to be one of the mechanisms promoting progression of cardiovascular diseases. It has been described that coronary arteries of ICM patients expressed more IL-1ra mRNA and immunoreactive IL-1ra protein than DCM arteries (65). In heart tissues, higher expression of IL-1β mRNA was detected in DCM compared with ICM patients, and it may be assumed that the IL-1/IL-1ra balance could be disturbed by this enhanced IL-1 production (14).…”

Interleukin‐1 receptor antagonist (IL‐1ra) modulates endothelial cell proliferation

“…We have previously reported that a genetic variant of IL-1ra is linked with reduced icIL-1ra1 production by EC [8] and a diminished proliferative capacity by EC [9]. Other studies have suggested a role for G1 cell cycle proteins in the IL-1 mediated proliferation of vascular smooth muscle cells [10] and the senescence of ECs [11].…”