Differential Effects of Interleukin-1 Receptor Antagonist and Tumor Necrosis Factor Binding Protein on Fatty-Streak Formation in Apolipoprotein E–Deficient Mice

Abstract

Background-The cytokines interleukin 1 (IL-1) and tumor necrosis factor (TNF) are secreted by the different cell populations of the vascular wall and have been suggested to promote atherosclerosis. Methods and Results-Their respective roles in fatty-streak formation in apolipoprotein E-deficient mice were investigated by use of IL-1 receptor antagonist and TNF binding protein. Estradiol-17␤ was used as a positive control. Blocking TNF seemed to be active in female animals but not in males. IL-1 receptor antagonist was as effective as or more effective than estradiol in both sexes. Conclusions-IL-1 plays a crucial role in the initial step of the atherosclerotic process in this animal model, and blocking the activity of this cytokine should be considered as a therapeutic possibility. (Circulation. 1998;97:242-244.)Key Words: atherosclerosis Ⅲ apolipoproteins Ⅲ interleukins Ⅲ tumor necrosis factor I t is known that IL-1␣ and -1␤ and TNF-␣ and -␤ are secreted in the vascular wall by endothelial and smooth muscle cells as well as by monocytes/macrophages. 1,2 These cytokines have been shown to increase permeability of the endothelial cell barrier, 3 induce the expression of surface leukocyte adhesion molecules, 1,4,5 and enhance the production of other cytokines and growth factors, such as IL-6 6 and macrophage colony-stimulating factor, 7-9 all such activities being considered to promote atherosclerosis. The objective of the present study was therefore to clarify the role of IL-1 and TNF in the initial steps of the atherosclerotic process, ie, fatty-streak formation, using apo E KO mice as an animal model of atherosclerosis 10,11 and human IL-1ra and TNFbp as the specific cytokine antagonists. IL-1ra is a recombinant 17-kD protein, which binds to IL-1 receptors and competes with both IL-1␣ and IL-1␤ without detectable IL-1 agonistic effects. 12,13 TNFbp is a specific TNF inhibitor consisting of two molecules of the extracellular domain of the human type 1 TNF receptor added to both ends of a molecule of polyethylene glycol. TNFbp binds with equal affinity to TNF-␣ and TNF-␤.14 -16 E 2 treatment was used as a positive control, because we and others have shown that this hormone prevents fatty-streak formation in the apo E KO mouse animal model. 17,18 The data obtained showed that TNFbp was active in female animals but not in males. Like E 2 , IL-1ra was active in both sexes, suggesting that IL-1 plays a crucial role in the initial step of the atherosclerotic process in this animal model. Methods Study ProtocolApo E KO mice, originally obtained from the Jackson Laboratory, Bar Harbor, Me (sixth generation of backcross from 129/B6 F1 heterozygous to C57BL/6), were housed as previously described 18 and fed normal laboratory mouse chow containing 4.3% fat and 0.02% cholesterol. Four-week-old animals were gonadectomized under general anesthesia. At 2 months of age, these animals were given 0.2 mg 60-day time-release E 2 pellets (Innovative Research of America), a dose that was found to exert a maximal effect on fatty-strea...

Interleukin-1 Receptor Signaling Mediates Atherosclerosis Associated With Bacterial Exposure and/or a High-Fat Diet in a Murine Apolipoprotein E Heterozygote Model

“…46 Other studies suggest a crucial role for IL-1 in the atherosclerotic process, even at its earliest foam cell stage. 35 On the basis of incomplete effects of IL-1 on atherosclerosis in prior studies, we planned to neutralize the effect of IL-1 as completely as possible with a knockout IL-1R1 receptor mouse model. In the present study, histopathologic analysis of the ApoE ϩ/Ϫ /IL-1R1 Ϫ/Ϫ mice exhibited reduced atherosclerotic lesions, suggesting that IL-1R knockout diminishes the hemoattractant effect on circulating monocytes.…”

“…40 The proximal aorta (ascending thoracic aorta or aortic annulus alone) was embedded together with the heart in Histo Prep (Fisher Scientific) for cryosectioning. 35,37 Liver, kidney, and spleen were collected for routine paraffin sections and hematoxylin-eosin staining.…”

“…28 Its level has been successfully lowered by blocking its transcription and synthesis with corticosteroids, nonsteroidal antiinflammatory drugs, cyclooxygenase/lipoxygenase inhibitors, transforming growth factor-␤, IL-4, IL-10, and IL-1␤ converting enzyme inhibitor. 29 -34 Short-term perfusion with an IL-1R antagonist has been shown to modify fatty-streak formation in apolipoprotein E (ApoE)-deficient mice, 35 and genetic overexpression of this antagonist promoted atherosclerosis in LDL receptor-knockout mice fed a high-fat diet (HFD); absence of this antagonist conversely promoted neointimal formation after injury. 35 Recently, genetic deletion of IL-1␤ was shown to decrease atherosclerotic severity in ApoE Ϫ/Ϫ animals, but only by Ϸ30%, perhaps because of persistent activation of the IL-1R by IL-1␣.…”

“…29 -34 Short-term perfusion with an IL-1R antagonist has been shown to modify fatty-streak formation in apolipoprotein E (ApoE)-deficient mice, 35 and genetic overexpression of this antagonist promoted atherosclerosis in LDL receptor-knockout mice fed a high-fat diet (HFD); absence of this antagonist conversely promoted neointimal formation after injury. 35 Recently, genetic deletion of IL-1␤ was shown to decrease atherosclerotic severity in ApoE Ϫ/Ϫ animals, but only by Ϸ30%, perhaps because of persistent activation of the IL-1R by IL-1␣. 37 In contrast, IL-1R2 is a nontransducing decoy receptor.…”

Effets vasculaires des œstrogènes

“…On peut alors s'attendre à ce que le blocage de certaines cytokines pro-inflammatoires et/ou l'administration de certaines cytokines anti-inflammatoires aient un effet athéroprotecteur, et inversement(‹). Cela se vérifie par exemple pour l'interféron g ou l'interleukine-1 qui accélèrent le processus athéromateux [25], tandis que l'interleukine 10 s'avère protectrice [26]. Étant donné l'importance du système immunitaire dans l'effet athéroprotecteur de l'E2, l'implication voire la régu-lation d'une ou plusieurs cytokines par l'oestradiol repré-sente donc une hypothèse qu'il nous a semblé logique de tester.…”