Abstract 12161: Toll-like Receptor 9 Plays a Pivotal Role in Angiotensin II-induced Atherosclerosis
Background: Chronic vascular inflammation causes atherosclerosis. Toll-like receptor (TLR) 9 recognizes bacterial unmethylated DNA and plays a role in innate defense, whereas it can also provoke inflammation in response to fragmented DNA released from damaged mammalian cells. However, the role of TLR9 in the development of atherosclerosis remains unknown. Here, we investigated whether genetic deletion of TLR9 attenuates atherosclerosis in apolipoprotein E knockout (ApoE KO) mice.
Methods and Results: We generated TLR9/ApoE double knockout (dKO) mice by crossing ApoE KO mice and TLR9 KO mice, and infused angiotensin II (Ang II) (1000 ng/kg/min) subcutaneously for 28 days using osmotic pump. There were no differences in blood pressure and plasma lipid levels between ApoE KO mice and TLR9/ApoE dKO mice. Ang II infusion significantly increased plasma levels of single-stranded DNA and double-stranded DNA, endogenous ligands of TLR9, in both strains of mice (P<0.001, respectively). TLR9/ApoE dKO mice showed less atherosclerotic lesion progression in the aortic arch and less lipid accumulation in atherosclerotic plaques in the aortic root compared with ApoE KO mice (P<0.05, respectively). TLR9/ApoE dKO mice also showed less gene expression of inflammatory molecules (e.g., ICAM-1, MCP-1) in the abdominal aorta. The result of cell sorting experiment using atherosclerotic aorta obtained from Ang II-infused ApoE KO mice demonstrated that macrophage population mainly expressed TLR9 in this tissue. We, therefore, performed in vitro experiments using thioglycolate-stimulated peritoneal macrophages. CpG ODN, agonistic oligonucleotide for TLR9, markedly promoted the expression of inflammatory molecules (e.g., ICAM-1 and MCP-1) in wild-type macrophages but not in TLR9 KO macrophages. Furthermore, conditioned medium (CM) of human umbilical vein endothelial cells (HUVECs) treated with Ang II promoted gene expression of ICAM-1 and TNF-α in THP-1 macrophages compared with CM of non-treated HUVECs.
Conclusion: Our results suggested that Ang II infusion activates the TLR9 signaling in macrophages, leading to the promotion of vascular inflammation and atherosclerosis. TLR9 may serve as a potential therapeutic target for atherosclerotic diseases.
Author Disclosures: S. Nishimoto: None. D. Fukuda: None. Y. Higashikuni: None. K. Tanaka: None. Y. Hirata: None. S. Yagi: None. T. Soeki: None. H. Sakaue: None. M. Shimabukuro: None. M. Sata: None.
- © 2015 by American Heart Association, Inc.