Fibronectin Splicing Variants Containing Extra Domain A Promote Atherosclerosis in Mice Through Toll-Like Receptor 4
Objective—Cellular fibronectin containing extra domain A (EDA+-FN) is abundant in the arteries of patients with atherosclerosis. Several in vitro studies suggest that EDA+-FN interacts with Toll-like receptor 4 (TLR4). We tested the hypothesis that EDA+-FN exacerbates atherosclerosis through TLR4 in a clinically relevant model of atherosclerosis, the apolipoprotein E–deficient (Apoe−/−) mouse.
Approach and Results—The extent of atherosclerosis was evaluated in whole aortae and cross sections of the aortic sinus in male and female EDA−/−Apoe−/− mice (which lack EDA+-FN), EDAfl/flApoe−/− mice (which constitutively express EDA+-FN), and control Apoe−/− mice fed a high-fat Western diet for 14 weeks. Irrespective of sex, EDAfl/flApoe−/− mice exhibited a 2-fold increase in atherosclerotic lesions (aorta and aortic sinus) and macrophage content within plaques, whereas EDA−/−Apoe−/− mice exhibited reduced atherosclerotic lesions (P<0.05 versus Apoe−/−, n=10–12 mice/group), although cholesterol and triglyceride levels and circulating leukocytes were similar. Genetic ablation of TLR4 partially reversed atherosclerosis exacerbation in EDAfl/flApoe−/− mice (P<0.05) but had no effect on atherosclerotic lesions in EDA−/−Apoe−/− mice. Purified cellular FN, which contains EDA, potentiated dose-dependent NFκB-mediated inflammation (increased phospho-NFκB p65/NFκB p65, tumor necrosis factor-α, and interleukin-1β) in bone marrow–derived macrophages from EDA−/−Apoe−/− mice but not from EDA−/−TLR4−/−Apoe−/− mice. Finally, using immunohistochemistry, we provide evidence for the first time that EDA+-FN colocalizes with macrophage TLR4 in murine aortic lesions and human coronary artery atherosclerotic plaques.
Conclusions—Our findings reveal that TLR4 signaling contributes to EDA+-FN–mediated exacerbation of atherosclerosis. We suggest that EDA+-FN could be a therapeutic target in atherosclerosis.
- Received June 23, 2014.
- Accepted September 14, 2015.
- © 2015 The Authors.
Arteriosclerosis, Thrombosis, and Vascular Biology is published on behalf of the American Heart Association, Inc., by Wolters Kluwer. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial-NoDervis License, which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited, the use is noncommercial, and no modifications or adaptations are made.