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), EDA fl/fl Apoe −/− mice (which constitutively express EDA + -FN), and control Apoe −/− mice fed a high-fat Western diet for 14 weeks. Irrespective of sex, EDA fl/fl Apoe −/− 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 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 EDA fl/fl Apoe −/− mice ( P 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.