Key Points Fn-EDA+ promotes arterial thrombosis. Platelet TLR4 mediates the prothrombotic effect of cellular Fn.

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Background The fibronectin splicing variant containing extra domain A (Fn-EDA) is present in negligible amounts in the plasma of healthy humans, but markedly elevated in patients with comorbid conditions including diabetes and hypercholesterolemia, which are risk factors for stroke. It remains unknown, however, whether Fn-EDA worsens stroke outcomes in such conditions. We determined the role of Fn-EDA in stroke outcome in a model of hypercholesterolemia, the apolipoprotein E-deficient (Apoe−/−) mouse. Methods and Results In a transient cerebral ischemia/reperfusion injury model, Apoe−/− mice expressing Fn deficient in EDA (Fn-EDA−/−Apoe−/− mice) exhibited smaller infarcts and improved neurological outcomes at days 1 and 8 (P<0.05 vs. Apoe−/− mice). Concomitantly, intracerebral thrombosis (assessed by fibrin (ogen) deposition) and postischemic inflammation (phospho-NF-κB p65, phospho IKKα/β, IL1-β and TNFα) within lesions of Fn-EDA−/−Apoe−/− mice were markedly decreased (P<0.05 vs. Apoe−/− mice). In a FeCl3 injury-induced carotid artery thrombosis model, thrombus growth rate and the time to occlusion were prolonged in Fn-EDA−/−Apoe−/− mice (P<0.05 vs. Apoe−/− mice). Genetic ablation of TLR4 improved stroke outcome in Apoe−/− mice (P<0.05) but had no effect on stroke outcome in Fn-EDA−/−Apoe−/− mice. Bone marrow transplantation experiments revealed that non-hematopoietic cell-derived Fn-EDA exacerbates stroke through TLR4 expressed on hematopoietic cells. Infusion of a specific inhibitor of Fn-EDA into Apoe−/− mouse 15 minutes after reperfusion significantly improved stroke outcome. Conclusions Hypercholesterolemic mice deficient in Fn-EDA exhibit reduced cerebral thrombosis and less inflammatory response after ischemia/reperfusion injury. These findings suggest that targeting Fn-EDA could be an effective therapeutic strategy in stroke associated with hypercholesterolemia.

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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 gender, 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 vs. 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, TNFα and IL1β) 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.

Objective Von Willebrand factor (VWF), which is synthesized in endothelial cells and megakaryocytes, is known to worsen stroke outcome. In vitro studies suggest that platelet-derived VWF is biochemically different from the endothelial cell-derived VWF. However, little is known about relative contribution of different pools of VWF in stroke. Approach and Results Using bone marrow transplantation, we generated chimeric platelet derived-VWF mice (Plt-VWF), platelet derived-VWF mice that lack ADAMTS13 in platelets and plasma (Plt-VWF/Adamts13−/−), and endothelial cell derived-VWF mice (EC-VWF) to determine relative contribution of different pools of VWF in stroke. In brain ischemia/reperfusion injury model, we found that infarct size, post-ischemic intracerebral thrombo-inflammation (fibrin(ogen) deposition, neutrophil infiltration, IL-1β and TNF-α levels) within lesions were comparable between EC-VWF and WT mice. Infarct size and post-ischemic thrombo-inflammation were comparable between Plt-VWF and Plt-VWF/Adamts13−/− mice, but decreased compared to EC-VWF and/or WT mice (P<0.05) and increased compared to Vwf −/− mice (P<0.05). Susceptibility to FeCl3 injury-induced carotid artery thrombosis was comparable between WT and EC-VWF mice, whereas Plt-VWF and Plt-VWF/Adamts13−/− mice exhibited defective thrombosis. Although most of the injured vessels did not occlude, slope over time showed that thrombus growth rate was increased in both Plt-VWF and Plt-VWF/Adamts13−/− mice compared to Vwf −/− mice (P<0.05), but decreased compared to WT or EC-VWF mice. Conclusions Platelet-derived VWF, either in presence or absence of ADAMTS13, partially contributes to VWF-dependent injury and post-ischemic thrombo-inflammation following stroke. Endothelial cell-derived VWF is the major determinant that mediates VWF-dependent ischemic stroke by promoting post-ischemic thrombo-inflammation.

Intercellular adhesion molecules (ICAMs) belong to the immunoglobulin superfamily and participate in diverse cellular processes including host-pathogen interactions. ICAM-1 is expressed on various cell types including macrophages, whereas ICAM-4 is restricted to red blood cells. Here we report the identification of an 11-kDa synthetic protein, M5, that binds to human ICAM-1 and ICAM-4, as shown by in vitro interaction studies, surface plasmon resonance and immunolocalization. M5 greatly inhibits the invasion of macrophages and erythrocytes by Mycobacterium tuberculosis and Plasmodium falciparum, respectively. Pharmacological and siRNA-mediated inhibition of ICAM-1 expression also results in reduced M. tuberculosis invasion of macrophages. ICAM-4 binds to P. falciparum merozoites, and the addition of recombinant ICAM-4 to parasite cultures blocks invasion of erythrocytes by newly released merozoites. Our results indicate that ICAM-1 and ICAM-4 play roles in host cell invasion by M. tuberculosis and P. falciparum, respectively, either as receptors or as crucial accessory molecules.

Essential oil components from turmeric (Curcuma longa L.) are documented for neuroprotective, anti-cancer, anti-thrombotic and antioxidant effects. The present study aimed to investigate the disease-modifying potential of curcuma oil (C. oil), a lipophilic component from C. longa L., in hyperlipidaemic hamsters. Male golden Syrian hamsters were fed a chow or high-cholesterol (HC) and fat-rich diet with or without C. oil (30, 100 and 300 mg/kg) for 28 d. In HC diet-fed hamsters, C. oil significantly reduced plasma total cholesterol, LDL-cholesterol and TAG, and increased HDL-cholesterol when compared with the HC group. Similar group comparisons showed that C. oil treatment reduced hepatic cholesterol and oxidative stress, and improved liver function. Hyperlipidaemia-induced platelet activation, vascular dysfunction and repressed eNOS mRNA expression were restored by the C. oil treatment. Furthermore, aortic cholesterol accumulation and CD68 expression were also reduced in the C. oil-treated group. The effect of C. oil at 300 mg/kg was comparable with the standard drug ezetimibe. Delving into the probable anti-hyperlipidaemic mechanism at the transcript level, the C. oil-treated groups fed the chow and HC diets were compared with the chow diet-fed group. The C. oil treatment significantly increased the hepatic expression of PPARa, LXRa, CYP7A1, ABCA1, ABCG5, ABCG8 and LPL accompanied by reduced SREBP-2 and HMGCR expression. C. oil also enhanced ABCA1, ABCG5 and ABCG8 expression and suppressed NPC1L1 expression in the jejunum. In the present study, C. oil demonstrated an anti-hyperlipidaemic effect and reduced lipid-induced oxidative stress, platelet activation and vascular dysfunction. The anti-hyperlipidaemic effect exhibited by C. oil seems to be mediated by the modulation of PPARa, LXRa and associated genes involved in lipid metabolism and transport.