Deletion of Extra Domain A of Fibronectin Reduces Acute Myocardial Ischaemia/Reperfusion Injury in Hyperlipidaemic Mice by Limiting Thrombo-Inflammation

• DOI: 10.1055/s-0038-1661353
• Publication Date: 2018-06-30T23:00:41Z
• Authors: Mehul Chorawala; Prem Prakash; Prakash Doddapattar; Manish Jain; Nirav Dhanesha; Anil Chauhan
• Keywords: Inflammation; Male; Mice, Knockout, ApoE; Neutrophils; Myocardium; Myocardial Infarction; Apoptosis; Hyperlipidemias; Myocardial Reperfusion Injury; Thrombosis; Extracellular Traps; Fibronectins; 3. Good health; Mice, Inbred C57BL; Toll-Like Receptor 4; Disease Models, Animal; 03 medical and health sciences; 0302 clinical medicine; Neutrophil Infiltration; Animals; Female; Gene Deletion; Signal Transduction

Background Fibronectin splicing variant containing extra domain A (Fn-EDA), which is an endogenous ligand for Toll-like receptor 4 (TLR4), is present in negligible amounts in the plasma of healthy humans, but markedly elevated in patients with co-morbid conditions including diabetes and hyperlipidaemia, which are risk factors for myocardial infarction (MI). Very little is known about the role of Fn-EDA in the pathophysiology of acute MI under these co-morbid conditions. Materials and Methods We determined the role of Fn-EDA in myocardial ischaemia/reperfusion (I/R) injury in the hyperlipidaemic apolipoprotein E-deficient (ApoE−/−) mice. Infarct size, plasma cardiac troponin I (cTnI) levels, intravascular thrombosis (CD41-positive), neutrophil infiltration (Ly6 B.2-positive), neutrophil extracellular traps (citrullinated H3-positive) and myocyte apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling-positive) were assessed in myocardial I/R injury model (1-hour ischaemia/23 hours of reperfusion). Results Irrespective of gender, Fn-EDA−/−ApoE−/− mice exhibited smaller infarct size and decreased cTnI levels concomitant with reduced post-ischaemic intra-vascular thrombi, neutrophils influx, neutrophil extracellular traps and myocyte apoptosis (p < 0.05 vs. ApoE−/− mice). Genetic deletion of TLR4 attenuated myocardial I/R injury in ApoE−/− mice (p < 0.05 vs. ApoE−/− mice), but did not further reduce in Fn-EDA−/− ApoE−/− mice suggesting that Fn-EDA requires TLR4 to mediate myocardial I/R injury. Bone marrow transplantation experiments revealed that Fn-EDA exacerbates myocardial I/R injury through TLR4 expressed on the haematopoietic cells. Infusion of a specific inhibitor of Fn-EDA, 15 minutes post-reperfusion, into ApoE−/− mice attenuated myocardial I/R injury. Conclusion Fn-EDA exacerbates TLR4-dependent myocardial I/R injury by promoting post-ischaemic thrombo-inflammatory response. Targeting Fn-EDA may reduce cardiac damage following coronary artery re-canalization after acute MI.